Sticky Piston
- daberno123
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- Location: Ohio
Today I took out my newly completed piston gun to test. I had tested the valve before, using a 1" modded sprinkler as a pilot, and thought it worked becasue of the loud noise it made when piloted.
However, after loading in a potato and squeezing the blowgun, no potato left the barrel.
It seems that my piston is sticking to the barrel, and all air in the chamber (40" of 2" PVC) is leaving via the sprinkler.
The specs on my piston valve are 1.5" porting housed in a 2" tee. The 1.5" pipe extends halfway into the tee.
I have two 1.25" caps as a piston with a sealing face bolted on using a .25" nipple and cap.
The sealing face is three layers of neoprene washers.
The piston is wrapped in a few layers of duct tape for a better fit and lubricated with white lithium grease so it slides easily.
It is piloted with a 1" sprinkler and pilot volume measures approximately 6 cu. inches.
Anyone have any ideas on why this is happening, and how I can fix it?
Any help is much appreciated.
However, after loading in a potato and squeezing the blowgun, no potato left the barrel.
It seems that my piston is sticking to the barrel, and all air in the chamber (40" of 2" PVC) is leaving via the sprinkler.
The specs on my piston valve are 1.5" porting housed in a 2" tee. The 1.5" pipe extends halfway into the tee.
I have two 1.25" caps as a piston with a sealing face bolted on using a .25" nipple and cap.
The sealing face is three layers of neoprene washers.
The piston is wrapped in a few layers of duct tape for a better fit and lubricated with white lithium grease so it slides easily.
It is piloted with a 1" sprinkler and pilot volume measures approximately 6 cu. inches.
Anyone have any ideas on why this is happening, and how I can fix it?
Any help is much appreciated.
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- Corporal
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put some grease on it... thats what I would do... maybe some white lithium grease... put the grease on the sealing face ( if thats where u think its sticking)
- daberno123
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I already did. Its in my above post.
Any other ideas?
Any other ideas?
- daberno123
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If by thin you mean short in length, then I don't think so, but how short would be too short? The piston rests in a section of pipe and I don't think there are any gaps.
- jrrdw
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Can you post some pics of it if you can. With the greese on it the duct tape shouldn't be causeing any problems. How loose does the piston fit? Any chance it is tipping and jamming? Is the barrel half way through the tee?
Last edited by jrrdw on Sun May 18, 2008 4:49 pm, edited 1 time in total.
- SpudFarm
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- Location: Norway Trondheim area
my valve it completely sealet behind the "gap" in the back of the tee. (equalizion holes (?) )daberno123 wrote:If by thin you mean short in length, then I don't think so, but how short would be too short? The piston rests in a section of pipe and I don't think there are any gaps.
hard to explain so i make some crappy diagrams..
Edit: the diagram are in (ask)
- Attachments
"Made in France"
- A spud gun insurance.
- A spud gun insurance.
lol, now you're just being mean jrrdw... Ease up on him....he's only human lol.jrrdw wrote:brogdenlaxmiddie, I should delete your post but I'll leave it for the embarresment factor! Reread daberno123 post, then reread yours and read them very carefully. I think you will figure out what I'm talking about.
Due to my slow typing brogdenlaxmiddle had edited and reposted the correction I did not see that not seeing the edit, lead me to post the above mentioned, that now makes no sense....... sorry.
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- bigbob12345
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My post did get deleted
Well there, my point is proven if you got the opportunity to read it.
But back on topic(so this post doesnt get deleted too)
Check to see if there is any sticky part of the duct tape on the outside(I probably didnt word that very well)
I had the same problem with my first piston and it was solved by adding the duct tape cleanlyer(yes I know that isnt a word).
And how tight is your piston?
- jrrdw
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Hey Bob --bigbob12345 wrote:
My post did get deleted
Well there, my point is proven if you got the opportunity to read it.
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- daberno123
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Thanks for the diagram spudfarm. I took apart the valve and my piston is like the top left one, not the bottom left. It seems to have proper equilization holes. I tested it by blowing behind the piston. The air slowly leaked through, not in a rush like in the bottom left one.
Here are the pics jrrdw asked for
BTW, jrrdw, thanks for keeping this thread on topic for me.
This is the whole valve. I am fully aware of the massive pilot volume and there is no need to tell me about it.
Piston in the housing
The porting, halfway into the tee
The piston itself
Another picture of the piston, showing how tight a fit it is. I noticed the gash in it, but it doesn't seem to be affecting its travel at all. The piston moves easily with the push of my figure.
Here are the pics jrrdw asked for
BTW, jrrdw, thanks for keeping this thread on topic for me.
This is the whole valve. I am fully aware of the massive pilot volume and there is no need to tell me about it.
Piston in the housing
The porting, halfway into the tee
The piston itself
Another picture of the piston, showing how tight a fit it is. I noticed the gash in it, but it doesn't seem to be affecting its travel at all. The piston moves easily with the push of my figure.
- jrrdw
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BTW, jrrdw, thanks for keeping this thread on topic for me.
Your welcome.
I see a wrinkle/bulge in the duct tape. I would use a razor blade and slice it up the middle, lay it flat and trim off the essex tape. That will eliminate the possibility of that hanging it up. I see the gash half way/3rd of the way around the circumference of the piston, that is a sign of tilt type jamming. If the gash ran long ways then I wouldn't worry about it.
I also see the side clearance from piston to cylinder, a bit much in my opinion. Try another layer of tape and leave about 1/32nds of a inch gap in between the tape ends to act as a equalization hole. See what happens, keep us up to date please.
- SpudFarm
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good looking, i am agree with jrrdw here.. to much gap and some sort of jamming.
do you have the tools/time to make two simple o-ring grooves in it?
i wouls have taken the time to use the dremel tool to make two grooves. one at the front and one at the back.
mabe you can try to make a piston like the one on the diagram but add a neoprene washer longer back to?
first you have to try to make the piston fit so tight you feel a slight restistance (?) when you push it. more tape!
do you have the tools/time to make two simple o-ring grooves in it?
i wouls have taken the time to use the dremel tool to make two grooves. one at the front and one at the back.
mabe you can try to make a piston like the one on the diagram but add a neoprene washer longer back to?
first you have to try to make the piston fit so tight you feel a slight restistance (?) when you push it. more tape!
- Attachments
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- don't know if you care but it is worth it if you can't get yours to work
- piston diagram.jpg (3.16 KiB) Viewed 2874 times
"Made in France"
- A spud gun insurance.
- A spud gun insurance.