# Kostov vs Netgain in direct drive applications



## Plamenator (Mar 6, 2009)

I think you should be more interested in motor rpm/torque rather than the coupling method.
Having no gear box means you achieve torque by overusing amps which affects your range greatly.
I remember some evidence where a gearbox conversion used 200W/km vs. 270-300W/km when gearbox was removed.
I hope you are keeping at least the axle gear ratio (1:3.6?).


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## algea07 (Oct 1, 2010)

Plamenator said:


> I think you should be more interested in motor rpm/torque rather than the coupling method.
> Having no gear box means you achieve torque by overusing amps which affects your range greatly.
> I remember some evidence where a gearbox conversion used 200W/km vs. 270-300W/km when gearbox was removed.
> I hope you are keeping at least the axle gear ratio (1:3.6?).


i was planning the use a diff ratio of around 3.6-4 which would give me a motor speed of around 3000rpm. i have a few diff options with the car i'm thinking about using.

i can guess at lower speeds or start stop traffic it would be a good idea to have a gearbox or a lower ratio to keep the revs higher and current lower, but i live in an area where the majority of roads are 100kmh(62mph). so the motor will be revving fairly high anyway.

i don't know a huge amount about how motors behave but i saw that on the netgain site they posted maximum efficiency at around 3000rpm. so i was planing on aiming to have my motor run at around that speed for as long as possible. at 100kmh, with a diff ratio of around 3.6-4, and normal sized tires the motor will spin at 3000rpm. the table they have on their website was easy for me to comprehend

i'm not sure if i;m reading the graphs correctly_(do all the lines relate to each other or just touque)_, but i have noticed that netgain only post stats at 72v while you guys have you stats at 144v and on your graph, if I'm reading it correctly your efficiency comes at a greater rpm, around 5000rpm. *does that mean that the higher the voltage the higher rpm the motor achieves maximum efficiency?* or is it a difference in how the motors are made?

with the information i had available it looks as though 3000rpm would be fine for a nine inch to handle, and given that there is two of them i figure that they wouldn't have to work to hard, so wouldn't need huge amounts of current at take off.


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## piotrsko (Dec 9, 2007)

you are aware that plamenator is the Kostov rep and all around kostov motor guru, right?


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## algea07 (Oct 1, 2010)

piotrsko said:


> you are aware that plamenator is the Kostov rep and all around kostov motor guru, right?


yeah i figured he knows what hes talking about. 

as i said i don't know much at all about motors and i'm just going off the performance data on the netgain site, and i thought if i could keep the motor revs high , around 3000rpm i should get good efficiency. this car wont see much city driving, and will spend most of it's life doing 100kmh

going direct drive just seemed easier, if I'm going to b loosing 70w per mile even at high speeds i'll leave the transmission in.


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## Guest (Mar 10, 2011)

You say you want to do a direct drive conversion but you do not give any reasoning as to why. It sounds like maybe you have not done enough research yet on the merits of direct vs transmission. A good conversion can be done even with the transmission. I'd say go with a transmission with clutch and I think that the 11 Kostov HV motor would be a good choice. I think the Warp 11 HV is a good choice. 

It is your choice. Choose wisely. 

Pete


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## EVfun (Mar 14, 2010)

I'll tweak Pete a little 

I say do a direct drive with your conversion, provided you are willing to pay the premium to really go fast on electrons. When you are ready to put up the dough to be the star of the show the transmission starts to add as many problems as benefits. They where not designed for full torque at zero rpm. 

If you are not going to make a lot of power you may as well keep the transmission. Torque multiplication in the gearbox that came with the car is a lot cheaper than a larger motor and higher current controller. Speed costs, how fast do you want to go?


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## Guest (Mar 10, 2011)

Tweek! Depends upon his needs. Does he really need direct drive? Guess we need to wait on his response. Lets hear from the horse on his needs. Could be he just wants direct and that would be his choice. I have no problem with that. Why would I! Just wondering why he has chosen that route.


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## algea07 (Oct 1, 2010)

gottdi said:


> You say you want to do a direct drive conversion but you do not give any reasoning as to why.


it's simple.

there are a few guys that have done direct drive BMW 3 series with one 9' motor 
this guy used an fb-4001, there is a two door version and a four door version.

it just seemed to me that a gearbox was a waist of space and with a big electric motor it wasn't really needed. It was just another thing that would need maintenance, it adds weight and and I'd loose some efficiency through it anyway.

so why not get rid of it.

if i'm wrong its not going to stop me, an 11 inch coupled to the gearbox wouldn't be bad it'd be cheaper then two 9's. I think i would perefer the direct drive even if i am likely to loose some efficiency.

i also looked briefly at custom diffs a while ago, i thought the stock diff might not be up to the torque and they offer ratios of 4.45. it's expensive $2500, but at least it'll last, better then 20 year old one that comes with the car anyway.


