Hi Daniel,
The Thomas toy uses four AAA rechargeable batteries, that power an inexpensive 3/6 volt can motor with a plastic worm and wheel drive to the axle, the axles are coupled using 'V' pulleys and a spring wire belt (Wilesco type), R/C is fitted.
The toy was bought from a charity shop for a few pounds. it is a push-along toy and the eyes move when pushed and it had a sound system.
I can post a couple of photographs if you wish.
Take care. Tony.