SpudFiles

The tutorial is how to take a sheet of HDPE, UMHWHDPE or other suitable material and make a small piston with a floating o ring seal using a drill press. I was asked to produce a small piston, so I took the opportunity to turn it into a photo tutorial.

The piston on the right is destined to become someone's piston hybrid. I can't wait for the photos and a video of the finished product.

The construction of the middle piston was photographed for this tutorial.

To limit the number of photos per post this will be a double post.

To cut the groove, a sideways cut needs done. A drill press vise works great to hold a small cutting tool that can be used to cut into the side of the piston.

The groove in a piston for an o ring is called the gland. For a floating o ring the gland is deep enough that the o ring does not receive any cross sectional squeeze. The gland is wide enough the ring has some wiggle room, so it is free to float. This prevents it from becoming stuck down in the gland.

The ring is slightly larger than the ID of the cylinder so it gets some peripheral squeeze to fit. The air pressure holds the o ring against the side of the gland and pressure under the ring tightens the seal with pressure against the cylinder wall. These work great as a dynamic moving seal on a piston.

Edit: Added photos of the finished pistons.

good tutorial, now peolple has less excuses when they say they cant make a piston hybrid

couldn't you use a flat head screw driver in stead of making a mini chisel?

great tutorial btw, but just a little side note:

I'm grateful for the piston you sent me, but unfortunately, I don't think this stuff is exactly "5x hybrid material" upon the first shot at 5x, the material behind the o-ring was mangled beyond all salvageability. The bumper was a coiled 1/4" air hose then a 1/4" thick rubber washer. thanks for the help, but I think I'll have to stick to bolt+washer pistons

A mini screwdriver could be used, but I use my mini screwdrivers as um screwdrivers. A dull drill bit was a better choice for me to grind to a sharp cutting edge.

Thanks for the feedback on the piston at 5X. I was not sure on how it would hold up to that abuse. Feel free to post damage photos. Knowing what works and what doesn't is what this thread is all about.

Tech,

You'll get to your piston shape faster, and with less tearout, if you cut the corners off the square before you start to spin it on the drill press.

As so:

Hey tech, on a external website you discussed in a build log how to merge two or more pieces of plastic together, for construction of a piston.
Since i can't find the link again can i ask what kind of plastic this was?
Also do you have any idea if UHMWPE or Nylon is able to be melted and molded in one piece (in your own home).

i know you can with HDPE just heat up both sides till they get a clear layer on top then press them together.

I believe he used HDPE cutting boards.

It was HDPE. The other stuff was tried and failed. The photo you are looking for is on this page;
https://inteltrailblazerschallenge.wiki ... +brag+zone

And the photo of them being squished.


and the finished piston.

BTW: What is a turtorial ?

A slow and steady tutorial ?



Remember that old tale ? "The turtorial and the hartorial"...

Tech, if you are using UHMW, you don't need a rubber sealing face. As long as both the piston face and corresponding face are square and free of nicks or cuts, the UHMW will seal very well. I did this for my hybrid piston cannon and it never leaked.

Of course, I had access to a lathe, so I was able to machine clean faces. That being said, it would be worth a shot, as if there is no rubber sealing face, it can never be blown out the barrel!

Technician1002 wrote:It was HDPE.

The same stuff milk jugs are made of.
I wonder if anyone has tried molding a milk jug to make a block of HDPE?

Matt_NZ wrote:

Technician1002 wrote:It was HDPE.

The same stuff milk jugs are made of.
I wonder if anyone has tried molding a milk jug to make a block of HDPE?

I have been considering it.