HW90 potential

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scax said:
Soon, I hope to get it outside to see if can shoot straight using my peep sight and mega maga power! The cocking's ok, so I don't mind keeping the power up should that work.
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Just so you know that your tax dollars are being well spent by the snooping CIA, note my above quote from post #32 of this very thread on October 7th and note the White House news headlines for yesterday, October 22nd. I coined the above phrase "mega maga" here and now it made world news just two weeks later. Coincidence? Could be. Does the CIA monitor all communications based on the keyword "maga".... that seems reasonable to assume. Especially gun sites since to this administration, everyone who is pro-gun is an enemy. But pro-gun and maga? How about pro-gun and MEGA MAGA!??? -- ooohhh yeahhh! But I like it, lol!
 
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Ahhh my friends, welcome to my HW90 cookout. Our specialty today is northern germanic seal. How do you like yours? Well done? Please check the photos below to make your selection. (tongue in cheek, that is).

OK. So, how to avoid cooking your HW90 (or any springer!) piston seal. Simple. Never ever put anything combustible down the bore to clean your barrel. I realize I did twice and from the breech end. 1. I used Eezox and thought I only put in a few drops, but obviously got some on a cleaning patch to migrate around the breech seal and the once white Weihrauch seal is now served on toast. I thought it was just factory grease that cooked it and that may well be, but I now blame my cleaning with Eezox (which is actually a great lube) that dries (eventually!) to leave just a dry film, but dangerous in airguns as any that gets in your breech seal area will stay there until it is sucked, little by little, into your compression chamber by piston rebound with each shot and only the tiniest vapor is enough to give a once-in-a-while crazy chrony reading that equates to also melting a not so nice, permanent trough in your piston seal.

So, I replaced the Weihrauch seal with a new Vortek which I am told is also from Germany, but seems higher quality. At some point later, I cleaned the barrel as part of a one-time-only, new barrel conditioning process I used with great results on my custom .22 LR bench rest guns. But I know that I haphazardly used too much barrel cleaner (SiliKroil -- highly combustible) that got not only into the breech seal area, but even into the barrel/barrel block interface. My chrony numbers were so crazy, some showing like 60 ft lbs, that I thought my chrony was broken. Nope. And then, suddenly, chrony numbers went down, down, down as the new piston seal was, shall we say, well and done.

Moral of story: simply don't put anything combustible down your bore. Period. It's just not worth it. I think my barrel/bore/breech seal/barrel block is clear at this point, but it takes an amazingly small amount of Silikroil, for instance, to give very many chamber explosions which are guaranteed to cook your seal just the way you don't like it -- haha!

IMG_20221006_140234940(1).jpgIMG_20221013_181048394(1).jpg
 
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IMG_20221026_100339134.jpgIMG_20221026_100728650.jpg Just click on any thumbnail pic to see it up close....
Those are two photos taken today. One showing the red 27x29x1mm silicone o-ring (hardness 70A), mounted on my piston in that otherwise unused factory groove. The piston with that o-ring seemed to slide into the receiver cylinder bore rather easily, so I did a trick to check to see if it was doing anything: I inserted the piston deep inside with only the o-ring on and without the piston seal installed. Then, I put my finger over the transfer port and held up the receiver to see if the piston would easily fall out (as it would without the o-ring installed) and sure enough, the piston with o-ring moved down, but very, very slowly -- which is just want I wanted. That is, it seals, but not perfectly, so the o-ring is able to block a blast of piston seal blow-by air pressure, but also not retain pressurized air between itself and the piston seal edge. I found these nice o-rings on eSay, seller swint101 with price of $3.79 for two, shipping included. We'll see if it lasts, but as well lubed with Krytox, I think it might. All sharp edges inside my receiver's bore are now smoothed.

The second pic shows the piston's open end with the new brownish, Viton o-rings installed inside with white delrin "backer" and the black compression tube, both all lubed up with some of my Krytox GPL-203 which I use frequently on projects like this one.

