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Post by hairy apple on Jan 18, 2010 19:47:00 GMT -5
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Post by squirrelcat on Jan 18, 2010 20:04:22 GMT -5
That thinkg is gonna have some hell of a range Keep it up!!
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2nd Bat
Master sergeant
Posts: 11,813
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Post by 2nd Bat on Jan 18, 2010 20:29:46 GMT -5
How are you locking the chamber in (Slide and twist?) I'm guessing you're going to have way too much leakage. Hope I'm wrong. I think this is a cool project and look forward to the updates.
With a long barrel like that if the seals are tight that little foam rocket might really sail What diameter is your ball valve? That makes a huge difference to the power. Incidently your length and tube dimensions seem more in line with a 57mm don't they?
That would be more appropriate for a wider variety of periods. Anxious to see your progress.
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Post by hairy apple on Jan 18, 2010 20:49:42 GMT -5
I am going to dremel a small notch in the rear coupler to allow it to lock in. It's not going to be fancy at all. The part that is duct taped right now is just two 2" couplers... I will be gluing them together soon. I dremeled out the rings that stop the pipe from sliding through and took a little out of the inside of the couplers to allow them to slide a little eaiser. It's still pretty stiff to slide it back and forth. I was unsure as well about leakage, I thought it was going to be a ton and had my doughts... however after test firing it if there is a lot of leakage it didn't seem to matter much. It really shoots hard and fast and far.
The ball valve and high pressure pipe is 1 inch. I like the overall size of the 37mm. The 57mm seems a little harder to build out of that little trailer. I am going to recheck the correct length of the 37mm barrel as mine seems far too long.
I'm hoping there will be a break in the stroms tomorrow so I can get some outside work done... I can only do so much in the garage.
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deacon
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Post by deacon on Jan 18, 2010 21:05:39 GMT -5
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Post by hairy apple on Jan 18, 2010 22:47:59 GMT -5
Honestly, I am pretty impressed with my little C02 and ball valve set up. It works amazingly well. I was putting nerf rockets out to the road... at least 150 yards. And we didn't put much of an angle on it as we were trying not to hit the road. The "guts" we used were from my bazooka and we just used it for testing, when we build them for this we will modify it to use paintball co2 tanks instead of the 12g co2 cartidges. In brainstorming about it we figured if we can keep the same pressure and the same volume and use a paintball rig of some sort, we can have faster reloading. The only reason for the 12g set up was for mobility for the bazooka, with this we have a whole trailer to mount larger Co2 tanks on.
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deacon
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Post by deacon on Jan 18, 2010 23:01:47 GMT -5
Mine will have a large(welder type) regulated Co2 tank running 175 Psi. I will then hook that up to my piston gun.
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biged
Master sergeant
Posts: 468
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Post by biged on Jan 19, 2010 7:47:06 GMT -5
Ball valves are extremely slow opening valves. You can double, even triple, the performance by using a irrigation valve, QEV, or design your own piston valve.
The bigger the ammo, the more volume needed. More volume needed, the bigger the valve. The bigger the valve, the better performance. The better performance, the faster the valve.
Once that is achieved, you are limited only by PSI.
///ed///
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deacon
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Post by deacon on Jan 19, 2010 19:43:41 GMT -5
Thats where I'm at, finding a fire extinguisher tank rated at 300 psi that has 3/4 pipe threads.
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Post by hairy apple on Jan 19, 2010 21:17:16 GMT -5
We'll see. I may end up changing to a irrigation valve set up. That was my original plan. However I find this set up works very well. This is more the likely going to be 90% prop/game objective and not used that much for actually shooting at anything. I can't imagine too many tanks in our airsoft games around here... and the only one who ever brings out a truck is me. This is more for fun then usefullness. The ball valve set up was very cheap as well and I am working part time right now so cheap is good these days. So far I have $6 into this project.... everything I've used so far I've had laying around other then the PVC pipe and couplers. Hopefully the rain lets up soon so I can go to work on the trailer soon.
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CptJericho
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"We got to stop the Germans from getting the secret weapons!"
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Post by CptJericho on Jan 19, 2010 21:22:13 GMT -5
cant wait to see this finished
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Post by zbear on Jan 21, 2010 19:36:09 GMT -5
think twice about irrigation valves and CO2. Most of them use a rubber diaphram. The rubber is not rated for co2 temps and tends to fail quickly. My two bazookas both used rainbird valves they were fine as long as I used a pump but then I shifted to a trie inflator with CO2 they failed after only a few shots
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petermartin14
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Post by petermartin14 on Jan 21, 2010 19:38:29 GMT -5
all i know is that looks sweet, keep it up!
