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my proto bb gun

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my proto bb gun

Unread postAuthor: shud_b_rite » Fri May 11, 2007 7:50 pm

This is my prototype bb gun I just put together, it doesn't look like much, but it demonstrates the power of a drink bottle. I came up with the idea after failing many times to make a piston valve, I thought it would be simpler to have something similar but actuated mechanically.

It uses a water bottle as a chamber, the bottle top is the valve, and an aluminum barrel to fire 6mm bb's at 274 fps (thats as fast as a quality spring powered bb gun).

The drink bottle cap opens very quickly when there is pressure behind it, it just takes a little bit of force to actuate it.

I couldnt find a good way to attach the end of the bottle cap to a barrel so i put the barrel in a fixed position through the wood. When I fire it, I hold the drink bottle behind the barrel (about 5mm away from barrel) and then open the cap, when the cap is fully open it connects up to the barrel so most of the air is directed down it. Some air escapes through the side but that doesn't matter because it is just a prototype.

At 10psi it will perform better than a $2 shop bb gun which fires at 48fps
At 20psi it performs better than my other crappy bb gun I made
At 30psi i recorded it at 63.1m/s (207 fps)
At 40psi i recorded it at 83.6m/s (274 fps)

I don't want to take it above 40psi because it is just a water bottle, not really made to hold pressure.

When i get the chance I will make a proper version, I hope to get over 500fps by:

Making a replica of the drink bottle top out of brass using a lathe
A smaller chamber at higher pressure
A built in mini shock pump
Creating a proper seal around the barrel
And making some kind of semi auto setup.


So tell me what you think about my design.
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Attachments
diagram.JPG
This diagram is a bit messed up. The top picture shows the valve open. The lower picture shows valve closed
diagram.JPG (15.03 KiB) Viewed 1909 times
close.jpg
Close up while the valve is open
full.jpg
I know, it looks poor
cd.jpg
Damage. It will go through a cd and through a milk bottle but its not quite powerful enough to go through a can.
Last edited by shud_b_rite on Fri May 11, 2007 11:07 pm, edited 2 times in total.
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Unread postAuthor: Mr.Russ » Fri May 11, 2007 8:25 pm

ive tried something similar to that, the pop lids cant hold that much pressure
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Unread postAuthor: super spuder » Fri May 11, 2007 8:32 pm

nice. . you should use a pop bottle. they will hold 120 psi
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Unread postAuthor: wannabie » Fri May 11, 2007 8:36 pm

cool only 40psi and 247fps? that a good result

BTW nice pump you got there
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Unread postAuthor: A-98 » Fri May 11, 2007 8:47 pm

ummm...why does your pump say something like 40 psi, and yet its not connected to the gun?
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Unread postAuthor: shud_b_rite » Fri May 11, 2007 9:03 pm

Because the needle on it wont go below 30psi anymore for some reason. I use a different tire pressure guage checker thing to check the pressure of my cannons.
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Unread postAuthor: cb4289 » Sat May 12, 2007 8:42 am

Cool but i still don't get how yall are using pop bottles. I mean to get the valve in why not use a gatarode bottle. It's twice as thick and stronger to but if it gets to cold it will shatter under the psi. I think those can go to 145 PSI but don't quote me. So please tell and others how the gatorade bottles work , they work well for combustion cannons as said by one poster on this site. Also the large poweraid bottles might work to but the walls are thinner than the gators but thicker than pop bottles. :twisted:
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Unread postAuthor: spudthug » Sat May 12, 2007 8:50 am

because he needs a pop thingy on the front..it is the valve..
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Unread postAuthor: cb4289 » Sat May 12, 2007 9:18 am

how the heck dose that help
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Unread postAuthor: shud_b_rite » Sat May 12, 2007 10:46 pm

When I make my proper one (when I find time) I will use an empty 12gram co2 cartridge as the primary chamber. This will be filled by a secondary chamber (an old paint ball tank) filled to about 200psi with air. The hardest part is trying to make a valve similar to these drink bottles, I am not good at making valves.
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Unread postAuthor: cb4289 » Sat May 12, 2007 11:45 pm

pvc welders tire valves can it work i mean welring the hole shutt with plastic
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Unread postAuthor: Mr.Russ » Sun May 13, 2007 12:07 am

i have an idea. You can ge a bit of slingshot tubing and put it over the end where the bb goes, then glue that to the bottle. hyave about a cm hanging off the end, and join it to the bottle top. Will act as a sealer,and if you poke the bb into it when it shoots it will have more power
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Unread postAuthor: simo » Fri Jun 15, 2007 4:21 am

not such a good idea there russel
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Unread postAuthor: shud_b_rite » Fri Jun 15, 2007 5:43 am

not such a good idea there russel
???

Yea that will work. But im not going to spend anymore time on it. I just need to figure out a way to make a valve similair to this that is made out of metal. Flow isnt that important, opening time is.
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Unread postAuthor: Hotwired » Fri Jun 15, 2007 6:08 am

Someone else spotted the sports caps too?

I was messing about with those caps last month. I've found one type which has the exact diameter of 15mm copper pipe and I've been fiddling with it to secure it in a copper fitting as a kind of exhaust valve for a little piston :)
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