Hipo AWD project

Technical discussion on converting internal combustion to electric
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Post by Johny » Tue, 25 Nov 2008, 02:27

There have been practical suggestions about improving diff efficiency such as using lighter oil (seeing as how DIY EV don't normally do the long trips).

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Post by Electrocycle » Tue, 25 Nov 2008, 15:06

yeah since you're generally running less power (less peak torque than the ICE engine launching in first gear), lower cruising speeds, and shorter trips, you can easily get away with using a lighter grade diff oil.
I'd try some the teflon treatment stuff too.
I think some gains could be had by running thinner oil in the gearbox for people who are using one.
It's not going to run nearly as hot as it would with its original engine, so the standard oil will be too thick, and cause a fair bit of drag.
Some manual gearboxes run auto trans fluid standard, and it might work well in other boxes in EV use.
A diff will still need a hypoid gear oil though.
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Post by MikeG » Tue, 25 Nov 2008, 15:08

acmotor wrote: Don't be fooled by the sales blurb of a wiki. Rotating mass (of say a drive shaft) is of little consequence to efficiency and consumes no power when cruising anyway. The drive shaft inertia is maybe 0.1% or less compared with the vehicles inertia. It is gears first and CVs then bearings in that order that waste power.
A good diff may be 85 to 90% efficient and the tailshaft 99.99% efficient. Its only loss being wind drag (tiny) and some uni joint loss if they are not straight. (still less than a CV at 30 deg).

"improved drive train efficiency" doesn't occur if the same mechanicals (gearbox and diff) are involved.


Let's get this straight... You think acellerating a mass consumes no power? That's bizarre... To turn a driveshaft, torque is applied. You can't have torque without applying power. A driveshaft not only connects the motor to a diff that in turn drives the wheel(s), it has its own mass and as such, even with the diff disengaged, it will require torque to accelerate. You seem to think it minimal, but the consensus is actually that it is sufficient to cause a loss in the order of 5-10% which in my opinion is substantial.

Now, you also say "improved drive train efficiency" can't occur... So you think a 20 year old diff will spin as easily as a new one? Sure if you rebuild your diffs, you may bring it up to spec, but I think it would be cheaper to buy new ones or get one off a newish wreck. Most components reduce in efficiency as they get older, even with excellent maintenance... Sorry if I didn;t make that clear in my previous post.

A popular modification in race cars is to replace the driveshaft with one made of kevlar fibre. Some think this is to reduce the sprung weight by 10kg, but the read advantage is in reduction of losses through the drivetrain. Similar to the reasons they use lightweight wheels. I've seen a car that should have put down big power numbers, put down less than stock to the rollers due to having 20" chromed steel wheels on the car. The wheels weighed more than twice what the std rims do, so the power loss through the wheels, even with the same rolling diameter was enough to suck up 20-30% (another good point for EV builders, if you have heavy wheels, replacing with lightweight wheels will give you more acelleration.

http://www.wheelfire.com/scontent/Wheel ... ?Brand=134

I don't want to come across as combative, I'm just trying to share my experience with you. Feel free to disregard what I say, and what is published elsewhere. But I recommend reading a little on the subject before you do so...

Going Faster!
Mastering the Art of Race Driving
by Carl Lopez
ISBN-13: 978-0-8376-0226-4

http://en.wikipedia.org/wiki/Drive_shaft

http://en.wikipedia.org/wiki/Electronic_Differential

http://en.wikipedia.org/wiki/Differenti ... al_device)

I can recommend the Motor Bookshop for quite a few excellent books. I've read quite a few on racecar suspension and chassis design...

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Post by tsport100 » Tue, 25 Nov 2008, 15:47

There are 2 separate subjects getting confused here. Accelerating a mass is not the same as energy inefficiency through a gear.

