# Transmission?



## madderscience (Jun 28, 2008)

Hi JokerzWild-

Your question has been mulled many times over on the forums and the wiki so there is plenty of dialogue and opinions for you to read over.

To summarize things from my POV:

The benefit of using a transmission is that you can get by with a less expensive or less powerful motor and controller. This is because, just as with a gas engine, you can change gear ratios to get more torque or more speed at the wheels as your needs dictate without requiring as much extremes from the motor and controller. The disadvantage of course is the extra weight, complexity and losses from the gearbox. Conversions that retain a transmission are generally less expensive than direct drive conversions. There are some games that can be played to improve the efficiency of a manual transmission.

The benefit of direct drive (no transmission, though there will still be a single ratio gear reduction system even if it is nothing more than the differential) is that the system can be simpler and possibly lighter. The disadvantage is that the motor generally needs to handle a much wider RPM range and/or the controller must be able to dump considerably more amps to the motor to make enough starting torque for those situations where with a tranny you would have just downshifted. Direct drive setups are generally going to be more expensive. Direct drive with a DC system is going to require a big motor and a big controller and probably about a 5:1 overall gear ratio. Direct drive with AC won't need to pull as many amps but you will want about 8:1 to 10:1 overall gear ratio and you will probably need to build a much higher voltage battery pack.

Most conversions use a donor car with a manual transmission. Most manual transmissions are around 90 to 95% efficient so there is not a huge loss there. Some people keep the clutch and some don't. I would keep the clutch with a first time conversion, unless it is a very small car with a small motor. The benefit of removing the clutch and flywheel is less rotating weight which is a double benefit if you know your physics. The disadvantage is shifting can be difficult and tough on the transmission especially with a large vehicle or a big motor.

Some people try to use automatic transmissions. These can work, but they are harder to integrate with (for example they require the motor to "idle" just like a gas engine to run the hydraulic pumps) and your typical automatic transmission is going to be less efficient than a manual especially in an older car. That said, there are a lot of crazy things you can do with some automatic gearboxes, find the thread on the two speed powerglides and read a bit there. I would say however that doing something with an automatic is not a good idea for a first-time-conversion. I will also say that I don't think I have ever seen a conversion using an automatic transmission that I thought would be as efficient as it could have been with a manual transmission.

For your specific scenario, if you had a 2500lbs car (which btw means it is either a custom chassis or you are using lithium batteries) then this would work:

156V system. Lightweight battery pack to satisfy the 2500lbs requirement.
1000A logisystems controller (the biggest one I know of currently availalbe). Batteries need to be able to handle that kind of current. Lithium or AGMs, basically.
warp or advanced DC 9" motor coupled directly to the driveshaft
5:1 to 6:1 differential
small diameter tires

The car's top speed will be motor RPM limited and probably around 65-70mph if the motor redline is 5000RPM which is typical for a stock 9" motor.

If I lived in a mostly flat area, I could leave my 3400lbs, lead acid MR2 in 3rd gear all the time. 3rd in my car is about 6:1 overall gear ratio. I have a 500 amp controller so my starts are leisurely in 3rd but it keeps up in traffic. (I usually run in 2nd up to 40mph and then shift) I have a 9" motor. So in the example, with 2x the starting torque and 2/3 the weight of my car, you should have decent direct drive performance.

Good Luck.


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## Jokerzwild (Jun 11, 2009)

Thanks,

your mr2 3400lbs with lead acid, I was going to go with lifepo batts but I am seriously thinking about going with a deep cycle system. The reason being is the technology curve, since people are throwing tons of $ into this it will only get better and cheaper. 

So my question to you is whats your volts and your ah on your batts and how far do you think you can get on it?


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## judebert (Apr 16, 2008)

Nice summary. The only thing missing is the stress on the batteries. Most batteries lose capacity and life cycles if you pull too much current from them at once. You want to keep the current as low as you can while still meeting your other design and performance constraints.



madderscience said:


> Direct drive with AC won't need to pull as many amps but you will want about 8:1 to 10:1 overall gear ratio and you will probably need to build a much higher voltage battery pack.


The reason an AC system won't pull as many amps is because it's a higher voltage pack. This is not always the case, of course, but it's true in enough cases that it's become a generality.