And below is a pic showing the piston going into the compression chamber in my receiver -- you can see the new Vortek piston seal with the red o-ring riding behind.IMG_20221026_102059346.jpg

I put this HW90 back together and took about 10 shots just to see how it feels. I didn't secure the front receiver mount bolts with loctite at that point as you need to let it set 24 hours to cure. So, no accuracy or chrony tests yet -- I just pumped it up to 20 bar and took some plinks indoors. Cocking didn't feel anything noticeably different, so that's good. Shooting seemed very solid and maybe more like a single, quiet "thud" than before. "Thud" came to mind as a good nickname for this gun. Oh, and same as before I am not using the inertia weight which I deem useless until proven otherwise.

So, the Viton o-rings seem to be holding air pressure just fine. Cocking feels perhaps more "even" throughout the cocking stroke than earlier -- nice and smooth.

I'll do velocity tests tomorrow, once the loctite has cured on the forward mount bolts. I expect lower initial velocities as the piston seal, two inside and one outside o-rings are all new and will likely need a few hundred rounds to break-in.

And I think the sensation of a nice thud when firing now "may" be due to the one, new silicone o-ring riding behind the piston seal in combination with the noticeably stiffer, two Viton o-rings riding inside the piston, all working together to help keep any metal part of the piston from touching/bouncing/twanging the receiver's compression chamber during the firing cycle. So, all that's left to feel now is a vibrationless, lovely "thud".
Charles
 
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Correction: Loctite 242 (blue) is cured in just 6 hours at 72 degrees. The 24 cure is when the temp is only 39 degrees, such as in your garage on a cool winter day. I put slivers of masking tape on my two front mount bolts/screws to be able to see easily if they loosen during firing, even slightly. Loose mount bolts are the surest way to very poor accuracy in these airguns. Now, on to some simple, indoor accuracy tests and chrony tests..... more to come.
 
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Well, I told you if the o-ring behind the piston seal is a big fail, you'd be the second to know! Accuracy was consistently inconsistent. With each 5 shot group with various pellets, two or three would often make one ragged hole at 10 meters indoors, but then two would be way off. I finally put the chrony on and that seems to tell the story -- in 5 shots, 2 or 3 would be expected velocity at 20bar pumped pressure, but then one would be 200fps low! and another maybe 100 low. My guess is it's the experimental o-ring behind the piston seal causing variable drag, shot to shot. Sometimes touching the cylinder wall, sometimes not, and slowing down the piston when it does, causing low velocity on the pellet. It could be something else happening, but as I can't see it, that's what I think. Too tired to disassemble the gun just now, but I'll take out that o-ring and retest maybe tomorrow. I do hope the two Viton o-rings aren't to blame, but more testing will tell. When we try something and it doesn't work, that's actually good news -- we're doing something new and should expect we may have 999 fails for every big success. I think Thomas Edison said something similar. Cheers to all. Charles
 
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Hi Scax,

LOL - Roast northern germanic seal. But isn't Vortek located in Michigan? Maybe they manufacture their seals in Germany and ship them to the US.

I think you're spot on about combustible oils contributing to piston seal damage. We usually think of dieseling as a single 'big bang'. But small amounts of combustible material probably cause localized micro dieseling, much like carbon deposits cause knock in a gas motor. Like you say:
  • This is where a high temp lube like Krytox may be superior.
  • Keep the piston seal CLEAN!
My question is this: are burned seals caused by dieseling? If so, then all you need to do to avoid burned seals is to eliminate lube on the piston seal. I wonder if we should even use a lube on Vortek seals. They are moly impregnated.

If, on the other hand, the burning is caused by overly high pressures, then what's needed is a different seal material, or perhaps going to piston rings/o-rings.

scax said:
Ahhh my friends, welcome to my HW90 cookout. Our specialty today is northern germanic seal. How do you like yours? Well done? Please check the photos below to make your selection. (tongue in cheek, that is).

