The piston is still in place. There is a small hole in the bottom plate to clear the inner spigot of the piston (see photo). My top and bottom plates are 12mm thick steel and the all-thread is M12. I added 4 equal lengths of plastic conduit over the all-thread which are 20mm longer than a collapsed bag so the bag is extended 20mm when pressurised. Not sure whether wood would be OK, I figure there is about 2000-3000lb force exerted by the bag when pumped up to 280 PSI.

Thanks Crusier for the reply and extra photo. Wow that is a lot of pressure !

Well I made up a jig out of timber to pressurise the bags.



I had to add the extra bracing at the base to support the timber off the bottom nuts as the prototype did split where it was unsupported when I went over 200psi.

I have since added two braces to the top for extra strength. Good use of some Merbau and Meranti off cuts I had lying around I thought. May need to develop it further or make up some spare tops and bottoms to allow for any weakening of the timber down the track.

Good stuff Minimate, you turned that around pretty quickly!

Did the ends of the steel shell on the hydro bag dig into the wooden end plates much at full pressure?

Cruiser the steel didn't dig in at all really, I can see a faint mark from the piston. It was the unsupported timber from the nuts on the steel thread sitting proud that was the issue. Have done 10 flushes now on 3 bags and will need a couple more on this third bag before doing the last bag. Took the pressure up to around 230psi tonight without any problems.
I'm also applying some Aero Space spray 303 and glycerine to the rubbers to keep them supple.

cheers

Removed the front displacer and found this painted number. It aligns with the part number for my car without the 21A prefix. Should there also be a stamped number on the body somewhere?



Edit: found a faint stamp - 317 21A2012L69

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1970 Mk2 Cooper S

That is it.
None of my displacers have the "21A2012" stencilled on them although others here do have it. Displacers all seem to have the number stamped onto the body after the very early (around 1966 vintage).
There is no agreed explanation for the "317" code - they all have different numbers on them.
The "L69" refers to the date 1969 when made.

Thanks bill b. The other side is no where near as clear unfortunately. I can’t be sure, but it appears instead of the L the other side might be an R. They are located on the L for left and R on the right.. not sure though because it’s not been stamped as square on.

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1970 Mk2 Cooper S

The displacers were not "handed".
Did the other side's displacer have stencilled numbers too? And a band of silver on the body and on the end of the hose?

Unfortunately the other displacer is not in as good visual condition. You can see the reminiant of the stencil print and the stamping is not as clear either. I can just make out 317 21A2012 ?69. Silver band on the body and hose. It also was more of a pain to remove the ball end. Lots of silicone spray and banging a open ender on the collar. Finally wedged it off by inserting screw driver between the spacer and ball end collar, and using the persuader.

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1970 Mk2 Cooper S

When replacing the ball pins, I always use an anti-corrosion compound to make removal easy.

What product would you recommend? I’m a lanolin fan but think over time it may dissipate?

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1970 Mk2 Cooper S

Nickel antiseize.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I have been using "Rex-Pak" Antiseize compound Number 4. My father knocked it off from his work in about 1950 and the tin has finally emptied. So I'm not sure what to buy next, now that I have to pay for it.
Go with Drmini's nickel based anti seize. I think nickel is best for stainless to stainless mating surfaces (?).
I thought a copper based anti seize would be adequate for most car applications, but am open to better advice.

Copper antiseize is fine for steel parts except exhaust joints that get real hot. However it should not be used on aluminium I read somewhere.
Some of the hydro pistons are diecast alloy.
I now use the nickel one for everything because a mate gave me a whole tubful.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.