Jim,
I know I'm not the David you asked, but my two cents worth says you're
probably correct. Centrifugal force would have to deflect the tire diameter
outward as seen on rail dragsters during the burnout. Would it be enough on a
belted street tire to increase the actual rolling diameter or would the weight
of the car and strength of the tire structure tend to negate the effect? It's
beyond my ability to calculate, for sure. If the diameter does increase, it
would definitely make the car's actual speed higher than the indicated (or
mathematically derived) speed.
- David Booker
'71 Midget
Long Island
--- On Sat, 10/18/08, Jim Johnson <bmwwxman@gmail.com> wrote:
From: Jim Johnson <bmwwxman@gmail.com>
Subject: Re: [Spridgets] calculating speed
To: "David Lieb" <dbl@chicagolandmgclub.com>
Cc: "Spridgets" <spridgets@autox.team.net>
Date: Saturday, October 18, 2008, 11:37 AM
Hey, David....
My engineering background tells me Dean and Duncan are on to something.
There will definitely be some tire circumference growth which changes the
tire diameter making it larger at higher speeds.... Where am I going wrong
with that thinking? ;-)
Cheers!!
Jim
On Sat, Oct 18, 2008 at 6:13 AM, David Lieb
<dbl@chicagolandmgclub.com>wrote:
> Go to:
>> http://bgsoflex.com/auto.html
>> Then scroll down on the left to rpm range program...
>> Here is a sample output. The key item is to go measure your tire
>> diameter.
>>
>
> Since you already measured circumference, divide it by pi (3.1415) to get
> 20.69 as a diameter.
> with the 4.55 diff at 7000, that site indicates 95mph
> with the 4.22 diff at 7000, that site indicates 102mph
>
> Input Parameters Are the Following:
> Differential Gear = 4.55 to 1
> Transmission Gear = 1.00 to 1
> Tire Diameter (Inches) = 20.69
> Engine RPM = 7000
> Computation Results:
> Computed Vehicle MPH is 95
>
> Input Parameters Are the Following:
> Differential Gear = 4.22 to 1
> Transmission Gear = 1.00 to 1
> Tire Diameter (Inches) = 20.69
> Engine RPM = 7000
> Computation Results:
> Computed Vehicle MPH is 102
> You are subscribed as bmwwxman@gmail.com
>
> http://www.team.net/archive
>
> http://autox.team.net/mailman/listinfo/spridgets
>
--
Cheers!!
Jim
You are subscribed as tncarnut1@yahoo.com
http://www.team.net/archive
http://autox.team.net/mailman/listinfo/spridgets
Tired of
spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
_______________________________________________
Support Team.Net http://www.team.net/donate.html
http://www.team.net/archive
http://autox.team.net/mailman/listinfo/spridgets
|