# Choosing a motor(s) and effects on range



## booksix (Aug 26, 2008)

As I'm working on my first EV, I'm very new to the performance and behavior of an electric motor. I come from a background of high torque/hp v8's and am actually pulling one out of my current car to make way for a new dc motor. My initial thought was to have a pair of DC motors coupled end to end to achieve the amount of power I'd like. I was then wondering if one motor could be somehow disconnected from power and made to free spin once up to highway speeds, to increase range... but perhaps that would be less efficient than both motors working less to maintain speed. Anyone have experience with this?

I'm also trying to decide on which motor would be good as twins (starting with one for the first year or two). My car's current ICE equipped weight is right around 3400 lbs (yes, it's a very specific car, no I don't want to pick something lighter  ) and will be a few hundred pounds heavier after the conversion. It is an 88 Thunderbird with a 5.0 v8 Mustang drive train swapped in and (had) twin turbos in the works. I'm trying to find something that will give me similar performance (or that can be _made_ to give similar performance once battery tech grows and drops in price). My initial thought was a single WarP 11" to be upgraded to a pair of 11" coupled end to end in the future. Thoughts? And just out of curiosity, how much more juice would a single 11" motor use over a single 9"?


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## 1clue (Jul 21, 2008)

I'm a n00b here too, but I just asked a similar question on a different web site where there is a motor design section.

The answer I got was that an AC induction motor has a variable field which is varied in strength by the fact of current going through the stators AND slip in the motor. So if you have a big motor and are trying to drive like a typical EV driver for extra range, the bigger motor makes less difference if it's an AC induction motor.

The context for comparison though was a brushless DC motor, which has natural magnets on the rotor. I did not ask about DC because I'm not really interested in DC. A brushless DC motor will still suck up a lot of power when it's running at partial power evidently, and coasting requires a circuit that does that, as opposed to an AC induction motor which freewheels as soon as you turn off the power.

My question was posted here:
http://www.rcgroups.com/forums/showthread.php?t=915990

This is not exactly in the context of your question, but hopefully it helps.


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## booksix (Aug 26, 2008)

thanks a lot, I'll check that out later... time for work!


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## OHM (Jun 30, 2008)

A single 13inch should be nice with a strong hybrid 3 speed
http://www.speedwaymotors.com/p/1956,509_Lightened-3-Speed-Transmission.html
and a suitable 9 inch diff with correct ratio.


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## booksix (Aug 26, 2008)

That's really sweet, but I already have my T5. So what about a future upgrade to a PAIR of 11's. Maybe 2 144v packs parallel to retain range but two motors=insane power (too insane for street?)


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## OHM (Jun 30, 2008)

booksix said:


> That's really sweet, but I already have my T5. So what about a future upgrade to a PAIR of 11's. Maybe 2 144v packs parallel to retain range but two motors=insane power (too insane for street?)


You realize you wont be able to use 1st ,2nd on your T5?

The torque these things produce only require 2 speeds really.
Especially a non-streetr. In any case youll do better for a lead whale
with a Siamese 11inch setup from Jim Husted and direct drive or a 
single 13 with a 2 speeds. I would hurry up first an invest in a Zilla 2k
before the order time runs out as they wont be available soon.
The power and torque you will get from a Siamese 11incher will cost
a quarter of a similar output ICE V8. However depends what you want
and if you are serious then even consider a Siamese 13incher by using
two cheap heavy duty forklift motors since 2 new ones will cost too
much and will be dissected and modified anyway.
Also you could design it with a removable battery pack once you are
on the track to improve your times.


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## booksix (Aug 26, 2008)

No, I didn't realize that. I'm still trying to get my head around this stuff (as much as I can without ever driving one). I suppose the 3.55 gears in the rear won't make things any better. I think one big thing I'm confused with is direct drive. Doesn't an electric motor use more amps at high revs (like an ICE uses more gas) meaning lower gears makes range greater? 

