lifting arm gear question ?

i have a easy question, fir power and so it doesnt fall as easy on an arm, would you use the smallest gear from the motor to like a 64 tooth ? or use a medium gear from motor to a large gear second ?? thanks

The higher the gear ratio (driven:drive), the more torque you get (less likely to fall). Assuming you’re driving the 12-tooth gear (connected to motor), and the following gears are driven, the ratios are:

Extra large gear - 84:12 or 7:1 (most torque, least speed)
Large gear - 60:12 or 5:1
Medium gear - 36:12 or 3:1
Small gear - 12:12 or 1:1 (least torque, most speed)

Ok, I have the smallest gear to the motor and the largest gear to the arm, if I threw in another 12 tooth gear inbetween , so it would be small gear to motor another set of small gears , then large gear on arm , would that help to slow down and not fall ?

It sounds like you have a problem keeping your arm at your desired height. Instead of changing your gear ratio, try adding elastics/rubber bands to provide tension upwards on your arm so that gravity does not push it down when you raise it. You’ll have to play around with the amount of tension you provide to find the right ‘balance’ for the arm.

To answer your question, yes, a middle idler gear (or gears) may help the arm not fall down on its own, due to the additional friction introduced by that middle 12tooth gear.

You can also make a “compound” gear ratio. That will provide you with more torque if you build it correctly and more friction, both of which will aid you in holding your arm up.

would a 5:1 gear ratio be good for a NZ design 6-bar?

My team currently runs a 7:1. It really all depends on what type of motors you are using, what quantity your using, and how heavy your lift system and intake is.

Be careful with compound gearing, as you’re putting a lot of torque on the intermediate and final shafts. For example, 3:1 followed by 3:1 will put 3x more torque, and thus force, on the intermediate and final shafts than will a single (hypothetical) 9:1 gearing. If you don’t have issues with gears slipping, compound gearing should be fine.

Motors should not be supporting the whole weight of the arm by themselves. Use elastics to take some of the burden off of the motors.

I would advise a 1:7 ratio whether you are using two motors or four motors. With four motors a 1:5 would probably be fine, but I imagine you would want more motors for your drive so I would say two 393s at 1:7 for a six bar.

That also depends on how many game pieces your intake will hold at once…
7:1 even with rubber bands usually has trouble lifting 6 pieces at once.

@NNE : I would personally go with the 5:1 if you’re using aluminum on the standard New Zealand lift/scoring mech. I’ve heard that team 10D has had great success with this gear ratio so far.
But it’s a simple switch either way, perhaps you should test it in different game scenarios on the practice field you have in the basement. :slight_smile: