Noobs first gun (damage Vid)

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
bullrees
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Sun Jan 24, 2010 8:28 pm

I don't have pics of the gun because it's not painted up yet. It's a basic over under sprinkler. Will get some pics soon.
SPECS
BARREL: 1"x64"
CHAMBER: 1.5"x60"
VALVE: 1" RAINBIRD SPRIKLER WITH MOD BLOWGUN(credit to Mr.C)

Note: As we were about to shoot a neighbor came over to borrow a tool. He wanted to see this shot and then got his wife..then a friend.. and some kids so there was a crowd by the end of the VCR. The soda was filmed later. Thanks to spudfiles they all think I'm some genius lol.

............on to the damage

[youtube][/youtube]
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MrCrowley
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Sun Jan 24, 2010 9:20 pm

Not bad, if you ever get tired of pumping up the chamber, you can always cut it down to 15" and I doubt you'll see a difference in performance :P

Have you noticed how much more powerful it is with a blowgun instead of a solenoid?
bullrees
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Sun Jan 24, 2010 9:37 pm

yup and no honk...just like you said. The chamber don't take long to fill with a compressor so if anything I'll make the barrel longer. There is always some air left over now but not a ton. I have more parts to make the same gun so I'll do changes in version 2.
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jackssmirkingrevenge
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Mon Jan 25, 2010 1:02 am

Nice and lol @ the crowd at the end, it's nice to see the neighbours getting involved in a positive way as opposed to complaining to police about the insane terrorist next door :)
hectmarr wrote:You have to make many weapons, because this field is long and short life
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chinnerz
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Mon Jan 25, 2010 5:37 am

nice nice, im liken it!!.
i have always wanted to make a rifle using a valve like that.

btw where do you live?
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tghhs
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Mon Jan 25, 2010 7:07 am

Yeh well done, a nice reliable launcher is the bomb :P Look forward to the picks.

Have you put in the data in GGDT? If so i'm sure you'll either make the barrel longer of cut down the chamber.
chinnerz wrote:nice nice, im liken it!!.
i have always wanted to make a rifle using a valve like that.

btw where do you live?
Your in AUS chinnerz yeh? you'll find plenty of sprinkler valves in bunnings though all with pins in them i believe, no problem just put the hose barb off centre. I've recently modded one (i'll be putting up the launcher soon) for my pilot valve, so you can see how it's done then if unsure.

*unboarding the hijack*

What range do you get too?
bullrees
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Mon Jan 25, 2010 5:40 pm

chinnerz wrote: btw where do you live?
USA

@tghhs
I'm not sure if I'm selecting the correct valve type and my numbers are correct. If you guys can look it over and let me know it would help a ton but here's what I get whit what I think I should use.

Image

EDIT: If I cut the chamber in half to 30" I get 169 ft/s with the rest the same.
EDIT2: Also I don't know about range sry. I don't have anywhere to fire it in a strait line to find out
Last edited by bullrees on Mon Jan 25, 2010 6:02 pm, edited 1 time in total.
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MrCrowley
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Mon Jan 25, 2010 6:01 pm

A changed a few things, the sprinkler valve numbers are from what I last recall, one or two may be a bit off.

Valve: Barrel Seal
Flow Coef: 6 Cv (go to file>configuration to change it)
Seat Diam.: 1.1in
Dead volume: 3.05^3"
Piston Diam: 1.8"
Piston Mass: .8oz
Vent Diam: 0.15in
Pilot volume: 3.5^3in

Gives me velocities around 230fps, if the chamber were only 15" I get velocities around 210fps.

BTW, what are you shooting that is 100grams?
bullrees
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Mon Jan 25, 2010 7:00 pm

Thanks for the numbers Mr.C

I get the same as you (230) as is but get 183 for a 15" chamber.
Wish I had a chronometer about now :(
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MrCrowley
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Mon Jan 25, 2010 9:06 pm

Ah, I slipped up somewhere with the 15" chamber velocity, my fault :P

With a 20g projectile, you're getting lethal velocities (410fps - according to MythBusters anyway). Strap a 3' golfball barrel on there and you're looking at 620ft distance shots at 230fps, all at 90PSI. :)
EDIT2: Also I don't know about range sry. I don't have anywhere to fire it in a strait line to find out
Go to Tools>External Ballistics Calculator in GGDT :P

The drag coef. can be difficult if you have a funny projectile shape but if I remember correctly, spherical projectiles are 0.5 and for golfballs i've found that .25 is the most accurate for transonic velocities. 0.3 is probably closer but I've found it underestimates distances on a few of my cannons.

You don't necessarily need a straight line to fire it in, just a place where it is safe to fire, you can see where the ball will land (for safety purposes) and a good eye. I shoot on to the golf course behind my house when it's closed and then I just go down and look for my marked ball, find a few reference points (such as trees, creeks and sand bunkers) and then jump on Google Earth and measure the distance using the ruler tool.
bullrees
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Tue Jan 26, 2010 7:56 pm

What is the standard angle to really fire at? 42 seems to be what the external calculator likes. Is that what you would fire at to compare?

Either way a straight line of safe fire is a bit difficult in my neighborhood.
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Sniknej
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Wed Jan 27, 2010 12:21 pm

A friend of mine did some projectile-angle-velocity calculations for a physics class, and he said that with a fixed initial velocity, you can get the optimal flying distance with an angle of elevation of somewhere between 35 and 42 degrees.
Sound right?
Tobbz
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Tue Feb 09, 2010 2:26 pm

Very nice, i am excited making one myself but im too poor to afford any materials yet :?
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Wed Feb 10, 2010 4:43 am

Sniknej wrote:A friend of mine did some projectile-angle-velocity calculations for a physics class, and he said that with a fixed initial velocity, you can get the optimal flying distance with an angle of elevation of somewhere between 35 and 42 degrees.
Sound right?
Depends. If you have enough power, a higher angle will work better. As you increase the altitude the drag is reduced substantially. For example, the Paris gun could fire it's shell to 40+ km into the stratosphere- where there was much less drag. It had an effective range of around 130km at around 55 degrees elevation.
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CpTn_lAw
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Wed Feb 10, 2010 5:29 am

The "big Bertha", I had a maths analysis to do on that.... 4 years ago XD
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