The biggest challenge for me is I love shifting my car: being in control to shift smooth or slam the gears to chirp the tires as I wind out, downshifting 2 gears for a nice spirited highway pass, etc... I don't think I could ever not have a manual transmission.....?

Also, to clear this up, this car is my daily driver, 100% street right now. I go 25 miles _one way_ to work 4-5 days/week. Right now I'm looking for something that will get me there (where I will charge) efficiently but still have a lot of power when I want it. I'm also looking to do a minimal 11" setup but I'm trying to plan it in a way so that stepping up later will require a small amount of mods, rather than starting over. I'd consider starting with a forklift motor with the idea that a 2nd would be coupled later but how could I be sure I'd find a matching piece? anyway, thanks for the input!


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## booksix (Aug 26, 2008)

ps: I'm still wondering if two motors for more power will drastically reduce my range on 1 battery pack and if one could be shut down when at highway speed to increase range... anyone have info?


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## skullbearer (Jul 9, 2008)

booksix said:


> ps: I'm still wondering if two motors for more power will drastically reduce my range on 1 battery pack and if one could be shut down when at highway speed to increase range... anyone have info?


Ok, since nobody answered that question when you asked it earlier, I'll jump in here.


Is there a difference? Yes, depending on the amount of power required to maintain your speed compared to the amount the motor can sustain constantly, there can be a difference.

Let me put it differently... say you have a motor rated for up to a constant power of X Watts, and at freeway speed you are using nearly all of that, the motor will run less efficiently under constant heavy load than under a moderate load, and so two motors under moderate load could be more efficient.

HOWEVER!!! Brushed DC motors 'short' at the point where the brushes are shifting from (+) to (-) contacts inside the motor, and so you _double_ that inherent inefficiency by doubling your motors! So it would probably end up being that 1 motor is very very slightly more efficient than 2 for maintaining highway cruising, assuming everything is being properly cooled.


It is a lot more difficult to setup your vehicle to shutoff a motor though, I think, than it is to lose maybe 1-2 miles of range due to the tiny loss of efficiency for just cruising with both. Plus since they would be under a lighter load, you could potentially keep them in good shape longer.


As for shifting, I too am in love with manual trannies, and I would suggest that you use a reduction gear with your motors so that in the 2 or 3 gears you want to use, the motors will be at their manufacturer tested peak efficiency point at the different speeds you cruise at. For me that would be 35, 45, and 60mph, so I would pick a reduction that would let me cruise most efficiently at those speeds in my 3 gears. I would probably pick it more specifically to achieve maximum efficiency rpm at 60mph, and let the other two suffer a little if necessary.


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## 1clue (Jul 21, 2008)

Somehow I get the impression that you would do better with one big motor, as long as you pick your motor technology carefully. I think the biggest issue is that you don't use permanent magnets. My own choice seems to be running toward an AC induction motor, but maybe a series or shunt might work for you, if you want DC.

Keep in mind I'm still a n00b on this too, but while I don't have any desire to lay a quarter mile of rubber I do feel the need for speed every now and then. I would rather spend a little more on a strong motor too. In other words, make sure you do some research before getting your motor.


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## booksix (Aug 26, 2008)

Well, the fact is I don't even know the difference (between AC and DC - whether it's series, shunt, perm, etc..) I like DC because there is a lot of parts available. But then I see a vehicle like Tesla's running AC and I wonder what I should REALLY do. Is there a big cost difference between the two? How about performance and range differences?

edit: ok, looks like AC is roughly twice the cost!! I'll have to go DC until I can afford a bigger system...


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## 1clue (Jul 21, 2008)

booksix said:


> Well, the fact is I don't even know the difference (between AC and DC - whether it's series, shunt, perm, etc..) I like DC because there is a lot of parts available. But then I see a vehicle like Tesla's running AC and I wonder what I should REALLY do. Is there a big cost difference between the two? How about performance and range differences?


Keep in mind I'm still just reading up on it, I knew a bit about motors before but I don't have practical experience yet.

Based on the introductory information on this site and my use of a search engine to expand on some topics, here's what I can give you for a short tutorial:


AC is alternating current, like you get in your house. Only the motor and controller and any incidental circuitry (if any) are going to change for this, the batteries and charger etc. are always DC.
DC is direct current, which is what you have in your car right now. One wire is always + and the other is always -.
Most conversions are still DC conversions because the equipment is easier to deal with and is much cheaper if you are buying components.
AC can be higher performance in every way than DC, unless I missed something somewhere. Building your own AC components, if you are qualified or willing, can be cheaper money-wise than buying DC components. Not including your labor!
AC gives you a lot more features and gives you potentially better efficiency. Also, the torque curve for an AC motor looks WAY better than the torque curve on a typical DC conversion.
Check out this site: http://www.metricmind.com/ac_honda/main2.htm

Before you go much further, I strongly recommend that you read the wiki (click on NuWiki in the upper left corner of the page) and start reading. Also, look at my first thread here: http://www.diyelectriccar.com/forums/showthread.php/newbie-3-phase-ac-place-start-17468p2.html

and then start using the search engine. People responding to your posts is easier for you, but once you get started you can much more effectively research things on your own. Everybody who answers your question colors it with their own preferences, and they are less likely to be accurate or complete when it's a response to a post than they are when it's a tutorial or wiki page.

I'm not trying to make you stop asking questions, I certainly haven't stopped asking and I'm very glad people are still answering!  I'm just saying you can get a more complete idea of what's going on by looking at what's already out there, and then ask questions to clarify what you found.

Good luck and have fun.


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## booksix (Aug 26, 2008)

Yeah, i always search first... its choosing the right keywords that is hard. 

Anyway, that page you linked was crazy! That AC setup is sick but that's a lot of room and MONEY in batteries and caps. Have you come across any information detailing how much range can be increased by AC regen braking? I downshift a lot when i drive my car so I'm sure switching over to doing a lot of regen braking wouldn't be hard for me. What I'm getting at is: can I save money in batteries (less Ah) by relying more on AC regen?


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## 1clue (Jul 21, 2008)

Usually around 10%. More if you use a huge bank of capacitors, but that costs even more yet, like over 10G.

That link was a no-holds-barred conversion. It's possible to use some not-so-good components and get the same sorts of things done, but it will be more work. If you like working on cars and aren't afraid to experiment, you might be able to do it the hard way.

Here's the place to start on a lot of these questions:
http://www.diyelectriccar.com/forums/showthread.php?t=669&redir_from=668


From what I gather from all this, if you're doing a conversion to save dollars then you need to stop right now. It's possible, but not for the type of car you're looking at, with the capabilities you're looking at. If, on the other hand, you're a gear head who wants a really cool car, then go right on ahead.

The caps will give you two things: More power from regenerative braking, and a huge kick in the seat when the light turns green, assuming your controller can handle it. Batteries don't like being run at full current rating. The less current you draw from them, the longer they last. That goes both for that charge and for the overall life of your batteries. Start doing brake torques and you will trash your batteries unless you have a capacitor bank that can handle it and still protect the batteries.

Regenerative braking is only one of the features you get with AC, and for some reason it's what everyone focuses on. For me, it's the potential higher efficiency and a torque curve that is literally flat from zero until it gets over half of red line. I would have thought you would have grabbed that right away with your particular car.

I gave you that link because his stated intent was similar to your stated intent. I would look closely at what he did, and try to figure out why he made that particular choice. Then decide if that particular choice is compatible with your situation. You could still go with AC motors and spend a whole lot less than he did. You could use lead-acid batteries for now, and still use a capacitor bank. Your performance will be less than his, but you would still get a car that can break the speed limit when you want to, even though it won't go as far on a charge and won't set you quite so far back in the seat.

Whatever you do though, remember that batteries WILL wear out, and no matter how much or how little you spend on them, the charger and battery management system will either make the most out of them or trash them in a few cycles, depending on how well you paid attention.


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## booksix (Aug 26, 2008)

Well, it is to save money, but my calculations have me paying the entire conversion off ($8-10k) in about 3 years (this is money saved in gas - including charging costs).

My main thing is to do a 'budget build' for 8-10k but that is scaleable without a full rebuild. So, I want to plan on a motor that I can buy a matched 2nd in a few years and link it up. I also don't want to have to rewire everything (i'll already have 4/0). Also, I really like having control of my car, which means I like shifting. So, if I have to use gears to keep in the power band of a DC setup rather than using no gears and having constant torque with AC it's no big difference for me...


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## 1clue (Jul 21, 2008)

Just be sure you know what the power band is on a DC motor. Generally, it gets good torque right around zero RPM and not much higher. Definitely NOT the same as an ICE.

I'm definitely injecting my preference for AC into this discussion. You need to make your own decision, just make sure you cover all the bases before you start tearing your car apart.


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## booksix (Aug 26, 2008)

From what I understand it's a lot of torque from 0 to about 4000 rpm. Yes it's much different than an ICE but so is an AC. And I'm all about hearing you thoughts, but I'm not seeing the gain for the cost yet... what am I missing?


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## 1clue (Jul 21, 2008)

Well, I wouldn't have nearly enough money to put together a car like that Honda.

On the other hand, I'm not afraid to try building my own motor and/or controller. That would increase the work several times, but cut down the money cost toward what I would spend on a DC system. I am interested in how the process works as well as in the end result. Building my own gear fits that goal nicely.

Another data point for me is that I've always had a fascination with 3-phase AC motors. Can't explain why. All the weak points of DC seem to be addressed in AC. I'm not going to try to rationalize this, I'm just not very interested in a DC conversion.

My goal is not your goal. I'm not after making a hot rod. I want a commuter that's not totally nutless. This again shifts my end goal away from yours because to make a hot rod with this technology is WAY more expensive. You might want to see what the drag racers do, because your project is more akin to a drag racer than to a commuter.


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## booksix (Aug 26, 2008)

Yeah, it's kind of a drag/street car yet a daily commuter. Seems DC is popular in drag but then again, that's only an acceleration similarity with me. I still need to get 25 miles to work each day (where I can charge). 

Anyway, aside from that, I dig your interest! Any chance you're in San diego? LOL, I'd SO love to be involved in what you want to do with building components. I actually would like to get into this stuff as a career somehow but im just starting my first build with already made/proven components.


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## booksix (Aug 26, 2008)

nm: I see your in Chicago... I'm from WI

Oh,and btw, I'm way more fasicnated with AC as well. Wish I could get the price down!


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## 1clue (Jul 21, 2008)

Sorry, I'm near Chicago.

I keep thinking about a career in alternate energy of some form or another, but that's a long hop from being a computer programmer. And I'm grass-green on this too, the only reason I show up as "senior member" is because I type as fast as most people talk.

I started hanging out on rcgroups.com as well, as soon as I realized that most AC systems were out of my reach. rcgroups.com has the most informative and friendly motor design forum I've found so far. Mostly it's brushless DC for them, but the core of guys know about motor design in general and are both knowledgeable and helpful.

In spite of my grand dreams, I'm still trying to wind my first motor. I don't have a lot of time right now, but I have to start somewhere. As well, my dryer just bought the farm so maybe I have a bigger motor to try rewinding after my current kit is done. Maybe I can make a lawn mower with it.


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## OHM (Jun 30, 2008)

I think a single 13inch that has lots of torque and wont die at cruising in 5th. Youll need a custom gearset for your t5 though its a different beast to an ICE. 1st and second are gone bye bye anyway you choose


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## booksix (Aug 26, 2008)

Hmmm, too much torque huh? I'm not into changing the trans though... Guess I'm gonna go for a single 11 for now... Start with clutchless and see how that all works with my 3.55 rear gears...


