SpudFiles

I snagged a cheap set of four sanding drums for my drill press at Harbor Freight the other day...just your basic sanding sleeve around a rubber cylinder with a bolt through it. After I got them home, I grabbed a scrap piece of 2" sch 40 and, whatayaknow, the 2" drum (without the sand paper, of course) is a great fit! Ready-made piston.
I stripped the hardware off of it, slapped a couple washers on either side, a piece of bike inner tube on the front, a nut and bolt and, voila, an adjustable piston. As you tighten down the nut, the dense rubber "squishes" and expands, giving you an infinitely fine-tuneable piston. Seems pretty durable, too. The best part? $7.99, and you still have three other sanding drums.
Anywho, perhaps someone can benefit from this. Through no fault of the piston's, I'm having no luck constructing a functioning piston valve. I'll keep trying though. Here are some pictures...





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Very nice find there! I may run over there and snatch up a set of these.

It looks like you had all the parts there, but in the cunstructed piston pic, I don't see the sealing face. All you gotta do is put that rubber washer on one of the ends of that bolt, between the 2" washer and the bolt head. Preferbably a rubber washer with a small inner diameter (that of the bolt, guessing 1/4"). Then put a smaller washer, like 1/2" in diameter, or something at least a tad smaller than your barrel size, between your new rubber washer and the bolt head.

Sooo.. on the bolt, from one direction to the other, it'd be...

Nut -> 2" Washer -> Sanding Drum -> 2" Washer -> Rubber washer sealing face -> Smaller washer -> Bolt Head

Just remember a few things -- 1. your sealing face (the rubber washer)should ideally be as large as the outer diameter of your barrel, and of course, no larger than the piston diameter itself. 2. the smaller washer you use to hold the sealing face to the larger washer should be SMALLER than the inner diameter of your barrel.

EDIT: Durrr, I see it now. It's just so thin that I missed it so I thought I was looking at the steel washer. Okay, I oughta go to bed.

That being said, are you using this in a coax configuration?

Make sense? That's what you're doing, right?

You could whip up a few o-ring grooves relatively easily

Nice find btw, i'm tempted to make a 'most creative piston' thread.

So far the most creative piston i've made is two .303 shell casings, cut in half and stuck together. The small indent ring before the base of the shell serves as a good o-ring groove too

Again nice find and nice piston. Two questions:

1) How much does it weigh?

2) It may have quite a bit of friction if it's made from rubber, so have you tried putting some lubricant on it?

Blitz wrote:That being said, are you using this in a coax configuration?

Make sense? That's what you're doing, right?

Well, at the time of the original post it was in a coax gun....but I didn't make it serviceable, so now its been dissected.

MrCrowley wrote: Again nice find and nice piston. Two questions:

1) How much does it weigh?

2) It may have quite a bit of friction if it's made from rubber, so have you tried putting some lubricant on it?

1) It weighs 5.75 oz. with all the hardware attached., its got a pretty good heft to it.

2) Actually, without tightening down the bolt, it fits loosely in the housing with no resistance. I've got it tightened to the point that its got just enough resistance to be pushed with one finger and it doesn't catch or snag. I might try tightening it a tad more and lubing it up to see if that improves my results.

cornflake_81 wrote: 2) Actually, without tightening down the bolt, it fits loosely in the housing with no resistance. I've got it tightened to the point that its got just enough resistance to be pushed with one finger and it doesn't catch or snag. I might try tightening it a tad more and lubing it up to see if that improves my results.

Yes I recommend to try that.
I think it also deforms under pressure but I am not sure in wich way.
It may become smaller, or because of the pressure against the sealing face, squished in and become thick.

Wow thanks sooooooo much for that, i never really got the whole concept of the piston thing.

i was reading up on some other topics and i was wondering what you used for the sealing face ????

thanks again

so i was just over at Harbor Freight getting a new air reg.. and i remembered this thread so i picked up a set of the sanding drums to try as a piston for the 2'' valve on my GB cannon and i have to say this is one of the best pistons i've had in this cannon and i've used everything from- 1 1/4 Coupler w/ o-rings,molded hot glue, molded epoxy, a pill bottle filled with epoxy and by far this is the best--- so if anyone needs a good piton try this for $7 you cant find a better piston :thumbup:


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Glad I could help. I went over to Harbor Freight to pick up a few more of these and noticed they didn't have them on the shelf any more...no longer on the website, either. So heads up to anyone who may want to try one of these, I think they're being discontinued...get 'em while you can.

ould a 4" sanding wheel make a 4" piston????

ajb12345 wrote:ould a 4" sanding wheel make a 4" piston????

Very possibly, would probably be a little heavy though. You would just have to try one and see.

Yeah you'd probably want to bore some of it out to reduce weight.

Wow!! I know this thread is extremely old, however I thought I would comment for new guys looking for a easy, pre made piston. I have not used one, but I know someone that has, and he said its the best piston he has used in a 2 inch tee. I am going to try to find one tomorrow.