# Converting an '82 Corvette to use 4 electric motors



## Jomp135 (Mar 20, 2021)

So, I'm currently going through the design process for a high performance '82 Corvette electric car conversion. I'm looking at using AMR-250 90 single motors from EVWest, and after building a rather nifty calculator for spec analysis, I've figured out that the best way for me to meet my performance goals is to use 4 of them, one to power each wheel. I've looked at in wheel hub, and because of the associated performance issues with unsprung mass and the size of the motors, it's not practical. Because of this, I'm now looking at putting the motors in the axle assemblies: each motor will have a planetary gear reduction on the output, and that will be connected to a halfshaft connecting it to the wheels. It's essentially 2 motors pretending to be a very large differential. My problems are twofold:
First, what is the best way to convert an '82 corvette from having a nondriven front axle to having a driven front axle? I don't need most of the features associated with AWD. The way I see it, I just need an FWD axle that can go in an '82 Corvette, but what would that be? Tell me if I would be better off posting this in another forum, by the way.
Second, would my plan with the motors work?

Thanks!


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## wjbitner (Apr 5, 2010)

Jomp135 said:


> So, I'm currently going through the design process for a high performance '82 Corvette electric car conversion. I'm looking at using AMR-250 90 single motors from EVWest, and after building a rather nifty calculator for spec analysis, I've figured out that the best way for me to meet my performance goals is to use 4 of them, one to power each wheel. I've looked at in wheel hub, and because of the associated performance issues with unsprung mass and the size of the motors, it's not practical. Because of this, I'm now looking at putting the motors in the axle assemblies: each motor will have a planetary gear reduction on the output, and that will be connected to a halfshaft connecting it to the wheels. It's essentially 2 motors pretending to be a very large differential. My problems are twofold:
> First, what is the best way to convert an '82 corvette from having a nondriven front axle to having a driven front axle? I don't need most of the features associated with AWD. The way I see it, I just need an FWD axle that can go in an '82 Corvette, but what would that be? Tell me if I would be better off posting this in another forum, by the way.
> Second, would my plan with the motors work?
> 
> Thanks!


Hi!

That certainly sounds interesting. Can you quantify the performance goals you want? As I think about this, I would be more concerned about the batteries. Specifically, when the throttle is applied assuming 4 controllers, that's a lot of current. To get a battery pack to supply that much current is a very high discharge rate, meaning not a lot of range. What type of range are you looking to achieve? Simiilar to ICE engines, the whole system has to work together, fuel supply, cams, compression ratios, suspension, tires... Some depends on how much of the car you are willing to 
alter. Where can you put all those batteries. Look forward to hearing more about this project.

Bill


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## reiderM (Dec 30, 2020)

Jomp135 said:


> So, I'm currently going through the design process for a high performance '82 Corvette electric car conversion. I'm looking at using AMR-250 90 single motors from EVWest, and after building a rather nifty calculator for spec analysis, I've figured out that the best way for me to meet my performance goals is to use 4 of them, one to power each wheel. I've looked at in wheel hub, and because of the associated performance issues with unsprung mass and the size of the motors, it's not practical. Because of this, I'm now looking at putting the motors in the axle assemblies: each motor will have a planetary gear reduction on the output, and that will be connected to a halfshaft connecting it to the wheels. It's essentially 2 motors pretending to be a very large differential. My problems are twofold:
> First, what is the best way to convert an '82 corvette from having a nondriven front axle to having a driven front axle? I don't need most of the features associated with AWD. The way I see it, I just need an FWD axle that can go in an '82 Corvette, but what would that be? Tell me if I would be better off posting this in another forum, by the way.
> Second, would my plan with the motors work?
> 
> Thanks!


You're better off using 2 tesla drive units, one for the front and one for the rear. All the power you could possibly dream of, while only needing to deal with 2 inverters instead of 4. 

Like Bill said, you would probably have a hard time finding a battery pack that can power 2 powerful inverters, much less 4.

You're correct in that there is not a good reason to use hub motors for just about any project.

What kind of performance are you looking for? 2 large Tesla drive units will produce around 1000hp, which is in truth probably too much for an '82 corvette.


