Denso Motor with CIMple Gearbox

[JellyMan]

We are considering using the Denso window motors and CIMple gearboxes to pivot a long lifting arm. What is under the plastic drive sprocket on the motor? If that piece is carefully cut off, would that leave a usable shaft which we could attach some kind of coupling to the CIMple gearbox? If this is feasible, does anyone have a recommendation for this coupling?

As we are unfamiliar with lifting arm and motor/gearbox calculations, could someone double check our concept? We have the following:
_ 65 inch arm of less than three pounds
_ 12 oz game tube (0.8 lb)
_ 2 Denso window motors (10.6 Nm stall) on each side of the pivot shaft
_ Each motor driving through a CIMple gearbox (4.67:1)

The JVN-DesignCalc spreadsheet seems to indicate that this would work, but I know the answer is only as good as the input assumptions!
Thanks.
Jeff

[JellyMan]

OK, we've taken a closer look at the Denso window motors. We see now that the metal shaft does not actually move with the splined plastic output. So, that will make connection of the motor to the CIMple gearbox more difficult.

It may be a while before we can prototype this. Does anyone have a feel for whether two window motors, each driving through a CIMple gearbox will lift the arm?

Thanks,
Jeff

[JamesCH95]

They might lift an arm, slowly, if geared down low enough. If memory serves they are only good for 20-25 watts. Compared to the RS775-18s or FP motors at 250+ watts they are woefully under powered for serious lifting. Their worm gears are plastic and have been known to strip, FWIW. I know it's tempting to use them because they have built in anti-backdrive capabilities, but they are relatively weak.

Having said that, check out JVN's design calculator and do the math to convince yourself. They probably could work fine lifting an arm that was light enough.

[Nemo]

Since I am learning to do some of these calculations this season as a mentor, let me take a shot at this. If anybody corrects my numbers, that's great since I want to know if I am doing it wrong.

Torque of the arm = 3.8 lb x 65 in = 247 in-lb = 3952 in-oz.
Torque at Denso motors after gear reduction = 3952 in-oz / 4.67 = 846 in-oz.
Torque per Denso motor = 846 in-oz / 4 = 211 in-oz (stall = 1500 oz-in)
Using the Denso motor curve, a denso can run at about 73 RPM at 211 in-oz of torque (while pulling about 4-5 amps).
CIMple boxes + arm move at (73 PM / 4.67) = 15.63 RPM = 0.26 rev/sec
0.26 rev / sec = about 90 degrees of motion per second.

Is this done correctly?

[joek]

do you mean that you are removing the worm gear assembly?
if you ran it through a CIMple box it would be 18 RPM output.
it would have 3950.8 oz-in (21 ft-lb) of torque
seems like it would work very well for an arm, but too slow for anything else

[JellyMan]

To clarify our concept, we would keep the Denso motors intact (worm gear and all), but drive them through the CIMple gearboxes. We are looking at either one or two such pairs on the arm pivot shaft.
This is what Nemo assumed as well?

Thank you both.
Jeff

[Nemo]

I assumed four denso motors with worm gears intact. The denso motor has to be used with the gears attached since they are considered integral to the motor.