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## OHM (Jun 30, 2008)

Good choice the 11inch with a transmission as the 11 still revs nice and high like a 9 and will be good if you want to go higher voltage.


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## booksix (Aug 26, 2008)

thanks ohm, I appreciate your input!!  so, what are the risks when I can't resist trying out 1st and/or 2nd?? LOL


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## OHM (Jun 30, 2008)

booksix said:


> thanks ohm, I appreciate your input!! so, what are the risks when I can't resist trying out 1st and/or 2nd?? LOL


youll move a metre if you are lucky with no traction and youll need to change gears. By then a Honda n360 scamp with 360cc would have creamed you to the next set of lights.


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## booksix (Aug 26, 2008)

that's what I figured! LOL just wanted to make sure I wouldn't damage anything!


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## OHM (Jun 30, 2008)

booksix said:


> that's what I figured! LOL just wanted to make sure I wouldn't damage anything!


well theres possible damage to someones ego.


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## booksix (Aug 26, 2008)

hahaha!!! Now that's a thought I didn't have.


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## enganear (Jun 16, 2008)

booksix said:


> hahaha!!! Now that's a thought I didn't have.


booksix,
I am planning a conversion of a 1988 5.0 Mustang. I have a World Class T5 (2.95 1st gear) and a 3.27 differential ratio. I have been through the numbers with various options and a 9" motor would be adequate and an 11" would give greater range because it provides more torque/amp. The numbers indicate a very useful 1-2 gears in town, with 3rd being good for the freeway. I intend to go clutchless, but keep in mind that clutchless shifts are slow if you are intending to race. I have not designed my adapter yet, I am still trying to find a source for 5.0/T5 interface dimensions. I would be very interested in sharing this information with you. I have not been able to find anyone who has made a T5 adapter yet.

The best thing about twinned motors is being able to run them in series at low speeds and switch to parallel to get more top end. Twin 11s would probably break your T5. Twin 13s would break the bank.
-enganear


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## booksix (Aug 26, 2008)

yup, I'm now designing a twin 8" setup that can switch between parallel and series! I have a world class as well but have 3.55's. Guess I'll see how it goes. I'm designing a motor plate and spacer that will allow clutch or clutchless but the EV shop I'm shadowing at suggests clutched. Anyway, let's kep in touch because I think we could help each other. btw, where are you located?


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## enganear (Jun 16, 2008)

Twin 8s, sounds like a plan. You should grab a Zilla while you can. It is the only controller I know of that can handle the series/parallel switching automatically based on rpm.

I am located in Greensboro, NC. 

I have searched and exhausted my automotive engineering contacts trying to find an interface drawing for the 5.0. I would really like to create a drawing that others could use. So many conversions are custom with no documents generated that can be shared with the EV community. If we had a library of drawings for adapters, any DIYer could have the machined adapter parts made locally. 

-enganear


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## booksix (Aug 26, 2008)

Really?!? I guess I didn't realize the series/parallel switching thing was dependent on the controller (I'm by far no EE). That's a bummer too, because I'm trying to just get a start (maybe a single motor to begin) with a 'budget' setup and I wasn't planning on a Zilla. I was hoping a Logisystems 1000a could get me by until someone bought zilla or came out with a competitive product (and I was ready to unload the cash)!

As for the drawing, I know what you mean. I have 2 weeks to do my conversion and can't get my motor plate started until I have the 5.0 out! But, if I get there first I would love to hook you up. I'm working with a local machinist who went private a few years ago and he said he can do all the CAD drawings for me. So I'll for sure upload those to a server where others can get them...


