I just can’t get it patented!
(Something about "a train" already being a different sex thing)

I’ll make a kickstarter (or similar better provider) about it.

It will run on solar energy & get up to 30kmph, so spankers need only to hold out their hands or paddles & the little TrampTram™®© will provide them the spankees butt already presented at desired speed.

If I lived in the USA I would market this as a judicial and prison tool as well, public spankings is a tradition we gave up for no good reason at all.