adric22
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How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 10:33 am

So they were making electric cars 100 years ago. How did the throttle work? Today we use microprocessors to pulse large groups of power transistors at different intervals in order to determine how much amperage we want to go to the electric motor. Obviously that was not how it was done 100 years ago. So how did it work?
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TonyWilliams
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 11:06 am

For a DC electric motor, would you just use a variable resistor?

I think a big spring with a sliding piece of metal maybe?

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mwalsh
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 11:38 am

That would be my guess too...a big old potentiometer.
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 11:41 am

Most likely, Jay Leno knows!
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 11:41 am

Well they did not go anywhere close to 90 mph. I speculate mostly they ran at full throttle except to start and stop. The resistor would be just to smooth the transition.
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 11:42 am

Could also have been a sliding switch that selected from various tapped voltages of the battery array.
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TomT
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 12:00 pm

Yep, that is how many of them worked and how many cheaper golf carts still work today. Various series and parallel combination of batteries. They would also switch in and out very large fixed value resistive elements in some implementations (think of resistive heaters)...


DeaneG wrote:Could also have been a sliding switch that selected from various tapped voltages of the battery array.
Last edited by TomT on Wed Jan 25, 2012 12:54 pm, edited 1 time in total.
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adric22
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 12:03 pm

TonyWilliams wrote:For a DC electric motor, would you just use a variable resistor?

I think a big spring with a sliding piece of metal maybe?

Image


I suspect that thing would melt after about 20 seconds. Too much amperage.
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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 12:25 pm

DeaneG wrote:Could also have been a sliding switch that selected from various tapped voltages of the battery array.


The cells become unbalanced.. a better way is to split the pack in half and configure the two halves in parallel for low speed and in series for high speed.. that plus switching-in resistors to further reduce speed. I think variable rheostats were limited to very low power motors.. 1/2 hp and such.

Look up how GM did throttle control on their series diesel-electric locomotives in the 20s.. very creative without electronics or power wasting resistors.

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Re: How was throttling accomplished 100 years ago?

Wed Jan 25, 2012 8:15 pm

Uh, it's been a loooong time since the DC Machines classes in college, but I seem to recall that playing with the amount of current running in a motor's field coils had a pretty big influence on the rpm-vs-applied-voltage characteristics. You could use a rheostat to modulate a motor's field strength, and still keep the heating losses in the rheostat fairly negligable, I think. Just don't let the field go to zero!

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