| Author | Message | ||
     Chris Miller Yet to post message Username: cjm51213 Post Number: 1 Registered: 5-2013 |
Hi Folks, I am renewing the hydraulic system on my '72 (SRH 13161) I have removed and am rebuilding the accumulators and valves. Apparently there is an adapter necessary for re-pressurizing -- RH7808. I am unable to find one of these and that includes the American national warehouses, the Crewes warehouse, and the cooperative dealer inventory. I know my local shop probably has one and will recharge my spheres, but I have this silly self-sufficiency compulsion. Does anybody have a secret stash of them? Chris. | ||
| Geoff Wootton Prolific User Username: dounraey Post Number: 196 Registered: 5-2012 |
Hi Chris I can't help with RH7808 but I recharged my accumulators by using a Watts A762 3/8 1/8 coupler and a standard schrader valve. The Watts coupler has the correct thread for accumulator and is rated at 1000 psi. I took the coupler down to a local hydraulic hose company and they fitted the schrader valve. This will then fit any charging station. Worked great. I bought the Watts connector from Lowes. When you get the shop to pressurise the accumulator tell them to expect a loud "crack" as the diaphragm flips. Will save you having to pay their laundry bill. Geoff | ||
| Chris Miller New User Username: cjm51213 Post Number: 2 Registered: 5-2013 |
Hi Geoff, Thanks very much. I suspected that it was probably a simple conversion problem, but never having seen one of these things, I didn't know for sure. Chris. | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1509 Registered: 4-2003 |
Chris I have been recharging accumulators on and off vehicles for over 30 years. The main expense has been renting cylinders of dry nitrogen. I am intrigued with the shrader valve? Where does that go? The other expense is the regulator which can be very expensive but perhaps you pipe the stuff directly from the cylinder to the accumulator? That would explain the possible laundry problem. Frankly I am having that problem at the moment thinking about not using a regulator if that is the case. As to the adapter I simply had one made up to fit normal high pressure gas hoses. For years I have 're-gassed' these things when they get down to 10 'pumps' or so as the diaphragms are usually still intact with plenty of life in them. If on removing the charging cap there is any sign of brake fluid, it is pointless charging and simply blowing the gas back through the system. Charging the rear accumulator on the Shadow 1 cars can be an embuggerance because the charging valve is right above a suspension arm. A little patience and loosening or removing the accumulator valve mounting bolts and fiddling usually overcomes that problem. Lastly, the charging valve in the base of the accumulator has been greatly improved upon by a couple of local entrepreneurs who have made up spigotted discs with a very small 'O' ring which drops down the charging hole. So far I have had not one of these leak. Geoff - as to the intestinal trauma when charging, the Factory has always advocated turning the diaphragm 'inside out' with the thick central 'knob' located against the accumulator inlet. This area is almost always the area that the diaphragms fail so a little caution here may save work later. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 414 Registered: 6-2009 |
Bill, I'm here to second your statement, "the diaphragms are usually still intact with plenty of life in them." The ones that I've removed when rebuilding the accumulators I've done have been in almost perfect shape. The only observable difference from new is that some very tiny bumps on the part of the diaphragm that can come in contact with tiny holes that make up the fluid port. The diaphragms I've dealt with are so thick at this area, significantly more so than where they flex near to their circumference, that I can't imagine a rupture every occurring in that spot. The folks at Flying Spares definitely came up with a greatly improved valve setup on the charging port as well. The friend I had charge up the three accumulators I've worked on recently does this kind of work frequently, but for accumulators used in aviation. Apparently the loud crack doesn't frighten these folks, since I hadn't "pre-domed" the diaphragms. Brian | ||
| Geoff Wootton Prolific User Username: dounraey Post Number: 197 Registered: 5-2012 |
Bill You have just solved a mystery for me. I wondered why no-one had documented the loud "crack" when charging a reconditioned accumulator. I thought I may have made a mistake and obviously did, in not turning the diaphragm inside out. It looks like I "got away with it" as I have had no problem with holding the charge. I get 80 foot pedal pumps for system 1 and 120 for system 2 and the accumulators have been on the car for a year now (although I am currently fixing an RR363 leak between the sphere and ACV). In answer to your question about the schrader valve, when I was seeking a company for the recharge, all the charging stations required a standard schrader valve. My solution is best explained in the photo:  The fitting on the right of the photo is the Watts A-762 adapter and the fitting on the left is the schrader valve screwed into the A-762 adapter. The A-762 screws onto the accumulator sphere and the schrader valve end fits the line from the charging station. There is an O ring on the inside of the Watts adapter to form a good seal with the accumulator valve. Geoff. | ||
| Chris Miller New User Username: cjm51213 Post Number: 3 Registered: 5-2013 |
Hi Folks, With the explanation of Geoff's improvised RH 7808, the problem for me now is the nitrogen charge. The nitrogen supply companies fill trucks and tanks and no tanks as small as an accumulator. I find no hydraulic service and supply companies that re-charge accumulators in Sacramento. Where do I look? What google search string will reveal the local options? Chris. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 417 Registered: 6-2009 |
Chris, If you have any friends who work at any aviation repair service (or connections to same) talk to them. They're constantly charging accumulators with nitrogen. Another place to check is your local welding supply services. See this document on making your own recharging setup. I "inherited" the set that's shown from Jean-Michel when he stopped working on his own cars. It works like a charm, and I had a friend who's an aviation mechanic get the bottle charged with nitrogen when I last needed that. It's easy to source PTFE spheres to use to seal the charge port. If you need me to do so I'll look up where I ordered mine from. Brian P.S. to Geoff: Remarkable how similar this setup is to yours, isn't it? The only difference is it uses a quick connect instead of a schrader valve | ||
| Geoff Wootton Prolific User Username: dounraey Post Number: 198 Registered: 5-2012 |
Brian Fantastic document!!! I didn't realise you had it. Thanks for putting it up. Geoff. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 418 Registered: 6-2009 |
Geoff, I had forgotten that I had that document until I saw your picture posted. On a closely related note, here's one documenting how to build your own hydraulic pressure gauge. I shall simply say that my personal electronic library of technical documents has long ago outstripped the ability of the "wetware" to quickly and efficiently search the index. [A fancy way of saying my memory's not what it once was.] Brian | ||
| Geoff Wootton Prolific User Username: dounraey Post Number: 199 Registered: 5-2012 |
Thanks again Brian. Chris - I found a local company here in Las Vegas by using a search string in google like "Nitogen Recharge Las Vegas". It pulled up a whole load of custom car forums and I went through them all arduously. I eventually found a transmission company that re-charged my accumulators for 10 bucks each. I think they carried the recharge kit for nitrogen filled suspension dampers. The firms are out there - just hard tracking them down. Geoff. | ||
| Jan Forrest Grand Master Username: got_one Post Number: 479 Registered: 1-2008 |
Here in Blighty a lot of tyre fitters have nitrogen tanks for filling tyres. How much pressure they can supply I couldn't say although I reckon it might be severely limited by the pressure gauges used. As I've already got a 20 litre scuba tank, hoses and adaptors I can recharge my accumulators several times to 1,000 psi with dry breathing air. I used to use it to recharge my PCP air rifles to over 2,000 psi so it's well capable for the job. I can't see the 19% of O2 making much difference from pure nitrogen as the other side of the diaphragm will always be in contact with O2 dissolved in the hydraulic fluid anyway. | ||
| Kelly Opfar Experienced User Username: kelly_opfar Post Number: 16 Registered: 7-2004 |
Here's the wrench I made for the job.  |
