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37mm Anti tank gun build

49K views 153 replies 37 participants last post by  nc_reb 
#1 ·
Well I have been toying with the idea for a few years now. In that time I have slowly been acquiring materials and resources to make a wanna-be 37mm to tow behind my jeep.

47lincsled and his 57mm, as well as others have inspired me to finally begin. In the past year or so I have acquired some 1/4 inch, 3/16 inch, and 1/8 inch plate for the armor and components. I have tubing for axles, spindles, hubs, rims, and tires. I also have rectangular tubing for the trails. I am still working on barrel materials, but I am persistent.

I bought a CD with much of the blueprints a while back. The images are copies of microfilm and some of the measurements are not legible. I need the axle diameter if anyone has one.

I am lucky enough to have access to a CNC plasma cutter, so I spent about 30 minutes today programming in the large piece or armor. Gotta start somewhere....I may cut it tomorrow. We'll see. I left many of the bolt hole off, so that I can drill them where I need them. This is not going to be exact of course.

If there is any interest in this I'll keep the thread active.

Here is the results of the programming of the top armor. It will be CNC plasma cut from 1/4 inch steel plate (mild).

Andy

 
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#2 ·
I cut the armor today. I couldn't help myself. It cut so pretty, I went ahead and programmed the apron and the little guards. It is 1/4 inch mild plate.



 
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#3 ·
DANG! That CNC cutter looks like it would be dangerous! All the wacky things you could make with it, I think my wallet would catch fire just standing next to it.
 
#5 ·
Yeah, I have cut out tons of stuff. Anything that you can program and cut flat and then bend you can make. I made my m2 tripod head on this machine, as well as the spare tire bracket for my '43 Willys MB. If I can find blueprints, I can pretty much program it. If you've ever seen any of the toy guns I've made my kids, many of the parts were made on this. Tons of brackets and gussets for other metal projects like trailers, tractors, or farm implements.

Before I got my 1917a1 tripod, I programmed the cradle plates and cut them out with this. I really enjoy it.
 
#8 ·
I think I have the Traverse and elevation all figured out. It is not going to look exactly like the original but I am pretty sure it will work, and I am optimistic that it will work well. I am in the process of rounding up the parts. I have a few leads on the items I am looking for and I am excited about it. I am going to use an old screw type bottle jack for the elevation mechanism. The kind of jack that used to come in Toyota and Nissan trucks. A modified common universal should help make the turn over to the elevation knob. I think I am going to use a common trailer spindle and hub with bearings to ease the traversing.
I have a right angle gear box that has been donated to the effort but it has one stripped gear. Kind of like this one:

http://www.ebay.com/itm/STM-RMI50-P...076?pt=LH_DefaultDomain_0&hash=item51b59d64fc

I am looking for a replacement gear. My brother thinks he has another right angle gear box that has a 15:1 gear ratio. He says it is about the size of a big grapefruit. I am imagining the steering gear from an old riding lawnmower on the downward angle and the corresponding gear attached to the hub under the actual barrel carriage. It should ..... in theory....traverse as far right and left as riding lawn mower wheels.

suggestions? what have I left out or not considered? This is kind of like building an airplane while you fly it.

Andy
 
#11 ·
102.3 fever and a kick butt case of strep throat has put the build on hold....:(

Belt Fed Frog.....pm inbound!
 
#13 ·
Found some time to program the spades, supports, and a few other small parts. I also bent a few things in the metal break. I cut the trails, and managed to get one spade welded on.
Andy


 
#14 ·
Looking good so far. What file format do you have your cutting program saved as? One of our customers has a large metal fab shop (I repair welders) and they said they could cut the stuff out if i could get them usable files.

Between the motorcycle and the GPW my garage is full so I'd have no place to store this thing or any other way to move it around...
 
#15 ·
Looking good so far. What file format do you have your cutting program saved as?
I have a cheap machine, as far a CNC plasma cutters go. It called a PlasmaCam. However it does everything I ask it to. I really love it! It is a really easy program to learn. It is a simplified windows based version of cad/cam. It can read G-code...I believe it saves as PSM or PCM files. Heck I don't know. I just use the dang thing.

http://www.plasmacam.com/archive/sfsp.htm
 
#16 ·
With the beginning of school, I have not had time to work on the build until today.....I had about an hour after school before I HAD to go.
I programmed the guard plate that shields the gunner from the recoil........only one problem. I was in such a hurry to build a part to put on the "pile"....stooooooopid me.......built the thing backwards...ughhhh...
Anyway...I am not deterred!

Just to update this post I'm adding the picture of the screw up.......

I'll just cut another one and recycle the rod. What's a little scrap steel and lost time during a build...:jedicrying:

Here's a brief video of my machine cutting the plate.



Here is the screwed up part......

 
#19 ·
The shop has had one for about 7-8 years now. I think the machine itself, meaning table, servo motors, controls, and software was in the $9k range. On top of that you have to provide the plasma cutter, computer, and air compressor. I suspect there is about 12K in it.
 
#21 ·
The build continues....
I got the other trail/spade cut and welded up. It is a mirror image of the other one. At this rate it is going to take me years to get this thing built.
I have been sourcing prices for the barrel materials.....the cheapest I have found is nearly $600.....ughh. Well that is a ways down the road.
I plan on starting on the axle and support/traverse bar next.

Andy



 
#23 ·
I finally got around to cutting an axle.
I have had to cut and turn the spindles to fit the tubing. That took a while, but I finally got it. I have started making the rotating wheel chocks.
I had to turn the outside and bore the inside on the lathe to make it blueprint specific.
This is a really slow process, especially since I can only work on it during "stolen" minutes from something else.

 
#24 ·
Fabricated one of the spring loaded catches for the rotating wheel chocks. I still have to lathe the pins. I have bolts through the pin holes for now.
I also have to weld a little gusset between the latch arm and axle. You will be able to see what I mean in the photo of a real one from the svsm.org picture below my home made one.



Here is a link to a real one from svsm.org

http://svsm.org/gallery/37mm_M3/IMGP7433
 
#27 ·
Front apron armor installed on the axle. Next I will work on the latch arms and latches to hold up the armor when towing.
This whole project is going to take a year or more!

 
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