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Chris Miller
Experienced User
Username: cjm51213

Post Number: 35
Registered: 5-2013
Posted on Tuesday, 13 May, 2014 - 03:02 am:   Edit PostDelete PostView Post/Check IP

Hi Folks, I've removed and disassembled my two accumulators and I'm thinking about the assembly process. The manual says to charge with 1,000 PSI Nitrogen. Is there any reason I couldn't/shouldn't use Argon?

Why is this even a question? There are competing considerations:
1) Argon is a noble gas and nonreactive. Nitrogen has non-zero reactivity, although
Nitrogen doesn't seem to hurt the diaphragm.
2) The Argon atom is bigger than the Nitrogen atom, but the Nitrogen molecule (N2)
is bigger that the Argon molecule (Ar), so impounding success may differ
3) The cost will differ, but probably not by much, given the relatively small
quantity an accumulator needs, but I don't know if this is really a
significant consideration.
4) I already have Argon.

Chris.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 388
Registered: 5-2012
Posted on Tuesday, 13 May, 2014 - 03:57 am:   Edit PostDelete PostView Post/Check IP

Hi Chris

I'd research the thermal coefficients of the two gases before going ahead. I believe (but may be wrong) that argon will cause much greater pressure increases over nitrogen as the gases are heated. The accumulators, being situated close to the engine will of course get much hotter as the engine is run. I am no expert on this, but would go ahead with caution.

Geoff
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Chris Miller
Experienced User
Username: cjm51213

Post Number: 36
Registered: 5-2013
Posted on Tuesday, 13 May, 2014 - 04:54 am:   Edit PostDelete PostView Post/Check IP

Hi Geoff,

That is an excellent point and one I had not considered, so it bears investigation...

The ideal gas law is "PV=nRT". Specifically, at room temperature, "PV" and "T" for Argon will be the same as Nitrogen, since these values are determined when I initially pressurize the accumulator at 1,000 PSI. "n" may vary, but "nR" can not. If "T" doubles, then "P" doubles, irrespective of the gas -- Nitrogen or Argon.

I have no reason to believe that I have not made any mistakes, so if you have an inkling, please review this reasoning to be sure I have not made any mis-steps in the reasoning.

Finally, the "Charging Valve" is responsible for keeping the pressure constant, so expansion characteristics of the gas would appear in duty cycle variations of the accumulator, rather than pressure variations, I think. Check me on this. I've been wrong before and I will probably be wrong again.

Thanks for the help,

Chris.
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Bob uk
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Posted From: 94.197.122.93
Posted on Tuesday, 13 May, 2014 - 05:57 am:   Edit PostDelete PostView Post/Check IP

Argon is not suitable nitrogen is best
I know more than one accumulator that has lasted 20 years with full charge nitrogen
I am a retired vehicle inspector and if I found a brake accumulator had argon I would prohibit the vehicle unti-l the owner could prove that argon ok

(Message approved by david_gore)
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Chris Miller
Experienced User
Username: cjm51213

Post Number: 37
Registered: 5-2013
Posted on Tuesday, 13 May, 2014 - 07:05 am:   Edit PostDelete PostView Post/Check IP

O.K., so that's one vote, "No." (-:

Bob, haven't I already proved Argon is a viable candidate? The only important characteristics of the gas are reactivity with the components of the accumulator and difficulty impounding. Reactivity of Argon should be zero. It is an open question about leakage; the argon molecule (Ar) is smaller than the Nitrogen (N2) molecule. Aside from these two considerations, I think they are indistinguishable, but I have been wrong before and this is way I am asking the question.

Chris.
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John Grieve
Experienced User
Username: john116

Post Number: 30
Registered: 4-2012
Posted on Tuesday, 13 May, 2014 - 07:06 am:   Edit PostDelete PostView Post/Check IP

How as a vehicle inspector would you ever know the accumulator had argon as opposed to nitrogen? Certainly not from a normal inspection, so that point would appear to be moot.
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Bob Reynolds
Frequent User
Username: bobreynolds

Post Number: 83
Registered: 8-2012
Posted on Tuesday, 13 May, 2014 - 10:24 am:   Edit PostDelete PostView Post/Check IP

I guess there's only one way to solve this, and that is to try it out. I doubt that anyone else has ever tried it and can give a definitive answer.

I have heard of plain compressed air being used, and it can't be any worse than that.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 389
Registered: 5-2012
Posted on Tuesday, 13 May, 2014 - 11:46 am:   Edit PostDelete PostView Post/Check IP

Hi Chris

The ideal gas law is "PV=nRT"

That took me back to school physics, a long long time ago. I found it quite interesting so did some checking out and have to agree that Argon should be ok. At the temperatures and pressures we are talking about the ideal gas law should apply - nitrogen and argon will behave similarly. The only problem I can think of is the one you alluded to, which is permeation of the membrane due to Ar being monatomic. I doubt this will cause any significant problems in terms of pressure loss over the years. So my vote is yes, try it. Also, there will be no problems with the MOT test as we don't have one here, in the US

Geoff
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Bob uk
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Posted From: 94.197.122.85
Posted on Wednesday, 14 May, 2014 - 07:13 am:   Edit PostDelete PostView Post/Check IP

Don't fix what isn't broke
To say that argon is ok on the basis of 5 minutes research is not good enough an insurer would question it

(Message approved by david_gore)
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David Gore
Moderator
Username: david_gore

Post Number: 1381
Registered: 4-2003
Posted on Wednesday, 14 May, 2014 - 08:47 pm:   Edit PostDelete PostView Post/Check IP

The following information on Argon compatibility with elastomers commonly used in O-rings may be of interest:

http://www.efunda.com/glossary/design/oring/design--oring--chemical--argon.cfm
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Chris Miller
Experienced User
Username: cjm51213

Post Number: 41
Registered: 5-2013
Posted on Wednesday, 14 May, 2014 - 10:33 pm:   Edit PostDelete PostView Post/Check IP

Hi David,

Excellent research. This introduces another consideration I had missed -- partial pressure. If any of these materials out-gas Nitrogen, then the Argon environment would have a zero partial pressure of Nitrogen and allow for the material to degrade by "evaporation" so to speak.

I don't know the materials used in the various seals; I can't find any documentation describing that level of detail. This has come up before in my experience. There is the whole RR363 composition question, which is ultimately a "seal preservation" issue.

Thanks very much for the help; it has been beneficial and has decided the issue for me -- Nitrogen. Why chance it?

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 788
Registered: 6-2009
Posted on Thursday, 15 May, 2014 - 02:29 am:   Edit PostDelete PostView Post/Check IP

The standard seals in RR363 systems are EPDM.

I cannot even imagine that the diaphragm is not also EPDM.

All should be fine with argon, nitrogen, and even "treated air."

The only issue I could anticipate as a possible, but not probable, problem based on the information presented so far in this thread is that argon might be able to pass through the diaphragm a tiny bit more easily than nitrogen.

Chris, how, may I ask, did you come by a supply of argon of all things?

Brian
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Chris Miller
Experienced User
Username: cjm51213

Post Number: 43
Registered: 5-2013
Posted on Thursday, 15 May, 2014 - 02:40 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

Argon is a standard gas for shielding wire-feed welding. It's actually pretty easy to come by, but I don't remember the relative price of Argon and Nitrogen. I suspect there will be a difference. Maybe Nitrogen will be cheaper with all the "run-flat" tires around these days...

Straight air is 80% nitrogen, to one significant figure, but it is that tricky 20% oxygen that might cause the trouble and the only reason I am not simply going with compressed air, which is *really* easy to come by. (-: After all, the "run-flat" guys think it is worth excluding the oxygen, and refilling/changing a tire is *easy*.

Chris.
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Richard Treacy
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Username: richard_treacy

Post Number: 3016
Registered: 4-2003
Posted on Thursday, 15 May, 2014 - 02:16 pm:   Edit PostDelete PostView Post/Check IP

It certainly puzzles me how anyone would be brave enough to meddle with the tried and proven braking systems of these cars. If something went wrong the authorities would have a field day. Nitrogen-charged gas spheres have been used in a multitude of applications for decades, and not just by CitroŽn and Crewe. Next someone could suggest replacing the gas by a steel spring or a rubber ball.

