Stuck Tich piston

[Mark Salzedo 1Participant @marksalzedo1]

Hi, A few months ago I bought a pretty much complete but seized 3 1/2″ Gauge Tich chassis. Recently I have found the time to take it apart – the cylinders have been taken off the chassis. The cylinder-less rolling chassis now rolls relatively freely. Also, the piston in one cylinder now moves freely. The other piston though is still seized. I have loosened the rear cylinder cover just in case there was any binding and used WD40 and penetrating oil in the cylinder (back and front) in the last few days but to no avail.

Any suggestions on how to free the piston will be appreciated.

Many thanks.

[MichaelRParticipant @michaelr]

You could try warming up the cylinder with a hot air gun (Paint stripper gun) or put the cylinder in the kitchen oven, when really warm dunk it in cold water the shock of cooling fast may just loosen the piston.

Other than that just keep persevering with the release oil.

MichaelR

[noel shelleyParticipant @noelshelley55608]

Remove the front cylinder cover if not already done, use a short length dowel of about the bore size or suitable piece of wood and  gently drive the piston back with a small hammer. Has it got an iron piston ring or an O ring ? If an O ring it may try to drag the ring between the piston and bore causing the whole thing to jamb as soon as it moves, this will require more care and very slow progress.  Noel.

[Mark Salzedo 1Participant @marksalzedo1]

Thank you for the advice. It’s a gunmetal cylinder assembly with an O ring which is now perishing.

[Nigel Graham 2Participant @nigelgraham2]

Using the technique Noel suggests should work but you may need tap the piston back and forth a little at a time, not just in one direction, to free it enough to move in one direction.

Obviously don’t hit the piston-rod. Use a smaller dowel on that side, and acting on each diametral “side” of the piston alternately.

Replace both O-rings, as that on the free side is likely to be badly ageing too.

[Nigel Graham 2]

On Nigel Graham 2 Said:

Using the technique Noel suggests should work but you may need tap the piston back and forth a little at a time, not just in one direction, to free it enough to move in one direction.

Obviously don’t hit the piston-rod. Use a smaller dowel on that side, and acting on each diametral “side” of the piston alternately.

Replace both O-rings, as that on the free side is likely to be badly ageing too.

Use a piece of tube so you are still hitting central

[Mark Salzedo 1Participant @marksalzedo1]

Much obliged for all the advice. Really good suggestions which I will probably have to act on if the penetrating oil doesn’t free up the piston. I don’t have much hope that it will!

[BazParticipant @baz89810]

If the o ring is perishing I doubt that WD40 or heating the cylinder will do any good.

[noel shelleyParticipant @noelshelley55608]

Sitting here mulling ! What is the piston made of, iron ? Is it the piston that has seized or is it the O ring that’s causing the problem ? Other thoughts, If there is sufficient bore clearance a thin strip of ALI drinks can (or shim brass) down beside the piston may get the O ring to move.  A fluid that will reduce the O ring to soup, Acetone or cellulose paint thinner ? With both cylinder covers off gentle violence should get it free, bronze has a high rate of expansion so heat will help, 2 – 300c drop the lump in a deep fat frier, or a pan of cooking oil on the stove – DO NOT use engine oil. There are small glaze breakers/ bore hones available quite cheaply that will clean up any small marks on the bore.Good luck Noel.

[duncan webster 1Participant @duncanwebster1]

If it’s got an oring seal it’s probably gunmetal

[noel shelleyParticipant @noelshelley55608]

Gunmetal block and a gunmetal piston ? Noel.

[duncan webster 1Participant @duncanwebster1]

That’s what original design called for I think. Lots of people successfully use ally piston in gunmetal cylinder to save reciprocating weight.

[bernard towersParticipant @bernardtowers37738]

Like that expression Noel “gentle violence”

[Mark Salzedo 1Participant @marksalzedo1]

Thanks for the suggestions. Yes, it’s a gunmetal block and piston with an O ring.

[Mark Salzedo 1Participant @marksalzedo1]

I don’t want to force anything just at the moment but I will probably have to at some point! Some time ago, I recollect reading about immersing the cylinder assembly and piston in petrol or paraffin to free a stuck piston. Has anyone else come across this possible solution? Thanks.

