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Old 12-30-2008, 07:54 PM   #11 (permalink)
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We've hashed this out before, but here are the problems with hub motors:

Hub motors have to handle huge amounts of current, since they're at a fixed 1:1 ratio with the wheels. That means lots of low-end torque, and thus heavier insulation than a motor with reduction gear.

As part of the unsprung weight of the wheel, the hub motor must be able to withstand road impacts directly. Thus, stronger construction and even more weight.

Because it's outboard and in the wheel, the hub motor must be sealed to prevent dirt, water and junk from getting into the unit. A sealed unit is much more difficult to cool properly.

The Hi-Pa motor weighs 66 pounds. 4 x 66 = 264 pounds. You could install two Warp 9 motors for that much weight and get far more power.

BTW, the Tesla doesn't use hub motors. It uses a single AC drive motor coupled to a fixed 8.28:1 gearbox, so it still has axles.

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Old 12-30-2008, 07:56 PM   #12 (permalink)
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Quote:
Originally Posted by Christ View Post
So you couldn't use a single controller and two contactors?

controller would send the signal to both contactors, which would turn the engine's power on/off as necessary... I don't see how this wouldn't work out...

A long time ago, a local mechanic told me that you couldn't put two engines on a car without them being coupled somehow... I laughed at him and drove a go-kart with two 5 hp briggs direct-drive engines on it into his shop, one engine controlling each rear wheel.

This controller per motor thing seems kind of speculative, honestly, I just don't see a real reason that it couldn't work.
I believe the Zilla controllers can drive more than one motor by wiring them in series or parallel, though I think they must turn at the same speed at all times. You could break one or both with contactors, but contactors tend not to last very long if they have to break a few hundred amps every time you turn a corner.
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Old 12-30-2008, 08:02 PM   #13 (permalink)
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Quote:
Originally Posted by Clev View Post

BTW, the Tesla doesn't use hub motors. It uses a single AC drive motor coupled to a fixed 8.28:1 gearbox, so it still has axles.
I thought something like this, so I went and looked at the site again... I didn't get specifics on the gear ratio, but it does use a single motor.

Also, the hub motor idea could be more pheasible when the hub IS the motor. Which has also been done.

The design can be DIY'd by making a magnetic induction motor where the armature is stationary and the "housing" is the mobile part. Add a inner bearing race to each side of the armature, and an outer race to each edge of the "housing", and press them together. Mount a tire on the "housing" and you've got an electrically operated tire, where the center stays stationary (so it can be mounted to a car.) I'm not sure how to cool it or anything else yet though...

Check on back episodes of "Ripley's Believe it or Not" there is a guy that made a 1 wheeled vehicle (it's gas powered) but look where he sits... that's the same idea.
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Old 12-30-2008, 08:06 PM   #14 (permalink)
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Quote:
Originally Posted by Christ View Post
The design can be DIY'd by making a magnetic induction motor where the armature is stationary and the "housing" is the mobile part. Add a inner bearing race to each side of the armature, and an outer race to each edge of the "housing", and press them together. Mount a tire on the "housing" and you've got an electrically operated tire, where the center stays stationary (so it can be mounted to a car.) I'm not sure how to cool it or anything else yet though...
But how many amps can it handle for long periods of time? It boils down to amps vs. weight.
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Old 12-30-2008, 08:09 PM   #15 (permalink)
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Using one controller for two motors would be like not having a differential. And if the wheel with the shaft sensor spun, the other motor would get rapid, useless pulses. Hub motors would be OK for a golf cart used in a warehouse, or for creeping gridlock on a nice day, but are not a good choice for wider conditions.
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Old 12-30-2008, 08:40 PM   #16 (permalink)
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Quote:
Originally Posted by Clev View Post
But how many amps can it handle for long periods of time? It boils down to amps vs. weight.
Well, I can't personally tell you about that, I've never built it, nor do I have intentions to... but it's an idea that someone could run with, at least to get started on something like this.

Quote:
Originally Posted by Bicycle Bob View Post
Using one controller for two motors would be like not having a differential. And if the wheel with the shaft sensor spun, the other motor would get rapid, useless pulses. Hub motors would be OK for a golf cart used in a warehouse, or for creeping gridlock on a nice day, but are not a good choice for wider conditions.
Thank you, that explains it a little better. Now I would agree that it's kinda useless, in the sense that if one wheel hit ice, the other motor would be tryin to spin just as fast, without the secondary controller to prevent it.

On another note, traction control (at any throttle) is a nicety when using more than one motor, as each motor can use ABS type sensors to determine if one is spinning faster than the rest, and power to that motor can be limited, to prevent it from spinning.

Until hub-motors are researched, they can't be refined to a state where it might be more pheasible, and I've never heard so many people shoot something down without real information that it can't work, ever. (Not this thread, or even this forum... but I've asked about this A LOT, and everyone suggests that it's "nearly impossible" or highly impracticable.

No one ever seems to take into consideration that each "advancement" that's been made in automotive/engine/flight/just about any history started with something that "wouldn't work".
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Old 12-30-2008, 08:51 PM   #17 (permalink)
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How many watts would it take to make a car accelerate to only 10-15mph?

I am seeing the possibility of making my a semi hybrid and looking to see how many watts would be needed to push my car to those low speeds... it weight 3,000lbs

What do you say? 3,000 watts?
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Old 12-30-2008, 09:13 PM   #18 (permalink)
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>No one ever seems to take into consideration that each "advancement" that's been >made in automotive/engine/flight/just about any history started with something that >"wouldn't work".

We who make the advances have learned to choose our routes. You can get from San Francisco to L.A. via Denver, but it is a hard way to win a race. Nobody is saying hub motors won't work, just that their advantages seem likely to always be overwhelmed by less-obvious disadvantages. If technology changes, it is likely to improve both layouts equally.

Basslover - what's your acceleration time?
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Old 12-30-2008, 09:18 PM   #19 (permalink)
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Quote:
Originally Posted by Christ View Post
Until hub-motors are researched, they can't be refined to a state where it might be more pheasible, and I've never heard so many people shoot something down without real information that it can't work, ever. (Not this thread, or even this forum... but I've asked about this A LOT, and everyone suggests that it's "nearly impossible" or highly impracticable.

No one ever seems to take into consideration that each "advancement" that's been made in automotive/engine/flight/just about any history started with something that "wouldn't work".
Nobody said it wouldn't work. They are saying that it's impractical. For every advance made in motor technology that's applicable to hub motors, it's also applicable to non-hub motors. Hub motors already have their place: in scooters, golf carts, bicycles and other smaller lighter lower horsepower applications.
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Old 12-30-2008, 11:17 PM   #20 (permalink)
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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.

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