Weihrauch HW55

[nick_mantis]

Just found this over on airgunation. HW55T being stripped for a new leather seal. Same 2 piece construction, aluminium/steel, and it's threaded! It is the exact same piston so either someone was selling aftermarket pistons or Weihrauch were threading the cylinder onto the head. Will be interesting to see what DJ finds investigating his. Even the machining is the same. Welds not so sure, might just show up on mine because they have gaps and dirt in them.

If anyone is junking an old piston with a damaged head but good tube I have a kidney here with your name on it....well not literally......don't think tatoo's go that deep....

[evert]

Just found this over on airgunation. HW55T being stripped for a new leather seal. Same 2 piece construction, aluminium/steel, and it's threaded! It is the exact same piston so either someone was selling aftermarket pistons or Weihrauch were threading the cylinder onto the head. Will be interesting to see what DJ finds investigating his. Even the machining is the same. Welds not so sure, might just show up on mine because they have gaps and dirt in them.

If anyone is junking an old piston with a damaged head but good tube I have a kidney here with your name on it....well not literally......don't think tatoo's go that deep....

Does not look like this one has the same welds as yours did.
Remember that the threads on your aluminium piston head probably are damaged when the body slipped off- replacing the body while keeping the head may lead to just another failure.

But the piston in the last picture had the same serious flaw as yours did- the cocking groove covers very much of the threaded area.
If a piston is made up with threaded body all the way up to the seal, I suspect it may be a lot stronger.

[nick_mantis]

I see what you are saying, and as you can see on mine there is a washer butted up against the aluminium head that would stop the cocking lever from getting that far up the slot so there doesn't seem to be any reason for it other than to save weight. To be that perfectly line up as well with a cross pin has it been assembled, pinned, and then the slot milled through everything?

Whatever they did looks like I need a like for like to keep the action as fast as it is. Also looking at DJ's 2 pistons the older steel one is shorter, ie. if the same spring was used with both pistons the aluminium head doesn't let the spring decompress as much (ignoring the 2 thicknesses of seal). If I dropped in a shorter piston could that induce bounce at the end of the firing stroke, and then would be looking at trying to get a spring to match a new piston to keep everything within competition levels.

Only needed a few months out of it too as was going to retire the Weihrauch for occasional use and upgrade to a PCP for competition.

Does not look like this one has the same welds as yours did.
Remember that the threads on your aluminium piston head probably are damaged when the body slipped off- replacing the body while keeping the head may lead to just another failure.

But the piston in the last picture had the same serious flaw as yours did- the cocking groove covers very much of the threaded area.
If a piston is made up with threaded body all the way up to the seal, I suspect it may be a lot stronger.

[evert]

The slot is milled for clearance with the cocking shoe, but does not pose the same problem on the soldered piston heads of steel.
The washer probably clears the cocking shoe, as it is close to the same diameter as the spring, I have a similar setup on some of my HW50's.

From your pictures, the weld on your piston to be from previous repairs?

[deejayuu]

Good read here. Will try to do some dismantling/photos tomorrow.

[TonyL]

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

Absolutely 100% with you, Mick.

[T 20]

Good read here. Will try to do some dismantling/photos tomorrow.

I'm intrigued for a couple of reasons, Jules.

Although Aluminium is about a third of the weight of steel per cc, the aluminium section of the piston head shown is about two times longer than that section on the all steel pistons --- hence my interest in the piston weight.
The long Aluminium section could just be long to allow enough thread engagement in the steel body, but then it's strength has been compromised by machining a slot into it --- weird.

The other thing I've noticed this morning is that the piston head appears to be an O ring conversion which probably accounts for the gun's consistency.





All the best Mick

[TonyL]

And I must get around to stripping my 55 one day (this won't be helping others on here)........bought about ten years ago from a very nice forum member. I wasn't actively seeking one but it needed buying! I only had a few shots with it and remember it being quite twangy but the recoil being very low. But it's lived in the cabinet ever since. Must pul my finger out and have a look inside. I could understand the use of aluminium to reduce the weight, but not convinced over its suitability vs good old steel. Is it sounding like these might indeed have an ally piston?

[robmc]

If anyone is junking an old piston with a damaged head but good tube I have a kidney here with your name on it....well not literally......don't think tatoo's go that deep...

I have a Hw55 piston,
I'd swap it for your kidney or £50 (whichever you prefer!)

I've sent you a pm and email with pics.
Regards,
Rob

[evert]

I'm intrigued for a couple of reasons, Jules.

Although Aluminium is about a third of the weight of steel per cc, the aluminium section of the piston head shown is about two times longer than that section on the all steel pistons --- hence my interest in the piston weight.
The long Aluminium section could just be long to allow enough thread engagement in the steel body, but then it's strength has been compromised by machining a slot into it --- weird.

The other thing I've noticed this morning is that the piston head appears to be an O ring conversion which probably accounts for the gun's consistency.





All the best Mick

The thing I dont understand is why they didnt extend the piston body all the way up to the seal.
That way there would be lot more threads uncompromised by the cocking slot.

[nick_mantis]

Weighed the piston tonight for those interested. And to be fair I have stripped it of any accessories that would alter it.

This is just for the:
Steel body
Aluminium head
Steel hook

Excluded:
Piston seal
Washers/brass spring seat
(basically anything that can change from rifle to rifle)

Total Weight: 149.48g Allow a tiny bit extra for a tiny amount of missing material but I would reckon 149.50g for these pistons.

[HW777]

It would appear your piston has been repaired or adapted ? I can't find the picture of your latch rod/alloy block but from the above pics, from the top edge down and right there is a circle, was this filled with anything and is there any sign of a cross pin having been fitted through the alloy block ?

I weighed a bare 55 piston and it comes up as 152.2 grams, lighter than I expected and the alloy block is threaded into the piston.

[deejayuu]

Here's two 50 pistons from unknown platforms and a one from a 55 marked Burgo 52897, the retailer, not Weihrauch but HW55 nonetheless.
The Burgo is the same as our 55T 417827 with aluminium alloy screwed head with steel cross pin.

https://photos.app.goo.gl/1KoTwMoSwYSdr3ji7

[T 20]

It would appear your piston has been repaired or adapted ? I can't find the picture of your latch rod/alloy block but from the above pics, from the top edge down and right there is a circle, was this filled with anything and is there any sign of a cross pin having been fitted through the alloy block ?

I weighed a bare 55 piston and it comes up as 152.2 grams, lighter than I expected and the alloy block is threaded into the piston.

Interesting, John.

The HW50 synthetic seal piston using the same bore and stroke as the HW55 weighs in at 199g, and the HW50 uses a stronger Spring than the HW55.



All the best Mick



Ps :- I've not forgot your Hawk piston, I'm just waiting for my eyesight to get back to normal after the Covid jab --- if push comes to shove I'll send you my piston so you can crack on.

[TonyL]

Hope you're feeling much better very soon, Mick.

The HW50 that Nick, Oldskoolz, found for me about five years ago is another non-started project of mine. I'll be sure to carefully inspect, weigh and compare the pistons of that and the 55 when I finally get around to fettling them and share the information.