| Author | Message | ||
     Chris Miller Prolific User Username: cjm51213 Post Number: 180 Registered: 5-2013 |
Hi Folks, Since I'm currently elbow deep in accumulator projects, I thought that this would be an excellent time to extract and re-build the accumulators from the '66 cadaver car. There is lots of discussion about the "correct" way, meaning any proven workable way, to seal the nitrogen chamber beyond the seal provided by the check valve. Apparently some enterprising mechanic in years gone by understood that the correct way to seal the chamber was with a STEEL crush ball! I apologize that my pictures are a bit blurry; this is not apparent until I view them on the screen, by which time it is too late to correct. Well, it is never "too late", but it would mean repeating the pictures and these are good enough to show what I want to show.   And the majority of the crushing was to the cap... "Hmmm, still leaks. I know, I'll just apply more torque!" I'm not even sure that they are air-tight any more. They may be completely useless, but I'll charge them up and let them sit for many months to see if they lose nitrogen. I don't think a crack has to be very big to let nitrogen escape...  More destructive torque fall-out from an over-zealous mechanic. This used to be an o-ring...  So, now I need to remove that steel ball and I'm having no luck. I'm looking for ideas. I tired two obvious way to extract them and I have so far been defeated. I know from experience that I can't drill a hole in it, because I tried that when Jim Walters told me that the best practice was to lap the seat of the check valve with a steel ball, which lapping required a stylus with a ball-bearing on the end. I tried to make such a stylus by drilling a hole in a ball bearing. Couldn't even dent it... I tried to file a notch in it to give a chisel purchase to knock it loose. No dice. Any advice? Chris. | ||
| Jim Walters Experienced User Username: jim_walters Post Number: 23 Registered: 1-2014 |
Chris, hit the ball with a spot of weld from a MIG welder. When it cools it will shrink and should fall out. I'm assuming here that you have already removed the circlip, spring, and ball bearing from the inside and tried to tap it out with a thin punch but it didn't move that way. Try that after the MIG weld procedure. To attach a ball bearing to a rod to use as a lapping tool silver solder them together. SRE22493 NAC-05370 www.bristolmotors.com | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 960 Registered: 6-2009 |
Chris, If you know these accumulators to already be completely discharged then the "inside out" method Jim mentions would be the most straightforward. You can drill that ball bearing, but you'll want to use a dremel and a fine diamond bit to do so if you go that route. You'd also want to keep a thin stream of water running over the area being drilled while you're drilling it. Then I generally find some very small screw to thread in to the hole and pull it out or try the smallest "easy-out" bit you can find for broken screws and see if you can get a grip on it that way. If the MIG weld procedure doesn't work, and you don't know if it's safe to separate the sphere halves, you could silver solder a rod on to the stuck ball bearing then use the end of the rod to try to leverage it out. The worst that could happen is that the solder joint would break. Also, I believe it. The set that is on SRH33576 was done "nylon ball inside, steel ball outside" by the nitwit who rebuilt the accumulators the time before I did. How they even held charge is a mystery to me. Brian | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 182 Registered: 5-2013 |
Hi Jim, Brian, Oops... Well, yeah, I forgot to mention an avenue of attack -- open them up and punch it out. It turns out that the accumulator on the '66 cadaver car is a slightly different design and has a slightly larger circumference on the pin side of the ring, and my pin wrench doesn't quite fit. I'm in the process of making a plate with a bigger hole to accommodate the larger diameter of the '66 accumulators, but I just started that yesterday, so it is not done. I asked about other techniques, because it is not a foregone conclusion that I will be able to open these guys, even with the extension plate. I have opened my '72 accumulators while they were pressurized, but pressurized to only 125 PSI. It took the five foot handle on the pin wrench and all of my weight hanging on the end, but I was able to do it. The sphere depressurizes long before it separates, so there is no safety issue. However, I suspect that 125 PSI is going to be close to the limit of internal pressure that I can overcome. If I can open these guys, then the long punch will certainly do the trick. Assuming I can open them... Big "if"... Thanks for the help, Chris. | ||