[duncan webster 1Participant @duncanwebster1]

A mix of automatic transmission fluid and Acetone was an old recipe, but unless you already have the ingredients could be expensive and difficult to procure. Also have to think about the effect of Acetone on the remains of the oring. If it made it swell you’d be worse off. Many moons ago we used a bucket of diesel. Better lubricant then petrol and much less volatile

[noel shelleyParticipant @noelshelley55608]

Mark, I take it the rear cylinder is off, it’s not stuck on the packing gland ? Bronze piston and cylinder, what is holding it ? Just the O ring ?  Noel.

[Mark Salzedo 1Participant @marksalzedo1]

Noel – Yes, that’s correct. The rear cylinder cover is detached from the cylinder assembly….

[pgk pgkParticipant @pgkpgk17461]

No-one has mentioned an ultrasonic bath. Is that inappropriate here? Borrowing the use may be possible or indeed they are handy and not that expensive these days.

[Andrew Moyes 1Participant @andrewmoyes1]

You could make a temporary front cylinder cover and tap the centre for a jacking screw.  Some discretion will be needed as to how much torque to apply so that no damage is caused to the cylinder cover fixings.  I think this will be more controlled and gentle than hammering.  Also the jacking force can be applied and left overnight or longer in conjunction with penetrating fluid.

[SillyOldDufferModerator @sillyoldduffer]

Too late to help, but I wandered the web last night looking for chemicals that would dissolve an O-ring whilst not attacking metal.   Disaster!  O-rings are much tougher than I expected, and the chemicals already suggested cause them to swell, not disintegrate.   I fear the liquids recommended have made things worse!

Also seems that techniques that work well on metal are unlikely to work on an O-ring.   They resist chemicals, and them being elastic means heating and cooling won’t un-seize the joint.  They’re also remarkably tough – hard to break once fitted.

My thoughts:

1. Hammering – driving the piston out with a series of moderate sharp shocks.  Maybe adapt a impact driver.  Risks damaging the cylinder.
2. Pushing the piston out between the jaws of a big vice, hefty Arbour Press, or a Hydraulic Press. Risks damaging the cylinder.
3. Drill and bore out the piston until the O-ring groove is exposed from the inside.   Doesn’t risk damaging the cylinder, but a new piston has to be made.

Nasty!

Dave

[Michael GilliganParticipant @michaelgilligan61133]

Liquid Nitrogen would render the O-ring brittle, and it should shatter on impact.

… availability being the difficult bit.

MichaelG.

.

Edit: __ classic demo.

https://youtu.be/-gvxOBfHiE4?feature=shared

[noel shelleyParticipant @noelshelley55608]

There are numerous materials used in the making of O rings that resist various fluids,  silcone was favoured for piston ring as it stood the heat. Let us all be clear, is the problem that it is the O ring that is the reason the piston won’t move ? OR is it the piston it’s self that is seized ?

Does the OP have a lathe and could make a new piston if need be ? Remove the valve gear, valve rod, slide valve etc and heat the piston with a blow lamp. Have the cylinder well held in a fixture that will allow you to hit the piston with the dowel rod mentioned earlier, wrap the cylinder block in a damp/wet rag,eventually the O ring will be softened, or burn out. Once it starts to fail it will go in a rush. No idea where you are, in the UK ? I have a press and it should be an easy job. Noel.

 

[Dave HalfordParticipant @davehalford22513]

If the O ring has perished it will have formed a sticky mess and glued the piston in.

If the piston seized from lack of oil or solidified steam oil from years of storage, a foreign body or flake of solder or rubbish  from the steam piping or the piston has collapsed etc, I can only see two options.

1. Strip the valve chest and con rod off and heat the cylinder to dull red and tap out, the O ring should melt as should any old steam oil. Once it’s moving it should be much easier. Stinks to high heaven tho.

2. Just drill the piston centre out past the dimension of the bottom of O ring slot as the drill breaks through into the ring space it should catch and half the piston should break free and rotate. The problem with that is the bore may take a hit.

[John PurdyParticipant @johnpurdy78347]

Be  careful heating the cylinder to high heat if the O ring is of an unknown material. If it is a material that contains any fluorine compounds the fumes could/will be nasty, even fatal.

John

[Author]

Posts