Slewing Gear pulsing during rotation

[bonesoup]

Hey all,

So I finished the prototype Slewing Gear last night. I loaded it up to see how well it will turn. - I also clearly OVERLOADED it.

https://flic.kr/p/CxppjQ

In the video it starts to pulse - yes I know it's overloaded :P

Two questions:

1) What terms describe this unwanted motion? Physics or engineering terms ect:

2) What kind of solutions exist. ( besides reduce the load )

I'm not trying to solve the impossible, just learn from it to design a better setup which can handle such a load smoothly ( maybe it simply cant ). No worm gears are used to drive this ( this would be my first thought ).

Thanks

[Blakbird]

No way to tell from your video, but typically this kind of motion is caused by elasticity in the drive train. Because the static and dynamic friction coefficients are different, it takes a certain amount of torque to get the model moving and then a smaller amount of torque to keep it moving. During the first phase, the drive axles wind up like a spring. When motion begins, this energy is released and causes a sudden acceleration. Once that energy dissipates, the model slows down again, possibly even stopping to begin the cycle again. If this is what is happening, the only thing you can do is use stiffer components (i.e. metal) and/or reduce friction (i.e. bearings).

[bonesoup]

Thanks for the quick reply.

I think you are describing the problem exactly. There are quite a few parts used just to keep the hail-fire gear from having any sideways play (which I can reduce I believe) this is at least one source of unwanted friction - I have a few other thoughts as well. On further inspection my drive train is rather silly. I chose to move the motor outside the main structure in favor of having an open center in the slewing gear itself. There are way too many parts and long axles in the drive train. So it looks like a redesign of the drive train and a reconsideration of how I reduce sideways play in the big gear.

Thank You!