Rebuilding an Ashlocker - getting the piston apart?

[elbekko]

I'm currently rebuilding an Ashlocker to go into the front of my P38. This is a unit @Escaperan for a few years, and then was recovered from his P38 that was in the workshop fire.

Most internals seem fine, but of course the seals need to be replaced. Ordered a seal kit from Ashcroft a few years back, which is 3 o-rings (and should be 4, apparently).

Now for the problem: the o-rings around the piston don't seal anymore, and thus I can't get the piston out of its housing with air pressure. The piston is some sort of brass, so non-magnetic. Hammering doesn't work, soaking in penetrating oil doesn't work.

Any bright ideas?

Also, had to buy new M5 countersunk bolts for the piston retaining ring, as the old ones were made of chinesium and all needed to be drilled out. But it almost looks like the old bolts have been machined down to be flush? Will this actually be a problem?

[Stellaghost]

6 minutes ago, elbekko said:

I'm currently rebuilding an Ashlocker to go into the front of my P38. This is a unit @Escaperan for a few years, and then was recovered from his P38 that was in the workshop fire.

Most internals seem fine, but of course the seals need to be replaced. Ordered a seal kit from Ashcroft a few years back, which is 3 o-rings (and should be 4, apparently).

Now for the problem: the o-rings around the piston don't seal anymore, and thus I can't get the piston out of its housing with air pressure. The piston is some sort of brass, so non-magnetic. Hammering doesn't work, soaking in penetrating oil doesn't work.

Any bright ideas?

 

 

Can you get some thick oil in there, I would try some oil in spread it around and then try as maximum air pressure as you can get to then push brass out, my thought process is it would similar to squirting oil into a piston bore which would give you raised compression figures as it makes the compressed air fight harder to bypass the rings. A similar approach might work, the oil might encourage a bit more sealing and allow air to work on piston regards Stephen

[elbekko]

I tried that with penetrating oil, but I guess that's way too thin.

Will give it another go with some motor oil.

[Stellaghost]

Just now, elbekko said:

I tried that with penetrating oil, but I guess that's way too thin.

Will give it another go with some motor oil.

I would say too thin the whole idea of penetrating oil is to capillary into tight areas, not much good at sealing but plenty good at creeping... lol regards Stephen

[elbekko]

Tried with some 10W40 - better but still not budging, even with some hammering.

Also not helping that the o-ring for the air line isn't supplied, and the smallest one in our kit is a bit too big.

[elbekko]

And another thing not helping is that you can't really get to the back of the piston - all there is, is this tiny air hole.

Oil doesn't really want to flow in there 😕

[Stellaghost]

1 minute ago, elbekko said:

Tried with some 10W40 - better but still not budging, even with some hammering.

Also not helping that the o-ring for the air line isn't supplied, and the smallest one in our kit is a bit too big.

Ok 

I'm not familiar with the set up however with a piece of hard wood can you tap the brass home, it may not move because it is cocked over due to seals being damaged and therefore jammed, tap it gently home and see if it moves, the other thing I would try and do is try and get it to spin in the housing, again tapping with some wood or try and use a couple of valve grinding suction cups to encourage movement. If all else fails degrease a couple of areas and araldite a couple of rods on to allow you to pull and twist, glue can be cleaned off easily enough later regards Stephen

[Stellaghost]

6 minutes ago, elbekko said:

And another thing not helping is that you can't really get to the back of the piston - all there is, is this tiny air hole.

Oil doesn't really want to flow in there 😕

You could try connecting a grease gun onto the air pipe and pump grease in to try and hydraulic out the piston regards Stephen

[Bowie69]

Drill tap and stick a bolt in?

 

[elbekko]

7 minutes ago, Bowie69 said:

Drill tap and stick a bolt in?

 

I don't have a new one...

 

40 minutes ago, Stellaghost said:

Ok 

I'm not familiar with the set up however with a piece of hard wood can you tap the brass home, it may not move because it is cocked over due to seals being damaged and therefore jammed, tap it gently home and see if it moves, the other thing I would try and do is try and get it to spin in the housing, again tapping with some wood or try and use a couple of valve grinding suction cups to encourage movement. If all else fails degrease a couple of areas and araldite a couple of rods on to allow you to pull and twist, glue can be cleaned off easily enough later regards Stephen

I've tried tapping it home both gently and less than gently. I can see a tiny bit of movement when putting pressure on, but it doesn't come out further. Tried tapping it all around with pressure on, no luck.

I left it soaking in some 10W40 now, maybe it'll seep past the seals by tomorrow.

 

[Wytze]

Can you tap that little hole to take a grease gun nippel?  I use a grease gun for calipers when the pistons are really stuck.  It allways works

[Stellaghost]

Have you measured the steel bore, make sure its not oval and slightly distorted out of shape, would not take a lot as the tolerances are fine. Only asking as I do not know how much heat the locker was exposed to in the fire regards Stephen

[elbekko]

5 hours ago, Wytze said:

Can you tap that little hole to take a grease gun nippel?  I use a grease gun for calipers when the pistons are really stuck.  It allways works

Can, yes. But that would destroy the piston. So I'd rather not 😕

5 hours ago, Stellaghost said:

Have you measured the steel bore, make sure its not oval and slightly distorted out of shape, would not take a lot as the tolerances are fine. Only asking as I do not know how much heat the locker was exposed to in the fire regards Stephen

Haven't checked, but good call, will try to measure tomorrow. Fire got pretty toasty, but so far gearbox internals and such from the fire have been fine - and the rest of the diff seems smooth enough. But could always be.

[muddy]

could you get a chunk of 20mm ish plate, drill and tap for a grease nipple and bolt that over the hole? I would also waft a plumbers blowtorch around the outer circumference as presser is applied, that way if the brass slug misses you you still get a burning shower or hot grease 😃 

[elbekko]

Measured with calipers, seems to be within ~0.01mm, so that's fine.

Chucked it in the freezer now, hoping the brass will contract more than the steel.

12 hours ago, muddy said:

could you get a chunk of 20mm ish plate, drill and tap for a grease nipple and bolt that over the hole? I would also waft a plumbers blowtorch around the outer circumference as presser is applied, that way if the brass slug misses you you still get a burning shower or hot grease 😃 

Not a bad idea, don't have much thick plate kicking around though. And probably no tap for whatever imperial thread a grease fitting has.

[muddy]

32 minutes ago, elbekko said:

Measured with calipers, seems to be within ~0.01mm, so that's fine.

Chucked it in the freezer now, hoping the brass will contract more than the steel.

Not a bad idea, don't have much thick plate kicking around though. And probably no tap for whatever imperial thread a grease fitting has.

A welder can solve both issues should to be needed.

[elbekko]

Great success!

Freezer helped a bit, but the big breakthrough was finding a small enough punch to give the piston a good knock through the air hole. After that it was a lot of oil, and a lot of rocking while applying pressure to the back.

[Nonimouse]

beaten to it