At 10:59 AM 12/15/01 +0000, Michael Hargreave Mawson wrote:
>
>Having recently replaced the gearbox and speedo cable in my non O/D
>1500, I have noticed that the readings I am getting on the speedo are
>lower for a given engine speed than hitherto.....
>Now, it would be rather handy to know whether I am doing 46 mph, 51 mph
>or 54 mph at 3000 rpm (or rather, to know by what percentage my speedo
>is reading low at a given speed). Does anyone have a formula to
>convert rpm into road speed for a UK-spec 1500?
Michael,
Measure the height of the tire - the diameter from the ground to the top.
The circumferance is: C= pi * D, where pi = 3.14....
Do you know the final gear ratio?
Distance = RPM * final ration * C.
But the easiest way is to find a spot on a road where it is marked off
in 1/4 mi., 1/2 mi etc. Some fixed distance. If you don't have anything
like that, measure off a distance on your own, with a ruler. Now travel
that distance at a fixed speed in 4th gear and measure the time it takes
to cover that distance. The longer the distance the more accurate your
results will be. V = D/ T where V = velosity (mph), D = distance in
miles, and T = time in hours.
>A corollary to the above question is, "Is there anything I can do to
>calibrate my speedo?"
In many towns there are shops that will calibrate your speedo for you,
or at least give you true readings for specific guage readings. Look in
your local phone book.
John
John T. Blair WA4OHZ email: jblair@exis.net
Va. Beach, Va Phone: (757) 495-8229
48 TR1800 48 #4 Midget 65 Morgan 4/4 Series V
75 Bricklin SV1 77 Spitfire 71 Saab Sonett III
65 Rambler Classic
Morgan: www.team.net/www/morgan
Bricklin: www.bricklin.org
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