RT.
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Bob Reynolds
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Username: bobreynolds

Post Number: 84
Registered: 8-2012
Posted on Thursday, 15 May, 2014 - 02:52 pm:   Edit PostDelete PostView Post/Check IP

Hmmm - what an excellent idea.

Thanks for the suggestions.
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Chris Miller
Experienced User
Username: cjm51213

Post Number: 47
Registered: 5-2013
Posted on Friday, 16 May, 2014 - 12:08 am:   Edit PostDelete PostView Post/Check IP

Hi Richard,

> It certainly puzzles me how anyone would be brave enough to meddle...
Well, since you asked... Undertaking a discussion is not "meddling", and sometime such discussions lead to improvements.

> Nitrogen-charged gas spheres have been used in a multitude of applications for decades...
Yes, but why Nitrogen? Because it is best or because it is easiest to get? Argon is now readily available, and may be better. I now believe that it is not because of physical chemistry considerations, not mechanical considerations -- partial pressures exerted by the constituents of the seals and the open question of the size of the molecule leading to potential permeation of the diaphragm, but these are physical/chemical considerations. Mechanically, Argon is just as good as Nitrogen.

> Next someone could suggest replacing the gas by a steel spring or a rubber ball.
Yes. And is some applications they have, steel springs are used everywhere, but the beauty of a gas is that it doesn't fatigue and break like mechanical components, and the mass is relatively small, so inertial response is very much better.

Chris.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 393
Registered: 5-2012
Posted on Friday, 16 May, 2014 - 04:00 am:   Edit PostDelete PostView Post/Check IP

I fully understand Chris's desire to use argon instead of nitrogen. If I had a cylinder of argon in my garage I would also consider the same. The show-stopper for me is the insurance implications of modifying the brake/hydraulic system. However, you could in principle use the same argument against using a dot3/castor oil mix instead of RR363.

My question to Chris would be is it possible to fit your argon regulators to a nitrogen bottle? Nitrogen cylinders are cheap to rent/buy however the regulators are very expensive. I know you should never use regulators across different gas bottles however argon/nitrogen is not an explosive or corrosive mix.

Geoff
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 798
Registered: 6-2009
Posted on Friday, 16 May, 2014 - 05:06 am:   Edit PostDelete PostView Post/Check IP

Geoff,

Just for the record, a safe and inexpensive nitrogen charging system for the hobbyist can be easily put together.

See this document on how to assemble same. The key is having the regulator in this setup be a 1000 PSI regulator. I actually now have this kit since the person who put it together has retired from working on his own cars and was kind enough to give it to me when he knew I needed it.

Brian
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 395
Registered: 5-2012
Posted on Friday, 16 May, 2014 - 08:22 am:   Edit PostDelete PostView Post/Check IP

Hi Brian

Many thanks. This will be the method I use when I eventually need to re-charge my accumulators, hopefully not for quite a while yet. The reason I mentioned a nitrogen bottle to Chris is that he already has the regulators. I was curious if they could be swapped across from argon to nitrogen bottles. It would be a good option for owners with argon arc welders.

Geoff
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 53
Registered: 5-2013
Posted on Friday, 16 May, 2014 - 09:23 am:   Edit PostDelete PostView Post/Check IP

Geeze...

I am despondent. Last summer I ran around and collected all the necessary pieces to do this -- develop Hydraulic Accumulator charging proficiency. I stashed it in one of my "Project Boxes" where I keep all the necessary pieces of pending and on-going projects together until I can advance that project, SO THEY DON'T GET LOST! I'm pretty organized. That project box is gone and I have looked everywhere, so I have to conclude that it was stolen. I'm angry and mystified in turns and I have wasted pretty much the whole day searching and re-searching and re-re-searching my shop, still in a state of shock that it is gone. However, ...

The canister was a standard 48 cu.in. 3,000 PSI *compressed air* paint ball canister; Carbon Dioxide canisters are *not* acceptable, first because nobody will put anything in them but Carbon Dioxide, and second, the vapor pressure of Carbon Dioxide is very much lower than either Nitrogen or Argon, which I think means that they don't have to be designed to the same strength limits. At room temperature, Carbon Dioxide can be compressed into a liquid. Regardless, Carbon Dioxide is a distraction and we don't need to spend any more time on it.

Compressed Air canisters come with a stock regulator that develops 800 PSI, which is not quite enough to meet the Hydraulic Accumulator charging specification. 800 PSI will work but, reduces the volume of fluid available "at working pressure". The gas volume of the sphere in use when the gas is initially charged to 1,000 PSI is 40% (1,000 PSI / 2,500 PSI) , but when initially charged to 800 PSI, it drops to less than 25% (800 PSI / 2,500 PSI). It drops pressure more quickly as fluid is deployed to various applications. Rolls Royce says 1,000 PSI and I suspect it is the best balance of pressure response and duty cycle.

In order to get 1,000 PSI, I bought a special "high-pressure" regulator for the canister, which is also "paint-ball" equipment, that can produce 1,100 PSI. This will equilibrate at a lower fluid volume and therefore a shorter duty cycle, but is probably operationally acceptable, and preferable to 800 PSI, given the choice. There will be slightly less fluid in the accumulator, but more available "at working pressure".

These 1,100 PSI regulators are not terribly expensive in this application domain, "paintball", but "Standard" industrial gas regulators that source this pressure cost many hundreds of dollars, if you can find them, and I could never get an answer if they will even fit on the 48 cu.in. canisters, but I think the consensus is that "compressed air" is "compressed air" regardless of the size of the canister, so they will. But let's not go there. The "paint-ball" equipment is perfectly adequate and *much* less expensive.

My MIG welder regulators don't source that kind of pressure, so can't be used. It is shielding gas and delivered at quite a low pressure to envelop the weld in a cloud of non-reactive gas stifling any oxidation that would otherwise ruin the weld.

Is this at all useful to anybody? I have already been down this path, but I must re-create this capacity (uuugh! I'm dumbfounded at this development...), so if anybody is interested, I will happily list the parts I collect and the source. Collecting the canister, the regulator, the hose and the fittings to the Accumulator is dead simple. The hard part is getting someone to fill the canister with nitrogen and I remember that I had to do something special for that. I don't remember the details, but stay tuned and I'll report what I (re)learn. I should have reported last summer, so I'd know now, but I didn't and here I am -- re-inventing.

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 799
Registered: 6-2009
Posted on Friday, 16 May, 2014 - 09:43 am:   Edit PostDelete PostView Post/Check IP

Chris,

If your local welding supply can't/won't charge your paintball tank make some inquiries at your local airport or airplane service facility. They use nitrogen for accumulators on planes on a constant basis and can often either fill your tank or tell you who will.

Brian
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 396
Registered: 5-2012
Posted on Friday, 16 May, 2014 - 12:12 pm:   Edit PostDelete PostView Post/Check IP

Chris

Since you have the accumulators off the car why don't you get them re-charged at a local factors. It will save you having to sort out your own charging station. When I was looking for a recharge I did google searches on local businesses and checked out craigslist etc. I found three sources and chose a local transmission specialist who charged me 10 bucks for each accumulator. If you look locally I am sure you will find somewhere. My main reason for going the paintball route for future charges is so that I can charge them in-situ. If the accumulators are off the car, as in your case, it will be much quicker to get them charged by a local shop.

Geoff
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Jim Walters
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Username: jim_walters

Post Number: 14
Registered: 1-2014
Posted on Friday, 16 May, 2014 - 02:52 pm:   Edit PostDelete PostView Post/Check IP

You don't absolutely need a second regulator, and I wouldn't trust a preset one without a gauge to confirm the pressure. I made my Nitrogen charging rig using a high pressure hose from the high pressure port on the gas regulator on the tank to a T fitting with a 3000 psi gauge attached. This first fitting also has a bleed off valve at the bottom. This fitting is attached to a high pressure valve, I used an old valve off of a Scuba tank, good for at least 3000 psi. Then another T fitting with a second gauge that will read the gas pressure in the accumulator, and out of that is the filling valve. The filling valve has a pin in it that will depress the ball bearing in the accumulator by turning the T handle shown on top of it. This is the only way to actually test the pressure in a sphere that is not connected to an accumulator valve. When charging a sphere, one carefully, slowly just cracks the scuba valve until Nitrogen starts to fill the sphere and the pressure registers on the second gauge. Obviously great care must be used with my system to avoid over-pressurizing the sphere. One should have a second regulator set at 1000psi for safety but I am the only one who uses my rig and I have used it safely without incident for years.

