# Yet another Delorean conversion



## brian_ (Feb 7, 2017)

vauron said:


> 4. A shipment of two in-wheel motors, inverters, and "powerbrain" arrived yesterday shortly from Elaphe Propulsion, still awaiting customs to clear it.


In-wheel motors have never been successful in normal road-going cars, for a few reasons. You're going to see lots of scepticism in this discussion as a result.

The mass of the wheel and everything that moves with it during suspension travel - called "unsprung weight" - is important to suspension performance and resulting ride and handling. Just putting the mass of the car's motor(s) and distributing it to two or all four of the wheels is a problem for suspension performance. 

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. An in-wheel motor with reduction gearing adds substantial weight and complexity. Whether it is a large motor without gearing, or a smaller motor with gearing, this is a problem.

People promoting in-wheel motors often point to the benefit of not needing a jointed axle shaft from inboard-mounted drivetrain to the wheels, but an in-wheel motor requires the power cables go to the wheels, flexing with every suspension movement (and turn, if on a steered axle). In addition, a motor of significant power density (like every production EV motor) also needs liquid coolant hoses.

I assume that the proposed motors are the Elaphe M700. They weigh 23 kg each (including the hub), and require liquid cooling. They also have bearings from a Smart, and apparently the brake from a Smart which is appears to be a drum; this seems unlikely to have sufficient capacity for a DeLorean.


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## brian_ (Feb 7, 2017)

vauron said:


> Continuous power per motor is 50 kW, peak is 75 kW which adds up to 200 HP. This is an improvement over the 140 HP I was getting from the Peugeot-Renault-Volvo V6 engine.


Elaphe says that the peak torque output of the M700 is 700 Nm, so two of them will put 1400 N⋅m to the wheels in total. For comparison, the DeLorean's engine has a peak torque output of 153 lb⋅ft (207 N⋅m) @ 2750 rpm (according to some sources).

207 x 3.36 1st gear x 3.44 final = 2,392 N⋅m to wheels up to 17 mph or 27 km/h
207 x 2.06 2nd gear x 3.44 final = 1,467 N⋅m to wheels at 27 mph or 43 km/h
207 x 1.38 3rd gear x 3.44 final = 983 N⋅m to wheels at 41 mph or 67 km/h
207 x 1.06 4th gear x 3.44 final = 755 N⋅m to wheels at 53 mph or 86 km/h
207 x 0.82 5th gear x 3.44 final = 584 N⋅m to wheels at 68 mph or 110 km/h
The DeLorean engine put out 162 lb⋅ft (220 N⋅m) @ 2750 according to Road&Track's 1982 test, which would mean more torque to the wheels at the same speeds.

The dual M700 setup will be like driving a DeLorean in second gear all of the time, so the start of acceleration driving slowly over bumps may not be acceptable. That's roughly what Duncan was saying in the other thread.

The stock DeLorean can use first gear all the way to 40 mph. Of course torque drops off after 2750 rpm, but it's still going to be out-accelerating the dual M700 setup in the same weight of car.

Is a full set of specs available for any of the Elaphe products? Given just the peak torque, peak power, and continuous power, this is a guessing game. If the peak torque can be maintained continuously within the power limits, then the 50 kW power limit will be reached at 690 rpm, and then torque will drop in proportion to speed. A Delorean's 235/60R15 rear tires turn 794 revolutions per mile, so 690 rpm is 0.87 miles per minute, or 52 mph or 84 km/h; acceleration will start dropping off more rapidly from that point.

The idea of a fixed drive ratio from electric motor to wheels is normal - essentially all production EVs have a fixed-ratio transmission, so their change in behaviour with speed is similar. But for comparison, an original Nissan Leaf (low-performance by today's standards) has a motor putting out 320 N⋅m, multiplied by a 7.94:1 transaxle, putting 2541 N⋅m to the wheels. It can only put out 80 kW, but it reaches that at a much lower speed than the M700 setup driving 235/60R15 tires.


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## vauron (Sep 25, 2016)

brian_ said:


> In-wheel motors have never been successful in normal road-going cars, for a few reasons. You're going to see lots of scepticism in this discussion as a result.
> 
> The mass of the wheel and everything that moves with it during suspension travel - called "unsprung weight" - is important to suspension performance and resulting ride and handling...
> ...
> ...