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## enganear (Jun 16, 2008)

The Zilla is the only controller currently available (for a short period of time) that provides an output that can be programmed for auto series/parallel switching. You can use any controller and switch it manually. You will need some additional contactors either way. I know a guy with twinned series 7s in a TR7 with no transmission. He has a top speed of 40 (72V) and has not installed the parallel circuits yet. Reversing two series wound motors is a complex affair!
-enganear


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## fugdabug (Jul 14, 2008)

> As for shifting, I too am in love with manual trannies, and I would suggest that you use a reduction gear with your motors so that in the 2 or 3 gears you want to use, the motors will be at their manufacturer tested peak efficiency point at the different speeds you cruise at. For me that would be 35, 45, and 60mph, so I would pick a reduction that would let me cruise most efficiently at those speeds in my 3 gears. I would probably pick it more specifically to achieve maximum efficiency rpm at 60mph, and let the other two suffer a little if necessary.


Skullbearer,
When you speak of a reduction, are you speaking of a 'gear reduction' adapter to the motor itself? And could you elaborate on this in a separate thread? I would like to understand this application better, as I have a situation with my reverse gear such that when I touch the pedal I leave dugouts in my driveway!...TIA
-fugdabug


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## booksix (Aug 26, 2008)

Pretty sure he's talking about trans or rear-end gears. For you, I think you need to read up on your controller and see if it is capable of reducing the throttle when in reverse (you'd have to connect it to the reverse switch in the transmission).


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## booksix (Aug 26, 2008)

Ok, so I'm looking more into a single 11" (easier and actually cheaper to start because it doesn't absolutely require a zilla) vs a twin 8" setup (zilla for series/para switching). I guess the next question I need to ask is: can anyone explain exactly what switch between series and parallel motors does? How does effect performance and range? Does it provide more power when reaching the portion of the torque curve where most elec motors start to fall?


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## Ioku (Sep 27, 2007)

> Quote:
> Originally Posted by *booksix*
> _thanks ohm, I appreciate your input!! so, what are the risks when I can't resist trying out 1st and/or 2nd?? LOL_
> 
> youll move a metre if you are lucky with no traction and youll need to change gears. By then a Honda n360 scamp with 360cc would have creamed you to the next set of lights.


Im sort of confused here why would you have problems moving in 1st or 2nd, I would think this would be best for a fast take off as you would have the most torque in a low gear like this, if 1st gear and your final drive net you around a 7:1 ratio then you would have 7 times the torque you would if you just had a 1:1 ratio. 

maybe I'm missing something but I would think that for the best acceleration shifting though all the gears like you with an ICE would be best.


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## booksix (Aug 26, 2008)

The problem is the DC motor makes all it's torque right off the bat where-as an ice doesn't peak until it gets up in the revs. The result of '1st gear plus an electric drivetrain' is roasting the tires, winding out of 1st gear almost immediately and the risk of over revving the motor (from what I understand...). Plus, you'll have a lot of burned rubber and no movement to show for it!


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## OHM (Jun 30, 2008)

booksix said:


> The problem is the DC motor makes all it's torque right off the bat where-as an ice doesn't peak until it gets up in the revs. The result of '1st gear plus an electric drivetrain' is roasting the tires, winding out of 1st gear almost immediately and the risk of over revving the motor (from what I understand...). Plus, you'll have a lot of burned rubber and no movement to show for it!


spot on.

The ideal ratio is round 2 to 1 for take off thats why many EVrs only use 3rd gear in most 5 speed boxes.


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## fugdabug (Jul 14, 2008)

OHM said:


> spot on.
> 
> The ideal ratio is round 2 to 1 for take off thats why many EVrs only use 3rd gear in most 5 speed boxes.


Ummm... gotta say, that 3rd gear is a sweet one... very much like an old Indian Chief Motocycle, you could darn near drive all around town in 3rd gear!
I tried 3rd on our driveway (of about 3/8th mile length) and it was good up and down a slope and on the flat!


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## enganear (Jun 16, 2008)

OHM said:


> spot on.
> 
> The ideal ratio is round 2 to 1 for take off thats why many EVrs only use 3rd gear in most 5 speed boxes.


I have not finished my EV, but I have ridden in others and modeled extensively. I have to disagree with your statement. My calcs show significant range and motor current advantages to using 1st and second gear.

