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Later last night after I got out of the shower, I went back in the garage and discovered that if I pumped air AND dumped the meter at the same time, I got a much better explosion. Since the air and propane use the same nozzle, pushing them both through at the same time seems to mix them better.
Sadly, I made this discovery naked since I had just gotten out of the shower. (Insert ball joke here)
I'm going to have to work this into my design.
Also, I nearly died laughing when I accidentally left a plastic plate with some cake on it in front of the barrel. It took me a while to find the plate, and there was icing everywhere!
All the most important discoveries are made while naked - The famous Archimedes principle, catching hot oil from the frying pan in the crotch area hurts, Strip Poker, the works.
Indeed, that's why all when I'm holding a brainstorming session the people who don't come up with any ideas have to get naked.
You'd be surprised at how many more ideas and suggestions this technique produces.
Does that thing kinda look like a big cat to you?
rag, are you loosing it now? So next time i think of semi auto guns ill strip down...ahem
"Did you ever stop to think that out of the seven deadly sins envy is the only one which doesn't give the sinner even momentary pleasure"-George Will
So the first thing you do when getting out of the shower is to fire a spudgun?
Im sure that that technique will motivate people. If I just knew that last week...
Though if it were for world of warcraft or any other game like that, keeping your clothes on raises your intelligence...
Testing showed that injecting the propane and air at the same time through an orifice improved combustion.
I'm now going to actuate the valves using the pressure from the purge system. This allows the valves to be mounted anywhere. They have been re-located to the grip which is now also doubling as the metering tank.
I've assembled 90% of the fuel and air pump system. With the exception of the valve actuators and a couple of fitting substitutions, it is complete.
The air pump check valve system is going to be crammed into what was originally going to be the metering tank.
I'm very close to ordering the plates and the aluminum extrusion. This is it. My wife is in the final week of her pregnancy and I just sold my old car to fund the rest of this project.
Nice! Thats looking very awesome!
Good luck with the construction, and also good luck to your wife.
I got my quote back for the aluminum and UHMW plates. With tax it comes out to $99.89. Not bad considering it's 6 different pieces from two different materials.
They are officially on order, and I'm hoping they will be ready next week!
I also ordered a new 0-30psi pressure gauge, the 3/4 nut for the purge cylinder and the two valve actuators from Clippard.
Also, last night I soldered and pre-wired the ignition button.
All that is left is some minor hole drilling, ordering the aluminum extrusion, and collecting the fasteners.
My wife is due any minute, and I have a feeling that I'll be putting this together during my paternity leave.
Just for jollies here's another model pic!!
Here is what the actuators look like:
The aluminum plates are done and ready for pickup!! Unfortunately, The UHMW plates won't be done until Friday or Monday.
I've given the purchasing agent my aluminum extrusion shopping list. Hopefully that stuff will come in by Friday too!!
Now that I am in the final stretch, I'm trying to decide what color to paint my plates. I could leave them raw sanded aluminum, which looks good, or I can add a splash of color. Also I'd like a color that says "I'm badass" at the same time is says "I'm totally not a firearm" so the ATF does not show up after I shoot this thing in my backyard.
The red ties in the already anodized grip.
The yellow would allow me to put yellow and black striped safety tape down the sides of the barrel making it look totally industrial.
The pink screams....I don't know. It sure would be funny though.
I now have the aluminum plates, the UHMW pusher and ball guide in my possession. I don't think my 80/20 parts are going to come in today though.
Editing sucks. I'm dropping the pics but no one is listening. Someone bump this. Then again, aluminum propane tennis ball repeaters are so last year.
My aluminum extrusion has arrived. Assembly begins tonight.
The cannon has been fired.
No pictures. I was up again until 1:30 working on it. No time to play photographer.
It shoots, but it's wildly inconsistent. One shot it goes "phissssssh"-"damn" and the ball drops out the end, and another goes "BLAAAAAAM!!!!"-"HOLY F****** DONKEY CRAB MEAT D****LE A** PUDDING!!!!" and punches a hole through a double wall cardboard box on the other side of the room. This is where I stopped and turned off the light.
I think it has to do with the oxygen initially in the chamber. After the first shot, the only oxygen is what I inject, the open ball slot and what the bolt displaces when it moves back. Quite a bit when you think about it.
