Ideas for trailer wiring that extends and contracts?

I recently acquired an abused rollback trailer and one of my tasks will be rewiring it. 

I’m looking for ideas on how to run the trailer brake wires.  I will have a little wiring box on the front that the plug (that goes into the towing truck) comes out of.   I will run the brake wiring from the box to the axles  

but with these rollback trailers, the axles are part of a trolley that the deck slides on top of.   So the wiring will be extended to about 8’ or so normally but when loading or unloading the trolley will be locked and the deck slid back on them, reducing the distance from the wiring box to the axle to about 2’ 

i thought about some coiled cord but wanted to see if anyone had any better ideas  

Coiled cable is your best bet for simplicity and durability.  

It's how the semis do it.  Support it with a spring or two.

What about having them lay in a track that rolls out with the cable? I know I’ve seen that somewhere before. 

Coiled cord with a metal rod down the center, like on tow bars.  Alternately,  inside two chunks of tubing that telescope around the wiring.

grover said:

This ia a great solution. Used this on robots for the travel cart on a 3 arm palletizer. Very smooth and the cables are tied solid to the cage so nothing falls loose.

I did a dump trailer using a coiled cable from an 18 wheeler.  I actually found it on the side of the highway and put a regular 7-pole plug on it.

Make sure to anchor it somehow near the front.  They're pretty stiff, so using the dump feature can put a lot of stress on the connector.

In reply to oldopelguy :

I think I understand but can you illustrate it??

the trolley ends up a few feet from the front of the deck so I’m trying to picture it...   thanks!

grover said:

I love the idea but the price is pretty high unless there are no other solutions.  Unless I’m missing the affordable supplier!

In reply to Curtis :

Great gutter treasure!   I haven’t found anything super cheap but glad to hear the idea works

I used to build extendable trailers that had to run lights and hydraulics like this. I'll try to explain how.

The works were run inside a pipe. In your case, I'd say, a solid pipe running front to back. Bundle wires you need to run making a large S. If you play around with lengths and routing, you can get it to Lay correctly. Smooth, flat metal underneath to give the loose part a place to lay, away from exhaust, etc. basically, you run some extra wire to change the pivot point so it all works out.

I hope this is clear/helpful.