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## Electric Land Cruiser (Dec 30, 2020)

This guy made a 4WD C3 Corvette by using a Caddy Eldorado front end, so maybe the Cadillac FWD axles and hubs would bolt up to the C3 suspension, or close enough to make work: The World’s Only 4WD Hemi-Powered Corvette -

Personally, I think RWD suits the Vette more. EV conversions should be built to the original car's strengths. One great thing about a Vette is the rear transaxle, which means that it's already set up for a rear engine EV conversion!


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## brian_ (Feb 7, 2017)

Jomp135 said:


> ... each motor will have a planetary gear reduction on the output, and that will be connected to a halfshaft connecting it to the wheels. It's essentially 2 motors pretending to be a very large differential.


That's a perfectly workable configuration, used by a few existing EVs (such as the Rimac Concept cars) and used at one axle only (three motors total) by some hybrids and proposed EVs.

But you may want to reconsider the use of planetary reduction. It's hard enough to get a high enough ratio in a single planetary stage, and two planetary stages are complex(and take more axial length) compared to a two-stage set of parallel gears. For instance, GM used single-stage planetary reduction in the Chevrolet Spark EV but it only had about 3.5:1 reduction, then for the Chevrolet Bolt they use parallel gears; both have the axle outputs concentric with the motor shaft.


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## brian_ (Feb 7, 2017)

wjbitner said:


> Can you quantify the performance goals you want? As I think about this, I would be more concerned about the batteries. Specifically, when the throttle is applied assuming 4 controllers, that's a lot of current.


It isn't any more battery current than the same power from one huge motor or two large motors - it's just a question of total power, regardless of how many ways it is split up.

But yes, performance requirements need to be understood to assess battery requirements, regardless of the number of motors.



wjbitner said:


> To get a battery pack to supply that much current is a very high discharge rate, meaning not a lot of range. What type of range are you looking to achieve?


Performance only matters to range if you use that performance. If you are racing, using everything the car can do continuously, obviously range is short.


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## Jomp135 (Mar 20, 2021)

Yes, I guess I should lay out my performance goals. I want to use the AMR motors because of their power curves. I used Desmos to whack together a crude calculator to analyze performance(found here: Curves ) , and I found that this specific layout meets my goals quite nicely, with a little extra bonus. My goals going in were:
180 mph top speed
2.5 second zero to 60
At least 100 mile range.
I was looking at an 80kwh battery bank, but I haven't settled on what batteries to use yet.
However, looking at the power curves I found something which is very nice indeed: namely, acceleration stays pretty much constant throughout the full speed range of the car, at about 10 m/s^2. This is assuming 95% drivetrain efficiency, though, so I'm obviously not expecting those results in the real world. Still, that kind of acceleration means 7.5 second 0-170 times, which is fantastic. I feel that the calculator is definitely flawed in that the power draw at low speeds is really low, giving me ranges that are much too good.

4 AMR racing motors produce about 737 continuous horsepower, and 1622 peak, which may well actually be too much for an '82. What would be the limiting factor there? I'll have more of a look at battery packs, but I'm planning to supply the inverters at 700 volts to decrease the current draw. Do you have any suggestions as to potential batteries?

I thought for a while about using a larger motor (AMR 250-90 dual) on the rear axle, but I couldn't find a way to get that to meet my goals without using some sort of transmission, and those are very underdeveloped for electric cars at the moment. The reason Tesla uses AWD for their high performance EV's is because they couldn't get transmissions working reliably, so they went to a different gearing for the front and back. 

I found some Tesla Drive units at StealthEV, I'll run the numbers for those.

Also at Stealth EV I found my motor controllers: Cascadia Rinehart PM250Z's. And they are ludicrously expensive, at $13,000 apiece. And I would need one per wheel. I'll have a look at the Tesla Drive units.


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## brian_ (Feb 7, 2017)

Jomp135 said:


> First, what is the best way to convert an '82 corvette from having a nondriven front axle to having a driven front axle? I don't need most of the features associated with AWD. The way I see it, I just need an FWD axle that can go in an '82 Corvette, but what would that be?


