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New guy on the block needs help

A place to ask general spud cannon related questions.
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Unread postAuthor: EIGHTWGT » Sun Feb 13, 2005 3:59 pm

Here is my gun and breech end
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Unread postAuthor: EIGHTWGT » Sun Feb 13, 2005 6:54 pm

I said it dumps in 1.5 seconds... more like 3 seconds or so.

I removed the lil blower and put a sprinkler valve on it to dump the air so the piston slams back.... now it dumps in about 1 to 1-2/2 seconds.... By the way its attached to the back of the piston chamber via a 1/4" brass threaded coupling (typical compressor fitting)

It still doesnt work - just farts real loud out the back of the sprinkler valve......

Man Im lost.......... didnt look this hard !
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Unread postAuthor: EIGHTWGT » Sun Feb 13, 2005 6:58 pm

QUESTION :shock: :shock: :?: :?:

How tight is the piston / diaphram supposed to be anyway ? I mean is it supposed to be really tight ? you can slide mine with light finger pressure - its not loose but not tight either....
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Unread postAuthor: EIGHTWGT » Sun Feb 13, 2005 8:47 pm

Here is a pic of the new trigger / dump- AND the pressure gauge I installed to be positive it was charging and it was not over charged

IT STILL DOESNT WORK.....and now it dumps pretty fast but still not 'instant'

I put a 1/2" tap into it, added the rainbird....

STILL no go......... I guess I have a dia / piston problem ???

GEEE WIZZZ......... what now fellas ?? :?: :?: :?:

:oops:
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Unread postAuthor: BC Pneumatics » Sun Feb 13, 2005 8:52 pm

If your pilot is taking an entire second and a half to vent, It must be venting the entire chamber. Your piston may be too tight, but from you say, it doesnt seem like it. if it is that easy to move, it doesnt seem like the air would just come out through the equalization hole, or whatever it has. It really really sounds like your piston isnt shooting back when you fire (99% sure), but I cant figure out why, if the piston is really as loose as you say it is. The surface area isnt all that much, but it should still move the piston enough to fire the gun.
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Unread postAuthor: EIGHTWGT » Sun Feb 13, 2005 9:14 pm

I can put my mouth on the air inlet ( I know yuk) and push the piston closed with my lungs and suck it back till it seals with my lungs....

so is this design I have not likely to work ?? Is the CU IN of air PUSHING it towards the pipe to great for the push/pull force to pop the piston open ???

I am lost now.......
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Re-arrange...

Unread postAuthor: Freefall » Sun Feb 13, 2005 10:18 pm

Starting from the barrel-side, you have the barrel seal gasket (red), the support plate (metal) and the piston seal gasket (yellow). I also notice that the actual piston body is fairly narrow.

I suspect that the problem is that the piston seal gasket is flexing backwards when you try to fire, letting too much air past the piston. I'd suggest swapping the support plate and piston seal gasket. This should prevent the excess flex and should allow the gun to fire properly.
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Re-arrange...

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Unread postAuthor: EIGHTWGT » Sun Feb 13, 2005 10:36 pm

Freefall

Good observation...... however - I already tried swapping the plate and gasket.... even tried greasin it.

I put a new one on without using the steel plate in front. It was very wierd, the valve went off (sprinkler) vent most of air (all but about 15 pounds) then it slowly hissed out the firing valve and when it got to 8 pounds in the gun it fired ( I had a wadded up sock in it) It did this several times.....

Hmmm..........
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Unread postAuthor: ojhspyro89 » Sun Feb 13, 2005 10:42 pm

This is ohspyro89 from spudtech and i dont think your pilots big enough. A blowgun is very slow youll need at least a ball valve or something with better cv to empty it out behind the piston. Just hook up a ball valve like half inch or something and it should work.
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Unread postAuthor: ohspyro89 » Sun Feb 13, 2005 10:44 pm

I have no clue how to edit and i didnt see this page of stuff. If you have a lathe try making a solid piston with oring groves on it. Thats bout the best bet ive used fiber glass resin and its a cheap good alternative to buying pvc rod
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Unread postAuthor: clide » Sun Feb 13, 2005 11:14 pm

As others have mentioned it is most likely just too much leakage around the piston (maybe something flexing). I had a gun similar to that one and I had good luck with test caps. They have them at most hardware chains. They are designed to fit inside sch40 pipe They arn't terribly thick, you can see light through them. They have a lip to keep them from going all the way into the pipe, just break that off with plyers or something. Then put it on the front side of that front metal washer with the remaining lip facing forward...
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Unread postAuthor: PCGUY » Sun Feb 13, 2005 11:53 pm

ohspyro89, you can't edit because your posting as a guest you guys aren't registered :P
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Unread postAuthor: BC Pneumatics » Mon Feb 14, 2005 2:10 am

the only down side to solid pistons, is that the seem to open a bit slower, because they weigh so much more. I have been haveing a tough time finding any proper gaskets though, so I have had to use mostly solids... they work, just not as good.
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Unread postAuthor: Tim Jones » Tue Feb 15, 2005 12:34 pm

Air flow through the vent is still restricted by the size of the coupler (formerly 1/4", now 1/2"?) between the launcher and the sprinkler valve. The launcher is only using 1/4 of the sprinkler valve's venting capacity (assuming a 1" rainbird). Upping the coupler size to 3/4" or 1" may help, although I'm supprised that a 1/2" vent does not suffice.
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Unread postAuthor: pacogoatboy » Thu Feb 17, 2005 10:33 pm

Your pilot is big enough (using the sprinkler that is...) The problem is, as stated, that your yellow rubber is bending around the steel plate (there's no reason it can't bend either way, so the position doesn't matter.) Here are 2 guaranteed fixes.

To fix it cheap, use duct tape. Wrap your piston in tape until it fits the ID of your chamber loosely. You could use any sufficiently durable tape for this, but everyone has duct lying around. This will fix the seal, and the valve will work. The piston will look kinda crappy, but the idea isn't to look at it...

The spudzooka piston is a neat idea, but it's pretty problematic. If you decide to try again with this piston, you need to make your steel plate bigger. It should almost fit the ID of the chamber, and the bit of rubber will make up the difference (honestly, with a 1" pilot valve, you probably wouldn't even need the rubber if you cut the plate carefully.)

Good luck, and don't dispair, you'll love it once it works.
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