Electric motor design claims remarkable improvements • Hacker News Board

Re: Electric motor design claims remarkable improvements

#141

Post by elihu » Mon, Aug 19, 2019, 8:49 PM UTC

Svip wrote: post #20

yholio wrote: post #8

Electric cars don't usually have "gearboxes" proper. They use gears, fixed ratio reductors. This is not expensive nor is it fragile nor bulky nor inefficient. The benefits that a very high torque motor could bring are real but marginal, a few percentage points improvements on the respective metrics. They could instantly be negated by, say, the lower initial reliability of a revolutionary design.

I am genuinely curious, why aren't there transmissions for electric engines? Surely the advantage would be the same as for an IC engine. I remember hearing that Tesla tried to build a 2 speed transmission for their Roadster back in the day, but apparently it kept breaking, so they stuck with no transmission. Are there transmissions out there for EVs, and I just haven't been paying attention? And if no, why is it so h…

EVs don't usually have a transmissions unless they were converted from a gas car. Electric motors don't stall and generally have a much wider RPM range where they're usable and efficient.

I think most people with conversions just drive around in 2nd gear or thereabouts most of the time. Transmissions are a nice-to-have feature though, especially if your motor isn't particularly powerful and isn't made to run at extreme RPMs.

Re: Electric motor design claims remarkable improvements

#142

Post by foobiekr » Mon, Aug 19, 2019, 9:00 PM UTC

londons_explore wrote: post #121

adammunich wrote: post #109

Earlier quoted context omitted.

A reduction gear is really not all that much of a loss, wind on the other hand-- that's a big one.

Airflow losses in big AC generators are solved by having the whole motor sealed in helium. The helium gas is used as a coolant too. It would be hard to design such a system with a big enough supply of gas to survive leakage for the whole life of the motor though.

I thought these mostly used hydrogen instead of helium?

(and as an aside, hydrogen detecting sensors is an area of astounding complexity and cool effects which are worthy of an HN post all on their own)

Re: Electric motor design claims remarkable improvements

#143

Post by coryrc » Mon, Aug 19, 2019, 9:49 PM UTC

foobiekr wrote: post #142

londons_explore wrote: post #121

Earlier quoted context omitted.

Airflow losses in big AC generators are solved by having the whole motor sealed in helium. The helium gas is used as a coolant too. It would be hard to design such a system with a big enough supply of gas to survive leakage for the whole life of the motor though.

I thought these mostly used hydrogen instead of helium? (and as an aside, hydrogen detecting sensors is an area of astounding complexity and cool effects which are worthy of an HN post all on their own)

I doubt hydrogen would ever be used because it makes metals brittle.

Re: Electric motor design claims remarkable improvements

#144

Post by Gibbon1 » Mon, Aug 19, 2019, 10:45 PM UTC

coryrc wrote: post #143

foobiekr wrote: post #142

Earlier quoted context omitted.

I thought these mostly used hydrogen instead of helium? (and as an aside, hydrogen detecting sensors is an area of astounding complexity and cool effects which are worthy of an HN post all on their own)

I doubt hydrogen would ever be used because it makes metals brittle.

I'm pretty sure large generators used hydrogen at one point. I seem to remember reading about them using a palladium membrane to purify the hydrogen used to cool generators.