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Help with piston

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Help with piston

Unread postAuthor: spudthug » Fri Apr 06, 2007 10:22 am

ok well im making a piston for my comp gun and idk how i should do it...i have already got my piston it is teflon and i have rubber to but....idk how to hook the tee that the piston is seated in up to my pipe...the piston just fits in the tee and not in the 1" pipes...i need it to seal the the barrel but move enough so it will open and seal...with the pipe into the tee the piston cant move...how small can i make the piston so it still works??i am going to only solder the pipes half way into the tee but it still only moves minimally......god someone please help me i am going insane..
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Attachments
piston 1.jpg
old ignore
piston 2.jpg
old ignore
piston4.jpg
new help
piston3.jpg
new piston seating inside 1.5 tee with the barrel half way through stopping it...need to know how to make the air go through the piston into the chamber or however i should do it....look at my last post
Last edited by spudthug on Sat Apr 07, 2007 5:46 pm, edited 3 times in total.
4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: willarddaniels » Fri Apr 06, 2007 10:50 am

It is hard to determine without being there...
The piston could fit inside the pipe or the T to work, it depends on what you want it to seal against. If it fits only inside the T, you probably seal it against the end of the barrel that is welded into the T. You could machine it so that it fits into the barrel, but it is not necessary.
Without seeing it or being there... I assume the piston isn't simply too long, the o-rings aren't binding, compression spring (if used) isn't too stiff, without the barrel in the T- does the piston slide easily?, sealing gasket isn't binding, etc.
Do you need a little longer piston and a shorter rod between the psiton and sealer?
I am not the expert on these, so it is difficult for me to offer more suggestions without knowing how you are building it, exactly. But then, most folks don't like giving away their "secret" info.
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Unread postAuthor: spudthug » Fri Apr 06, 2007 10:54 am

its no secret it is mahcined out of a large chunk of very very very hard plastic called teflon...it is machined to 1 1 thousandths to fit inside the tee...the tee is honed out so there is no stops in it and the piston moves freely...the piston is going to seal againts the barrel yes there is no spring and no orings...orings are not needed in this is is so great of a fit...but i need to know how short the piston can be for maximum flow and so it will work...i would post plans but the best thing i have close to a camera at my dads is a scanner...ill try it but i think it wont turn out good...
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: Hawkeye » Fri Apr 06, 2007 10:58 am

You have to make the piston fit the pipe... Sand it down until it slides in the pipe.
If I understand you correctly you think you can slide the piston in the T and then solder then pipe in behind it without melting it into a blob that you will never get out?
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Unread postAuthor: hi » Fri Apr 06, 2007 11:01 am

the barrel actually has to be about halfway into the tee.
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Unread postAuthor: spudthug » Fri Apr 06, 2007 11:07 am

sh*t!!!!!!!i forgot about access at it wtf!! god damnit how the hell am i going to do this....is there a simpler way??i found that 1 1/4 inch pipe fits over a 1 inch tee could i solder that on then put a 1 1/4 inch to a 1inch reducer and for the back have something screw on it for access if i needed it??? would this work??post suggestions..


edit wtf i need a whole new concept becuase if i do that i would need a stop and i still wouldnt be able to get at the piston.....omg someone help here is my setup now without the rubber i ddint put it on yet...

...pics are in main post
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4" piston valved cannon-half done..( i spilt my cement...)

Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: hi » Fri Apr 06, 2007 11:15 am

yes you could do that, but if you put a reducer on you cant get the piston out (if the reducer is on the back) if its on the front, where the barrel goes, it will be ok, assuming that you are using copper pipe.

It sounds like you screwed it up pretty bad. maybe if you gave a couple picture we could help a little more, but the way you are describing it, it sounds like the best thing to do is start over. Before you even glue/ solder anything, check and see it it fits right first.

I just had a possible brain storm!!!! you said to were soldering it right? just heat it up again and melt the solder and take it apart with pliers.

edit- sorry didnt see the pictures, ya just heat it up again with a blow torch and take it apart.
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Unread postAuthor: spudthug » Fri Apr 06, 2007 11:22 am

i kinda cant start over i spent over 150 on this gun and if i cant get a piston or anything else i am thinking on a qev...theres more effing money!!!!!!please please please someone help me...
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Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: Hawkeye » Fri Apr 06, 2007 12:01 pm

You need a reducer for the barrel side and a fitting with a threaded opening larger than your piston for the back.
Then just lathe your piston down so it slides in the one inch pipe.
I'm not sure why you thought it actually slid in the t itself.
It is probably easier to buy a one inch t with a half inch reduction on one side for the barrel and then use a bushing to take the piston side down to 3/4. That way your access port isn't so bulky and your piston can be smaller and lighter.
Make sure whatever fittings you screw into the back are threaded all the way in and positioned correctly before you attach them.
It would be just your luck to attach the fitting and then find out that fully tightening everything leaves the assembly upside down or pointing out the side.
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Unread postAuthor: hi » Fri Apr 06, 2007 12:01 pm

ill try to explain this the very best i can.

Take about 3'' of you barrel and use a bushing to put it into the tee about half
way in. put a piece of pipe the same size of the tee in there and that is where the piston sits. The way you have it now, the piston sitting in the tee itself, wont work if you want to take it out. the piston neets to be in a piece of pipe, which needs to be in the tee. this will allow you to take it out.

By the way, the barrel need to be t least 1/2 inch smaller than the tee, and it need to fit into the tee about half way. so if you have a 1 1/2 inch tee, then the largest barrel you can have is 1''.

hope this help, if you have any more unanswered questions, feel free to ask and ill help the very best i can.
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Unread postAuthor: jrrdw » Fri Apr 06, 2007 12:38 pm

I think you need to do something like this.
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Unread postAuthor: hi » Fri Apr 06, 2007 12:49 pm

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Unread postAuthor: jrrdw » Fri Apr 06, 2007 1:01 pm


Now follow my diagram to come up with what hi has done but do it with the copper and your set.
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Unread postAuthor: spudthug » Fri Apr 06, 2007 1:27 pm

i dont really understand how to do this...so i would use the piston i have??the teflon one?? and how to i get the barrel to do that...my gun is using a 1 inch barrel....and i wanted them to be interchangeable barrels...so i have to solder a female copper adapter on and that design wouldnt work...unless i had a bigger to to fit the piston into...i have no clue how this is going to work....
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Hybrid- 75% done. need to build propane holder and drill/tap sparkplug hole..
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Unread postAuthor: jrrdw » Fri Apr 06, 2007 1:42 pm

spudthug wrote:i dont really understand how to do this...so i would use the piston i have??the teflon one?? and how to i get the barrel to do that...my gun is using a 1 inch barrel....and i wanted them to be interchangeable barrels...so i have to solder a female copper adapter on and that design wouldnt work...unless i had a bigger to to fit the piston into...i have no clue how this is going to work....


Rite. all the way around. Now the discision is up to you. You could build a bigger piston for a bigger tee, that will allow the use of 1" barrel. Time to decide, the contest is coming up.
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