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[Spridgets] Bentley-RR Trivia: was calculating speed

To: Spridgets <Spridgets@autox.team.net>
Subject: [Spridgets] Bentley-RR Trivia: was calculating speed
From: Kitterer Bob <bkitterer@mac.com>
Date: Tue, 21 Oct 2008 09:57:36 -0700
The placards on the Bentley and RR at the Gilmore Car Museum have  
bothered me for some time and having opened my mouth here it forced  
me to do some research which I should have done long ago.  I should  
mention that the Gilmore is a great museum located in SW Michigan.

The HP question:  From physics a HP is a HP is a HP - - - well not  
quite.  In Britain the RAC (Royal Automobile Club) computed  
automotive HP by an equation of their own.  This apparently work for  
early cars and indeed it was used for tax purposes hence taxable  
HP.    It continued in use into the 1960's but the RAC had made three  
assumptions which did not hold up over time.  There is an  
explanation, with the equations, at  http://www.designchambers.com/ 
wolfhound/wolfhoundRACHP.htm  It would be fun to plug in some numbers  
from current cars just to see how HP comes out in RAC HP but I do not  
have time for that now.

The following information came from various sites which do not all  
agree with each other but these were not "production line" cars so  
some variance is expected.

Bentley Speed Six (supercharged perhaps)  4850 lbs, 180 to 200 hp,  
top speed 84 to 125 mph.

RR Phantom II Sports Coupe, 5485 lbs, 43.3 RAC HP, 120 BHP, top speed  
92 mph.

Almost all Phantom II's were custom bodied but seem consistent  
mechanically with exception of wheel base.  The Bentley seems only  
slightly more consistent.

Bob Kitterer

1960 Austin Healey Sprite (Mk IV in disguise)
1966 Austin Healey Sprite Mk III (Trevor) - still in boxes
2000 Miata Special Edition




On Oct 20, 2008, at 6:36 PM, Billy Zoom wrote:

> I doubt that the Bentley weighed anywhere near as much as the  
> Rolls, but you
> can't judge anything by the top speed.   I'm sure the Rolls was  
> geared a lot
> taller, and I'll bet that was taxable horsepower, which is  
> calculated  by
> the area of the tops of the pistons and has nothing to do with power.
> Bentley's were race cars. I'll bet it got to 95 a lot quicker than an
> overweight cruiser like a Rolls.
> James Bonds Bentley was always credited with doing over 100 when he  
> wanted
> it to.
> BZ
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