One of the most interesting applications I've heard of for planetary gears is as replacements for stepper motors in positioning systems. By running 2 servo motors in opposition the output can be 0 rpm, but 0 rpm at the torque of the motors.
in other words, if you have 2 motors rated at 1 HP and 1800 rpm ea, by changing speed and direction of the motors you can have the ouput range from 1800 rpm at 2 HP to 3600 rpm at 1 HP. If the motors are in exact opposition to each other, each will be applying full torque to the output so any attempt to move it will be resisted with full motor power. Great for CNC machines where you need the holding power of steppers with the power profiles of servos.
For boating, imagine being able to handle a snag at low rpm with the full force of the motors or using high speed motors to turn a low speed prop at full power.
You can also combine electric motors with petro engines. With the right electric motor, you can run it to combine power with the petro engine or back drive it to generate electricity.
David
--- In electricboats@yahoogroups.com, Craig Carmichael <craig@...> wrote:
>
> For example, I just realized last month that you can use a simple 3
> element planetary gear as a compact, infinitely variable torque
> converter to replace an entire automotive transmission. (My "Electric
> Hubcap" motor was named for where I want them to mount, not just for
> its pancake shape.) Just let the ring gear slip backwards at a
> controlled rate and you increase the reduction ratio between the sun
> gear and the planets assembly. You can have 1000 to 1 if it's needed.
> (Somewhat unintuitively, no energy is lost except frictional losses.
> The slip control is of course an important design detail. It can be
> controlled by a mechanical brake/clutch, possibly a magnetic brake,
> or with a motor/generator.)
>
> It took me 3 years to come up with that... and planetary gears have
> been around for maybe a century. If anyone else ever figured it out
> previously, they didn't tell anybody. There've been lots of people
> trying hard for a long time to come up with a good CVT or torque
> converter, and there are a number of strange, complex and inefficient
> designs out there.
>
> Craig
>
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