How to Remove Piston from Cylinder

Dave S wrote:
Jon Woellhaf wrote:
Is anyone in the chapter a surgeon or does anyone know one personally?
I have a surgeon friend who's an expert in performing abdominal
surgery through a tiny incision. He could remove your appendix though
your belly button. I think someone like him would find it possible to
work through the spark plug holes and squeeze the ring enough to let
it slip past the top of the sleeve.


I think you are smoking something strong if you think a surgeon is
going to use instruments intended for use in the body in a plane - and
as a general rule, the equipment/instrument is usually owned by
hospitals, not by the docs..

I like the grease gun idea the best.. any 'noncompressible' media will
do - water, grease, oil.. just not AIR..

OR.. fill the head with water, valves closed, spark plug hole sealed,
and freeze it. Water expands a little as it freezes.. it will overcome
any shear resistance the rings have.

The ring may not have expanded all the way round, in that case, you
might coax the piston out using a set of long feeler gauges slipped
between the piston and wall and twisting the piston gently. I have a
set of feeler gauges made for piston work that are a little over twelve
inches long. Not surgical tools, but could get the job done. My
Franklin Manual(very dated) shows the max wear cold clearance to be .036
at the piston top, so it just might be doable.

You could also fabricate a tool from music wire by annealing it,
flattening the end very thin with hammer and anvil (small) and then
rehardening it. Working through the plug holes with several tools and a
lot of patience you might be able to coax it back in.

In big transformers we have an effect called magnetostriction (the cause
of the hum you hear) I was curious if it would have an effect on a
piston ring, so I tried it out with a small piston ring from a weedeater
motor in my growler. No effect. I couldn't find my degaussing coil
(which might produce a more useful field), so could not try that, but
suspect that if it did have an effect it would be to open the gap and
actually spread the ring. The ring had a lot more tension than I
thought. I grabbed an old automotive ring (no idea what it is off of --
I save everything) and am guessing that it would take north of ten
pounds of pressure to compress it, which calls for a pretty strong
magnetic field when it is expected to perform over a considerable gap.

There are also several acids that will attack steel and not aluminum. I
have used that dodge many years ago to remove a busted tap from an
aluminum part that I had a lot of time invested in. I used plain
battery acid that time, but I think I recall that nitric acid could work
better. This would likely attack the valve seats and liner, but would
not harm the head or piston. You would want to degrease everything
before trying the acid.

As far as heating it up and pulling the liner, my (very dated) Franklin
manual shows the liner and valve guides are installed with the jug
heated to between 625-650 degrees F. They list this same temperature
for replacement of the guides, but there is no guidance on removing the
liner. It does show the liner is held in place by one or more
(depending on the model) locking pins at the base (flange) of the jug.
The locking pin is inserted in and held in place by two socket head
screws placed in the hole one after another. The cylinder is finish
ground and honed after the pin(s)are installed, so once you pull the
liner, you are sending it out to be reworked, in which case you might as
well let them deal with the whole problem.

Charles

Charles Vincent wrote:

There are also several acids that will attack steel and not aluminum. I
have used that dodge many years ago to remove a busted tap from an
aluminum part that I had a lot of time invested in. I used plain
battery acid that time, but I think I recall that nitric acid could work
better. This would likely attack the valve seats and liner, but would
not harm the head or piston. You would want to degrease everything
before trying the acid.


On reflection, forget I said that. To much risk that the acid would
have some long term effect and I simply don't know enough about it to
recommend it for an aircraft part.

Charles