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Manual vs automatic transmission

44K views 35 replies 15 participants last post by  gracestevens 
#1 ·
I just read a post that talked about a 5 speed manual transmission but only using 2nd gear.
Can someone give some clarity for me please? Why is the manual preferred over automatic?
Additionally, explain why only 1 or 2 gears are utilized and not all 3 or 4 or 5 gears used (depending on the tranny)?
Thanks so much for your responses!
 
#2 ·
In general having more gears is gonna get you better range and higher top speed.
If you know you will only be in town 0-45 mph( no interstate) then maybe "pinning to 2nd gear" would make sense.
You have about 0-5000 rpm's with most street motors so you can use your gear ratios to figure out what speed your gonna get from what gear.

Automatics are not as effecient and may require cooling and/or a cpu.

I like the idea of a manual trans with all gears available and the clutch operable.

Don
 
#32 ·
In general having more gears is gonna get you better range and higher top speed.
If you know you will only be in town 0-45 mph( no interstate) then maybe "pinning to 2nd gear" would make sense.
You have about 0-5000 rpm's with most street motors so you can use your gear ratios to figure out what speed your gonna get from what gear.

Automatics are not as effecient and may require cooling and/or a cpu.

I like the idea of a manual trans with all gears available and the clutch operable.

Don
Hi all, first-time/long-time -- I just have to ask: why hasn't anyone gone to a super-steep 5.71 type rear-end gear ratio for the "fun factor" of shifting all of the gears in a homebuilt EV?

Thanks!
 
#5 ·
So let's say I have a 144 volt system in an S-10 that has a 5 speed manual. What would be the highest usable gear on the highway? And before you respond, I'm not able to give all the variables that may affect your response due to being a newb. But thanks for responding so that I can take the info decide what I'll eventually do.
 
#7 ·
Gidday TJL!
I use 3rd gear for my highway driving (from around 35mph to 60mph). It keeps the electric motor spinning around 5000rpm at 60mph which is good for airflow inside the motor. Using 4th or 5th gear would mean the motor would spin slowly and considering you're using higher amps at high speed, you want the motor to stay cool, so the motor's internal fan spinning fast is a good idea.
 
#8 ·
Compared to an ICE, electric motors have higher Torque at low RPM's.
An ICE has to reach a high RPM rate before it has high Torque.

Electric motors also can run at higher RPM's safer than an ICE.

Most people don't run their ICE at 5000RPM in 3rd gear on the highway because that would destroy an ICE.

Electric motors on the other hand can handle much higher RPM's without problems and usually they draw a little less amperage at higher RPM's because they're using more voltage.(this is a good thing)

Thus electric vehicles can use 2nd gear for town driving (45mph and under) and 3rd gear for highway driving (around 65mph).

You could use 4th and 5th gears but your motor will be running at lower RPM's and drawing much more Amperage meaning the motor will heat up more, overdoing this can burn out the motor.

Also as Gavin said some motors have internal fans used to cool them, so the higher the RPM's on the motor the more they are being cooled.

Either way, it's a bonus because it means less shifting, usually you'll use 2nd and 3rd and that's it, unless you want to use 1st gear to show off your ICE butt kicking acceleration, or 4th gear to make the first electric vehicle high speed police chase. :rolleyes:

Also keeping the clutch in the manual transmission is good because it allows you to disengage the motor from the transmission in the case of a controller failure.
 
#9 ·
Thanks once again for a tremendously educational post :D!
I am assuming (please tell me I'm correct) that you're referring to a DC motor and not an AC?
Obviously trying to keep costs low, the DC is what I've been planning since getting "edumucated".
For a small pickup conversion, is there a motor recommended? I think the main thing I need to keep in mind is the climate. Being in Alberta, Canada I'm not sure that I'll necessarily need a "fanned" motor.
Again, thanks for the input!!!! I love the education I'm getting here! :)
Jerry
 
#10 ·
I have been reading on this topic on multiple sites as I am now beginning the task of building an EV. I have a 5 speed manual vehicle and have been arguing with myself over the clutch or not to clutch that is the question.

As gavin did, with his remoaval of his clutch it seems to simplify it a little, and it sounds like I won't ever need 4th and 5th gear. I am planning on leaving the clutch in, trying it and seeing if I like it, and if not, pulling the sucker out.

Unless I am missing something, this shouldn't be that difficult, except for the act of pulling the motor and everything out. Once you construct the engine mounting plate to the transmission, are you stuck? Do you have to make a new one depending on whether you have the clutch plates in our out? Is the connector between the motor and the transmission different if you have the clutch plate in?

Might this be an idea for you TJL?

As for the Automatic transmission, I have a friend who is a transmission expert and I am working no him to experiment. It was actually funny seeing his eyes light up and the gears begin to work (no pun intended) when I mentioned the problems of using an automatic transmission with an electric motor.
 
#11 ·
Thanks once again for a tremendously educational post :D!
I am assuming (please tell me I'm correct) that you're referring to a DC motor and not an AC?
Obviously trying to keep costs low, the DC is what I've been planning since getting "edumucated".
For a small pickup conversion, is there a motor recommended? I think the main thing I need to keep in mind is the climate. Being in Alberta, Canada I'm not sure that I'll necessarily need a "fanned" motor.
Again, thanks for the input!!!! I love the education I'm getting here! :)
Jerry
Yes I was talking about DC motors in my last post, but it also applies for AC motors too.

Usually AC motors run at even higher RPM's than DC's.

The AC55 motor from Azure Dynamics(formerly Solectria) can reach 8000 RPM's:
http://www.electroauto.com/catalog/acmotors.shtml

This would mean you could reach highway speeds in 2nd gear, though I'm not sure you'd want to.


