Matt's Monster RC Tank Project

My eventual goal with this project is to build a mobile radio controlled all-terrain platform to carry a surveillance camera that feeds into my security system. I started by researching different motorized drive options and settled on using wheelchair drives for this. I also researched how others have built tank-like vehicles and what they used to drive them along with different track ideas. After brainstorming with a friend from work, I built a prototype to test our ideas.

This concept used 26” bike tires with the wire cut out and wrapped around a series of rollers. This method work very well – as long as the vehicle moved in a straight line. However, when one track was turned off (to make a turn) it would jump track. I found no simple way to reliably correct this defect. Epic FAIL.

Weeks later, after consulting with another co-worker, it was suggested to use some kind of conveyor as a track system. After much time on Ebay I scored this!

I bought a lot of 4 of these (40 feet!) for just over $100 – PERFECT for what I needed!!!!!!

My next step was to find drive gears for it. I DID find some, but since I needed several, it would simply cost too much...hmm... what to do. I needed 1” pitch gears that were about 6” in diameter. Several. 36 to be exact! After pondering this, I broke out a little something I had built months earlier.

It's a small CNC machine I built from a kit. I found that building it was the easy part. Creating “G-Code” to run it was something also entirely. Since I am a hobbyist programmer as well, I spent about a month writing a program (in Dark Basic) that would generate G-Code for gears:

Running this program, you simply input the specs on the gear (or actually more of a sprocket), and this will create a Gcode file that the machines software can read and cut the gear. It also has options for mounting holes to be precisely placed.

I used 1/4” PVC sheets since that about the best my little CNC could handle. My awesome little kitten “Kiki” sat out with me in the shop for hours cutting all 36 gears. She worked hard!

I put together the drive sprockets first and then the idlers:

A collection of several parts in one pic:

The white ones are the idlers – same gear pattern, but has a 1/4” brass bushing in each piece with a grade 5 bolt going through. Also pictured is my first servo controller (I built a better one since), a deep cycle 12V battery, an 8 channel radio,a solar charge controller and the two drive motors.

Next came welding the frame together. I used 1” structural tubing. Kiki didn't hang around for all the welding!

Test fit:

Here's the frame painted black and skinned with more PVC sheeting:

Test fit the drive motors on their adjustable mounts:

Now, test fit the major parts together:

...note the battery pan is now in...

Next, pull it all apart and paint in a desert camo theme:

Next, started on a better servo control system. Since I want each track to be independently controllable in forward and reverse, I opted for a relay system. It very much simplified things and has decent reliability.

Some miscellaneous specs: Length 40”, width 16” (23” counting the tracks), weight: over 100lbs
Each track is about 4ft laid out straight. A 15W solar panel is standing by for the next stage of the build. After that, RC headlights then the camera system...

Issues:
I'm unsure as to how well the PVC will tolerate 100+ temperatures. Also, I >MIGHT< end up needing metal drive gears.

... many unknowns at this point....

Preliminary tests have worked well so far. I'll post a video of it in operation soon...

last update Nov 17 2013 Matt