Ok, so the main concern is not with the battery then.

Yes, the M700. The Delorean's front brakes will remain disc, we'll see whether drums in the rear make a big difference to the Delorean's stopping ability. I never found the Delorean's e-brake terribly effective, we'll see if that's any different with drums.

With the original engine the Delorean's curb weight is 1244 kg, call it 1400 kg with two passengers. I expect the weight to be roughly the same without the engine, transaxle, and gas tank, but to be on the safe side round it up to 1500 kg.

An 8% grade at 120 kph (75 mph) raises the car with a vertical velocity of 8/3 m/s. If I can remember enough 10th grade physics, that should add 1500*9.8*8/3 = 39.2 kW to whatever drag and rolling resistance requires at that speed, hopefully less than 30 kW.

Since Elaphe specs the two motors at 100 kW continuous, and 150 kW for 10 seconds, I figured that 70 kW would be enough power to feel reasonably confident about hill climbing ability, otherwise I would have used some other motor.

As for unsprung weight, this will be a learning experience for me. If it proves to be unbearable I'll look into active suspension options. (Since the front suspension is unchanged, information about bumps can be measured there and fed to the rear suspension before it hits the bump.)
However this won't be a priority because the purpose of this conversion is to have a test platform to explore renewable (zero-emission) fuel technologies for use as a range extender, e.g. ammonia. At some point I'll start fleshing out details at https://7leaguewheels.com.


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## vauron (Sep 25, 2016)

brian_ said:


> the 50 kW power limit will be reached at 690 rpm


Yes, and the 75 kW power limit will be reached at 1035 rpm, which using your arithmetic is 78 mph.

So acceleration will still be constant at 60 mph = 26.8 m/s. If the curb weight is 1244 kg, an 80 kg driver brings that to 1324 kg. I measure the rear wheel's radius at 0.30 m (you were working with 0.32 m), which converts 1400 Nm to 1400/.30 = 4666 N, hence an acceleration of 4666/1324 = 3.52 m/s2. So to reach 60 mph = 26.8 m/s should take 26.8/3.52 = 7.6 seconds, well within the time allowed to use the motor's max power 75 kw.

Road & Track measured the Delorean's 0-60 mph time at 10.5 seconds. If my math is correct the M700 should shave about 3 seconds off that. Nowhere near ludicrous of course, but respectable.


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## vauron (Sep 25, 2016)

brian_ said:


> The dual M700 setup will be like driving a DeLorean in second gear all of the time.


I seriously doubt that the acceleration of the Delorean in second gear at below 5 mph is remotely near 3.52 m/s2, which is what I'm expecting from the M700. The PRV V6 is wonderful but not that wonderful.

As long as you can keep the M700's magnet below 65 °C and the windings below 180 °C it has a torque constant of 2.12 Nm/A. Maximum phase current is 350 A; as long as this current is sustained you should get a torque of 350*2.12 = 742 Nm as soon as you hit the accelerator. (This is actually a tad over their quoted max torque of 700 Nm, I'm guessing they rounded down to be conservative but I can check.)


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## brian_ (Feb 7, 2017)

vauron said:


> I measure the rear wheel's radius at 0.30 m (you were working with 0.32 m), which converts 1400 Nm to 1400/.30 = 4666 N, hence an acceleration of 4666/1324 = 3.52 m/s2. So to reach 60 mph = 26.8 m/s should take 26.8/3.52 = 7.6 seconds, well within the time allowed to use the motor's max power 75 kw.
> 
> Road & Track measured the Delorean's 0-60 mph time at 10.5 seconds. If my math is correct the M700 should shave about 3 seconds off that. Nowhere near ludicrous of course, but respectable.


I didn't work with a radius at all; I used the specifications for a P235/60R15 tire. Unfortunately I copied the revolutions per mile incorrectly, presumably picking off the number for the wrong size - it should be in the range of 715 to 745 revolutions per mile, depending on tire brand and model. The same specifications show an overall diameter of 28", which would be 71.12 cm, for a radius of 35.56 cm, but the loaded radius is less. A radius of 30 cm would be a flat tire of that size, but okay...

