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If you read my previous post the additional weight is just 4.4 lbs.
When i first saw this my Initial reaction was that that was simply not possible. The pancake style DC motors are not light, and the tire, and rim still need to be there. How could that not just be added weight.

However i followed the link and saw that they removed the rotor and brake calipers. Using the motor to regen brake. In light of that, and a light (read $$$) DC motor and rim, i could see such a small increase in unsprung wieght.

A little tangental, in the performance crowd an extra 5 lbs per tire is a very significant increase. But that could probably be forgiven when the power and torque curves were looked at. As well as the dynamic power and braking algorithms that could be applied to a truly independant 4 wheel drive system.

One note from the article is that they mentioned not currently having a manual back up brake system. Maybe someone who knows more about DC motors could tell me what the failure mode is with regards to regen braking? IE. if the motor loses connection with the rest of the car will it apply full brake, or will it spin freely? I realize it might depend on the DC motor but if you know i'd be interested.
 

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I have been thinking about a back-up brake system and the thought of fly-by-wire braking made me a bit uneasy. Sure we have fly-by-wire airplanes and they work just fine but NO physical brakes? Burrrrr.

So, I was thinking how can we have a back-up system that will make everyone feel safe and not add much weight. Remember, we are counting on the removal of the disk brake assemblies to make the wheel-hub motors light enough. Since the unlikely failure of the fly-by-wire braking system would result in the vehicle being transported back to the shop for extensive repairs I recommend a one-use emergency braking system. I'm thinking along the lines of the new table saws that stop the blade if you accidentally touch your skin to it. These brake systems disintegrate and have to be replaced if used. I think this type of disintegrating system would be a perfect match. It only has to be used to stop the car once and would have to be replaced along with the other major components, should the fly-by-wire brake system fail. Very light, probably inexpensive and makes everyone feel all warm and fuzzy. Nothing like that feeling when you try to stop your car and the brake pedal goes directly to the floor and you remember that your emergency brake has been frozen with rust for the past 5 years! ;)
 

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Discussion Starter · #24 ·
If you read my previous post the additional weight is just 4.4 lbs. In addition, these are not even in mass production yet. Wait until all the major automotive companies and their vendors start optimizing the design. I predict that in 10 years 4-wheel-hub motor configurations will be standard on all cars and that their un-sprung wheel weight will be of no concern.
I read your post after submitting my post ... :eek: The article that I was mentioning was based on an analysis of Mitsubishi's iMIEV Colt EV from 2005. (I don't recall the source.) Quoting from an article on Wikipedia: MIEV motors are constructed using an in-wheel motor rotor, an in-wheel motor stator, a rotor bracket, stator bracket and inverter directly behind the brakes. (Source: http://en.wikipedia.org/wiki/MIEV)

Images of the MIEV motor show that it is much more bulky than PML's "pancake" brushless electric motors used in the Mini EV prototype. However, the Mitsubishi motor includes the required rotor, brakes, etc. that the Mini EV does not include.

According to the following article, the 2005 Mitsubishi Lancer Evolution IX "has a top speed of 111 mph and weighs 1,590 kg, just 120 kg more than the standard Evo IX". (Source: http://www.carpages.ca/go/conceptcars/2005_mitsubishi_lancer_evo_ix_miev_concept.aspx)

Obviously, the weight difference between ICE and EV is decreasing ... perhaps someday the EV will weigh less!
 

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Discussion Starter · #25 ·
Since the unlikely failure of the fly-by-wire braking system would result in the vehicle being transported back to the shop for extensive repairs I recommend a one-use emergency braking system. I'm thinking along the lines of the new table saws that stop the blade if you accidentally touch your skin to it. These brake systems disintegrate and have to be replaced if used. I think this type of disintegrating system would be a perfect match. It only has to be used to stop the car once and would have to be replaced along with the other major components, should the fly-by-wire brake system fail.
Sounds like a great idea - hopefully it can get past the various transportation regulators ...
 

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schreeeeeeeeeech

I'm thinking along the lines of the new table saws that stop the blade if you accidentally touch your skin to it. These brake systems disintegrate and have to be replaced if used. I think this type of disintegrating system would be a perfect match.

What i would worry about with the system described above is that, unlike the table saw, ti would be undesirable to lock up the wheel in the even of a brake failure. some progressive application of the brake would be needed.

I agree that the emergency brake system should be compact and light weight. It should also be a completely independant from the primary brake system.

