I'm Sat Waiting On Postman Pat

[T 20]

I'm now working on the assumption that the HW99 piston with its 71 mm stroke has an overall length of 146 mm, so by replacing the 10 mm wide HW seal with a 5 mm wide TX seal I could stroke it by 5 mm to 76 mm.

Well I was way off with that assumption.

It appears that the HW99 piston is 156mm long and not 146mm as I'd expected, after further reading it turns out that ONLY the external dimensions of the HW99 action are the same as an Old School HW50 action.

When Weihrauch changed from the Old School 50 to the HW99 they increased the cylinder bore from 25mm to 26mm, they increased the piston stroke from 65mm to 71mm, but more importantly to my search for a suitable piston Weihrauch shortened the transfer port from 26mm to 16mm --- a full 10mm.
This explains why the HW99 piston is a full 10mm longer than I expected as the internal length of the cylinder is 10mm longer than the Old HW50.

I could possibly still use a HW99 piston by machining off the Weihrauch seal arbor then machining the front of the piston to accept a TX seal giving me a 71mm stroke.

But I may just park this one up again while I wait and see what appears in the sales section this year.






All the best Mick

[evert]

.....
But I may just park this one up again while I wait and see what appears in the sales section this year.



All the best Mick

OR you could drill out the locking pin, unsolder the piston body from the piston front, and shorten the rod of the piston your are working on?
Maybe make up a new piston front and use the piston body and rod, shortened to give you the maximum stroke available with these components?

[T 20]

OR you could drill out the locking pin, unsolder the piston body from the piston front, and shorten the rod of the piston your are working on?
Maybe make up a new piston front and use the piston body and rod, shortened to give you the maximum stroke available with these components?

That's a lot more work than you'd imagine, Evert --- it would be quicker to build a new piston from scratch.

I still think starting with a 99 piston would be the quickest option, but until I have one in my hands I'm only guessing.





All the best Mick

[evert]

That's a lot more work than you'd imagine, Evert --- it would be quicker to build a new piston from scratch.

I still think starting with a 99 piston would be the quickest option, but until I have one in my hands I'm only guessing.





All the best Mick

For me it would be easier to use the original parts. I have a good lathe, and am fairly comfortable with its use.
But my milling equipment and skill is less than mediocre, and I'm not comfortable with the hardening needed to make a new piston rod.