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I try to look at this problem from a different perspective, to say that unsprung weight is a big issue with low downforce. What do you think?

If we can make the wheels have enough downforce so that the "sprung" (so-called) to unsprung weight ratio is kept, then it wouldn't be a problem anymore?
"Downforce" normally refers to aerodynamic force, and wheels don't have aerodynamic downforce, so I'll assume that you mean to make the car have enough aerodynamic downforce carried through the suspension that the high unsprung mass is tolerable because it is low compared to the suspension load.

That ignores all of the dynamics related to the car's mass, but still think it's valid to some extent; however, in practice road cars don't have any downforce and even race cars with extreme ground effects or big wings only have substantial downforce at high speed, so it's not useful to a functional road car or a really effective solution even in a race car.
 

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Bear in mind that if you're planning to attach a motor to a suspension that Elaphe hasn't worked with before, the engineering costs are likely to dwarf the parts costs.
Elaphe's in-wheel motor page gives only the barest minimum of information. Is there anything more available, such as drawings showing how the unit is mounted?
Lacking a response to this I did a bit of searching, and found this article about a larger Elaphe unit:
Elaphe begins production of new in-wheel hub motor

This unit appears to be designed to mount to the hub carrier (or upright) with four bolts in the same way that a typical hub-bearing unit mounts, which makes a lot of sense. One variation in this case is the brake caliper, which is typically bolted to the upright, is bolted to the hub-bearing unit instead; presumably this is due to the need to use smaller brake components (rotor and caliper to fit inside the convoluted structure of the motor and supporting frame. The key would be to use a suspension which uses a hub-bearing unit compatible with the one for which Elaphe designed their structure.

I'm really curious what the back side of the M700 to be used for this project will look like, and what will be adapted or built to work with it.
 

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"Downforce" normally refers to aerodynamic force, and wheels don't have aerodynamic downforce, so I'll assume that you mean to make the car have enough aerodynamic downforce carried through the suspension that the high unsprung mass is tolerable because it is low compared to the suspension load.

That ignores all of the dynamics related to the car's mass, but still think it's valid to some extent; however, in practice road cars don't have any downforce and even race cars with extreme ground effects or big wings only have substantial downforce at high speed, so it's not useful to a functional road car or a really effective solution even in a race car.
"That ignores all of the dynamics related to the car's mass,"

If possible, could you explain what you mean by this?

On a separate note, you have made a fair point, that even race cars do not give enough downforce to make an in-wheel motor relevant. I agree with this, and that is why I am finding what other benefits in-wheel motors can give other than just "interior space savings". still in progress!
 

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hi, can you say anything about the costs of the Elphane hubs?
Bear in mind that Elaphe hasn't yet gone into anything resembling mass production. They've taken an interest in my project. I suspect my little one-man company is the smallest they've ever been willing to deal with.

There are engineering costs on both sides. On their side you can figure Elaphe's total BOM and engineering costs at about what you'd pay Steve Wynn for an electric Delorean,
namely at the low end of six figures.

A ball-park division of what Elaphe would charge you for their contribution would be 70% for engineering and 30% for the BOM--two motors, two Elaphe-engineered uprights (to integrate with the Delorean suspension), two inverters (two because the 3-phase AC motors don't stay in phase when going round a corner), power distribution unit (PDU: contactors, resistors, fuses), power control unit (PCU, Elaphe's "brain") and other miscellany.

On my outfit's side I get to source the battery (Chevy Volt), BMS, OBC, and DC/DC (400V to 12V) and put the car back together. (It took me a month to take it apart, mainly alone except for removing the engine with the help of two friends.)

Over a year ago (February) two Elaphe engineers came by and spent four days hooking up the battery to a jury-rigged PDU (cannibalized from the Volt battery) to the inverters to the motors, jacked up the rear end, and spun the wheels at various speeds, establishing that that much at least was working properly. This left them with a spare fifth day that they spent touring San Francisco before flying back to Slovenia.
122639

After that it was my turn to source the components that their PCU would talk to on the CAN bus. However I'd torn my rotator cuff (subscapularis tendon completely detached from the humerus), and what with that and the pandemic I've put the whole project on hold, just getting back to it now as my shoulder recovers and people get vaccinated.

