I want to study motion analysis of vehicle which is two wheel driven condition is like after certain time one motor driven will stop and other will keep on running and then how much my vehicle will skid?

I made the motion analysis of 3 wheel car which is driven by two servo motors installed on the rear wheels. I was successful in running it with the one servo motor but unable to run both the servo motors together.

I am attaching the assembly with the preliminary motion analysis setup. Please have a look in it and suggest me the changes if i'm doing something wrong.

Also let me know best settings ( in below attached pic.) to complete this motion analysis