Post Number: 49
|Posted on Sunday, 27 November, 2016 - 11:16 am: |
On the subject of recharging accumulators, I've read about a small ball, either steel or nylon. I'm not sure which is fitted to SRX6816 but want to learn before starting on the job of checking pressures and possibly recharging the accumulators. The other question is; is this ball located beneath a protective cap, which is an analog to the cap on a tire valve (Schrader)? And is the ball a loose fit such that removing the cap sees it drop out, or does it need to be pried out? Is the tip of a pocket knife adequate?
Moreover, is there a source other than RR for these, and is it advisable to obtain a couple before attempting to service the accumulators, or are they usually fine to re-use?
Post Number: 2116
|Posted on Sunday, 27 November, 2016 - 12:49 pm: |
In brief, the steel ball bearing is what is used *inside* the accumulator as the stop valve. It is not very good at performing its function.
This led to the use of a plastic ball as a secondary seal on the opening of the charge port *outside* the accumulator that gets crushed into place when the cap is screwed back on. There is also an O-ring as a tertiary seal.
What follows is my own experience and opinion. I expect that others will differ. If one is going to stick with the original steel ball I have found that the plastic ball is virtually useless and a PITA to remove at a later date. How big a PITA can vary from minimal to curse-worthy. The O-ring is as effective or more effective than the plastic ball. What's more effective than either of these (provided you have a reasonable primary stop from the steel ball) is using hydraulic thread sealant when you put on the charge port cap, Loctite 545 being one example. I still always use the O-ring.
What is far superior is the Flying Spares modification to the original primary valve configuration and is included in their accumulator rebuild kits, a detail shot of which is:
It makes so much more sense to use a pin that centers in the port with a tiny O-ring to form the seal and that has a machined top that centers the spring on that side of the pin. The worst part of rebuilding the accumulator for me, other than the struggle to get them open in the first place, was trying to get that *%$# steel ball, spring and micro circlip back in place on the inside of the charge port.
After rebuilding several accumulators I am a contrarian and would always recommend trying to recharge them before going to the trouble to rebuild them. The trick is making sure you get a good seal on the charge port or else you will experience a leak down of your pressure over a period of days (worst case) to months.
I have never found a source other than Crewe Original or "the usual suspects" (that is Flying Spares or Introcar or similar) for the accumulator diaphragms which you really must have for a rebuild and would want to install if you ever took the sphere apart.
The rest of the seals are dirt common EPDM O-rings in standard sizes.
Also, have a look at:
SY Brakes and Hydraulics
The Brake Pedal Test & Other Hydraulic System Diagnostics
Flush and Bleed Your Silver Shadow/Bentley T Hydraulics/Brakes the Easy Way
Building a Hydraulic Pressure Test Gauge (B.Vogel)
Building Your Own Hydraulic Pressure Gauge (Vogel mod of Hunter)
Constructing a Nitrogen Charging Unit for Rolls-Royce & Bentley RR363 Accumulators and Recharging Them
Silver Shadow Brake Issues: Your Help Would Be Appreciated! on rollsroyceforums.com
Post Number: 57
|Posted on Sunday, 27 November, 2016 - 04:22 pm: |
Of the six links, I had only stumbled across the last of them - thank you!
In perusing this site, one of the documents I came across had your name on it (explaining how to modify an inexpensive paintball canister to charge the accumulators with nitrogen - plus how to make a test gauge setup). That was great!
Since my local Airgas distributor only does cylinder exchanges and said I would have to go downtown to have it recharged (I live in the suburbs of Orlando and avoid downtown like the plague), I elected instead to purchase a 40lb nitrogen bottle and a 200-2500psi regulator instead. While the regulator was new, the bottle I purchased from a pawn shop. It was fitted with a 100-500psi regulator. My plan is to swap the new regulator onto the bottle for the purpose of charging the accumulators (because I agree with you 100%, e.g. first try to recharge them, and only worry about rebuilding them if they leak). Afterward, I'll reinstall the other regulator, set it to 150psi (about the same as my shop air compressor), and use it to air up tires. I've also built a test gauge and fitted it with a removable high pressure hose-coupling to facilitate storage.
Anyway, the lights in Tootsie's panel do not come on when I drive the car. Never. However, they do come on afterwards if I switch on the ignition key (and within a low-teen number of pumps on one circuit and a mid-20s number on the other). Moreover, in reviewing the service records, the car had the brakes gone through to the tune of a fair bit of money in 2010, which included one new accumulator. Thus, I suspect they're fine and just need a recharge.
Also, now that I've purchased a 2-post lift to facilitate working on the car, this will be one of my first undertakings, hence why I asked. Meanwhile, I wonder if Flying Spares would sell me the primary valve sealing bits alone, e.g. without the accumulator rebuild kit? Reason is I am in contact with Chris on another matter. I guess I'd betetr send him an email immediately because he is preparing a package for me and the added weight would be negligible. By any chance do you have a higher resolution photo, which you can share with me via email of the new seal, and which I may reference when I communicate with him?
John, who is grateful for having encountered you.
Post Number: 2119
|Posted on Monday, 28 November, 2016 - 01:11 am: |
That photo is a cropped bit of the photo of the whole kit from the FS website that I snagged last night. I have never rebuilt using that kit but know others who have. Just based on my own experiences this setup for that primary seal is a major, major improvement over the original. It could easily be made on a lathe though I have no idea of precisely what AS658 standard size that O-ring is, though it's got to be small.
Even if you could order those bits alone you have to disassemble the accumulator in order to install them anyway. You'd have to be insane to go to the trouble to take apart an accumulator and not do a full rebuild on it, which includes renewing the diaphragm while you're there. To get these things apart requires a special pin wrench and a lot of effort. Rebuilding accumulators has been discussed at length here, and many pictures posted.
Post Number: 63
|Posted on Monday, 28 November, 2016 - 03:55 am: |
OK, I didn't understand replacement involved a rebuild of the accumulator. I thought it was merely a cap at the point of access for refilling with nitrogen. Of course, yes, I agree it would be insane to go to the effort of disassembly and not go all the way in refurbishing.
Meanwhile, I have viewed a YouTube video of a (French?) fellow disassembling accumulators (perhaps Citroen but basically the same, I suspect, because the one is built under license). Anyway, the fixtures involved for securely holding it for disassembly are well within our manufacturing capabilities (I happen to also have an interest in a CNC-equipped machine shop) because we manufacture most of our products. This is an example:
That said, I remain of the opinion I may well be able to recharge the accumulators. That would be nice. Any tips?
Post Number: 2319
|Posted on Monday, 28 November, 2016 - 11:52 am: |
If you haven't done so already, I suggest downloading the complete set of Bill Coburn's Tee One Topics from the Technical Libray as accumulator charging etc has been covered by Bill in several issues.
Make sure you download the Index up to Issue 97 as well as this is a great time saver when looking for a relevant issue. Also the Shadow workshop manuals including the high-resolution version of TSD2476 which allows you to substantially enlarge the wiring diagrams to read the fine detail without distortion.