13 replies to this topic

[munson20]

I am making a homeade plunger, and I am having trouble getting it so there are no leaks. I sand it down around so I can put on O-rings but I don't do it perfect, so some parts are too far in, and others just right. Is there a way to fix this?

[Carbon]

The problem you're having is exactly why most people work with sizes that naturally nest in each other (.5" sched 40 and 1" thinwall, .75" and 1.25")...sanding down is tough work anyway, and nearly impossible to get consistent by hand.

What sizes are you trying to make fit?

[munson20]

No, you don't understand. I make crevices where O-rings go, but the depths they go in are uneven, so it doesnt make a perfect circle in the cylinder, which allows air to get by instead of suction.

[Carbon]

Oh, I get it, you're making channels for O-rings. I've had the best lucking doing that by using a metal cutting wheel on a dremel, and then using a round rasp to clean out the channel. You'll still have to eyeball it, but you can sand until the rasp is a consistent amount down the channel.

[Flaming Hilt]

I think somebody posted this a while ago but I can't seem to find it. Anyways, it's what I do:

Cut an endcap in half (the endcap that'll go on your plunger... IE 1/2" End for 1/2" Plunger).

Put the end half on.

Now, wrap tape (I use e-tape, usually) around just behind the 1/2 of the end cap until your O-ring fits perfectly over it (you'll have to slide the O-ring on the long way because of the end cap).

Take an exacto knife and cut off the excess e-tape (the tape not used to hold out the O-ring).

Put the back half of the endcap on.

Add glue if you like. Lubricate. Enjoy.

- - -

Another thing you have to be sure of is that you have the right size O-ring. Too small is... too small, and DON'T SAND ONE THAT'S TOO LARGE. It'll leave residue and the texture won't slide as easily. I've had many problems with sanded O-rings. Make sure you get the perfect size.

[munson20]

Carbon, your idea sounds great, but can you translate a little into something I can understand? Maybe pictures of the tools?

How did BoltSniper do his? I was looking at the scar-n and Far, and they both are perfect!

Edited by munson20, 11 November 2006 - 11:09 PM.

[Carbon]

These are the two tools that I use for channels:

Here's the cutting wheel. A small diameter wheel makes it easier to cut a shallow slot.


I have a small round rasp that I got in a set of diamond files for something like $5. I've always called them rat tail rasps. This isn't mine (the one I have is smaller and less tapered) but this gives you the right idea.

[Meaker VI]

Carbon, your idea sounds great, but can you translate a little into something I can understand? Maybe pictures of the tools?

How did BoltSniper do his? I was looking at the scar-n and Far, and they both are perfect!

I'm pretty sure he did what Flaming Hilt said; he cut an endcap in half and then put the back part on his pvc, then the o-ring, then the front of the cap and glued it all togeather.

You could also try Captain Slug's plunger head, which he posted somewhere... I think it was on the mods page and involved longshots. It was two washers with a neoprene fender washer sandwitched between them with a bolt/screw holding the thing to the plunger rod.

[six-five-two]

Carbon actually made the rubber washer plunger head in the SNAP.

http://boltsniper.co...ap-1/SNAP1.html

Here's Captain Slugs: http://nerfhaven.com...?showtopic=7664

[Gyrvalcon]

I did a Tutorial on how I make them a while ago. It's the same method that Flaming Hilt brought up.

[bigpinecone]

I have an idea, just spin the pvc you're planning on turning into a plunger on a lathe or other thing that will spin it. Get a piece of sandpaper and fold it in half, but don't crease it. As the pvc is spinning, put the sandpaper folded side down onto the pvc until it sands a channel the perfect size for your o-ring. Let me know if anyone tries/has done this.

[InkJet]

Well, on a metal lathe, i did this. I didn't use sandpaper though, I used a cut-off bit, it basically makes a
1/8" wide groove, and if it's not deep enough, i just push the bit in farther. It worked in my Boltsniper GNS great. I'd recommend it to anyone who has a lathe.

[bigpinecone]

I'm acually in the process of making a small "Lathe" from scraps of Balsa, a few Motors, and a 9-volt battery. I currently have the beginning set up sort of a "Grinding Wheel". Soon I'll post how to make it on Instructables(http://www.instructables.com/).

[SHADOW HUNTER ALPHA]

If you finish the lathe, post the revolutions per minute. If the thing is safe and practical, I'll probably wind up using it for my shotty.

Edited by SHADOW HUNTER ALPHA, 09 December 2006 - 07:00 PM.