At some point I'll give more details about the engineering, here and/or on 7leaguewheels.com when that site becomes more real. For the moment I'll just address four points raised earlier in this thread, and also ask for sourcing suggestions for still-needed parts.

1. "The dual M700 setup will be like driving a DeLorean in second gear all of the time." The M700 motor makes one revolution every 28 cycles of the AC and is designed to max out at 700 Hz, which corresponds to 700/28*60 = 1500 rpm. At say 850 revolutions per mile that comes to 1500/850*60 = 106 mph, faster with larger wheels. And no gearing (of any kind, neither step-down nor diff) means that much less friction and gear noise.

2. "an in-wheel motor requires the power cables go to the wheels, flexing with every suspension movement." The three cables from the motor are strapped to the trailing arm and enter the frame at the arm's pivot point. The cables therefore don't flex but twist, by a few degrees along the part of the cable at right angles to the arm (just above the right rear wheel in the photo). The twist is distributed along about a foot of cabling before it turns to reach its inverter.

3. "Without reduction gearing between the motor and the wheels, the motor needs to be very large to produce enough torque to the wheels, making the unsprung mass problem worse." Following Brian's suggestion to add up the weights of what's removed and what's added, I weighed everything during (dis)assembly and calculated the net increase in unsprung weight at about 30% for this configuration. Lighter wheels, lighter uprights, and no half-axles helped. People have way more experience with duallys than with in-wheel motors so I imagine they'd be the ones to ask. How often do people with duallys complain about their unsprung weight?
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4. The drum brake "seems unlikely to have sufficient capacity for a DeLorean." The Delorean's rear disc pads are smaller than its front pads, which remain unchanged. I'm not expecting a big change replacing small disc pads by small drum pads at the rear, but we'll see.

Regarding sourcing advice, I have a 2014 Kia Soul onboard charger but no clue as to its CAN commands, so I'm looking for suggestions for a suitable OBC with known CAN commands. Ditto for 4 BMS's for the 4 Chevy Volt modules (Gen1). And ditto for a suitable DC/DC 400-12V converter, preferably water-cooled. Is there a one-stop shop that could supply all three (for easier integration)? (I'm in North America.)

More details later.
 

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Thanks a lot for the very detailed explanation. I had such figures in mind. This is unfortunately out of my budget. But thanks again. Cheers and greetings from Austria.

Bear in mind that Elaphe hasn't yet gone into anything resembling mass production. They've taken an interest in my project. I suspect my little one-man company is the smallest they've ever been willing to deal with.

There are engineering costs on both sides. On their side you can figure Elaphe's total BOM and engineering costs at about what you'd pay Steve Wynn for an electric Delorean,
namely at the low end of six figures.

A ball-park division of what Elaphe would charge you for their contribution would be 70% for engineering and 30% for the BOM--two motors, two Elaphe-engineered uprights (to integrate with the Delorean suspension), two inverters (two because the 3-phase AC motors don't stay in phase when going round a corner), power distribution unit (PDU: contactors, resistors, fuses), power control unit (PCU, Elaphe's "brain") and other miscellany.

On my outfit's side I get to source the battery (Chevy Volt), BMS, OBC, and DC/DC (400V to 12V) and put the car back together. (It took me a month to take it apart, mainly alone except for removing the engine with the help of two friends.)

Over a year ago (February) two Elaphe engineers came by and spent four days hooking up the battery to a jury-rigged PDU (cannibalized from the Volt battery) to the inverters to the motors, jacked up the rear end, and spun the wheels at various speeds, establishing that that much at least was working properly. This left them with a spare fifth day that they spent touring San Francisco before flying back to Slovenia.
View attachment 122639
After that it was my turn to source the components that their PCU would talk to on the CAN bus. However I'd torn my rotator cuff (subscapularis tendon completely detached from the humerus), and what with that and the pandemic I've put the whole project on hold, just getting back to it now as my shoulder recovers and people get vaccinated.