The logic of acceleration calculation is fine, except that it ignores all rolling and aerodynamic drag; that's a substantial difference. If you make the same assumption with the output of the gas engine (which is much more difficult because it varies with speed), you'll get an acceleration time much quicker than reality, too.

During that acceleration with a constant 700 Nm the motor's output power isn't 75 kW; it is zero at zero speed and increases linearly with speed. Using the undersized 0.3 m radius, the tire turns 854 times per mile, so 854 revolutions per minute at 60 mph (a mile per minute). 700 Nm times 854 rpm is still only 62 kW, so the motor's burst power limit is not a concern.


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## brian_ (Feb 7, 2017)

vauron said:


> With the original engine the Delorean's curb weight is 1244 kg, call it 1400 kg with two passengers. I expect the weight to be roughly the same without the engine, transaxle, and gas tank, but to be on the safe side round it up to 1500 kg.


My suggestion would be to add up the weight of all of the parts to be removed, and all of the stuff to be added, to get a realistic estimate. EV conversions only end up lighter than the original car if they are very short-range (small battery), or if the original engine and transmission were abnormally heavy.


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## vauron (Sep 25, 2016)

brian_ said:


> I didn't work with a radius at all; I used the specifications for a P235/60R15 tire. Unfortunately I copied the revolutions per mile incorrectly, presumably picking off the number for the wrong size - it should be in the range of 715 to 745 revolutions per mile, depending on tire brand and model. The same specifications show an overall diameter of 28", which would be 71.12 cm, for a radius of 35.56 cm, but the loaded radius is less. A radius of 30 cm would be a flat tire of that size, but okay...
> 
> The logic of acceleration calculation is fine, except that it ignores all rolling and aerodynamic drag; that's a substantial difference. If you make the same assumption with the output of the gas engine (which is much more difficult because it varies with speed), you'll get an acceleration time much quicker than reality, too.
> 
> During that acceleration with a constant 700 Nm the motor's output power isn't 75 kW; it is zero at zero speed and increases linearly with speed. Using the undersized 0.3 m radius, the tire turns 854 times per mile, so 854 revolutions per minute at 60 mph (a mile per minute). 700 Nm times 854 rpm is still only 62 kW, so the motor's burst power limit is not a concern.


Good, it looks like we're basically on the same page. I was wrong to ignore rolling resistance and drag for 0-60 mph quickness, it will be interesting to see what the real quickness is. Hopefully I'll know this in December.

No need to point out that power is low at low rpm for both electric motors and ICEs, obvious for both from elementary physics. The huge difference is that, like power, torque is also low at low rpm for ICEs, but not for electric motors, which is why a Delorean in 2nd gear is the wrong comparison. The acceleration figure I gave for two M700s on the Delorean should be correct at low speed and gradually decrease at higher speeds because of drag and rolling resistance as you say.

The rear wheels are currently off the car, and their circumference is 2.13 m, making their unloaded radius 34 cm. I believe I'd correctly inflated them back when they were supporting the whole car, will recheck when it's back together.


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## vauron (Sep 25, 2016)

brian_ said:


> My suggestion would be to add up the weight of all of the parts to be removed, and all of the stuff to be added, to get a realistic estimate. EV conversions only end up lighter than the original car if they are very short-range (small battery), or if the original engine and transmission were abnormally heavy.


At some point I'll try to estimate the weight of the Delorean's engine, transaxle, and half-axles.

Don't most conversions only remove the engine and not the clutch or transaxle/transmission and half-axles? I've removed the lot. And I'm not aiming for long range using just the Volt's battery, which is somewhere around 400 lbs, a lot lighter than the batteries in Teslas, Bolts, etc. I'll be happy if I get 60 miles of range before I get around to the range extender.


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## MoonUnit (Jun 29, 2019)

4. A shipment of two in-wheel motors said:


> I didn't realise one could buy Elaphe motors, I thought they were only available to OEMS. Can I ask how you were able to purchase them?


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## vauron (Sep 25, 2016)

MoonUnit said:


> I didn't realise one could buy Elaphe motors, I thought they were only available to OEMS. Can I ask how you were able to purchase them?



