Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 47 users online :: 5 registered, 0 hidden and 42 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

piston qn I need settled

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.
Sponsored 
  • Author
    Message

piston qn I need settled

Unread postAuthor: pizlo » Sat Mar 08, 2008 12:24 am

Well with disappointment earlier today I found out I wouldn't have access to a lahte until monday, which totally sucks ass because I'll have a compressor on my hands this weekend. My plans for the piston were pretty simple. The T is 3/4 iron
(chamber and piston housing)

Image


, on the barrel end I have a 3/4 threaded to nonthreaded adapter, which extends into the T to make a thing to seal upon. the fill/exhaust end of the T is occupied by a steel 3/4 threaded to 1/4 threaded bushing,
Image

Image

then I have a short nipple to a 1/4 T and my shrader and blowgun are hooked up to that. But that is really not important, what is is that I thought I had a great Idea, I would have a small section of my piston slide into the 1/4 hole to stabilize it, reduce pilot by about half, and keep the exhaust and chamber a bit more separated. I planned on reducing down the end of my wooden piston with the Lathe at school, but as I said I can't use that 'till monday. So getting to the point (slowly but surly) I decided to use a hacksaw, razor blades, sandpaper and a dremel to replace a Lathe. It wasn't great but It seemed good enough. I tested it, made some length changes and tested some more, the times I could get it to seal (with a bike pump) It would never Pilot, justt leak all the air out through the blowgun. This didn't stop me, as I have read up on these kinds of things. so next I put a layer of ductape around the smaller portion to make the space around it smaller. then I cut a decent sized groove into the piston about halfway through as I have hears it could make up for my biggest mistake, having next to no area on the piston face exposed to pressure. Being cought up in making the porting as large as possible, and making the piston as small as possible, I just didn't think abut that. I don't think I couldn't find a fitting on mcmaster that went from 3/4 threaded to 1/2 solvent weld, that I could alter a bit to work. and if Mcmaster doesn't have it I don't see the point of checking Home depot. Is there anythign I can do currently to get the actuation right, do I need to figure out away to have half inch pvc as the sealing face.
Heres the piston and a few other shots so you can understand my late night babbling.

The piston
Image

The piston setup without T around it (so you can see)
Image

Blurry pic to show you that theres no space on the face of the piston
Image

Ok hope that helped. here are my many questions.

If I used the lathe to get the narrow part almost exactly the width of the hole in the reducer would that help. Will making a bigger groove for the presure in the middle of the piston help. or could I add a washer around the middle to give it something to push on. Do they make Orings that small? Any other solutions are welcome.

Damn man its about 12:30 and I can't find my camera so no pics for tonight. All help is apritiated and I apologize for this post I'm quite spent so I leave you all to ponder while I get some rest.
G'night
  • 0

Last edited by pizlo on Sat Mar 08, 2008 12:32 pm, edited 1 time in total.
User avatar
pizlo
Brigadier General
Brigadier General
 
Posts: 783
Joined: Fri Dec 22, 2006 7:27 pm
Reputation: 0

Unread postAuthor: bigbob12345 » Sat Mar 08, 2008 12:43 am

Wow that was hard to understand I read it 5 times before I got what you meant. It is really going to be hard to help you without some pics.
  • 0

User avatar
bigbob12345
Major General
Major General
 
Posts: 1516
Joined: Sat Dec 01, 2007 9:13 am
Location: Mercer Island,Washington
Reputation: 0

Unread postAuthor: psycix » Sat Mar 08, 2008 7:26 am

bigbob12345 wrote:Wow that was hard to understand I read it 5 times before I got what you meant. It is really going to be hard to help you without some pics.


Agree,
Also it would read easier if you used paragraphs

Please re-write your story when youve got more time and arent going to bed :P
  • 0

Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

Spudfiles steam group, join!
User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: pizlo » Sat Mar 08, 2008 11:48 am

Yeah I see what you mean, I got a bit carried away, I'll take some pics now, and put them into the original post...
And Bigbob I apritiate your effort :)
Ok a added some pics, hope they help.
and while I'm on photoshop heres something I whipped up last night...
Image
  • 0

User avatar
pizlo
Brigadier General
Brigadier General
 
Posts: 783
Joined: Fri Dec 22, 2006 7:27 pm
Reputation: 0

Unread postAuthor: bigbob12345 » Sat Mar 08, 2008 12:44 pm

thank you for posting pics and breaking up the huge paragraph.
So your problem is that it wont fire air just leaks out of the pilot.
the reason it is happening is because the port is to large, there has to be some space on the piston that the air can push it back with and right now there is no space for the air to push on.
Make the port smaller and your problem will go away.
  • 0

User avatar
bigbob12345
Major General
Major General
 
Posts: 1516
Joined: Sat Dec 01, 2007 9:13 am
Location: Mercer Island,Washington
Reputation: 0

Unread postAuthor: pizlo » Sat Mar 08, 2008 1:30 pm

Well If thats the only solution I guess I have no choice. Thanks, I'll probably spend the next hour figuring this out. And to make matters worse I used the last of my epoxy last night.
  • 0

User avatar
pizlo
Brigadier General
Brigadier General
 
Posts: 783
Joined: Fri Dec 22, 2006 7:27 pm
Reputation: 0

Unread postAuthor: bigbob12345 » Sat Mar 08, 2008 1:33 pm

OMG you ran out of epoxy
I couldnt live a day without the stuff it is arguably the most useful 'tool' for spudding
  • 0

User avatar
bigbob12345
Major General
Major General
 
Posts: 1516
Joined: Sat Dec 01, 2007 9:13 am
Location: Mercer Island,Washington
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: pizlo » Sat Mar 08, 2008 5:21 pm

Yeah, and I was so close to making JSRs day. The epoxy tube was so close to being my smaller sealer, but alas it was a bit too big. It would have been beast if I had used all the epoxy, then the tubes. anyway you might not believe this but I'm temporarily using a sanding bit from my dremel, I'll have pics later":)
  • 0

User avatar
pizlo
Brigadier General
Brigadier General
 
Posts: 783
Joined: Fri Dec 22, 2006 7:27 pm
Reputation: 0

Return to Pneumatic Cannon Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Google Adsense [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'