Nitrogen charging rig

SRE22493 NAC-05370
www.bristolmotors.com
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 397
Registered: 5-2012
Posted on Friday, 16 May, 2014 - 11:06 pm:   Edit PostDelete PostView Post/Check IP

Hi Jim

Nice set up. Do you ever re-charge accumulators in situ on the SY1s, or do you always remove the accumulators.

Geoff
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Jim Walters
Experienced User
Username: jim_walters

Post Number: 15
Registered: 1-2014
Posted on Saturday, 17 May, 2014 - 03:57 am:   Edit PostDelete PostView Post/Check IP

Hi Geoff, I've always removed them and rebuilt them before charging. As I am in the business, I need to be able to stand behind my work and provide a guarantee. Without installing a new diaphragm in the sphere I have no idea of the condition of it or the life left in it. It may charge up fine on the car, but then fail completely a week later, jeopardizing not only my reputation with my client but perhaps someone's life. To me it is not worth taking the risk. Jim.

SRE22493 NAC-05370
www.bristolmotors.com
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Chris Miller
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Username: cjm51213

Post Number: 54
Registered: 5-2013
Posted on Saturday, 17 May, 2014 - 06:47 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I started to think about optimal values for the initial pressure.

I considered, "What would happen if I started with 100 PSI?" The ACV (Accumulator Control Valve) would ramp up the fluid until the sphere was 2,500 PSI, but there would only be a small volume of fluid available until the pressure decreased below the operational pressure.

Then I considered, "What would happen if I started with 2,400 PSI?" The ACV (Accumulator Control Valve) would ramp up the fluid until the sphere was 2,500 PSI, but there would only be a small volume of fluid available period, although 100% would be above operational pressure.

At this point it was clear that the optimum value was somewhere between 100 PSI and 2400 PSI. Although, to be honest, I was pretty sure of that before I did this. (-:

This is when I realized that an important value I didn't have was the operational pressure. It is not immediately obvious, but any initial pressure above or below this operational pressure will cost available fluid either because the surplus fluid is not at sufficient pressure, or there is a deficiency of fluid volume.

I have concluded that the spheres are initially charged at 1,000 PSI because that is the operational pressure and any deviation from that value results in either fluid pressure deficiency or fluid volume deficiency.

I plotted a chart with my two ridiculous values of 100 PSI and 2400 PSI, and the more moderate values of 800 PSI and 1,100 PSI that I can get with paint-ball equipment, and finally 1,000 PSI. I also declared the operational pressure to be 1,000 PSI, because that is the recommended initial pressure. It was not immediately obvious to me until I did this that if the operational pressure of the brakes and levelling system is 1,000 PSI, then *only* an initial charge of 1,000 PSI would provide the greatest volume of fluid at operational pressure; any other initial charge will result in decreased available fluid either from reduced volume or reduced pressure.





Notice that my two ridiculous values result in about 1 cubic inch of fluid (to one significant figure). The difference between 1,000 PSI and 1,100 PSI is about 1.5 cubic inches, while the difference between 1,000 PSI and 800 PSI is about 4 cubic inches, answering the question I posed last summer. Given the choice between 800 PSI and 1,100 PSI, which is the preferable mistake? The answer, as many said, is, "1,100 PSI.".

I hope I haven't bored anybody with this, but I put it here so I will know where to find it the next time I need it. (-: I'm off to reconstitute my nitrogen charging capability with paint-ball equipment.

Chris.
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Paul Yorke
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Username: paul_yorke

Post Number: 1195
Registered: 6-2006
Posted on Saturday, 17 May, 2014 - 07:35 am:   Edit PostDelete PostView Post/Check IP

Sometimes it is better to just ignore the voices.

If you can't, it's always better to keep them to yourself.

:-)
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 55
Registered: 5-2013
Posted on Saturday, 17 May, 2014 - 09:30 am:   Edit PostDelete PostView Post/Check IP

Hi Paul,

Are you poking fun at me or do you really think this was off-topic or not of general interest? I thought it was a pretty cool conclusion, but I may not be mainstream.

Chris.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 398
Registered: 5-2012
Posted on Saturday, 17 May, 2014 - 09:41 am:   Edit PostDelete PostView Post/Check IP

Hi Chris

I liked your post. A lot of paint ball gauges are either set or only go up to 800 psi so it is useful to hear your view. It confirms my opinion to absolutely avoid under-charging an accumulator and always seek out a charging station that will deliver at least 1000 psi.

Geoff
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1196
Registered: 6-2006
Posted on Saturday, 17 May, 2014 - 04:47 pm:   Edit PostDelete PostView Post/Check IP

Hi Chris,

I was, and apologise for not heeding my own advice! :-)

The optimal pressure for the system is up around 2200.

Accumulator gas pressure and volume has no bearing on this whilst the engine is running. The pumps will supply enough fluid to pressurise everything with about 10 strokes, although it will need more if the rear suspension is 'on the floor'.

The accumulator is designed as a safety back up if the engine stops whilst moving. Optimal pressure is not it's goal , just keeping the grill looking pretty. :-)

Air, especially wet expands too much.

Shadow Accumulators have exploded in the past. I don't know what caused the explosions though. It may be bad workmanship or the wrong gas.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 801
Registered: 6-2009
Posted on Sunday, 18 May, 2014 - 01:35 am:   Edit PostDelete PostView Post/Check IP

Paul,

Do you have any "hard reports" on exploding accumulators? Not that I'd wish this on anyone, and I also don't think it's impossible if a wildly wrong gas (say pure oxygen or an actually explosive gas) were used, but I have yet to see documentary evidence of "an event."

It's interesting to me how many precautions the workshop manual instructs you to take during the charging process as far as building barriers around the accumulator in case it should blow apart. In practice I know of almost no one, hobbyist or professional, who does this now or has done it as standard practice in the past. If these things are screwed together correctly it would take a lot more than 1000 PSI to get them to blow and if they're so loose that they couldn't hold that pressure they'd probably leak prodigiously when attempting the charge.

Brian, who had considered "processed-dried air" (which is what our local paintball shop now dispenses) until I found a local nitrogen source at our local airport

P.S.: You used an emoticon - that's about as obvious as you can get!
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Chris Miller
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Username: cjm51213

Post Number: 57
Registered: 5-2013
Posted on Sunday, 18 May, 2014 - 01:36 am:   Edit PostDelete PostView Post/Check IP

Hi Paul,

The little voice in my head is telling me, "In the name of fun, it's all good."

Thanks for the help,

Chris.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 400
Registered: 5-2012
Posted on Sunday, 18 May, 2014 - 05:58 am:   Edit PostDelete PostView Post/Check IP

Hi Paul,

I'm also interested if you have any reports on exploding accumulators or whether you have ever seen the results of such an event in your work. I did check a citroen forum where two owners reported such things, but in both cases they appeared to be explosive decompressions through the valve rather than an explosion in which shrapnel was thrown all over the place. This is obviously an area of interest for anyone charging these accumulators. I cannot imagine that 1000 psi would be enough to blow an accumulator apart unless there was obvious damage/cracking to it.

Geoff
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Jim Walters
Experienced User
Username: jim_walters

Post Number: 16
Registered: 1-2014
Posted on Sunday, 18 May, 2014 - 08:16 am:   Edit PostDelete PostView Post/Check IP

Some may be missing the fact that the spheres are regularly "pressure tested" to 2500 psi whenever they are on a car with a working brake pump and accumulator valve. I've never had any worries putting 1000 psi of nitrogen into one knowing this fact. In 40 years of working on these cars I've never had an issue, nor have I heard first hand from anyone who has. I suspect most who have had an issue were pressurizing spheres with old diaphragms in them or tore the new diaphragm on installation. A sudden escape of pressure without rupture of the sphere itself would not be an explosion in the traditional sense. I doubt very much they would explode as a grenade would, unless subjected to pressures in excess of the normal working pressure by at least a factor of 1.5. At least I would hope not Proper workshop safety, cleanliness, skill etc. to be observed obviously.

