[sdiy] OT: Generator?

[KA4HJH]

>> In the UK, and I guess many other electrical railway systems, a system
>> of regenerative braking is also used. Any generated electricity from one
>> locomotive is fed back into the supply grid to power other engines on
>> the line. (also used in battery operated vehicles too to recharge the
>> batteries).
>
>throughout this thread, I've been wondering why locomotive engines in
>america don't do this... (regenerative braking).  AFAIK, even though
>trains are diesel in america, the diesel powers generators and the
>locomotion is created by big electric motors (don't ask me why!),

It's a problem of sheer scale. The forces involved are so large that the
drive train needs to be as mechanically simple--and straight--as possible
or it won't last very long! That's why locomotives (and other large
machines) use hydraulic or electric motors. The hydraulic approach was
tried but never caught on with US railroads.

I once had the opportunity to drive a train through the (railroad) yard.
Over 10,000 tons at my fingertips. Imagine having to start that load up a
hill! The traction motors drive the axles through simple spur gears, and
the motors themselves aren't completely fixed but rather pivot around the
gears. That way any sudden change in speed doesn't break teeth.

Superchargers have a similar problem because they're geared up. There has
to be some slack in the mechanism or something will break. That's why they
use rubber belts (or in the case of some aircraft long drive shafts which
act as torsion rods).

> so
>it makes sense to me to use regenerative braking, unless of course,
>there aren't any batteries, just the generators to the motors (through
>a controller or two no doubt)

Nope, they just use the current to heat resistors. Saves wear on the
brakes. Some railroads in the US were electrified; I don't know if they fed
the current back or not.


John L Marshall wrote:
>
>The generator-motor approach solves the gear shifting problem. Kenworth
>trucks have up to 16 forward gears to start rolling and then get up to
>speed. Imagine the gear box for three locomotives that are pulling a hundred
>cars!

Then there's THAT little problem... As it is they have to switch the wiring
of the motors depending on the load/speed.

-- 
Terry Bowman, KA4HJH
"The Mac Doctor"