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Schrader threads to small?

Discuss miniature cannons built from things such as pill bottles and pen caps.
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Unread postAuthor: theBOOM » Tue Apr 27, 2010 7:22 am

Hey guys after doing alot of googling and what not I actually find a thread on schrader head replacement hose which is actually quite cheap, http://www.amazon.com/Sunlite-Bicycle-F ... agicweb-20, what I plan to do is order this, remove the schrader head from the hose, epoxy it to some metal pipe and make myself a mini high pressure costume shock pump.

I prefer this over buying a new shockpump beacause I would rather build it than buy it for 30 dollars, and also beacause it will make a nice compliment to the cannon.

Thanks Jsr, it took me alot of tries to actually get the cast to look good, I always tried doing it with medium viscosity epoxies but it never came out nicely until I finally decided to buy low viscosity epoxy from ebay. It's pretty easy to cast now.

I'll update you guys when I get the pump head in the mail.
Tell me what you think.
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Unread postAuthor: Crna Legija » Tue Apr 27, 2010 8:06 am

that hose wont take much pressure to burst and you have to make a check valve i think its better to buy one i got myn of ebay for $13 dellived
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Unread postAuthor: theBOOM » Tue Apr 27, 2010 3:14 pm

-_- wrote:that hose wont take much pressure to burst and you have to make a check valve i think its better to buy one i got myn of ebay for $13 dellived


I'm gonna be using the schrader as a check valve in this case, and I won't be using the hose that comes with this.

Even if I did, I probably wouldn't take my hybrid to more than a 12x mix which is about 150 psi of air needed. This is just temporary until I can get the fittings for my fridge compressor.
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Unread postAuthor: theBOOM » Thu Apr 29, 2010 9:23 pm

UPDATE: :D Bought a mini 400 psi shock pump from ebay 2 days ago, it should be here in about a week and a half. I hope I can pump air into the cannon with it. Here is a link to the pump I bought. 8) 8)
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWNX:IT

I fueled the cannon successfully at a 1x mix, it took me about 5 tries with a 1milliliter, insulin syringe to get it right. I have got it down to almost a perfect fuel air mixture (not too lean, not to rich) :o

With a burst disc on, it makes a loud pop. :twisted: :twisted:

Edit, I'm posting a video on youtube of me fueling the mini as I type this.
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Unread postAuthor: jackssmirkingrevenge » Fri Apr 30, 2010 12:06 am

Nice choice of model :) good luck with gettig it to work, what's your chamber volume?
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Unread postAuthor: theBOOM » Fri Apr 30, 2010 11:42 pm

Um im kinda drnk right now, but its about 13.5 ml if I can recall ... I use .610 ml of butane to fuel it.. I got it working with my burstidsc I think this is gonna be a beast of a hybrid ionce i get it done,
Superosonic bbs for hthe win

btw i think i measured it about 4 times with a 10 ml syringe and i got 13.5 all of the times.
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Unread postAuthor: chinnerz » Sat May 01, 2010 12:06 am

wow you measured 13.5 mL using a 10 mL syringe?? you must be drunk...
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Unread postAuthor: jackssmirkingrevenge » Sat May 01, 2010 12:07 am

PUI FTW :D

Maybe I should consider redoing the hybrid with a slightly bigger cartridge...
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Unread postAuthor: theBOOM » Sat May 01, 2010 9:32 am

I think you shuold defenently consider redoing the hybrid, it's quite simple to meter a 10 ml + chamber, of course the cartridge won't be as small as before but if you can get them to work it would be awesome.

Chinnerz I used a 10 ml syringe to measure my chamber volume... First I injected 10 ml of water into the chamber then 3ml, and this filled up the chamber all the way up, I repeated it about 3 times and kept getting the same results.
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Unread postAuthor: chinnerz » Sat May 01, 2010 7:06 pm

theBOOM wrote:Chinnerz I used a 10 ml syringe to measure my chamber volume... First I injected 10 ml of water into the chamber then 3ml, and this filled up the chamber all the way up, I repeated it about 3 times and kept getting the same results.


hahaha i know man :Di was just being a d!ick
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Unread postAuthor: theBOOM » Tue May 04, 2010 5:56 pm

Update.
My mini 400 psi shockpump came in today, it works well, and it actually does the depress the pin from my mini, but I dont know why the burst disc dosen't blow. Even if I pump it to 300 psi, the 40 psi burst disc dosen't rupture, when I disconnect the schrader valve head from the pump I hear a rush of air go out... Anyone know what's happening or what I'm doing wrong?
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Unread postAuthor: the unit » Tue May 04, 2010 7:59 pm

What are you using as your burst disk, and what diameter of it is exposed to pressure? Also how do you know it bursts at 40psi in your setup?
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Unread postAuthor: theBOOM » Tue May 04, 2010 8:03 pm

I know beacause I've tested it at a 1x normal combustion, and it poped, why would that generate anything close to 300 psi?
To answer your questions, the surface is about 1/4", I'm using normal clear scotch tape.

Any other ideas?

Update, got it to work multiple times as a pneumatic burst disc. I can up the pressure to 200 psi without getting any leaks if I manage to thread in the pump valve head correctly, the problem arises when it's time to disconnect this valve head from the schrader on the gun, when I unthread the valve head, all the air goes out for some reason, why is this happening?? :x :x :(
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Unread postAuthor: jackssmirkingrevenge » Tue May 04, 2010 11:27 pm

theBOOM wrote:To answer your questions, the surface is about 1/4", I'm using normal clear scotch tape


That's what I was doing here, it needed more than 300 psi to burst. Probably in the combustion context the added heat makes it burst at lower pressure.

the problem arises when it's time to disconnect this valve head from the schrader on the gun, when I unthread the valve head, all the air goes out for some reason, why is this happening??


Stupid question, are you loosening the "valve head depressing bit" before removing the head?
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Unread postAuthor: theBOOM » Tue May 04, 2010 11:34 pm

Um, no, is that the pink thing on the back of the valve head???

Yep, thanks JSR that was the solution, I tried a 2x about 4 times but it didn't ignite, I'm confident in my fuel, I'm not so sure the gauge on the bike pump is accurate enough to give me 30 psi of air though, JSR, have you gotten good results trying to meter air from this pump?
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Last edited by theBOOM on Tue May 04, 2010 11:59 pm, edited 2 times in total.
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