polyurethane for seals

[Benelli B76]

I have found 85 to 90 degree Shore A hardness polyurethane to be good for impact resistance.It is used for loading dock buffers for trucks to back into.For airgun parts I buy it in rod form and turn it, there is a trick to this to get a good finish.

Baz

[wonky donky]

I have found 85 to 90 degree Shore A hardness polyurethane to be good for impact resistance.It is used for loading dock buffers for trucks to back into.For airgun parts I buy it in rod form and turn it, there is a trick to this to get a good finish.

Baz

Well is the "trick" a secret Barry or are you willing to to share with us? I've been turning 93 shore Polyurethane for some time to make piston seals. Getting the seal to work is not a problem, getting a good finish everytime is. This is typical.

I have used my dremel in a makeshift tool post holder with the lathe in reverse for grinding, made up holders to carry scalpels & hobby cutting tools, used stoned tool steel all to only achieve adequate parts.

Here is one of JB's BTW out of a modified BSA

I've also used Polyurethane for piston buffers similar to BSA's as well as pistons inside an alloy piston nose as well as rubber. Now I do know if you can get it right it does work, but I haven't as yet, not to my satisfaction anyway! The closest I got is with the piston in the nose. Using the buffer I either get no perceptible difference or I can feel a double "surge" & the result is a loss of Vo, as much as 70fps with a similar stroke to a non buffered set up.

I feel the solution will be very different for every rifle or even pellet to a point.

[Shed tuner]

I've also used Polyurethane for piston buffers similar to BSA's as well as pistons inside an alloy piston nose as well as rubber. Now I do know if you can get it right it does work, but I haven't as yet, not to my satisfaction anyway! The closest I got is with the piston in the nose. Using the buffer I either get no perceptible difference or I can feel a double "surge" & the result is a loss of Vo, as much as 70fps with a similar stroke to a non buffered set up.

I feel the solution will be very different for every rifle or even pellet to a point.

Yeah, it's going be be very tricky as ideally you'd need both shock absorbing and damping properties... and we've very little space to work within!

[greenwayjames]

Here is one of JB's BTW out of a modified BSA

.

It would be interesting to know when JB did that work. I have tried to get him to do work on a springer but was told that he hadn't worked on springers for well over 20 years
I was given a hint that he was thinking of re-visiting his last spring airgun design that he developed while a partner at Titan back around 1990. He wouldnt give details only saying nothing like it has been seen before. "A totally different layout to the conventional thinking of what a spring air rifle should be" is what he said