At some point I'll give more details about the engineering, here and/or on 7leaguewheels.com when that site becomes more real. For the moment I'll just address four points raised earlier in this thread, and also ask for sourcing suggestions for still-needed parts.

1. "The dual M700 setup will be like driving a DeLorean in second gear all of the time." The M700 motor makes one revolution every 28 cycles of the AC and is designed to max out at 700 Hz, which corresponds to 700/28*60 = 1500 rpm. At say 850 revolutions per mile that comes to 1500/850*60 = 106 mph, faster with larger wheels. And no gearing (of any kind, neither step-down nor diff) means that much less friction and gear noise.

2. "an in-wheel motor requires the power cables go to the wheels, flexing with every suspension movement." The three cables from the motor are strapped to the trailing arm and enter the frame at the arm's pivot point. The cables therefore don't flex but twist, by a few degrees along the part of the cable at right angles to the arm (just above the right rear wheel in the photo). The twist is distributed along about a foot of cabling before it turns to reach its inverter.

3. "Without reduction gearing between the motor and the wheels, the motor needs to be very large to produce enough torque to the wheels, making the unsprung mass problem worse." Following Brian's suggestion to add up the weights of what's removed and what's added, I weighed everything during (dis)assembly and calculated the net increase in unsprung weight at about 30% for this configuration. Lighter wheels, lighter uprights, and no half-axles helped. People have way more experience with duallys than with in-wheel motors so I imagine they'd be the ones to ask. How often do people with duallys complain about their unsprung weight? View attachment 122638

4. The drum brake "seems unlikely to have sufficient capacity for a DeLorean." The Delorean's rear disc pads are smaller than its front pads, which remain unchanged. I'm not expecting a big change replacing small disc pads by small drum pads at the rear, but we'll see.

Regarding sourcing advice, I have a 2014 Kia Soul onboard charger but no clue as to its CAN commands, so I'm looking for suggestions for a suitable OBC with known CAN commands. Ditto for 4 BMS's for the 4 Chevy Volt modules (Gen1). And ditto for a suitable DC/DC 400-12V converter, preferably water-cooled. Is there a one-stop shop that could supply all three (for easier integration)? (I'm in North America.)

More details later.
 

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How often do people with duallys complain about their unsprung weight?
All of the time. If you have ever drive a heavy duty truck you know unsprung weight causes all sorts of weird behavior especially around corners over a bumpy section. Definitely something that you should aim to limit as much as possible on a sports car.
 

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1. "The dual M700 setup will be like driving a DeLorean in second gear all of the time." The M700 motor makes one revolution every 28 cycles of the AC and is designed to max out at 700 Hz, which corresponds to 700/28*60 = 1500 rpm. At say 850 revolutions per mile that comes to 1500/850*60 = 106 mph, faster with larger wheels. And no gearing (of any kind, neither step-down nor diff) means that much less friction and gear noise.
My comment about second gear was about the torque available to the wheels; perhaps that wasn't clear. The above is interesting, but completely unrelated to the subject of torque. At high speed, the M700 motors won't produce their peak torque, of course.

How much gear noise do you hear in a typical EV? I don't think it's a problem, but some might. There is no loss due to gearing inefficiency, but motor efficiency is more important... and unknown.
 

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2. "an in-wheel motor requires the power cables go to the wheels, flexing with every suspension movement." The three cables from the motor are strapped to the trailing arm and enter the frame at the arm's pivot point. The cables therefore don't flex but twist, by a few degrees along the part of the cable at right angles to the arm (just above the right rear wheel in the photo). The twist is distributed along about a foot of cabling before it turns to reach its inverter.
It's good to hear that the cables are routed appropriately, and that you understand that they are flexing with every suspension movement.
 

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3. "Without reduction gearing between the motor and the wheels, the motor needs to be very large to produce enough torque to the wheels, making the unsprung mass problem worse." Following Brian's suggestion to add up the weights of what's removed and what's added, I weighed everything during (dis)assembly and calculated the net increase in unsprung weight at about 30% for this configuration. Lighter wheels, lighter uprights, and no half-axles helped. People have way more experience with duallys than with in-wheel motors so I imagine they'd be the ones to ask. How often do people with duallys complain about their unsprung weight?
Thanks for the information. Replacing old wheels and heavy antiquated uprights with modern materials does help. ;)

Part of the weight savings comes from using a lighter brake assembly, a change which could be made in any EV conversion, although there are limits to that (in-wheel or not).