To Headrush:
I'm not a transmission expert but I'm pretty sure you'd need to rebuild the adapter plate due to the space the clutch used to take up not being there.
Personally I don't think thats much of a problem and I doubt you'll care about the clutch once you build your EV.:rolleyes:
 
#12 ·
Headrush, it may be an idea except that I only vaguely have a clue to what you're talking about :). I just have enough knowledge right now to be dangerous!! :D
I just keep asking questions and inch along with my education and research until the day comes that I begin my conversion.
The one thing I do do :D, is cut and paste in my conversion file. Then try to review from time to time. I'm getting better but I know I need to purchase a book about it all. soon . . .
 
#13 ·
Guys, I'm no expert on anything, but for what it's worth, the clutch would be able to be removed without refabbing the adapter plate, assuming the plate is of the commonly used type (elec motor to trans bellhousing).

The clutch is attached to the flywheel and connects to the input shaft of the transmission. It sits in the bellhousing. Removing the clutch WOULD require you to fabricate an alternate means of connecting the flywheel (or motor shaft, if you removed the flywheel too) to the input shaft of the trans. Perhaps something that goes from the hub adapter to the trans splines.

This being said, it would probably be easiest to keep the clutch in there. Even if you didn't use it, I don't see any downsides to it being there. If you were going direct drive, I think you'd need a lot of motor torque. Plus, you lose reverse.

JMHO, John K.
 
#14 ·
If you look at Kwiev he decided to rip out his clutch and pedal and all. I am just wondering what ate the good and the bad of keeping or getting rid of the clutch.

I am no expert by any means. I am a 'computer guy' and have forgotten more about electronics than I like to admit. That and working with computers is a lot different than working with real electricity. I am learning as I go too . TJL, and that's probably why I ask some dumb questions. But we are all learning here and hopefully we can all learn from each other.

Here are a few books to get that have begun to help me:

Convert It!
Build Your Own Electric Vehicle
Electric Motors and Control Techniques
Electric Motors & Drives
 
#16 ·
My concern is that I am trying to build this car with the average driver in mind. My wife is all excited about this becoming her around town car. To that end, I would think a clutch will make her experience the same as any other manual transmission. When dealing with 2000+lb of car, I can't see where 20lb can make all that much difference.
 
#33 ·
My concern is that I am trying to build this car with the average driver in mind. My wife is all excited about this becoming her around town car. To that end, I would think a clutch will make her experience the same as any other manual transmission.
It would not really be the same experience. You use a clutch with an engine to allow the engine to keep turning at more than idle speed when starting off from a standstill. You don't want to do that with an electric motor.

The clutch is only used with an electric motor if you want to shift gears while moving, since you may trash the synchros trying to shift with the motor coupled to the input shaft.
 
#18 ·
I think that either way, there is going to be a relearning curve with driving an EV, with or without a clutch. A series wound motor with no load (i.e. clutch in) will spin up VERY fast and destroy itself. So, even if you keep the clutch, you have to be careful about pushing the "gas" pedal when you take off from a stop and when shifting gears because "slipping" the clutch will no longer be necessary and possibly dangerous. If you get rid of the clutch, the shifts are going to take longer because you have to wait on the gears to synch up and downshifting will be near impossible while moving.
Just my .02

James
 
#21 ·
Yeah, an ICE powered car requires a bit of a wait to "dry shift". I have done plenty of dry shifting in traffic, and it really sucks when you're trying to accelerate quickly. However, it is really helpful when you are using your right hand to shift, your left hand to hold your cel phone, and your left knee to steer. Oh, it's also nice when your clutch master has completely failed. :rolleyes:
ICE-powered cars have a flywheel that helps to make the motor smooth despite its tendency to produce individual pulses of power. An electric motor does not have this. Is this what makes a clutch-less manual-transmission EV possible? I know that the motor doesn't need to be spinning all the time, so the clutch is not needed for a standing start, but apart from that...
 
#25 ·
ICE-powered cars have a flywheel that helps to make the motor smooth despite its tendency to produce individual pulses of power.
Thats what the harmonic balancer is for.
You don't need a clutch in an ICE powered car either, you would just have to shut it off when you came to a stop and start it up in gear which would wear out your starter.
 
#23 ·
Headrush, thanks for the book recommendations. just purchased Build Your Own Electric Vehicle. Will certainly be gaining knowledge but will be needing questions answered. I'm sure you guys will be stepping up to the challenge :)
Any suggestions on what I should study first?
thanks guys!!!
 
#26 ·
I guess it depends on the motor as to whether or not a harmonic balancer does some of the work. Rotary motors don't use them at all. But then, a rotary motor's fly wheel is... I forget... 25lbs? It's a friggin' man hole cover ;:pRotary flywheels are known to break VW transaxles.

I guess one could claim that a piston engine doesn't "need" a clutch, but it depends on your definition of the word "need". If you want your transmission to last as long as the next guy's, then you need a clutch. If you want to be able to keep up with traffic, then you need a clutch. If you want your starter and ring gear to have a long healthy life, then you need a clutch.

And yes, I know you can shut the motor off to get started sans clutch. I drove an 83 Rx7 that way for a few months. Actually, I covered several miles (not all at once of course) on the starter in my 84 Rx7 when it was having fuel delivery problems. Those are some stout starters. I never had any trouble with either one of them. The battery cables didn't like that too much though. :p That's a Jap car though. I would not recommend doing anything like that in a British car. Good thing British cars are so light. They'd be difficult to push otherwise.
 
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