# Why don't use a Multispeed Gearbox in Electric Cars?



## nimblemotors (Oct 1, 2010)

yeah why not, go ahead and use gears! 
You'll just carry around some more weight in your car, and if you are an OEM, having a transmission manufactured to your specs might cost multi-billions extra. In a junkyard a transmission cost $100.



leonheart said:


> Hi
> I'm new in this Forum and I don't speak english very well so I apologize if sometimes I'm wrong.
> 
> My principal question is the title of this Thread: Why don't use a Multispeed Gearbox in Electric Cars?
> ...


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## leonheart (Mar 2, 2011)

nimblemotors said:


> yeah why not, go ahead and use gears!
> You'll just carry around some more weight in your car, and if you are an OEM, having a transmission manufactured to your specs might cost multi-billions extra. In a junkyard a transmission cost $100.


So, the cost of production are the only reason for don't produce, in a single prototype too, a specs gearbox? It's impossible to get a gearbox to another car and modify just the final trasmission*? 
Correct me if I'm wrong.

*: If it's possible modify the final transmission like in the motorcycle, replacing front and rear sprocket (Crown and pinion in the motorcycle transmission)


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## Woodsmith (Jun 5, 2008)

The main issue, I think, is that a multiple speed transmission is only used *if* it is actually needed.
With an ICE many ratios are needed because the power and torque curve of the ICE is in such a narrow band.
The change points may be from peak torque at 2500rpm to peak power at 4000rpm so only 1500rpm to work with.

An electric motor could be peak torque at 0rpm to peak power at 4000rpm so there is 4000rpm to play with and so fewer ratios needed.

With an electric drive if it can drive, accelerate and reach the required top speed direct drive or with only two ratios then why have more?

Much of the time people doing DIY conversions only use a couple of gear ratios and some even try to remove the unused gears from the box to save weight and drag.
Those who can manage with a single gear ratio will even remove the transmission completely.


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## leonheart (Mar 2, 2011)

Woodsmith said:


> The main issue, I think, is that a multiple speed transmission is only used *if* it is actually needed.
> With an ICE many ratios are needed because the power and torque curve of the ICE is in such a narrow band.
> The change points may be from peak torque at 2500rpm to peak power at 4000rpm so only 1500rpm to work with.
> 
> ...


Yeah, It's true, but i think that an huge torque could be used to have more top speed ('cause we have it from 0 to 4'000rpm) and acceleration too.
I think that a multi speed transmission could accentuate the acceleration and increase top speed than a single ratio do. Generally, the problem in the electric car is the low top speed respect the provided power. This in the ICE motor is the opposite. 
In see ICE car go over 170km/h with just 75hp, why don't have an electric car that do that with more acceleration?


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## rwaudio (May 22, 2008)

leonheart said:


> Yeah, It's true, but i think that an huge torque could be used to have more top speed ('cause we have it from 0 to 4'000rpm) and acceleration too.
> I think that a multi speed transmission could accentuate the acceleration and increase top speed than a single ratio do. Generally, the problem in the electric car is the low top speed respect the provided power. This in the ICE motor is the opposite.
> In see ICE car go over 170km/h with just 75hp, why don't have an electric car that do that with more acceleration?


A transmission is there to multiply torque, it doesn't really have much to do with HP. Since the electric motor can have full torque from 0rpm then you don't need to multiply anymore. 

Many electric conversions use controllers with high peak current, but fairly low continuous current, this could have something to do with why they don't all go "fast", you might be into current limiting on a Curtis/Zilla etc. when you really need the power at much higher speeds. I would imagine that a water cooled Soliton1 would have a better shot at making the electric comparable to a gas car. Then it comes down to how well your motor can handle (get rid of) the heat for extended periods of time. 

When there are high power, light weight, water cooled AC motors I'm sure we will see a change in what "fast" is in an EV.


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## MalcolmB (Jun 10, 2008)

leonheart said:


> In see ICE car go over 170km/h with just 75hp, why don't have an electric car that do that with more acceleration?


You're right of course, a two-speed transmission can give you improved starting torque and a top speed comparable with that of ICE cars. BUT, to get 75 hp at the wheels you'll need close to 75 kW from the battery. With a moderate battery capacity of 15 kWh that gives you a run time of less than 12 minutes.

As the energy density of batteries improves I'm sure there will be more demand for gearboxes designed or adapted for EVs. In the meantime a lot of people make do without, because it makes things simpler and cheaper, and because high speeds drain the pack so much faster.

That's obviously a simplification, and there are still efficiency and performance advantages to using a multi-speed transmission. Try doing a search for "powerglide" on this forum.


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## leonheart (Mar 2, 2011)

rwaudio said:


> *A transmission is there to multiply torque*, it doesn't really have much to do with HP. Since the electric motor can have full torque from 0rpm then you don't need to multiply anymore.
> 
> Many electric conversions use controllers with high peak current, but fairly low continuous current, this could have something to do with why they don't all go "fast", you might be into current limiting on a Curtis/Zilla etc. when you really need the power at much higher speeds. I would imagine that a water cooled Soliton1 would have a better shot at making the electric comparable to a gas car. Then it comes down to how well your motor can handle (get rid of) the heat for extended periods of time.
> 
> When there are high power, light weight, water cooled AC motors I'm sure we will see a change in what "fast" is in an EV.


Yes, but a transmission could multiply the Wheel RPM too. If we have a ratio less than 1 we have more RPM at the wheel than at the motor. If we have 2 or more ratio, we could multiply at first the torque to increase acceleration and finally more top speed. Maybe I was not clear when I explained my question, I know is not NECESSARY but I think is usefull to have more performance from the same motor.
Are here in the forum someone who modified the transmission of a car for his conversion?


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## leonheart (Mar 2, 2011)

MalcolmB said:


> You're right of course, a two-speed transmission can give you improved starting torque and a top speed comparable with that of ICE cars. BUT, to get 75 hp at the wheels you'll need close to 75 kW from the battery. With a moderate battery capacity of 15 kWh that gives you a run time of less than 12 minutes.
> 
> As the energy density of batteries improves I'm sure there will be more demand for gearboxes designed or adapted for EVs. In the meantime a lot of people make do without, because it makes things simpler and cheaper, and because high speeds drain the pack so much faster.
> 
> That's obviously a simplification, and there are still efficiency and performance advantages to using a multi-speed transmission. Try doing a search for "powerglide" on this forum.