All Corvettes have double A-arm (double wishbone) front suspension, and should retain that. So the two options are to change the hubs and hub carriers to ones which could be drive, or to completely swap the suspension for something that has driven double A-arm from suspension... which is more likely to be found in an AWD vehicle than anything just front wheel drive. Regardless of the suspension, the frame rails will probably be in the way of the axle shafts; pickup trucks and SUV routinely have driven front axles with double A-arms and a ladder frame, but the are designed to fit that, with the frame well above the axle line.



Electric Land Cruiser said:


> This guy made a 4WD C3 Corvette by using a Caddy Eldorado front end, so maybe the Cadillac FWD axles and hubs would bolt up to the C3 suspension, or close enough to make work: The World’s Only 4WD Hemi-Powered Corvette -


This is a rare example of front wheel drive with double A-arms, and would be good if the parts work... although all of the components are antiquated. That 4WD Hemi-powered C3 uses the complete Eldorado suspension and part of the frame, not just hub components; I don't know how well they would suit the Corvette. These components are not specifically Cadillac (Eldorado); the same chassis was used first for the Oldsmobile Toronado, and later for the Buick Riviera and even the GMC Motorhome, from 1966 through 1985 1979-1985 was a lighter version).



Electric Land Cruiser said:


> Personally, I think RWD suits the Vette more. EV conversions should be built to the original car's strengths. One great thing about a Vette is the rear transaxle, which means that it's already set up for a rear engine EV conversion!


A 1982 is the third-generation Corvette (C3), and doesn't have a rear transaxle; that didn't start until the C5 for 1997. Even then, the rear face of a motor attached to the front (input) of the C5 transaxle would be well ahead of the rear wheels; the front of the motor would run into the seats. Splitting the transmission section from the final drive would move the motor back, but it would still be entirely ahead of the axle (how far depending on how much length the required reduction gearbox would take).

But I agree - the proportions of the car are designed for RWD. With any rational component placement it will be neutral to tail-heavy, and during acceleration load shifts to the rear tires, so most of the power will be needed at the rear even with AWD. Some very high performance cars that would normally be RWD have gone to AWD for better control, and that makes sense, but in that case the front motors can be substantially lower-power than the rear.


*Rear suspension*
The discussion of front suspension brings up an issue: the rear dual-motor drive unit would replace the stock rear final drive (differential) unit, but the suspension uses it. In the C2/C3/C4 rear suspension, the axle shafts also serve as suspension components, transmitting lateral load through the diff bearings and final drive case to the vehicle structure. The new drive unit would need to handle the same forces (which are not normally handled by a final drive or transaxle), unless the suspension is converted to use a separate upper control arm. This same concern exists with any EV drive unit, including one from a Tesla.


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## brian_ (Feb 7, 2017)

reiderM said:


> You're better off using 2 tesla drive units, one for the front and one for the rear. All the power you could possibly dream of, while only needing to deal with 2 inverters instead of 4.


Total power isn't the problem. One Tesla large drive unit is enough for the car, if total peak power is the only concern. Dealing with more inverters also means not needing differentials and having (if the controls are done properly) excellent traction control (better than any limited-slip diff can achieve).


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## brian_ (Feb 7, 2017)

Jomp135 said:


> Also at Stealth EV I found my motor controllers: Cascadia Rinehart PM250Z's. And they are ludicrously expensive, at $13,000 apiece. And I would need one per wheel. I'll have a look at the Tesla Drive units.


Yes, high-power AC motor controllers/inverters are insanely expensive. This is a major reason why the current trend is to salvage complete drive units from production EVs, complete with the controller/inverter.


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## brian_ (Feb 7, 2017)

Jomp135 said:


> I was looking at an 80kwh battery bank, but I haven't settled on what batteries to use yet.


Okay, but have you considered where all that battery would go in a C3, especially with a front drive unit taking some prime space?


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## brian_ (Feb 7, 2017)

Jomp135 said:


> I thought for a while about using a larger motor (AMR 250-90 dual) on the rear axle, but I couldn't find a way to get that to meet my goals without using some sort of transmission, and those are very underdeveloped for electric cars at the moment.


What do you mean by "transmission"? A gearbox that transmits power is a transmission - every EV has one, and you will have four (or two if you give up on individual motors per wheel and go with one per axle). If you mean a *multi-ratio* (typically only two-speed) transmission... yes, almost all EVs avoid that. But they work for the few that use them, and most companies which make transmissions for EVs offer a two-speed version.

