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Old 12-31-2008, 12:07 AM   #21 (permalink)
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Quote:
Originally Posted by Bicycle Bob View Post
Basslover - what's your acceleration time?
With the 2.4L 150hp engine it take I think like 7 seconds to 60 flat out.

Every day, to 15 or 20mph, I think anything that is faster than walking would work. What do you think, 5-6 seconds to 20mph accelerating normally? If not less...

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Old 12-31-2008, 12:16 AM   #22 (permalink)
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I think normally driving, 30mph usually comes in about 8-9 seconds, maybe 11 tops. Creeping along on a summer day, noone else around, in the country, I can drag it out as long as 1 min to get to 40mph. (mostly at the top end though, since I won't let the engine rev past 2k when I'm just "out" driving.)

This, of course, is in Granny... my old Civic (officially being parted out) I don't think I could take more than 15 seconds to get to 30... so take what you will from this.
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Old 12-31-2008, 12:34 AM   #23 (permalink)
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I'm a complete novice when it comes to Electric motors/Controllers of any sort (picking brains on the Internet until I get it right)...but I have no bias against Innovation.I doubt anyone on this board does.

What I do have is an empty wallet and not enough spare time. Many Ecomodders are probably similarly limited. I plan on building my own EV one day-when finances allow-and I can tell you right now that every part of my design will outright STOLEN from the most proven and reliable designs out there. I forsee enough difficulties and setbacks without trying to trailblaze new paths, particularly when I don't understand the existing ones too well yet...

"Not Practical" isn't an insult, it's just a descriptor-often it's just relatively informed opinion. Having said that, I don't think any poster here would tell you not to try something just because of 'untested technology' or 'impractical design'...it's just a shorthand for:

1) nobody's quite got it right yet, prepare for lots of setbacks and
2) have lots of money and time to burn-and also
3) you may have nothing to show for it at the end.

If you have enough determination, time and money, go for it-you could be the next Henry Ford or Ferdinand Porsche.And if anything really good comes out of your sweat and inspiration, I don't think there's any one of us who won't grind up our words over a Double-fudge sundae and chow down!
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Old 12-31-2008, 01:11 AM   #24 (permalink)
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Quote:
Originally Posted by Christ View Post
Once again, I would like to iterate that it's not mainly on this forum that I got that hint of negativity toward things that haven't been done yet.. nor it is primarily on this particular subject... it's just really common that people dismiss things b/c of what "can't be done" or "won't work" because "the numbers say so" and most of them don't even double check the paper part to make sure that it was all correct...

I guess what I'm saying is that a lot of people are more willing to find every reason something won't work, and spend more time making excuses than getting results. If everyone spent more time working on things, even those that are guaranteed to fail, rather than spending all that time thinking of every reason it won't work, they'd probably find a way to make it work.

Kinda falls into the "it doesn't benefit me, directly, so why should I spend my time on it?" argument...

But, I digress. Back on topic - I still like the 600HP E-Mini Cooper I posted awhile back in another thread. It had hub motors.
The original poster wants to use hub motors on his Dodge Caravan and wants to know if he can. The answer is, "yes, but it's going to be experimental or one-off, very expensive, slow and short-lived." Any other answer is promising unobtainium.

I found the site for the Mini Cooper, and was underwhelmed by the information. No information on voltage and amperage, duty cycle. Hell, maybe it's 0-60 in 4.5 seconds because these motors only go to 60 mph. Frankly, 0-60 in 4.5 seconds is a bit underwhelming for an AWD car with 600 hp on tap--especially 600 electric hp.

That demonstrates the problem with wheel motors right there. Because there's no gearing, you ONLY get 0-60 in 4.5 seconds. White Zombie, with 2-wheel drive and single reduction (differential), does 0-60 in well under 4 seconds with about the same hp.
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Old 12-31-2008, 05:09 PM   #25 (permalink)
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Lot of naysayers on hub motors.

I suggest people look up BluWave's hub motors, they are quite impressive: All wheel drive built in, regen breaking, and normals breaks, additionally the ECU coordinates all traction issues.

Another interesting hub is Michelins. Their's has everything mentioned before, but also has suspension built into the wheel to remove most of the unsprung weight.

As far as efficiency these motors run around 95% efficient and need no transmission and are all fully capable of highway speeds.
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Old 12-31-2008, 06:17 PM   #26 (permalink)
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Quote:
Originally Posted by Blue Bomber Man View Post
Lot of naysayers on hub motors.

I suggest people look up BluWave's hub motors, they are quite impressive: All wheel drive built in, regen breaking, and normals breaks, additionally the ECU coordinates all traction issues.

Another interesting hub is Michelins. Their's has everything mentioned before, but also has suspension built into the wheel to remove most of the unsprung weight.

As far as efficiency these motors run around 95% efficient and need no transmission and are all fully capable of highway speeds.
BluWave motors are 100 pounds each, all unsprung, and each produces 61 hp peak and 27 hp continuous. The Michelin units are liquid cooled (meaning hoses to each wheel), produce 67 hp each, and have to have a second integrated motor to handle the suspension bits.

More importantly, to the original poster who wanted to use hub motors, none of these are real products yet. Michelin's Active Wheel concept has been around since 2004, with no release in sight.
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Old 12-31-2008, 06:26 PM   #27 (permalink)
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4 27hp cont. motors on a car around 2000-2500 pounds would probably outperform a corvette. Comparing hp ratings of electric motors and ICE is not really apples to apples.
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Old 12-31-2008, 07:17 PM   #28 (permalink)
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I can see this topic has been dredged from the ancient past...