| Bob uk Unregistered guest Posted From: 94.197.122.79 |
An outfit called Dadco sells accumulators. The sell also charging hoses and regulators. 200 psi to 2600 psi. In their literature they mention thread sealer. Locite 542 hydraulic and pneumatic thread sealer. Also 577 but locite web site is not very good ( to much industry standard trumpet blowing) the facts mam just the facts mam. 542 is £6.15 from bearingboys.! The thread on the charge bit looks different from others I have seen. I believe this is 1/8 BSP parallel. The more I see of the crush ball the less I like it. Options. Solder the hole up. Drill and tap and screw with locite 542 Or just charge cap on it's own. Also I quote "our accumulators are supplied ready charged and will give years of service without further charging or can be supplied uncharged with equipm-ent for charging etc etc) Also only nitrogen is to be used because any oxygen that comes into contact with oil will create an explosive mix. Chris easiest way to check how much charge is left is to connect acc to test rig. Assuming there is no air. Pump up, the gauge if it goes up fast to 2500 then the acc is empty if the gauge goes fast to 1000 then slows the acc is charged. If the gauge goes fast to 100 then that is the nitrogen pressure. As you said it is hard to.separate under pressure. Move the lock ring a bit then stick it in water any bubbles means the acc will discharge if not give the lock ring another tweak. Don't stand to close six foot long scaffold pole will keep you at a safe distance, also place blanket over acc. All hydraulic engineers will tell you that accs are dangerous when doing stuff like this so be very careful. Also eyes and ears. The danger is that the diaphragm may not release the nitrogen from the edges until the ring is quite loose and then go suddenly and cause the halves to separate violently which could be enough to strip the locking ring off the sphere. (Message approved by david_gore) | ||
| David Gore Moderator Username: david_gore Post Number: 1429 Registered: 4-2003 |
Here we go again - NO-ONE and I mean NO-ONE should ever contemplate undoing a gas pressurised container such as an accumulator without fully discharging it first and even then a shield should be used to protect the person disassembling the item. This is why proof testing of a pressure vessel is always done with a liquid as any failure always is in the form of a leak which does not constitute a threat to those in the vicinity in contrast to the explosive decompression of a pressure vessel charged with gas. The difference in stored energy between a pressurised liquid and a pressurised gas is huge as can be seen in the numerous photos of the aftermath of steam locomotive boiler explosions. Personally, I cannot understand why anyone would want to use the extra effort and time involved in opening a pressurised container when it is much easier in the fully discharged condition. You might get away with ignoring this most basic safety procedure several times but you WILL eventually be caught out and receive your nomination for the annual Darwin Awards. | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 183 Registered: 5-2013 |
Huh? What!?! Wait a minute, you mean to tell me that these things are dangerous!?! Good thing I have someone like you to point out how stupid I am. Wow, that was close! (-: | ||
| Chris Browne Prolific User Username: chrisb Post Number: 144 Registered: 2-2010 |
Chris, As a fellow forum member and with the greatest respect, you are in danger of antagonising people with your sarcasm when long-standing and respected contributors are merely concerned for your personal safety. Perhaps you should consider accepting their comments in the spirit they are intended. Kind regards, Chris | ||
| David Gore Moderator Username: david_gore Post Number: 1430 Registered: 4-2003 |
I remind everyone that this Forum operates under the auspices of the Rolls-Royce Owners Club [Australia] and our Club places great responsibility on our Administrator and the Moderators to comply with the Club's standards and ethics as well as promoting safe working practices and the maintenance of personal safety. In the above instance, Chris Miller's advice failed to meet the standards applying to this forum and represented a serious threat to someone who might read this advice in future and act on it whilst not understanding or comprehending the risks involved if something goes wrong. The "streaker's defence" that "it seemed a good idea at the time" is little consolation when someone suffers a disabling or life-threatening injury let alone death as a consequence of avoidable inappropriate actions. It certainly is not accepted as a defence or justification in a Coroner's Inquest or formal accident investigation. I make no apology for what I wrote as it is in accord with the principles underlying this Forum. This Forum is extremely tolerant with members and accepts different points of view on a regular basis without editing which distinguishes it from many other Forums; however, for the reasons detailed above, we cannot condone unsafe, potentially unsafe and/or inappropriate working practices. In this instance and based on my own training and experience, I believe the risks involved are such that my response was warranted. | ||