The AMR 250-90 dual motor is simply two AMR 250-90 single motors in the same case. Using that dual-core motor instead of two single-core motors would make no difference to the performance or gearing requirements.




Jomp135 said:


> The reason Tesla uses AWD for their high performance EV's is because they couldn't get transmissions working reliably, so they went to a different gearing for the front and back.


That's nonsense from some Tesla fan who with no technical understanding. Tesla failed with two-speed transmissions early in the Roadster era, and never built an AWD Roadster. AWD and two-speeds are unrelated.

Tesla has AWD for the same reasons as everyone else: better traction, better stability. The front and rear drive units in some Model S and X variants are only different in ratio because they have different motors (small at the front and large at the rear) due to re-using existing components (small from the original AWD with matched front and rear motors; large from the original RWD). Someone at Tesla came up with the idea of changing the power distribution between front and rear based on speed to take advantage of the different drive units' operating characteristics, but the gearing different is both small and irrelevant. Having two motors both driving all the time through unchanging ratios is very different from having a motor driving through a two-ratio transmission.


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## Jomp135 (Mar 20, 2021)

brian_ said:


> .. yes, almost all EVs avoid that. But they work for the few that use them, and most companies which make transmissions for EVs offer a two-speed version.


I didn't know that, so far all I've been able to find are:
The Taycan Transmission, which is impossible to find on the aftermarket
The Inmotive transmission, which only supplies to OEM's (and I haven't been able to find any that use it)
Borg Warner, who made both a transaxle and a linear transmission, but who I think have stopped producing those. Plus, I can only find the transaxle, which can't take the loads I want. 

I'm still looking at Tesla Drive units, but I'm trying to figure out what motors they use so that I can get power curves to plug into my equations. Anyone know what motors are used by this, or this?


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## Isaac97 (Jun 3, 2019)

Jomp135 said:


> I'm still looking at Tesla Drive units, but I'm trying to figure out what motors they use so that I can get power curves to plug into my equations. Anyone know what motors are used by this, or this?


Those are Tesla's motors so it's not very easy to get detailed specifications. However, you should be able to figure some things out by looking at max torque and max horsepower; when torque * rpm = max hp, there you have the 'knee' of the torque curve. (there are of course other conversion factors necessary.) 

One issue with Tesla units is that they have fairly tall gearing and thus will have issues getting up to 180mph; 9.73:1 in the large motor, with a maximum motor RPM of 18,000. And at that RPM you won't have much torque. So different gear sets might be necessary; Zero EV sells a 4.5:1 gearset which should give you excellent top speed at the expense of torque. (300mph top speed anyone?)


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## brian_ (Feb 7, 2017)

Jomp135 said:


> I didn't know that, so far all I've been able to find are:
> The Taycan Transmission, which is impossible to find on the aftermarket
> The Inmotive transmission, which only supplies to OEM's (and I haven't been able to find any that use it)
> Borg Warner, who made both a transaxle and a linear transmission, but who I think have stopped producing those. Plus, I can only find the transaxle, which can't take the loads I want.


Yes, they're rare in production, and some of the two-speed transmissions which are available have not been selected by any manufacturer. As an individual builder you can't buy from the manufacturers, aftermarket suppliers won't have them, and salvaging used units from production EVs is of limited practicality.

The Taycan rear transmission is impossible to find because the vehicle is too new, and even in a few years it will still be expensive because the car is so expensive. The best-known example might be the Rimac Concept One... and they only made about 7 of those cars.

I'm not really suggesting the you could reasonably find a two-speed transmission to use, just that they are possible and even reasonable to make - they are rarely used because they are not needed, not because they can't be or haven't been built.


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## brian_ (Feb 7, 2017)

Isaac97 said:


> One issue with Tesla units is that they have fairly tall gearing and thus will have issues getting up to 180mph; 9.73:1 in the large motor, with a maximum motor RPM of 18,000. And at that RPM you won't have much torque. So different gear sets might be necessary; Zero EV sells a 4.5:1 gearset which should give you excellent top speed at the expense of torque. (300mph top speed anyone?)


