# Formula for speed!

Discussion in 'General Questions' started by pianoman8t8, Feb 3, 2007.

1. ### pianoman8t8Guest

FORMULA FOR SPEED!!!

Speed (MPH) = a X (b/c) X (d/e) X (f x g) X 60 / 12 / 5280

X = times (multiply)
/ = Divide by...
the paranthesis aren't completely necessary, but help add organization to the problem for those of you who remember enough of Algebra to know what they mean. They mean that you do the process inside the paranthesis first. so let's say a X (b/c) ..... you'd divide b by c, then multiply by a ...... know what i mean?

a = RPM of engine
b = #teeth of first gear in gearbox where clutch is (smaller gear)
c = #teeth of second gear in gearbox (larger gear)
I beleive the smaller gear is 20 teeth and the larger gear is 83 teeth
d = #teeth of chain sprocket on engine (usually 9 or 10 teeth)
e = #teeth of chain sprocket on wheel
f = diameter of wheel
g = 3.14 which is equivelant to pi (to get circumference of wheel)
60 is for min. in an hour, 12 is for inches in a foot, 5280 is feet in a mile. Hope this works for you.

-pianoman

2. ### jwibbityGuest

my brain just fell out and plus i dont know a couple of the dimensions

3. ### pianoman8t8Guest

also, i figured about a 20 to 1 ratio from the RPM of the engine to the RPM of the tire. so if you take one twentieth (1/20) of let's say 6000, you get 300 (RPM). if you multiply 300 by 81" (roughly the circumference of a 26" tire in inches) then multiply by 60 (minutes) then divide that number by 12 (inches per foot) then divide again by 5280 (feet in a mile) then you get roughly 23 MPH, whoch sounds about right.
but anyway...

-pianoman

4. ### WheelsGuest

I will scribble this down on parchment and see what happens.

wheels

5. ### BarretGuest

pianoman - dude, that is so cool! I'll try this formula out in a few days, and it won't be any problem for me because I'm currently in Math 160 (Calculus) in college.

6. ### pianoman8t8Guest

oh, yes, the joys of college. I'm currently in college also. it's very nice to get outta the house during the week.

-pianoman

7. ### srdavoActive Member

hey Augi,
does this remind you of anything?
dave

8. ### sideshowsideswipeGuest

I get it I just don't want to do math stupid lazy brain... 8)

9. ### GuestGuest

Here is my personal formula for speed:

Full throttle going down a steep hill. It has never failed me yet.

11. ### RLKGuest

Math is hard. :lol:

Ya got a tachometer I can borrow?