[Farmall] MPH per thousand revs

[Howard R Pletcher]

Your second question is the easy one.  With a 5.83 ratio, your engine
will be turning 5.83/7.33 = .795 or 80% as fast as with the 7.33 ratio.

The first question takes several calculations if it's done in a logical
fashion so you can understand how it's done.  If you have a tire data
book that gives the tire Revs per mile for your 9.00 x 20 tire or if
someone can provide that, part of the calculations can be avoided or if
you know any truck salesmen, their data books probably have tables that
give the final answer directly.

To calculate the Tire Revs per mile without a data book, you will need to
measure as closely as you can the loaded radius of the tire in inches
which I will denote as R.  The circumference of the tire in feet will be
2 x Pi (3.14) x R/12.  The Tire Revs/Mile will be 5280/Circumference.

The Engine Revs per Mile will be Tire Revs per Mile x 7.33 for the 7.33
ratio.

The Engine RPM at a given MPH will be the Engine Revs Per Mile x MPH/60
(using 60 mph reduces the calculations needed)

And finally, the MPH per 1000 RPM would be 1000 x the MPH used above /
the RPM calculated above.

All this could be put into one formula and reduced to one simple
calculation, but my brain is tired!

Assuming the radius of your tire is 20", which I think is in the
ballpark, I get 16.2 mph per thousand RPM with the 7.33 ratio and about
20.3 mph per thousand with the 5.83 ratio.

Howard

On Sat, 23 Oct 2004 12:33:41 +1000 "Robert Johnson"
<rjohnson at netcon.net.au> writes:
> I am inching towards getting my IHC ACCO on the road , but I'm 
> wondering how to calculate MPH per thousand revs , for a truck with 
> 9x20 tyres , direct drive top , and a 7.33 diff ratio.
> What would be the difference with 5.83 diff ratio ?.
> Rob Johnson.