I think you meant that they have fairly short gearing for high speed: the terminology (which can be confusing) is that a greater reduction ratio is suited to lower speeds and is called "short"; a lower reduction ratio is suited to higher speeds and is called "tall". 

The overall gearing of the Tesla drive units (and almost every EV drive unit) is short compared a typical engine-driven car in high gear, with an overall ratio of about 10:1 versus about 3:1 for a typical car. The short gearing is made possible by the high motor speed which is possible, and it limits the top speed of the car. The motor can produce full power to nearly the top motor speed, so top speed is limited by the safe motor speed, not the availability of power.

At the other speed extreme, the overall gearing of the Tesla drive units (and almost every EV drive unit) is a bit tall compared a typical engine-driven car in low gear, with an overall ratio of about 10:1 versus about 15:1 for a typical car. The tall gearing is made possible by the high motor torque at low speed, but still limits the low-speed acceleration of the car. In the highest-powered EVs it's not a problem because even with this gearing the available torque to the wheels still exceeds available tire traction and is far beyond what is useful on the road.

To reach extreme high speeds and still have extreme low-speed performance two ratios are beneficial, and that's why the Taycan has them. For sane people, that's not required; even on a race track, more than 250 km/h (155 mph) is of little use.


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## MattsAwesomeStuff (Aug 10, 2017)

I've never seen an EV converted this way.

I love weird solutions and I love Corvettes, so, I'm quite excited to see what you come up with. Please stick around and keep documenting your build!


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## Bratitude (Jan 23, 2020)

Jomp135 said:


> So, I'm currently going through the design process for a high performance '82 Corvette electric car conversion. I'm looking at using AMR-250 90 single motors from EVWest, and after building a rather nifty calculator for spec analysis, I've figured out that the best way for me to meet my performance goals is to use 4 of them, one to power each wheel. I've looked at in wheel hub, and because of the associated performance issues with unsprung mass and the size of the motors, it's not practical. Because of this, I'm now looking at putting the motors in the axle assemblies: each motor will have a planetary gear reduction on the output, and that will be connected to a halfshaft connecting it to the wheels. It's essentially 2 motors pretending to be a very large differential. My problems are twofold:
> First, what is the best way to convert an '82 corvette from having a nondriven front axle to having a driven front axle? I don't need most of the features associated with AWD. The way I see it, I just need an FWD axle that can go in an '82 Corvette, but what would that be? Tell me if I would be better off posting this in another forum, by the way.
> Second, would my plan with the motors work?
> 
> Thanks!


sounds very very very expensive. just get a Lexus gs450h hybrid transmission, and the evbmw controller. it’ll pull hard. And be much much simpler, while keeping the rear end stock, and giving you a engine bay for batteries


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## brian_ (Feb 7, 2017)

Bratitude said:


> sounds very very very expensive. just get a Lexus gs450h hybrid transmission, and the evbmw controller. it’ll pull hard. And be much much simpler, while keeping the rear end stock, and giving you a engine bay for batteries


That would package nicely but it wouldn't even remotely approach the builder's performance goals, and wouldn't be AWD.

Why comment if you're not even going to read the discussion so far?


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## Bratitude (Jan 23, 2020)

brian_ said:


> That would package nicely but it wouldn't even remotely approach the builder's performance goals, and wouldn't be AWD.
> 
> Why comment if you're not even going to read the discussion so far?


he hasn’t stated numbers, and that set up could yield 350hp +
And there is a version with a awd transfer case.


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## brian_ (Feb 7, 2017)

Bratitude said:


> he hasn’t stated numbers, and that set up could yield 350hp +


He has given performance targets, and 350 hp would be far short of adequate:
​


Jomp135 said:


> My goals going in were:​180 mph top speed​2.5 second zero to 60​...​​


​


Bratitude said:


> And there is a version with a awd transfer case.


True... if there were only space under a Corvette floor for a transfer case and a shaft to the front, where a drive axle would take almost as much space as just running a separate front drive unit.


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## Jomp135 (Mar 20, 2021)

I'm pretty sure that I'll still be able to put plenty of batteries in the engine bay: the '82 Corvette is almost 1/2 hood. Tesla battery modules are 27 by 11.5 by 3.5 inches, and looking at build space I'd say I have about 60 by 30 by 20 inches of hood space between the front wheels and the driver space. Using an ideal packing, I can fit about 20 battery modules in there, although I'd only use 16 at most in that space. That solves my battery storage problem.

