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-   -   Smoking RS-550 motors (http://www.chiefdelphi.com/forums/showthread.php?t=91491)

billbo911 11-02-2011 17:31

Re: Smoking RS-550 motors
 
OK, I crunched some numbers based on what you gave us + a couple assumptions on stuff you didn't give us.

SR550 with 25:1 reduction should yield 9.185Lb/ft of torque. Assuming you used a 25:1 2 stage planetary trans for reduction, your actual usable torque should be:
9.185*.81= 7.44Lb/ft of torque.
Spinning a 3" dia. pulley yields 29.76 Lb/ft of maximum torque.

I verified that you are running at about 60% torque capacity.

So the load on the motor/trans/pulley is roughly 17.86 Lb.

Now, from all I have read, optimal design is to keep the load at 50% or less of max. So, if you can reduce the load via. weight reduction, alignment, lubrication etc. to less than 15 Lbs, you lift should be in good shape.

Based on all these calculations, I too would say you had a bad case of "Baby Smoke".

BTW, If you are pulling 51 amps (85*.6), then you are dissipating as much as 612 watts. No wonder it's smoking! It won't do this very long, so make sure to reduce the load as much as possible.

Al Skierkiewicz 11-02-2011 17:34

Re: Smoking RS-550 motors
 
Ok Jeff,
I think you are on the right track. One of the issues we have noted in the past, is the efficiency of the internal fan at different speeds and it's effect on internal heat. Slow speeds just don't get the job done. So it's a combo problem with high heat generated and poor fan efficiency occurring at the near the same RPM. The holes in the end plate opposite the motor leads form the inlet for cooling air. If those are blocked, very little air moves.

klmx30302 11-02-2011 17:35

Re: Smoking RS-550 motors
 
Hmm.... to make our rs550 smoke we had to have it lift 70 pounds. we were using a 64:1 transmission with a 2" spool.

Ether 11-02-2011 19:16

Re: Smoking RS-550 motors
 
Quote:

Originally Posted by billbo911 (Post 1020779)
If you are pulling 51 amps (85*.6), then you are dissipating as much as 612 watts.

Not really.

If the RS550 is operating at 40% rated speed, then it's pulling ~51.6 amps @ 12 volts or ~619 watts from the power supply. But not all that power is being dissipated as heat. 237 of those watts are output power at the motor shaft. So "only" 382 watts are being dissipated as heat in the motor. Still too much, I know.


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