Really thanks MalcomB.


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## Woodsmith (Jun 5, 2008)

leonheart said:


> Yes, but a transmission could multiply the Wheel RPM too. If we have a ratio less than 1 we have more RPM at the wheel than at the motor. If we have 2 or more ratio, we could multiply at first the torque to increase acceleration and finally more top speed. Maybe I was not clear when I explained my question, I know is not NECESSARY but I think is usefull to have more performance from the same motor.
> Are here in the forum someone who modified the transmission of a car for his conversion?


I know what you are getting at.
You are suggesting that one could gear an EV so that the motor is spinning at, say, 100rpm and travelling at 100mph because there is sufficient torque in the hypothetical motor to do that. You are supposing that it would equate to 200mph at 200rpm, still running close to maximum torque.

Well, if there was enough torque to overcome the various resistances I guess in theory it may work as a purely mechanical thing (though the gear wheels will be massive to cope with the enormous stresses) but the motor will be drawing maximum current for long durations and running very inefficiently.
It would be a toss up of which bit failed first, the motor over heating and burning out, the controller shutting down, the batteries melting, the cables/breakers giving up.

There are very good reasons why an EV will aim to cruise at near maximum rpm as that is when the current is lowest and efficiency highest for that speed.

If you were to want to drive at very high speed you would work you ratios to get the highest motor speed that just provided enough torque to maintain that speed and no more.

In the real world....
Actually you are not looking at real world are you, so it doesn't matter for now.


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## rwaudio (May 22, 2008)

leonheart said:


> Yes, but a transmission could multiply the Wheel RPM too. If we have a ratio less than 1 we have more RPM at the wheel than at the motor. If we have 2 or more ratio, we could multiply at first the torque to increase acceleration and finally more top speed. Maybe I was not clear when I explained my question, I know is not NECESSARY but I think is usefull to have more performance from the same motor.
> Are here in the forum someone who modified the transmission of a car for his conversion?


What I'm getting at is the ratio's aren't what's holding back EV's from being fast. Many people keep the transmission, me included but that doesn't mean I'm going to have a 160+mph car.


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## michaeljayclark (Apr 3, 2008)

not looking to go fast, just 70 is fine for me.

my conversion has a 3.42 rear end. I want to have a one speed transmission as the original poster has said. he was merely looking for someone that is using something else instead of the transmssion.

I have been looking at custom airplane gearbox reducers. these I believe could be adapter to our purpose as well.

http://glasairproject.com/Marcotte/Page2.html

a basic site dedicated to these gearboxes. 

If I have a 1.81 gearbox, the motor would be at 74 rpm at 1 mph, then at 5212 rpm at 70 mph.

final gear ratio of 6.19. seems to be just about perfect. perfect would be 3.83 rear end gear but close enough.

I have contacted the site owners for more information.


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## dtbaker (Jan 5, 2008)

...and you really do need some rpm to drive the internal fan for a little cooling.


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## Duncan (Dec 8, 2008)

Hi Leon

A gearbox can give you additional torque at lower speeds - good idea -*Until you can't use any more torque!*
If you can spin your driven wheels more torque is redundant!

The Tesla can do 0-60mph in 3.7 seconds - I don't think it will be able to put any more torque on the ground (with road tires)
Its top speed is 125mph - enough to get a ticket almost everywhere!

For a Tesla a gearbox is unnecessary weight and complication

For the rest of use - most of us are power limited as far as top speed is concerned but most EV's can get off the line fast enough to give an IC car a fright


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## Duncan (Dec 8, 2008)

Hi Michael 

Which drive are you using?
Can't you find a decent diff ratio to avoid the additional complexity?

My Subaru has a 4.1:1 diff - I think its the same diff as used in some Nissan's


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## michaeljayclark (Apr 3, 2008)

I am using this calculator

http://xse.com/leres/ss/calculator.html

I change the 1st gear ratio to 1.81 and all the others to 0.

I change the rear axle ratio to 3.42

my tire size is 235 70 15


then it changes and shows a final ratio of 6.19. it defaults to show at 55 rpm my motor is at 4589 rpm

MPH @ 6000 RPM is 71.9

its a great calculator.

what I am trying to do here is eliminate complexity. If we can eliminate the transmission we are reducing weight. we are also getting rid of 3 other gears we dont need in the EV. reverse is easy with a reversing contactor.

Ive been researching the gearboxes and it turns out electric boats us them. they have calculated that the gearbox is 97% efficient.

imagine looking at the transwarp motors from netgain that have a yoke attached at a 1:1 ratio. Imagine this gearbox attached to the back of the motor with a yoke to ujoint up to the rear end and having a choice of the gearbox ration to give your EV a final ratio of 6.2!

Ive been asking about how many RPM does kostov motors need to have before it sees actual amperage and doesnt melt. I havent been able to get too many answers unfortunately because I dont think the answer is truly known.

the more rpm the motor gets before it seems serious amperage the better! If I use a 1.81 ratio and hit the pedal to the metal my motor will be at 83 rpm when it see 600 amps from a solition jr. thats at 1 mph using the calculator. If I change the calculator to what rpm my motor will see at 2 mph is goes up to 167. at 3 mph its at 250 rpm....

an additional blower to blow air into the motor at lower rpms would only help and hey, Ive got a used blower motor that came out of a 1996 jimmy here that nnoone wants! (Ive listed it on craigslist, noone wants it )


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## Woodsmith (Jun 5, 2008)

michaeljayclark said:


> what I am trying to do here is eliminate complexity. If we can eliminate the transmission we are reducing weight. we are also getting rid of 3 other gears we dont need in the EV. reverse is easy with a reversing contactor.


I found this reversing gearbox that would save the electrical issues of reversing contactors.
Nova Racing - Reversing Gearbox.
It is used on motorbike engined Caterham Sevens, Triking Morgan replica, and other similar cars.