Quote:
Originally Posted by LostCause View Post
Issues that come off the top of my head include:

1.) Lower efficiency

While motors (especially the AC variety) tend to have very linear torque curves, they have a speed of most efficient operation. Using a hub motor, which almost certainly means it will be direct drive, forces the motor to operate under a much wider speed range. Generally, the faster the motor turns, the lower its efficiency due to friction.

Many of the top solar cars use direct drive hub motors, though. I've forgotten the motor brand, but it is extremely expensive for its output and extremely efficient.
Since efficiency is lower at higher speeds, it seems to me like hub motors have the advantage in that regard, because even the 8" trailer wheels on the trike kit of my Burgman, which are far smaller than most car tires, are only about 2,000 revs per mile at a quick guesstimate, (I don't know the exact circumference of the tires), which is much lower speeds than I've seen for ANY central motor in ANY design so far. This seems to me like a much narrower speed range, really. Especially compared to the Tesla, with it's 13K redline.

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Originally Posted by LostCause View Post
2.) Higher Unsprung Mass

Hub motors are physically attached to the wheels, increasing their weight. From a performance and design perspective, lowering the unsprung weight to sprung weight ratio is desirable. Heavy wheels exert large forces on suspension members, causing their required strength (and thus weight) to increase.
That I can see as being a concern. My primary focus with hub motors is reducing un-needed weight from the car as a whole, and when I take a light truck like a Chevy S-10, and start weighing out the components, it starts adding up REALLY fast. I bought some lowering spindles for a truck I had once, and each one was 20-30 lbs. EACH. Then you had the weight of the brake disc, (which I thought was undersized), plus the brake caliper. With only 180hp on tap with the stock V6, I can't imagine putting 50hp at each wheel would add a significant amount of weight if it were to replace redundant components, drive shaft & drum brakes in the rear, spindles, discs & calipers in the front. Even better would be to integrate the motor into the rim itself, saving yet more weight, and eliminating a (granted no longer common) point of failure.

Quote:
Originally Posted by LostCause View Post
3.) More Complex Drivetrain

Some high-end electric cars, such as the Tesla Roadster, use hub motors. The average DIYer most likely shies away from the technology because it is easier to drop in an engine replacement than redesign the drivetrain. Axles would have to be lost, kingpins and steering knuckles redesigned to accomodate the motor and its wiring, and special rotating electrical contacts fabricated to power the hub motors. While it is not impossible, hub motors probably rate low on the cost/benefit ratio list.

- LostCause
Incorrect as has been stated in this thread. Also, rotating electric contacts? Has no one ever heard of stationary-winding motors?

As for cost/benefit, ANY retrofitting is low on cost/benefit by nature. Even just replacing the engine with a motor. But as for mass production, the reduction in the numerous little parts that exist between engine and wheel is a massive savings for any high-volume auto manufacturer.

Really, as far as things go, I see hub motors as having the most pro's and fewest cons, of ANY electric design.
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Old 12-31-2008, 09:30 PM   #29 (permalink)
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Originally Posted by Blue Bomber Man View Post
4 27hp cont. motors on a car around 2000-2500 pounds would probably outperform a corvette. Comparing hp ratings of electric motors and ICE is not really apples to apples.
Not if they're directly connected 1:1 to the wheels.

Besides, you're comparing 4 x 27 hp to an ICE. I'm comparing it to a 150kW AC motor and a transmission. The single motor with transmission will be cheaper (one motor/one controller) and far more powerful. Even having fixed ratio inboard motors with axles (a la Tesla) keeps the motor out of the damage area, allows standard suspension/braking components and keeps the motor as sprung weight.
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Old 12-31-2008, 10:50 PM   #30 (permalink)
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I don't necessarily agree w/the issue about 1:1 coupling w/ the wheels, only b/c if you read back through bennelson's E-metro build - he has a video taking off in 3rd and 4th gears, working up to 30mph in 13 seconds each time...

Those two gears are as close to 1:1 as most transmissions will get, and having both of them showing the same acceleration curve shows that the relative torque output of the engine (which most certainly ISN'T 27 HP, being from a forklift which has insane reduction in the transaxle) is more than enough to move the car.

I'm sure that what actually would happen in this case is that even though the 4x27 car might accelerate something comparable to a Corvette (I dunno about this one either.), it will also use more amps to get to speed being directly coupled with no option for gear reduction or changeable speeds.

The Tesla uses a 14krpm AC motor coupled to a single speed gearbox... but if you look at the "dyno" info for the tesla's motor, it develops and MAINTAINS a plateau of peak TQ from 0-6krpm.. while any other car is having to build up that torque to get moving, an e-car already has it, which means that coupling it 1:1 even on a take off would have an ICE power equivalent of launching a 1:1 (final) ratio gear at peak TQ in the RPM range.

Now, I wait for someone to call me out for not mentioning that tires technically change final drive ratio to a greatly underdriven ratio.

Frankly, I still don't think that the e-motor would have much trouble taking off, coupled exactly 1:1 with a wheel/tire combo of reasonable size compared to the power output of the motor. 27HP is more than enough to move an average 13" tire and make it accelerate decently.

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