Here's the thing: to accelerate a car at any particular rate with a fixed gearing ratio, you need a certain amount of power. It's the product of voltage and current (VxA). If you use a higher V, you need less A. That's it.

With most motors, you need low gear ratios to achieve your desired top speed. At low gear ratios, like direct drive, you need a LOT of power to accelerate. 

With a higher voltage system, you use less current for that acceleration. If you can't afford the higher voltage system, you use a lower voltage system. If you keep the same low gear ratio, you'll need a lot more current to compensate for the lower voltage. That's rough on the batteries. But if you switch to a higher gear ratio, you'll never be able to achieve the top speed you desire.

To keep the current low, you have to compromise on design, performance, or both. A transmission loses some efficiency and space, adds weight and complexity, and requires extra shifting time. In return, you get good acceleration at lower currents without losing your top speed, you can use less expensive controllers and motors, and your batteries are happier.

It's all a matter of tradeoffs. I built for reliability, so I kept the transmission.


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## Jokerzwild (Jun 11, 2009)

What about?

An older 3 speed transmition, why would you need 5 speeds for an electric motor? I understand because of tourque I could not ust the old gears but I can rebuild it with better parts. Or even a 2 speed?


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## Jimdear2 (Oct 12, 2008)

Jokerzwild said:


> What about?
> 
> The following is for RWD
> 
> An older 3 speed transmition, why would you need 5 speeds for an electric motor? I understand because of tourque I could not ust the old gears but I can rebuild it with better parts. Or even a 2 speed?


Joker,

The older big 3 speeds were mostly cast iron monsters and very very heavy. I haven't seen a aluminium manual 2 speed that would handle the torque of a BIG motor. 

The only two speed I know of that fits that bill is a modified converterless manually shifted powerglide which is a whole different bag of worms.

Here is a thought. Look for a medium sized iron 3 speed and modify as follows

Weld up low gear and turn it into a park gear. Then use 2nd and 3rd as a low high shift. For this set up I would keep the clutch.

Most of the old Iron 3 speeds had removable bell housings which will make motor attachment easier.


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## racunniff (Jan 14, 2009)

madderscience said:


> Hi JokerzWild-
> 
> Your question has been mulled many times over on the forums and the wiki so there is plenty of dialogue and opinions for you to read over.
> 
> ...


Good summary. Here is my analysis for the ElectroJeep: http://electrojeep.blogspot.com/2009/01/more-motor-notes.html - I could get by with a 3-speed transmission, probably, but am just using the original 5-speed due to cost / convenience issues.

Not having a variable transmission of any kind would result in performance compromises at one end or the other of the speed range.


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## Jokerzwild (Jun 11, 2009)

(Here is a thought. Look for a medium sized iron 3 speed and modify as follows

Weld up low gear and turn it into a park gear. Then use 2nd and 3rd as a low high shift. For this set up I would keep the clutch.

Most of the old Iron 3 speeds had removable bell housings which will make motor attachment easier. )

I love that idea!
2nd for optimal race gear and 3rd for optimal free way speeds, this should get rid of any shifting issues.


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## DavidDymaxion (Dec 1, 2008)

There is also an efficiency loss if you don't used a transmission!  It's a case of "it depends."

An electric motor has 0 efficiency at 0 rpm. This rapidly climbs to ~80 to ~85% above low rpms and low loads. If you are doing lots of stop and go up steep hills, the tranny car will be more efficient. If you do lots of steady cruising the direct drive car might be more efficient.

If you are doing regen, the tranny car can be more efficient, in that you can downshift to spin the motor faster and get more regen. 

Poke around http://www.evalbum.com . Informally, it seems most successful direct drive EVs either have AC or twin DC motors. Most successful DC conversions keep the tranny.


Jokerzwild said:


> I have heard there is a large power loss when using a transmission on an Electric Motor is this true? Also my guess is there is also an efficiency loss when using a transmission. So what is the happy medium at what size of motor would you be able to push a 2500lb car with great speed without a trans? If I do not have a trans will freeway driving be doable?