| Jan Forrest Grand Master Username: got_one Post Number: 615 Registered: 1-2008 |
"Also I quote "our accumulators are supplied ready charged and will give years of service without further charging or can be supplied uncharged with equipment for charging etc etc) Also only nitrogen is to be used because any oxygen that comes into contact with oil will create an explosive mix." Eh? Atmospheric oxygen is always in contact with the fluid at the surface inside the reservoirs! When was the last time that this 'explosive mix' so much as ignited, much less exploded? | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 184 Registered: 5-2013 |
Hi David, No apology necessary; we're all big boys here. You commented on my post; I commented on yours. We can bump into each other without getting hurt. > In the above instance, Chris Miller's advice ... I will point out that you justified your immoderate "warning" as mitigation of my advice. I advised nothing. The advice was given to me, not by me and I am enormously thankful for it. I hope to continue to get such helpful advice in the future, in spite of such dire and, in my view unnecessary, warnings. For my part, I reported what I have done, probably will do, and some observations I have made. None of it constituted advice. Chris. | ||
| Jim Walters Experienced User Username: jim_walters Post Number: 24 Registered: 1-2014 |
Let me add that I assumed the sphere was already depressurized and split when I responded to your post Chris. I could see the circumstance where a steel ball could be so tight that it would not come loose using a hammer and a small pin punch from the inside out. I only suggested you MIG weld a spot on the ball bearing assuming it was depressurized. I WOULD NOT MIG weld a spot on a ball bearing stuck in a sphere like that without being absolutely certain it was depressurized. It is entirely possible that the pressure behind the ball bearing could be anything up to 1000psi. There exists the very real possibility of the ball shooting out like a bullet when it shrinks and comes loose potentially killing anyone in the vicinity. I absolutely DO NOT recommend using welding or heat of any kind on a pressurized sphere. Mig welding tight bearing races is a common way of removing them from their housings. They will shrink and drop out when cool. SRE22493 NAC-05370 www.bristolmotors.com | ||
| Chris Miller Prolific User Username: cjm51213 Post Number: 186 Registered: 5-2013 |
Hi Jim, > I WOULD NOT MIG weld a spot on a ball bearing > stuck in a sphere like that without being > absolutely certain it was depressurized. No, of course not. There is no guarantee that the check valve is intact, and it is entirely possible that the only thing holding 1,000 PSI of nitrogen is that damn steel pellet. Wouldn't that be a surprise? Have no fear; playing with this stuff is an engineering discipline. You must keep your wits about you, and I do. Your advice was written with a competent mechanic in mind, and I am a competent mechanic, so there is zero negligence on your part. Determining if the spheres are depressurized is dead simple -- insert a probe into the "salt and pepper shaker" holes and see if the diaphragm is inflated. If the pressure is low enough to permit spinning the containment ring, then that is low risk; if the pressure will not permit spinning the containment ring, then probably the only solution is to puncture the diaphragm with a hypodermic needle, and maybe that is the best thing to do in any case. Thanks for the help, Chris. | ||
| Bob uk Unregistered guest Posted From: 94.197.122.88 |
Chris it is obvious you have not understood the manual because you say things like I thought the master cylinder was for feel only. Or I don't know what the pressure is in a sphere, when if you read the manual and understand it you will find it. You don't understand how bolts work you don't understand how much 1 ton of pressure per inch means. You are not competent to repair safety related system. If you worked like that in a garage the boss would sack you. Until you learn that makers data is law you will be a liability to yourself.and those nearby It is like you think you know better than the bloke who designed the car. The charge cap is 5/8 UNF not BSP. (Message approved by david_gore) |
