Venturi shows eight-motor electric sportster

Gallic moteur maker Venturi has taken the wraps off the result of its co-development effort with tyre company Michelin: un sportster electrique avec two motors in each wheel. Venturi Volage Venturi's Volage: hugs the road, actively The four-wheel drive Volage uses one motor for drive, the other for "active" suspension that …

[RMartin]

Heavy wheels

The car looks very pretty, and its good to see that many manufacturers are now thinking of electric in a performance context rather than in a weedy G-Whiz context, as that is far more likely to get the man in the street interested in electric cars. The media interest in these vehicles is absolutely a case in point.

However, I'm not convinced by Venturi's putting what looks like both the drivetrain AND parts of the suspension in the wheels, as this adds considerably to the unsprung weight of the vehicle, which traditionally means poor handling & braking. I'm guessing that the suspension motor is designed to help overcome the effects of the weight of the drive motor, but that just sounds like throwing unecessary complexity at the problem.

[tony72]

Arnold Lieberman, where are you?

So in the comments on the Honda Insight story posted the other day, Paul Murphy wonders "Am I missing something here? Design a car with electric motors in the wheel hubs". Arnold replies:

"Yes, you are missing something. It's called "handling" ... "Perhaps Mr Murphy should stick to commenting on what he knows about in future, along with all the other armchair critics who appear to know so much more than trained engineers."

Perhaps Arnold should inform the Venturi engineers, who've put not one but two motors in each hub of this thing, of how clueless they are, hmm?

[Jim Coleman]

Holy Flarkbunkles!

That's one desirable mothercar!

Not since I kissed goodbye to my Lamborghini Countach 5000QV for bitchfucking my wallet one time too many at the petrol pumps have I had such wibblylust for a car. 200 miles on a charge? 0-60 in under five seconds? Looks like a carbon-fibre incarnation of Venus on crack?

I'll have one of those.

What's that you say? HOW MUCH????!!!!!

[Natalie Gritpants]

Shame about the doors

It looks nice but what happens when you get back to the car park and find you can't get the doors open because they need about a yard of clearance. Not very cool climbing in through the sunroof.

[Bronek Kozicki]

nevertheless,

... it's beautiful

[Dave]

Looks

Totally un-cool.

And rubbish: 200 miles at 56mph? What do you get at 73mph which is rather more typical (on a good day and a good road).

[Iain]

Contrast and compare

with the Audi in the film of 'I Robot'. Similarity methinks

And imagine presenting those wheels at your local kwikfit!

[amanfromMars]

Silent Stealthy Drive ...... Grimaldi DNA Gnometry

A Sexy Motor.

[Anonymous Coward]

Unsprung weight?

By the look of things (going on the photo of the wheel) it seems that a lot of items that contribute to unsprung weight in a conventional vehicle (brake disc, drive shaft, universal joints etc.) have been ditched and replaced by the motors.

Although its going to be very expensive, it could well be the pattern of electric vehicles to come. As for 73mph average speeed for the day, not very realistic given that most of us have to travel to and from high speed roads at an average of less than 30 mph (and who wastes a sportscar on a motorway? Any idiot in a repmobile can average 100mph there).

[TeeCee]

Unsprung weight

True, conventionally. However, as with all such "rules" of automotive design, it's a tradeoff.

Colin Chapman (one of the world's greatest proponents of minimal unsprung weight) was, himself, responsible for the "dual chassis" Lotus F1 car that had the wheels and all the aerodynamic components (i.e. most of the bodywork) unsprung, with a sprung "tub" containing the driver and engine / transmission assembly.

The reasoning here was that maintaining a constant ground clearance post "skirt cars" and the predictable downforce thus achieved was more important to the handling than the increase in unsprung weight. He was right too. The lap times achieved show that Lotus would have wiped the floor with the opposition that year had not the F1 authorities reinterpreted the rulebook and banned it.

