Here’s How A Formula E Race Car Puts Power From Motor To Wheels – Video

DEC 19 2017 BY MARK KANE 19

Formula E for its Tech Tuesdays series attempts to explain the technical details inside electric racers in layman’s terms; the latest video in the series concerns how the car’s torque transmission works.

FORMULA E EXPLAINED: What Makes an Electric Car’s Torque So Special?

In the base case scenario, even with a simple electric powertrain, there is several stages between the torque from the motor and actual transferred to the wheels.

There are now several types of electric power-trains in operation, many have co-axial motors or double motors (one per wheel) as well as some in-wheel motor systems – all with advantages and disadvantages.

The common feature of electric motors however is their high and instantly available torque, and also a high efficiency over a broad range of rpms.

Several prior videos are abour power, monocoque, steering and suspension:

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19 Comments on "Here’s How A Formula E Race Car Puts Power From Motor To Wheels – Video"

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Why is the differential ahead of the differential?

I agree with you. I think that is a mislabel.

I don’t see a differential in the diagram. A single gear seems to be attached to both axel half-shafts which would not allow each half-shaft to rotate at different speeds.

well, technically what is missing that would allow the wheels to turn at different speeds are the spider gears. You don’t technically need for there to be spider gears for there to be a differential. In racing the term for that is having a “spool differential”.

I suppose not having the wheels be able to turn at different speeds makes calling a spool differential a “differential” an oxymoron, but that’s #because racecar. As long as you have a ring and pinion, racers will call it the differential, even if the wheels are locked. Again, the reasoning behind still calling it a differential is #because racecar.

In this case they are calling out the ring and pinion as the differential, the same way an R&P with a spool would be called a differential in a race car.

Conceptually, it is similar to running a 2-speed differential in a Semi truck in the low speed gear setting all the time. It is an additional gear reduction, just using an external gear instead of an internal planetary gear.

Hmmm… torsion bar is used in those suspensions…

Geez, how many people here have made the comments about torsion bar is somehow “inferior” design compared with old fashion springs? Or is it because it is only a complain when they are used on the Volt and Bolt?

Torsion bars are used there for space saving. It takes far less vertical space than traditional springs. That is also why Volt/Bolt uses them to fit the battery in a relatively small frame.

The valid complaint about the Bolt and Volt rear suspensions is that they are not true independent rear suspensions. I believe the rear wheels are connected by a single twist beam which is a type of torsion bar compared with the Formula E cars which use a single torsion bar for each wheel.

That is fair.

So, it isn’t about torsion beam but rather the lack of “true” independent setup.

The next person who blame it on the torsion beam should learn the difference then.

I look at the first picture and see multi-link. Is it something else like a sway bar? I didn’t watch the videos.

Google: Torsion Beam Rear Suspension
Google: Multilink Rear Suspension

You will see how terrible torsion beam looks in comparison. It is okay on flat ground, but vibrations are past from one side of the car to the other.

By the looks of it I would actually refer to the Formula E car as double wishbone suspension, a specific type of multi-link.

Torsion beam is compact and cheap. Good for the Volt to save some space for the 12V battery and inverter. Did I mention
it is also cheap?

Those lovely “Low Traction” messages you get in the Volt when you hit bumps and your regen cuts out. You can thank the torsion beam 😉

Hi highly doubt that the ‘low traction’ message is related to the torsion beam suspension, since traction is on the front axel and torsion beam is on the rear axel.

“Those lovely “Low Traction” messages you get in the Volt when you hit bumps and your regen cuts out. You can thank the torsion beam ”

uh… no.

Torsion beam is only on the rear of the Volt. Volt is FWD and the front isn’t torsion beam.

“You will see how terrible torsion beam looks in comparison. It is okay on flat ground, but vibrations are past from one side of the car to the other.”

You are confusing between a configuration of a suspension setup vs. a particular spring design.

Torsion beam is a spring design. Just like coil spring or leaf spring which are designed to handle travel in the suspension. The multi-link or wish-bone or other configuration is stabilization setup or a configuration of springs/damper and stabilizer setup.

The formula E setup is effectively a multi-link with torsion beam.

HAHA! I didn’t see much of a differential.

Who ever makes these vids makes them with no relation to reality.

The only thing I saw was a first stage helical reduction, a pretty useless 2nd stage conversion to Spur Gears, and then the 3rd stage with no differential gearing shown.

How they get the 3rd stage’s SINGLE row of Spur Gear Teeth to run at different speeds when turning around the corner is a mystery, and I bet it is a mystery to them also.

Any technical description should have explained this clearly. This video is useless crap.

From the way they slide these cars around corners, I don’t think they bother with having the rear wheels turn at different speeds. The design is effectively the same as a “spool differential” that is used in NASCAR Stock Car racing, Australian V8 Supercar Series, drag cars, dirt racers, etc. I would not be surprised at all that the video is accurate, and that there is nothing in the drivetrain that allows the rear wheels to turn at different speeds. As you correctly point out, it is an oxymoron to call a “spool differential” a differential, since the wheels can’t go different speeds. But that’s what racers call them anyways. Just like calling NASCAR “Stock Car” racing is an oxymoron, because there is nothing stock about the cars they race in NASCAR. But that’s the racing world. _____________________– The design certainly does explain why we keep seeing footage of Formula E cars getting sideways. With a “spool differential” the inside wheel has to slip as the weight goes to the outside wheel in the corner. Put on the power and the outside wheel that has traction now has to do all the work. If that tire breaks traction, now both… Read more »

Yeah, lets let all race car drivers have the rear wheels BREAK TRACTION when going around a corner at high speed… Tell me what happens.

Humm, I made a sufficiently intelligent comment and the ‘moderation’ wouldn’t let me in.

No engineer was involved in the production of these diagrams, I have zero confidence in their accuracy. Clearly the drive is wrong, no diff and a (incorrectly aligned) reduction bevel/hypoid gear that clearly isn’t a diff is labelled as one. The steering rack & pinion have drastically different tooth size and the helix angle is backwards such that they wouldn’t mesh anyway.