RE: my very heavy and lossy EV LandCruiser idea... :-)

["Roger Stockton" <stockton@racalcanada.com>]

Hi Will,

I still doubt that your LandCruiser really requires that much HP
on the flat and level.  Here's some numbers I dug up on the EPA
site:

'78 LandCruiser (258cu.in./6cyl/125hp/4.11 final/4500lbs): 12.7hp@50mph
'87 LandCruiser (same as '78 except 3.70 final): 18.5hp@50mph (with A/C on)

for comparison:

'87 Suzuki Sprint (61cu.in/3cyl/48hp/4.10 final/1875lbs): 7hp@50mph (with A/C)
'87 VW Syncro 4X4 van (90hp/4.86 final/4250lbs): 20hp@50mph

As I understand it, these HP figures represent road load, so your engine
would be developing somewhat higher output.

Some time ago it was reported to the list that Uve's calculator yielded
inaccurate results when asked to model John Wayland's unusually-heavy
long-range EV, the Red Beastie.  I think Uve reported that he'd corrected
the problem, but you might want to search the archives to double-check.
I also found that the motor model used by the calculator can err significantly
when determining voltage & current for an operating point at either extreme
of the curve, although the error was greater for some motors than others.

You might double-check the calculator's predicted "Required HP" @ 50mph
on the flat with no wind, and an overall weight of 4500lbs, against the
EPA's 12.7hp value.  Then adjust the Cd &/or frontal area, or rolling
resistance (whichever you're least confident in ;^) until this prediction
is close[r].

FWIW, I just ran a "non-aerodynamic small truck" [Cd=0.46, A=24 ft^2,
weight=4500lbs, rolling resistance = 0.015, brake & steering = 0.003]
through and get 81 lbs of rolling force and 70.6 lbs of still air drag at
50mph, for a total of ~22.5hp road load. The '87 Suzuki Sprint [Cd=0.35,
A=14ft^2, weight=1875] yields ~34 lbs rolling force & ~31 lbs still air drag
at 50mph for a total of ~9.5hp, which is also a bit higher than expected,
though reducing the rolling resistance to 0.008 (+ 0.003 for brake &
steering drag) drops its 50mph HP to ~7.5.

Definitely check with Wilde EVolutions regarding the actual performance of
their Land Rover, and check the archives for info regarding John Wayland's
Red Beastie (5000lb+ Toyota pickup EV).

Cheers,

Roger.

 -----Original Message-----
From:	ev@listproc.sjsu.edu [SMTP:ev@listproc.sjsu.edu]
Sent:	Monday, November 29, 1999 6:30 AM
To:	'ev@listproc.sjsu.edu'
Cc:	Stockton@racalcanada.com
Subject:	RE: my very heavy and lossy EV LandCruiser idea... :-)

Okay listers,
	Seems I stirred quite a pot. Haven't finished reading all the
responses, so let me first cover my butt by saying I used the calculation
page off of this site:
http://www.geocities.com/CapeCanaveral/Lab/8679/ev.html  (Good site, I
probably either used it wrong or input wrong values or something!)

[snip]

Really, it does take almost 100hp or so just to
push it down the road at 65-70mph!

[snip]

	I'll write more after I finish reading where I went wrong! :-)
 -Will