SRE22493 NAC-05370
www.bristolmotors.com
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Bob uk
Unregistered guest
Posted From: 94.197.122.82
Posted on Sunday, 18 May, 2014 - 07:04 am:   Edit PostDelete PostView Post/Check IP

This thread worries me

1000psi of any gas is king dangerous nitrogen is not inert at a 1000 psi and will blast dust and debris and worse should your person be in the way call ambulance

My main concern is the fittings used

The bloke in the store said they should be ok

As stated to get them charge costs not very much

I know it is nice to think I can do

But he who runs away has all his fingers

(Message approved by david_gore)
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David Gore
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Username: david_gore

Post Number: 1382
Registered: 4-2003
Posted on Sunday, 18 May, 2014 - 08:40 am:   Edit PostDelete PostView Post/Check IP

From past knowledge of high pressure hydraulic accumulators used in mining equipment, the service technicians always recharged them inside a safety cage from past experience with infrequent separation of the accumulator housings after diaphragm replacement due to cross-threading during reassembly, damaged/corroded threads or, very rarely, problems with the pressure gauge not reading correctly or the shut-off valve not shutting off completely. In most cases, the sound of gas escaping alerts the technician that there is a problem allowing the recharging to be aborted before catastrophic failure however sudden explosive separation can occur without prior warning.
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Jan Forrest
Grand Master
Username: got_one

Post Number: 542
Registered: 1-2008
Posted on Sunday, 18 May, 2014 - 07:57 pm:   Edit PostDelete PostView Post/Check IP

If you don't want to go down the argon or breathing air routes many welding gas suppliers can also supply cylinders of pure nitrogen as a straight purchase with no rental. There is a small (or not so small) deposit on the cylinder which is returnable with a reduction based on how long you've held it.
Since I don't know where the OP is based I can't suggest any such suppliers outside the UK, but I know of at least one here - Adams Gas.
It's also used pure or mixed with CO2 for pub purposes, so you could try at a pub gas supplier.
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3020
Registered: 4-2003
Posted on Monday, 19 May, 2014 - 12:03 am:   Edit PostDelete PostView Post/Check IP

Then again, you may simply contact your local SY specialist parts supplier. Buy an exchange sphere for a nominal price, forget all these issues, know that it is correct and enjoy a warranty.
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richard george yeaman
Prolific User
Username: richyrich

Post Number: 160
Registered: 4-2012
Posted on Monday, 19 May, 2014 - 12:54 am:   Edit PostDelete PostView Post/Check IP

Hi Richard, I too would go down the replacement route but if I had time and the equipment then I too would have a go much more FUN!!!!

Richard.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 803
Registered: 6-2009
Posted on Monday, 19 May, 2014 - 01:14 am:   Edit PostDelete PostView Post/Check IP

The idea that there exists a "local" Rolls-Royce/Bentley specialist parts supplier in most parts of the world falls into the, "It is to laugh," category. That is unless you stretch local so far as to have no meaning.

Brian, who won't even get into "nominal," particularly with shipping on the heavy stuff
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Paul Yorke
Grand Master
Username: paul_yorke

Post Number: 1198
Registered: 6-2006
Posted on Monday, 19 May, 2014 - 01:35 am:   Edit PostDelete PostView Post/Check IP

The world is now a local market. Can't think of many countries we haven't shipped to.

Shipped by freight may take a little longer , but the effort , time, and expense, spent trying to cobble something together. . . . not to mention the danger . .. .

I guess there are worse ways to get your fun though :-)

I doubt Jim could do them at the bulk price they are done for in the UK, but with shipping within the same continent, it might work out cheaper?
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 805
Registered: 6-2009
Posted on Monday, 19 May, 2014 - 03:06 am:   Edit PostDelete PostView Post/Check IP

Paul,

I know that anyone can ship anything virtually anywhere, but if that's the definition of local then the word has ceased to have any meaning at all.

For me, local is within a 30-minute drive from my home. If it isn't "brick and mortar" where I can walk in and either see the merchandise and/or talk with an experienced hand about same then it isn't local.

I have often wished that Jim was just inside the borders of the United States rather than just outside. Having a friend in Toronto for years we've both stopped sending things other than letters due to the unbelievable escalation in postage for parcels between the US and Canada. The same thought was had for Ralph Curzon (and I think Hyphen Repairs is still a going concern).

Also, at least sometimes, it's not an issue of cobbling anything together. For accumulator rebuilds the kits are either from Crewe Original or one of "the usual suspects" in the UK if you're trying to source them in the USA. Some people actually like doing this work. It also keeps firsthand knowledge alive in the current generation of custodians to be passed along to the next.

Brian, who gets great satisfaction at the end of a "job well done" but who seldom truly enjoys doing the job itself (but I'm a RR owner "in the hinterlands" and one does what one must)
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 402
Registered: 5-2012
Posted on Monday, 19 May, 2014 - 03:35 am:   Edit PostDelete PostView Post/Check IP

Here's the nominal price my local RR dealer quoted for a replacement sphere, with a warranty of course:

---------------------------------------

Steve Csizmar (scsizmar@towbinauto.com)

The brake accumulator is $2202.63 each. There are two on the car and both should be done together.

Thank you Steve

-----Original Message-----
From: Jason Brown [mailto:jbrown@towbinauto.com]
Sent: Wednesday, May 30, 2012 3:08 PM
To: Steve Csizmar; TTURNER@towbinauto.com
Subject: FW: WEBSITE: PARTS



-----Original Message-----
From: geoffwootton@hotmail.com [mailto:geoffwootton@hotmail.com]
Sent: Wednesday, May 30, 2012 3:01 PM
To: jbrown@towbinauto.com
Subject: WEBSITE: PARTS

PARTS REQUEST

SUBMITTED: 05/30/2012 18:00:42

CONTACT INFORMATION
First Name: Geoff
Last Name: Wootton
E-mail: geoffwootton@hotmail.com
Phone: 813 334 1646

VEHICLE INFORMATION
Year: 1974
Make: Rolls Royce
Model: Silver Shadow
VIN: SRX18501

ADDITIONAL INFORMATION:
Hydraulic Accumulator Sphere.

----------------------------------


I took the other option - 10 bucks for a recharge.


Geoff
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Omar M. Shams
Grand Master
Username: omar

Post Number: 394
Registered: 4-2009
Posted on Monday, 19 May, 2014 - 03:41 am:   Edit PostDelete PostView Post/Check IP

Dear Paul,
I would love disposable spheres. If only!!! but tell me this: which airline knowingly puts a small pressure vessel with 1000 psi of pressure in its hold??
I have to declare lap top batteries and all sorts of insignificant things whenever I put things on aeroplanes.
You have been my primary source of parts for many years now - if you can get me dsposable spheres that will not endanger the airline industry, PM me.
Thnaks
Omar
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 403
Registered: 5-2012
Posted on Monday, 19 May, 2014 - 03:55 am:   Edit PostDelete PostView Post/Check IP

Omar

That raises a very interesting point. When I was researching options for replacement spheres in 2012 I raised the issue of transporting charged spheres with a UK supplier, given that in the US it is illegal to use air freight for such items. The response was "we have never had any problems in the past". I wondered if the word "problems" in this context equated to a plane being blown out of the sky by one of these spheres exploding in the cargo hold.

Geoff
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 58
Registered: 5-2013
Posted on Monday, 19 May, 2014 - 05:28 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

At 1,000 PSI initial charging pressure, we have 1,000 / 14.7 = 68 atmospheres in the accumulator and at sea-level we have 1 atmosphere outside. So the container must withstand 67 atmospheres at sea-level and 68 atmospheres on the moon. And we know it can contain 2,500 / 14.7 = 170 atmospheres under normal use.