Any mechanical transmission of power through a gear has a % of energy converted to heat at the tooth face, hence the energy lost between input and output.

http://www.societyofrobots.com/mechanics_gears.shtml

I realise this isn't a text book reference but it's a good example. You'll see a Bevel gear (as used in a RWD diff) rated at about 70% efficiency. A differential crown and pinion has a helical type tooth cut which raises it's efficiency maybe 5-10%. In an open diff / planetary gear centre you also have a 2nd set of bevel gears that are straight cut.

You'll also see a Spur gear (as used in the final drive of a FWD) is around 90% energy efficient. Might help explain a few of the differences between FWD and RWD losses.

Accelerating a mass, especially in an AC powered EV is a totally different subject as due to the laws of inertia a significant % of the energy used to accelerate a car (mass) can be recollected on deceleration via regeneration. The only things that disipate energy when a car is at a constant speed is rolling resistance and aero friction.

(I think it's a classic that most Electric motors carry an energy efficiency rating but there is not even a recognised term for the equivalent measurement in ICE powered cars.. as they really don't want anyone knowing they are all only 15% energy efficient from tank to tire)

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Post by acmotor » Sun, 30 Nov 2008, 05:42

Mike G,

Your points re inertia are correct in concept but not in order of magnitude.
The inertia of a tail shaft is of almost un-measurable consequence compared with the 1 or more tonne of vehicle being accelerated.
In fact the 10kg reduction of weight for the kevlar fibre item is of far more consequence to performance as it lowers the overall mass being accelerated.

When an EV is cruising (as it is up to 90% of the time) the inertias are not an issue, and as someone mentioned, if you have regen then you get back a fair bit of what goes in when you slow down.
This is one of the big features of EV - energy recovery.

Sorry, it is a bit like oxygen free speaker cables. In theory correct but give me a break, your ear will never know. Coming from an electronics background, I have to laugh at this one ! Image

I agree that modern gearboxes can be more efficient, probably by a few percent or so. but.... this is often at the expense of robustness or longevity. There is only so much you can do to improve their efficiency.
The best thing is to do without them. e.g. by emotor design - hub motors will be the answer, when the unsprung mass is low enough.

Anyway, the issue is not one of big concern to EV converters.
There is no one feature of an EV that alone determines efficiency.
I would definitely not choose FWD or RWD on a supposed efficiency point.

The comment often made is that if a vehicle has low fuel consumption as an ICE then it will make a good EV. That does not mean that A FWD micra is a good donor. You need to consider other factors too !
I would much prefer a 318 beema with direct drive to diff.

tsport100,
Yes, a hard metal cross cut gear with clearance and roller bearing mounting, is the most efficient. There is only one reason they are not used in gearboxes (except some reverse gears) - They are noisy. I think it was Citeron who developed the angled gear (originally V shape) and remains to this day as their vehicle logo.
Modern hellically cut gears are less efficient than cross cuts but at least quiet due to the sliding nature of their contact. The options are heat or noise. Image

Guys,
Remember, the aim is to have an EV, and 5% efficiency one way or the other is not the issue.
It is good to throw these geabox ideas around as you soon realise that it would be best to do without one ! Image     
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Post by tsport100 » Sun, 30 Nov 2008, 08:49

I’d advise against mocking!

As the subject of this thread is about using an AWD chassis in an EV conversion I simply wanted to point out the losses of an AWD transmission, as they can be fairly significant.

I fully understand the demand for AWD with an EV as 2WD in any form is a compromise. With FWD you get good regen but due to the torque curve of Electric motors you get terrible traction problems. With RWD you get great traction but lousy regen.

If you’ve ever driven or owned a high powered Turbo AWD you’ll know they are by far the safest and most stable platform for fast driving. Wheel motors are the ultimate solution to this compromise and as they are direct drive there are no mechanical losses.

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Post by Thalass » Sun, 30 Nov 2008, 10:35

As has been mentioned before, a direct-to-diff drive is a good (IMO) layout for an EV. I'm hoping to do this myself, more or less copying the Electric Impreza.

The trouble is finding a controller that has two outputs.