Go to youtube and search for the Electric Delorean. It is probably the best video out there for getting the feel of driving a manual transmission EV.

Not spinning the tires is just a matter of controller setup and right foot discretion.
-enganear


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## sunworksco (Sep 8, 2008)

Transmissions are really a waste of money and energy.Isn't it better to go from 0-120mph in one gear with no shift lag? I'm using an ac motor with a www.1speedway.com quick-change rear end with gear ratios as low as 10 to 1.It only weighs about 78lbs. and has Porsche 930 axle shaft hubs and can be used with inboard brakes.The diff can be used in reverse or forward direction mounting and front or rear drive.This eliminates drivelines and allows for a center aluminum spine for strenghthening the chassis.Look at the Lotus Elise chassis used on the Tesla EV.
High performance evs are all about eliminating overall weight.The Lotus chassis is easy enough technology for the DIY,just epoxy and rivet screws.Think of it as an Erector Set only with an extra dab of epoxy.You can even update their chassis design by using www.alulight.com aluminum foam panels to construct the chassis.I'm also sourcing out Porsche 996 suspension from the recycle yards and also using Ducati 1098 center-lock pin-drive wheel hubs and www.blackstonetekwheels.com carbon fiber wheels.


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## booksix (Aug 26, 2008)

yeah, that's a great setup, but most of us are building our cars with what we already have, not from scratch. Thus, we end up with manual transmissions... I would like, in the future to have a higher end setup that I can run direct drive, but for now this is where I'll be (i think  )


edit: btw, I would like to see this car you're building though!


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## fugdabug (Jul 14, 2008)

I'll be happy to do my errands and grocery runs to town...


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## enganear (Jun 16, 2008)

AC motors have a much wider speed range than DC motors making direct drive more feasible. Most of us are using DC motors and unless you are racing and measuring battery life in minutes, direct drive will kill your range and shorten your battery life. Starting amps will be enormous and limiting current will kill the performance.

Do you really think all those EVers out there with DC motors and manual transmissions are wasting their money?

Good luck on your project, if its real.....
-enganear


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## Ioku (Sep 27, 2007)

sunworksco said:


> Transmissions are really a waste of money and energy.Isn't it better to go from 0-120mph in one gear with no shift lag? I'm using an ac motor with a www.1speedway.com quick-change rear end with gear ratios as low as 10 to 1.It only weighs about 78lbs. and has Porsche 930 axle shaft hubs and can be used with inboard brakes.The diff can be used in reverse or forward direction mounting and front or rear drive.This eliminates drivelines and allows for a center aluminum spine for strenghthening the chassis.Look at the Lotus Elise chassis used on the Tesla EV.
> High performance evs are all about eliminating overall weight.The Lotus chassis is easy enough technology for the DIY,just epoxy and rivet screws.Think of it as an Erector Set only with an extra dab of epoxy.You can even update their chassis design by using www.alulight.com aluminum foam panels to construct the chassis.I'm also sourcing out Porsche 996 suspension from the recycle yards and also using Ducati 1098 center-lock pin-drive wheel hubs and www.blackstonetekwheels.com carbon fiber wheels.


Well you can still do well with only one gear, especially with an AC motor capable of high rpm's but I still think it would be better to have more than one gear. 

If we use your set up as an example, lets say you go with that 10:1 ratio rear end, well because it is geared so low it will be great for initial take off and lower speeds but even with a high rpm ac motor you will limit you top speed once your rpm’s hit there max. so if you gear it higher to give you more top speed your take off’s will suck and you will pull too many amps so you still need at least 2 or 3 gears. Now maybe if you had some super motor that had a rev limit of like 20,000 rmps with a flat torque cure to whole way and was most efficient all the way to the max then you could be fine with one gear, just gear it low from the start so your not killing the amps to get the thing to move and then just keep crankin' the rmp’s for as fast as you want to go. 

But if your like most people using a DC motor then a trans is a must as they have a rather small window of efficacy and max there rpm’s at around 5,000, so you have to have different gears.


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