# manual transmission in an electric car



## sgtlethargic (Sep 17, 2010)

How does the use of a manual transmission in an EV differ from an ICEV?

Thanks,
Kurt


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## racunniff (Jan 14, 2009)

sgtlethargic said:


> How does the use of a manual transmission in an EV differ from an ICEV?
> 
> Thanks,
> Kurt


Several, mostly minor, ways:



The peak HP of your electric motor is usually at a different RPM than the peak HP of your ICE. This means your shift points will be different. For example, on the volt914, I can stay in 1st gear until 40 MPH+ and then shift directly into 3rd
As the above implies, the low-end torque means you may not need some of your manual transmission gears. But they are expensive to remove, so most people leave all of them.
If you do not have regenerative braking, the motor will tend to continue to spin at full RPM when you push the clutch in - even if you are not applying throttle. This can make it difficult to down-shift in many cars
Other than that, the main mechanical points are the same, and, in fact, people strive to maintain the same tolerances and alignments with an EV that they had with the ICE.


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## Coley (Jul 26, 2007)

If you go clutchless, the time to shift gears is a tad longer.

Since the speed range is good for 2nd or 3rd gear, you don't need to shift at all.

If you are in stop and go traffic, again not much shifting.

With a clutch, you just shift as usual, but not as often either.


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## sgtlethargic (Sep 17, 2010)

Are manual transmissions, especially say a 5-speed with overdrive, not as advantageous in an EV? I don't have a feel for the different parameters like batteries, motors, and such, but I'd think that something in the EV system could be _smaller_ by taking advantage of a transmission.

Thanks,
Kurt


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## Anaerin (Feb 4, 2009)

sgtlethargic said:


> Are manual transmissions, especially say a 5-speed with overdrive, not as advantageous in an EV? I don't have a feel for the different parameters like batteries, motors, and such, but I'd think that something in the EV system could be _smaller_ by taking advantage of a transmission.


ICEs have a minimum RPM speed of 700-1000RPM, and a "Power band" of 3000-5500RPM (typically).

Electric motors have a minimum RPM speed of 0RPM, and a "Power Band" of 0-6000RPM.

Given that an Electric motor doesn't need to idle, there is no need for a clutch (no need to speed match between an idling engine and a stationary gearbox). Also, as an Electric motor has such a wide power band, there is no (well, considerably less) need to change gears to keep the engine within it's power band, as it's always within it. 

The only issue you will have is balancing torque and speed, ensuring that you have enough torque to accelerate the car, while keeping your required top speed attainable.

If you have a Electric motor that puts out enough torque, it is quite possible to directly couple it to the differential, bypassing the gearbox entirely, but this usually isn't done because it's more difficult to get the correct ratio in a differential than it is in a gearbox, which is already provided with the vehicle. So, as an alternative, most converters attach the Electric motor to the gearbox, place the gearbox in an appropriate gear (2nd or 3rd), and leave it there. Some even go to the lengths of removing the other gears from the gearbox itself to lighten the weight and decrease the rotating mass.


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## Woodsmith (Jun 5, 2008)

The other difference, from what I have gathered, is that with an ICE you would try to keep the rpm low for economy so you would use 5th gear with the ICE at, say, 1500-2000rpm.
With and EV economy comes at the top end of the rpm so you may leave the transmission in 3rd and cruise at 5000-6000rpm.

Apart from not overspeeding the motor on down hill coasting higher gears are not that useful.

What gears you would use would also depend on what sorts of speed you would require most of your driving to be at.


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## Coley (Jul 26, 2007)

As my battery pack has gotten better, I find myself using 4th and 5th gears
for highway driving.

3rd is used around town most of the time,to 40 mph.

I find that having a 5 speed is a good thing.

When I go out in the field to build fence, 2nd gear is great for rough, uneven ground. You can creep around well.

1st gear is hardly ever used.

I know, who builds fence with an EV? Well, I built mine to do any job that I need it for.


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## lou-ace (Jul 21, 2009)

without a clutch in the manual transmisssion, it's been my experience that up shifting is rather easy, as the syncros will match gear ratios. Where you may have trouble is in down shifting. Most manual transmissions will need a "tap" on the accellerator ( motor controll), to speed up the primary gear ring to match up the syncro's and avoid grinding gears. think of double clutching an ICE, not to difficult but, you will need to learn the new driving skill to avoid damaging the tranny. good luck


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## Frank (Dec 6, 2008)

Assuming an air-cooled motor, you don't want to lug it i.e. use too high a gear. Most motors have an internal cooling fan and not spinning them fast enough will make them overheat. They *do* make max torque at low speed but excessive lugging is bad. A transmission helps here.

Of course you don't want to over-speed them and exceed the mechanical strength of the commutator. Like a lot of folks I generally use 2nd and 3rd gears in my conversion.


