HW 55 internal weirdness...

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MDriskill

MDriskill

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Jul 17, 2018
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TN, United States
Weihrauch builds a quality air rifle as we all know, and the old HW 55 target rifle has long been my favorite. BUT...our heroes can have feet of clay sometimes, and there's a reaon you need to check out any old gun! Check out this photo:

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What you're seeing, left to right:

+ A quality replacement HW 55 piston seal from my parts stash. Most HW 55 seals I've seen look very similar to this, a simple but high-quality leather cup, with a rigid filler piece in the center.
+ Seal I took out of HW 55S no. 140388 (Burgo label, 1963) years ago. Apparently when HW ran out of the proper filler pieces, they just slammed a couple flat washers under the screw?
+ Seal from HW 55M no. 140385 (Burgo label, 1963). Probably made the same day...with the same awful detail.
+ Seal from HW 55S no. 303567 (1969) that I re-did for a friend some time back. Ditto.
+ Seal I just now removed from my recent Findlay buy, HW 55T no. 878276 (1980). Ditto - yet even worse! The larger washer underneath was plastic. As you can see, now disintegrated, leaving little chunks all inside the receiver and down the barrel (looked like this when I took it out):

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One might expect an occasional "Monday build" from Weihrauch's earlier days I guess, but I am amazed that stuff like this was still around in the Beeman era, and in their top-of-the-line rifle to boot. Yikes, guys!
 
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I appreciate the offer! :D But, if I wasn't clear, I'm convinced what you see in my post above is FACTORY WORK!

When I opened up the first 55 with this weird seal detail years ago, I assumed it was a bad amateur "repair" job. But after finding four guns like this - made at different times, bought from different sellers - I can only assume Weihrauch sometimes used a flat washer instead of a proper filler in the leather piston seal.

The new-to-me 55T is otherwise in really fantastic condition. I don't think it's been opened since the day Beeman shipped it out, and I'm sure the previous owners had no idea this was going on. The seal edge was probably cut by a loose piece of the broken plastic washer, which was then gradually pounded into tiny fragments that became embedded in the front of the seal.
 
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Those exact seals could have come from my own HW55's and that is why, sometimes contrary to the opinions of very knowledgeable historians and devotees of these guns, I install piston seal conversion kits to go from leather to synthetic (like HW did in the last years of production) which reminds me.....I have two to disassemble, check out and likely perform the swap so best order parts while they are available.

I love these old guns and preserve them the best I can but I love to shoot them too and me and them ol' leather seals have never had good relationships, lol.
 
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I just freshened up a HW-55 for a customer 2 days ago ... His serial # @ 1981
Upon disassembly .. VIRGIN internals with old greases intact, varnish etc .... Nothing tore up, just ugly and dried up.

SEAL ... yes Leather and in good shape only requiring a small amount of brushing to take the caking / glaze off the surface. It was a simple slot screw and small washer retaining seal, NO filler.
 
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Thanks gents for the additional info! So my assessment is too harsh I guess - the flat washer seal attachment wasn't a mistake, but something HW actually regarded as a proper design?!?! In a way, that seems even weirder!

I may go with a Maccari spring / guide kit (great luck with 'em in the past), and Vortek piston seal conversion (new to me) in the 55T.
 
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I can see an internal filler being of benefit in two ways, tho not necessarily needed due to the low power of these rifles.

1st being as an impact buffer for piston impacting comp chamber roof , or in reality further crushing the leather seal disrupting it's shape and being kept concentric.
2nd being part of the above... in that as seal is smashed it simply has no where to go INWARD towards the screw keeping seals shape at the outside edge a more even width and increasing service life.

Rebuttal being ....
If the piston decelerates enough on the air cushion of compression, impact we speak of is very slight if any.

The 55 of a few days ago had a VERY light piston, thin walled and slotted both sides. Fitted with a .110" wire spring & tho a few inches of preload present I just can't see it not slowing way down or stopping under the rapid compression cycle.

Ah the many ways to cook chicken 🤣 🤣
 
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Thanks Scott. Your thinking is obviously well ahead of mine, and in line with that of Herr Weihrauch. The proof is in the pudding, and a lot of guys won matches with these guns back in the day, after all. But if the flat washer was intentional - I think it's at least safe to say changing from a metal to PLASTIC one was a mistake. It has disintegrated, cut the seal edge, and caused other problems.

I guess it's the old architect in me acting up...that wadded up seal is just so freakin' UGLY, it's hard for me to see it as anything proper, LOL...!
 
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MDriskill said:
Hi Ron - the port is a big one - it measures slightly over 4 mm. Again, gun is from 1980 and with a leather piston seal (which, as I've learned here, doesn't work quite the way I assumed it did!). :oops:
Click to expand...
Thanks Mike. I believe the larger transfer port was intentional. Leather seals lubed with oil will surely diesel. Which is OK in a controlled environment. The larger transfer port slows pressure build up and reduces
peak pressure thus preventing detonation which is very destructive and terrible for accuracy. The dieseling from oiled leather seals contributes to total power.

The standard Weihrauch transfer with all the synthetic sealed guns I've worked on is 3.2mm. Synthetic sealed guns don't rely on dieseling for power. I've noticed converting a leather sealed gun to synthetic, loses substantial power over the original rating.
 
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MDriskill said:
Excellent info, many thanks.

I've often wondered if HW changed immediately to the smaller port when they changed seal materials...or if it took them a while to suss out what you just described!
Click to expand...
I imagine they sorted out the transfer port size verses piston seal material by time the R1/HW80 was developed in the early eighties. They were trying to squeeze as much as they could from that gun.
 
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Motorhead said:
I just freshened up a HW-55 for a customer 2 days ago ... His serial # @ 1981
Upon disassembly .. VIRGIN internals with old greases intact, varnish etc .... Nothing tore up, just ugly and dried up.

SEAL ... yes Leather and in good shape only requiring a small amount of brushing to take the caking / glaze off the surface. It was a simple slot screw and small washer retaining seal, NO filler.
Click to expand...
So you reused the original leather seal? Is that your first choice if possible? Also, is there a replacement leather seal being made anywhere for these old classics? I prefer to keep them original. The leather seal, IMHO, creates a softer firing cycle. Very good post everyone. Thank you all.
 
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Bear-of-Grayling said:
So you reused the original leather seal? Is that your first choice if possible? Also, is there a replacement leather seal being made anywhere for these old classics? I prefer to keep them original. The leather seal, IMHO, creates a softer firing cycle. Very good post everyone. Thank you all.
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I have used 2 replacement seals from TW Chambers with good results. 1 in a 55S, and 1 in a 50S.
They must be sized, but they work really well.
The leather seals from John Knibbs would probably work as well, but they use a metal washer under the fixing screw, while the Chambers seal uses a plastic filler under the screw, more like the original set up.
I have never used the leather seal that JG Airguns offers, might be worth a look.
 
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Mycapt65 said:
Thanks Mike. I believe the larger transfer port was intentional. Leather seals lubed with oil will surely diesel. Which is OK in a controlled environment. The larger transfer port slows pressure build up and reduces
peak pressure thus preventing detonation which is very destructive and terrible for accuracy. The dieseling from oiled leather seals contributes to total power.

The standard Weihrauch transfer with all the synthetic sealed guns I've worked on is 3.2mm. Synthetic sealed guns don't rely on dieseling for power. I've noticed converting a leather sealed gun to synthetic, loses substantial power over the original rating.
Click to expand...
So do I change out the synthetic back to leather on my 50? The Fella I bought this from did the convertion.
 
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