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does this piston look right.

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: 8tonsemi » Wed Oct 10, 2012 5:29 pm

mattyzip77 wrote:Save yourself the time and bullshit and just get a rubber sanding drum. Unless you have a lathe its the best piston your going to get...

How much does it weigh and will it fit in the T with a bushing bolted in. Im going to do that to cut down on dead space and I do have access to a wood lathe but I don't think that will work.
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Unread postAuthor: mattyzip77 » Thu Oct 11, 2012 7:27 am

Of course a wood lathe will work for pvc. Sanding drum fits perfectly with a female adapter on the back of the tee. Also a sanding drum is rubber so its not all that hard, and acts as its own bumper. Its hard to do the bolted bushing method your speaking of cuz you have to bore out the tee with a lathe. Also I do not reccomend this method cuz the tee ALWAYS breaks or cracks sooner or later around the holes in the tee. Not to mention you have to make a oring groove for the back plug as well. I suggest you go on youtube and watch gun freaks tutorial and make the housing like that before you go jumping into one like your speaking of. Here is a perfect diagram below. Except eliminate the 2 inch male adapter and use a 2 inch thread X 3/4 inch thread reducer bushing to eliminate dead space.
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Unread postAuthor: jgrimm » Thu Oct 11, 2012 11:08 am

8tonsemi wrote:I'm also thinking of using 1 1/4 inch coupling for the piston. How would I get o ring grooves in it correctly. I only have a drill a hack saw and a dremel. Any ideas


Find someone with a lathe or table saw with adj blade height to cut your o-ring grooves. I use a table saw.

You can use a drill like a lathe, but be careful and buy a few spare couplers/caps. You'll mess up a piston or two trying to cut the grooves. I have turned a few pistons like this.

A flat ended endcap would work better than a coupler (you can get the caps that are flat on one end, they do exist). It'll be lighter and more solid than both a rod and washers or pvc coupler with plugs, etc.

I used an ABS (black plastic) cap for the piston in my cannon (I recommend ABS for the piston material if you can get the size you need, as it is lower in density, which means less mass to bust out of the rear of the valve housing during operation, but it is still durable enough to withstand accel/decel/impact).

You can lube your o-rings with a small sheen of white lithium grease to reduce wear (white lithium wheel bearing grease is what i use). You can get it at your local auto parts store. Too much grease will slow the piston and cause poor valve operation.

-Grimm
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Last edited by jgrimm on Thu Oct 11, 2012 11:34 am, edited 1 time in total.

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Unread postAuthor: jgrimm » Thu Oct 11, 2012 11:16 am

Also, not to hijack, but I have a mostly off the shelf from Lowe's or Home Depot 4" Coax piston cannon build I am going to upload in a few days (College is time consuming). If you have hand tools and a drill, it can be made fairly easily. And relatively inexpensively. Most expensive piece is the sprinkler valve for the pilot. Hardest part is grooves for the o-ring. The thing really wallops. I mention this not to hijack your thread, but because I used an endcap for the piston like I was saying in the above post and will include pictures for example, which may help you out. I also did the valve face seal a little differently than most.

Also:
Question, why the piston valve? IMHO (and I've been building these cannons for years) piston valves are overkill for smaller cannons (2" and under). I would just use a sprinkler valve or QEV. Much easier. Just stick it on, and they're usually adequate for most people. Heck, I have ran my 1" orbit for over two years at 100+ psi. 1.5" barrel. 2" tank. Thing would throw an alkaline battery to narnia and back, lol. Only had the sprinkler valve apart twice since i built it over two years ago (debris in the valve seat).
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Unread postAuthor: 8tonsemi » Thu Oct 11, 2012 1:54 pm

Mattyzip77-I think I'm just going to make both pistons :lol: Because now that I know I can use a wood lathe to make an O-ring groove it will be easy.
I'll run some test between the bolted cap and the female adapter pistons to see which one is better.

Jgrimm- I just wanted to see what pistons are like. Plus I can't to see your four inch piston gun. Thanks for your help. 8ton
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Unread postAuthor: MrCrowley » Thu Oct 11, 2012 2:47 pm

jgrimm wrote:Also:
Question, why the piston valve? IMHO (and I've been building these cannons for years) piston valves are overkill for smaller cannons (2" and under). I would just use a sprinkler valve or QEV. Much easier. Just stick it on, and they're usually adequate for most people. Heck, I have ran my 1" orbit for over two years at 100+ psi. 1.5" barrel. 2" tank. Thing would throw an alkaline battery to narnia and back, lol. Only had the sprinkler valve apart twice since i built it over two years ago (debris in the valve seat).

