Sum of torque

[dieter]

Hi EOW,


did I understand this correctly:
the motor turns the big pulley, the small pulley recovers the energy, and the support rotates due to inertia?


Did you get the gears yet?


BR

[EOW]

the motor turns the big pulley, the small pulley recovers the energy, and the support rotates due to inertia?

yes, there is no torque on the support IF pulleys don't accelerate.

Did you get the gears yet?

yes but the energy recover is lower (there is friction and efficiency of generator is not 1 maybe 0.8 or lower) beause w is small and the motor turn very quickly => the force is small, I need a low speed motor and a support that turn at w high enough. I gave an example, the power recover is smal with a small force.

[dieter]

There may be some low RPM dc motors using built in gears, like eg. a grill motor. I also got one from the mentioned laserprinter, although more of a motor with attached gear set. However defective laserprinters are a great source for gears, I got mine for 5 bucks, was even still working, but I wasn't interested in printing...


Other sources may be Microwave oven plate motor (dc?) or scanner motor, they all need to be low RPM for what they do.


BR

[EOW]

There may be some low RPM dc motors using built in gears

with gears inside, there is a counterclockwise torque on the support, the motor needs to rotates slowly or the angular velocity of the support must be high.

With:

w (support) = 157 rd/s (1500RPM)
w (motor) = 157*2rd/s and P=300 W, the torque is 1.91 Nm => the force is 19 N if 3R = 0.1 m, R=0.1/3

The generator turns at 6w but the stator of the generator turns at w, so the difference is 5w. The generator can give 5FRwt.

The power won is 2FRw = 200 W

If the efficiency of the motor and the generator is 0.8, the global efficiency is 5/3*0.8*0.8 = 1.06 so it is necessary to use brushless motor (some can have an effciency of 0.9) and without take in account of the efficiency of the electronic card and the belt... maybe 0.95 for the belt and for the electronic card, the global efficiency become 5/3*0.8*0.8*0.95*0.95=0.96. With a motor/generator at 0.9 this could be: 1.21

Maybe the best is to test a basic dc motor/generator and look the efficiency without rotation of the support and turn more and more the support and look at the efficiency, the efficiency must increase more and more like the angular velocity of the support. The small pulley can be smaller, 3R for the bigger and 0.2R for the smaller, the efficiency will be at 29/15*0.8*0.8*0.95*0.95=1.11

[dieter]

There are also losses in getting the required current to the pulley's motor. As the support is rotating, you maybe need to use brushes. Or you could try inductive coupling if the support has near zero mechanical losses: an additional disc on the support's shaft, maybe 1-2 foot away to prevent magnetic interferences with the dc motor etc. Although the Lorentz force is the only cost in frictionless inductive coupling (other than friction etc.), the implementation would complicate things.


Furthermore, you also got to extract the power from the generator to measure it ...


If the COP is over 1.0 then it may be possible to have everything on the support...


BR