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Post by hairy apple on Jan 21, 2010 20:38:19 GMT -5
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Post by hairy apple on Jan 23, 2010 19:57:06 GMT -5
I had this fancy little shock mount that I was going to use on the Land Cruiser, however I ended up reusing the stock ones when I built it. However, it was the same size as the other shock mount I used for the trailer side of the joint.... so I chopped it in half... ...and removed a small ammount from each side. Welded it back together and now it fits tightly inside the other mount. The lower tube will be welded to this mount. Then the barrel will be mounted on top of this tube. The blast shield will be welded to the tube part of the mount, that way the shield will rotate with the barrel, but allow the gun to elevate without the shield.
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Post by hairy apple on Jan 23, 2010 20:36:29 GMT -5
Barrel assembly.
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Post by dan2 on Jan 24, 2010 17:22:50 GMT -5
The only problem with this project is transportation... i dont think the state troopers would like seeing a guy with an artillery peice driving down the highway!
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petermartin14
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Post by petermartin14 on Jan 24, 2010 17:28:06 GMT -5
hahaha! yea he does have a point there.
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Post by hairy apple on Jan 24, 2010 18:32:08 GMT -5
Ah, I have that solved as well. The gun and blast shield will come apart and be able to just go in the back of a truck where hidden. The rest of it will just look like a funky little trailer and nothing scary.
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Post by dan2 on Jan 24, 2010 21:38:27 GMT -5
oh nice, i wouldnt have thought of that during the construction of it! good job!
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Ersatzjack
Corporal
"That silly Franz... he thinks we are winning."
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Post by Ersatzjack on Jan 24, 2010 22:39:18 GMT -5
Hairy Apple - from what I've seen I do believe you'll have a finished piece at some point. Looks good so far. Can't wait to see the finished item.
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Post by hairy apple on Jan 24, 2010 23:59:32 GMT -5
I could have had a lot more done by now if the weather would work with me... it's been pouring for the last week and this thing is too large to work on in the garage. I think next week is going to be cold but clear so hopefully I will be able to get some major work done.
The blast shield is the part I think will be the hardest part.... or at least the most time consuming part. I have the barrel assembly pretty much set up, but not attached yet. This project is a fun one for sure. There are a couple of real M3 A/T guns in Petaluma and an amazing military museum/store there... I think we are going to go check out the museum/store this week so I'll be stopping by the park down the street to take some detailed photos and messurments of the real deal.
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Post by hairy apple on Jan 26, 2010 19:41:06 GMT -5
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Post by fantana44 on Jan 26, 2010 20:04:41 GMT -5
wow that is looking really good cant wait to see the finished product.
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Post by hairy apple on Jan 26, 2010 20:55:30 GMT -5
Gives you an idea of the size.
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Post by Garrick Udet on Jan 27, 2010 11:53:36 GMT -5
You should really consider replacing the PVC with 2" steel pipe instead. CO2 can cause PVC to crack and explode. I'll echo biged's comments about the valve. The mortar I built uses a simple 1" sprinkler valve and can put a nerf rocket or foam mortar round 200+ yards on an 80psi air charge.
Check out the German PAK thread for more info about how I set up an HPA system with a $50 beer regulator and a paintball tank as well, it's a pretty easy system to build that will give you an output adjustable to 125psi (or higher depending on the regulator). I've found that 60-80 psi is generally optimal pressure (if you're using an expansion chamber).
Anyway, the chassis looks great (you could put your expansion chamber in the bottom steel tube as well). Good luck on this project! it's nice to see more heavy ordinance.
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Post by hairy apple on Jan 27, 2010 13:11:08 GMT -5
I may indeed convert it to a valve system. We'll see. Right now I just want to build the thing and then I'll make it work better. As far as the PVC, it's not holding any pressure at all, although I may swap it out down the road too. Today it's finally sunny so I can spend all day working on it (I work part time at night), hopfully we'll have the blast shield done and the barrel actually welded and mounted. Today should be a big day!
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2nd Bat
Master sergeant
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Post by 2nd Bat on Jan 27, 2010 13:36:00 GMT -5
This project is awesome and hopefully will inspire others. There is a wonderful replica 37mm AT gun that you can buy for $5,500.00 shipped (Some assembly required) but I suspect when done yours will suffice quite nicely for sweat equity and a little bit of money. Great job.
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Post by hairy apple on Jan 27, 2010 20:03:23 GMT -5
So far the total cost of this project has been about $60. I had to buy the PCV barrel, the U bolts for the barrel, the metel frame of the blast shield, some cut off wheels, epoxy, and some welding wire. Other then that I had all the parts around here to use for this. I have seen those replicas, they are amazing. I would love to have one... but there are a lot of things I would spend $5,500 before I bought a replica AT gun. I actually got a lot more done today then I expected. Even with some minor screw ups we got it looking like a gun. I have to pop rivit the shield to the frame, build the "skirt" to hide the suspension, mount an ammo can on the blast shield, and do some other minor things. Some green paint and it should be looking pretty good. Square peg in a round hole...
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biged
Master sergeant
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Post by biged on Jan 28, 2010 7:35:23 GMT -5
It's comming along nicely... Great work!
///ed///
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