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Slavia · Moderator

I've been reading about "buttoning" pistons. This apparently involves super glue and little pieces of plastic on the sides of the piston in a springer. This is to prevent metal-to-metal contact between the piston and compression tube.

While the concept sounds good, I'm curious about the super glue holding, what with expansion/contraction, lubricants migrating into the pores under the glue, and of course the stress of normal firing.

Anyone with experience? Opinions?

cw · Banned

I've always had durability

j.m. · Member

Depending on how big the piece of plastic is, super glue should hold quite well enough.

In my experience it can have a VERY strong bond.

(I build model planes)

Another idea would be to machine a piston out of delrin. Though I don't know how it would hold up...

kanyon · Silver Status Member

Hi.. have read a bit about it putting 3 buttons spaced around the rear of the piston supa glue seems to hold them in place.
But I really can't see a need for them any contact between piston and
tube is very low pressure/friction and this contact happens above where the seal runs. "gimmick"
my guns will never see piston buttons. But someone ealse may think they are the best thing since sliced bread, To each his own

Amigo · Veteran Member

The pistons I've seen buttoned were first "spotted" with a flat bottom end mill to provide a flat and slightly recessed seat for a same sized Delrin button.
After all buttons (3 or 4 depending on cocking system) were super-glued in place, the piston was chucked on center and the piston button assy. turned to a slip fit in the tube.

With the piston positively located with each cocking cycle, the trigger sear locates and seats consistently and thus releases more consistently and consistency usually improves accuracy. Also, without buttons, piston skirt wear and tube wear could eventually impair proper sear engagement rendering a gun unsafe.

Hope this helps

Amigo

Alstone · Moderator & Site Supporter

Yea I'll go along with Amigo, spot the skirt with a very small drill and open out with a shallow ground drill, three around the skirt should do it. You only need about 0.010" depth. and use Derilin inserts.

Al

dummyracer36 · Senior Member

if i'm totally off base here, someone please set me straight. but this sounds like a theory borrowed from the motorsports industry. putting "buttons" on pistons has been a practice in race engines for some time, and the reason for doing it has nothing to do with stopping piston to cylinder wear. it is done to keep piston wrist pin circlips from coming out and allowing the engine to eat itself.the button fills the recess for the wrist pin and applies positive pressure to the seated circlip keeping everything in place. since airgun pistons arent assembled like a piston from an engine, i just dont see the advantage....

cw · Banned

They are used in

cliffspot · Veteran Member

I have used the Maccari glue on "Old school" buttons with good results. Just make sure you fit them BEFORE you install the seal! I had a DUHHHH episode on that one! The wear actually comes from the cocking stroke as the cocking lever pushes the top of the piston against the top of the tube. I use the buttons to hold off the clearances between the piston skirt and the comp tube because less wear (minor) but mainly to facilitate better consistency shot to shot. Think about it, if the piston flies true with no axial variation on every shot, consistency should be optimal. I have used the buttons on my HW77 chamber and piston and the gun is super smooth to cock and shoot.

broommaster2000 · Moderator

Jan did it to his HW97K.

cw · Banned

Interesting. I have never seen them installed without
recesses machined into the piston skirt.

broommaster2000 · Moderator

I must say, that rifle shoots darn well.

cliffspot · Veteran Member

But the buttons on the front of the piston are for naught. The piston seal prevents that part from touching anything.

kanyon · Silver Status Member

kanyon · Silver Status Member

On a side note: Hey Dummyracer, I don't know if you were ever
into 2-strokes, but if so, do you remember the old racer's secret
of corking or plugging the bottom end to raise the compression
ratio of the lower end for more power and better throttle response?[/quote]

Hummmmmmm would have to have soom real design floors that to be of any use.... Older Villers type mottors I asume you are refering to.
Reid valve mottors don't lose crank case volume back though the intake
like the older piston port mottors did. so reducing the volume of the crank case would defeet what you are trying gain as the less volume in the crank the less you can aford to lose back though the intake port.
changing the intake port timeing would have far more benifits.

TWO STROKES RULE