Tether Management System (for poly rope tethers)


We have decided to to go with making a tether that consists of (buoyant) 1/4 inch hollow braid poly-rope. This was done in order to provide the wire tether with some amount of buoyancy as well as to provide a secure means of retrieving the OpenROV in the event of total system failure.

In addition to constructing the Rope/Wire Tether, we built an inexpensive, easy to build Tether Management System (cord reel).

We have provided the following links to the written accounts of the processes that we used to build our Tether and Management System.

Part 1- Covers the construction of the Rope/Wire Tether: Tether System Part 1.docx (3.2 MB)

Part 2 - Covers the construction of the Tether Management System: Tether Syetem Part 2.docx (2.7 MB)

Blue Robotics/OpenROV 2.8 Hybrid ROV

nice work- thanks for taking the time to document and share.

i was wondering how these cheap ebay/amazon sliprings will hold up in use.
Let us know how it performs in the field.

Best Regards


There was a question about the size, manageability, portability of this reel system. I transport my OpenROV and Computer in a Day Pack sized backpack. This reel system fits quite nicely in to a second small back pack, as shown in this photo. The reel system and tether together weighs about as much as the OpenROV alone weighs, so weight is not a real issue.


I like this approach with a hollow poly-rope very much. Did you already test it in the water? How does it perform?


The poly-rope gives the tether a bit more buoyancy than with just the wires alone. In salt water the buoyancy is slightly better than in fresh water. The poly-rope provides good protection for the tether wires and also provides a good strong means of recovering the ROV if needed.


I discovered after testing and then buying rope, that some rope is more buoyant that other rope. heh. My test of 1/4" rope suggested it was more than sufficient, but the rope I actually bought was less buoyant and the rope sinks slowly. It is still better though. One Idea is to cinch up the rope until there is enough to make the tether neutral/positive, but doing that means that all the tension is on the wires and none on the rope.


I have been using an e-bay purchased slip ring for a while now. I have had zero problems with it thus far.

I suspect they have conductive oil on them which would keep them from corroding in the slip mechanism. Also, since we only need 2 conductors, and the slip rings tend to come in 6 - 12 conductor varieties, the extra conductors can be linked together which might reduce noise. Or quite possibly noise is not an issue at all. :smiley:


One might try a larger diameter rope, say 3/8 inch to increase buoyancy. Another alternative would be to maybe to insert small strips of neoprene in to the weave of the rope at regular intervals in order to increase the buoyancy. However, it is important to not make the tether too buoyant lest we create additional problems…


Hi All,
Anyone had any experience with this 1/4 inch diameter braided poly rope on Amazon?


This i exactly the same rope I used. I’m very happy with it, but it’s not quite neutral in the sea water we have around here, in western of Norway. So I had to attached som floaters to it, to make it neutral. But maybe if you got more salty water, it will be neutral “as is”. For floting I used pieces of the material they use in the ropes for fishing nets. This material is proven for depths up to 100m, some up to 300m without loosing floating capabilities. Tried several different materials first, like cork, foam materials etc, but all of them worked only to some depth, like 20-30m.