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## madderscience (Jun 28, 2008)

To answer Jokerz's earlier questions:

The maximum range I have seen in my car was 66 miles (55 miles on the freeway at 55mph) on one charge. That was a range rally where I pushed it to the limit. I frequently drive 30 miles with no problems. With a few hours of opportunity charging here and there I have easily done 50+ miles in a day without any worries. Most of my longer drives are relatively flat but I do have a lot of hills around here to negotiate too.

My battery pack weighs 1250lbs alone. Its heavy, but 6V golf cart batteries' bang for the buck is about the best for lead acid. LiFePo4 can beat the overall life cycle costs if it actually lasts as long as the claims say but that is more complex and a much bigger up front cost.

I could get away with just two gear ratios in my car: 2nd (8:1 overall) and 3rd(6:1 overall). In a perfect world though If I only had two speeds I would try to make them about 5:1 and 9:1. However, my transmission has four forward speeds. 4th is somewhat better at higher speeds I've decided (60+mph) or when I am coasting but I don't use it much. The only time I have needed to use first is the one time I ran my battery pack down enough that I needed the lower gear to get going on a hill.

I removed 5th and reverse from my transmission to try and reduce internal friction. If I had been clever I would have done as some suggested here and found a way to make reverse into a parking cog; I like that idea a lot.

Judebert is right that direct drive can stress the batteries more, but with a light enough car and a torquey enough motor you would probably be OK even with (good quality) FLA. To respond to Judebert's comment about why AC used less current, there are 2 things that made my AC example use less current: the theoretical higher voltage and W=V*A as he explained, AND the higher gear ratio, meaning less torque is needed from the motor. You can get away with this because AC motors usually redline at 8000 to 10000 RPM while the DC motors you would use for direct drive are going to redline at 5000 or so.


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## Jokerzwild (Jun 11, 2009)

MAD;

I shot you an message please take a look.

Thanks,
Scott


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## SimonRafferty (Apr 13, 2009)

Another easy source for 2 and 3 speed transmissions is transfer boxes from 4x4's. Many (Jeep & Suzuki come to mind) have a prop shaft input and output with bolt together flanges so easy to adapt to.

High range ratios seem to run from about 1.1:1 to 1.6:1 and low from 2: to 4:1.

I have one (Suzuki Samurai) with selectable 4 wheel drive and I plan to use the flange that would have driven the front wheels to drive the AC pump. Then I only need turn the lossy belt drive when needed. 

An advantage of a transfer box is that it is intended to be driven by a regular gearbox so has to be rated for high input torque - typically over 350Nm even on a small 4x4.

Si


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## Jokerzwild (Jun 11, 2009)

Great idea thanks.


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## Jokerzwild (Jun 11, 2009)

I will also have to take a look at the 2 stage turbo shifters from the 80's and maybe I can use that.


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## Jimdear2 (Oct 12, 2008)

SimonRafferty said:


> Another easy source for 2 and 3 speed transmissions is transfer boxes from 4x4's. Many (Jeep & Suzuki come to mind) have a prop shaft input and output with bolt together flanges so easy to adapt to.
> 
> High range ratios seem to run from about 1.1:1 to 1.6:1 and low from 2: to 4:1.
> 
> ...


Si,

One problem with using Transfer Cases as a two speed trans comes to mind. Most transfer cases require you to come to almost a complete stop to change ranges. It's not a killer but it does preclude some of the advantages of having a two speed. You would have a city gear and a highway gear. The only real problem I would see is acellerating from stop to speed on the highway

Also many of the earlier vehicles required you to stop even to engage 4WD. There were some that allowed engagement of 4 wheel drive on the fly so that would handle your proposed A/C pump drive. Although stoping to start up A/C is not going to be a big problem.

It might be wise to get hold of a Suzuki Samurai Owners Manual and see what they say about Hi and Low range shifting.

If it is going to be a problem I hope I caught you in time.


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## Jimdear2 (Oct 12, 2008)

Jokerzwild said:


> I will also have to take a look at the 2 stage turbo shifters from the 80's and maybe I can use that.


Joker,

Help me out here what is a "Two Stage Turbo Shifter"? It is not a term I am familiar with. Could you give me a description or maybe a link to a site or WIKI. 

Thanks


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## Jokerzwild (Jun 11, 2009)

Its not 2 stage its an item cars like the Dodge Colt had when you shifted you had a 2nd shifter that aloud you to shit in and out of the turbo.