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Post by acmotor » Sun, 30 Nov 2008, 11:10

No mocking ??? non intended.
The FWD/RWD point was raised and begged debate. IMHO there were a few misconceptions. As with all forums - be prepared to be flamed !Image
( I get it all the time !)
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Most controllers will run two motors in parallel at the same frequency.
Danfoss does. The motors naturally load share and in an AWD EV (direct diff drive) would produce a 'semi locked centre diff' type action, allowing only a few percent difference in speed front to back. Probably quite desirable for traction.
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Post by woody » Sun, 30 Nov 2008, 15:06

I would have thought that DC controllers/motors would also do parallel or series a là white Zombie
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Post by tsport100 » Sun, 30 Nov 2008, 17:19

IMHO you really need 2 separate inverters to run 2 motors other wise you lose many of the benefits of going AWD!

For example if there is no proportional difference between front and rear then you get many of the same problems as if you were running just 2WD. The amount of regen you could use would still be limited by rear wheel lock up on forward weight transfer and the same with acceleration, power application would be limited by front end traction as weight transfers to the rear. A "few" percent will only work for gentle driving as a viscous coupling at times seems able to go as high as a 20-80% split front to rear.

I imagine using 2 motors and one LARGE controller (not forgetting the Inverter has to either be double the KW rating or your motors have to half the power) would be alot like the old Audi Auattro with a locked centre differential. On corners the front wheels travel along a larger arc than the rears causing huge understeer with a locked centre diff as the front wheels try to wheelspin around every turn. In an EV using 2 AC motors that will most likely cause the front motor to regen (brake) around corners while the rear is driving.. and the tighter the corner the more it will front end regen. (unless the front has more traction in which case the rear will regen) A fairly counter productive way to drive a vehicle.

High performance AWD road cars get around this by using a viscous coupling that automatically sends power to the end of the car with the most traction. In an EV with 2 motors you'd need to do this with 2 separate Inverters run by a central speed controller using a accelerometer input + steering angle input (not an impossible concept to make work if you've seen any of the simple balancing robot projects built by school kids.. but definitely not an "off-the-shelf" project)

BTW It wasn't me you were mocking... but I wouldn't be surprised that you get flamed all the time, you invite it.

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Post by tsport100 » Sun, 30 Nov 2008, 17:37

BTW that "ProEV" Impreza previously mentioned runs 2 seperate inverters controlled by a PC running XP and some 'custom' motion control software.

I think a PC is probably OTT as this sort of thing has been done with something embedded and much cheaper like a PIC.

Again if you're interested I'd recommend researching balancing robots and home built Segways on the net to see how simple a system that uses accelerometer/gyro/pot inputs to control 2 motor outputs can be (relatively speaking).

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Post by acmotor » Sun, 30 Nov 2008, 20:56

Flame on ! That way we all learn. The thing is to know when you've been flamed and admit it. At least I can !Image

Your thoughts re power balance in AWD are fine.
My understanding and experience of AC drives is that they will naturally address much of this as standard, however there is no question that FOUR controllers and FOUR motors would be the optimum for control. Two motors is most practical for a conversion though as hub motors enter a whole new world of suspension change.

The power balance L to R is probably as important if not more important than the front to rear. Thus LSDs and lockers were developed, as you say actual locking can be bad F to R. (and L to R on a corner)

Keep in mind that the ASB and traction control principle is to keep all wheels rotating at much the same speed and avoid changes of speed that are not 'possible' for the vehicle.

AC induction drive steps in well here because of the 'slip' parameter.
Consider the case of 2 motors. Slip will be in the range of +-5%
Power will automatically transfer to the motor that is being held back from the demanded speed.( or regen from one going over the speed) Neither can lock up or go over speed by more than 5%.
Transfer of power to axle with most traction is electromagnetic without need of XP !

You can probably put some numbers on the relative F to R speed differences of an AWD when pushed in cornering. My first impression is that parallel AC induction could be quite tidy and very smooth.

The actual need for 2 controllers may be more for DC or brushless DC systems that do not have the natural bi-directional slip property of AC induction.
Cost and redundancy may also be factors.

