Full resolution (JPEG) - On this page / på denna sida - Mechanics - Calculating sizes of pulleys - To calculate the speed of gearing - Efficiency of machinery
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
322 SPEED OF MACHINERY.
TO FIND THE NUMBER OF REVOLUTIONS OF THE COUNTER
SHAFT.
Rule.
Multiply the diameter of pulley on the main shaft by its
number of revolutions per minute and divide this product by
the diameter of pulley on the counter-shaft, and the quotient is
the number of revolutions of the counter-shaft per minute.
Example.
The pulley on a main shaft is 24 inches in diameter and
makes 150 revolutions per minute, and the pulley on the counter-
shaft is 15 inches in diameter. How many revolutions per
minute will the counter-shaft make ?
24 X 150
Number of revolutions = = 240 revolutions per minute.
15
F
To Calculate the Speed of Gearing.
In calculating the speed of gearing, use the same rules as
for belting, but take the number of teeth instead of the
diameter.
Example.
The back gearing on a lathe consists of a gear and pinion
of 8 pitch, 96 teeth and 32 teeth, and the other gear and pinion
are 10 pitch, 120 teeth and 40 teeth. How many revolutions will
the cone pulley make while the spindle makes one revolution?
Solution
:
Cone pulley makes = -—_ = 9 revolutions.
y
32 X 40
Efficiency of Machinery.
Divide the energy given out by a machine by the energy
put into the same machine ; multiply the quotient by 100, ancl
the result is the per cent, of efficiency of the machine.
Example.
A dynamo requires 15 horse-power, but the electrical power
given out is only 12 horse-power. What is the efficiency?
Solution
:
Efficiency = — X 100 = 80%
15
A steam engine is to develop 60 horse-power net. What
will be the gross horse-power if the efficiency is 75% ?
Solution
:
Gross power = — = 80 horse-power.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
