Which is better, 10:1 & 5:1 or 2 7:1 VP stages for an elevator


#21

Good point, I should have included that.

One of them is driving a 24" arm with 12 pounds on the end. It also has a gas shock to counterbalance the weight, so the effective weight should be lower. Without the gas shock, it’s 24 ft-lbs of torque /2 on the chain = 12 ft-lbs. Probably lower than that once the gas shock is added in. 1/2" hex shaft.

The other one is driving a wrist, and I’m not 100% sure what we’re looking at for torque on that. But it’s certainly less than the arm, so if the arm is fine the wrist should be fine.

We will look into doing 70:1, not sure if we’ll have enough output torque then. Potentially dumb question: if 70:1 isn’t enough, would 210:1 (10:1, 7:1, 3:1) be worse or better for gear failure? I know it’s three stage which means the torque on the end is worse, but the output stage would be 3:1, which is the strongest from what I understand.


#22

correct. Actually 2 775s based on the WCP model.


#23

I noticed a lot of teams support the end of the shaft to prevent it being cantilevered. However according to very, it seems this is not necessary and the designs of the West coast products elevator don’t seem to indicate it either. Is it really necessary if you are following the vex loading guidelines.


#24

We sheared 3 10:1 stages on our arm last year before bag day, as a result we switched up the ratios to a slightly higher 3 stage, didn’t have another issue until off season events. Highly recommend the 7:1 setup if you expect heavy loads.

For context, they didn’t shear in normal use, but if our arm came down on the switch with the force of 2 775’s then the 10:1’s said no.


#25

I’m not familiar with the WCP elevator. Does each 775 have its own gearbox? If not, again you’re pushing the torque limits on the gearbox if you stall those motors (e.g. running it with a heavy load or at some sort of stop).


#26

If by WCP elevator, you mean greyt elevator, it actually only specifies one 775, not 2


#27

The VF load limit tables are already based on a cantilevered shaft, or a sprocket/pulley located at the gearbox end of the shaft. See the bottom of page 1.


#28

Yes i know that, and a cantilevered shaft is a worse condition than if you can support the end of the output shaft.


#29

technically we are using the West coast products MCC robot elevator design. It is very similar to their greyt elevator however it does have 2 775s on separate sprockets.