I kept an eye on the metering tank fill pressure (that's how you know how much fuel you are feeding) but I DIDN'T keep an eye on if it was dumping. This morning it looked like the dump valve's actuator line was crimped on the box I was sitting it on. If it was obstructed, the fuel dump valve may not have been operating correctly which may have caused the inconsistencies I experienced. If this does not fix the problem, I may de-couple the air cylinder and operate it and the fueling valves manually.
Despite the problems I am exited about the last shot last night even though I'm pretty sure it destroyed what ever was in that cardboard box.
I got the cannon to fire over lunch today, and man did it fire. Here is the problem though. I have to pump it twice for one ball. Despite trying every metering tank Psi from 5 to 25, I just can't get it to run consistent with one stroke. Running it with TWO strokes however works great: Air, Air+fuel, Air, Air+fuel.
I think it is a volume problem, rather than an A:F problem. I can stroke it 20 time and still get a good shot, but stroking it once just results in failure. I'm going to try reversing the fill/purge valves so it Air+fuels as the bolt is opening, and just blows air as the bolt is closing.
There is also the possibility of using a larger air cylinder with more volume and then upping my fuel amount. The problem with that is that the cracking pressure of my check valves is between 2 and 4 psi. Just to crack the check valves with a 2" bore air cylinder would require almost 10 lb of force. You also have to deal with o-ring friction and the slide guide friction which honestly has been problematic.
Still, it sure is damn skippy when rack this beast and the ball falls right in and then jams into the chamber with satisfying "chick".
well that was possibly one of the most useless posts Mongloid... but at least it served the purpose of bumping the thread.
Wow, absolutely amazing, I must say. Really nice work. I like the concept of painting it yellow, with industrial tape etc.
The inconsistencies are the main issue with your current setup. Unfortunately there is no real reliable way to completely vent the chamber, without a fan, blowing through it.
Still, I am very impressed by your work. When you get a chance, post a video, cuz I want to see this in action!
Do not look back, and grieve over the past, for it is gone;
Do not be troubled about the future, for it has not yet come;
Live life in the present, and make it so beautiful that it will be worth remembering.
There are still some things that need to be polished out, and it doesn't work the way I wanted it to, but it does work!
It's sooooooooooo daaaaaaaaamn heeeeaaaaavvvvyyyyyy. My arm is killing me from shooting it yesterday.
I'll throw up a video up later.
Last edited by chenslee on Tue Apr 07, 2009 11:42 am, edited 1 time in total.
Wow that's awesome looking.
What's the total weight of that beast? Looks like it needs to be mounted on a tripod or something...
Any videos of it shooting/damage pics yet?
I love the work there chenslee...very industrial...Terminator looking. Looks like you're paying for it with weight though.
Still, looking forward to some performance vids.
Ooh so shiny. I like it!
How much money did you put into this project?
Maybe it isnt an issue with your pumping system, but:
Have you thought about purging the fuel meter with propane? This may explain the inconsistency in your shots. If there is air in your meter, you are injecting less propane then intended.
WOW... just WOW... i assume this isn't your first venture into spudgunning? because you don't really see new members rocking up with something this impressive!
and as for the colour... definitely pink! it will lul people into a false sense of security... then it goes BOOM! and they crap themselves
HAHA, thanks for the support guys!
I put about $475 into this.
Weight. Oh. Man. I think I'm pushing about 35 lbs. You can aim, shoot, and carry it but I am very sore from shooting Saturday.
As for air in the metering system, after 30 or so shots it's been purged.
This technically not my first cannon. I built a PVC hairspray cannon a million years ago, but I never attached the barrel. The only thing it ever shot was wadded up socks across the room. I also built a 1" bore CO2 cannon out of steel pipe, but the seam in the barrel sucked and although I shot a couple of spark plugs out of it, it was so inefficient I only got about 10 shots out of a 20oz CO2 bottle. I never re-filled that bottle.
I've been kicking around the idea of making a repeater for years. It still has some issues to work out, and the next one will be a different configuration, and hopefully lighter.
Well. Here it is. The ball feed still isn't working right, so it's still a work in progress.
Last edited by chenslee on Tue Apr 07, 2009 7:36 am, edited 1 time in total.
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