One question I have is regarding the gearing on the Tesla motors: if the back motor tops out at 16,000 rpm and has a gear reduction of 9.73:1, then that connected to 20 inch wheels would top out at about 98 miles per hour. Given that this is the Tesla Ludicrous speed drivetrain which apparently tops out at at least 155 mph, there has to be something I'm missing. Maybe StealthEV posted the wrong reduction ratio?


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## kstegath (Nov 4, 2008)

I have a lot of experience with the C3. I converted a C3. For enough money, any thing is possible.
Realistic number: $60K without batteries.


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## Isaac97 (Jun 3, 2019)

Jomp135 said:


> I'm pretty sure that I'll still be able to put plenty of batteries in the engine bay: the '82 Corvette is almost 1/2 hood. Tesla battery modules are 27 by 11.5 by 3.5 inches, and looking at build space I'd say I have about 60 by 30 by 20 inches of hood space between the front wheels and the driver space. Using an ideal packing, I can fit about 20 battery modules in there, although I'd only use 16 at most in that space. That solves my battery storage problem.
> 
> One question I have is regarding the gearing on the Tesla motors: if the back motor tops out at 16,000 rpm and has a gear reduction of 9.73:1, then that connected to 20 inch wheels would top out at about 98 miles per hour. Given that this is the Tesla Ludicrous speed drivetrain which apparently tops out at at least 155 mph, there has to be something I'm missing. Maybe StealthEV posted the wrong reduction ratio?


That sounds like a plan. Keep in mind that all that battery will be pretty heavy and will certainly affect performance.

16,000 / 9.73 = 1644 wheel RPM.
20" wheel diameter = 1061 rev/mile. Yup, that creates ~95mph.
Now consider the Model S. 245/45R19 tires are 751 rev/mile. Bam, 131mph. (top speed of LR model S? 135.)
HSRMotors specs 18,000 rpm max for their 'sport plus' unit. That reaches 147mph. (top speed of performance model S? 155.)

The reduction ratio is known to be correct.

If you use smaller tires, the 4.5:1 gearset will actually work better, since it'll push you to ~200mph with 20" wheels. (that is total diameter incl. tires.)


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## Jomp135 (Mar 20, 2021)

Okay, that makes sense. Do you know where I could get that gearset?

Edit: Nevermind, I found it with one search.


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## brian_ (Feb 7, 2017)

Jomp135 said:


> One question I have is regarding the gearing on the Tesla motors: if the back motor tops out at 16,000 rpm and has a gear reduction of 9.73:1, then that connected to 20 inch wheels would top out at about 98 miles per hour. Given that this is the Tesla Ludicrous speed drivetrain which apparently tops out at at least 155 mph, there has to be something I'm missing. Maybe StealthEV posted the wrong reduction ratio?


No, the problem is the 20 inch dimension. We're not talking about golf carts or microcars here.



Isaac97 said:


> 16,000 / 9.73 = 1644 wheel RPM.
> 20" wheel diameter = 1061 rev/mile. Yup, that creates ~95mph.


Without checking the math, that looks right. 



Isaac97 said:


> Now consider the Model S. 245/45R19 tires are 751 rev/mile. Bam, 131mph. (top speed of LR model S? 135.)
> HSRMotors specs 18,000 rpm max for their 'sport plus' unit. That reaches 147mph. (top speed of performance model S? 155.)


The issue with the original value does appear to be that the calculation must use the overall diameter (and thus the outside circumference) of the tire, not just the bare wheel. The easy (and most accurate) method is to get that revolutions per mile (or kilometre) value from tire specification charts, as shown here. The overall diameter of a 245/45R19 is nominally 703 mm or 27.7", and a random brand (Michelin) and model shows 28" overall and 743 rev/mile... exact dimensions vary. 



Isaac97 said:


> The reduction ratio is known to be correct.


Yes, it's published by many sources. When a calculation comes up way off of published values, it's time to check the calculation.



Isaac97 said:


> If you use smaller tires, the 4.5:1 gearset will actually work better, since it'll push you to ~200mph with 20" wheels. (that is total diameter incl. tires.)