4 hub motors under computer control still being the holy grail.

Does this make sense to you ? Image
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Post by tsport100 » Sun, 30 Nov 2008, 22:18

Make sense?

My full time job is as the owner of a business that has been working on an AC wheel motor project for the past 2 years and I have a patent pending on the subject. These wheel motors DON'T require any suspension modifications. We're also working on a drive system that uses 4 separate inverters and a central controller to drive and brake the 4 induction wheel motors.

What you describe as AC Induction 'slip' is probably best described as passive traction control in either regen or acceleration. For example under acceleration if any individual wheel loses traction relative to the others it will momentarily go faster than the drive frequency being applied and will therefore brake itself automatically until it's speed equals the drive frequency again.

It can also provide the same kind of traction 'balance' during braking (ABS is a modulated anti-lock system so not the same principle) and can provide a passive form of yaw control. I've seen test data from a car fitted with 4x BLDC wheel motors on a skid pan. The matching frequency input on all 4 motors meant that if either of the back wheels lost traction while pitched into a corner then that motor passively braked itself which reduced the yaw rate (i.e stopped the slide). Obviously slightly different with synchronous BLDC instead of asynchronous AC as there's no 'slip' but the reactions would be comparable.

When running separate motors in each wheel you also get a form of passive "brake steer" especially with AC induction as the inside wheels travel a shorter distance they brake slightly and this actually helps turning. The effect can be compared to how a tank of bulldozer with tracks turns, or how a bobcat excavator steers. McLaren had a feature like this years ago in F1 which was manually operated by the drivers via a 4th pedal, of course they started winning too much so it was banned.

I think a 'dumb' parallel system with front and rear differential mounted motors with maybe 5% slip is flawed as unless vehicle pitch is somehow compensated for then the whole system is compromised as I said in a previous post. A circuit for doing this is, believe me, not rocket science.

As a quick example, consider the difference in the size of friction brakes front to rear on any car you care to name. The fronts are ALWAYS bigger and for good reason. If you have ever driven a car with adjustable brake bias you'll realise how poorly it brakes the more rear bias is applied. Having a 'dumb' parallel system tying the front and rear motors together has a similar effect.

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Post by Electrocycle » Sun, 30 Nov 2008, 22:54

I think parallel front and rear motors would work quite well.
Remember we're not talking about really massive torque here. How many AWD cars have rear wheel traction problems under acceleration?
Usually the only way to get major wheelspin is to dump the clutch at high revs in first gear, which is producing way more torque at the wheels than your electric motor will.
When running separate motors in each wheel you also get a form of passive "brake steer" especially with AC induction as the inside wheels travel a shorter distance they brake slightly and this actually helps turning.
Is this with active control?
If your motors are paralleled left to right your inside wheels will see more load in a corner, and will produce more torque, trying to push the car straight - the old locked diff problem.
Running motors in series left to right (whether electrically or in software) gives the same effect as a normal open differential, and controlling them individually based on steering input, g forces, and traction can give the best result - with 100% of usable power making it to the ground.
None of this is highly necessary in a normal road car though, which is generally not going to be under full acceleration all the way around a corner!

A wheel motor at each corner with individual control is probably the best thing for efficiency and traction, but if you can get enough power into two wheel motors it's unlikely that it would be a major downgrade unless you're trying to put 200+ kw to the road without any intelligent control.
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Post by Electrocycle » Sun, 30 Nov 2008, 23:10

In tarmac racing, AWD doesn't usually doesn't have much of an advantage over RWD, unless you're talking about massive power (or it's raining!)

It's not hard to put 300kw to the road in a light weight RWD car, so unless you're talking substantially more than that, the AWD car is just carrying around a lot of extra weight and drive train losses.

