Let's Make Robots!

tractor-trailer coupling with power transfer

This is an idea for two (or more) cooperative robots. One passive bot (with wheels, but without motors) and one active bot (with motors). The motor-bot (the tractor) would pull the lame bot (the trailer). The trailer has a power source on board. The tractor wants to recharge its battery from that source.

The big idea is so big, I won't even mention it here. Yet.

One of the necessary and mission-critical components would be the coupling of the two machines. In my design I want this coupling to be strong enough for the pulling AND I also want the two bots to share electrical power through the coupling. The mechanism must be robust and reliable. I want the tractor to be able to perform the entire coupling maneuver without my help. And also the de-coupling. So the coupling must also be fool proof.

Look at these designs made in a rapid prototyping material called pizza box.


That was the initial flat version. The red/black markings indicate where I would place conductive materials (e.g. copper plating). All the rest is electrically insulating (wood, plastic, chewing gum).

I recreated the "mushroom" in a taller version, so I could actually test the coupling/decoupling.



Here is how they "work".




And here you see how well the coupling works (even I were surprised) when the approach is not perfectly aligned.



Feel free to use these designs, even when I do not. Also feel free to post your results on LMR!



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This looks like a cracking project. Your coupling looks like a real winner, even from a mechanical point of view. Insulation is going to be entertaining for you from an electrical POV.

Can you please write a walkthrough on how to obtain free samples of your "rapid prototyping material"?

Darn! I totally overlooked the insulation! The terminals one one robot must not touch each other. They would short. Not a big deal on the tractor with its solid state mushroom. But the trailer might close its jaws and the terminals might touch.

About that walkthrough: if it is not with you within 20 minutes, you will get it for free!

Blessed be the delivery man, for he does not know that he delivers two fold greatness, Greasy Fuel for the Creator, and Materials for the Creator to make cool stuff with!

That's pretty innovative Rik,

I like it, but I just have to ask a question.  How would you deal with the "loose" electrical connection when the coupler is slack, or just not under tension? Like when backing up, or coasting?

Duane S

Wilson, North Carolina  USA

The final implementation will have to provide some extra tension. Maybe a spring from bot to bot. Or in this case, from the pivotpoint on the traailer to the mushroom on the tractor. The whole idea  is based on the desire to keep the tractor part as simple as possible. So the spring would be attached to the trailer side.

idea for power contacts:

you could have two wire coming from both side, and having a small magnet so that when the joint close, the magnets will attach and keep the wires connected.

Here's a representation made with my Advanced Mechanical CAD Software:


The magnets should be weak enought to be easily separated when the robots disconnects.

Btw, your system looks great, is it original or you based on something you've seen around ? Maybe it's worth a patent :)

Your design will not allow my tractor to pull the trailer. The magnets would release before the train came in motion. Or vice versa, magnets would never release, because pulling would set the train in motion. You cannot have both without some sort of control.

Patent: Maybe! It is not directly based on anything I've seen before. But I did take a look at (model) trains, cars, tractors, trucks of course. I even considered checking out pictures of spacecraft. But I decided that I needed a cheaper alternative that could be autonomous.

Maybe I could use the magnets to overcome the problem Duane suggested: loose contacts when the train is coasting or reversing.

yes, i meant just for loose contacts, not to replace the whole joint :)

btw, i just taken out my old Geomag set and it looks perfect for such task.Couple a pair of bars, and voila' :) 

I guess I'll disassemble a Mac for parts then! How much do they go for?