On Fri, 4 Oct 1996, David Rupert pondered 'what's up with this?':
> > ...What the heck is hp? One of the cars in the article was described
> > as, "A 10.5 hp model featuring a 48 bhp engine", or something to
> > that effect. I'm assuming that it is NOT some arcane method of
> > measuring horsepower....
On Fri, 4 Oct 1996, John Lupien wrote:
> Not from "over there", but I've had this explained to me before.
> The 10.5hp rating is a "tax rating", which is based on a formula
> that includes bore, stroke, and a rather antique notion of specific
> power. It has nothing to do with actual horsepower.
And I will add my own $.02 worth. To to calculate the "treasury rating"
(taxable horsepower), the RAC formula is as follows:
2
(bore in mm.) x number of cylinders
hp = ------------------------------------
1613
This is from Culshaw & Horrobin's "The Complete Catalogue of British Cars."
At one point, this formula helped lead to some fairly long-stroke
engines in LBCs. The "rating" was gone after WWII if not previous to
that, but the "naming convention" remained for some time to come, hence
Austin 7s, Standard Eights and Tens (and Triumph 10s), etc.
--Andy
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
* Andrew Mace e-mail: amace@unix2.nysed.gov *
* *
* Mrs Irrelevant: Oh, is it a jet? *
* Man: Well, no... It's not so much of a jet, it's more your, er, *
* Triumph Herald engine with wings. *
* -- The Cut-price Airline Sketch, Monty Python's Flying Circus *
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
|