My first mini: the Micro Raptor

[Boom_erang]

Thanks to all the great ideas I found around here on SF!

Presenting my first mini. The chamber is two Nalgene 1oz jars, glued back to back with LockTite plastic superglue (this stuff really works!) The forward jar is for storage, while the rear jar is the actual chamber. The barrel is a 12" piece of metal tubing with a 1/4" bore. At first I thought that it was steel because it definitely is not aluminum. But just tonight I tried sticking a magnet on it, and it does not appear to be ferrous material. Hmmm. Well, I found it lying around work so I'll ask around as to what it might be.

Ignition comes from a piezo element from a Scripto long-stemmed lighter, with solid wires soldered to the terminals and inserted directly into the chamber via small holes. I got the butane cartridge, tubing, and the brass tip (where the gas goes into the chamber) from same.

I used a 10CC syringe to figure out that this chamber needs about 1.5CC of butane for optimum combustion. I had calculated .9CC, but it did not turn out to be correct. Maybe my math is off... So my method for charging the chamber is to count about 2.5 seconds of butane from the cartridge. Fires every time and packs quite a punch! (video coming soon).

The ammo I made from brass rod and from aluminum stand-off posts. I used my drill press as a lathe of sorts to shape the rod into a bullet with a file. The aluminum bullet is faster because it's mostly hollow and thus about 1/2 the mass of the brass bullet.

As you can see from the damage pics, this thing will penetrate cardboard with these bullets.

The only problem is that often the cap will fuse to the jar and I have to work at it to get it off! So I added some oil and it helps. Any other ideas out there to prevent the polypropylene from fusing from the combustion heat?

[THUNDERLORD]

Cool mini. I bet the clear chamber gives a nice flash.
I like your 2.5 sec. metering system too.
I'm more into pnuematics myself but looking at this it's tempting me to build one similar.
BTW that barrel sure looks like aluminum.
I'll be checking for that video. thanks. 8)

[base45]

looks awesome how long did it take you to build? :wav:

[Brian the brain]

The only problem is that often the cap will fuse to the jar and I have to work at it to get it off! So I added some oil and it helps. Any other ideas out there to prevent the polypropylene from fusing from the combustion heat?

I could tell you the secret to cold fusion...

( kidding)

Not a Combuster myself, not even a mini-man..
But you have built this very well.

[Boom_erang]

Thanks, guys! It took one day to build, but a couple of weeks of collecting the parts for the gun and ammo, the glue, etc. I had the idea for the structure a few weeks ago... And fortunately, the only purchased item was the Scripto lighter! The two Nalgene jars were part of a "travel kit" we had bought years ago.

Thunder - the barrel is def. not aluminum, although it may look that way in the pictures. I have access to aluminum tubing as well, and it looks very different than this and is much softer.

I'm working on some dart concepts, and also some way to keep the bullets (or other smooth ammo) in place at the back of the barrel until ignition.

-B

[lockmanslammin]

Nicely done man. I built one somewhat similar, but yours is much cleaner. I use the same way to meter, but I do it in two one second bursts.http://www.spudfiles.com/forums/my-firs ... 13804.html

It looks like your barrel uses more of your chamber than a lot of other minis out there including mine. Fun to shoot in the dark. Try airsoft bb's in it. They are 1/4" and should fit good.

Nice projectiles by the way, looks like you put some tlc into them.
Mini's are silly, but fun.

Lock

[FordGtMan]

Nice! Love the ammo. Once you get bored of regular combustion, take that barrel with that ammo and make a mini hybrid. you already have all the syringe techniques down, it just needs to be taken to full potential...

[STHORNE]

That is awesome! A lot better than my first mini lol.

You didn't by chance use my tutorialto make it did you? lol

Again, very nice job!

[mikemurph]

how many seconds of butane, and at what level?

[irisher]

Check the date mike!