18-09-2020, 11:08 AM
(This post was last modified: 19-09-2020, 12:17 AM by Bob Culver.)
Hi Howard
According to the not high tech book The Sports Car by Campbell, rolling resitance, due mainly some cahracteristic of the tyres, increases vaguely as the square of speed, and directly with weight. For unspecified probably crossply tyres at 35 psi and an unspecified, vehicle rolling resistance per 1000 lb given as about 2 1/2 hp at 50 mph, 7hp at 100 mph.. Not clear if it includes loss thru the gearbox and diff.
The air resistance of a modern with the same cross section is only about half that of a Seven. Moderns are heavy cf cars of the late 60s so the two losses may roughly match at 50 mph, but on a Seven the wind resistance dominates
Wind hp is given as Cd x area x vel cubed (mph) all divided by 146,600
From the same Autocar article Cd Ford Pop 1948 .493, VW Beetle .48, Consul mk1 .455, BMC 1100 .453, Jowett .39, Porsche 356 coupe .333, Citroen DS .326. Open topped sports cars worse than coupe equivalent.
According to the not high tech book The Sports Car by Campbell, rolling resitance, due mainly some cahracteristic of the tyres, increases vaguely as the square of speed, and directly with weight. For unspecified probably crossply tyres at 35 psi and an unspecified, vehicle rolling resistance per 1000 lb given as about 2 1/2 hp at 50 mph, 7hp at 100 mph.. Not clear if it includes loss thru the gearbox and diff.
The air resistance of a modern with the same cross section is only about half that of a Seven. Moderns are heavy cf cars of the late 60s so the two losses may roughly match at 50 mph, but on a Seven the wind resistance dominates
Wind hp is given as Cd x area x vel cubed (mph) all divided by 146,600
From the same Autocar article Cd Ford Pop 1948 .493, VW Beetle .48, Consul mk1 .455, BMC 1100 .453, Jowett .39, Porsche 356 coupe .333, Citroen DS .326. Open topped sports cars worse than coupe equivalent.