It's for a research project they're interested in. https://7leaguewheels.com will have more details in due course.


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## rmay635703 (Oct 23, 2008)

How much does the hub motor set you back?

I was looking at an s400 to drive a rear wheel on a micro car and will watch your progress carefully


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## EVmattyP (May 12, 2019)

rmay635703 said:


> How much does the hub motor set you back?
> 
> I was looking at an s400 to drive a rear wheel on a micro car and will watch your progress carefully


same... I did the math on the S400 and it looks like top speed with my wheels would only be 50mph but that may be fine for you. 

I've also reached out to them, re-purposing my business to something that may allow me to get a quote.


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## vauron (Sep 25, 2016)

EVmattyP said:


> same... I did the math on the S400 and it looks like top speed with my wheels would only be 50mph but that may be fine for you.
> 
> I've also reached out to them, re-purposing my business to something that may allow me to get a quote.


Seems like DIYelectricCar is quite divided about in-wheel motors. Duncan and Brian were pretty pessimistic. I'd be interested to know who's tried them and been disappointed. Me, I like to balance theory and practice, and this is a big experiment for me. For all I know I'll have proved Duncan and Brian right.

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. When it comes to your budget, think Roadsters, not volume-production Model 3's. Stephen Wynne's Delorean operation in Texas would hit you up for over $100K if ever the NHTSA lets them go forward with their idea of selling electric Deloreans, even though Congress is fine with the concept and gave it the green light years ago. And those would still be using the Delorean's clutch and transaxle with just one motor, not the fancier pair of M700's with no transaxle.


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## brian_ (Feb 7, 2017)

vauron said:


> Seems like DIYelectricCar is quite divided about in-wheel motors. Duncan and Brian were pretty pessimistic. I'd be interested to know who's tried them and been disappointed. Me, I like to balance theory and practice, and this is a big experiment for me.


I would be interested in just seeing someone try them with a normal road car (not a microcar or low-speed vehicle, or a heavy truck or bus) and complete the project to a running state. Then, it would be interesting to see an objective suspension performance comparison, but I really don't expect to ever see that.

I am looking forward to seeing this DeLorean reach completion (at least to the battery-electric stage) - it should be interesting.


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## brian_ (Feb 7, 2017)

vauron said:


> 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?


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## ishiwgao (May 5, 2011)

vauron said:


> Seems like DIYelectricCar is quite divided about in-wheel motors. Duncan and Brian were pretty pessimistic. I'd be interested to know who's tried them and been disappointed. Me, I like to balance theory and practice, and this is a big experiment for me. For all I know I'll have proved Duncan and Brian right.


I, for one, am actually very interested in In Wheel motors, and not just the low-powered ones for low speed vehicles. I have been looking at high powered in-wheel motors and seeing how to fit super high powered motors (200-300kW) into normal wheels to use in sports car applications. 

It's been about 3 years since i started, and still no concrete method yet. But I'm not giving up soon.


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## brian_ (Feb 7, 2017)

ishiwgao said:


> I have been looking at high powered in-wheel motors and seeing how to fit super high powered motors (200-300kW) into normal wheels to use in sports car applications.


By "fit in", I hope you mean "make light enough" more than just "find space for". The only space problem is getting the motor (possibly with reduction gearing) and the brake both in. Excessive unsprung mass is a bigger issue, especially in a sports car.


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## ishiwgao (May 5, 2011)

brian_ said:


> By "fit in", I hope you mean "make light enough" more than just "find space for". The only space problem is getting the motor (possibly with reduction gearing) and the brake both in. Excessive unsprung mass is a bigger issue, especially in a sports car.


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? 

of course, how to implement this is another topic for discussion, but at least now we found a solution to the first problem


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## brian_ (Feb 7, 2017)

ishiwgao said:


> 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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## brian_ (Feb 7, 2017)

vauron said:


> 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.





brian_ said:


> 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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## ishiwgao (May 5, 2011)

brian_ said:


> "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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## Grupie (May 13, 2021)

hi, can you say anything about the costs of the Elphane hubs?


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## vauron (Sep 25, 2016)

Grupie said:


> 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,





NHTSA releases final Low-Volume Manufacturing Rules | DeLorean


The New DMC DeLorean




www.newdelorean.com




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.








