In 2009 a German gent posted a working transfer idea for a Marklin crane on Utube but his description of the mechanism was obscure.
I suspect it involved a belt under the layout but I could be wrong.It worked well and I vowed to make one. ( 9 years ago)!)
I recently saw a linear screw slide on eBay and realised it would be a good mech to use. I chose a 300mm one.
It was supplied with a large NEMA 42 stepper motor which I replaced with a Canon gear motor from a redundant ECG (EKG) machine.
An end bearing and a reduction shaft was needed to couple up with the lead screw.

The trick was how to get the power up to the moving crane. A rear concertina cable mounted on a support cable as is seen in the real thing wouldn't work in HO scale.
A flat ribbon cable which unfolded and folded I felt would fatigue and looked a bit naff.
The solution was to use a piece of PC board milled to form six contact strips and to collect the current with six Marklin carbon brushes.
A micro switch was added each end to prevent overrun. The control box uses two joysticks for transfer and crane functions.
The magnet control only requires a momentary push as it is interfaced with a latching relay.

Some photos of the construction ( not too many I hope!).







The flat connectors on the transfer base connect to the Marklin crane wires and sit nicely under the crane base plate.
I built it in a display case with perspex sides as I didn't want to place it in my layout.
It would be easy to support it under a layout and use the baseboard as the transfer table ( with suitable 5mm slot ).
A short video.

Edited by moderator 18 May 2018 19:41:36(UTC)  | Reason: Updated YT link

Hi again,
This is a much smaller linear slide with a ball bearing mounted table which I feel could be the basis for a transfer table.
30cm long with mounting holes in the table. Need to design a motive arrangement but that's the fun hey?



Cheers,
Howard.