ADD - I just added a Pi B+ / B2 bracket. It is meant to mount to the bottom front screw holes behind the camera, then use some plastic tapping screws to mount the Raspi
As soon as I saw the original Drogerdy tank by timmiclark I was intent on building one. Since then, I've printed the parts about 4 times and made some adjustments. My biggest recurring problem was that I had a lot of trouble getting the tracks to operate without binding and it seems like others may have had this problem as well. As this was one of my first prints, I'm sure my lack of expertise in 3D printing probably caused these issues. I also glued the first model together and maybe the tolerance were a bit off lending to the track issues.
So I made some adjustments while keeping the overall dimensions the same. I made 2 sets of cogs, one for the motor-driven cog (all the teeth) and one for the dummy cogs that just rotate (I removed half the teeth), this works wonders for the tracking issues. I added screw holes for countersunk size M2.5 screws, reduced the hub diameter on the cogs to allow for better seating of US-sourced toy motors that have a pesky nub, added screw holes to mount the motors with longer M2.5 screws and allow for locking in the nub on the motors. I used 1.5" #15 finish nails (wire brads) from home depot to link all the tracks together - they are sharp on one end, the rivets face outwards and it looks pretty cool.
In retrospect, I did go a little crazy with the screw holes, don't feel like you have to use them all; it can be quite frustrating to get them all bolted up - and use a lock washer on all your screws, you don't want your fasteners rattling around on your raspberry pi or other electronics.
Now that I've got this working, I'll be using the screw hole mounts to add on additional hardware and upload that as I am successful.
This was a great learning experience for me and hats of to timmiclark for putting the original together!
I've printed most of these parts at 50% or 100% in HIPS and PLA. I wouldn't recommend one material over the other, just experiment. Following printing, I'm finding myself chamfering the edges of the cogs (hub and recess not the teeth), holes on the body and hubs on the outer brackets to get a smoother rotation.
I still had some minor issues with tracking, for that I printed some individual tracks stretched 10% in the direction of travel (this adds about 1mm to the total length). For one track set I printed about 5 of these and the other I printed 3. I cannot isolate the exact cause of the track binding issues, but somewhere between low-torque motors, individual print differences and too-wide tolerances in the track guiding there is a problem. This stretched part printing should be the last resort but it will work!
I imported all the original STL files into FREECAD and modified those parts there. Please let me know if you have any questions or comments. I need to clean up the freecad files a bit and I'll upload those (but you cannot adjust the dimensions made in the original files, just what I added).