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?









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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## Grupie (May 13, 2021)

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.



vauron said:


> 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,
> 
> ...


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## Electric Land Cruiser (Dec 30, 2020)

vauron said:


> 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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## brian_ (Feb 7, 2017)

vauron said:


> 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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## brian_ (Feb 7, 2017)

vauron said:


> 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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## brian_ (Feb 7, 2017)

vauron said:


> 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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## brian_ (Feb 7, 2017)

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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## brian_ (Feb 7, 2017)

vauron said:


> 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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## brian_ (Feb 7, 2017)

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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## eUKenGB (Feb 21, 2019)

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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## brian_ (Feb 7, 2017)

eUKenGB said:


> ... 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.



eUKenGB said:


> 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.



eUKenGB said:


> 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.



eUKenGB said:


> 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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## eUKenGB (Feb 21, 2019)

brian_ said:


> 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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## brian_ (Feb 7, 2017)

eUKenGB said:


> 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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## brian_ (Feb 7, 2017)

eUKenGB said:


> '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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## brian_ (Feb 7, 2017)

eUKenGB said:


> 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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## eUKenGB (Feb 21, 2019)

brian_ said:


> 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".
> ...


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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## Electric Land Cruiser (Dec 30, 2020)

@eUKenGB You are misremembering Colin's quote or something else. And yes, if you drop a name like that as your argument from authority, you better be able to back it up.

"The type of suspension used is not important as long as it fulfills a number of basic requirements. These are *minimum unsprung weight*, minimum change of roll center height, correct camber change, minimum angularity of the driveshafts, and elimination of sliding splines. Another essential is to select the correct spring rate, which in effect means deciding on the softest possible spring, one which will give maximum bump absorption with reasonable wheel travel-that is, without increasing ground clearance from a minimum of 4 in. for the sprung mass of the car. On current (1960) racing cars anti-roll bars are needed to obtain the required handling characteristics, but are not necessarily an essential feature of suspension design."
-Colin Chapman






Colin Chapman: One Man Band of the Racing Circus - LotusElan.net







lotuselan.net





It seems that Mr. Chapman thought unsprung weight important enough to put it first on his list of basic requirements.


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## eUKenGB (Feb 21, 2019)

I am not misremembering anything. I just cannot be bothered with all this doom and gloom to try and remember where I read it and since I am not about to waste the time finding corroboration for the quote, obviously I'm lying. Have it your way. I didn't come here to argue about stuff like this.

I thought in a forum such as this we should be supporting everyone's attempt to convert to electric propulsion. Sadly, as in so many other forums, there are always those who simply want to criticise others without actually adding anything of any value.

Pour all the hate you want on the idea of in-wheel motors, but for some of us, in some circumstances, it makes sense and quite frankly, I couldn't give a toss about what Colin Chapman or anyone else says.

What I would like to discuss is e.g. getting coolant out to the motors and other actually interesting technical details of the OP's project.


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## Electric Land Cruiser (Dec 30, 2020)

Alright sorry, @eUKenGB, I won't interact with you anymore. You brought up CC so obviously you do "give a toss." Unsprung weight is one part, mechanical advantage, vibration, water and debris, etc are all other reasons

Go ahead and build your EV with hub motors, should be an excellent vehicle, right.


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## Electric Land Cruiser (Dec 30, 2020)

@eUKenGB I lied, I will pester you some more. I've done a modicum of searching on the subject and find lots and lots of talk by Colin on unsprung weight. Mostly, that all types of weight should be kept to an absolute minimum, I mean that is his mantra. Secondly, the part you are probably _mis_-remembering, is that there is an important relationship between unsprung weight and suspension springrate, he called it "suspension frequency." Basically unsprung weight isn't the be-all, end-all of suspension, but it is extremely important.


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## eUKenGB (Feb 21, 2019)

Electric Land Cruiser said:


> @eUKenGB I lied, I will pester you some more. I've done a modicum of searching on the subject and find lots and lots of talk by Colin on unsprung weight. Mostly, that all types of weight should be kept to an absolute minimum, I mean that is his mantra. Secondly, the part you are probably _mis_-remembering, is that there is an important relationship between unsprung weight and suspension springrate, he called it "suspension frequency." Basically unsprung weight isn't the be-all, end-all of suspension, but it is extremely important.


