Solenoid tractor gears or more precisely the connecting of the rotational output from the motor to the wheels. Accomplished using 1.5 mod brass gears machined using the Genmitsu 3018-pro cnc machine.

In the first part of this build I made a solenoid that generated 5x the force of the original motor.
I then created an outline of a tractor for this motor to drive.

There is a great online gear generator from Evolent Design.
This allows you to generate a .SVG file that you can import into a CNC package and from that generate a gcode file.
Here you can see lots of 1.5mod gears machined from 1.6mm thick brass using a 1.5mm diameter cutter. The cutter was a tad large in diameter, but it was more robust and the resultant gears were fine for this project.
The gears were paired up and soldered onto brass bushes that had a 3/32″ diameter reamed hole for the axle. The axles were also brass, not such a good idea to run brass on brass, and soldered to the brass backplate.

It is best to see this running and then moving. The overall speed reduction is very good and the gears run like a dream.