Also, a tyre has a "traction circle". The more load you put on it in any one direction, the less it can handle in any other direction.
So, if you are using 50% of its grip for acceleration, you'll only get 50% of its lateral grip for cornering.
In the end, if you put a lot of power to the front wheels coming out of a corner, you'll understeer, which wastes time and requires you to go slower to maintain line.
Due to weight shift under acceleration, you'll never be able to put as much power to the ground through the front wheels as the rear wheels, so it doesn't make sense to have equal power capabilities at each end of an AWD car.
By the time you're going fast enough that acceleration has dropped to the point where you can put 50% of your power to the front wheels, you'd have no trouble continuing to put all your power to the rear wheels (again unless we're talking really massive power - which we are not because there are no batteries that can sustain that sort of power delivery - yet :))
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Post by tsport100 » Sun, 30 Nov 2008, 23:51

1) We're talking about electric motors that have 100% torque from Zero RPM. A medium sized AC Induction motor can easily have as much torque as a 5.7lt V8, but from 0 rpm, that's one of the best things about EVs. Multiply that torque through a final drive gear ratio and traction can be a real problem, especially in FWD. For example an AC Propulsion EV system which is only a 50kw continuous motor has 220Nm at the motor shaft but with a final drive of 8.25:1 that’s over 1800Nm (minus losses) at the wheels. What you’re talking about with 'dumping a clutch' is getting an ICE into it's peak torque range, an EV motor has that from zero rpm.

2) From experience I've owned both a 200Kw turbo AWD and 255KW RWD and there's no comparison as far as laying down the power is concerned. I can destroy a set of rear tires in less than 60 seconds with the RWD but with AWD the thing just launches with minimal fuss and in wet weather they are from different planets altogether. I clocked up 300,000kms in the AWD and I think I got the 2 inside tires to spin once, in the rain. The RWD requires that you pay attention to avoid wheel spin at all times and you simply can not accelerate hard in the wet.

3) The 'traction circle' only applies to corners but is exactly what needs to be compensated for. Just running a 'dumb' system will limit the amount of power that can be applied to the rear wheels by now much traction is available a the front. As you point out under power that is limited. The same applies to braking, the amount of regen that can be applied to the front will be limited by how much traction you have at the back before rear wheel lock up occurs.

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Post by tsport100 » Sun, 30 Nov 2008, 23:53

Yes I ment to say Active brake steer.

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Post by Electrocycle » Mon, 01 Dec 2008, 00:15

yeah, definitely no point having a dumb AWD system, unless it's of low enough total power than it never has traction issues (which would be the case in many commuter car style designs)

Even if an electric motor has 100% torque from zero rpm, an ICE has close to maximum torque from a fairly low rpm, and with a gearbox (especially auto with a torque converter) you can have a very high ratio between the engine and wheels, which means much higher peak torque figures at the wheels.

Dumping the clutch on an ICE also dumps all the engine and flywheel's momentum into the drive train, so again the peak torque applied is much higher than the specifications suggest.
From experience I've owned both a 200Kw turbo AWD and 255KW RWD and there's no comparison as far as laying down the power is concerned
If you have intelligent control of an electric motor though, you can really maximise the traction available, so unless you have massive power, the RWD layout is not going to lose out too badly.
I'm talking more in terms of an average car than a really high performance one, as I see this as being where the electric vehicle fits in. Getting enough sustained power to compete with high powered ICE cars from available battery technologies is not currently possible.

I have built and driven a race car with over 300kw at the rear wheels.
The car weighed 1060kg, and had no trouble putting the power to the ground with some careful throttle control.
At speed, full power was very usable, and it was faster than a V8 Supercar down the straight at Eastern Creek raceway.
The steering response was unlike pretty much anything I've driven, and is simply not possible with an AWD layout - due partly to the extra mass in the front end, and partly the extra load on the tyres.
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Post by tsport100 » Mon, 01 Dec 2008, 01:46

An average ICE has peak torque up around 3500rpm. The ENTIRE reason a EV can go without a multi speed gearbox and an ICE can't go anywhere without one is purely their respective torque curves, they are the inverse of each other so there's little point saying they're simular.

