Separating the Accumulator from the A... Log Out | Topics | Search
Moderators | Register | Edit Profile

Australian RR Forums » Silver Shadow Series » Threads to 2015 » Separating the Accumulator from the ACV . . . « Previous Next »

Author Message
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 944
Registered: 6-2009
Posted on Wednesday, 06 August, 2014 - 08:56:   Edit PostDelete PostView Post/Check IP

. . . when you'd like to allow the ACV to remain in situ on the car.

I will preface this post by saying that I am thinking out loud based on information that's been collected on these forums and elsewhere over the last several months. None of the things I'm about to discuss has been tried by me, but I'm considering different options.

Recently, regular poster Bob_uk mentioned that his own technique for tightening the accumulator to the ACV was using a strap wrench and nipping it up tight with that. The torque tightening figure for this connection is shown as 50-60 lb ft in the Series One SY workshop manual and as 55-60 lb ft in the Series Two workshop manual. For comparison, lug nuts have a torque figure of 45-50 lb ft, so the "high end" on a lug nut is roughly equivalent of the "low end" on the accumulator-to-ACV connection.

My personal experience suggests that some there is a tendency to go overboard as far as tightening the accumulator to the ACV. It's very easy to knock lug nuts loose with the supplied wrench and it should be equally easy to get the accumulator to unscrew from the ACV using either a strap wrench or chain wrench around the clamping ring or a deep 15/16" socket on the end of a ratchet or breaker bar on the hex that surrounds the charging valve after the cap is removed.

Given the amount of torque on the clamping ring (provided it was applied as specified) there is no way that it should ever budge if the decision to use the socket with ratchet/breaker bar on the bottom hex fitting is selected as the unscrewing method.

As we all know, it does not take superhuman strength to get a lug nut to break loose. It should not take superhuman strength to get an accumulator to unscrew from the ACV, either.

In the future I will likely use Bob_uk's technique and not completely tighten the accumulator to the ACV while both are off of the car. I had been hand tightening and then giving a gentle tap or two with a hammer (and I do mean gentle - not vigorous) to nip things up. It seems to me that simply hand tightening and then to use a strap wrench after the assembly is back in place on the car to nip the accumulator up tight is quite sufficient. This should also make it easily possible to use a strap wrench to unscrew the accumulator from the ACV should that become necessary.

Right now I have a situation where I would like to get an accumulator that seems to have a very, very slow leak going on through the charge cap off of its ACV without removing the ACV from the car. Since recharging is the whole goal I am inclined to try the socket technique if I cannot get the accumulator loose using only a strap wrench, which I will try first.

Brian
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.87
Posted on Wednesday, 06 August, 2014 - 11:07:   Edit PostDelete PostView Post/Check IP

Often torque settings that are between two figures are often guidance where a torque wrench would be awkward. These two settings are 20% apart which indicates a firm nip. I watch the thread area as well I like to see it turn a bit to stretch the thread to give a modicum spring against the seal

I was miffed when I saw all the problems people were getting And also empathetic because continually doing the same old fault is expensive and stressful which is not a hobby it's a drudge.

Notice that RR use the now infamous nip.
Because of my cultural background in brit iron words like tad nip and smack it with an 'ammer are words used in even the highest engineering circles for specs that are difficult to quantify.

RR expected that only engineers would do their cars it was never designed as a diy car to be restored 40 years later and neither was any other car.

My accumulators? have lasted 18 years and are still.good. My RR man emphatically states most old shadows he sees with poor brakes do still have nitrogen and once sorted the brakes are good apart from other normal car brake stuff. Once done the car will go for years with just normal car servicing. Which is all I have done.

I can't understand all these brake problems in what is a very not complicated system the complexity inside the bits does not make repairs difficult plus the information available far exceeds lots of other old cars.

And RR enthusiasts can get precious. In motor factors they don't bat an eye lid.

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.92
Posted on Thursday, 07 August, 2014 - 06:08:   Edit PostDelete PostView Post/Check IP

For Brian,
Thankyou for your posting and read it as a compliment.

My strap wrench is intended for oil filters and will easily crush a filter should it be too tight.

Sykes Pickavant make these 1/2 drive. Less than £20. Chain type with teeth for getting really stuck in also available.