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## JRP3 (Mar 7, 2008)

Just thought I'd point out that Tesla tried to use a 2 speed gearbox and a number of vendors failed to build one that could handle the shift under full load without breaking. Since most people just don't care about going more than 125mph they decided to simply increase the power to the motor and skip the gearbox.


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## Guest (Mar 4, 2011)

The Tesla also has an AC motor which can run at a much higher RPM than the typical DC motor of the DIY crowd. The DC motor has better torque and we can use the transmission to our advantage and still go fast. You can change the final drive gear in the transmission to better utilize the limits of rpm with the DC motor. Most don't need to go 125 mph. Most are just regular vehicles on the road to get you from there to here or here to there. No need because speed limits are still in effect. 

Pete


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## DavidDymaxion (Dec 1, 2008)

Most of the successful single gear ratio electric cars have twin motors, or a single huge 13 inch motor. Using the tranny greatly lowers the startup current and heating, so you can use a single 9 or 11 inch motor instead.

If you really want it all, great startup and high top speed, you really need a transmission. The Buckeye Bullet (315 mph!) used a five speed tranny. If you are happy with a mere 170 mph (Killacycle) or 125 mph (Tesla or NEDRA racers) then a single gear can work great, provided you have a stout enough controller, motor(s), and pack.


leonheart said:


> Hi
> I'm new in this Forum and I don't speak english very well so I apologize if sometimes I'm wrong.
> 
> My principal question is the title of this Thread: Why don't use a Multispeed Gearbox in Electric Cars?
> ...


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## michaeljayclark (Apr 3, 2008)

still using a transmission, just not the ice transmission.

generally i think most just use 2nd gear in the manual transmission. the gear ratio is usually over 2 and therefore doesnt give the best gear ration band and the person must shift at speeds over 55.

i am suggesting a way to get a single speed gearbox and give us a final ratio of 6.2 and not spend 1000 dollars.

the single speed gearbox is also more efficient, something we need as well.


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## algea07 (Oct 1, 2010)

hi guys i was looking at the links you guys posted of the diff calculator and i just used the 24inch dia wheels and the 3.75 diff ratio (which seems to be close to what most cars use). and i found that at 60mph or 100km/h the motor revs at about *3000 rpm*.

i then had a look at the stats for the trans warp 9 and saw that at around 3000rpm was when the motor was at its most efficient at 87%-89%.

*so wouldn't it be best to keep the final drive ratio at around 3.5 - 4 (most diff ratios) so the motor spins at maximum efficiency?*

if you look at the stats the motor produces 15hp with 72V and under 200amps, which isn't that much current. 

having a ratio in this range also allows for a high top speed of well over 100mph, going of the maximum revs of the motor.
*
so why would you want to gear down the motor or have a gearbox at all?*


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## Anaerin (Feb 4, 2009)

algea07 said:


> *so why would you want to gear down the motor or have a gearbox at all?*


Torque, torque, torque. From a standstill, you have to overcome the inertia of the vehicle. The heavier the vehicle, the more torque you need. Smaller motors can't take the high current required to get large vehicles moving without overheating/zorching. So something like a Geo Metro could be direct driven with a Warp 11, possibly even a Warp 9 (Look at the "TransWarp" if you want a motor of that size already set up for direct drive). But something larger, like an F250, for example, would need a Warp 13, at least, if not a pair siamesed together, just to overcome it's standing inertia.

If you use a gearbox to gear down the motor, you gear up the torque, at the expense of speed, which makes a smaller motor more easily able to move a larger vehicle.


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## algea07 (Oct 1, 2010)

Anaerin said:


> If you use a gearbox to gear down the motor, you gear up the torque.


but wouldn't two warp nines with a drive ratio of 3.75 have more torque then one warp nine with a drive ratio of 6? and about the same weight.

given that you'll be spending at least $1000 (if you're lucky) on a gearbox of some type, wouldn't it be easier to and simpler and cheaper to buy the second motor? so you have the same torque and a much more comfortable top speed. you might have to put in a parallel/series switch if you're useing a low voltage controller.

and given the motor is close to 10% more efficient at a lower speed, and you would also have losses through the gearbox. you could be looking an increase of efficiency of around 15%, that's 15% more range or 15% less batteries and even less weight.
*
if the warp nine is happy to spin at 3000rpm*, i get why you'd use a gearbox that came with the car, but i cant see why you'd go out and buy one.


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## Anaerin (Feb 4, 2009)

algea07 said:


> but wouldn't two warp nines with a drive ratio of 3.75 have more torque then one warp nine with a drive ratio of 6? and about the same weight.


No. Because you would be more limited by the amount of power you can put through the hardware. If you try and crest about 1,000 amps, you'll find that all your hardware (controller, contactors, cabling, fusing) becomes considerably more expensive and more difficult to get.


algea07 said:


> Given that you'll be spending at least $1000 (if you're lucky) on a gearbox of some type, wouldn't it be easier to and simpler and cheaper to buy the second motor? so you have the same torque and a much more comfortable top speed. you might have to put in a parallel/series switch if you're useing a low voltage controller.


While it may be "Easier" at first glance, you have to remember that by doubling the number of motors, you have to increase the size of your battery pack to handle the extra load, increase the controller to deal with series or parallel (or switching) loads, and the difficulty in mating and keeping the motors in perfect sync. Given that a single motor will cost in excess of $1,000 (your quoted value), not accounting for all the other uprating that is required, it is cheaper and easier to get a racing gearbox from one of the many suppliers out there, and throw that in.


algea07 said:


> and given the motor is close to 10% more efficient at a lower speed, and you would also have losses through the gearbox. you could be looking an increase of efficiency of around 15%, that's 15% more range or 15% less batteries and even less weight.


If you look at that power curve, it is limited by the incoming power at lower speeds, until it reaches it's peak. That means the available power goes up linearly, whereas the load is inverse exponential.


algea07 said:


> *if the warp nine is happy to spin at 3000rpm*, i get why you'd use a gearbox that came with the car, but i cant see why you'd go out and buy one.


If you were using the gearbox that came with the car, but found yourself stripping gears because of the torque you're putting the box through, you might want to go and buy yourself a better gearbox.


