[dwalsh62]

You certainly do not put 100 watts of power into something and get 7200 watts out of it as you describe here:

"100W at 72:1 gives 7,200W (7.2KW) at the output of the harmonic drive "

That is completely wrong and I am curious how you can be designing or assembling anything if you are working with ideas like that.

In any case, power certainly does go down in any system. Every system has loss of some kind and in a gear train most of that loss is friction. So with your 100W in you are doing pretty good if you get 98W out of it.

You mean everyone else in the world has it wrong????

Torque multiplication is a byproduct of gear reduction, google confirms this.

We have a a machine that installs 10mm bolts, it's driven with a 40W 90VDC motor, I've removed the motor to service it a couple of times over the last 5 years, you can stop the shaft with your fingers or prevent it from starting by holding the shaft with your fingers, the machine has a gearbox with a ratio of 200:1, if you forget to engage the clutch it will twist the head off of a grade 12.9 8mm bolt and do it effortlessly, I guess my fingers are stronger than the grade 12.9 bolts or the machine has some magical powers if your opinion has any fact.

Information taken from a torque calculator located HERE
The output torque and speed of a gear reducer with 200 :1 ratio,
input torque of 7.35 in/lbs: (torque of 40W 90VDC motor)
1,470.0000 in/lbs (rounded to the nearest 10,000th)
input speed of 9840 RPM is: (RPM of 40W 90VDC motor)
49.2000 RPM (rounded to the nearest 10,000th)

Even if there is 25% loss (highly unlikely but I'll humor you with an unrealistic loss), there is still sufficient power to twist the head off.