This was quite a learning experience. Hard to print and a lot of work to make everything fit. But I dropped a 7 1/2 lbs tank from 24" on to my table several times without breaking anything. May take a couple times making shocks, but they will hold up nicely and give your tank a nice cushion to ride on.
This stuff goes with the Tank Track 2in, Tank Track Idler wheels, worm gear cases, body parts, and lots more in my things.
If you space the Idler arms and shocks 3 inches apart on your tank side rail, you can make your tank as long as you want. All of the parts are spaced so the tank track has a center 1.5 inches from the side rail. 2 inch tank track gives 1/2" clearance to tank side rail.
Parts you will need besides the printed parts. (4) 1/4"x3/8"x1/8" sealed ball bearings, (8) #212 O-rings for idlers, (1) 1/4"x1 1/2" shoulder bolt, (1) 1/4"x7/8" shoulder bolt, (1) 1/4"x3/4" shoulder bolt, (1) 1/4"x1/2" shoulder bolt, (4) 10-24 nuts, (1) 4x3/8" sheet metal screw, (1) #6 flat washer, (1) #90 Hillman compression spring 1/2"x3/4"x.035 (optional), (1) #6 Hillman compression spring 5/16"x1 1/2"x.020, for each of these suspension units. Springs, bolts available at True Value or Fastenal.
Added some additional sizes of Idler arms and shocks to play with. Can choose from 2 1/2" 2 1/4" and 2" arms. Shocks are 3", 2 3/4" and 2 1/2" eye to eye. #6 springs are for the longest shocks, use the same size spring only shorter for other shocks. Shorter arms will be able to make roller closer than 3" apart and shorter shocks will drop tank height. Have fun!

There is a PDF drill guide for the frame rails in the downloads, also other drill guides for gear boxes in the gear box listing.

Be sure to check out the instructions tab for more info.

Dec. 8, 2017: I just downloaded some sprockets and cool mag idler wheels in bigger sizes to play with. Also some different arms that hold the track idlers on the arm. See my things for more tank related stuff.

Dec. 29, 2017: Have CNC machined motor rails available to help you build a tank. This is the hardest part to make on the tank, having one will make it much easier.

Mar. 15, 2018 Their are Tank frame kits and parts available on ebay to build the fastmike tank.

For more pictures of the fastmiketank1 project and pictures of my latest projects go to fastmiketanks.com