Hi Kevin,

It can be done using KD delayed action couplers and magnets, or the servo operated tension locks from Keen Systems (if still in business). You need to swap the steel axles for brass or plastic on the wagon/van if using KDs, and use a van for the Keen servo and the decoder, and of course some means of moving/pulling the wagon off the table. Coupler on an actuator arm works. There is a You Tube of this in action, along with how to keep the wagon in one place on the table. An important point, you do not want them rolling around.

If you want a static cameo it's easy ("bit of scrap and a file" as Martin says) but a working one can be a challenge (£££) if you want it hands-off. 

I found some photos of these in sugar mills, so you never know. One may appear on my layout. Plus they are used to move diesel electric bogie/truck assemblies around in factories/repair shops. Never knew that.

Nigel

Hi Nigel. Thank you. I am beginning to appreciate that . Meanwhile I have so many other jobs to be getting on with, but all I want to do is catch up with sleep 💤.   Best wishes Kevin