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## grouster (Nov 20, 2008)

If was going to build a ground up EV, I would use an electronic underdrive unit. This company even lets you select gearing. http://www.usgear.com/dual_range.htm They are not cheap, but the ability to shift on the fly would be nice and I imagine that some electronic guru on this forum could figure a way to make it shift in and out on its own under the load conditions lol...


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## SimonRafferty (Apr 13, 2009)

I can think of more useful ways to spend $3000! 

You would need to build a co-axial adaptor gearbox to connect to one of these - so it's not even going to be an easy conversion.

Si


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## SimonRafferty (Apr 13, 2009)

Jimdear2 said:


> Si,
> One problem with using Transfer Cases as a two speed trans comes to mind. Most transfer cases require you to come to almost a complete stop to change ranges.


I agree - but all I wanted out of it was a fixed 1.6:1 reduction and that should give me a fairly usable overall ratio of 6:1. It also has low range at 2.5:1 which should still give me a top speed of about 70. I had not intended to shift while driving - in fact the stick shift is in the engine bay!

It's all mounted up and nearly ready to go - so I'll see for myself in a couple of weeks!

Si


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## Guest (Jun 26, 2009)

Dual Range Transmission! Just like the transmission on my old Ford 8N. 8 Forward speeds and 2 reverse. Works like a charm. Heavy!


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## rillip3 (Jun 19, 2009)

gottdi said:


> Dual Range Transmission! Just like the transmission on my old Ford 8N. 8 Forward speeds and 2 reverse. Works like a charm. Heavy!


What in the world do you need two reverse speeds for? One for backing up and the other for... what, backing up the freeway??


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## Guest (Jun 26, 2009)

rillip3 said:


> What in the world do you need two reverse speeds for? One for backing up and the other for... what, backing up the freeway??



LOL

You don't.


Pete


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## Jokerzwild (Jun 11, 2009)

Obviously a drug runner, why else would you need a high rate of back up power

I would realy think about using another car for drug running since you can only go 30 miles


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## FreedomVoltage (Jun 28, 2009)

well the electric drag racing team Plasma boy racing there car "White zombie" uses a dual 8" motor direct drive and a zilla controller to boost it from 0 - 60 in 2.9 seconds, so there realy is no difference between tranny and no tranny cause the A123 systems racing team has the drag bike killacycle and it uses a transmission... and moves at 200 mph ... so REALY a hydromatic 2 speed transmision would be the absolute best for an electric motor. it has 1st gear to help launch off the line and the 2ond gear is prety much direct drive all the way to the top RPM range. so it is like having your cake and eating it too 

happy motoring

oh ps this thing goes just as fast in reverse as it does in forward... i think that's what some one was looking for.... lol the "drug runner"....


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## Jokerzwild (Jun 11, 2009)

What do you think?

Chev power glide 2 speed auto trans with torque converter?

How hard is it to attach a auotmatic trans to the unit?


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## FreedomVoltage (Jun 28, 2009)

Jokerzwild said:


> What do you think?
> 
> Chev power glide 2 speed auto trans with torque converter?
> 
> How hard is it to attach a automatic trans to the unit?


you just need an adapter plate and a coupler, you can have them made at a machine shop, make it yourself or buy one off the net


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## toddshotrods (Feb 10, 2009)

FreedomVoltage said:


> ...cause the A123 systems racing team has the drag bike killacycle and it uses a transmission... and moves at 200 mph ...


Did you mean to say KillaCycle does not use a transmission? On their site is says:


> Drive: direct chain drive on the rear wheel.


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## FreedomVoltage (Jun 28, 2009)

toddshotrods said:


> Did you mean to say KillaCycle does not use a transmission? On their site is says:


oh oops, lol on the show i was watching (hot rodz i think) it said it had a two speed transmission... maybe in an older model?? at any rate, it clearly does not matter whether you use a transmission or not, it all depends on the electric motor you use. i still say a 2 speed hydromatic tranny would be best due to the lack of a top end on the transmission, it'll better match the rev range of an electric motor.


