Hi Robin2,
I wont have any trouble with the mechanical side of things, I've tinkered with mechanical things all my life.
Lets forget about stopping the carriage whilst a shot is taken. I can't see that it will make much difference. I'm not a photographer, this project is for my son who's right into it.
Help with driving the carriage forwards and backwards at variable speeds, would be appreciated.
I shall look back through some of your replies to look for stepper motor control ideas.
Thanks,
Ken