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Posted: Wed Jul 09, 2008 6:33 pm
by hoarp001
Yeah I did think of that, the base that the gun sits on has bearing runners built in. When the gun fires the whole thing slides back about 5 inches and is softened by shock absorbers. It looks cool but it helps it hold together.
Posted: Thu Jul 10, 2008 1:50 pm
by hoarp001
Heres some video for you.
I shot this afew mins ago in our garden. Pressure was 80psi with a normal tennis ball, no ice or sand or anything, just a normal tennis ball.
The target was a winebox and then some 6mm MDF board. behind the target I hung up two blankets believing this would slow the ball down. Behind that I put a large wooden packing case with a garden seat cushion over it.
Its pretty powerful at 80psi, half its working pressure.
Cant wait to get this thing in front of the highspeed camera.
http://uk.youtube.com/watch?v=dZ-sjJuqv7k
Posted: Thu Jul 10, 2008 2:10 pm
by starman
Nice damage there hoarp. You can get that tennis ball to punch through a board 3 times that thickness MDF...2 times for sure, with this gun.
Clean cannon!! The breech loader is really nicely done.
Posted: Sat Jul 12, 2008 4:51 pm
by hoarp001
Also added a third barrel support...
Posted: Tue Jul 22, 2008 12:17 pm
by hoarp001
I just fired a standard tennis ball with 100psi, 7bar.
The chronograph clocked the ball at 1192 feet per second, or 812mph. Thats 51 faster than the speed of sound.
Could this be the worlds first supersonic tennis ball?
Posted: Tue Jul 22, 2008 12:30 pm
by DYI
How many times did you repeat the measurement? It doesn't mean anything if it isn't repeatable. Remember how Spudfarm chronied his hybrid at 1.35km/s with a golfball when it usually only shoots 0.4 or so?
Posted: Tue Jul 22, 2008 12:33 pm
by TurboSuper
I thought supersonic speeds were impossible with compressed air...or are you using a different gas?
Either way, that's a pretty sweet cannon you got there.
Posted: Tue Jul 22, 2008 12:36 pm
by DYI
Supersonic isn't impossible with room temp. compressed air, you just need decently high pressure, a fast valve, and very little friction. Firing a projectile over the particle speed of the propellant, however, is not possible in a gas gun.
Posted: Tue Jul 22, 2008 12:37 pm
by hoarp001
No, just compressed air.
I have only shot one ball at 812, but I have shot several in a row that have clocked over mach1, shot three in a row at 770mph.
Going to change the firing valve for a bigger one and il do afew more tests. Il film them for you.
Posted: Tue Jul 22, 2008 12:52 pm
by DYI
Going to change the firing valve for a bigger one and il do afew more tests. Il film them for you.
Sounds good. What muzzle velocity does GGDT predict for this cannon?
Posted: Tue Jul 22, 2008 12:55 pm
by hoarp001
Er, it was 650mph at 10bar. Im using 7bar at the moment to get these speeds...
Posted: Tue Jul 22, 2008 2:00 pm
by DYI
Er, it was 650mph at 10bar. Im using 7bar at the moment to get these speeds...
That may indicate a problem. Assuming you didn't screw up the modeling, how far is the muzzle from the chrony when you shoot?
Posted: Tue Jul 22, 2008 2:34 pm
by hoarp001
about two feet.
Posted: Tue Jul 22, 2008 3:40 pm
by FishBoy
I have no idea how i didn't see this gun before now, but it's awesome that you broke the sound barrier with a tennis bal!! I can't wait until you get the high-speed footage, that will be sweet. I need to send this thread to my friend, he's making a spray n' pray tennis ball gun at the moment.
btw- I'm typing this with my eyes dyilated, so forgive any spelling errors (i'm not sure if ther are any)
Posted: Tue Jul 22, 2008 4:03 pm
by THUNDERLORD
FishBoy wrote:...btw- I'm typing this with my eyes dyilated, so forgive any spelling errors (i'm not sure if ther are any)
mE Too!!! The video dIaleted mY pupils too!
Like this:
BTW, the first shot in new video sounded like a sonic boom (cracking).
Might have been the backstop though(?)