I started the HO - 1:87 scale monorail project. Here are the head, the cart, the belt transmission and a piece of stright rail.
I havent desigend the terminals to get the electricity from the track to the motor, as well as the electrification of the track itself - I'll do it soon.
You can find in the head an object of the electric motor - do not print it, buy a real one.
Since my printer broke, I couldn't print this, so it is not tested.
Next elements to come are curved rail, rail-changer, poles for the track and stations.