Turns out Helical Beam Couplers aren't meant to handle that much stress . . .

[Al Skierkiewicz]

I know you can't see it in the video but your coupler got into a resonant mode where the parts were vibrating independent of the lead screw. When the resonance hit the right part of the coupler, the stresses increase significantly. That is why you had parts of the coupler deform more than other parts.

[Chris Fultz]

We used a 5/16-5/16 flex coupling on part of our winch this year. In the right application, they are very good. We purchased from McMaster-Carr.

Below is a link to the McMaster part that looks similar to what you are using. it has 5/16" and 1/2" bores. This part is rated for 0.015" parallel offset and 5 degrees angular offset. It sells for $55.

http://www.mcmaster.com/#6208k596/=ryvr6u

Another strong point to make is the connection directly to the CIM. The CIM "bearing" is just a bronze bushing and cannot take axial loading. The motor and connection really needs to be mounted in a way that limits the axial load on the shaft.

Your initial question was if the part from China was as good as a part from other suppliers. I have an opinion, but i don't think this test can validate yes or no because the part was used well beyond what it is designed for.

[Monochron]

Originally Posted by Al Skierkiewicz

I know you can't see it in the video but your coupler got into a resonant mode where the parts were vibrating independent of the lead screw. When the resonance hit the right part of the coupler, the stresses increase significantly. That is why you had parts of the coupler deform more than other parts.

Hun interesting. I just assumed that parts were more deformed because it was able to bend such a large angle and a certain ring section failed before the others.

After the fact we looked up the length of exposed threaded rod that would lead to resonance at our diameter and found out that we were WAY over the limit. This mechanism was nick named the "Garbage Disposal" shortly after due to the noise.

Originally Posted by Chris Fultz

Your initial question was if the part from China was as good as a part from other suppliers. I have an opinion, but i don't think this test can validate yes or no because the part was used well beyond what it is designed for.

Yeah, the McMaster one would have to be significantly stronger in order to make it usable for this application. I'm thinking that any helical coupler like this just isn't going to get the job done. We will have to stick with our giant solid piece of aluminum that we used during the season.

[Al Skierkiewicz]

Brian,
I tell people all the time to listen to the robot. It talks to you, you just have to know what it is saying.

[FrankJ]

You really need a rigid coupling there since you are transmitting a bending moment through it. (Like you giant solid piece of aluminum?). Flexible couplings are meant to transmit torque, not to hold things in alignment.

To help with the resonant frequency and the vibration, cut off the extra length of screw since it is mass whipping around. Use a a speed controller on the motor to slow the screw down. The more it extend, the faster it can go.

[Monochron]

Originally Posted by Al Skierkiewicz

Brian,
I tell people all the time to listen to the robot. It talks to you, you just have to know what it is saying.

You're absolutely right. I think in this case ours is saying "AAARRRRGGGGGHHHWHYOHGODWHYRRRRRRRGGGGGG!"

[Monochron]

Originally Posted by FrankJ

Flexible couplings are meant to transmit torque, not to hold things in alignment.

Well, I specifically chose Helical over a Lovejoy or Oldham for their ability to both transmit torque and hold things in alignment. I think that the huge amount of angular force and resonance was simply way more than it was intended to handle.

To help with the resonant frequency and the vibration, cut off the extra length of screw since it is mass whipping around. Use a a speed controller on the motor to slow the screw down. The more it extend, the faster it can go.

Unfortunately we only have an inch or two of extra length, we cut it about as short as we could get it while still allowing some length in case the ball holder extends past our hard-stop.
As far as speed control, yes it is on a Talon but we already have it as slow as it can go before it starts failing at its extreme down position. Any slower and it stops having the power to lift back up to a Hold position.