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!



I like your coupling! I

  • I like your coupling!
  • I like your LMR-profiles branding! Very original & cool with your paper and glasses re-appearing! :slight_smile:
  • In your profile (linked to above), you mention that you are going to work on “Poor man’s robovision using cheap lenses and LDR’s” - I like the sund of that. last time I was working on that, I only got to make the AmandaLDR-project :slight_smile: However, combined with GroG’s sterreo-vison-work, the way a flie’s eye works with many little eyes etc… I think there is a future for that project.
  • … but what is wrong with this link: ? I strongly advice you to start on a very easy project. You have a LOT to experience & learn :slight_smile: It is fun, but it is a lot!!


Thanks for noticing the branding. I figured it would make all my projects (?) recognisable by this community. The glasses and 5mm squares are always in my vicinity, so they fit. Once I start making videos (and I really like the way Chris the Carpenter does them!), you will notice these brands again.

The idea for robot vision was inspired by your LDR posts indeed. I made quite a few complicated suggestions and I hope to, one day, research them myself… In my robotlab, once finished.

I “fixed” the link you mentioned :wink:

I know I am starting at the bottom step of the ladder. I don’t mind at all. I am in robotics for the learning. And I am on this website for the sharing.



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,
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

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

Shiz man. That whole post

Shiz man. That whole post was a thats what she said.However, that is an ingenious idea and i would love to see that in action (TWSS).


That’s very cool, I think

That’s very cool, I think I’ll be making use of that coupling at some point. I really like the ideas you have for projects too, very creative. I hope to eventually see all of them posted here :slight_smile:


all of them?

I’m not sure we get to live that long Dan!

It’s nice dreaming though.

loose coupling loses contact
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.

in action: that’s what I said!
twis week?

idea for power contacts:you

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 :)

magnets and patents

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

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

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

i think you should use the
i think you should use the wires as Nicola has shown. Else: what will happen when the tractor brakes and the trail goes forward, thus disconnecting from the contacts on the "mushroom"?

I dig Cris’s videos too,

I dig Cris’s videos too, looking forward to yours!

Regarding the link though… You should have a look at best practice :wink:

- That would be the FAQ… strange indexing ;/ We’ll work on that one day!

Who said blog-postings where
Who said blog-postings where not read?

civil disobedience

I did! I read both and doubted if I should start a project page without any robots actually running around my house yet. And I decided against. because you asked us not to. In the FAQ.

But then you went and asked me what was wrong with this link! Coming from any other guy, I would have ignored the provocation, but from you… I just gave in to my previous instincts! Justifying myself by thinking that your word trumped the FAQ.

You only have yourself to blame here Frits! 8-D

I promise to all of you that I will endavour to replace the lame project with a real one as soon as possible. And if this precedent should trigger other members in defying the FAQ laws of LMR, I will take it down myself. Just ask.