You're wrong about the gearing ok. I said ACP (which includes cars like the Tesla) have 8.25:1 final drive. You're average car has a 3.5:1 final drive diff ratio with a top gear of 1:1. The only time an ICE even gets close to having the same kind of torque as an EV at the wheels is in 1st gear, usually around 3:1. An EV has that torque ALL THE TIME, it's like taking off in 1st gear from 100kph.

I'm definitely NOT talking about average cars, not even slightly interested in the performance envelope of some shopping trolley. Perhaps you’re not aware that EVs these days have a 300kms+ range and can do 0-60 in 3 seconds on battery power, that's faster than anything short of a Veyron, and all for $0.01 a km.

It's pretty easy to calculate how long a battery EV will last when driven hard. Use the Tesla as an example. It has a 53kw/hr battery pack and a 180kw motor. Doing a flat out run 0-100kph takes 4 seconds and using all 180kw for 4 seconds consumes 200 watt hours (180kw-hr / 3600 seconds in an hour x 4). Best of all it can collect around 30% of that back via regen. At <200wh a run, it will take a significant number of runs (over 250) to deplete the 53kw/hr battery pack.

I presume as you've talking about a 300kw 'race car' that you're running slicks? If so that's hardly a normal level of traction and a race circuit is nothing like a real road. What sort of chassis and motor are you talking about? I’m going to guess something with a very small frontal area if it has a higher top speed than a 650hp V8 supercar.

Talking about AWD in racing… what car was banned for the Aust touring car championship because it won too many races?

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Post by Electrocycle » Mon, 01 Dec 2008, 02:15

The race car is an S14 Nissan Silvia (200SX). We were running street legal semi slicks on it, and it spent a fair while still street registered and running street tyres. They required a bit of care, but you could still make generous use of the engine's power once the speed was up.
At Eastern Creek we were hitting about 265km/h down the straight, after overtaking an ex V8 supercar that was running with us. It was on slicks and coming onto the straight at a higher speed. We had less weight and a wider power band than it did, with maybe slightly less peak power.

Even though an ICE has a point of peak torque, usually the torque curve is fairly consistent over a fairly wide rpm range. This is always a point of contention with ICE people, because they only look at the peak figure and not the shape of the curve, or the average value.

In an old dyno chart of one of my previous cars, making 110kw at the rear wheels, the torque value stays within 10% for the entire usable rpm range of the engine.
The power curve is fairly close to a straight line, just like an electric motor.
The only difference is that it doesn't continue to zero rpm, hence needing a clutch.
If the car only needed a 100km/h top speed it would have only needed second gear, and actually would have been quite happy taking off in second. Obviously the efficiency on the highway would have suffered though!

Funnily enough, that particular engine, making 110rwkw through a 30% drive train loss at 7000rpm makes the average torque about 215Nm.
Peak torque was about 225Nm.

The aforementioned race car was making over 600Nm of torque at the engine at peak power, and substantially more at lower rpm (it was tuned for midrange power rather than top end, and made over 300rwkw for more than 2000rpm - which is probably why we broke every custom billet drive shaft and gearbox part we could get made!), driving through a 3.9:1 final drive.
With the 3.2:1 1st gear, that's over 7500Nm torque available at the wheels on takeoff.


Oh yeah, doesn't the Tesla have a two speed gearbox?

Also, the GTR was "banned" because it was too fast for the competition, which is only partly due to its AWD design. It was unbeatable in the wet, but in the dry its superior power to weight ratio and massively more advanced suspension and chassis design played more of a part than the AWD.
Also in those days turbo engines had very peaky power delivery, which AWD helped get to the ground, but with more controllable engines (especially electric! some of that benefit is lost)
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Post by acmotor » Mon, 01 Dec 2008, 02:21

This is interesting discussion, go for it guys!
We are all coming from slightly different angles though.
I am more into the conservative road car, however the big advances will come from those who push the envelope.

This interests me very much...