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 174
Registered: 5-2013
Posted on Saturday, 09 August, 2014 - 05:01:   Edit PostDelete PostView Post/Check IP

Hi Brian,

I speak from experience.

First, there is insufficient clearance to put a fabric strap on a sphere in situ; the clearance behind the union ring on my '72 is nearly zero and the clearance between spheres is zero. There might be room for a steel strap like an oil filter wrench between the sphere and the engine, but not between the spheres. I've never seen a strap wrench with that sort of a design. The 15/16 hex is a fine "handle" and will do exactly as you suspect, meaning turn the sphere in total, not just the lower hemisphere.

Moderator Edit:

Some repetitious content from another thread was republished by our contributor and has been removed as it was publicly and privately challenged by other members with experience and qualification to do so. The original content remains in another thread together with the subsequent input by members and a concluding comment by myself advising professional advice should be sought before implementing the offered advice.


There is an additional requirement that the sphere not work itself loose, and that requirement is met by the lower brace and the threaded rod on the check valve cap. If it does start to work loose, you will see brake fluid leaks long before you suffer a failure, so there is even a built-in warning. Maybe but not always and also may not be seen in time.

Provocative comment removed.


For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 952
Registered: 6-2009
Posted on Saturday, 09 August, 2014 - 05:32:   Edit PostDelete PostView Post/Check IP

Bob,

You're quite welcome.

Chris, just FYI, this is one of those instances where the differences between the SY1 accumulator sphere mounting configuration and SY2 is huge.

Yours are side-by-side on one side of the engine. Mine are one to a side on each side of the engine. The difference in space constraints, and possible tool options, is obvious.

That being said, I personally prefer the idea of a 15/16" deep socket on the bottom hex myself. The "remove and recharge" project will be in the works soon and I'll probably experiment to see which method is most convenient and effective given the space I have to work with and degree of torque necessary to break the accumulator loose from the ACV.

Brian, who will still tighten the accumulator to the ACV such that it's hand tight, then "nipped" per Bob's description

P.S. to Bob: I've never quite understood how one is supposed to definitively know whether one has hit the specified torque specs on a wide number of fasteners. You can't possibly use a torque wrench in many instances. I have always used the "tight enough to stop turning with ease, then just the slightest bit more" metric for things that don't have huge torque values (e.g., the clamping ring on the accumulator sphere). Even for that, there's no way to measure it in the workshop, you simply make it tight then throw all your body weight into great pushes on the end of the pin wrench handle several times, followed by a couple of "whack it with a hammer"-s thrown in for good measure.
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 175
Registered: 5-2013
Posted on Saturday, 09 August, 2014 - 05:44:   Edit PostDelete PostView Post/Check IP

Hi Brian,

When I first separated my ACVs from their spheres, it required sufficient torque that I feared damage to the ACV. It required a vise and a three foot handle bolted to the three ACV mounting points, and even with a three-foot handle required a substantial force. I hadn't yet built my sphere union ring pin wrench, but that wouldn't have changed anything except how I would have had to mount things to get them apart. I don't know if this is typical, but I have the accumulators out of the '66 cadaver car, and I am going to rebuild them while I have everything already set up, so I will get a second data point.

If your ACVs are attached like mine were originally, then your breaker bar won't be long enough, unless you are a lot stronger than I am, and I'm pretty strong.

I look forward to hearing your report.

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 953
Registered: 6-2009
Posted on Saturday, 09 August, 2014 - 06:05:   Edit PostDelete PostView Post/Check IP

Chris,

The accumulator and ACV in question were already rebuilt by me and reinstalled last year. It appears that the charge port seal has had a very long, very slow leak. The accumulator is not yet exhausted, but I want it to be fully charged again and to stay that way to the maximum extent possible. I've had this happen once before when the friend I have do the charging for me accidentally omitted the o-ring tertiary seal.

When I first took the ACV assemblies off of the car it didn't take much more than a couple of "whacks with a [3 lb.] hammer" on the flat surface at the end of the ACV body which is there for precisely this purpose. [If anyone wants to argue about this take it up with the folks at the Rolls-Royce Foundation who sponsor the Hydraulics Workshop and the well-known mechanics who stated this and demonstrated said technique.]

When I put the ACV and accumulator back together off the car, before reinstalling the whole assembly, I simply put them together hand tight and then did the "nip up" with a few very gentle whacks of the hammer.

