Gearbox for mechanism or appendage

[Andrew Duerner]

Hi All,

I did some measurements and testing on the gearbox, particularly on the 168:1.

Weight came to 1.1lb (0.5 kg)

Backlash was 1.1 degrees

Efficiency was a bit trickier. I have a supply that has 3 different power settings and a very course amperage meter. I put a volt meter across the leads when I ran with a bare motor and then retested with the gearbox (no load). I did this with 2 different motor / gearboxes and in both directions. The voltage across with the gearbox was around 9, 12, and 14 volts, so I think the efficiency was hurt a little bit by spinning faster than what would be seen in normal operation. Without putting a ton of data down, the average of the results for efficiency under no load came out to be 61%. All but 2 of the results were +/- %7 from this.

I would expect that the values for the 264 and 552:1 should be very similar to the above.

Next up, making an adapter plate for a torque wrench to test max torque.

[DaveL]

Originally Posted by Andrew Duerner

Hi All,

Next up, making an adapter plate for a torque wrench to test max torque.

Andrew:
If you could build in a FIRST standard bolt pattern, we could attach sprockets!
D

[IKE]

500:1 is probably a bit slow if the plan is to mate it to a CIM motor. At free speed, it would go down to 9 RPM or about 7 seconds per revolution. At peak power, it would be about 13 seconds per revolution. An arm sweeping 120 degrees would be between 2.5 and 4 seconds which would seem pretty slow.

The 125:1 & 250:1 arms have me pretty intrigued.

Are you measuring efficiency as "Actual speed / theoretical free speed"?

Richard Wallace and some others might be able to help you with a more accurate efficiency method that you could do.

A string and spool winch with a weight and stopwatch could probably be pretty effective way of measuring efficiency at several torque levels.

[Richard Wallace]

Isaac is right, a string, weight, spool, and stop watch are the best method for this kind of measurement when speeds are low; e.g., when it takes several seconds for the weight to drop.

On the original topic, I recommend this lugnut remover as cheap example of cycloidal gearing. It was easy to find at Harbor Freight years ago. Don't know if you can find it there now. I posted some details and pictures a few years back, linked earlier in this thread.

[GeeTwo]

Originally Posted by IKE

500:1 is probably a bit slow if the plan is to mate it to a CIM motor. At free speed, it would go down to 9 RPM or about 7 seconds per revolution. At peak power, it would be about 13 seconds per revolution. An arm sweeping 120 degrees would be between 2.5 and 4 seconds which would seem pretty slow.

Several of the four-arm-linkage lifts I saw this year only needed to span about 30 degrees of arc to pick up a game piece from the floor to quite a few feet off the floor, so 13 seconds per revolution would be a bit under 1 second. At these sorts of ratios, a CIM could compete for some jobs for which we would previously only have considered pneumatics.