Need some help here… my team is struggling how to build a service loop for our turret.
Our shooter turret sits basically on top of the robot… with balls feeding up through the center of the turret… meaning wires need to go along the outside.
Mechanically the turret could spin forever, what is going to limit us is the wiring to the motors on each side of the turret.
How are people handling allowing these wires to service loop around the turret? I would love to get it so we can rotation +/- 360 degrees from a single point on the turret. Mechanically we aren’t limited to do that… but service loop wise we might be.
I think you should ask yourself what are the realistic limitations in your strategy if your turret only rotated say 270 degrees or even 180 degrees.
This would make your problem much easier to solve. Wire management with a 360 degree turret is usually accomplished with a slip ring and i’m not even sure if there’s a legal FRC solution.
The limiting factor is cost and materials. A lot of slip rings use mercury, which is explicitly banned. The others either don’t fit needs for the number of electrical contacts or fit within the BOM limitations.
Anyway to OP, we had ~380° of wrap in 2016 and ~400° (in some cases 1800°) in 2019. There is no fancy trick, you need to make your tether as long as you want to travel and have your turret home in a “neutral” state to make your programming a little easier. I would recommend making these tether points as solid as possible, and make sure there is no way it can get snagged internally when the turret spins quickly. In the past, we have played with adding a badge reel to hold down the tether. This allows the turret to spin freely but adds a downward force on the tether to prevent it from getting stuck on different places on the robot
If you mounted a typical wire snake horizontally (laying on its side) instead of vertically, it could wrap around the turret as the turret rotates. As you unwrap it when the turret rotates back, you would need to have a way to pull that wire snake out linearly horizontally away from the turret. This could be done with a retraction line (shock cord or some rope+spring system). I have seen this done in industrial applications.
Edit: I just found this system that would also work with standard wire snakes to guide them as the turret rotates. You could probably 3D Print something similar.
Our current solution to running wires to our turret is to run wires through a PVC pipe so that they drop above the hood shooter near the axis of rotation. This way, the wires don’t twist much, and they’re still protected for most of the cable run. The only major downside is that it adds about 6" to our minimum robot height as currently designed, so we might need to find an alternative if we want to try to go under the control panel.
A previous idea was to use igus energy chains with a reverse bend radius. That would be very compact vertically, but would add several inches to the diameter of the turret, making packaging difficult. I did end up getting a list of energy chain models that can be used with RBR without getting a custom order, if that helps anyone. RBRMoldedList.pdf (433.8 KB)
I think we just let it hang, but we played with adding a badge reel to provide a downforce on the tether. It worked but I think I remember us not liking how it restricted motion in some corner cases.
We used a slipring from them in 2012, and honestly, while it was nice to have full 360 movement, it was highly impractical, and I don’t believe it was worth the extra work setting it all up.
Not sure if the one we got from Moog contained mercury or not if so it would be outlawed starting in 2015. I don’t remember the exact price (as they donated it to us.) but if I remember it was around $300? the one we used. Here is a video of it in action.
