Here's another guide for figuring ratios and speed
thanks to Glen Byrns.
>From: grbyrns@ucdavis.edu (Glen Byrns)
>To: "Robert Van Kirk"
>Subject: RE: TOP SPEED AND RATIOS
>Date: Mon, 12 Jun 2000 22:42:32 -0700 (PDT)
>
>Here's how I figured my theoretical speed at various
rpm's:
>
>Mark a spot on one rear tire and roll the car so the
mark touches the
>pavement. Mark the pavement at this point. Roll the
car forward with you in
>it (for highest accuracy) until the mark on the tire
is again on the ground.
>Mark this spot and measure between them. This is the
distance the car moves
>forward for each rotation of the axle, call it "C".
In my case, C=69 5/8" =
>69.625".
>
>With a 4.2 rear end, the drive shaft will turn 4.2
times to turn the rear
>axle one revolution. Assuming a fourth gear ratio of
1:1, then at 6K rpm,
>6000/4.2 = turns of rear tire per minute = 1428.72.
Multiply by 60 to get
>turns per hour, = 60 x 1428.720 = 85732.2
>This number times the number of inches forward for
each turn you figured out
>earlier(C)tells you how many inches forward for each
hour at 6k rpm in
>fourth. Divide by the number of inches in a
mile(63360) and you should get
>miles per hour.
>
>{(rpm/rear end ratio)x 60 x C }/ 63360
>
>So for a 4.2 rear end, 69.625 inches per turn of
tire, fourth gear:
>(6000/4.2) x 60 x 69.625 / 63360 = 94.18 mph, at 5k
rpm = 78.49mph
Tired of spam? Yahoo! Mail has the best spam protection around
|