Michelin reinvents the wheel, electric motors help to retire the combustion engine | Hacker News Reader

Michelin reinvents the wheel, electric motors help to retire the combustion engine

theenergyroadmap.com

43 pointsmielles23 comments

A better write up without the hype

http://www.motorauthority.com/michelins-active-wheel-technol...

Look at heavy equipment LeTourneau loved electric wheel motors. He built huge scrapers, tractors, and offroad trucks with them. http://en.wikipedia.org/wiki/R.G._LeTourneau

One big disadvantage of wheel motors is greater unsprung weight. This will make for poorer ride quality, or more expensive/complicated suspension systems. Because the wheel needs to move over bumps, if it has less mass, it can accelerate with less energy input.

I was about to say the same thing re: unsprung weight. Wouldn't it wear the tires more quickly? That would be good for Michelin...

Is the motor the main weight?

I was under the impression that modern electric motors weigh less per foot/pound of torque than ever before and that most of the weight of an electric vehicle is in the battery pack.

//me wants a all electric version of the dymaxion car

LeTourneau (a personal hero of mine) powered his giant square-wire-wound electric motors with even more powerful diesel engine/generator sets. His machines were diesel powered with electric transmissions.

The article misses the "elephant in the room" point that the electric motors are the easy part. They always have been. It doesn't much matter if you cram the electric motor into the wheel or under the hood. Getting a power supply with enough power density and a short enough charge cycle that its actually feasible for daily use is the silver pearl.

> His machines were diesel powered with electric transmissions.

Large mining machinery (Haulpaks) are the same - electric with a diesel power plant.

I don't believe the wheel weight is a big issue in these cases - particularly for the AC systems, which are somewhat simpler and more robust (in terms of the wheel motor, the actual control system is much more complex).

The reason they use an electric system for Haulpaks is varied - but basically it's due to the fact that a mechanical drive system is almost infeasible at that size/load/torque. An electric transmission system is easier to control and more robust.

Also, electric lets you control the torque much better, particularly in the AC case where they can adjust phase/freq/etc to keep it controlled.

This technology is also common in cruiseships.

Diesel-electric locomotives work like this too. You can run your diesel engine at its most optimal rpm which makes it more efficient.

This is how I hope they'll build gas-electric or diesel-electric hybrids in the future.

I worked at mines a few years back. These diesel electrics were stealthy. Don't make much noise at all, and the next thing you know they are charging at you at 60mph.

Actually, all the technical problems have already been solved. The silver pearl is already there for the taking. It's other factors that are the problem.

The LeTouneau stuff is very interesting.

Your concerns over the ride quality for the wheel are addressed in the press release for the product from Michelin (I linked to it in another comment). The wheel will actually contain an active electrically driven suspension system. Michelin claims an extremely fast response time - just 3/1000ths of a second and all pitching and rolling motions are automatically corrected. I also believe that the idea that the wheel will not be able to accelerate as quickly to be unfounded. The same amount of weight it being rotated, as only the tire, which is roughly the same as any normal tire, is actually spinning.

These pictures give a far better idea of how the wheel is constructed:

Front - http://servicesv2.webmichelin.com/frontnews/servlet/GetEleme...

Back - http://servicesv2.webmichelin.com/frontnews/servlet/GetEleme...

I'm sure there are going to be plenty of complications with the design but it is really good to see large companies taking some initiative for innovation. They have already produced two concept cars with these wheels.

The unsprung weight is not that big a deal, really the inertia from the rotating tire is so great that the addition of some stationary components in the middle don't add that much.

While the angular momentum of wheels and tires does make a pretty large contribution to overall vehicle inertia, the fact that the wheel is rotating won't influence the specific issue of unsprung mass one way or another.

The problem with wheel motors has historically been unsprung mass (the mass of the portion of the car that moves with the wheel, rather than with the chassis -- typically the tire, wheel, brakes, suspension upright, and half of the driveshafts, springs, dampers and suspension arms).

The problem with unsprung mass is that it lowers the amount of available friction (for cornering, acceleration or braking) on bumpy roads. What happens is that the inertia of the unsprung mass as it's cresting a bump partially or completely offsets the downward force of the weight of the car, and the tire no longer has any normal force with which to create friction.

A good active suspension can help by measuring the force of the tire on the road and attempting to keep it roughly constant (by actively shoving around the suspension). But historically active suspensions have been energy hogs, soaking up something like a liter of fuel per hundred kilometers. It's possible that newer power electronics and an attempt to actually focus on energy efficiency could reduce that, but it's likely to be expensive and complicated in any case.

Two concept cars with this technology:

Eco-commuter Heuliez Will http://www.treehugger.com/files/2008/11/active-wheel-afforda...

Performance roadster Venturi Volage http://www.autobloggreen.com/2008/10/02/paris-2008-venturi-v...

I've been excited by the possibility of in wheel motors ever since I first heard of them because of the combination of simplicity of the motor, and the massive simplification of mechanical systems of a car. You no longer need all the bits which connect your inefficient internal combustion engine to the wheels, and those bits lose a lot of energy, somewhere around 50% according to what I've read. There is one company that makes buses with wheel motors which quadruple the fuel efficiency of the current best diesel bus, and of course there is the electric mini prototype which got a lot of hype a few years ago.

My biggest problem assessing the technology is my complete ignorance of the mechanical/electrical engineering issues involved. One engineering grad student argued that wheel motors were no good because they destroyed the control of the car by putting all the weight at the very bottom, and that the motors were going to be subject to a lot of shocks in real world use. I don't know enough to evaluate if that is true or not, but I'm hopeful. Anyone here know more?

"There is one company that makes buses with wheel motors which quadruple the fuel efficiency of the current best diesel bus"

Given that buses are surpassed only by garbage trucks in the number of stop and starts they make in a given distance I suspect this has much more to do with scavenging energy during braking than it does with the fact the motors are in the wheels.

If wheels contain the motors and th motors can operate independently, it makes some really interesting things possible like rotating the car in the position (wheels on other side of the car roll to different directions).

Great concept, but the article lacks any teeth. And the links don't work. Anyone have better links -- is Michelin really developing this seriously?

Here is the Michelin page for the Active Wheel: http://www.michelin.co.uk/michelinuk/AfficheServlet?Rubrique...

But for much more detail check out the press release (pdf): http://servicesv2.webmichelin.com/frontnews/servlet/GetEleme...

So what happens when you have a flat tire? You're extremely screwed?

As long as the lithium ion battery is the best we got, there will be no mass replacement of combustion engines with electric. There simply isn't the energy density. Also, lithium supplies aren't sufficient.

Energy density isn't nearly the as big a problem as lifespan and cost. You have to move some things around, but if you stick the suspension and the engines in the wheels, there's room for > 500 liters of battery in most cars. Th!nk gets about 150 L in a microcar.

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