In the case under discussion, the active suspension makes unsprung weight pretty much a moot point anyway as this serves to remove the impact on the springs and dampers (it's a supplementary system rather than a replacement, if I've read correctly) of the additional moving masses. As for braking, a larger unsprung to sprung weight ratio is, if anything, an advantage. The same amount of kinetic energy has to be removed by the brakes whether the moving mass is sprung or unsprung, but sprung weight contributes to braking dive and squat whereas unsprung weight does not.

[Gulfie]

@RMartin

Unsprung weight is unlikely to change significantly over a 'traditional' wheel with disc brake, caliper and hub complete with bearings and drive shafts. The disc, caliper and driveshaft etc all go with an in-wheel motor design so you don't neccesarily increase the unsprung weight, you just change what it consists of.

It really depends on your overall design as to what type of electric motors you use and where they end up being installed. The Tesla uses a gearbox, so in-wheel motors are out. The Lightning does not use a gearbox and does have in-wheel motors.

These cars use different types of battery as well, management of the power delivery is very important as getting it wrong can kill the battery and/or its ability to recharge, so it becomes an exercise in getting the right amount of eletrical power matched to the right kind of electric motor(s).

So the drivetrain design fundamentally affects the decision on where the motors go and therefore if the unsprung weight increases or not, and as a result some manufacturers have successfully used in-wheel motors whilst others have said that the increase in unsprung weight is unacceptable.

Pick up a current copy of Evo for some excellent inside info on this.

[Geoff Webber]

Oh Dear

I misread the second headline.

I thought it said "made in meccano" - now that would have been something!

[Francis Boyle]

re: Heavy wheels

An electric motor's a pretty simple thing (and not necessarily that heavy). The complexity is in the software that drives it and that from my perspective is a Good Thing.

If the motors aren't in the wheels it ain't a real electric car - more like the twenty-first century equivalent of a horseless carriage.

And yes, I wouldn't mind owning one either.

[Anonymous Coward]

And...

will they do a diesel version?

[RMartin]

@Gulfie

Good to see some reasoned discussion on the pros/cons of unsprung weight - did I really just type that? Anyway I can now see that there may be good reasons for not avoiding more weight in the wheels.

However, I still think my complexity argument stands. Here we have a design with eight separate motors in what looks like two groups of four - four for drive, and four for suspension assistance. Each set needs to be co-ordinated both internally and between the two sets in order for the design to work.

No matter how clever the software is, that's still a lot of things that need split-second coordination throughout the life of the car. No matter how reliable each component, they all have a real-world MTBF. In an internal combustion car, failure of the engine gives a predictable result - you slow down in an even manner. In this car, failure of one or more (but not all) motors will result in some pretty immediate and unpredictable things happening. Even worse if the co-ordination system goes up the fritz and starts spinning the port side motors at 500rpm more than the starboard side ones for example. This could happen for innocuous reasons - e.g. crud in a wheel's spin speed sensor. Plus, correct me if I am wrong, but eight motors somehow sounds just a bit more expensive and complicated to design and build than one motor...

Still, its nice to see people experimenting with new form factors in this day and age.

[Kevin McMurtrie]

Wasted motor?

I don't understand why one motor would drive the car and the other manage the suspension. It sounds like a waste of a motor and a LOT of power, especially on a car body that offers little room for wheel travel. Why not gear them so that both motors drive the wheel and the phase difference between them controls the wheel height? Much simpler and efficient.

[Richard Foersom]

Eliica

Having electrical motors inside each wheel is not a disadvantage. Eliica the fastest electrical car, going at 370 km/h, have motors in each of its 8 wheels.

http://en.wikipedia.org/wiki/Eliica

[Richard Foersom]

Eliica

Having electrical motors inside each wheel is not a disadvantage, it gives other advantages, e.g. avoids power loss in transmission systems. Eliica the fastest electrical car, going at 370 km/h, have motors in each of its 8 wheels.

http://en.wikipedia.org/wiki/Eliica