OK. So, how to avoid cooking your HW90 (or any springer!) piston seal. Simple. Never ever put anything combustible down the bore to clean your barrel. I realize I did twice and from the breech end. 1. I used Eezox and thought I only put in a few drops, but obviously got some on a cleaning patch to migrate around the breech seal and the once white Weihrauch seal is now served on toast. I thought it was just factory grease that cooked it and that may well be, but I now blame my cleaning with Eezox (which is actually a great lube) that dries (eventually!) to leave just a dry film, but dangerous in airguns as any that gets in your breech seal area will stay there until it is sucked, little by little, into your compression chamber by piston rebound with each shot and only the tiniest vapor is enough to give a once-in-a-while crazy chrony reading that equates to also melting a not so nice, permanent trough in your piston seal.

So, I replaced the Weihrauch seal with a new Vortek which I am told is also from Germany, but seems higher quality. At some point later, I cleaned the barrel as part of a one-time-only, new barrel conditioning process I used with great results on my custom .22 LR bench rest guns. But I know that I haphazardly used too much barrel cleaner (SiliKroil -- highly combustible) that got not only into the breech seal area, but even into the barrel/barrel block interface. My chrony numbers were so crazy, some showing like 60 ft lbs, that I thought my chrony was broken. Nope. And then, suddenly, chrony numbers went down, down, down as the new piston seal was, shall we say, well and done.

Moral of story: simply don't put anything combustible down your bore. Period. It's just not worth it. I think my barrel/bore/breech seal/barrel block is clear at this point, but it takes an amazingly small amount of Silikroil, for instance, to give very many chamber explosions which are guaranteed to cook your seal just the way you don't like it -- haha!

View attachment 299819View attachment 299820
Click to expand...
 
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Even more interesting. I'm curious to see what happens if you use only the Viton o-ring on the piston. Maybe put the leaky old piston seal on the end just as a piston bumper. Will the viton piston seal work? What happens to power?


scax said:
... I did a trick to check to see if it was doing anything: I inserted the piston deep inside with only the o-ring on and without the piston seal installed. Then, I put my finger over the transfer port and held up the receiver to see if the piston would easily fall out (as it would without the o-ring installed) and sure enough, the piston with o-ring moved down, but very, very slowly -- which is just want I wanted. That is, it seals, but not perfectly, so the o-ring is able to block a blast of piston seal blow-by air pressure, but also not retain pressurized air between itself and the piston seal edge.
Charles
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Well, the present political scene is totally beyond my understanding. I can't make heads or tails of it. It's best to just not discuss politics online. Stick to springers and traditional airguns. If the world goes crazy, then at least we'll be able to bag an occasional rabbit or pigeon for the kitchen table, to keep the wife happy.

scax said:
Just so you know that your tax dollars are being well spent by the snooping CIA, note my above quote from post #32 of this very thread on October 7th and note the White House news headlines for yesterday, October 22nd. I coined the above phrase "mega maga" here and now it made world news just two weeks later. Coincidence? Could be. Does the CIA monitor all communications based on the keyword "maga".... that seems reasonable to assume. Especially gun sites since to this administration, everyone who is pro-gun is an enemy. But pro-gun and maga? How about pro-gun and MEGA MAGA!??? -- ooohhh yeahhh! But I like it, lol!
Click to expand...
 
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Well, I was easily able to remove that silicone o-ring behind the piston seal, all from the back of the receiver without removing the barrel block. At this point, I need to simply confirm restored accuracy, so I also replaced even the Viton twin o-rings inside the piston with the originals and will put it all back together this morning after a little shopping. I need a small bottle of loctite 242 blue, especially to secure the two front stock mount bolts which I changed from 5mm to 6mm diameter, carefully drilling and tapping new threads which came out good. Those mount holes/threads take a tremendous beating what with sometimes hard cocking and the double-recoil shock with every shot. 6mm gives much more purchase on the threads to hold things securely, but you still must use Loctite blue on them and let it cure at least 6 hours at room temp before shooting it.