There is virtually zero danger of containment breach *for a non-defective unit* in an aircraft hold, however that does not change the shipping laws. You can ship without proper disclosure, but I suspect that if you get caught, it will cost more than the alternatives discussed, and given the attention on airline cargo and x-rays, I suspect that this will be discovered. So, probably not a good idea.

I have developed the capacity to remove, rebuild and re-charge my accumulators from scratch, with the invaluable ideas I've gotten from you guys. I think I have spent less that $600 all in, and that includes a wrench for disassembly, 2,500 PSI hydraulic pressure bench testing (Thanks, Jim), and Sufficient Nitrogen for 15 charges. I can provide a detailed list of materials and costs, if anybody is interested...

(There go those voices again, Paul Yorke. I'm thinking that this should be "By Popular Demand" (-: )

Chris.
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Jan Forrest
Grand Master
Username: got_one

Post Number: 544
Registered: 1-2008
Posted on Monday, 19 May, 2014 - 08:42 pm:   Edit PostDelete PostView Post/Check IP

At least in theory the UK Post Office (and Parcel Force) will not ship pressurised containers or flammable fluids, so you should revert to using specialist couriers. Most couriers aren't particularly interested in the contents of the parcels they deliver - other than the insurable value of them.
As for recharging: I recharged mine with dessicated breathing air from a dive cylinder a couple of years ago and they still seem fine. As I said at the time, the 20% O2 in the mix shouldn't cause many problems as the hydraulic fluid will be absorbing atmospheric oxygen from the moment you open the bottle.
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 59
Registered: 5-2013
Posted on Tuesday, 20 May, 2014 - 02:35 am:   Edit PostDelete PostView Post/Check IP

Hi Jan,

I've heard of the "compressed air" camp. I may have heard of it from you! I have two observations:



First, I've read the argument that oxygen is only 20% of the atmosphere, so should be a negligible consideration. 20% is enough for fire and rust, but I'm withholding judgment, so I'm very interested to follow the long term results of your experiment. I'm skeptical that the oxygen is a negligible component of diaphragm failure, but I'm also skeptical that diaphragm failure is the primary cause of accumulator failure. I suspect that diaphragm failure is less prevalent than check valve failure, by which I mean depressurization.

I'd like to hear from the guys that have rebuilt more than two accumulators. Jim Walters? Richard Treacy? (Please forgive me if you are in this group and I have ignorantly excluded you.) Which, in your experience, is more frequent, diaphragm failures or check valve leaks?

My blind view of this elephant: When I rebuilt my accumulators, the failure was the compressed gas check valve and not the diaphragm. I can say nothing about the erstwhile compressed gas which was of unknown composition because the gas had long ago leaked out and these diaphragms were plastered against the lower half of the sphere, sandwiched between brake fluid and steel, completely isolated from gas considerations, but mechanically intact and completely functional. I think I've read that check valve leaks are more prevalent than diaphragm failures and my experience supports this, meaning much of this discussion is probably academic. If you're right, and the compressed air is no more debilitating than nitrogen, then, at some future point, I may wish that I had relied on SCUBA shops over industrial gas suppliers.



Second, I know that brake fluid is "hygroscopic" meaning it likes to absorb water from the environment, but I wasn't aware that it could/would absorb oxygen. Am I misunderstanding?

Chris.
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Jim Walters
Experienced User
Username: jim_walters

Post Number: 17
Registered: 1-2014
Posted on Tuesday, 20 May, 2014 - 04:24 am:   Edit PostDelete PostView Post/Check IP

Having rebuilt lots of these over the past 40 years I've been in business I can say this. When dismantled, most still have some pressure in them. I would say about 20% are from neglected cars and the diaphragms are torn with fluid on both sides of the membrane indicating to me continued use with no gas pressure in the sphere. I think it is rare for the check valves to leak after the plastic ball, O ring and cap are on. How would you tell anyway? I used to put them in a pan of water overnight to check for bubbles but haven't bothered doing that for years as none ever appeared. The gas in my opinion is much more likely to permeate the diaphragm than the crushed plastic ball and O ring cap seal. I would bet 99% of the depressurization comes from the gas permeating the membrane. I would think the amount of use, heating, cooling cycles etc. would be a factor in the speed of permeation, as well as the gas used. As I already have nitrogen on hand for AC work, I'll continue to use it for the spheres. Pure nitrogen does have advantages over air, one is that it is dry when air is not. I have found the occasional sphere that was rusty on the gas side. Perhaps air was used as the charging gas, and the moisture in that air caused the rust. Just conjecture, but in my opinion plausible.

SRE22493 NAC-05370
www.bristolmotors.com
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 811
Registered: 6-2009
Posted on Tuesday, 20 May, 2014 - 04:48 am:   Edit PostDelete PostView Post/Check IP

I've rebuilt more than two accumulators and it was interesting to see how the diaphragm design was tweaked. The new ones that I received all had a much thicker "bubble" of material at the center while at least one older one did not. I can personally envision a diaphragm rupture with the old version (and I've been told this is most common when the gas pressure is completely gone and the diaphragm gets pushed into the top of the charge port repeatedly over time), but not with the new ones.

I'm sure that the gas can migrate through the diaphragm over time regardless of what the gas is. I also know that there are plenty of accumulators that have been rebuilt incorrectly (now know of more than the one I encountered with the nylon/PTFE ball being used as the check valve inside the accumulator) and that certain things can happen with the charge port caps that allow very slow leaks of gas. One of mine did that because the "crush ball" seal was imperfect, but still very good, and the tertiary O-ring had been omitted in the base of the cap. It clearly leaked, but not quickly enough to cause a bubble trail during immersion testing. It has since been recharged and recapped and is holding its charge perfectly.

The Society of Aerospace Engineers (SAE) Aerospace Recommended Practice (ARP) 5316 is generally the standard reference regarding elastomer shelf life. EPDM is generally considered to have an unlimited shelf life in controlled temperature storage and when not exposed to high levels of ozone.

EPDM is not particularly reactive with oxygen, either, that's why I've always believed that dessicated air would probably serve quite adequately as a pressurizing gas. It simply wasn't commonly available until recent years. I stuck with nitrogen because I was able to source it locally, but was just about to use dessicated air. I can see no reason why any inert gas would not likely be quite suitable, either.

The diaphragms, though very thick, are still, essentially, not different than the walls of your common balloon. They will allow very slow permeation by gas. It's the time scale that's radically different.

Brian

P.S.: Most liquids are capable of carrying dissolved gasses.
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 62
Registered: 5-2013
Posted on Tuesday, 20 May, 2014 - 04:49 am:   Edit PostDelete PostView Post/Check IP

Hi Jim,

So, in your experience, you see 20% membrane failures, and 80% depressurization? That really puts the whole question in a much clearer light.

I was considering "leak testing" my rebuilds the same way, so now I know I don't have to spend a whole lot of time with that consideration.

Mine had no "O"-rings in the caps! Now that I know about it, I will be sure to add one.

What is the average time between accumulator re-builds?

Thanks for the help,

Chris.
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Bob uk
Unregistered guest
Posted From: 94.197.122.88
Posted on Tuesday, 20 May, 2014 - 07:09 am:   Edit PostDelete PostView Post/Check IP

Compressed air from a dive shop is probably just as expensive as nitrogen

My local man does Citroen ds ones as well

15 quid New charge valves included

The bottle is 5 ft tall and 1 ft dis

He has a small cage and safety goggles

These accumulators are spheres which makes them very very strong

Even in an engine fire they don't explode

However try hard enough and be stupid enough then they will

(Message approved by david_gore)
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 64
Registered: 5-2013
Posted on Tuesday, 20 May, 2014 - 03:25 pm:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I have re-assembled my two spheres and I have not yet attached the control valves. I built a fixture that permits me to charge the accumulator with my shop compressor. I realize that 125 PSI is nowhere near the correct charge pressure, but since I've never done this before I thought that this might be a good testing step and save me a lot of nitrogen. If it won't hold 125, it won't hold 1,000...