In my experience, there's a huge difference between a golf ball fired from a cannon with a sprinkler valve and a cannon with a 1.5" porting piston valve. When I say 'huge difference', I'm talking like 200 yards.

I'd say building a 1.5" porting piston valve is worth the extra performance over a 1" sprinkler valve. If, on the other hand, you have a 1.5" sprinkler valve, then that would be adequate.
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Unread postAuthor: 8tonsemi » Thu Oct 11, 2012 3:13 pm

MrCrowley wrote:
jgrimm wrote:Also:
Question, why the piston valve? IMHO (and I've been building these cannons for years) piston valves are overkill for smaller cannons (2" and under). I would just use a sprinkler valve or QEV. Much easier. Just stick it on, and they're usually adequate for most people. Heck, I have ran my 1" orbit for over two years at 100+ psi. 1.5" barrel. 2" tank. Thing would throw an alkaline battery to narnia and back, lol. Only had the sprinkler valve apart twice since i built it over two years ago (debris in the valve seat).

In my experience, there's a huge difference between a golf ball fired from a cannon with a sprinkler valve and a cannon with a 1.5" porting piston valve. When I say 'huge difference', I'm talking like 200 yards.

I'd say building a 1.5" porting piston valve is worth the extra performance over a 1" sprinkler valve. If, on the other hand, you have a 1.5" sprinkler valve, then that would be adequate.


I have 1 1/2 half sprinkler valve and a 1 1/2 inch dust collector valve.
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Unread postAuthor: mattyzip77 » Thu Oct 11, 2012 4:50 pm

Its cool to want to experiment and build stuff. Just dont be disappointed when your dust collector outperforms it......
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Unread postAuthor: 8tonsemi » Thu Oct 11, 2012 5:17 pm

mattyzip77 wrote:Its cool to want to experiment and build stuff. Just dont be disappointed when your dust collector outperforms it......

lol if it's really that much worse I'll shoot it with my goyen launcher :D
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Unread postAuthor: jsefcik » Thu Oct 11, 2012 8:37 pm

mattyzip77 wrote:Its cool to want to experiment and build stuff. Just dont be disappointed when your dust collector outperforms it......


these dust collector valves that us three have are so powerful, i havent seen anything out perform it
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Unread postAuthor: 8tonsemi » Thu Oct 11, 2012 9:11 pm

Jsefcik did you ever post a gun that had unisonminds valve on it?
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Unread postAuthor: mattyzip77 » Thu Oct 11, 2012 11:20 pm

Gun Freak wrote:Uhhh why is it like a foot long?? :lol:


Thats what she said!!!!! :lol: :lol:
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Unread postAuthor: jgrimm » Fri Oct 12, 2012 1:34 pm

Hey, nothing wrong with curiosity. I love building and testing valves/concepts.

I am not trying to discourage you, I promise. I was just making sure your not after a quick and easy valve built by just smacking a few pieces together off of a shelf. Because in my experience, piston valves (or typically any other custom built valve for that matter) aren't quick and easy, and in some cases, may cost more than one might expect (it may take several attempts to get things right before the valve yields
worthwhile performance. I think I made like four or five different pistons out of several different materials before i ended up with one that worked as I had initially hoped).

I've seen quite a few folks get frustrated and give up on this wonderful hobby of ours, due to trying to build some awesome valve or another and getting a bad taste in their mouth from it.

I'll get a build thread up soon with pics on the 4" coax piston cannon.

-Grimm
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Unread postAuthor: jgrimm » Fri Oct 12, 2012 1:38 pm

And X2 on that dust collector valve. Their pretty slick little valves.

You know, since getting involved in this thread, I've really been considering a 2" piston valve build. I typically don't deal with custom stuff under 3". But you folks may have just inspired me.

-Grimm
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Unread postAuthor: 8tonsemi » Fri Oct 12, 2012 2:18 pm

Hey Grimm I have been making cannons for a year now so it's a new challenge for me to try making a piston valve and your post didn't discourage me it made me want to make one even more lol. Plus you probably know the difference between the two but you used pressure rated fittings on your 4inch coax and not DWV fittings right?
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