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## Guest (Mar 10, 2011)

What are you going to use your car for? Just daily driving or racing? If racing your on the right track. On the street, I doubt that loosing the tranny will help in any way. The weight loss may be reasonable but I don't think you will really gain much of anything. You won't use the tranny all the time but it will help you get from slow to fast more effectively. If you go with direct be sure your gearing is right and that you have a good controller and motor. The 11" HV motors are excellent choices. I am putting in an 11" Kostov into my VW bus. Yes with a tranny. It's a transaxle. Direct is understandable. Is your budget good enough to do the changes that are needed? Get some good lithiums too. 

Pete


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## Guest (Mar 10, 2011)

Fine examples of direct drive conversions. Have you sent them any emails to pick their brains and to ask about cost? Or difficult issues so you don't have to do the same mistakes. You need to talk with all the folks who have been successful with building a direct drive vehicle. I am a tranny guy go can't help. My preference is with a tranny. 

Pete


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## algea07 (Oct 1, 2010)

i don't want to drive a slow car, i hate he negative stereotype of slow electric cars, and the last thing i want to do is reinforce it. so it has to have power and torque and i am aware that those things aren't free. i have a budget of 25-30 thousand.

i'll have over 20kwh of lithium not 100% sure on what type.

i'm not going to be racing it, other then 1 or 2 times at a drag strip maybe, just to see what it can do. 

my performance goal is to be able to beat a 3.8litre v6 holden commodore to 100kmh(62mph) which is about 10 seconds, and i'm not to worried about going faster then that, 130max would be more then what is needed. 

but it will still be a daily street car. 

i figure a lithium electric car will cost at least $15,000, and it's not be very exiting. i can add $10,000 nave have a car i'm really going to enjoy driving for the next 10 years.


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## algea07 (Oct 1, 2010)

gottdi said:


> Fine examples of direct drive conversions. Have you sent them any emails to pick their brains and to ask about cost? Or difficult issues so you don't have to do the same mistakes. You need to talk with all the folks who have been successful with building a direct drive vehicle. I am a tranny guy go can't help. My preference is with a tranny.
> 
> Pete



yeah i'll send off a few more questions, i still have time before i have to make a decision.


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## Guest (Mar 10, 2011)

I think you can still do a very good fast car with a transmission. In some situations a transmission may be a very good thing to have if driving mostly on the street. Remember that trannies can be configured with gearing to give you the best you can extract from your motor and you can have one built that will handle the power output. Most race cars have transmissions and they do just fine pumping over 500 + ponies through them. Even when dumping the clutch. 

My little Ghia did 85 mph with only 96 volts and stock 4 speed. Not quick but it did move to a good high speed for the voltage/amperage applied to a single 9" motor. I think it can do a whole lot better with out much extra effort. 

Pete 

We will be looking forward to seeing what you decide to build and how you build it.


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## LithiumaniacsEVRacing (Oct 9, 2010)

The 'slip yoke' is designed from a turbo 400 trans tail end.



algea07 said:


> i want to do a direct drive conversion for my Ev using either an 11" or a dual 9", depending on what i can fit in the car. i looked around and decided it it either had to be a transwarp from netgain, or a kostov motor that i would have to modify for direct drive use.
> 
> i like the netgain, firstly because it comes with the slip yolk already installed and it has two bearings on the drive side for added strength, but its expensive, 2000 to 3000 more expensive (for a dual nine).
> 
> ...


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## algea07 (Oct 1, 2010)

i've been doing some digging and asking some questions, so i thought I'd come back and post what i found out.

i talked to Rob the guy who made the four door BMW, he said
_
"I have 45 x 160 Ah _[same size as what i plan to use] _cells in my BMW and I have converted 2 others with the same configuration. It works very well with a 1000 amp controller and gives a range of 110 to 120 Km per charge giving about 180 watt hours/km."_

180wh/km = 288wh/mile
which is pretty good. the range is good but he didn't post what type of driving it was. but it seems comparable to other BMW's on EV album.

i also talked to him about making the the slip yolk for me, we didn't talk price or anything technical but he seemed to suggest that if i could get him the parts he could put something together for me.

so i've decided on the dual kostov 9" direct drive.


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## rochesterricer (Jan 5, 2011)

So thats about 75 miles range? Not bad. Is that the 80% DOD number?


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## EVfun (Mar 14, 2010)

If I wanted a direct drive street EV (and I kinda do) I would consider this hardware from EVsource. 

Using the TH400 shorty housing has issues, most notably the limited oil volume that can be in there for lubrication. If you have even the slightest leak you run out almost before you know it. Some have used grease, but the tail housing bearing isn't designed to be a greased bearing. Some have run without a tail housing at all, using the splines directly, but those splines where designed to be fitted with an outside support bearing. I don't know if there would be life issues or increased vibration issues.

The sliding spline driveshaft is a common part of any vehicle with a 2 piece drive shaft. That would be most trucks and some long wheel base automobiles. It has also been used for years as a retrofit to older Mopars that came with a ball and trunnion joint to allow sliding movement in the driveshaft. The spline is designed to run dry, usually not seeing any love until it's time to replace the U-joints anyway.


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