Swedes partner to build new EV transmission

Three Swedish companies have designed a new transmission for electric vehicles, which will be on display for the first time at next week’s CTI Exhibition in Berlin... http://www.chargedevs.com/content/news-wire/post/swedes-partner-build-new-ev-transmission" onclick="window.open(this.href);return false;

I'm guessing that a transmission would be beneficial to make the electric motor more efficient by running it at or near its efficiency sweet spot rpm rather than to get more power or torque. It may be able to provide more range. Tesla abandoned its 2-speed transmission after having problems with it. I wonder if they will try to bring it back with the new model.

Material --------------------------Tensile (psi)
Wrought Iron, Hot Rolled ------------331 (48,000)
Powder Metal, 84 % density ---------- 214 (31,000)
Powder Metal, repressed, 95 % density - 283 (41,000)

I had my doubts this was wise, until I read this:

In comparison to the traditional gear manufacturing process, the powder metallurgy process offers several advantages, particularly the elimination of machining and scrap losses. Internal configurations (splines, keys, keyways) can also be formed simultaneously with the gear profile during molding, eliminating subsequent machining operations. General process advantages of powder metal gear manufacture include:

* Economy in mass production
* Repeatability and uniformity of part features and dimensions
* Production of multilevel gears
* Close control of density or , conversely, porosity to suit a particular application
* Reduction or elimination of secondary operations
* Improved surface finishes on gear teeth by reducing or eliminating the machining (or "scoring") marks that can be left by conventional methods
* Self-lubricating ability from impregnation of oils and lubricants into the pores
* Noise reduction from the sound-dampening qualities of the pore structure of a powder metal component. High surface finish and tooth form consistency can also have an effect on overall reduction in noise in comparison to cut gear sets
* Weight reduction by incorporating weight-saving or lightening holes (or similar shapes) in the initial tool design

AP1 said:

I'm guessing that a transmission would be beneficial to make the electric motor more efficient by running it at or near its efficiency sweet spot rpm rather than to get more power or torque. It may be able to provide more range. .

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Obviously, a transmission can do both. They just add weight, cost and complexity to an already overweight and costly propulsion method (EV compared to ICE)

I hope they continue with single speed gearbox.

smkettner said:

I hope they continue with single speed gearbox.

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Replacing the 7.9:1 reduction gear box in the LEAF with a multispeed gear box probably wouldn't be the end of the world in terms of weight and cost. But it does add up.

The trick, like any engineering project, is to make the compromises and balances that offset the weight and cost with increased efficiencies elsewhere (range, power, noise, etc).

To my thinking, anything that boosts the range besides bigger batteries (with current battery tech) is probably good. Let's say a 10% increase in range were possible with just a super duper transmission; how many extra batteries cells would that take, and how much would they weigh and cost?

TonyWilliams said:

AP1 said:

I'm guessing that a transmission would be beneficial to make the electric motor more efficient by running it at or near its efficiency sweet spot rpm rather than to get more power or torque. It may be able to provide more range. .

Click to expand...

Obviously, a transmission can do both. They just add weight, cost and complexity to an already overweight and costly propulsion method (EV compared to ICE)

Click to expand...

Yep - even though the torque curve of your typical EV motor is way better than your typical ICE, there is still room for improving efficiency by keeping the motor in it's sweet spot.

I suspect that efficiency will also improve significantly at higher speeds as well.

It also seems that you're probably not going to need more than 2-3 gears for your typical EV before you've reached the point of diminishing returns at least with current motor technology. More efficient motors may reduce that further.

Powdered metal tech is scary, but if the parts are properly designed (larger) then its ok.. but I'm not convinced electric cars need a multispeed transmission.

Interesting article on transmissions for evs:

http://www.gizmag.com/antonov-3-speed-transmission-ev/19088/

There's also the Borg Warner unit:

http://www.borgwarner.com/en/Drivetrain/products/Literature/eGearDrive%20Product%20Sheet.pdf" onclick="window.open(this.href);return false;

hpage said:

There's also the Borg Warner unit:
http://www.borgwarner.com/en/Drivetrain/products/Literature/eGearDrive%20Product%20Sheet.pdf" onclick="window.open(this.href);return false;

Click to expand...

That's a single speed unit. Good to know that even a single speed gearbox is 97% efficient... Would be nice to compare to a multi-speed unit.