Was that total including the axle shafts? Those shafts were only roughly half unsprung mass, because they are supported and located at the inboard end which does not move with the suspension.

What are the actual numbers? A 30% increase from what?
 

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The dually Buick is hilarious - it's even front wheel drive! 😂

An excellent demonstration that just because something can be done, and someone has done it, does not mean that it is a good idea.
 

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4. The drum brake "seems unlikely to have sufficient capacity for a DeLorean." The Delorean's rear disc pads are smaller than its front pads, which remain unchanged. I'm not expecting a big change replacing small disc pads by small drum pads at the rear, but we'll see.
The pad size is a small part of the effectiveness of a brake. What are the diameter and width of the Elaphe drums?
 

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I glad to see that the project has made progress, and is only temporarily paused. Many projects never make it past the initial planning and some acquisition of parts. The Volt battery fits nicely in the rear frame section.
 

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Very interested in this project as I'm also looking into the idea of a couple of Elaphe M700s in an EV project.

There will always be those who dismiss the idea of hub motors due to the unsprung weight and apparent low power, but the former is not necessarily a problem and subjective performance of the car is really related to the motor's torque production rather than the calculated figure we call 'power'. I always compare the torque available from a potential motor with that of the original ICE. If the electric motor(s) make more than the ICE did in first gear, then the car will perform very well. Even if it falls between 1st and 2nd from the ICE, that will still be quicker overall than the ICE.

Unsprung weight is always the stick with which to beat up anyone who considers in-wheel motors, but unless you're on the racetrack trying to shave fractions of a second off the lap times, is it really that much of a deal. Apparently Colin Chapman (i.e. Lotus) did not believe so, as long as suspension was set up appropriately. I am not concerned about this.

The big advantage of in-wheel motors is allowing all the space previously taken up by the ICE to instead be used for batteries as in smaller cars, this can otherwise be problematic.

What does concern me is the requirement for liquid cooling. I know the power cables can be routed appropriately, but having to pass coolant out the wheels also may just be a set too far.

I'd be very interested to know how vauron plans to deal with this.
 

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... subjective performance of the car is really related to the motor's torque production rather than the calculated figure we call 'power'.
That's valid if you are comparing torque at the wheels and if the same overall diameter of tires are used, and of course torque at the wheels multiplied by wheel speed is power... so you're really comparing power available at a specific speed.

I always compare the torque available from a potential motor with that of the original ICE. If the electric motor(s) make more than the ICE did in first gear, then the car will perform very well.
I agree - for the speed range of first gear.

Even if it falls between 1st and 2nd from the ICE, that will still be quicker overall than the ICE.
Again, I agree, for less than highway speeds.

Unsprung weight is always the stick with which to beat up anyone who considers in-wheel motors, but unless you're on the racetrack trying to shave fractions of a second off the lap times, is it really that much of a deal. Apparently Colin Chapman (i.e. Lotus) did not believe so, as long as suspension was set up appropriately.
What makes you think that? Chapman didn't use particularly heavy unsprung weight, and in fact used light wheels, alloy hub carriers, and low unsprung weight suspension designs.
 

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That's valid if you are comparing torque at the wheels and if the same overall diameter of tires are used, and of course torque at the wheels multiplied by wheel speed is power... so you're really comparing power available at a specific speed.
Same car, same wheels, same tyres so perfectly comparable. Otherwise, not hard to compute a suitable correction factor.

I agree - for the speed range of first gear.


Again, I agree, for less than highway speeds.
Why do you say that? Torque output from an electric motor is pretty flat. So at e.g. 50 mph, the electric motor will be outputting (putting out?) way more torque to the wheels compared to the ICE which in top gear has lost the multiplication advantages of the gearbox (let's assume top is 1:1) and hence much less torque available at the rear wheels.