True, but no one is going to use 20" tall tires. A stock 1982 Corvette had 225/70R15 or 255/60R15 tires, which are about 27" tall... almost as tall as the base Tesla Model S tires.

The 4.5:1 gearset is for people who want to feed the Tesla drive unit outputs into front and rear final drive units (differentials) with their own substantial gear reduction; it is not useful for driving wheels directly in street-driven vehicles.


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## brian_ (Feb 7, 2017)

Jomp135 said:


> I'm pretty sure that I'll still be able to put plenty of batteries in the engine bay: the '82 Corvette is almost 1/2 hood. Tesla battery modules are 27 by 11.5 by 3.5 inches, and looking at build space I'd say I have about 60 by 30 by 20 inches of hood space between the front wheels and the driver space. Using an ideal packing, I can fit about 20 battery modules in there, although I'd only use 16 at most in that space. That solves my battery storage problem.


Here's a suggestion: make a cardboard box 60" by 30" by 20", take it to the car, open the hood, and figure out how that entire box is going in there. When reality sinks in, start again...

Realistically, you have just the space currently occupied by the engine (with accessories), which is roughly half of that five feet, and narrower that you might guess looking at the outside of the car. The modules need to go in a supporting structure, and surrounded by a box. The suspension, steering, and brake master cylinder still need to be there (as well as a whole front drive unit if you're still thinking AWD). Although the stock radiator is larger than required, the drive unit and battery will still need a cooling system with radiator. About half of those 20 Model S/X modules will actually fit.

If you do extend modules way up into the nose, there's no need for a drive unit, as the result will handle so badly that there is no point in driving it.


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## Electric Land Cruiser (Dec 30, 2020)

180MPH is FAST. I would focus on going 100MPH first. If you can do that then changing gear ratios to go faster is no problem.


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## Frank (Dec 6, 2008)

A Gear Vendors 2 speed will handle a lot of torque. 

Sent from my SM-T380 using Tapatalk


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## Frank (Dec 6, 2008)

GV is an overdrive transmission.... 

Sent from my SM-T380 using Tapatalk


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## Jomp135 (Mar 20, 2021)

Okay, let's go through this:

1. I made a pretty big mistake in my calculations: I mixed up wheels and tires. You're absolutely right, I should have been doing it with about 27.7 inch tires. 
2. I see your point, and I'm going to shrink my goals. I'll try for a top speed of 150 mph, but I can't really go lower without compromising my goals: the stock 82 has a top speed of 130, and I want to outperform that.
3. I'm going to have another look at the AMR motors, because I was comparing constant supply for those to peak supply for the Tesla drive unit. It will be expensive, but I'll see if I can meet my new goals with just 2 of the motors in the rear, keeping the corvette RWD.


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## Jomp135 (Mar 20, 2021)

So I'm back from doing some number crunching, and the results are okay. I can use 2 motors in the back, and I can get 3.5 second zero to 60 with a 130 mph top speed. I can also get 4.2 second zero to 60 with a 150 mph top speed. (Additionally, this is with significant aerodynamic improvements.) It would be easier and cheaper to do this than to have 4 motor AWD in a car built for RWD, and it would free up more space in the front for batteries as well. My main problem, though, is that this feel's like it's not enough. My whole goal with this is to make an electric car conversion that blows most cars under a million dollars out of the water, for considerably less. That's another thing too, the performance on paper scales with cost, but I can't really justify spending probably $80,000 on a car with specs that are, while not lackluster, considerably worse than if I went a little further. 

If I use 3 motors, the specs get much better. 
This gives me a 0-60 of 3 seconds with a top speed of 160 mph, but it would necessitate me replacing the front axle assembly, and making some significant frame modifications. 
I could also configure it for 0-60 in 3.5 seconds, which would have the benefit of letting me reach 300 km/h: in just 11.9 seconds. That is what we call blowing multimillion dollar cars out of the water for a fraction of the price. Tell me which one you think I should explore more. 

I would also need to find a front AWD axle assembly that I can swap into the frame, so tell me if there are any options that spring to mind for that. It might actually be cheaper to just look at different classic cars that are already AWD, because although I personally think that the C3 corvettes are some of the most beautiful cars ever made, I'm open to other cars if they'd be easier.