I do have some other experimental ideas to try on the HW90, starting with machining a custom piston seal with a metal face that can withstand very high pressures without damage -- would have to be a very soft metal not to damage the compression chamber bore. Also, I'm beginning to wonder if the old-tech, leather piston seals weren't actually the best. I had one in my old Diana 45 and I used to purposely diesel it for kicks and NEVER had to replace it. On those old leather seals, they are held in place by a very large screw and washer which together absorb almost all the damaging pressure with the leather just going around the outermost edge -- very intelligent design. The Vortek is precision made, but I really don't trust it not to melt again. I did just inspect the new Vortek piston seal which has about 100 shots on it and I could see no signs of damage.

As for lubing the Vortek piston seal which is already sinter-lubed, I would guess it's not needed -- I put the thinnest possible coating inside the receiver cylinder bore of GPL-203, mostly to inhibit corrosion. Less is more when speaking about lube in the compression chamber.

Hoping to have some interesting data to share on accuracy soon enough.....
 
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My Vortek seal does have slight corrosion around the edges. Not sure if that was caused by dieseling, but it doesn't seem to be getting any worse. Definitely nothing that would affect sealing.

I had the same thoughts about a leather seal. Leather is more resistant to burning than most plastic materials. It might be worth modifying a HW90 piston to fit a leather seal. But that raises the questions:

What keeps the leather seal retaining screw from slamming into the end of the cylinder? Just the leather thickness?
Is there enough meat on the end of the HW90 piston to mount a retaining crew?

Sometimes I wish I had a small shop lathe.

You mention up-sizing the stock forearm screws to provide more surface area. That's why I installed a brass cup kit. The holes in the brass cups are a pretty close fit on the screws.

By the way, I have the Schrader valves and a removal tool. So I'll run some low power tests over the next couple of days.
 
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And my new Vortek has a lightened color where it contacts the cylinder wall, but I think that's normal.

I'm just getting into shooting my HW90 again, and did a couple groups of 5 shots at 10 meters in the house and pumped to just 15 bar pressure. The best group was with Crosman ultra mag 14.3grain and measured 0.43" ctc which may not sound great, but had I used sights it might have been better (just kidding). But this was with using just with iron sights, no scope --with a scope, probably 1/3 this naked-eye error. So, not bad at all.

Then, pumped it to 20 bar and first two shots in one hole of 21.3gr Baracuda, then three shots sprayed. Why? When I put the gun back in the stock I didn't check to verify that the trigger guard was properly seated by shooting it once and just put loctite on the screws and waited on the cure. But then, the trigger wouldn't set when cocked which means the trigger guard wasn't engaged properly -- uuugh. So, I just reseated things and put the screws back in without new loctite and sure enough, when I increased to 20 bar, the extra kick (which I hardly sense, but the gun does) loosened the rear trigger guard screw and this caused wild and immediate inaccuracy -- just so you know -- haha. Anyway, all is loctited and just about cured now, so more shooting to begin at 20 bar which should give about 19-21 ft lbs based on past experience with a new Vortek piston seal.

On leather piston seals, there is a pretty darn good article here which gives a nice overview: https://www.pyramydair.com/blog/2018/10/piston-seals-part-1/

And a comparison, new and old seals article: https://www.pyramydair.com/blog/2018/10/piston-seals-part-2/

Our pistons (gas ram gun) also serve as the air pressure reservoir, so great care must be taken when modding to avoid any misshapen pressure leaks, but I think some things could be done with patience and care.

I guess I can't get the chrony readings I got when it was dieseling earlier out of my head -- I mean, I was getting 60 ft lbs! with no apparent damage to anything but the synthetic seal. Hmmm..... may have to think on this one. OK, time to put up a new target -- any volunteer varmints? No? Just askin'
 
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Tuacati said:
I purchased from AoA (June 2022). I emailed them yesterday, but I have not heard back yet. The welding question is more for my general curiosity. 😁
Click to expand...

I imagine someone who is skilled in tig welding could fix it. The operative word is "skilled", because you need good heat control that still gets good penetration and bonding.

(Bonding is not the right word, but someone will correct me.)
 