So i was thinking about it. The DC motor sits on a shaft and is bolted to the rim. It spins around the shaft and that moves the wheel.
if the inside face of the DC motor had a thin steel plate attached to it. a friction brake could be used. Obviosly this would be a system thatt would not hold up to heavy use but should be able to stop a car one time and allow for gradual application/reapplication of the braking force.

As a side note. I wonder if ABS would be easier or harder to implement with a regen system.
 

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As a side note. I wonder if ABS would be easier or harder to implement with a regen system.
I can't say this for certain, but it seems to me that an ABS brake could only be pulsed dozens of times a second, whereas a motor could be pulsed many, many times that, or it might be able to apply a continuous rolling drag with no pulsing at all.
 

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Yes! The use of motors and controllers gives you basically robotic control over the wheels. They can be pulsed, slowed, reversed, sped up, made to keep from skidding right down to the smallest degree. Four wheel-hub motor control will be an amazing advance. After the software goes though a few generations people will be amazed with the amount of control. Like a modern day fighter jet. The computers make adjustments so fast that without them a human cannot fly it. I would like to call this four wheel-hub control, "Wheels alive". :)
 

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regen braking

Regen braking only on the front wheels will still recover most braking energy. As your auto mechanic will attest by the relative wear of your brake pads, your front brakes do about 75% of the braking. This is because the vehicle's weight shifts forward during deceleration, giving the front tires way more traction. That's why ABS, when it kicks in, usually has to back off the rear brakes, as they can't do much braking without locking up the rear wheels.
 

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Regen braking only on the front wheels will still recover most braking energy. As your auto mechanic will attest by the relative wear of your brake pads, your front brakes do about 75% of the braking. This is because the vehicle's weight shifts forward during deceleration, giving the front tires way more traction. That's why ABS, when it kicks in, usually has to back off the rear brakes, as they can't do much braking without locking up the rear wheels.
Well, if you have the wheel-hub motors on all corners then you might as well use them. Why use brake pads in the back and waste that energy? Are you suggesting just using two wheel-hub motors? If so for cost? Having complete control over all four wheels gives you all kinds of options for safety and performance. You can also have smaller motors in each hub. If you only have two hub motors they will need to be twice as powerful and thus more massive. I think having four wheel hub motors is the way to go to for safety, redundancy, performance, etc. Of course the cost could be an issue but inexpensive cars will probably just have one central motor anyway. We will just have to wait and see what the engineers come up with. Can't wait to see them on the show room floor! The thought of making a very light rail car using production wheel-hub motors and a powerful nanotechnology lithium-ion (or other technology) battery keeps me smiling. Probably the kid in me.
 

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Volvo ReCharge concept with in-hub motors.

The 2008 Volvo ReCharge concept, a flexfuel plug-in serial hybrid with individual electric wheel motors and batteries
that can be recharged via a regular electrical outlet, is slated to go into production in 2010.
This vehicle is even more ambitious than the Volt...should be interesting to see what becomes of it.
Check it out:
http://www.conceptcarz.com/vehicle/z14099/Volvo_ReCharge_Concept.aspx

 

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...is slated to go into production in 2010.
Guy, I love this concept and have been following it for a while but can you please give us the reference to where you heard that the project is a go? I'm pretty sure it's still at concept status but I really hope I'm wrong! An advanced hybrid with 4 wheel-hub motors is top on my list, even at a steep premium.

Buying this Volvo is buying a Ford but I don't think the ReCharge is the big secret project at Ford. For one...

"According to people close to Mulally, he is looking at selling Volvo despite Ford's repeated statements that it intends to hang on to the brand. He also hopes to kill off the ailing Mercury brand."

http://www.theaustralian.news.com.au/story/0,25197,23588928-36375,00.html

Secondly, I feel the the secret project going on at Ford (My belief) will be much more radical in terms of light weight, aerodynamic body design. Think stealthy fighter jet (Saab like perhaps - ironically Saab is owned by GM). The ex-Boeing CEO will probably take the automobile in that direction. He has more belief than any automobile company CEO on the planet on the virtues of light weight, aerodynamic design. I'm waiting for big news from Ford, I just don't think the Volvo ReCharge is it.
 

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Please do tell when the first hub motors are announced for a production vehicle. I need to know when to implement my hub motor replacement stand idea (Easy-hub) :D
 
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