Re: 5000 pound EV???

[RichSJ@aol.com]

FEF wrote about a 5000lb truck EV:

>On the upside, I believe I may have a more suitable challenge.  For a number
>of years I've been threatening to convert a late '60, stepside truck.  This
>truck is not used for hauling but for daily driving back and forth to work -
>a prime candidate if there ever was one.  It does have a few down sides....
>I expect that this truck will be just a bit over 5000 pounds when I'm done.
>That's even with the lighter front end and the weight reduction program.

I don't think that weight will be a big problem.  Don't plan on accelerating 
very fast or going up very many or very steep hills. You will suck lots of 
amps if you do.  The Red Beastie was about 5000lbs but, about half that 
weight was batteries.


>Now, here's the trick...  I would like to put a motor on the pinion so I can
>run it direct.  I got dimensions for the Kostov motor from a WEB page and
>made a model.  I believe I can mount the motor directly to the rear axle.
>Since it's a street truck, having the motor down there should not be an
>issue.

Why do you want to do that?  Read on.

>This is where I need the help from those with real world experience.  I look
>at Red Beastie (and others) and I think that it should be easy to just get
>those components because it's proven to work.  What I don't know is how much
>gear reduction trucks like Red Beastie are using.  Does a vehicle that size
>use all the gears in a manual tranny?  I'm assuming that it has a 5-sp (with
>over-drive) tranny.  If that monster starts off in 3rd, I have a very real
>chance of making it happen.  Most of the small trucks have 4.56:1 gears with
>trannies that have a 1.4:1 range before the 1:1 range.  In that case, they
>start in about 6.4:1.  I can build a diff that has a 6.5:1 ratio.  That's
>lower then the 3rd gear on a truck tranny.

6.5:1 is ok but not great.


>The down side is the top speed.  With a 6.5:1 axle, I will have a top speed
>of about 51MPH at 4000 RPM.  That kinda stinks.  At 6:1 I can have a top
>speed of about 69 MPH at 4000 but do I want the Kostov to spin at 4K for an
>hour???  Will I have any grunt off the line?  That's got to eat up power,
>right?

Isn't your top speed at about 5500-6000 rpm?  Check the curves for the Kostov 
and see if you shouldn't cruise at about 4500 rpm.

>Based on the numbers I will need a tranny or go with multiple motors and
>controllers.  If the system gets too big, I can't have regen.  I really want
>regen.

Been there...done that...got the souvenirs.  Most conversions need at least 
two gears. With one gear (the differential) you will not have a suitable gear 
for the street if you optimize your hiway cruising efficiency or you will not 
have a decent top speed if you run a high enough rpm on city streets.  
Multiple motors and controllers is a true pain in the ass. Unless you have 
lots of time, money, skill and patience...just use a single big motor and the 
transmission that comes with the truck.

>I don't see how you can learn this stuff from books.  This is some tricky
>stuff.

You probably could learn it from a book but, it's not laid out for you in any 
one book that I know of.  That's why we have this list with all kinds of 
people with all kinds of experience. My opinion is just one. There are many 
others.  I've done a single gear car, the Dualin'7...two 8" ADC motors...two 
DCP 1200A controllers...two strings of Hawker Genesis batteries.  It took 
lots of time, money, skill and patience. It works ok for me because most of 
my commute is on the highway, very little stop and go. It would be better 
with two gears. 

Your truck is going to be extra heavy. It will require a LOT OF AMPS to get 
moving with just a single gear. The strain on the caps in your controller 
will be incredible.  Thats one reason I went to two controllers. 

Rich Brown
San Jose, CA
Dualin'7