Formulas
& Conversion Factors
formulas.htm-72
©
Copyright, 2011, R. Fleischer
1. Torque:
Nm x 0.7376 = ftlbs
ftlbs x 1.356 = Nm
Mkp x 7.23 = ftlbs
inch-ounces = 141.6 x Nm
Mkp x 9.81 = Nm
2. cubic inches x 16.39 = cc
liters x 61.02 = cubic inches
cubic inches ÷ 231 = gallons
Imperial gallon x 1.2 = U.S. gallon
mpg x 0.354 = km/l
km/l x 2.825 = mpg
3. psi x 27.68 = inches of water
inches of water x 1.868 = mm of mercury
Kpa x 0.145 = psi
bars x 14.5 = psi
4. Km x .621 = miles
one Km is approximately 5/8th of a mile.
5. (F°-32) x .56 = C°
(C° x 1.8) + 32 = F°
6.
7. Electricity:
resistance in ohms = (voltage ÷ by amperes)
The symbol for ohms is the Greek omega
power in watts = amperes x voltage.
7 46 watts = one horsepower.
From the above, you can find any unknown.
8. You can generally interchange the following wrench sizes:
11 mm and 7/16 inch
13 mm and 1/2 inch
16 mm and 5/8 inch
19 mm and 3/4 inch
27 mm and 1-1/16 inch
9. velocity in mph x 1.467 = feet per second
kph x 0.621 = mph
10. (horsepower x 5252) ÷ by rpm = torque in ftlbs.
11. MPH = (rpm x rolling radius of the driven tire in inches) ÷
by (168 x the overall gear ratio)
12. Gasoline weighs 6 pounds per U.S. gallon.
Oil weighs 7.5 pounds per U.S.
gallon
Kerosene weighs 6.7 pounds per
U.S. gallon
Water weighs 8.4 pounds per U.S.
gallon
***NOTE: The U.S. gallon is 3.785 liters; but the IMPERIAL gallon
is 4.546 liters. In both systems 4 quarts are a gallon, but the
quarts are different sized! For those of you into beer barrels,
the British one is 36 gallons, the U.S. one is 31.5
gallons.
13. Bullshit is seldom given any
weight
14. 1 mm = 0.03937 inches
1 inch = 25.4 mm
miles x 1.609 = km
km x 0.62 = miles
15. Gas velocity through a port in ft/sec = (piston speed in
ft/min ÷ by 60) x (diameter of piston squared ÷ by
the port diameter squared).
16. Mean gas velocity through the valve in ft/sec = (piston speed
divided by 60) x [diameter of piston squared], ÷ by (the valve
diameter at throat x lift of valve x pi)
17. The formulas to calculate gas flow, resonance, reversion,
intake and exhaust diameters and flow and reversion are available
from me.
18. Modern internal combustion engines produce APPROXIMATELY 2
horsepower-hours per pound of fuel consumed. If one uses fuel
weighing 5.6 pounds per gallon, then you can expect 11.2
horsepower-hours per gallon, which is 8355 watt-hours.
19. TACH, MPH, RPM, AND SPEED:
Measure the radius of the
tire, bike on tires, not stands, you and passenger seated on
bike, bike pointed straight ahead, and balanced straight up,
buddy measuring the CENTER of axle to the floor, multiplied by 2,
multiplied by pi, will give the circumference,
close enough to
the actual in-use number. The formula for determining the
relationships, suitably simplified is as follows:
Let T = the tach reading
Let M = miles per hour
Let C = circumference in INCHES
Let S = small number in the rear end teeth ratio
Let L = large number in the rear end teeth ratio
Example: you have 37/11 gears (which is 3.36:1 btw). S = 11;
and L = 37
THEN, multiply the following: (T)(C)(S)
Divide that result by (1584)(L)
The result is M
Rearrange this formula to find any of the values, like you
learned in jr. high school in beginning algebra.
Practical example:
Most early BMW's came with a 4.00 x 18 rear tire. That tire is
likely, even if you have an oversize 120-90 x 18, to measure
about 80 inches in circumference.
The formula will show that for a 70 mph speed, the tach should be
reading 4667 rpm.
20. PISTON TRAVEL VERSUS CRANKSHAFT ROTATION IN DEGREES;
This simplified information is normally used for 2 stroke engine
timing purposes, but has some uses on airheads.
When measuring the piston movement per degree of crankshaft
rotation, the distance the piston moves is a cosine function.
Take the manufacturer's published stroke distance, multiply by
the cosine of the number of degrees, to equal the
piston stroke
distance. You can use your calculator, or a table of cosine
function. It is easy to transform the results into markings on
the flywheel.
I previously published the actually more
complex trigonometry and confused the heck out of folks.
So, here are some places to get that information, by simply
plugging information into a table; which will then do the
calculating for you.
http://www.dansmc.com/mc_software2.htm
21. Oil viscosity is often given in cST
or SUS....and seldom are both given for the same
product. Here is how to convert one to the other:
IF SUS is between 32 and 100: cST = 0.226
x SUS - 195/SUS
IF SUS is over
100:
cST = 0.220 x SUS - 135/SUS
For
very considerably more on oil, see my oil articles, and
regarding viscosities of particular oils, see my
viscosity.htm article.
Revisions:
04/11/2003: add .htm title; edit a few places for clarity
and renumber some items/splitting them first.
04/29/2003: expand #2; remove note in blue at top; clarify
minor details throughout
05/07/2003: add #19
09/27/2003: add a few conversions
12/23/2006: add #20
12/24/2006: add #21
01/27/2008: merge #6 into #20, and edit same
04/26/2010: remove a link
05/31/2022: clean up
©
Copyright, 2011, R. Fleischer