SpudFiles

This is my first hybrid. I hope you like it.

Barrel: 2,5m long, 26mm ID, 28mm OD
Chamber: 20 cm long, 2'' diameter (about 660ml)
Ignition: Sparkplug + Stungun
Burstdisks: Alu. foil
Ammo: 200-500g lead
Mixes: 8-18x

I built this cannon about 5 months ago. Back then i had to use my bikepump and was limited to 10 bar.
Using a 243g lead projectile at 8x my Chrony measured 62m/s which should be ~470 joule if my math is correct.
A few weeks ago I finally got my fridge compressor and now I plan on taking it up to 20x.
I was only able to fire it one time at 18x because im having trouble sealing it above 16bar using Alu. foil as a Burstdisk.
Maybe I will try soda cans or something else next time.

Greetings from Germany


Videos
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Awww... (Wait for it) Some!
6reat job on the cannon and congratz on getting a fridge compressor.
I wish you the best of luck with the 20x shots.

In the first video, what happened with the barrel?

Welcome to SpudFiles!

vince wrote:Using a 243g lead projectile at 8x my Chrony measured 62m/s which should be ~470 joule if my math is correct.

Your maths is correct, but that sounds very low for an 8x hybrid with a barrel of those dimensions. As an off the top of my head guess, I'd expect 3 to 5 times that muzzle energy.

This may be indicative of either a problem with the chrono (possibly how it's being used) or a performance inhibiting factor in the cannon, like blow by in the barrel, slow burn rate, bad fuel mixes or a poor C:B ratio.
On the note of C:B ratio, I have to say that from the pictures, that doesn't look like a 730 ml chamber - it doesn't look like it's 30 cm long.

This is impressive, but I'm sure you can get more out of it.

That is one beautifuly splattered lead round! Put that little guy in a shadow box.

You should look into making a stand that can absorb the recoil with a set of springs or something similar. I'd hate to see that thing fly back and do something unexpected.

Thanks for your replies
@MountainousDew
Well to be honest I have no idea how it happened.
In the first video I was using a barrel with an ID of 16mm and a steel ball as a projectile.
The ball fit really nice and tight in it and I shot 20+ time with balls of the same diameter before it happened.
Maybe the barrel had a slight dent or dirt got in there somehow? I really dont know.

@Ragnarok
You are correct. The chamber is in fact only 20cm long and has a total volume (with the T with the Sparkplug in it)
of 660ml. Im sorry I got it wrong and I edited my original post.

Im really having some problems with my Chrony at the moment. I measured at least 8 shots with similar projectiles (240-250g)
at the same mix and I got readings from 63m/s to 250+m/s so I assumed that when I got the high readings the Chrony was too
close to the end of the barrel and that screwed the measurement. So I just went with the lowest reading of 63m/s

@Gaderelguitarist
Yeah I already thought about something like Larda uses on his beautiful hybrid to absorb the recoil.

MountainousDew wrote:Welcome to SpudFiles!

Thanks!

Awesome cannon. I love the rounds! Dude, that thing has kick. Convert it to hand held!!

wow that is a real gun
try replace the copper barrel with steel one ,for the safety
and welcome to the spudder world

no, copper fine. It is smooth on the inside, and still has a failure pressure of at least 2000psi.

excellent cannon, but be careful with high mixes if you used sch40 pipe.

MountainousDew wrote:Awww... (Wait for it) Some!
6reat job on the cannon and congratz on getting a fridge compressor.
I wish you the best of luck with the 20x shots.

In the first video, what happened with the barrel?

Welcome to SpudFiles!

I'll take a shot at what happened to the barrel. I think he went from a flame front to a detonation in the barrel from compression shock ignition ahead of the flame front. It does stuff like this in small areas and it is dangerous.

A little knock occasionally in a car is one thing. A larger detonation can do this. The localized area indicates this was a detonation and not a spec of dirt that would have created a scuff mark inside or ripped a lengthwise tear.

I'm voting on this is an example of detonation in the barrel.

Are there any more plausible explanations? As tubing is drawn, it is very unlikely to have had a thin spot.

****Koff Koff** I've had unapproved (illegal) propellants do this to copper in the past long time ago ****koff Koff***

tech do u have the flu

by the way great build ,incase the barrel with steal just incase `boom'
need to geat around to a hybrid rifle

twizi wrote:tech do u have the flu

by the way great build ,incase the barrel with steal just incase `boom'
need to geat around to a hybrid rifle

No .. trying to hide from moderators.. mentioned illegal activity.. Shhh. We don't do that anymore.

Well, the lowest reading isn't necessarily the correct one either - muzzle blast can screw it either way with the higher velocity gasses of hybrids. Personally, I'd take figures in the 110-140 m/s range as likely with a cannon like this.

Finally a guy who would take the lowest reading instead of the highest
Great work on getting a working hybrid!

I will use a Steel Barrel as soon as I can find one that is smooth on the inside. It would also be nice if I can find one that has the same ID as my Copper Barrel because a friend just sent me a Picture of some
sweet 26mm Steel Projectiles he made for me
They are between 70 and 80mm long and weigh 250-270g.

what kind of friends do u have

ps wish i hadfriend that made sweet ammo