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## toddshotrods (Feb 10, 2009)

I agree that a Powerglide is a great option to give a little more flexibility with a lot of EVs. I thought long and hard about it, but I plan on racing my EV and finally decided on using a Gear Vendors overdrive instead. It would cost more to have a 'glide built into a comparable full race transmission, and would be more complex and a little bulkier. The GV unit is basically a two-speed, planetary, transmission that is similar to an automatic. It doesn't require a pump though, and can be switched between drive and overdrive with a simple electric switch. It has a hefty price of admission ($2500+), but is rated for 1200hp and commonly used in racing.


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## Jokerzwild (Jun 11, 2009)

Cant you just beef up low since you will not shift through the 1/4. You can get them used on ebay right now. Well you would have to do a little more then just beefing up low but not to much.


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## toddshotrods (Feb 10, 2009)

I plan to run slaloms, autocross, etc., as well as drag racing. I want to thoroughly abuse my EV, and I don't want any weak components that I have to work around. I don't want to have to think whether or not the transmission can handle what I need to do. A race-built glide could do everything I'm asking but it would cost a little more and be a good bit bulkier - as I mentioned.


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## Bowser330 (Jun 15, 2008)

toddshotrods said:


> I agree that a Powerglide is a great option to give a little more flexibility with a lot of EVs. I thought long and hard about it, but I plan on racing my EV and finally decided on using a Gear Vendors overdrive instead. It would cost more to have a 'glide built into a comparable full race transmission, and would be more complex and a little bulkier. The GV unit is basically a two-speed, planetary, transmission that is similar to an automatic. It doesn't require a pump though, and can be switched between drive and overdrive with a simple electric switch. It has a hefty price of admission ($2500+), but is rated for 1200hp and commonly used in racing.


i checked out the website, the ratios sound great...but thats serious bank$$...


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## toddshotrods (Feb 10, 2009)

Bowser330 said:


> i checked out the website, the ratios sound great...but thats serious bank$$...


Yup. I'm used to it though because if I was building a conventional ICE hot rod I would spend at least that much or more. An older 3spd full-race "automatic" ranges between $1500 and 2500, depending on how strong you need it. The newer, electronic, overdrive, automatics cost at least as much, and often more, to build and require aftermarket controllers.

I understand the reasoning of most people here who are looking for cost effectiveness and efficiency, and want to keep the initial cost low enough that the conversion eventually pays for itself. I just added the performance perspective because I've noticed that there are a few around here. The information may help someone. Anyone who is serious about performance knows that you simply have to "pay to play".


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## Jokerzwild (Jun 11, 2009)

Thanks!

I am in the same boat as you, I want the transmission only for distance. Because I do not think I will need it to shift out of first in the 1/4 mile. If you have a good enough motor you should not have to shift and if you did it would be at the end and it would do nothing. I could be wrong! 

Are you planning on shifting in the 1/4?


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## toddshotrods (Feb 10, 2009)

Jokerzwild said:


> Thanks!...Are you planning on shifting in the 1/4?


You're welcome - what did I do?

I plan to try it both ways, eventually. The "normal" setup probably won't require shifting through the quarter. After some of the bugs are worked out I would like to try a more intense rear end gear and tire setup (wrinkle walls) and see what kind of numbers I can put down using the overdrive. Most likely the shift point would be past half-track.

Also remember that the same thing CAN be accomplished with the Powerglide, and it does offer the advantage of being able to step your way up to maximum performance. I just have to do things the hard way.


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## FreedomVoltage (Jun 28, 2009)

toddshotrods said:


> I agree that a Powerglide is a great option to give a little more flexibility with a lot of EVs. I thought long and hard about it, but I plan on racing my EV and finally decided on using a Gear Vendors overdrive instead. It would cost more to have a 'glide built into a comparable full race transmission, and would be more complex and a little bulkier. The GV unit is basically a two-speed, planetary, transmission that is similar to an automatic. It doesn't require a pump though, and can be switched between drive and overdrive with a simple electric switch. It has a hefty price of admission ($2500+), but is rated for 1200hp and commonly used in racing.


good choice, that should give you an EV that will win every race against a regular combustion engine... lol your going to have to build a second EV to give you some competition...