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## EVfun (Mar 14, 2010)

algea07 said:


> but wouldn't two warp nines with a drive ratio of 3.75 have more torque then one warp nine with a drive ratio of 6? and about the same weight.
> 
> given that you'll be spending at least $1000 (if you're lucky) on a gearbox of some type, wouldn't it be easier to and simpler and cheaper to buy the second motor? so you have the same torque and a much more comfortable top speed. you might have to put in a parallel/series switch if you're useing a low voltage controller.


To the first question, yes. Two 9 inch motors wired in series will make twice the torque of a single 9 inch for the same amps. The motors wired in series will only see half the voltage so they will run out of steam (quit taking the amps) at about half the rpm. Of course, the lower gearing proposed with the single motor also means it will run the motor rpm up higher so the single motor will also run out of steam. With a series wound motor voltage allows rpm while amps create the torque.

The thing is, the tranny is generally in your car, it is basically free when you do a conversion. A 9 inch motor is around $1800 while good used tranny is just a couple hundred at a auto salvage yard. So even if you need to get a tranny it is cheaper. 

I would be inclined to use 2 motors and ditch the tranny, but it isn't for efficiency or to save money. It is to be quieter, not have a clutch to burn up, and to run the pack voltage higher than most of the motors we are using can take.


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## michaeljayclark (Apr 3, 2008)

getting this single speed transmission isnt much to make. it will be the same as going to a junkyard and getting a transmission without the worry of it beiong damaged in some way.

no clutch, only 2 gears to run power through, viola, more efficient and less than 1000. 

I wouldnt propose such an item unless the cost is down where it makes sense.

he bar is set to keep prices around $10,000. 

this single speed transmission is looking good to be made here on a cnc machine, just need to get the drawing made and machine it out.

when done it will be offered to everyone. I would really like to mate it with a kostov motor and it be the transwarp but not 1:1, able to be made with all the different ratios available to choose from.


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## Duncan (Dec 8, 2008)

Michael

Why would I use *two* non shift-able step down gear sets when I could use one?? 

For a lot less than the cost of your step down I could find the correct ratio diff

That give me *one* properly engineered step down


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## DavidDymaxion (Dec 1, 2008)

Possible reasons:


The particular car's diff doesn't have the needed ratios available
You have an AC motor that spins 12,000 rpm -- there are no rearends that'll gear that down enough in 1 step
You don't want to spin the driveshaft designed to spin at 2000 rpm at 5000+ rpm (BTW the Porsche 924/944 is the only car I'm aware of that spins the driveshaft at motor rpm)



Duncan said:


> Michael Why would I use *two* non shift-able step down gear sets when I could use one??
> 
> For a lot less than the cost of your step down I could find the correct ratio diff
> 
> That give me *one* properly engineered step down


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## JRP3 (Mar 7, 2008)

DavidDymaxion said:


> You don't want to spin the driveshaft designed to spin at 2000 rpm at 5000+ rpm (BTW the Porsche 924/944 is the only car I'm aware of that spins the driveshaft at motor rpm)


I'd think any car that has 1:1 transmission gears spins the drive shaft at motor RPM's.


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## DavidDymaxion (Dec 1, 2008)

Thanks for the post, I wasn't completely clear in my post. Your car's driveshaft average rpm will be much lower than 5000 rpm, and most folks will never come close to 5000 rpm on their driveshaft in daily driving. Hitting 5000 rpm briefly, as in drag racing or on the road racing track is one thing. Running the driveshaft at 5000 rpm as a matter of course, for an hour a day as part of a regular commute, is something that would make me a bit nervous. That's pushing twice the speed and 2 to 4x the average load of typical freeway speeds. Are the lubrication, balance, u-joints, and seals designed for that kind of continuous load?

Here are a couple of cases in point: When my car has the driveshaft going 5000 rpm, the car is going 120 mph. The highest sustained rpm it sees in daily driving is 3300. Despite being geared very low, the highest sustained rpm my truck's driveshaft sees is 3500.

The Porsche 924/944/928/Newer Corvette design is a special case as you can be driving the driveshaft at max rpm in every gear and at low speeds, such as climbing hills.


JRP3 said:


> I'd think any car that has 1:1 transmission gears spins the drive shaft at motor RPM's.


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## Duncan (Dec 8, 2008)

Hi David

If you fit a higher ratio diff you increase the drive-shaft speed.
However you only increase its average speed - its maximum speed is set by the motor maximum speed

I don't think it will make any difference to drive-shaft life - the vehicle manufacturer will have tested it at max revs continuously 

Which is normally an easy test - its the speed/load cycles that are the more strenuous tests 

If you could get a 12,000rpm motor and a very high ratio diff to match - then you would have to get a high speed drive-shaft to go with it!!

(Bets it would be a lot cheaper than the motor or the diff-)


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## leonheart (Mar 2, 2011)

And if we use a CVT transmission, the situation could be better?


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## michaeljayclark (Apr 3, 2008)

would love to use a CVT transmission but getting a CVT to match up to motors and operate without a transmission computer is a very hard bargain. It has been done but with many hours of R&D.

the motor cant run at just 3.42 ratio. the rpms would be too low. motors getting 600 amps at low rpm = death.

Ive been explained to compare the amount of work when the rpm too low technically but I just say the rule of thumb is to not have max amps to far below 100 rpm. thats why we just dont hook the motor to the rear end. unless youy are running drag races, then trashing a motor to go fast is just fun!


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## DavidDymaxion (Dec 1, 2008)

I look at it this way, I woudln't want to run my car at redline for an hour a day, run at its top speed for hours, or continuously ride the brakes down a hill. Yeah, it's designed to hit redline, top speed, or brake hard briefly, but I doubt designed for continuous redline duty. Likewise I generally wouldn't want to run the driveshaft at its max rpm continuously. Remember the forces go as the square of the rotational speed, so if you are running twice as fast that's four times the forces.

Let's look at a particular case. A 3.0 ratio Ford 9 inch has the driveshaft spinning around 3000 rpm at freeway speeds. If you jump to a 6.5 ratio, it's now spinning, continuously, 6500 rpm at freeway speed. Use this in a car with smaller wheels and a high rpm motor, and you could be spinning it at 7000+ rpm at regular freeway speeds. It might also be an argument for using a racing driveshaft.

