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Old 11-07-2018, 12:48 AM   #21 (permalink)
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The main advantage for hub-motors would be on small cargo vans, since it would allow a lower floor without major clearance issues with the drivetrain. And even though added unsprung weight is most often considered undesirable it might increase a few pounds to the payload...

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Old 11-07-2018, 02:07 AM   #22 (permalink)
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The only EVs here still using hubs are electric scooters. But once they get past the "toy" range, more powerful electric motorcycles (those with performance equivalent to 250-400cc motorbikes) are often chain driven.
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Old 11-07-2018, 02:41 AM   #23 (permalink)
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Hub motors aren't going to overcome their serious limitations. Maybe they could make sense in some lower speed delivery vehicle as CR mentions, but for vehicles where performance and reliability matters, they won't be used.

Conventional motors are shielded from the impacts of the road because they are protected by the suspension. Hub motors must absorb every impact the wheel encounters.

Good luck if you get a flat that requires a spare. Are you going to haul around another motor/wheel/tire assembly?
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Old 11-07-2018, 10:01 AM   #24 (permalink)
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I'm sure elec. hub motors are heavier than conventional cars regarding sprung wight, but how much so?

I would like to sit down and do some math on this one day.

Weight of brake rotors, calipers, pads, bearings, hub, wheel/rims, parking/emergency brake.... verses electric hub motor assembly.
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Old 11-07-2018, 01:32 PM   #25 (permalink)
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Quote:
Originally Posted by kach22i View Post
Article about funding and making them in China.
Protean Electric snags $84 million to produce in-wheel motors in China
Last time I looked into it (as deeply as a non-mechanical guy like me can) the issue was having the 'car' hanging off one side of the wheel, not both sides.

The hub motors on scooters, motorcycles, bicycles have the advantage of bearings on both sides of the wheel, connected to support arms on both sides of the wheels. So when the bearing surface wears a bit, the wheel is still level, the clearances still work, etc

On the car wheel, once the bearing(or bearings) start to wear .. just a little bit ... less than when the mechanical guys start to worry about it ... the tight tolerances on the rotor (rotating part) and stator (stationary part) of teh wheel motor ... get tighter. When there is enough wear to let the rotor rub the stator, metal shards come off, plug off the gap between rotor and stator ... and the motor comes to an ABRUPT halt. The wheel LOCKS in place and SKIDS the rubber off.

This sort of catastrophic failure was seen ... rumor only ... since NO ONE in industry wants to talk about things that they try that FAIL ... starting before the first set of tires was worn off to about midway on the second set of tires. 20,000 miles to 60,000 miles.

I have yet to read about a fix for this. If someone does figure it out, it will likely be patented ... so perhaps there are several companies with a magic solution already. But I have seen no evidence so far.

On this topic ... is there a technical reason why car tires and suspension don't use support (and bearings) on both sides of the wheel? Or is it just that it makes the car look goofy?
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Old 11-07-2018, 01:50 PM   #26 (permalink)
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But the electric hub motors still require all of those things. It's an additional weight, and a non-trivial additional amount of weight at that. I'd be curious on the math too.

This got me to thinking... What if conventional wheels could be made lighter weight by moving the braking components off of the wheel? Somehow slow the driveshafts or differential rather than the wheel directly. I suppose conventional brakes would still be required on non-powered wheels. I'm sure it's not a good idea, otherwise people would have done it already.

That's my point though, that if hub motors were a great idea, we'd be using them already. They have been around for over a hundred years, so it's not a new idea.
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Old 11-07-2018, 05:11 PM   #27 (permalink)
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Quote:
Originally Posted by redpoint5 View Post
This got me to thinking... What if conventional wheels could be made lighter weight by moving the braking components off of the wheel? Somehow slow the driveshafts or differential rather than the wheel directly. I suppose conventional brakes would still be required on non-powered wheels. I'm sure it's not a good idea, otherwise people would have done it already.
Inboard brakes have been done before, mostly on race cars but also some production cars. The biggest issue for production cars is packaging.

The main advantage to inboard brakes is the reduction of unsprung weight but the invention of carbon disc has reduced that advantage.

Attached are two race setups. The first is on the rear axle of a sprint car. The second is a Lotus F1 car
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Old 11-07-2018, 05:19 PM   #28 (permalink)
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That implementation works because it's either a solid axle, or the portion of the axle that the brake is on is fixed. I'm wondering how it could work on an axle that pivots, such as on vehicles with independent suspension.
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Old 11-07-2018, 05:25 PM   #29 (permalink)
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Quote:
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That implementation works because it's either a solid axle, or the portion of the axle that the brake is on is fixed. I'm wondering how it could work on an axle that pivots, such as on vehicles with independent suspension.
You attach the calipers to the transaxle
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Old 11-07-2018, 05:27 PM   #30 (permalink)
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Quote:
Originally Posted by kach22i
Just scroll down to the bottom to see Local Motors "Olli" self driving box/shuttle.
I like the Olli best of all the shuttle buses I've seen. Mainly for the interior.

Seventeen posts since yesterday? The idea is a non-starter and here's why: The motor/wheel has to integrate into the rest of the architecture. The struts, arms and springing don't go away. Take a step back, and the solution appears to be to put the motor at the end of a swing arm, with internal gearing.

No high unsprung mass and with two/four motors you get torque vectoring.


https://insideevs.com/zf-presents-el...urban-vehicle/

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