Chemistry help please

[leetrenchard]

Take the acetone out and light the vapours at the transfer port.

Point in safe direction😁

[silva]

Have you tried the gentle application of a bit of heat !

[guitardan]

I put my Airsporter in boiling water, ten minutes, out it came..

[WebleyWombler]

Well the soaking scorpion and Meteor have both come out with a little persuasion but only after putting a little solvent in each piston chamber and standing in a galvanised bucket of boiling water for 10 minutes. before the additional solvent , the boiling water alone wouldn't shift them with the amount of force I wanted to use.
I'll try the other methods on the other 2 scorpions and the meteor that's left for interests sake (and I'm lazy so always want to find an easier way)

[pothunter]

I had a thought after I previously posted, and realise that I got tunnel vision about the seal and O ring becoming fused.

My original degree is Organic Chemistry and, having thought about it, my view is that an essentially inert amine type polymer, ie Nylon seal, or a Butyl compound, O ring, couldn't possible weld to a steel tube, (the butyl would dry out and become brittle).

To throw a variable in, it might be not the seal or the o ring, it could be the amounts of mineral oils and grease that have previously been applied which have dried out and formed a hard semi cross linked gum/polymer as the volatile elements have evaporated.

If you have more of these to do petrol, xylene, plus gas or any dino fuel type liquid might be more successful at bringing the hardened gum back into solution and make freeing easier.

Acetone and Isopropyl may have moved it in this case, but my thoughts are that is is more of a creeping liquid that has disrupted the mechanical bond, rather than any solvent effect.

[edbear2]

I had a thought after I previously posted, and realise that I got tunnel vision about the seal and O ring becoming fused.

My original degree is Organic Chemistry and, having thought about it, my view is that an essentially inert amine type polymer, ie Nylon seal, or a Butyl compound, O ring, couldn't possible weld to a steel tube, (the butyl would dry out and become brittle).

To throw a variable in, it might be not the seal or the o ring, it could be the amounts of mineral oils and grease that have previously been applied which have dried out and formed a hard semi cross linked gum/polymer as the volatile elements have evaporated.

If you have more of these to do petrol, xylene, plus gas or any dino fuel type liquid might be more successful at bringing the hardened gum back into solution and make freeing easier.

Acetone and Isopropyl may have moved it in this case, but my thoughts are that is is more of a creeping liquid that has disrupted the mechanical bond, rather than any solvent effect.

It's not the washer or o ring but the cacky spongy buffer washer behind the piston head, this degrades and expands, I don't know what it is made of as am a welder, but a plasticky slightly spongy stuff a bit like a shock absorber piston bump stop is the best I can do

If you get one and place it in Acetone it goes all slippery when handled, rather than totally dissolve, but again that's all I can add except the Acetone from the cocking slot end does work for me.

ATB, Ed

[PhatMan]

WebleyWombler,

Try a mix of acetone & penetrating oil - 50:50.

Have fun & a good Bank Holiday

Best regards

Russ

[WebleyWombler]

Ok, got them all apart by trying all the methods and suggestions and have come to the conclusion that paint thinners or acetone dripped in from the spring end, left to soak for a couple of hours, coupled with later applied heat via heat gun is the best way to free the pistons off.

both the Meteors have been rebuilt.
the first needed Scotchbright treatment in the aircylinder to shift the final traces of crud and was then treated to a complete Protek refurb kit. The spring had about 30mm pre load. 1 shot through the Chrono with marksman pellets = 7.6FPE. 20 shots into the backstop and it does a very consistent 8.3FPE and shoots well

The Second was a little bit different. As stripped, it had a gold coloured aftermarket spring in with about 25mm preload. it appeared in good condition so was left. Piston 'O' ring was one out of a Lidl kit , buffer washer was 2 x 3mm leather washers cut from an old belt. breech washer was a home made one cast from PT85 casting rubber left to cure for 36 hours. It's a bit soft at shore 85 and i don't know how long it will last but is worth a try.
Before assembly the piston and air cylinder bore was given a liberal spray of the of the cheap graphite lubricant bought from Lidl. this was left for 2 hours for the carrier to evaporate before assembly.
First shot, it dieseled. very badly, scared the crap out of me . 20 shots into the backstop later and back to the chrono. Same 14.2 gr. Marksman Pellets. A reasonably consistent 9.5-9.7FPE and shooting very sweetly with no perceived vibration or bounce. the cheap bits seem to have worked but I'll have to use it more to determine longevity.

The 3 Scorpions can wait for now but I'm going to treat them to different piston heads and see what results I get.

[jedburgh]

A very useful thread .