I am not averse to continuing a civil discussion, so no problem.

I will clarify one point. The comment I read in relation to unsprung weight was quoted specifically in relation to the use of in-wheel motors and originally emanated from Lotus. I had in mind it was Colin Chapman, but it may have been his son or just Lotus, who may have been involved in development of that project. I realise now that I apparently attributed it to CC himself, but that wasn’t what I was trying to say. My apologies for being unintentionally misleading. The essence though is that while not actually desirable, more unsprung weight can be successfully dealt with by suitable suspension design.

Having said that, I am not convinced any major changes to suspension will be required as in my experience, such subtleties are invariably lost when not attempting to minimise lap times on track. For example, I have a Honda FireBlade based motorcycle and although racers and other owners will wax lyrical about the benefits or otherwise of altering suspension height by even one mm, for my own specific reasons, I dropped the rear of the bike by nearly 2 inches and I am unable to tell the difference on the road. Would I have done that to a track bike? No. But this is a naked road bike and in the use for which I have adapted it, I defy anyone to tell the difference.

I am not necessarily saying that fitting a couple of M700s in the rear wheels will be undetectable in all circumstances, but for its intended usage, I am satisfied they will not prove noticeably detrimental to my car. When considered in conjunction with the advantages that an in-wheel motor offers, in particular for my project the huge increase in available battery space and elimination of gear noise, they become a very attractive proposition.

When I stated I don’t give a toss what CC or anyone else thinks, what I mean is that in my use case, those aforementioned advantages of the in-wheel motor trump any so-called disadvantages for different usage. I have the greatest respect for Lotus and CC’s legacy, but they are not trying to do what I am. Their current electric idea is a £2m hypercar that will I am sure be stupendous and no doubt have wonderfully low unstrung weight, but while the Eviya is interesting, it is irrelevant to me. The only reason I raised the issue of their comment about unsprung weight of in-wheel motors was in response to the negativity I was reading here, targeted specifically at that facet of in-wheel motors. However, no, their opinion on the matter is irrelevant to me on this particular project.

I would still be interested in a more technical discussion about this use of in-wheel motors and let’s not get bogged down in having to justify why this particular course of action has been chosen.


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## Electric Land Cruiser (Dec 30, 2020)

Fair enough. Hub motors are the "popular mechanics" of the EV world. Every person I tell my conversion plans to asks "will you put a motor on each wheel?" To which I always reply no. It's the "it's so simple why isn't everyone doing it?!" of the EV world.

Well there happen to be many reasons why it's not been done. You are right that it frees up lots of space and you could possibly do torque vectoring and yes you probably wouldn't notice the change most of the time. All of these benefits are clear to everyone and still the automotive industry has not pursued them in production vehicles.

I believe the OP of this thread has been trying to get his hands on M700s for several years now without success. Perhaps because what works on paper isn't good enough for real roads.


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## eUKenGB (Feb 21, 2019)

I think you're right and that in-wheel motors are not the panacea many believe. But, they are a great solution in some circumstances for space reasons and also the possibility to convert to 4 wheel drive which although not necessarily simple, is basically impossible any other way. Swings and roundabouts.

I also have another project for which I plan to use a Tesla (or similar) motor, centrally mounted and with traditional drive shafts which better suits that particular case. I guess I could summarise that as 'horses for courses'.

The only important factor is that whoever is attempting the work understands all the potential pitfalls.

Designing an EV from scratch is a different proposition and makes in-wheel motors less attractive, except in specific cases for e.g. specialist utility vehicles as being suggested by some hub motor manufacturers. As to why it is taking so long to obtain the M700s? Have you tried buying ANY new modern tech motor. So many great new motors one can read about, but they are all still in development so in-wheel motor development seems no different in that regard.

In any case, the manufacturers only want to sell to 'large' organisations which is disappointing for those of us wanting to convert an existing vehicle as it leaves very little choice. This I believe is THE big problem facing prospective converters. Tesla motors are most commonly used simply because they are the most readily available, but there will soon be better options availalble - just not to us. 😖


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