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Tuacati said:
I stripped down my HW90 to replace the piston seal and found one of the front stock tabs completely broken off from the cylinder (no wonder it was shooting poorly). Can the tab be welded or jb welded back on?View attachment 304254
Click to expand...
Ask me why I'm not shocked by this. Well, what is says is there is a weakness in the design at this point. I had to rethread the 5mm holes to 6mm and even then and with loctite blue -- they come loose when it is pumped to 26 bar. The recoil is more than this design can take, in my opinion. It needs greater thickness and length to make more threads and to allow more area to weld. But I still like my HW90 and will get it sorted. Charles
 
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Tuacati said:
I stripped down my HW90 to replace the piston seal and found one of the front stock tabs completely broken off from the cylinder (no wonder it was shooting poorly). Can the tab be welded or jb welded back on?View attachment 304254
Click to expand...
The same exact thing happened to one of my HW90 cylinders. In your case I would send it back to AoA.

This is a problem with the HW90 and is caused by a weak weld and high recoil. Weihrauch must be aware of this problem. Look at the HW95's. The early HW95s have the welded on tangs. The later ones have a 'fixing block' which mounts on the bottom of the cylinder. It's got holes for the stock screws and a spring for the cocking arm. Here's a picture. https://twchambers.co.uk/twc-parts/fixing-block-with-spring/

This may be why Weihrauch supplies their breakbarrels with small, slotted forearm screws that keep you from applying lots of torque and possible breaking a tang. After my cylinder tang broke off, I became more concerned with the aftermarket brass forearm cups which come with socket head cap screws which can be tightened a lot. I had installed a set on my HW90, not sure if it contribute to the break but you never know. Nowadays I just moderately tighten the screws and count on loctite to keep them tight.

You can order a new cylinder from Krale. I did, and found it's a direct drop-in for a late model HW90. All I had to do was deburr it. Note that Weihrauch modified their piston assembly a few years ago. I don't know the date, serial number, or details of the mod. For more info check with T. W. Chambers airgun spares in England. ( https://twchambers.co.uk ). They answered my letters.

However, I got curious and was able to silver solder the tang back on.

Silver solder is almost as strong as welding, but requires much less heat. Something to keep in mind is that the solder merely flows into the break gap. It does not actually add more contact area. So you're left with a contact patch the same size as the original weld. It doesn't really solve the problem of a small weld area.

I had four temperature considerations. The barrel latching pin is hardened, you do not want to anneal it. The cylinder interior is polished, you do not want to discolor it. The cylinder itself is mild steel so I wasn't too worried about distortion. I wasn't too worried about the exterior bluing.

To locate the broken tang, I screwed a long screw through the broken tang. I then screwed it through the good tang, and adjusted the screw until the broken tang was positioned properly right over the break point. Not perfect but very close.

I used 'Muggyweld' 54% silver solder, and their proprietary flux. It's not cheap.

I started with a propane torch. That didn't have enough heat to properly flow the solder. I stepped up to MAPP gas (purchased at Home Depot). The soldering took only a couple of minutes. (I'm a total duffer with soldering and welding). MAPP is the way to go.

After soldering the only visible damage was to the exterior bluing. I had hoped to keep bluing damage under the stock. Unfortunately, some heat crept up the side of the cylinder, and you can see some bluing damage when it's in the stock. Somebody who knows what they're doing could probably do a better job. Also, a blob of solder slipped down the side of the cylinder, I ended up grinding some of that off.

The inside of the cylinder was still shiny, almost chrome like. No visible discoloration. The latching pin in the middle of the yoke seemed hard, I ran a file over it. So it didn't lose its temper. I put the cylinder in the stock, and installed the screws. Everything fit perfectly. I have not assembled the piston into the cylinder to see if it shoots properly. The main area of concern would be cylinder distortion. I don't have a way to check cylinder ID or out-of-round.

I cleaned it with steel wool and applied OXO bluing. It ain't gorgeous. More of an applied exercise.

UPDATE 12-11-22. I swapped in the cylinder, set the gun to 26 bar, and the silver soldered joint broke. So this is not a dependable fix.

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