[quote="tsport100"]
My full time job is as the owner of a business that has been working on an AC wheel motor project for the past 2 years and I have a patent pending on the subject. These wheel motors DON'T require any suspension modifications. We're also working on a drive system that uses 4 separate inverters and a central controller to drive and brake the 4 induction wheel motors.
QUOTE]

Ok, my concern, so to produce a hub motor, it must have the same weight and same moment of inertia as the factory road wheel for a conversion. i.e. same unsprung mass. (particularly in a high performance vehicle).
The reaction torque of the hub motor must now be taken by a suspension design that was never intended for such reations.

Hub motors seem to belong to a new generation of vehicle design.
The tsport100 tesla ?

I believe in hub motors but can't see that they will be a drop in for conversions.
However, I am all ears right now...
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iMiEV MY12     105,131km in pure Electric and loving it !

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Hipo AWD project

Post by juk » Mon, 01 Dec 2008, 02:24

tsport100 wrote: You're wrong about the gearing ok. I said ACP (which includes cars like the Tesla) have 8.25:1 final drive. You're average car has a 3.5:1 final drive diff ratio with a top gear of 1:1. The only time an ICE even gets close to having the same kind of torque as an EV at the wheels is in 1st gear, usually around 3:1. An EV has that torque ALL THE TIME, it's like taking off in 1st gear from 100kph.


This is demonstrated by Jay Leno in the Tesla:
http://www.jaylenosgarage.com/video/vid ... vid=229378

1:40 from the end.

He also drives a 1909 baker electric too.

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Post by juk » Mon, 01 Dec 2008, 02:31

acmotor wrote: Ok, my concern, so to produce a hub motor, it must have the same weight and same moment of inertia as the factory road wheel for a conversion. i.e. same unsprung mass. (particularly in a high performance vehicle).


When Holden, ford, nissan, toyota etc start to use aluminium suspension components like audi, peugeot, porsche etc then we can start to worry about unsprung weight. Until they get serious, i'm happy to bring on the hub motors. I love my alloy suspension and high Mg wheels.

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Post by tsport100 » Mon, 01 Dec 2008, 02:57

Gotta love those turbos.

I'm fairly familiar with flat torque curves as my daily driver for the last 6 years has 495 Nm peak with probably 85-90% of that as low as 1500rpm. It just doesn't even notice hills. With a 3.08 diff in top gear it's theorectially 1525 Nm at the wheels, closer to 1000 Nm if you subtract 30% losses. While that's good enough for me, when a little 240hp EV can have 1815 Nm at the wheels at any speed and cost 1/20th per km to run compared to my car I'm sold.

I used to "Do" Dato, must've owned 7x 1600s, built a Group G rally Dato with the motor 4" back in the chassis. The last Dato I owned was a Bluebird wagon that I put an FJ20T into, fun while it lasted. Owned a mildly truned up Lancer GSR for while too.

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Post by Electrocycle » Mon, 01 Dec 2008, 03:19

sounds like fun :)

I agree that the EV can make these sorts of power and performance figures, but at the moment it's still very expensive to do so.
Even if a battery pack has the watt hours to run at full power for a reasonable length of time, actually delivering the kilowatts on a constant basis is still a challenge!

I'm definitely interested in the performance electric side of things, but what will make it affordable is first getting the mass market friendly midrange cars at a point where they're a viable alternative for enough people (in a lot of cases they already are, but people are not yet willing to make the perceived compromises).
It's all about the critical mass!
When Holden, ford, nissan, toyota etc start to use aluminium suspension components like audi, peugeot, porsche etc
They do in a lot of cases, but often the steel parts are not much heavier, and have a lot of benefits (cheap pressed sheet construction, bending rather than breaking in a crash, less metal fatigue issues, etc)
The heaviest part is usually the brake disc, which could be reduced a bit with assumed regen braking most of the time - while still maintaining purely frictional emergency braking.

A friend of mine has been designing hub motors, and while they are theoretically the ideal option, there are quite a few challenges to getting high efficiency over a wide enough speed range and achieving the necessary power to weight ratio.
The Engine Whisperer - fixer of things

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