robot design question--please help

I am trying to design a simple robot that can climb over a four inch obstacle (basically over 2 two by fours that are stacked on top of one another). I am very limited by the fact that I have to use two motors that are 3.6 volts each and then batteries. (no complicated processors, etc). the robot is to be turned on with a simple knife switch.

I have built a basic rectangle–with six 3.5 inch wheels (3 on each side) and placed a motor in the front and one in the back to run front and back wheels. I used large and small gears to increase torque. But I have discovered that this will not climb over the four inches of boards.

Any suggestions on how to improve the design so that the simple robot can ascend up and over the boards? Much appreciated.

Either get another set of wheels and elevate them up so they can get over the obstacle, or elevate the front wheels. This would be easier with chain, but you can do it with gears. Keep the torque ratio though. Also, assuming that you’re using traction wheels, wrap zipties around the wheels so they can catch on the obstacle, giving your robot even better grip.

Thanks. Any idea how I could elevate the front wheels? Right now I have a rectangle for the chasis–It’s about 10 inches long–three wheels on each side. Sounds like the idea is then to drive the robot from the rear with the two motors? Also–any ideas about whether two fears (one large and one small) are enough for the torque ratio?

You could do something like this if you want style points:

Seriously though you could use a motor to move a bar that moves around the chassis in a circle (think of a mouse trap but the arm can rotate 360 degrees). You could use the bar to vault the robot over the bump. You could use the other motor on a central tank tread to move forward and backwards and help pull it over the bump.

try leg wheels, or make your own.

really though, the larger the wheel the easier to climb obstacles.

or try a jumping robot with rubber bands actuated by the wheels moving past a point. See
this could be a cool solution…
if the whole arrangement is large enough, it could traverse the bump quite well.
Idk if that’s a bit far-fetched tho.