The main message is if you are worried about running a driveshaft at or above its max speed, then that's yet another argument for using a tranny over a super low rear gear.

One minor correction, maximum driveshaft speed is set by the maximum vehicle speed for most cars. For the Porsche 924/944/928/Newer Corvette it is set by maximum engine speed, as the driveshaft feeds the tranny input shaft, as the tranny is in the rear.


Duncan said:


> Hi David
> 
> If you fit a higher ratio diff you increase the drive-shaft speed.
> However you only increase its average speed - its maximum speed is set by the motor maximum speed
> ...


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## michaeljayclark (Apr 3, 2008)

this makes me wonder how you would have an ac system with a 12000 rpm motor and a drive shaft. 

here's an interesting driveshaft speed calculator

http://www.wallaceracing.com/driveshaftspeed.htm#modulus

looks like the shorter the shaft the more rpm it can handle.

a 20 inch driveshaft, 3.5 inch outside diameter, material thickness .110 handles 63858 rpm! LOL, 12 inch can handle 177385 rpm


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## GrapeApe (Feb 5, 2011)

My battery drill has a 2 speed selector on top. I can use #2 to drive screws until the battery goes so low that it just stops. Then I can switch to #1 gear reduction and drive 20-30 more deck screws. 

So gear reduction in an electric car can do the same thing as a gas car. It can reduce the power draw needed for take off and increase drive time, not to mention create less heat at lower speeds. You'll use much less juice and take off a tad swifter at the same time. 

I would suggest a_ auxiliary underdrive _unit with electric shift, but I think you need to disengage the clutch to shift. You could make the adapter plate to fit the auxiliary unit just as well as the tranny and input spline. But how to disengage the power while the electric shift is completed is the problem. Maybe putting a clutch bell housing right to the auxiliary unit... hmmmm. I'll have to check into the bolt patterns. Aux tranny's are extremly light and even with a bell housing and clutch set up, it would still be a lightweight add on compared to direct drive. 

As for the high end of the speedometer, Chevy made a 2:08 rear end that would prolly launch your Hoopty over 1 MPH. Check with your local rear end re-builder for available options for your car. then you could have a low gear for 0-50 and one for getting speeding tickets 

But my question is 'can you use automatic tranny's??' I would think you need constant RPM's to run the front pump. I heard someone say 'Powerglide'? When the engine is running, the pump is turning also; at least 500RPM's. If the electric motor stops, how does this effect the tranny? Like you cant tow a car with auto tranny with the wheels on the ground, because it blows all the seals inside the tranny as only the rear pump is turning. How is this overcome?


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## DawidvC (Feb 14, 2010)

GrapeApe said:


> But my question is 'can you use automatic tranny's??' I would think you need constant RPM's to run the front pump. I heard someone say 'Powerglide'? When the engine is running, the pump is turning also; at least 500RPM's. If the electric motor stops, how does this effect the tranny? Like you cant tow a car with auto tranny with the wheels on the ground, because it blows all the seals inside the tranny as only the rear pump is turning. How is this overcome?


There are some people who modify auto trannies for ev's. It seems a bit expensive at this point. The Powerglide I have seen does not have an ideal ratio, as a first gear of about 3.0:1 seems a good compromise for an ev, based on the number of people running in 2nd and 3rd gear in their conversions. In general, I would think, the more powerful your motor the less need there is for a tranny.

Dawid


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## michaeljayclark (Apr 3, 2008)

Kansas EV has modified a powerglide with auxiliary pumps to keep the pressure up on the tranny.

http://www.kansasev.com/evglide-powertrain.html

the pump puts fluid pressure through the back and front.

Ive played with all the numbers to try and figure out the best gear ratio to have the best RPMs on the electric motor.

The 11 inch motors can be run 1:1 without an issue, they have more commutator bars to handle the amperage put through with the lower rpm. ONLY issue with less commutator bars available to transfer current, the MORE amperage it takes to take off. More Amps used to launch the vehicle, the less range you get. Major peukart effect in da house!

this may not be the exact technical reason but its how I understand it and an easy way to understand it.


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## JRP3 (Mar 7, 2008)

Not exactly. Brush area and cooling are what dictate your current carrying capability. If you run high amps at low RPM's your motor doesn't cool down enough with the internal fan. That's why people add external cooling blowers and look for motors with a large brush contact area.


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## michaeljayclark (Apr 3, 2008)

ok, Ill add cooling fan speed to my explanation to why a motor will not like and die when too much amperage is applied at lower RPM. more amperage equals more heat basically.

A blower motor would make an excellent blower to force air on the commutator at low RPMs.

I knew I was close on the technicals!


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## LithiumaniacsEVRacing (Oct 9, 2010)

Not sure if this company was posted, here it is:

http://www.gearvendors.com/racing.html


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## leonheart (Mar 2, 2011)

Is there, in the forum, someone who use a gearbox in his EV?


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## michaeljayclark (Apr 3, 2008)

I think everyone is waiting till someone tries it out before they get one.


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## DavidDymaxion (Dec 1, 2008)

I have the original transmission in my EV.


leonheart said:


> Is there, in the forum, someone who use a gearbox in his EV?


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## michaeljayclark (Apr 3, 2008)

another reason not adding a gearbox is its just easier to use the original transmission and use the existing mounts.

I still want a gear box that could attach to the motor like the tranny but be lighter and more efficient. could also be placed back near the rear end for a shorter drive shaft.


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## leonheart (Mar 2, 2011)

michaeljayclark said:


> another reason not adding a gearbox is its just easier to use the original transmission and use the existing mounts.
> 
> I still want a gear box that could attach to the motor like the tranny but be lighter and more efficient. could also be placed back near the rear end for a shorter drive shaft.


Yes, I know, but that ratios I think are too short for the EMotor Torque. So, technically, the first and maybe the second gear are useless, and the longer ratios guarantee a low Topspeed enough.
Now, nobody tried to change the final transmission like I suggested some posts ago?


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## DawidvC (Feb 14, 2010)

leonheart said:


> Now, nobody tried to change the final transmission like I suggested some posts ago?


