I’m on my second orbital sander. The first was a Porter Cable which was great but wore out. When I turned it off it quit spinning right away. I’m now using (have about used up) a cheaper brand model which continues to spin long after its turned off. You have me thinking that the reason is that the cheaper brand saved a few pennies by not including a resistor/brake.
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All that said, it seems like some sort of mechanical “emergency brake” would be required. That puts things back into heavier hub land.

“It can be done in a passive way so even if the battery is flat it can still stop.”

Don’t you mean even if the battery is fully charged?

“Unsprung weight!!!!!” is an argument I see often about the Protean motors. Usually by people who utterly failed to research the motor. I blame the authors of these articles for that as they have not addressed it in years. Since the second year these motors were out the bloggers and news authors report the weight but never mention the hardware that they replace inside the wheel. They also do not run comparisons of before and after weight.

If you read the data on the company’s website or the historical data starting with the mini QED you will see that there is a large amount of unsprung mass being replaced by the Protean Motors.

Reaching back to the mini QED quoting the article I first read: http://www.gizmag.com/go/6104/
“The in-wheel motors and magnesium alloy wheels, and tires, have a total mass of 24kg. The original assembly mass on the MINI One was 22.5kg.” I have to interject here that is a difference of 3.3 pounds not 66, and on a mini whose braking hardware weighs less than most. To finish the quote: “With so little difference in unsprung mass (the brake hubs and discs have been removed), and full regenerative braking, the ride is claimed to be no different.”

I have had some argue that using an electric motor to replace the friction brakes is a risky proposition. The thing to keep in mind is that these motors can generate 200hp each of stopping force. It can be done in a passive way so even if the battery is flat it can still stop. Try this experiment sometime: take an electric motor, hang a weight on it, get it spinning then short the leads (not by hand preferably). The motor will stop the load due to conflicting magnetic fields inside, and if it is large compared to the load it will happen very quickly.

Their description in the same article about the hypothetical hybrid car that would use the motor was remarkably similar to serial hybrid cars like the Chevy Volt, except they imagined a flywheel would capture energy from regenerative braking.

And with with electric/active suspensions 4wd vehicles could ride lower to the ground on smooth roads and raise themselves up when more ground clearance is needed.

Apparently Michelin had programmable suspensions in a working prototype in 2004. And here’s a great 2008 video of their prototype showing what the suspension can do.

That brings me to another favorite of mine: complete active suspension/wheel motor/brake/steering units with power electronics and a standardised vehicle interface (both electrically and mechanically).

Building a car then becomes simply designing a strong box for the passengers to sit in and making sure it has sockets for those standardised wheel units on all corners. Then connect the cables and you have a car!

“A stock 2007 Ford Focus was compared with an identical vehicle modified with 66 lb (30 kg) of ballast fitted to each wheel. The weight was distributed between rotating and nonrotating unsprung masses as to broadly replicate Protean Electric’s PD18 (18-in diameter) wheel-hub-motor unit. The project plan included three phases of analysis and testing.

Phase 1 focused on modeling of different modifications, including suspension spring, bushing, and damper rates, and different tires and pressures, and their effects on the IWM-equipped vehicle. It was determined that simply fitting a standard Focus ST suspension (an upgrade on the stock base car) would be a good practical solution.

In phase 2, the stock vehicle was modified with the Focus ST suspension. This setup included revisions to the front and rear spring rates, dampers, and the rear antiroll bar. In phase 3, the Focus with the modified ST suspension was retested. The process included a subjective vehicle assessment, objective ride and handling tests, on-road shake measurements, and two-post shaker rig measurements.

The studies concluded, and the presenters argue, that while the vehicle carrying the greater unsprung mass at each wheel did display perceptible differences compared with the stock vehicle, those differences were minor and can be mitigated using “normal engineering processes within a product development cycle.”

By fitting the upgraded ST-level suspension to the car replicating one equipped with Protean PD18 in-wheel motors, the vehicle’s handling and on-center tracking were improved back to reference. Overall, the effort conducted by Protean Electric, Lotus Engineering, and Dunamos may help convince skeptics that the addition of 30 kg of unsprung mass per corner will not adversely impact overall vehicle dynamics and can be addressed fairly easily with cost-effective countermeasures.

http://ev.sae.org/article/9493/

Furthermore, it seems to me if you’re using electric motor to control the vehicle height rather than liquid/air shocks then the unsprung weight wouldn’t matter. Feed a bit more power to the motor as the wheel travels downward in order to maintain the same amount of force between vehicle and wheel, capture that power back as the wheel comes back up.

Michelin, I believe, used motors rather than springs and shocks in their suspension.

The 4 main issues so far (as I see them) are:
1 Cost. Two motors instead of one is simply more expensive. The differentials/driveshafts/reduction gears that are being used now are commodity items in the car business and therefore relatively cheap.
2 Torque. A high rpm low torque motor is smaller and cheaper than a low rpm high torque motor that is required for a wheel motor.
3 Unsprung weight. I am not that much of a car buff, but they say high unsprung weight negatively affects handling and ride comfort.
4 Exposure. An electric motor is still a quite delicate piece of equipment. You’ll want to have it in a safe, protected spot. In the wheel the motors are exposed to more vibrations and dirt.

Nothing in this list poses a fundamental problem. All can be overcome by better design, advanced materials and mass production. I am certain the in wheel motor will be standard in the future, but we’ll have to wait.

Why would there be a serious wear issue with the bearings? Like any wheel bearings they are supporting the weight of the vehicle and going around in circles. It’s just a matter of sizing them correctly.