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## alelogman (Nov 3, 2010)

lou-ace said:


> ...think of double clutching an ICE, not to difficult but, you will need to learn the new driving skill to avoid damaging the used manual transmission. good luck


It took sometime for me to learn that skill but still not too confident.


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## Guest (Nov 6, 2010)

Keep the clutch, trust me, you will be glad you did. The extra weight is no big deal on a street driven car. 


Just because you can (go clutchless), does not mean you should.


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## EVfun (Mar 14, 2010)

Just to submit the counter opinion, I prefer clutchless, so long as you are not racing. By using a small diameter and light coupler between the motor and tranny shifting is not at all difficult in most gear boxes. I don't find shifting to be difficult, just a little slower (trying to shift and EV clutchless that has the clutch is A LOT slower.)

You don't have the motor, flywheel, and clutch kicking your car in the butt when you try to release the clutch after a shift. That after shift release is very different in an EV with a clutch compared to an ICE vehicle when the motor has slowed back to near idle. Another plus, you don't have a clutch to start slipping. A series motor can make a lot more torque than a stock small 4 banger. I also find balance is easier with a light and small diameter shaft coupler. 

That buggy in my avatar has been a clutchless EV for 11 years now. To each his own Gottdi.


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## DavidDymaxion (Dec 1, 2008)

It also depends hugely on the car. How easily it shifts clutchless as an ICE will give you a clue. I drove an electric bug, it shifted easily without the clutch. Myself and others have found the Porsche 911 to be very hard to shift clutchless. A 1965 Mustang I drove shifted as easily clutchless as with the clutch, but a newer Camaro was difficult to reliably shift without grinding without the clutch, despite my considerable rev-matching skills.

Something else is your drive. If you drive the flatlands neighborhoods and the city in 2nd gear, and do a single shift once a drive to 3rd getting onto the freeway, a couple of seconds is no big deal. When you are on a steep hill and traffic is approaching and you are trying to shift to move with the traffic, that 2 seconds is going to seem like an eternity. That's definitely the scenario where I live (home of the 2002 Winter Olympics), so I figure the clutch is a safety factor for me.

Not applicable to most folks, but keeping the clutch saved me $4500. I have old-school sepex. I can idle the motor and slip the clutch to take off with a simple, home built 2000A $500 controller, rather than have to buy a $5000 Zilla 2k.


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## JRP3 (Mar 7, 2008)

In my AC motor setup with regen I find that up shifting can be faster than with a clutch, but since the regen slows the motor immediately you have a very narrow window to make the shift correctly. Downshifting is very difficult. Luckily with the high RPM's and fairly flat torque band of the AC motor I don't really need to shift. 99% of my driving is in second gear, from 0-65 mph at 6500 RPM, and running at higher RPMs keeps the fan spinning faster. If I had a more powerful controller that allowed 700 amps and 156+ volts I could easily run a single speed gear reduction equal to second gear and bump my max RPMs to 8K. Someday.....


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## Guest (Nov 6, 2010)

It's a personel preference but not one taken lightly. Manual transmissions were designed for one. They are not built to be shifted with out one. Motor choice makes no difference. If you never shift I guess it's fine. There is not difference in shifting an electric vs gas. 

Pete 

Weight makes no difference either. You see, most just stuff the car with lead and it does just fine. So a few pounds of flywheel make no difference. It does not make any difference to the motor either unless your Racing and need that 1/100th of a second lead to win. Then I'd say ditch the clutch and use one gear. If you need two speeds use a clutch not matter what application. 

Personal preference? Yes
Wise Choice? Yes


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## Guest (Nov 6, 2010)

By the way, my Ghia shifted like crap clutchless and the transmission shifted smooth as silk with it. The transmission was designed to use one. That is not a personal preference. It's a fact.


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## JRP3 (Mar 7, 2008)

It's true that some transmission shift more easily than others. I disagree that motor choice makes no difference and that there is no difference between shifting an ICE or an EV, there is a huge difference. Shifting is necessitated by the need to idle and the narrow power band with an ICE. Put in an electric motor with a wide enough power band and shifting becomes unnecessary. Truth is I never need to shift in my car but sometimes it's fun to use first.


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## EVfun (Mar 14, 2010)

gottdi said:


> By the way, my Ghia shifted like crap clutchless and the transmission shifted smooth as silk with it. The transmission was designed to use one. That is not a personal preference. It's a fact.


I think I'm using about the same transaxle in the buggy. Upshifts are with less than 1 second delay, backing down the gears would take about 2 seconds each if I didn't blip the throttle. Since I really only need to shift up once for freeway speeds it's no big deal, even though I'm 2 traffic lights away from 3 freeway onramps. 

My old Datsun will shift without the clutch with about a 2 second delay, that is with the full weight stock flywheel and clutch adding inertia for the syncros to deal with. I'm actually sorry I left it in.

