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Equation for actual speed

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Offline LawDog

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Equation for actual speed
« on: July 13, 2005, 06:31:41 AM »
OK, i searched but can't find it.  There's some equation that tells us how fast were actually going right?  I'm on 33's with stock 3.73's and my speedo says 60mph.  How fast am I really going?
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Offline zaggy

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Re: Equation for actual speed
« Reply #1 on: July 13, 2005, 06:49:30 AM »
RU ready

     Tire diameter (33") divide by 12= (2.75')

     2.75' X 3.14= tire circumfrence (8.635')

     8.635 X 1000rpm= (8635')

     8635 divided by gear ratio in 4th (1:1) (3.73)=2315' per minute

     2315' per minute divided by feet in a mile (5280) = .438

     .438 X 60 mph (mile a minute)= 26.3 miles per hour per 1000 rpm

      60mph divided by 26.3= 2280 rpm for 60mph

     For 5th you have to adjust for the od ratio effect on the rear end ratio
     (5th ratio X 3.73= actual ratio)

     And you can mix and match the formula to figure out darn near
     whatever you need.

     Example: I use the same formula to work out propellor tip speed


    Zag

     
     
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Offline Cwkick

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Re: Equation for actual speed
« Reply #2 on: July 13, 2005, 07:02:16 AM »
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Offline zaggy

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Re: Equation for actual speed
« Reply #3 on: July 13, 2005, 07:47:05 AM »
Well if I had know that I could have sved a math lesson

Zag
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Offline wildgoody

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Re: Equation for actual speed
« Reply #4 on: July 13, 2005, 08:20:54 AM »
What's the 12 Zaggy ?
I thought Pi * Dia = Cir ?
Or is my Geometry rusty

Wild
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Offline zaggy

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Re: Equation for actual speed
« Reply #5 on: July 13, 2005, 08:24:38 AM »
Converting tire diameter from inches to feet.....sorry should have explained better
12=12"

Zag
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Offline wildgoody

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Re: Equation for actual speed
« Reply #6 on: July 13, 2005, 08:28:57 AM »
Dohh, I should of cought that   :-[

I convert that later, I find whole inches
are a little easier to figure in my head
than decimals

Wild
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Offline zaggy

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Re: Equation for actual speed
« Reply #7 on: July 13, 2005, 08:30:04 AM »
I'm gettin old...I don't even try to figure in my head no more

Zag
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Offline wildgoody

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Re: Equation for actual speed
« Reply #8 on: July 13, 2005, 08:37:30 AM »
Well I let the Calculator figure Pi
the rest I can get close or estimate
unless it's a critical thing

Wild

Here is an easy way to quickly
figure an engine's displacement,
and I always use the Calc for these

bore*bore*stroke*3.1417 and you get
a long #, or you can multiply by .0031417
and the decimal comes out at the right spot

example 75*75*90*3.1417 = 1590485.625
the stock displacement of the SideKick 1.6L engine
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Offline Bobzooki

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Re: Equation for actual speed
« Reply #9 on: July 13, 2005, 09:20:04 AM »
Quote from: wildgoody on July 13, 2005, 08:37:30 AM
Well I let the Calculator figure Pi
example 75*75*90*3.1417 = 1590485.625

Oh, man, you'll never get a good answer using 3.1417, everybody KNOWS Pi is more like 3.1415926, right?   ;D ::) ;)
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Offline mrfuelish

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Re: Equation for actual speed
« Reply #10 on: July 13, 2005, 02:02:03 PM »
the best is GPS  turn it on and drive.  ;D
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Offline wildgoody

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Re: Equation for actual speed
« Reply #11 on: July 13, 2005, 08:03:47 PM »
Well Bob, it's really more like
3.1415926535897932384626433832795
but I just get too tired typing it all in
 ;)

Bob PM me, I need your address, I still
have your 5mm allen wrench, I look for you
before I left, but I couldn't find your campsite

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Offline mrfuelish

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Re: Equation for actual speed
« Reply #12 on: July 14, 2005, 12:01:04 AM »
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Offline wildgoody

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Re: Equation for actual speed
« Reply #13 on: July 14, 2005, 09:55:22 AM »
 :o

I have other things to do besides
remember Pi to the 83,000 digit

 ;)
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Offline LawDog

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Re: Equation for actual speed
« Reply #14 on: July 14, 2005, 09:59:12 AM »
Japan Today later printed a retraction.  He had really eaten 83,431 pieces of pie to set that Guiness record. ;D 8)
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