Seized whisker pole piston - blowtorch?

[stuartwineberg]

Firstly I have seen another excellent thread with all the usual ideas Which I am trying - boiling water, phosphoric acid descaler, plus gas. this is an ancient alloy piston hank with a steel pin seized solid. I am working my way through the options and just wanted to ask about the nuclear option. Can you use a blowtorch on an alloy fitting to expand it or will it melt? If I do go this route is the idea to welly it with a hammer while it is still hot?

 

[Refueler]

Not something I would do ..... in fact I would not have used Phossy acid either .....

But heat and gentle persuasion .... takes time .... if there is any slack in the pin key slot ... then trying to torque it back and forth that little bit can help to break the bi-metal corrosion that's occurred.

If you have a container - you could create a strong descaling solution (acetic acid based) as used for kettles etc. and stand the end in it ..... leave it for a day .. try again ... if not back in the solution .... keep trying ...

 

[stuartwineberg]

Not something I would do ..... in fact I would not have used Phossy acid either .....

But heat and gentle persuasion .... takes time .... if there is any slack in the pin key slot ... then trying to torque it back and forth that little bit can help to break the bi-metal corrosion that's occurred.

If you have a container - you could create a strong descaling solution (acetic acid based) as used for kettles etc. and stand the end in it ..... leave it for a day .. try again ... if not back in the solution .... keep trying ...

Thanks. The reference to phossy acid is that I used descaler and the label said that this is what it contained. There
is no movement at all at the moment

 

[Praxinoscope]

Like Refueler would not recomend using the 'blue spanner', soaking in a solution of commercial kettle de-scaler for a few hours may help, I have also used a hot oil bath, (SWMBO was not too pleased that I use one of her saucepans for heating the oil) but it did eventually help to free the bits off.

 

[Refueler]

Thanks. The reference to phossy acid is that I used descaler and the label said that this is what it contained. There
is no movement at all at the moment

Phossy Acid ... I used to carry thousands of tons of it on ships ..... so it has a certain understanding for me !!

In descaler as you probably bought - its highly diluted. Its actually a very good stain remover from paintwork .... but it dulls the gloss and needs polishing after.

 

[dansaskip]

Vinegar is worth a try worked for me in the past and is fairly cheap. Give it a good soak.

 

[LONG_KEELER]

Left soaking in diesel for a few days might work.

I have had success separating spreader end inserts this way.

 

[vyv_cox]

The deposit that forms is almost identical to the scale that forms in kettles, so descaler should work well. Hydrochloric acid works more quickly but it may attack the aluminium casting, so don't be tempted to leave it overnight. 10 minutes should be ample.

 

[Refueler]

Vinegar is worth a try worked for me in the past and is fairly cheap. Give it a good soak.

Vinegar is based on Acetic Acid variant and is a very good descaler.

Coca Cola is also another as it has a small amount of compound based on Phossy Acid in it ... no wonder it rots teeth !!

 

[HissyFit]

If the problem is that the alloy has corroded (more likely than not with alloy/steel interface) ammonia dissolves aluminium oxide. This was the recommendation from a respected bike maintenance guru for the oft encountered problem of alloy seatpins stuck in steel bike frames. His next recommendation was drain cleaner.

[You're thinking of thermal expansion to expand the alloy away from the pin. How's about sticking it all in a bucket of ice first? That way you'll get the greatest differential in the rate of expansion between the alloy and the steel (the steel will still be warming up when you've got the alloy hot.]

[Edit: Thinking about the above sentence, I realise i'm being very dumb. The material expands under heat, thus the hole will shrink making the situation worse. Cold is the answer, not heat. Either wait for a long time with the end in the previously mentioned bucket of ice or, better still, find an old CO2 fire extinguisher that someone is throwing out. If you can find a source of dry ice, even better. The alloy will contract, as will the steel pin.]

I don't see why the steel pins need to be such a tight fit in the alloy clamp, after all they are meant to be held in by the force of the spring, not the interference with the clamp. Once it's out you could see about getting 1/1000" taken off its diameter. Then keep it greased. Don't forget to clean out the hole in the clamp, either.