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## toddshotrods (Feb 10, 2009)

FreedomVoltage said:


> good choice, that should give you an EV that will win every race against a regular combustion engine... lol your going to have to build a second EV to give you some competition...


Thanks, but I have my work cut out for me. There are some really quick ICE cars out there. I doubt I'll be the fastest in the circles I plan to run with, but it should get some respect as a potent vehicle (not just the "fast for what it is" thing).


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## FreedomVoltage (Jun 28, 2009)

toddshotrods said:


> Thanks, but I have my work cut out for me. There are some really quick ICE cars out there. I doubt I'll be the fastest in the circles I plan to run with, but it should get some respect as a potent vehicle (not just the "fast for what it is" thing).


WOW what are you trying to race against Top-fuel dragsters? have you not seen the videos of the "white Zombi" from plasma boy racing? it kills everything it races... i'd expect nearly the same performance from your EV... =)


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## Bowser330 (Jun 15, 2008)

toddshotrods said:


> I agree that a Powerglide is a great option to give a little more flexibility with a lot of EVs. I thought long and hard about it, but I plan on racing my EV and finally decided on using a Gear Vendors overdrive instead. It would cost more to have a 'glide built into a comparable full race transmission, and would be more complex and a little bulkier. The GV unit is basically a two-speed, planetary, transmission that is similar to an automatic. It doesn't require a pump though, and can be switched between drive and overdrive with a simple electric switch. It has a hefty price of admission ($2500+), but is rated for 1200hp and commonly used in racing.


What parts are you using for your racing EV?

a couple of built kostovs? twin controllers?


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## toddshotrods (Feb 10, 2009)

FreedomVoltage said:


> WOW what are you trying to race against Top-fuel dragsters? have you not seen the videos of the "white Zombi" from plasma boy racing? it kills everything it races... i'd expect nearly the same performance from your EV... =)


I hope to land somewhere in between the two. Yes, I am very familiar with the White Zombie; as I always say, it's the car that tipped the scales in favor of me building a performance EV. I want to get a little more aggressive off the line than he's going for currently. With a little more edge on the chassis setup, some more bite in the tires, and an extra gear change down track, I am hoping to slingshot myself into some crazy ETs.



Bowser330 said:


> What parts are you using for your racing EV?
> 
> a couple of built kostovs? twin controllers?


My plans are based on an 11-inch GE, that I plan to have built into a race motor by Jim Husted (the same guy who built the White Zombie's motor if you aren't familiar with the name). I've begun talking with someone here about developing a custom controller setup. My benchmark for the controller is the Zilla 2K-HV (the kind White Zombie uses), but I am trying to do this with a SepEx motor, instead of the more common series motor. So the end goal is basically 300+ volts/2000amps slammed into an 11-inch torque monster. The vehicle itself should weigh in well under 2000lbs. The exact figure depends on the batteries. If I can find a way to secure an A123 pack like he has in the the White Zombie it would probably weigh around 1500lbs. It will basically be a race car chassis with minimal amounts of carbon fiber skin over it.

I plan to run through cones, and around corners too - not just a straight line.

Now that I've thoroughly hijacked this thread - please follow me here if you want more info. My apologies to the OP of the thread.


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## JaysinSpaceman (Jul 11, 2009)

OK, I am new here and to the world of EVs but I have been a fabricator and builder of all things with wheels for as many years as I've been able to see over a fender. I had to add my $.02 here on the subject of two speed transmissions. While the Gear Vendors unit is very nice it is meant for 600+ hp and huge amounts of torque, a wee bit of over kill for 90% of EVs (I think anyway) and way pricey.

You are probably saying get to the point. Here it is.

The gear vendors unit is very similar to (and I think based on) the mid-70s Volvo manual transmission over drives. They even function in the same way,and are an add on (sealed seperate unit) to the back of the 4 speed. The Volvo units are very strong (not as strong as GV), capable of 400 hp in a light vehicle. I helped a friend of mine adapt a Volvo unit to the turbo 400 in his 67 big block pickup truck and it survives there just fine. They are shifted electricly and fine to shift while under load, and they are in junk yards all over the country for cheap. 

I cant remember the ratios off the top of my head (1:1 + overdrive). This is just a thought and way cheaper then the GV or modifing a automatic.

I hope this is of some help.
Jaysin


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