I still think you're getting hung up on power figures when they're irrelevant. Power is (as I'm sure you know) torque multiplied by speed and not something humans can ever physically experience as it is a purely calculated figure. What we actually experience is the thrust of the car as it accelerates and that is the torque. Power only determines the top speed. Torque is how fast we get there.

What makes you think that? Chapman didn't use particularly heavy unsprung weight, and in fact used light wheels, alloy hub carriers, and low unsprung weight suspension designs.
'cos he said so. At least that is what I have read. Particularly apposite when he has the reputation of always going for lightweight so if a man of his reputation can dismiss it, then it would suggest it's not that important - for road use.

My experience with hub mounted motors is purely theoretical at this point, but I have ridden many shaft drive motorcycles which carry the weight of a small electric motor in their rear wheels. If I was putting together a race bike or outright sports road bike, I would not use shaft drive as the weight penalty is relatively enormous. However, I have motorcycles with (lightweight) chain drives and heavy shaft drives and if I'm honest, on the road I cannot tell any difference from this increase in unsprung weight. Overall weight of the bike is far more noticeable when slinging it through tight turns (e.g. Alpine passes) than any supposed difference due to the weight of the rear shaft.

As far as I'm concerned, increased unsprung weight is a non-issue. The biggest problem is achieving sufficient torque without a gearbox, but for my purposes, a couple of M700s would do very nicely.

I'd certainly like to hear from the OP about his plans for coolant to the wheels.
 

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Torque output from an electric motor is pretty flat.
Only in the low-speed range in which current is constant. Above that (about one-third of the way up the speed range in a typical EV application) the available torque goes down as speed goes up.
 

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'cos he said so. At least that is what I have read.
Okay... but where? Rumours are not useful, and stories of vehicle development from decades ago are mostly rumour. Is there a published quote of some sort, or are we talking about another automotive fairy tale?
 

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I still think you're getting hung up on power figures when they're irrelevant. Power is (as I'm sure you know) torque multiplied by speed and not something humans can ever physically experience as it is a purely calculated figure. What we actually experience is the thrust of the car as it accelerates and that is the torque. Power only determines the top speed. Torque is how fast we get there.
Back to basics:
kinetic energy is the product of velocity squared and mass. The time taken to get to accelerate from one velocity to another is then the kinetic energy change divided by the average power applied (beyond the power required to overcome drag). Power is everything to acceleration.

I agree that what the "seat of the pants" detects is force, which implies acceleration, not velocity or energy; however, energy is real, not just "a purely calculated figure".

Here's an experiment: take a AA battery out a flashlight or toy, connect it to any motor you want, use an insane gearbox to produce more torque than a locomotive... and try to get your car (or even a bike) up to any speed, which should be no problem because "Power only determines the top speed. Torque is how fast we get there". Have fun.
 

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Back to basics:
kinetic energy is the product of velocity squared and mass. The time taken to get to accelerate from one velocity to another is then the kinetic energy change divided by the average power applied (beyond the power required to overcome drag). Power is everything to acceleration.

I agree that what the "seat of the pants" detects is force, which implies acceleration, not velocity or energy; however, energy is real, not just "a purely calculated figure".

Here's an experiment: take a AA battery out a flashlight or toy, connect it to any motor you want, use an insane gearbox to produce more torque than a locomotive... and try to get your car (or even a bike) up to any speed, which should be no problem because "Power only determines the top speed. Torque is how fast we get there". Have fun.
I don't think we're going anywhere with this, but I will finish by pointing out that we cannot detect velocity. Only change in velocity, which is acceleration and that is down to torque, not power.

Besides which, this 'discussion' is really about the efficacy of in-wheel motors compared to driving through some form of gearbox/shaft system and all your criticisms are equally applicable to both which rather suggests you are arguing against EVs in general.

I have no idea where I read the Lotus/Chapman comment. At the time I had no idea anyone would be demanding to know where I read it. So in future I'll be sure to make copious notes of everything I read, just in case anyone accuses me of 'making it up'. On second thoughts, I won't bother. You want to find it, go look it up yourself.
 
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