Notched throttles?

[Coldgunner]

I have a question which I hope some of those in the know may be able to answer for me.

 

Why do locomotive manufacturers opt for a notched throttle rather than a variable? From the outside point of view it would see a driver would have less precision control with a notch. Is there any advantage I'm not aware of?

 

Sorry if its seems like a silly question!

[pH]

Stays where it's put?

[Bert Cheese]

I'd imagine it helps with keeping everything in harmony of sorts too...factors such as governor settings and field diverts are probably easier to calculate and set if certain throttle settings can be pre-determined?

 

Mind you IIRC most E.E locos had some sort of infinite control linking the thrash handle to the governor via pneumatics and linked to the load regulator to sort the gen/motor loads out?

 

In other words...I'm not really sure

 

**Edited for spelling

[Oldddudders]

By no means a techie person, and I am slightly more familiar with older EMUs, but the "throttle" was mechanically linked to certain kit, e.g. banks of resistances, which were included or excluded as each notch was reached. Terms like "shunt" "series" " parallel" and "weak field" for individual notches come to mind. First generation US diesels "made transition" at a particular point early in the acceleration curve, where the diesel motor dropped and then regained RPM, in order to enable the current from the generator to the traction motors to be re-routed, probably series to parallel again.

 

All this no doubt changed when electronics came into the equation and infinitely variable settings and automatic changing were possible.

[Pete 75C]

"Notching up" was pretty useful in lots of situations. Avoiding wheelslip on the Caterham or Tattenham branches in winter, for example. Then again, you'd always get the muppets who'd go from zero to weak field on a 4EPB. Pete.