If we look at the experiences of the Ev racers, it seems as if accepted wisdom regarding correct ratios for ICE cars does not work with ev's. Using Franky's EV calculator and playing around with rear-end and gearbox ratios, it seems as if a two-speed box with 4:1 to 3:1 diff is suitable for a small car. The real suitability of any combination of gearbox/diff ratios will need to be established for each build, as the pack voltage, controller and motor used, also hugely influence what is achievable with a certain combination, when keeping the donor constant. Even changing battery type can have a large influence.

It seems to me that there cannot be a single "BEST" answer. What is needed is a tool to allow us to make a more informed choice, like the ev calculator, but expanded to take into acount controller type, driving style etc. That can help us make a more infomed choice.

Dawid


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## michaeljayclark (Apr 3, 2008)

that could be very possible. what the calculator says vs real life scenarios isnt always the same, they can be close, but not exact.

Ive put forth the idea that a final 6.2 ratio is the best to handle a single speed with enough range to handle an EV. But then if you look at efficiency of the motor you can see that the upper RPMs not only lose torque they lose efficiency.

the upper end of a single speed transmission for a DC motor will start losing torque AND start fighting the 50 mph wind created by going 50 mph.

AC is another story, a 12000 rpm motor is right at 161 at 12000 rpm. 

this ios another try it out scenario and I will try it. we are using ICE transmissions and they all work well, so making a single speed or two speed tranny at 1.81 first gear (which the powerglide has) works fine and my idea here is to make a 1.81 gear ratio single speed tranny to work with my rear end in my gmc jimmy.

for now until i can make the singlespoeed gearbox iull just use the existing tranny which is a 4L60E automatic.. will be interesting to use it to get it working.

they tell me with no computer hooked to the transmission it goies into emergency mode, which is 2nd, 3rd, park, and reverse. the EXACT gears I need! and a now 2 speed transmission! well see how it works!


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## DawidvC (Feb 14, 2010)

I remember seeing a 2-speed gearbox integrated into a diff. I was looking for epicyclic gears and google popped this up. It seems to be an interesting idea, and it is also very compact. Wish I could remember more details but it seems to have disappeared in the meantime. It would be useful for conversions - If the motor can fit under the backseat of a rwd car, yuo can have the whole engine bay for batteries 

Dawid


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## Guest (Mar 11, 2011)

Ever consider a marine Velvet Drive Transmission? Forward - neutral - reverse. Quiet, simple very well built and come in many different ratios. Plenty of them on ebay for under $1k. Small form factor too. The provide a safety factor because you can disengage if needed and you have a mechanical reverse. Provide water cooling and your good to go. I am quite sure you could adapt an electric motor directly to them. 

Just a thought.


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## michaeljayclark (Apr 3, 2008)

looking at powerglidses and how popular they still are, this transmission will do the job until a single speed easy gear to gear gearbox is made. Ill just use a powerglide in my ev then upgrade later, I want to get on the road asap! lol


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## Guest (Mar 11, 2011)

The velvet drives are simpler than the powerglide and you don't need a torque converter. They should mount up nicely in your car. Smaller too. The powerglide is however a good transmission for a simple automatic. 

Pete


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## michaeljayclark (Apr 3, 2008)

just looked and i think we found our winner! nice single speed transmission with reverse as well. even better, no reversing contactor. I see them on ebay around 500 dollars.

Ill have to check with local boat shops that sell used parts.


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## Guest (Mar 11, 2011)

Got a link so we can see? Or clip a pic and post a pic.  Specs too would be great.


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## michaeljayclark (Apr 3, 2008)

just checked craigslist. lots of boats in florida! found a person in naples selling a bunch of velvet drives and may even have the 1.81 gear ratio I need. $200.00

would be nice to try out.


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## michaeljayclark (Apr 3, 2008)

founbd a local person that can sell me a 1.91 ratio for $200. on my way out to take a look at how we can match these up as the single speed transmission.


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## Jimdear2 (Oct 12, 2008)

This does sound like a very good alternative to a powerglide or other automatic for a RWD vehicle.

For a high rpm (10.000 / 12.000 rpm) A/C motor it should be the answer. For a limited rpm (3 to 4.000 rpm) DC system the choice may be to have either a 0 to 60 mph or 40 to 100 mph setup.

I had a friend who used this transmission in a small pulling tractor and it worked well until the input rpm dropped to a point where the pump would not keep the clutch engaged, then poof. 

I looks like cooling is very very important.

Like the powerglide and most other planetary type automatics, the internal woking pressure is supplied by a pump driven by the input shaft. So if the motor stops turning the the clutch packs will open. When you start moving again the pressure has to come up and reapply the clutch. This could be a noticable pause and jerk or if power is brought up gradually the clutches would slip and eventually wear.

It does appear that this trans will need some form of eternal pump to keep the clutch applied whan the motor is not turning ot the rpm is low. 

The problem I see, is, if you try to idle the motor to keep the pressure up something has to slip, In an automatic, it's the torque converter in a boat the trans is in neutral and when in gear the prop acts like a torque converter. 

The answer of course is to install an external electric pump to keep the clutch engaged

The other thing is unlike the powerglide there is no park position, although that is easily overcome.


*EDIT*

A thought, the V drive models offer some interesting motor mount possibilities.


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## michaeljayclark (Apr 3, 2008)

picked it up for $200. Im also getting a powerglide as well, will see how both work out. The cost of the two items is covered by the 4L60E 4x4 transmission and the transaxle.

Its an even trade. Im getting the powerglide for $180. its a complete glide with torque converter. it may need a rebuild, thats about $100 for all new parts. Id like to know how to rebuild a small transmission like the powerglide anyway.


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## Jimdear2 (Oct 12, 2008)

michaeljayclark said:


> picked it up for $200. Im also getting a powerglide as well, will see how both work out. The cost of the two items is covered by the 4L60E 4x4 transmission and the transaxle.
> 
> Its an even trade. Im getting the powerglide for $180. its a complete glide with torque converter. it may need a rebuild, thats about $100 for all new parts. Id like to know how to rebuild a small transmission like the powerglide anyway.


 
Mike,

Good job!!!

There are several good books on working on / modifying powerglides. It's worth the few bucks investment.