An electric motor with no power applied to it (or being removed from it) is free spinning just like a clutch disc. The catch is, it packs a larger inertial punch. I hear some gearboxes really don't like that, but I don't know which ones.


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## Guest (Nov 6, 2010)

The act of shifting is no different. I have been driving VW's since 76. With my 96 Volt system using the transmission is required. I don't really need 1st but I use it. There is no excess strain on the clutch when I shift. The motor is not under load when I let off the clutch from shifting. I don't throttle until I have completed the shift which is faster than doing it clutchless. I don't throttle with no load. I have found it much more difficult to shift smoothly and consistently without the clutch than with. Maybe having a solid shaft connected to the transmission makes a difference vs trying to learn clutchless shifting with the clutch in the car. But even so I'd rather have what the factory intended the transmission to have. So with or without is truly a personal choice. But again, one which I did not take lightly and weighed all the pros and cons and the pros for the clutch won out. It is simple and easy.


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## EVfun (Mar 14, 2010)

gottdi said:


> Maybe having a solid shaft connected to the transmission makes a difference vs trying to learn clutchless shifting with the clutch in the car. But even so I'd rather have what the factory intended the transmission to have.


It certainly does! When you push the clutch in on your car (gas or electric) you disconnect the motor, flywheel, and pressure plate from the transmission. This leaves a free spinning clutch disc, input shaft, and some gears for the syncros to speed match in order to drop into the next gear. On an EV without a clutch the syncros have to match speed to the coupler and motor armature, which are free wheeling in place of the clutch disc. It certainly weighs a lot more, but the the diameter should be smaller. The inertia to overcome is based on mass and velocity. Something 2.5 inches from the center of rotation is moving slower than something 4 inches away. If you try to shift clutchless while retaining the flywheel and pressure plate it will be a lot harder with all the added fast moving mass. Smaller motors and smaller and lighter shaft couplers should also make clutchless shifting easier. 

That is what amazes me about my old Datsun gearbox. I didn't even lighten the flywheel and it's heavy. Of course no one could tell me if that gearbox could handle an armature, but it is clear to me now that it easily could. It takes about 2 seconds to shift clutchless with 1 finger on the shifter.

One last tip to good shifting, don't put GL-5 gear oil in a tranny that specifies GL-4. It makes it tough for the syncros to do their job unless they where designed for extra slippery stuff. Personally I use Redline MTL, a synthetic 70w80 wt GL-4 gear oil.


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## Guest (Nov 7, 2010)

Actually it was not what I was referring. With a motor direct coupled to the shaft or the motor coupled via the clutch but not using the clutch. In other words with a clutch in the car I shift without it vs shifting with a direct coupled setup. Is there a difference? I know the process of shifting without a clutch, I just wanted to know if leaving the clutch in and shifting to practice is different than a direct coupled setup and shifting that way? 

My tranny shifts like garbage with a clutch but shifting with out using it. Should work the same. Shifted like garbage with out it using the gas engine too.


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## EVfun (Mar 14, 2010)

Oh yes, Gottdi. It is a lot harder to shift an EV clutchless with the flywheel and clutch installed. The syncros have to get everything on the input side up or down to the speed of the next gear. The weight and diameter of the flywheel and pressure plate make this quite a bit more difficult. The motor armature is only about 5 inches in diameter so even though it is heavy it isn't moving that fast at 5000 rpm. The outside edge of the flywheel is hurling around at least twice as fast.

Shifting an ICE without a clutch is a completely different animal. You have to match speed between the engine and the next gear in the tranny with the throttle. With an EV the motor side is freewheeling. 

With my buggy or even the Datsun I can just release the throttle and shift up a gear. There is a slight delay before it drops into the next gear. If the flywheel is still there the delay will be longer and you will have to push harder. People often ask at shows about the missing clutch pedal. I tell them that when I release the throttle the electric motor freewheels, like when you release the clutch. That is why the clutch isn't needed to shift, and since I have full torque at 0 rpm I don't need a clutch to take off, so I got rid of it. 

I have to say that I haven't seen any off-the-shelf adapter clutchless adapter kits that I really like. It worked well for me because I was having my adapter locally made anyway. When doing it from scratch I find clutchless easier, but it certainly would be even easier (and about the same price) to just buy a good adapter kit.


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## eliseo8forem (Nov 13, 2010)

I know about EV.
At the present time AC motors are most commonly found in commercially built EVs, as they require more sophisticated and complex control systems than DC motors. AC control systems for hobbyist conversions are on the horizon, and will likely become available within the next year or two.


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## JRP3 (Mar 7, 2008)

Um, you mean like the AC motor in my conversion?


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## Guest (Nov 13, 2010)

Um, Yeah, like that. Didn't you know yours will be available in the next couple years? Bummer.


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