Freeing an Airsporter trigger block

[robs5230]

Against my better judgement I've been talked into looking at an old airsporter, which is not cocking. Lever only moves a fraction then stays solid.
Guessing the piston head has seized in the cylinder.

Last time I worked on an airsporter was over 30 years ago and they've been a bit of a distant memory.

After removing the cocking linkage, the trigger block is absolutely seized

So far I've used penetrating oil and a mallet on a bar through the hole in the block, and nothing is moving at all.
I'm reluctant to use heat due to the painted finish on the trigger block.

Guessing there's the issue with corrosion of sorts, between dis similar metals with the block being alloy and the cylinder steel.

Anyone have any ideas / suggestions?

Thanks in advance. Rob

[T 20]

If you can't use heat I wonder if freezing it would help, Rob ?

I normally soak them in penetrating oil and then batter them with a rubber mallet to shock them.





All the best Mick

[robs5230]

If you can't use heat I wonder if freezing it would help, Rob ?

I normally soak them in penetrating oil and then batter them with a rubber mallet to shock them.





All the best Mick

Hi Mick.

I really must learn to say no when folk try to talk me into things.

I'd have to lop the barrel off to get it in the freezer, so not really an option.

Its had 24 hours soaking in plus gas and I've scared the bloody life out of it with a mallet. It refuses to budge.

If it were mine, I'd get it apart somehow and if necessary refinish the alloy block, but I'm loathe to go to those lengths on something that isn't mine.

Just had a chat with the owner and its of sentimental value, so it may just get put away for another 30 years or so.

Rob

[rancidtom]

Try a can of "pipe freezer", make sure you only get it on the alli action block to shrink it, but alli shrinks much more than steel for a given temp drop so even though the cylinder will cool the grip on the block thread should relax.
If you want to use heat you will only need boiling water to free any thread locking agent or paint in the thread. Quite easy to stick the trigger block end in a pan on the stove for 10 mins, this may free it and it shouldn't take the paint off the block, however it will soften it so be careful if you have to clamp it while hot (although the cross hole with a bar is the usual method).

[T 20]

Try a can of "pipe freezer", make sure you only get it on the alli action block to shrink it, but alli shrinks much more than steel for a given temp drop so even though the cylinder will cool the grip on the block thread should relax.
If you want to use heat you will only need boiling water to free any thread locking agent or paint in the thread. Quite easy to stick the trigger block end in a pan on the stove for 10 mins, this may free it and it shouldn't take the paint off the block, however it will soften it so be careful if you have to clamp it while hot (although the cross hole with a bar is the usual method).

Ah, there's part of the problem, Tom, the male threads on the back block are steel not ally.
The steel male threaded piece is located on the ally block by teeth and is held on by a hollow bolt, if you fit one Airsporter back block to another tube you have to loosen the bolt and index the two pieces together before fully tightening the bolt --- all good fun.

I like the boiling idea, boiling in oil would be good.




All the best Mick

[rancidtom]

Ah, there's part of the problem, Tom, the male threads on the back block are steel not ally.
The steel male threaded piece is located on the ally block by teeth and is held on by a hollow bolt, if you fit one Airsporter back block to another tube you have to loosen the bolt and index the two pieces together before fully tightening the bolt --- all good fun.

I like the boiling idea, boiling in oil would be good.




All the best Mick

Yes, you're right, I forgot, even having done one quite recently! Now, where's me specs....

[T 20]

Hi Mick.

I really must learn to say no when folk try to talk me into things.

I'd have to lop the barrel off to get it in the freezer, so not really an option.

Its had 24 hours soaking in plus gas and I've scared the bloody life out of it with a mallet. It refuses to budge.

If it were mine, I'd get it apart somehow and if necessary refinish the alloy block, but I'm loathe to go to those lengths on something that isn't mine.

Just had a chat with the owner and its of sentimental value, so it may just get put away for another 30 years or so.

Rob

You can buy an aerosol can now that'll freeze the component when sprayed on, Rob, my hydraulic pipe man uses it to free pipes off.


I've had to resort to wrapping the timing belt off a car round the tap area of the cylinder to hold it in a vice before now with a pin through the back block and a piece of pipe as a lever.
On this one I indexed the male threads one tooth forwards on the back block and the trigger housing was still plenty tight enough on reassembly.


All the best Mick

[rancidtom]

You can buy an aerosol can now that'll freeze the component when sprayed on, Rob, my hydraulic pipe man uses it to free pipes off.


I've had to resort to wrapping the timing belt off a car round the tap area of the cylinder to hold it in a vice before now with a pin through the back block and a piece of pipe as a lever.
On this one I indexed the male threads one tooth forwards on the back block and the trigger housing was still plenty tight enough on reassembly.


All the best Mick

If you remove the tap you can use a brass (not steel) bar through the cross hole to hold the cylinder...

[T 20]

If you remove the tap you can use a brass (not steel) bar through the cross hole to hold the cylinder...

I once got a bollocking on here for saying that, Tom, so I don't say it now --- I just do it and keep quiet about it.