Weihrauch HW55

[crowbar]

Do your two pistons have aluminium heads?

Do they have two slots?

Are the heads pinned with a dowel?

Threads were used to fix breech blocks to comp tubes on early guns and soft soldered so I still think the long head will be
threaded and the short head brazed.

[T 20]

Here's a couple of 55 pistons
One earlier than the other https://photos.app.goo.gl/zwV6odNxi1gN1xQQ8

That's certainly buggered my theory then Jules.

Looking at the damaged piston I'm surprised it lasted as long as it did.

I must get round to stripping my 55 some time to see which piston it has as I'd be better off with the synthetic one so that I can long stroke it using a TX seal.


All the best Mick

[evert]

Seems like there is a lot of different pistons in the old 50 and 55, both between the models and within the models.
We should really make a thread on it, and gather pictures and all the facts we can find.

Other than that, a threaded aluminium head sounds like a recipe for disaster to me.

[nick_mantis]

The piston that has come out of mine has:

Aluminium head
Double slotted steel body
Adapter for synthetic seal but that is literally just attached to the front of the head with a single screw as the leather ones are.

The body was screwed onto the aluminium head with a pin running right through presumably to stop it unscrewing itself. The pin is offset to allow for the steel catch bar running down the middle.

On my internet travels I have not yet found any pistons built like this (any make) but no-one shows a piston in it's component form, just changing the seals which isn't really helpful. The seal conversions I have seen for the HW55 are not using 'o' rings like this one, just a big rubber bung to replicate the size of the leather.

[T 20]

The piston that has come out of mine has:

Aluminium head
Double slotted steel body
Adapter for synthetic seal but that is literally just attached to the front of the head with a single screw as the leather ones are.

The body was screwed onto the aluminium head with a pin running right through presumably to stop it unscrewing itself. The pin is offset to allow for the steel catch bar running down the middle.

On my internet travels I have not yet found any pistons built like this (any make) but no-one shows a piston in it's component form, just changing the seals which isn't really helpful. The seal conversions I have seen for the HW55 are not using 'o' rings like this one, just a big rubber bung to replicate the size of the leather.

Could you weigh the remains of the piston to give me an idea of the overall weight of the alloy piston, please --- the gun serial number would also be useful.

I have heard of the 55 having a steel and aluminium piston before but never come across one.




All the best Mick

[crowbar]

The steel head is the standard piston and the aluminium head is the match piston and the steel head piston would be
fitted to the base models HWSM and 55s and the aluminium head piston would be fitted to the HW55T,HWMM and 55M
models.

[nick_mantis]

Could you weigh the remains of the piston to give me an idea of the overall weight of the alloy piston, please --- the gun serial number would also be useful.

I have heard of the 55 having a steel and aluminium piston before but never come across one.




All the best Mick

Went to try and my scales are dead, so ordered some batteries and will have a go over the weekend.

However the serial number is 744907, and yes it is in a match stock as on page 1.

Cleaning everything up it might not actually be the threads or pin that have failed, but in-fact spot welds. If they failed the end of the the tube would have opened up over the pin and thus the head separated. The front of the tube has been machined down as well, presumably as it now runs on the 'O' ring and doesn't need the tiny swell at both ends, only at the back.

[crowbar]

It looks like the piston body is made of aluminium from your last picture and with use will have work hardened and built up
stress fractures till it cracked,steel on the otherhand needs to be stressed beyond it's yield point before it will crack.

I also think the spot welds are a repair done by a prior owner ,but I know nothing!

[evert]

I also think the spot welds are a repair done by a prior owner ,but I know nothing!

I tend to agree on the welds being home made looking.
But a mix of aluminium, steel, threads and welds sounds like someone have been tinkering heavily...

[T 20]

I tend to agree on the welds being home made looking.
But a mix of aluminium, steel, threads and welds sounds like someone have been tinkering heavily...

To be honest the piston looks like the modifications to it turned it into a right old knacker, I'm just happy for Nick that the cylinder came out of this unscathed.

As I said earlier in the thread, it would be a simple job to machine up a new piston using the salvaged latch rod from the old one.

BTW the gun dates from around late 1979, Nick.





All the best Mick

[junglie]

My BSf S70 head detached like that when the spot welds failed too just after i replaced the mainspring with a standard one not export.

[TonyL]

To be honest the piston looks like the modifications to it turned it into a right old knacker, I'm just happy for Nick that the cylinder came out of this unscathed.

As I said earlier in the thread, it would be a simple job to machine up a new piston using the salvaged latch rod from the old one.

All the best Mick

Jumping in very late on this. Sorry. But 100% what Mick says.

There will be people out there able to undertake this work, but many of these would only do so for their own projects. Thinking NickG might be able to assist?

[T 20]

Jumping in very late on this. Sorry. But 100% what Mick says.

There will be people out there able to undertake this work, but many of these would only do so for their own projects. Thinking NickG might be able to assist?

My big problem with making custom parts for other folks is that I like to take my time and I couldn't possibly charge an hourly rate accordingly, Tone.
The Pistons I've shown that I've made have all been for my own guns, so I never take the cost into consideration with them.

I'd rather leave the custom parts making to other folks rather than get too involved in things so I would also recommend NickG for this.




All the best Mick

[HW777]

My big problem with making custom parts for other folks is that I like to take my time and I couldn't possibly charge an hourly rate accordingly, Tone.
The Pistons I've shown that I've made have all been for my own guns, so I never take the cost into consideration with them.

I'd rather leave the custom parts making to other folks rather than get too involved in things so I would also recommend NickG for this.




All the best Mick

I've been asked to tune other people's rifles Mick but back off when they only want power above performance

DJ has offered Nick a piston and given they are a obsolete part and hard to find, that would be an ideal opportunity for him to replace his broken piston

As to converting Hw 25mm pistons from leather to synthetic, the early model smk B20 seal looks like a good option, plenty of extra sweep volume but I wonder how the compare the a tx seal ?

Atb

John

[T 20]

As to converting Hw 25mm pistons from leather to synthetic, the early model smk B20 seal looks like a good option, plenty of extra sweep volume but I wonder how the compare the a tx seal ?

Atb

John

Hi John.

If the B20 has become the X20 then it's a copy of the Weihrauch HW85/95 and has a 26mm cylinder :-

image.jpg

The TX seal and a few Diana and SMK seals are 25mm with the same dovetail fixing as the X20, I tend to use the TX seal when long stroking the 25mm cylinder Weihrauchs.
The Weihrauch seal is 10mm long, the TX seal is 5mm long, so by simply machining the Weihrauch seal arbor down into a TX dovetail arbor you get a piston with 5mm of extra stroke.
The piston cocking lever slot also needs extending a tad for this modification but basically it's a very simple modification that you can either use to increase power output or use at the original power output with less Spring length.

The X20 seal shown could be useful for longstroking a HW95 (God knows why you'd want to) or longstroking a HW99 as their cocking geometry will easily cock a 76mm stroke piston.





All the best Mick