If your going to overhaul, get one of the high performance kits. Again a few bucks more but worth it.

I'll be watching. . .

Jim


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## michaeljayclark (Apr 3, 2008)

found a complete aluminum case powerglide. the tranny is still in the original car. looked at the fluid and itrs pretty pink, too pink I think but like I said, trannys old and unused probably need an overhaul. the idea of upgrading it with a little more performance cant hurt anyway. the powerglide was $150.

the aluminum powerglide has 1st at 1.81 second 1:1, the exact ratio i was looking for. its the lighter duty cheaper one but i am sure it will handle the electric motor with the soliton jr.

as far as the original purpose for this thread, i think the powerglide is the EV transmission. If I had the money and we all say that, I would start producing them for ev use. the patent is expired by now.

thats for DC , as far as ac like tesla, a single speed tranny is all that is needed


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## Bags (Jun 20, 2010)

FWIW, my car uses direct drive with a Gear Vendors 0.76:1 overdrive.

www.evalbum.com/120


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## DawidvC (Feb 14, 2010)

gottdi said:


> Ever consider a marine Velvet Drive Transmission? Forward - neutral - reverse. Quiet, simple very well built and come in many different ratios. Plenty of them on ebay for under $1k. Small form factor too. The provide a safety factor because you can disengage if needed and you have a mechanical reverse. Provide water cooling and your good to go. I am quite sure you could adapt an electric motor directly to them.
> 
> Just a thought.


I just had a look at their website http://www.velvetdrive.com/

They have a nice selection of ratio's. I was thinking that the 2 speed box (T72) with 2.8 and 1:1 ratio and reverse will be handy. It will suit ev's better than the 1.81 ratio of the PowerGlide. It would be interesting if you could get the box with adaptor plate and female splines - It would make installation relatively painless, and, like the EVGlige, allow you to mount motor and gearbox in the gearbox tunnel, keeping the engine bay open for controller, batteries and other accessories. 

Nice find, Gottdi. It is a pity they don't have prices on their website, though.

Dawid


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## Harold in CR (Sep 8, 2008)

Ebay has 3 pages of Velvet Drives, and spring loaded dampers, and splined adapters, manuals, etc.


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## GrapeApe (Feb 5, 2011)

michaeljayclark said:


> The powerglide has 1st at 1.81 second 1:1, the exact ratio I was looking for. It's the lighter duty cheaper one but I am sure...
> Aas far as the original purpose for this thread, i think the powerglide is the EV transmission.




 I wholeheartedly agree, for the auto trans selection. My first car being a '65 GTO with a PG, I'm not biased at all  When I got on Interstate 5 here, I had no shortage of power up the ramp and would hit 70MPH (113km/h) before shifting to high gear.

PG's came in a few grades. Light duty can work well in a small or mid sized car... remember even the Corvair van/pu had a powerglide 

Double check the GVW of the vehicle the tranny was pulled from. Wikipedia has a good written history and will tell you the 'bad' years from the upgraded years that were highly successful. I pulled a number of trailers without failure with my '65 GTO. These tranny's were used in race cars and pickups alike, so a car will not be a problem as long as you find the better years for duty service.

 
There are a couple of other points people have made that I would like to expand on. 

Don't forget that the tire diameter on hte drive axle is part of the final drive formula. I see much talk of 1:1 and diff. gears. I learned this early when I put some fat 50 series wheels and tires on a 1950 Chevy pickup and the top speed dropped 50 MPH real fast! lol. The original tires were 30+ inches, not 26 :/ Most vehicles have had tires *other* than what the factory installed. Double check the door sticker or the handbook if you can find one. Tire shops can provide this information. 

As for stick vs. auto... I saw a comment like, sliding the clutch, or something like that. Well, with an electric motor, you would not start with the clutch disengaged anyway. You would not have your foot on the clutch unless you wanted ot to shift while under way and if you use a vehicles factory manual transmission, it would be a pretty light alloy box so weight is not a problem. The 4 spd tranny in my Datsun is only about 75 pounds. I lift the spare around the shop sometimes to get it out of my way lol. 

Another thing about the 4 spd (or 5 spd o.d.) tranny is that you wouldn't need to shift it more than once in most situations. taking off from the driveway would be a 2nd to 4th shift and leave it there until you stopped again. even 3rd or 4th might be used. starting when your car is already pointed down the freeway off ramp will be in 4th gear as you are using gravity for most of the start up anyway. When you go to the fav fishing spot in the hills or up a mountain road, 1st gear might be warranted. I'd like 1st gear to pull a buddy or stranded motorist out of the ditch and have more control than trying to control all that torque in a *direct drive only* situation. Hey, there's a sales pitch for you... "You've just been returned to the road by an all electric vehicle" hahaha 

As to the original question. "Why don't use a Multispeed Gearbox...", all I can say, is .... I intend to do just that because as a trucker for 30 years, I do understand that I will not always be driving in the flat lands with expected terrains. I want to drive my car to the high country and expect to tow a heavy trailer to the scrap yard and other "call of duty" situations in the life of my EV


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## michaeljayclark (Apr 3, 2008)

I picked up a velvet drive as well, 1.9:1 ration. VERY sturdy gearbox! weighs 100 pounds easily.

I think if I put a 1:1 gearbox after the velvet drive, I could start out with 1.91 VD then "shift" to the 1:1 gearbox by placing the 1.91 VD in neutral. I bet the VD can be shifted from drive to neutral on the fly. I bet the VD could go from drive to reverse on the fly and the driveshaft would snap and the VD would laugh lol

if i had the mythbusters budget I would definitely try it!

as far as mounting the motor to the VD thats easy, is has the same spline as an engine, I got the pressure plate as well, fits onto the spline nicely.


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## JRP3 (Mar 7, 2008)

If the VD is in neutral how would it drive the 1:1 gearbox?


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## michaeljayclark (Apr 3, 2008)

just though of that! would have to be a belt system... the belt connected to both drives, when one is in drive other in neutral, etc... i was thinking on step ahead of myself. 

gets a little complicated! so one drive, a 1.91 ratio would work for a single speed tranny and the vel;vet drive fits the bill. linear and strong enough to fit the bill. also canm be found on the secondary market at a reasonalbe cost.

if you want new, then this would work as well. very strong and able to handle as a single speed tranny.

http://www.redex-andantex.com/application.php?application=6


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## TomA (Mar 26, 2009)

Am I missing something here?