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## kstegath (Nov 4, 2008)

1982 C3 Corvette Frame 
NetGain 11" DC Motor




















Battery space and layout: Twelve 12V lead-acid in front; twelve 12V lead-acid in the rear.


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## Electric Land Cruiser (Dec 30, 2020)

@Jomp135 that is awesome that you are aiming for such high goals. Have you seen snowdog's Electric Supercar build? Definitely see what he is doing. He is actually getting those 0-60 times that you want in his own DIY EV car. It's so cool: Electric Supercar


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## Jomp135 (Mar 20, 2021)

Yeah, I'm actually thinking about changing the donor car over to a Factory 5 GTM. I don't have the corvette yet, and if I switch over to the GTM I'll have a much better and safer car, with more downforce. I'll probably configure it for 300 km/h top speed, because that will give me 2.8 second 0-100 km/h times, and 9.9 second 0-300.

What do you think?


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## Electric Land Cruiser (Dec 30, 2020)

I like your plan. Not that an '82 Vette is a bad car, they actually have ton of strengths like you've mentioned, and 82's are one of the coolest looking out there IMO. The issue is that making a 40 year old Corvette go 180MPH is probably just as much of a task as making a DIY EV whereas the Factory 5 just needs a powerplant. Not to mention the safety of a caged, modern car vs. a fiberglass one.


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## brian_ (Feb 7, 2017)

Jomp135 said:


> Yeah, I'm actually thinking about changing the donor car over to a Factory 5 GTM. I don't have the corvette yet, and if I switch over to the GTM I'll have a much better and safer car, with more downforce. I'll probably configure it for 300 km/h top speed, because that will give me 2.8 second 0-100 km/h times, and 9.9 second 0-300.
> 
> What do you think?


If you have the budget and the time, building a GTM as an electric would certainly produce a better car (aside from aesthetics, which is just personal opinion).

This would presumably be RWD only. People have discussed building an AWD GTM, but it makes no sense because it is not designed for that and uses Corvette (C5) front suspension components... although this sort of thing has been done with other RWD cars.

It looks like there has been at least one electric GTM built, and a few discussed, but I don't know how many have been completed or if there are any with components that make sense now. The obvious components would be a Tesla Model S large drive unit and a battery pack split between the engine and fuel tank spaces.

Of course any similar kit (tubular steel frame, body in the general style of a race car such as the Ford GT40) is a potential candidate. With any of these kits you will hit the problem that frame tubes are located where they are in the way of fitting in the bulky and inflexible battery modules, because the frame is designed to work with an engine and a fuel tank that can be shaped to fit the available space. The GTM uses stock Corvette C5 "saddle" tanks, which makes sense for gasoline but are two small and awkward volumes to try to pack any battery module into.


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## Swing (Apr 25, 2021)

Awesome project if this becomes anything close to your goals.

I see the remarks about the Lexus transmissions as a much cheaper option, but will not reach your goals. But I agree with spending much more, it has to be justifyable.

One thing though about Lexus transmissions. They are one of few gearboxes out there that come with a (planetary) 2 speed gearbox from factory.
I don't mean the motor itself, which is equal to a Prius, I mean the two speed behind it.
And don't forget you could still bolt another big electric motor to the whole Lexus transmission case. Giving you 3 motors and a 2 speed gearbox. Lexus GS450h goes to 270km/h from factory and you could run a different final gear in the back. Lexus LS600h gives you AWD.
Anyway, I get it that you might choose a different route to compete with million dollar cars.
However, just wanted to say it is not a bad option, bringing the cost down and still giving you nice performance.


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## BudgetDreams (Jun 14, 2021)

An 89 Corvette with a blown engine costs almost nothing, so could a super low budget, low range accepted, low top speed, no regenerative brake car-build use a Corvette body and participate in autocross?
It seems one motor in the transmission tunnel and a minimal set of batteries for ~6 minutes total race time would weigh less than stock, which would increase performance around the twisties.
How much weight in batteries would be needed for racing, and how much in a removable pack to get ~50 miles range?
Would using a Corvette body be any more expensive than using a Honda Civic?

What's the cheapest it could be built, still doing 0-60 in under 6 seconds or better, and what equipment would you use?


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