[sdiy] OT: Generator?

[KA4HJH]

Yeah we're really milking this (off) topic now, but I know we've got some
railfans on this list...and I never did get that Lionel train set for Xmas.
8^(


>an electric motor provides  tremendous torque from a
>dead stop. It wants to turn in a big way when power is applied, or it will
>dissipate the energy as heat.

Produces the most torque when it's stalled, doesn't it?


>Piston driven motors physically can't run when
>they're not turning, so there's no torque available. They have to be running
>at some higher speed to generate torque. That's the main reason the
>horsepower of a diesel is converted to electricity for electric motor torque
>in locomotives. You need torque to pull the tremendous weights, and you need
>it from standstill.

Exactly. I seem to recall that you test the power of a motor by braking it
to a halt. With an ICE motor the torque peaks somewhere right before it
stalls.

Piston-driven steam engines didn't have this problem since they were ECE.


>Notice when you hear a diesel train engine, it's rumbling
>at about the same RPM all the time? That's horsepower available to generate
>current for electric motors, regardless of train motion. The diesel generator
>eliminates the need for the overhead lines (or powered rails in a subway
>engine).

They actually have a surprisingly limited speed range. A typical locomotive
these days is over 4000 horsepower thanks to all the high tech gadgetry.

Steel wheels on steel rails have the highest adhesion when they're just
slightly slipping so modern locomotives use computers to keep the wheels
slipping just the right amount. They use doppler radar to measure the
ground speed and compare it to the rate of rotation of the wheels. You can
almost triple the tractive effort this way!


>There's a CSX railroad shop near me that rebuilds both the diesel engines and
>electric motors. Pistons almost the size of 5 gallon buckets, and the motor
>armatures are bigger than 55 gallon drums! Pretty impressive stuff.

V12's and V16's. EMD once made a V20, but they had problems with the
crankshafts.

Nice neighborhood you live in.

-- 
Terry Bowman, KA4HJH
"The Mac Doctor"