These velvet drives appear to be one-speed reduction gear boxes. That's OK, but doesn't solve the problem. A quick look at the spec sheets shows these all have pretty modest power ratings- particularly on bottom end torque, which is just the opposite of what they're going to encounter in an EV.

Our duty cycle is "max torque at no RPM" which is akin to a locked propeller on a marine drive, and lots of driveline shock at other speeds- more than the prop dropping in and out of the water, for sure; all of which I'll bet the mfr never intended these units to see.

They're also heavy; more than a 2 speed Powerglide. Velvet has a 2 speed transmission with reverse, intended for low speed work vehicles, but its cast iron and 275lbs. 

I just don't get how these boat drives solve the need for 2 speeds, or are worth the trouble to fool around with.

If you just want a reduction/overdrive unit, these boat drives seem heavy and complex. Here's a lighter, probably stronger planetary one, and it can be switched from Hi to Lo, though probably not while in motion:

http://www.northwestfab.com/blackbox.html

Anyway, am I missing something, or is there no there there?

TomA


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## JRP3 (Mar 7, 2008)

The VD's allow a gear reduction and a mechanical reverse. I agree they aren't ideal and you'd probably be better off with a transmission.


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## TomA (Mar 26, 2009)

JRP3 said:


> The VD's allow a gear reduction and a mechanical reverse.


If you are running AC, (presumably to take advantage of the single speed capability of these motors,) then you don't need reverse. Since any differential is going to give you a reduced and probably selectable final drive ratio, I don't see what VD provides beyond neutral, which an AC motor shouldn't need (because of the very low chance of failure in runaway full throttle mode.)

If you're running DC, a single speed really won't do, so the reverse and neutral (which BTW may not be selectable under full power, i.e. as an emergency disconnect) aren't important if the gearbox can't give you at least two ratios.

Not to mince words, JRP, but where do these VDs make any sense at all?

TomA


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## JRP3 (Mar 7, 2008)

Probably not anywhere really, but, if you are doing DC with a large enough motor in a light enough vehicle to do direct drive, but your differential doesn't give you low enough gearing, and you don't want to deal with expensive reversing contactors, and you can grab a cheap used VD, then maybe it might make sense. That's a lot of if's, but's, and maybe's.


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## michaeljayclark (Apr 3, 2008)

$1600 for a strong planetary gearbox is pretty good. I like that gearbox.

I got a VD and you are right, it wouldnt make a very good transmission for an EV.

and saying I got a VD for my EV sounds wrong.....


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## FB Performance Trans (Dec 14, 2010)

leonheart said:


> Is there, in the forum, someone who use a gearbox in his EV?


There are many advantages to using a multi-speed gear box in an EV conversion that far out weigh the disadvantage of carrying the additional weight of the transmision especially if its a heavier type of vehicle. 

Please take a look at the following thread:
http://www.diyelectriccar.com/forums/showthread.php/automatic-solution-ev-conversions-53052.html


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## GrapeApe (Feb 5, 2011)

This all reminds me of my Trade School shop teacher that once said "Why is it, the engineers and factory developers can take years designing and years improving applications in harsh test conditions... then some high school kid with a year of auto shop and a flier he got in the mail comes along and thinks he can improve his vehicle with some $100 bolt on part like Black Jack Headers or a camshaft and make it run better?".

Food for thought


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## michaeljayclark (Apr 3, 2008)

sounds almost like some guy gets an aircraft starter motor buts it in a car with batteries and thinks he can drive an electric car.


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## Batterypoweredtoad (Feb 5, 2008)

GrapeApe said:


> This all reminds me of my Trade School shop teacher that once said "Why is it, the engineers and factory developers can take years designing and years improving applications in harsh test conditions... then some high school kid with a year of auto shop and a flier he got in the mail comes along and thinks he can improve his vehicle with some $100 bolt on part like Black Jack Headers or a camshaft and make it run better?".
> 
> Food for thought


The garage engineer is less constrained than the factory engineer. The factory engineer has to balance performance, emissions, packaging, durability, ease of assembly, comfort, and often most importantly cost. The garage engineer can sacrifice one or many of those variables to get more of the variables more important to him/her.


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## FB Performance Trans (Dec 14, 2010)

Batterypoweredtoad said:


> The garage engineer is less constrained than the factory engineer. The factory engineer has to balance performance, emissions, packaging, durability, ease of assembly, comfort, and often most importantly cost. The garage engineer can sacrifice one or many of those variables to get more of the variables more important to him/her.


Good Observation!

Using the term “garage engineer” is very generous. I could be wrong, but I think in that respect the word engineer is being used very loosely. As I’ve mentioned before on this forum, the Do-it-Yourselfer certainly has a lot more latitude when it comes to accepting the quality of the finished project. 

Obviously there’s a big difference when you’re building and fabricating something like this for yourself versus being contracted to do it for someone else. An individual inclined to do this on their own can more or less tolerate his own mistakes and the time (and money) necessary to get it done right. However, a customer will not share a similar tolerance if they’re paying for an engineered product if it doesn’t work properly. Most in business realize that you won’t often get a second opportunity, if your original “engineered” equipment doesn’t perform as quoted. We also believe that there’s an intrinsic value in achieving a solid reputation for providing quality equipment.


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## leonheart (Mar 2, 2011)

I know that at this point I'm Off Topic but I found an interessing video about this discussion.
I post it because design my original idea, the idea that I had when I opened this topic. 

http://www.youtube.com/watch?v=pBMxynSFaok&feature=related

Look at the description of the video, there's a little comment about this realization


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## Woodsmith (Jun 5, 2008)

Before we all start a new debate on transmissions....

This is an old thread.


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## major (Apr 4, 2008)

Woodsmith said:


> Before we all start a new debate on transmissions....
> 
> This is an old thread.


Hey Woody,

You moved a post here a few days ago. It appears that fellow has deleted it. I think it contained a link. Any chance you have that link? 

Thanks, 

major


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