[Algorithms] Turing machine question

[Danny K. <dr...@we...>]

I've been making a small game about Turing machines, which features a
programmable robot that moves boxes around on a straight track, and I'm
wondering if anyone knows the answer to this question:

My robot works very similarly to a Turing machine, with one exception: it
can pick up and move boxes, but it can't create or destroy them. So if there
are 8 boxes on the track (equivalently, if there are 8 1's on the Turing
Machine tape), there will always be 8 boxes (one of which may be being
carried by the robot). Does anyone know if it's possible, given sufficient
boxes to work with, to make a universal TM using this system? My instinct
says no, but I'd be interested to know if the problem has been analysed or
has a name.

Thanks
Danny