And now I'm beginning to rethink that, because it is not holding 125. It leaks and vigorously enough to blow a pretty good bubble pretty quickly -- maybe a cu.in. per second. So, the next question is, will higher pressure create more downward pressure on the check valve and seal it better than my 125 PSI test case or will is just leak all the more vigorously?

This is a bit discouraging and I'm not exactly sure what I should do to stop this leak. Any ideas?

Thanks for the help,

Chris.
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Jan Forrest
Grand Master
Username: got_one

Post Number: 546
Registered: 1-2008
Posted on Tuesday, 20 May, 2014 - 10:08 pm:   Edit PostDelete PostView Post/Check IP

If you want to buy/rent a nitrogen cylinder it's going to seriously deplete your supply of single malt Scotch whisky tokens!
However if you already own a diving cylinder the cost of the air used is nominal as almost any such cylinder can be completely refilled for around GBP5 across most of the UK. Considering that most dive cylinders hold 7-12 litres @ 230-300BAR you can see that one such cylinder will hold enough gas for dozens of recharges.
How much it costs to buy the kit - including gauges, hoses and adaptors - I couldn't say as I've had mine for several years.
That reminds me: My dive cylinder is well past time for a full pressure (submerged in water) test.
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 3022
Registered: 4-2003
Posted on Tuesday, 20 May, 2014 - 10:58 pm:   Edit PostDelete PostView Post/Check IP

I'm concerned that this Forum is implying that marginal practices like downgrading braking systems are acceptable. People out there are going for nitrogen in tyres (possibly an advantage), yet others are going for air in accumulators (definitely a no-no) it seems.

In Australia, you may buy exchange SY rebuilt spheres with a warranty for a small fraction of the prices quoted by Brian delivered to East Coast capital cities overnight and in two days to Adelaide, Darwin, Perth and to the outback by courier. Brian, have a look at the globe. Australia is a fairly large country, yet economy shipping is possible overnight to just about anywhere here. Even classified as dangerous goods it is fully legal when properly packaged and declared. Your local spares supplier in Sydney provides this service regularly.

Why all the fuss ? These are not expensive items, and they have been in Crewe cars for almost 50 years, and for decades longer in other applications.

RT.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 406
Registered: 5-2012
Posted on Tuesday, 20 May, 2014 - 11:43 pm:   Edit PostDelete PostView Post/Check IP

Hi Richard

The cheapest deal I can find for reconditioned spheres here in the US is from Flying Spares or Introcar in the UK. A reconditioned sphere is listed as 120 ukp. The current GBPUSD exchange rate is 1.68, although Visa will add their cut, so realistically the exchange rate will be 1.75 dollars to the uk pound. Shipping will come in at about 60ukp, so the total is 180 ukp for each sphere, or $315. Since the exchange part has to be shipped to the uk, $105 has to be added, giving a total of $420 for each sphere. This is the best price I have been able to find.

You mention that in Australia you can buy rebuilt spheres at a fraction of the price quoted here in the US. Could you let us know the names of one or more of these companies and if possible their prices. This would be a great service to all of us here in the US. Also, it would be of benefit to these Australian Companies in building up an enthusiastic client base of US owners. I'd be really grateful if you could forward this information. It really seems we are paying way over the odds for our parts.

Geoff.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 815
Registered: 6-2009
Posted on Wednesday, 21 May, 2014 - 12:42 am:   Edit PostDelete PostView Post/Check IP

Richard,

First, I did not quote the price. Second, no one has talked about "downgrading" braking systems. Alternatives to nitrogen do exist, and are more readily available in some places than others.

I do my research, and am mighty thorough about it before making any decisions about changing anything. There are plenty of changes which can be either neutral or, in some instances (though not probably gassing accumulators), improvements.

Like Geoff I invite you to post information about the sources for parts you mention. I am able to call Albers (and other Crewe Original sources here in the US) and go online for Flying Spares, Introcar, etc., and get pricing and shipping information. If there are other sources where parts are available at less expense, and with far less effort on my part having to do rebuilding of various items, I'm all for it. That does, however, mean I need contact information at the very least and ideally a website or websites that allow e-commerce.

Brian
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 76
Registered: 5-2013
Posted on Sunday, 25 May, 2014 - 06:17 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I have lapped the check valve seat, as recommended, and I'll have a lot more to tell you later. The leak at the valve is probably a tenth of what I saw before, which is a good result. Can I do better?

So this raises the question, "What can I reasonably expect as excellent results?" Zero? Undetectable? Detectable, but small?

Is the check valve really the principle containment, or is it simply a retard until I install the cap, meaning the cap is the really and truly, final seal.

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 831
Registered: 6-2009
Posted on Sunday, 25 May, 2014 - 07:24 am:   Edit PostDelete PostView Post/Check IP

Chris,

The answer you seek has already been discussed in this thread:

1. You cannot expect zero. I know of no one who has ever had anything other than detectable, but small-ish with the original ball-bearing setup where both the bearing and seat are "clean."

2. Crewe introduced the PTFE/nylon "crush ball" because of #1.

3. Crewe introduced the O-ring into the base of the charge port because even with #1 & #2 the seal is often still not perfect enough to consistently prevent all nitrogen from escaping.

Brian
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Omar M. Shams
Grand Master
Username: omar

Post Number: 396
Registered: 4-2009
Posted on Sunday, 25 May, 2014 - 02:50 pm:   Edit PostDelete PostView Post/Check IP

perhps the time is right for someone to design a replacement valve for the "not so good" crushed-ball design. Could we not put some kind of high pressure shraeder valve assembly?
There must be a better way of sealing pressure using a modern check valve than the cumbersome and not very effective original design.
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 412
Registered: 5-2012
Posted on Sunday, 25 May, 2014 - 11:02 pm:   Edit PostDelete PostView Post/Check IP

Omar

This has already been done. If you check out the Flying Spares section Brakes/Accumulators and look at the diagram of their reconditioning kits you will see that the inner ball bearing seal has been replaced by a machined pin with a small O-ring. This forms a very effective seal. When I recharged my accumulators with this pin fitted, there was no leak at all and the crushed nylon ball was not required and indeed, was not supplied with the kit. It is traditional to charge to over 1000 psi to compensate for the nitrogen loss as the outer cap and nylon ball is fitted. This is no longer necessary using the FS mod. I detected no loss of nitrogen at all when I disconnected my recharged spheres from the charging station.

Geoff
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 832
Registered: 6-2009
Posted on Monday, 26 May, 2014 - 12:49 am:   Edit PostDelete PostView Post/Check IP

Geoff,

Yes, that modification, which is a clear improvement, makes infinite sense and FS has been selling it for years now. Were I in the market for an accumulator rebuild kit I'd by theirs over Crewe Original in a heartbeat.

It also puts lie to the often repeated variants on the, "Crewe did not accept anything but the best and always tried to find better solutions," mantra.

The SY series cars were in production from 1965 through 1980 and if there isn't a better example of trying to keep fudging your way around a bad design, rather than making a simple design change (you can't get simpler than the FS mod) this would be it.

The longer I've owned both of my cars, which are both from near the end of the SY era, and still find things done on them that people had been identifying as weak spots for years, the less I buy into the myth of the acceptance only of "perfection" at Rolls-Royce.

It doesn't mean I don't love my cars, I've simply become very realistic about what the company did, or did not, do to cut costs during that era.

Brian
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 78
Registered: 5-2013
Posted on Saturday, 31 May, 2014 - 12:35 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

I am announcing a new thread here because there have been a number of participants in this thread who have expressed interest in the topic and will probably benefit.

This forum doesn't have a way to post a link to other threads, so the best I can do is give you a title and an original posting time:

"Accumulator Check Valve" Posted on Saturday, 31 May, 2014 - 12:21 am by "Chris Miller"

Chris.

P.S. Is there a way to post links to other threads?}
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 852
Registered: 6-2009
Posted on Saturday, 31 May, 2014 - 12:43 am:   Edit PostDelete PostView Post/Check IP

Chris,

Yes, you can post links to other threads.

Click on the Formatting link under the Documentation category in the navigation list on the left side of your forums screen (or use the direct link I've included above). Then search for "hyperlink" within the page. I am presuming that you use http://au.rrforums.net/cgi-bin/forum/discus.pl as the direct link to the forums page when I make reference to the navigation list.

