Some years ago, probably before many of you were born, there were a kind of Levi Jeans with 5 buttons on the fly instead of a zipper. These were, affectionately know in the late 60's and early 70's as 5-Chance Pants - as in five chances to say "no" Oh, well, that was a LONG time ago.
Anyway, back into the HW30S this evening to button the piston. I put three buttons on and then, right or wrong, opted to put two extra buttons (for a total of 5 buttons and hence the earlier digression). I put the extra two a bit closer to the rear edge of the piston. Cleaned the piston with acetone, roughed up the spot where the button was to be applied with a coarse abrasive board, wiped again with acetone, applied a tiny drop of super glue, and then, using the round plastic patch you see on top of the abrasive board, which was cut out of the side of a plastic Coke bottle, pressed the buttons firmly on to the piston for a full minute. The first 3 went at 120 degree intervals with one exactly opposite the cocking shoe slot, about an inch from the rear of the piston. Then, for good measure, two more on the back side about a quarter inch form the bottom edge. Not sure if you can appreciate it from the photo, but the rear end of the piston has a slightly larger OD than the mid shaft of the piston. I was concerned that the buttons positioned above this might not give much protection once they wear in a bit.
After they dried for about an hour, I re-lubed and started to re-asseble. First, with this type of button, you need to take the same care as with the piston seal not to catch them on a sharp metal edge on the way back in. I tried first with the buttons still "dry" -- too tight! Back out, and with a bit finer abrasive board, I smoothed the buttons down just a bit and put just a touch of moly paste on each with a Q-tip. Re-assembly went much easier the second time. The cocking stroke (as before) is perfectly smooth, but now I am a bit more confident that the HW30S shouldn't suffer from galling of the compression tube, now that the excess grease slathered on the spring from the factory has been cleaned off.
BTW, CDT, the OD of the spring guide is 12.79 mm, the OD of the stem on the piston is 9.79 mm, the ID of the spring 13.33 mm and the OD of the spring 18.70 mm
Perhaps you're right, and yet, the two extra buttons on the back side now provide a three-point cushion on the back side of the piston where the cocking forces are most apt to gall the tube, and the two extra I added "aft the very end" (you're not a sailor, are you Paul?) were because, as I thought I pointed out, that the end of the piston, having a bit larger OD, seemed like it might have still contacted the compression tube after even a very little bit of wear on the one button that was primarily bearing on that surface. When I get my electronic gem scale, perhaps I can tell you how many milligrams of dead weight two extra buttons added. They may or may not do any good, but I doubt they do any harm.
Paul: Understand. Thanks, bro. First time I have tried this. BTW, hope things turn around for you soon. Don't mistake my attempt at wit with anything but respect and good will for a fellow member of the GTA.
I'll be polishing poop today, doing the same thing with a B-2-2 Chinese rifle, school time for me today. The piston in the B-2 has a bell on the end of it so may try a different type of button just to see what it does and if it will stand up, drill and tap holes in the piston and turn down and thread some delrin rod for the buttons, some stupid glue should keep them in place I'd think.....
TEC, nice work I bet the firing cycle is smoother now. You shouldn't have to worry about wear on the buttons, I read on JM's sire that after many thousand rounds, there was no wear, on one he did years ago. I'll be buttoning up a couple of pistons next weekend, if Gustav doesn't blow me away.
: What about the top of the piston seal end?
: 3n00nAugust 30, 2008, 12:50:31 AM
That is often a severe wear point, at the top of the fowardedge of the metal ring, 'jumping up' when the sear releases.
Nice work Tommy!! should be a real smooth shooter when your done... let us know how she turns out.
: RE: What about the top of the piston seal end?
: TCupsAugust 30, 2008, 12:59:00 AM
Rats!!
Well, OK, J -- so now that you inform me that I should really go bank in and button up the forward edge too, you are honor bound to turn me up a new synthetic seal for the HW30 that fits tightly to the piston. Hope you work cheap. Would you trade same work for a CDT trigger? I hope to pick one up today, and hear you might need one for one of the many projects you are working on.
: I thought I'd mentioned that at McAlister's Deli . . .
: 3n00nAugust 30, 2008, 01:16:19 AM
I'm sure we can figger sumthin' out, though. Haven't even opened the Gamo up yet, but will probably be looking at the breech seal, piston seal, guideand choke sometime this week, after I get a bit of finish on an old match plinker. (http://../images/emoticons/wink.gif)
: RE: I thought I'd mentioned that at McAlister's Deli . . .
: TCupsAugust 30, 2008, 07:51:20 AM
Hey J I picked up a present for you this morning. . . and one for me, too. Later, dude.
: Soon to be another happy Gamo!
: 3n00nAugust 30, 2008, 10:14:54 AM
Drop me a line when ya have a minute.
: Heat shrink
: kiwiAugust 30, 2008, 12:22:21 PM
Hi...I put a band of pre glued heat shrink on my piston. Its the stuf they use for sealing wire joins. place a band on the piston shrink it with a heat gun then just cut away the areas you dont want. keep in mine as it shrinks it gets thicker so if you have a big gap between the piston & chamber use a bit whitch is a bit bigger in ID than the piston & vice a versa for a close fit piston.
Very clever, Peter. As I think more about it, maybe what is needed is just the glue without the button or the heat shrink material. A thin bead of epoxy resin spread flat, hardended and sanded smooth would protect the piston too.
Tcups, you wasted a couple buttons! The only place for them are at the end of the piston because it is usually flared there. Looking at your photo, I can't see it. Maybe they changed the design? The most wear on that piston will be at the 12 o clock position. Look at Paul Watts site and his description of the R7 tune.The buttons toward the seal end will not even contact anything. 3 is good, 5 is better. Be sure they clear the trigger pin holes and the cocking slot. You will be fine. And fit the buttons without the seal on the piston! I found that one out the LOOOONG way!
Understand. The last two were just for that reason -- the flare or bulge or bell on the end of the piston or what ever you want to call it. The wasted buttons were actually the first three.