I also use anti-seize lubricant on virtually every threaded connection that I ever take apart and reassemble, and the threads on the accumulator sphere (which are nowhere near to making contact with the fluid when things are back together) were no exception.

Many accumulator to ACV connections are virtually "welded" together due to length of time between now and last separation, no historical use of anti-seize, and the tendency of some to think this connection needs torque not unlike the clamping ring (and completely ignoring the fact that it should be no tighter than a lug nut, which is not all that difficult to break free with a short wrench). Even in the worst cases I've been around it's generally worked better to get the sphere very firmly affixed and give the whacking spot on the ACV a few very insistent whacks to get it to break free.

The first time I had a recalcitrant clamping ring that didn't want to come off I was scared to death to take a hammer to the ring while the accumulator was sitting on a concrete floor (and was, of course, completely discharged prior). It turned out that the advice to give semi-insistent whacks around the circumference of the ring, then trying again to get it off, worked like a charm. The use of anti-seize on reassembly will, hopefully, make this unnecessary for me or whoever next needs to separate the sphere for rebuilding.

Brian
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 176
Registered: 5-2013
Posted on Saturday, 09 August, 2014 - 06:29:   Edit PostDelete PostView Post/Check IP

Hi Brian,

Given that you assembled it the last time it was assembled and that was recently, then I predict that you will have no problem and that the 15/16" "handle" will work exactly the way you expect. You will not be the victim of some over-zealous mechanic, or at least, if you are, you know who to blame. (-:

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Geoff Wootton
Grand Master
Username: dounraey

Post Number: 450
Registered: 5-2012
Posted on Saturday, 09 August, 2014 - 13:57:   Edit PostDelete PostView Post/Check IP

Interestingly, the procedure specified in the SY1 manual to separate the sphere from the acv is to use special tool RH7860 (presumably a deep 15/16" socket) on the hexagon machined on the sphere. It then says "It is of the utmost importance that, when the sphere is unlocked and unscrewed from the valve body, both halves of the sphere MUST rotate as a unit". Quite what to do if the halves start to separate is not specified. I much prefer Paul Yorke's method ( http://au.rrforums.net/forum/messages/17001/14050.html ) of holding the sphere in one hand and tapping the acv round with a copper hammer. (tut tut Paul, you will give the purists' nightmares). I can attest that this is the least damaging method of separating the acv from the sphere.

Geoff.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 954
Registered: 6-2009
Posted on Saturday, 09 August, 2014 - 14:30:   Edit PostDelete PostView Post/Check IP

Geoff,

Any time I'm in a situation where I'm removing the ACV and accumulator from the car as a unit the only way I'd try to separate them is the "hammer applied to the flat spot on the ACV body" to get it screwing off.

However, I find myself in a situation where I do not need, nor do I want, to remove both together. There has been a relative dearth of information regarding how to remove an accumulator from the ACV while leaving the ACV mounted to the car, that's why I was asking.

I had forgotten about the part you quote from the SY1 Workshop Manual. I know there's another thread here that's not that old where the RH7860 tool was mentioned and someone kindly posted a picture of same after I asked. It really is just a slight variation on a typical deep socket.

Brian, who figures the probability of both halves of the sphere not rotating as a unit is about as close to zero as one can possibly get without being there (provided the clamping ring was correctly torqued)
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 956
Registered: 6-2009
Posted on Monday, 11 August, 2014 - 01:07:   Edit PostDelete PostView Post/Check IP

Just to complete "the circle," the RH7860 tool was discussed very recently (June 2014) on a thread started by Mr. Wootton entitled, RR363 leak Accumulator/valve. An image of said tool can be seen in this post in that thread.

It's not a deep socket, but uses a cut-out style not unlike flare nut wrench to allow you to slide it on to the hex. For myself, if you have a deep 15/16" socket that fits over the port cap and hex fitting that is a superior tool for the job anyway.

Brian
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 185
Registered: 5-2013
Posted on Thursday, 14 August, 2014 - 05:43:   Edit PostDelete PostView Post/Check IP

Hi Folks,

The circle is the top of the accumulator sphere where the ACV threads on. The slanted line represents the threads between the ACV and the sphere. The rest is self explanatory. The conclusion is that 2,000 PSI of pressure in the sphere is equivalent to 40 ft.-lb. of torque on the sphere. Please review my theory, numbers and calculations.