Here's the direct click-through link to your Accumulator Check Valve thread.

Brian
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 854
Registered: 6-2009
Posted on Saturday, 31 May, 2014 - 06:48 am:   Edit PostDelete PostView Post/Check IP

P.S. to Chris: I had forgotten this, but hovering over the little computer icon that shows up at the top of each post in a thread shows you the URL/link to that thread as a whole, starting from the first post. If you're using a PC you can simply right click on it and choose "copy link <location|address>" to snag it.

The only way I know of to get to a specific post in a thread is to use the forums search function with enough keywords specific to that post to have it returned. You can then right click on any of the keywords that show up in the search result under a given thread title to snag the URL for the specific post in question.

Brian
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 81
Registered: 5-2013
Posted on Wednesday, 04 June, 2014 - 01:57 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

Now that I am holding gas pressure, I need to do hydraulic testing. I have a hand-pump that can produce 10,000 PSI of Hydraulic pressure, so I can pump brake fluid into the Accumulator Control Valve to confirm that it is working correctly. I have capped the operational output line with a gauge. I expect that I can pump fluid in and it will fill the accumulator until I reach cut-out pressure, at which time the ACV will bypass the accumulator and the fluid will return to my reservoir. I also expect that the ACV will preserve this pressure after I stop filling.

So, how long can I expect the ACV to preserve the pressure? Should I expect a slow leak?
To relieve the pressure, I use the bleeder valve?
At what pressure does the pressure switch cutout the red dashboard low-pressure warning light?

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 857
Registered: 6-2009
Posted on Wednesday, 04 June, 2014 - 06:08 am:   Edit PostDelete PostView Post/Check IP

Chris,

The pressure values and ranges for testing the accumulators are documented in chapter G7 for the RR363 cars. The pressure range for the pressure switches in Chapter G14.

You will use the bleeder valve to relieve the pressure. Have a hose attached and a jug ready to receive the fluid.

I would expect the possibility of a very small pressure leak from the ACV. Most cars will depressurize after sitting for some period of time. When that period is a few days to a few weeks it's generally declared within normal limits. If your pressure is being depleted with anything approaching a rapid rate something's not right.

Brian
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Bob uk
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Posted From: 94.197.122.73
Posted on Wednesday, 04 June, 2014 - 06:12 am:   Edit PostDelete PostView Post/Check IP

If the sphere is charged then due to it's very simple mechanism

It cannot fail to work

So to test fit to.car and do the pump the pedal test

Screw 3000 psi gauge into bleed port

Start engine gauge will jump straight to 1000 psi which is nitrogen charge pressure

Then the pumps will force the diaphragms into the nitrogen

At idle the gauge will go up in pulses in time with the engine

At about -look in manual for pressure -2900psi the relief dumps back to tank

Also watch tank levels drop as accumulators fill up

With engine off pump pedal till lights show I get over 60

Doing this will also purge that section of air

(Message approved by david_gore)
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gordon le feuvre
Experienced User
Username: triumph

Post Number: 35
Registered: 7-2012
Posted on Thursday, 05 June, 2014 - 05:33 am:   Edit PostDelete PostView Post/Check IP

2300 psi, then it will stabilize at about 2100.At this time the pressure of the pump is directed straight back to the reservoir via the rubber low pressure return. If you then crack off bleed screw to let pressure in sphere drop, the internal valve in the accumulator will cut in at about 17/1850 psi to again direct the pump pressure into sphere going back up to 2300, and so on.
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Chris Miller
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Username: cjm51213

Post Number: 82
Registered: 5-2013
Posted on Thursday, 05 June, 2014 - 06:15 am:   Edit PostDelete PostView Post/Check IP

Hi Gordon,

This is helpful and just what I needed. I did follow Brian's advice but I must have a different set of manuals, because I found no specs on pages G7 or G14, nor in sections G7 (pgs:G31-G39) or G14 (pgs: G67-G...).

I have an hydraulic hand pump and gauges in several places so I can measure the service pressure when the ACV changes state from "bypass" to "fill" and the pressure during operation in of those phases. This level of testing is probably not usually necessary, but I have never rebuilt an ACV before, and the time to discover and correct defects is when it is on the bench. You have described correct behavior in a measurable way.

Do you know the pressure that activates the red dashboard warning light cut-out switch? I'll want to measure that too, since I don't know for sure that the switch works.

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 859
Registered: 6-2009
Posted on Thursday, 05 June, 2014 - 07:24 am:   Edit PostDelete PostView Post/Check IP

http://rrtechnical.info/SY/TSD4200/tsd4200_g.htm
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 83
Registered: 5-2013
Posted on Thursday, 05 June, 2014 - 07:30 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

That completely explains it. All three of mine are Shadow I, so I was using a different manual. I doubt things have changed in this area, so I should snag copies of these in addition.

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 860
Registered: 6-2009
Posted on Thursday, 05 June, 2014 - 07:33 am:   Edit PostDelete PostView Post/Check IP

http://rrtechnical.info/SY/TSD4200/tsd4200_g.htm for the SY Two Series cars.

It's still in Chapter G of the SY One Series Workshop Manual, too, but both accumulator and pressure switch testing are in Section G6 - Hydraulic Accumulators.
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Bob uk
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Posted From: 94.197.122.79
Posted on Thursday, 05 June, 2014 - 10:39 am:   Edit PostDelete PostView Post/Check IP

Chris

You are getting over complicated and not understanding exactly how the system works

Carefully read the whole chapter study the schematic drawings

When Citroen and RR designed the system they also designed the testing and repair which is in that chapter
These procedures are designed to be easy so that Bush mechanics can fix the car

(Message approved by david_gore)
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 84
Registered: 5-2013
Posted on Thursday, 05 June, 2014 - 02:50 pm:   Edit PostDelete PostView Post/Check IP

Hi Bob,

The testing procedures in the manual assume that the parts are installed on the car and mine are not; I've just re-built them, so they are on the bench. To follow the manual, I have to install the parts, test and then remove any parts that require re-work. It just makes much more sense to bench test them first. This has the additional benefit that after I finally do reassemble the system, I will be able to distinguish defective parts from defective installation; errors come in many forms and the fewer the options, the clearer the diagnosis.

Thanks for the help,

Chris.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 861
Registered: 6-2009
Posted on Thursday, 05 June, 2014 - 11:47 pm:   Edit PostDelete PostView Post/Check IP

Chris,

If you want to have at bench testing go for it, you now have way more than enough information to do it.

In reality, though, it is overkill. I have yet to hear of anyone who's rebuilt accumulators who has any issue other than leaks and have yet to hear of an ACV failure from other than extreme neglect causing corrosion that causes seal wear. Once you've taken the ACV apart and cleaned everything up in denatured alcohol/methylated spirits, if the parts themselves look good (including a smooth interior on the ACV body bore) you should be fine if you install new seals and put everything together correctly.

I was actually surprised at how much simpler the ACV is in practice than it's presented as being in the manuals. While the thing's a PITA to get out (and put back) tearing it down and rebuilding it is a snap compared to many other tasks.

Brian
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 419
Registered: 5-2012
Posted on Thursday, 05 June, 2014 - 11:50 pm:   Edit PostDelete PostView Post/Check IP

Hi Chris

Would it not be quicker to refit the accumulators and test them on the car. If in the unlikely event you have to remove them again you will be able to do the job so much quicker than the first time. When I removed the accumulators from my car it took a couple of days. This included time going to the local tool store and buying extension rods and various other tools to facilitate the removal. The second time it took me about an hour. Once you are familiar with the job and have the tools to hand, it really isn't difficult to remove the accumulators, especially on a "Series 1" car. You have to gauge the time it will take if you do have to remove them again, against the time it will take to fabricate lines to connect the ACV's to your hydraulic pump.

Geoff
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 85
Registered: 5-2013
Posted on Friday, 06 June, 2014 - 12:50 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

Yeah, I think I'm in pretty good shape, too, and I doubt that I will find any problems with the ACV.

