SpudFiles

"what length would my barrel be to get .3 to 1? "

Really frickin' long!!!
Good job on it, wish I could find fire extinguishers to use for stuff....

Really frickin' long!!!

hehe...how long exactly?

Good job on it

thanks! there is like 3 comments on here and the rest are questions and suggestions and what not.. dont get me wrong i always want to improve but i like comments also!!

i have like 5 fire extinguishers laying around.. another huge one and a few little ones...my freind works for the highway and finds fire extinguishers in garbage places and washes em up for me..

mmm... you would need a 3103" barrel for a 0.3:1 chamber to barrel ratio... so yeah, its doable

just get a coupler and make a REALLY long barrel for the thing...........

make sure to bevel the rear ends of the barrels so that your projectile doesnt get caught on the ridges.....

catostrpohic hybrid failure is NOT an option

He he, I like the foot in one of the pictures. Read up on Jack Armstrong A.K.A "Spudkiller"; he has some good info on C/B rations and barrel lengths.
BTW Cool lookin hybrid!

noname wrote:Good job on it, wish I could find fire extinguishers to use for stuff....

I saw some small fire extinguishers at Lowes for about $15 and some larger ones for about $20.

yea i dont think im going to get a barrel over 200 feet long any time soon

i will buy a 10' section of 1 inch and use that for a barrel...i cant go much longer than that.

thanks for the complements guys!

EDIT.

tell me if i did this right but evbec live 1. 5 or whatever said i would geet super sonic at 3x (it said 1195fps) and more at 4x

here is 4x


Chamber length 19 in
Chamber diameter 7 in
Barrel length 72 in
Barrel diameter 1 in
Projectile mass .36 oz (10 grams)
Atmospheric pressure 14.7 PSIA
Chamber pressure 45 PSIG
Fuel-propane
Chamber fan-None


Chamber volume 731.21 in3
Barrel volume 56.55 in3
C:B ratio 12.931:1
Muzzle velocity 1332.4 fps
Muzzle energy 1141.6 ft-lbs

but the wierd thing is....it says i get 200 more fps with a chamber fan...is that correct? why would that matter...

Burnt latke did a <a href="http://www.burntlatke.com/jpg600/fan-data.gif">test</a> with and without a chamber fan, and found that it improved performance in their launcher. I assumed that such results are typical of spudguns, and thus programmed EVBEC to subtract a certain percentage of velocity from your spudgun if you don't have a chamber fan.

Now, this is a pretty poor way to predict it, but I don't have any other numbers to go by. There's a reason the tool-tip describes the feature with the wording it does.
*********************

Note that chamber fans improve performance by doing 3 things:
1) Venting the chamber, ensuring better combustion
2) Mixing the fuel-air mixture
3) Turbulating the flame-front, and thus speeding combustion

#1 is really only a problem with lazy people, and #2 is probably covered pretty well by the injection of air into a hybrid's chamber.
This leaves #3 as a source of improved performance - certainly only part of the reason they help velocity.

Now, what this means as far as you are concerned, I don't know... however, my expectation is that the turbulence increases performance mostly because it makes the combustion occur faster... an effect that a burstdisk mimics: they allow more of the fuel to burn before the projectile starts to move.

In short, in hybrids, I'd believe the "with chamber fan" values more than the "without chamber fan" numbers.
But that's just a guess.

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