Pressure/Torque Conversion

The coefficient of friction, K, is a bit difficult to quantify, owing to the possible presence or absence of lubricating agents, like RR363 brake fluid, Castor Oil, or anti-seize thread compound. But it seems to range from 0.20 to 0.80 and with an average value of 0.50 the conclusion, as stated above, is 2,000 PSI of pressure in the sphere is equivalent to 40 ft.-lb. of torque on the sphere. Using the full range of K, the range of Torque is

K Torque
0.20 16 ft.-lb.
0.50 40 ft.-lb.
0.80 64 ft.-lb.


I was hoping to show that the bonus torque provided by the hydraulic pressure was very much larger than this, because that was what I suspected, but it is a not insignificant, although modest quantity, within "human" range, meaning a force that can be duplicated by a human with a suitable wrench.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.92
Posted on Thursday, 14 August, 2014 - 08:16:   Edit PostDelete PostView Post/Check IP

Absolute nonsense. I have no idea what this rubbish is meant to show. None of it makes sense. It appears to say that at 2000psi the torque of the sphere connection will be 40 ftlbs. The idea of torturing the sphere is so that the O ring has the correct nip. On this site is a photo of an O ring that has been forced out under pressure. I think the O ring was wrong material but never the less it got squeezed out.
Endless b*****ks like this make me laugh and my dog laugh.

(Message approved by david_gore)
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 967
Registered: 6-2009
Posted on Thursday, 14 August, 2014 - 09:02:   Edit PostDelete PostView Post/Check IP

Removed.
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 188
Registered: 5-2013
Posted on Thursday, 14 August, 2014 - 09:08:   Edit PostDelete PostView Post/Check IP

Hi Brian,

I have apparently confused my demonstration.

Although the equivalent calculation for the containment ring would be quite interesting and fun, this calculation is between the ACV and the sphere. It pertains to the thread topic, "Separating the ACV from the sphere".

It shows that you might be able to use a wrench on the 15/16 handle and remove the sphere, even if it were fully charged; 2,000 PSI translates into an equivalent bonus torque of 40 ft.-lb.

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Brian Vogel
Grand Master
Username: guyslp

Post Number: 968
Registered: 6-2009
Posted on Thursday, 14 August, 2014 - 09:14:   Edit PostDelete PostView Post/Check IP

Chris,

I realized that, sort of, but no one would ever have any reason to try to remove an accumulator from the ACV while the system retains charge.

One does the "pump test," but not for testing purposes, to discharge the system prior to trying to remove the sphere.

At that point the only torque that's holding the sphere to the ACV is whatever you applied when you connected it yourself.

Brian, who knows that 90 ft lb of torque is well within "human unscrewable, with wrench" and can't imagine the mess that would ensue from the fountain of brake fluid that would come flying out were one to do the unscrewing quickly without having discharged the system
Top of pagePrevious messageNext messageBottom of page Link to this message

Chris Miller
Prolific User
Username: cjm51213

Post Number: 189
Registered: 5-2013
Posted on Thursday, 14 August, 2014 - 09:27:   Edit PostDelete PostView Post/Check IP

Hi Brian,

> no one would ever have any reason to try
> to remove an accumulator from the ACV while
> the system retains charge.

No, of course not. Someone should probably issue a safety alert for that, though, just to be sure... (-:

My real point is much more subtle and is left as an exercise for the interested student, but does not detract from the interesting conclusion that hydraulic pressure has an effect on the operational torque of the ACV/sphere junction, regardless of where it starts.

My numbers are accurate, except for K, the coefficient of friction, which is more difficult to evaluate owing to the circumstances that affect friction.

For your consideration,

Chris.
Top of pagePrevious messageNext messageBottom of page Link to this message

Bob uk
Unregistered guest
Posted From: 94.197.122.88
Posted on Thursday, 14 August, 2014 - 09:41:   Edit PostDelete PostView Post/Check IP

OMG a lot of wrong calculations to show that one could undo a sphere with the system is charged why would I want to do that. Why waste a load of RR363. One could take the top hose under pressure and squirt very hot antifreeze in ones face.

(Message approved by david_gore)