Change internal gearing or external gearing for flywheel?

VEX V5 General Discussion
#1

We didnt get our 600 rpm cartridges early so we built our flywheel with 2 200 rpm motors geared 15:1 (3000 RPM flywheel). We checked the motor RPM and it was able to maintain 190 - 200 rpm easily. It wasnt powerful enough for us so we decided to make the gear ratio 7:1 when the 600 rpm cartridges came for a 4200 rpm flywherl. After we swapped the motors, swapped the gears and tested it, we found that the 2 600 rpm motors never actually go up to 600 rpm. They hover between 450 - 500 RPM. Because of this, i was wondering if it would be better to use higher torque motors and bigger gear ratios rather than a higher internal gear ratio and lower external gear ratio.

#2

My initial thought process was that internal gearing would be better because it minimizes friction, maybe im missing something?

#3

You increased the strain on the motor by over 30%, so why would you assume it would preform the same? If the total gear ratio is the same then you should get similar results. That would be a better test.

#4

Usually you’re better off with internal gearing over extra compound external gearing due to friction.

You may also consider the curves for the motors. Trying to run at full speed is not the most efficient, and the motors won’t be able to provide as much torque.

Have you tried 7:1 running at a target of more like 500 rpm for consistency?

Separately, I have some students running a flywheel off a single v5 with a 600 rpm cartridge at 5:1. They’re still fine tuning things, but they’ve shot over the netting from the far end of the field. I think you may want to check some other factors, too, like friction on the axles, grip on the flywheel, rotational inertia of the flywheel, etc.

#5

For some reason we’ve never shot that far, even with our 2 200 rpm motor 15:1 flywheel. Our flywheel is 2 standard wheels wrapped with rubber bands, we have tries both foam and mesh on our hood, and we have 2 bearing blocks per axle (3 for the flywheel), and there is no metal to metal (or metal to plastic) contact. Our balls dont go farther than ~10 ft (might be inaccurate, i forgot the exact distance and need to retest) and cant turn the flags consistently unless it hits it in a very specific area.

#6