SpudFiles

I have been slowly becoming more and more dissatisfied with my previous pneumatic model. The most significant issue that I had with the previous build was its sheer size (which lead to a host of other problems). Thus the Trident (technically renamed Aeolus's Trident to differentiate from the Trident Antenna Launcher).

Specs:
Valve: Barrel-sealing piston valve (now with internal check valve)
Piston check valve cracking pressure: 5.4psi
Barrel: 0.364” x 18” (now 0.364" x 36")
Chamber volume: 5.38 in3
C:B ratio: 3 (now 1.5)
Port diameter: ~0.364"
Max operating pressure: ~2,000psi
GGDT muzzle velocity prediction @ 1,000psi: 912fps

The main purpose of the Trident is a test facility (and entertainment ). I originally planned to experiment with different piston designs, but later concluded by simulations in GGDT that no design will have any appreciable benefit over the UHMWPE-based check valved piston it currently uses. The Trident is extremely portable, and has a very small chamber volume, actually 1.4 times the displacement of the second stage on my pump. Future plans for the Trident include evolution into a QDV hybrid. Due to lack of funds and design flaws in current QDV hybrids, development has been delayed somewhat.

The original piston design for the Trident was simply a solid steel piston with an o-ring firmly attached to the front as a sealing face. Unfortunately, the steel rod I used was significantly less than .5" in diameter, so I wrapped it in scotch tape to minimize the size of the equalizer hole. After two shots, the scotch tape had to be replaced. Not the best system. Check-valved piston made from UHMWPE with a very durable o-ring as the sealing face, and the back drilled out as the housing with a button-head bolt to form the housing for the check valve.

08/25/2010: Design is functional, now working on moving my piston stop forward, decreasing pilot volume and preventing the front of the piston from catching and shearing off on opening.
8/29/2010: Tested to 160 psi. Piston now seals at 40 psi, added a bumper to prevent damage to the piston, and reduced pilot volume.
8/30/2010: Completely leak-free up to 160 psi.
9/1/2010: First damage shots. Need something that's stable. Will be looking into ball bearings, slugs, and darts.
9/6/2010: Work on pump delayed Did some experimenting with GGDT... and it predicts no muzzle velocity increase with a UHMWPE piston having 1/8th the mass of the solid steel one I'm currently using. Gonna try anyway when I get my hands on materials.
10/17/2010: Parts ordered and shipping. Pump should be operational within the week. Expect much higher pressures and lower piston densities.
11/06/2010: Currently working on incorporating a check valve into the piston. Hopefully that'll be finished within a week and I'll have an almost maintenance-free design.
11/20/2010: Check-valved piston almost finished. The rear seal seal fits a bit tight into the valve housing so it's kinda like stuck right now. Plus I discovered today that my gauge somehow broke itself while not in use.
11/27/2010: Tensile strength of UHMWPE is terrible. By the time I'm done the piston will probably be mostly steel again.
11/28/2010: Piston very much improved. No problems up to 650psi, no replacement gauge yet so I dare not push farther.
11/29/2010: IT WORKS!!!!!!!!!

Damage at 1,000psi vs 1/16th steel plate. Amazed it didn't go through, but it was directly against the backstop(pre-check-valve).


MASSIVE UPDATE
Check-valved piston (old pictures of the failed design have been replaced):


The piston was extensively modified from the original design and build, due to the terrible tensile strength of UHMWPE and its tendency to be extruded through an o-ring.

Shorter piston travel (I went to re-take this picture then realized my scope is in the way ):


Quick-disconnect rotated, stock modified to actually be effective, 3' instead of 18" barrel, and 4x scope (The bend is a result of some crookedly machined threads, I'll hopefully be replacing the crookedly threaded part with the next McMaster order.) I rotate the stock 1/4 turn clockwise for operation, it's just set like that so it can be filled:



What I did to be able to film that. The trident is sitting in for the camera... which doesn't like the lighting. Couldn't get a clear photo, since it was focusing on the ladder.


Most impressive picture is of the first can, other pictures available on request .


Finally penetrated the steel plate, at point-blank range with a deck nail



Videos compiled to one, will be updated with progress:
[youtube][/youtube]

Very clean cannon, nice!
I dont know if you have the optimal C:B ratio, maybe you could optimise it with GGDT, as I think it's way too short.

Any damage pics coming soon ?

Saefroch wrote: The main purpose of the Trident is a test facility. I plan to use the small size of the valve to my advantage; I am now able to use a .6” drill press chuck to machine pistons from various materials.

I still have the 3ft long barrel used on my other cannon in the basement, which I may stick on there after I'm done experimenting with pistons, but for now the C:B ratio is of relatively little concern to me.

Preliminary damage pics will appear when I can get something good to shoot. I'll probably be making some sort dart or "bullet" out of steel scrap.

Looks awsome and clean, I like the piston, it is a good idea. How often does the seal blow out? Also I think somebody beat you to the name Trident. It is a hunk of DWV of a cannon that PCGUY posted a while back.

How often does the seal blow out? Not yet. It might come off if I get to 500 psi, but it's very firmly attached right now. The McMaster-Carr item # is 5308T247. I used a clamp and screwdriver to force the o-ring onto the piston.

Darn, guess I'll have to change the name. Everyone's been calling it a trident, so it'll just have to be some variation on that.

keep the name it fits. I like the layout, but do you plan on getting an hp setup to push it to its limits

Saefroch wrote:very small chamber volume, actually 1.4 times the displacement of the pump I am (still) working on (and shouldn’t be for much longer).

I broke my pump a while back and started on this project. At that point I had only pushed the pump to 360 psi. I predict with my weight that I can reach 680 psi, and my predicted dead volume should only limit me to 1,100 psi. A thread will be posted when the pump is finished. I know that I can exert 170% of my weight in force against a pump already, so who knows how high I'll be able to push this, given some time.

nice clean build, odd chamber design

i like the piston design but the oring might have issues coming off at high pressures.

how did it take you 90minutes to make just the piston? also i suggest boring out the back of the piston to reduce weight by alot improving preformace.

"odd chamber design" is intended to increase flow into the valve and look pretty.

Like I said, somehow I don't think that o-ring will come off at high pressures. It's not exactly your normal o-ring. OD: .5" ID: .25" and much harder than a normal o-ring.

90 minutes on a drill press trying to cut a groove 1/4" deep and 1/4" wide with maximum precision, then putting that cone shape on the front to help me force the o-ring on. To actually get it on I set it on the front of the piston, set it in a clamp and threw all my weight onto the clamp. When that didn't get it on all the way I jammed a screwdriver between the clamp and the o-ring and it popped on.

Bump for some damage pics and additions to the build log.

use a angle grinder to do the cutting while its in the drill press and it would have taken 1min, i used it in my 3way the first grove i did with a hack saw blade and it took 10min i was like ''fuk dat ima use the grinder' and it was way better, i finished it with a file.

you should drill out the back fill it with foam.

-_- I'm definitely using my angle grinder next time I make something on a drill press like that, took freakin' forever.

Saefroch wrote:Did some experimenting with GGDT... and it predicts no muzzle velocity increase with a UHMWPE piston having 1/8th the mass of the solid steel one I'm currently using.

I'll try reducing the piston weight at some point, but because of that prediction... it's not exactly at the top of my list.

Saefroch wrote: with a UHMWHDPE piston

lol where are you geting Ultra-high-molecular-weight polyethylene High-density polyethylene

I honestly thought it was UHMWHDPE

Well put together, the piston is particularly sexy, though performance will definitely benefit from a lighter design