"Christopher Tidy" wrote in message
...
Any gearbox experts here? Just puzzling over why really big gearboxes
are commonly avoided. Locomotives mostly use electric transmission and
the reliability of gearboxes in things like wind turbines isn't great.

Is there some reason to do with scaling the geometry, like if you
double the size of every dimension, the shaft can transmit more torque
than the teeth? At a quick glance, it doesn't seem that simple. Or is
there more slip between the teeth and more wear? I can't figure out a
concrete reason and it's bugging me :-).

Chris
============================
From what I've read it seems the reasons are mismatches between the
engine and load torque/speed requirements and problems keeping the
shafts aligned in large, somewhat flexible structures like ships.
http://www.navweaps.com/index_tech/tech-038.htm

https://www.wartsila.com/docs/defaul...la-o-gears.pdf

Gears worked better when the speed was relatively constant or the load
demand could be controlled by varying propellor blade pitch as on
large WW2 aircraft engines.
http://www.newcomen.com/wp-content/u...r-13-White.pdf

http://www.machinedesign.com/news/co...tary-gearboxes

Usually lowest overall cost drives the choice.
-jsw