I'm Sat Waiting On Postman Pat

[evert]

Ah, Evert.

Embarrassingly, and weirdly, after a quick measure I only seem to have a 66.5mm stroke. --- I thought I was over 71mm.

I'll double check in the morning and strip the action down again but it looks like I'll have to machine up a custom piston.
Alternatively, perhaps I could use a 99 piston and just replace the body with a 25mm one, depending on the 99 piston's length.



All the best Mick

If my memory is correct, its been stated somewhere that the HW55 has been delivered with different pistons adapted to different power level.
May just be a rumor though, or me remembering something that was said about another gun.

[T 20]

If my memory is correct, its been stated somewhere that the HW55 has been delivered with different pistons adapted to different power level.
May just be a rumor though, or me remembering something that was said about another gun.

I'll definitely be stripping the HW50 action down in the morning as something doesn't add up here after reading this thread :-

https://www.airgunbbs.com/showthread...15#post7990915



Perhaps I measured it wrong this afternoon, though I don't think I did --- very weird.

[T 20]

I'll definitely be stripping the HW50 action down in the morning as something doesn't add up here after reading this thread :-

https://www.airgunbbs.com/showthread...15#post7990915



Perhaps I measured it wrong this afternoon, though I don't think I did --- very weird.

I did measure this wrongly.

After stripping the action this morning I found the stroke to be 69.45mm, this ties in with my prediction of the stroke in the above link, which I missed yesterday.

I will try to have a measuring session over the weekend and then work out the design for a new piston, though it could be that I could extend the stroke on the piston I have.




All the best Mick

[evert]

I did measure this wrongly.

After stripping the action this morning I found the stroke to be 69.45mm, this ties in with my prediction of the stroke in the above link, which I missed yesterday.

I will try to have a measuring session over the weekend and then work out the design for a new piston, though it could be that I could extend the stroke on the piston I have.




All the best Mick

The stroke is somewhat limited by the cylinder in itself. I think you may be able to reach 75mm, but not much more.
And you may probably reach those 75mm's by just trimming the front of the piston.
I'm a bit afraid to take too much off and have the piston coming apart during cocking.

[T 20]

The stroke is somewhat limited by the cylinder in itself. I think you may be able to reach 75mm, but not much more.
And you may probably reach those 75mm's by just trimming the front of the piston.
I'm a bit afraid to take too much off and have the piston coming apart during cocking.

As I started out with a 65mm stroke piston my machining for the TX piston seal is now within 0.5mm of the cross pin hole, so machining the piston face back any further is a none starter strength wise, Evert.

I'm pretty confident that altering a 99 piston could be my best bet --- but if someone could tell me the overall length of a HW99 piston I'd know for sure ?




All the best Mick

[evert]

As I started out with a 65mm stroke piston my machining for the TX piston seal is now within 0.5mm of the cross pin hole, so machining the piston face back any further is a none starter strength wise, Evert.

I'm pretty confident that altering a 99 piston could be my best bet --- but if someone could tell me the overall length of a HW99 piston I'd know for sure ?




All the best Mick

I havent seen any cross pin hole
Looks to me like it was brazed toghether.

[BTDT]

I havent seen any cross pin hole
Looks to me like it was brazed toghether.

My HW55's piston has a cross pin.

[T 20]

I havent seen any cross pin hole
Looks to me like it was brazed toghether.

My 50 piston has both cross pin and brazing :-

image.jpg