Date:         Sat, 21 Dec 2002 14:32:09 -0800
Reply-To:     Jeffrey Schwaia <jeff@TSSGI.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jeffrey Schwaia <jeff@TSSGI.COM>
Subject:      Engine RPMs
In-Reply-To:  <127.1d9b86a0.2b345cd9@aol.com>
Content-Type: text/plain; charset="iso-8859-1"

I posted this question a week ago and didn't receive any responses so I
thought I would try again.  Any input is appreciated.

Thanks,

Jeff

-----Original Message-----
From: Jeffrey Schwaia [mailto:jeff@tssgi.com]
Sent: Friday, December 13, 2002 11:34 AM
To: vanagon@GERRY.VANAGON.COM
Subject: RPMs

The previous thread about engine RPMs and top speed got me thinking, and I
was hoping that some of you gear heads out there could confirm or correct my
calculations.

Here's what I've come up with:

GIVEN....

PI = 3.14159
MILE = 5280'

SPEED = ((((RPM /(Gear * Final Drive)) * (2 * PI * Tire Radius)) / 12 ) *
60) / MILE

Using this formula with the gear ratios (4th gear = 0.85, Final Drive =
4.83) and tire radius (~12") in my 4 speed Vanagon I come up with: ~71 mph @
4,000 RPM.  This sounds dead on for my van.

It also gives me:

~18mph for 1st gear @ 4,000 RPM
~34mph for 2nd gear @ 4,000 RPM
~56mph for 3rd gear @ 4,000 RPM

All these speeds sound about right.

Am I missing something?

I'm looking to build a freeway flyer by mixing gear ratios from different
trannys, so this formula could be of great help... if it's correct.

Cheers,

Jeff