# [EVDL] Direct Drive vs. Transmission in RWD EV



## EVDL List (Jul 27, 2007)

I've been lurking in the background for a few weeks and enjoy reading the
list.

My question is this:

What are the pros and cons of going with a direct drive EV (specifically, I
mean using a rear wheel drive (RWD) donor car and connecting the motor to
the driveshaft directly, and driving through the rear differential ratio
only with no transmission). I know it requires electrical switching for
reverse, but my main question is can you achieve acceptable performance
(acceleration and range). Compared to an EV with a transmission, what does
it mean in terms of motor and controller? Do you need a bigger motor?
Better controller? More batteries?

I like the idea of direct drive because it eliminates one more of the
remnants of ICE-powered vehicles.

>From what I have seen, there aren't too many EV conversions without a
transmission or gearbox, so I have a feeling there may be some big
drawbacks....

Looking forward to your comments!

Regards,

Greg - Melbourne, Australia

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## EVDL List (Jul 27, 2007)

Direct drive (differential only) requires a bigger motor and
controller for similar performance; a rough estimate is about twice as
much.

The number of batteries needed doesn't change, though.

-Morgan LaMoore



> Greg Sievert <[email protected]> wrote:
> > I've been lurking in the background for a few weeks and enjoy reading the
> > list.
> >
> ...


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## EVDL List (Jul 27, 2007)

> On 2 Aug 2008 at 18:49, Greg Sievert wrote:
> 
> > I've been lurking ... What are the pros and cons of going with a
> > direct drive EV (specifically, I mean using a rear wheel drive (RWD)
> ...


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## EVDL List (Jul 27, 2007)

Basically only use direct drive if you are going for performance.

This was discussed a couple months ago.
Going direct drive costs about $4k more than using a gearbox, but if you
want performance, most gear boxes just arent strong enough.
If you are going for cost efficiency (as opposed to energy efficiency) keee
the gearbox.

Matt 

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of Greg Sievert
Sent: Saturday, 2 August 2008 4:49 PM
To: [email protected]
Subject: [EVDL] Direct Drive vs. Transmission in RWD EV

I've been lurking in the background for a few weeks and enjoy reading the
list.

My question is this:

What are the pros and cons of going with a direct drive EV (specifically, I
mean using a rear wheel drive (RWD) donor car and connecting the motor to
the driveshaft directly, and driving through the rear differential ratio
only with no transmission). I know it requires electrical switching for
reverse, but my main question is can you achieve acceptable performance
(acceleration and range). Compared to an EV with a transmission, what does
it mean in terms of motor and controller? Do you need a bigger motor?
Better controller? More batteries?

I like the idea of direct drive because it eliminates one more of the
remnants of ICE-powered vehicles.

>From what I have seen, there aren't too many EV conversions without a
transmission or gearbox, so I have a feeling there may be some big
drawbacks....

Looking forward to your comments!

Regards,

Greg - Melbourne, Australia

No virus found in this outgoing message.
Checked by AVG. 
Version: 7.5.526 / Virus Database: 270.5.10/1586 - Release Date: 1/08/2008
6:59 PM


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## EVDL List (Jul 27, 2007)

Hi Morgan and All,

----- Original Message Follows -----
From: "Morgan LaMoore" <[email protected]>
To: [email protected], "Electric Vehicle Discussion List"
<[email protected]>
Subject: Re: [EVDL] Direct Drive vs. Transmission in RWD EV
Date: Sat, 2 Aug 2008 13:07:15 -0500

>Direct drive (differential only) requires a bigger motor
>and controller for similar performance; a rough estimate is
>about twice as much.

Not necessarily true. You could use 2 smaller
motors and series/parallel them for a 2-1 traNSMISSION
EFFECT on a smaller controller.
I'm working with a Miata for the $2008 Grassroots
challenge in Gainsville where it has to do drag, autocross
and show on just $2008 bucks!! We'll use 2 motors with a
1000+ amp contactor controller will give plenty of power at
low cost DD mounted to the diff.
Another method is splitting the motor's field into
2 and series/paralleling them for 2-1 torque output.
Almost all built as EV's use direct drive, mine all
do and no one would call them high powered at all, 3.5hp GE
motor on 1,000lbs Ewoody, did 60mph on 36vdc with field
weakening, 45mph without. The heavier you are the more you
need a transmission or if you want to get by on low power.

Jerry Dycus

>
>The number of batteries needed doesn't change, though.
>
>-Morgan LaMoore
>
>On Sat, Aug 2, 2008 at 3:49 AM, Greg Sievert


> >> <[email protected]> wrote: I've been lurking in the
> >> background for a few weeks and enjoy reading the list.
> >>
> >> My question is this:
> ...


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## EVDL List (Jul 27, 2007)

I looked into this when I first started research on my EV project, The info
that I gathered was that you could do it, but with a smaller motor you
would need a really low gear ratio on your rear end 6 or 7 to 1. Then you
may be limited on your top speed. The gears required for my s-10 could be
ordered for dragracing applications, but was more exspensive, (and seemed
to me) more trouble than keeping the tranny. 

Just my 2 cents

Josh and Jen

www.jcsevparts.com


> What are the pros and cons of going with a direct drive EV (specifically,
> I
> mean using a rear wheel drive (RWD) donor car and connecting the motor to
> the driveshaft directly, and driving through the rear differential ratio
> only with no transmission). 
-- 
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