While the '72 is still relatively new to me, the '71 has always listed slightly, but detectably to the driver's side, and that is possibly ride control, which is hydraulic and something that I will need to "debug", so the bench testing ability that I am developing is actually more for that than the ACV. Since we all understand the ACV so well, this is the time to also develop bench testing facility -- pumps, gauges and procedures. I suspect that testing the ride control rams in place is probably much easier than removing them, and the "open door fast adjust" has never done anything detectable, so I have to split the problem, and this seems like a good way to do that.

There are two types of errors, interestingly called "Type I" and "Type II". One is where you draw the wrong conclusion, and the other is where you draw the right conclusion, but your standard is wrong. There are two ways I could conclude that I had a defective part: 1) the part is defective and the test is correct, or 2) the part is correct the test is defective. Since we all understand the ACV so well, this is more about finding and eliminating the "Type II" errors, i.e., making sure I know what my tests mean and that I am really testing what I think I am testing.

The hydraulic hand pump I have wasn't very expensive. (The bottle jack implementation that Jim made is even better! I'd have done that if I'd known enough about bottle jacks.) I have a gauge that I think will work. I have a five-gallon bucket of castor oil. So I think I have everything I need to do hydraulic bench testing, but I won't be sure until I actually bench test something.

In any case, a quick bench test beats the snot out of installing a part only to find that it doesn't work and has to be re-removed to be fixed, and that is WAY better than re-removing a part only to find that the problem is actually in a different place altogether! The bench test let's me reduce the scope of possibilities.

I hear you guys when you tell me that the ACV is unlikely in the extreme to exhibit any defect, and that is good news. I don't think I made any mistakes with it, but since this is the first time I have ever done this, who knows? I have made some incredibly stupid mistakes before...

Thanks for the guidance,

Chris.
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Chris Miller
Frequent User
Username: cjm51213

Post Number: 86
Registered: 5-2013
Posted on Friday, 06 June, 2014 - 01:11 am:   Edit PostDelete PostView Post/Check IP

Hi Geoff,

The pump has an integral gauge and a line that already fits the ACV input; I built the operational output pressure gauge last summer, so I can test the operational pressure the Sphere/ACV is delivering; the return is a vinyl tube hose-clamped onto the bleed valve going to a tub. I have a five-gallon bucket of castor oil. Since I haven't done this, I have no idea what pitfalls await me, but I think it should be pretty straight forward. Even if I spend an hour testing the accumulator/ACV, and I suspect that it will take much less than that, I think I'm in pretty good shape.

One more fall out of the bench testing: Since I can measure the volume of fluid I put in the sphere, I can also measure the initial charge of Nitrogen. My tests show me that my redesigned valve permits no detectable loss of pressure, but I have no way to measure the initial charge that actually gets into the sphere, a problem I recognized with previous re-designs of the check valve. My bench tests, masquerading as "Hydraulic" tests will also give me pressure and volume measurements that will allow me to calculate my initial Nitrogen charge.

Thanks for the help,

Chris.
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Bob uk
Unregistered guest
Posted From: 94.197.122.77
Posted on Friday, 06 June, 2014 - 10:59 am:   Edit PostDelete PostView Post/Check IP

To test the accumulator

Remove valve body from car

Fit accumulator to valve body

Fit pressure gauge

Screw bleed nipple into where the.stainless flexible went

Connect low pressure hose to catch tank this is the dump line

Connect pump to where large pipe from engine pump fitted

Connect ohm meter to switch overside to earth or use test light and pp9 volt battery

Pump up system

Do not not never no how
exceed 3000 Psi

Do not connect pump direct to accumulator without a relief valve set so that the pressure cannot exceed 3000psi

The accumulators are part of the valve bodies

Use dot 3 or 4

This system is very reliable and a genuine RR mechanic told me that 3 things he in the main he finds

Hoses
Nitrogen
Dirty dot

On many cars with bad brakes he does these 3 things and brakes are much better

The brakes on my car 1974 very good the only parts changed in 25 years

Are nitrogen,pads front.discs,hoses and metal pipes so the system is very reliable

(Message approved by david_gore)
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John Beech
Frequent User
Username: jbeech

Post Number: 79
Registered: 10-2016
Posted on Thursday, 01 December, 2016 - 02:02 am:   Edit PostDelete PostView Post/Check IP

Geoff asked early on within this thread whether the SY1 accumulators could be recharged in situ and never received an answer other than Jim doesn't because he has to stand behind his work. This begs the question, can the accumulators be recharged in the car?

Also, if the answer is yes, does anyone know (off the top of their head) what's the connection, e.g. 3/8-24, or 1/4" NPT, or . . . ?
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Geoff Wootton
Grand Master
Username: dounraey

Post Number: 1500
Registered: 5-2012
Posted on Thursday, 01 December, 2016 - 03:45 am:   Edit PostDelete PostView Post/Check IP

Hi John

On the earlier cars where the accumulator spheres are on the left side of the engine it can be done. Just remove the base plate. I have read warnings about doing this in case the diaphragm is holed, however I think starting with low pressure would soon identify this issue.

A lot of charging stations require a schrader valve. If this is the case with your setup, then pick up a Watts A762 3/8 1/8 coupler from your local Lowes store. You can then fit the schrader valve connector. The Watts coupler has the correct thread for the accumulator and is rated at 1000 psi.

When you pressurize the accumulator there is the possibility of a loud crack as the diaphragm flips over. This should not occur when recharging an existing accumulator, but if you have just fitted a new diaphragm this may be the case. When I rebuilt my spheres I did try to flip the diaphragm during the rebuild but it always returned to it's relaxed state. Charging flips the diaphragm "inside out" with the accompanying loud crack. I mention this to help save on your laundry bill.

It's worth downloading Brian's document

Constructing a Nitrogen Charging Unit for Rolls-Royce & Bentley RR363 Accumulators and Recharging Them

https://drive.google.com/uc?export=download&id=0B61gLtsXt4oqSGhUZEJ2M1RDMm8

Geoff
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John Beech
Frequent User
Username: jbeech

Post Number: 81
Registered: 10-2016
Posted on Thursday, 01 December, 2016 - 05:41 am:   Edit PostDelete PostView Post/Check IP

Hi Geoff,

I already built a nitrogen charging system. I purchased a 2nd hand nitrogen bottle from a pawn shop, which included 0-600psi regulator. This, for less than the price of a new bottle from Airgas (the local industrial supplier). The issue for me of using a paintball nitrogen-set up like Brian details is they exchange N-cylinders locally. So while they're happy enough to refill it, this requires going to the plant, which is downtown Orlando. I try hard to avoid 'that' because even though it's only 25 miles away, what with traffic, that trip tears a huge hole in my morning. Thus, I opted for an industrial bottle I can simply exchange 5 miles away without ever getting on I-4. Plus, I trust the adjustable regulator more than the preset version.
N-bottle and 600psi regulator1


Next, I purchase a 2500psi regulator (cost the same within single digits as the similar 1500pis regulator). 1000psi is within the sweet spot for both so why not? While I was at it, I also purchased the assorted fittings plus a 12' long hose rated to 10,000psi (= incredible overkill but that's just me). It has the fitting mentioned in the Hunter-Vogel article (3/8 FIP going off memory) for attaching to the accumulator.
N-bottle and 600psi regulator2


However, what's become clear as mud is whether I can recharge the accumulator while it's installed on the car, or if this fitting is a different one for when servicing on the workbench . . . so I await clarity on the subject.

Meanwhile, after charging the accumulator I think I'd rather have the 600psi regulator on the bottle. I'll set it to 200psi and use a conventional airline and gauge to air up tires through a Schrader valve (though I'm not convinced it's really worth the bother versus air other than because it's dry gas).

Finally, while I was at it, I also built the test-gauge set up.
N-bottle and 600psi regulator3

This is merely a glycerin filled 1000psi gauge, which is very inexpensive (USD$12) and I elected to use a high pressure disconnect for the convenience of subsequent storage of the hose. This based on the Hunter-Vogel drawing.

All I did differently is add a 90į fitting to the T plus a petcock valve (just for convenience when purging the air versus a brake bleeder).

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