Full resolution (JPEG) - On this page / på denna sida - Pulleys - Stepped pulleys
<< 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.
PULLEYS. 351
and the slowest speed 90 revolutions, per minute. The diam-
eter of the largest step is 15 inches. What should be the speed
of the counter-shaft, and what is the diameter of each inter-
mediate step ?
Solution
:
Speed of counter = \/ 90 X 250 = 150 revolutions per
minute.
The diameter of the largest step is 15".
90 X 15 .
’
Diameter of smallest step = —j^q
— — 9 inches.
By the method as shown in Fig. 2, the intermediate diam-
eters are found to be 11" and 13". The speed of spindle will be
:
First speed = — = 250 revolutions per minute.
150 X 13 , .
Second speed = tt = 177 revolutions per minute.
Third speed = * = 127 revolutions per minute.
Fourth speed = — — = 90 revolutions per minute.
These calculations are only correct for speed, and must be
slightly modified in order to get the proper tension on the belt,
if an open belt is used ; for a crossed belt the tension is cor-
rect if the pulleys are laid out in this manner. (See page 352.)
When the number of revolutions per minute for each change
of speed is given, the diameters of the intermediate steps may,
with regard to speed, be calculated by the following formulas :
(D+ d) XJV
Dl -" "
n + N
D\= Diameter of any step on spindle.
D = Diameter of largest step on spindle.
d = Diameter of smallest step on counter-shaft.
11 — Revolutions of spindle per minute, corresponding to
the diameter D\.
N = Revolutions of counter-shaft per minute.
After the diameter of any step on the spindle is calculated,
the diameter of the corresponding step on the counter-shaft may
be obtained by subtracting the diameter of the step on the spin-
dle from the value of {D + d).
Example 2.
A lathe spindle is required to run at 40, 120 and 360 revolu-
tions per minute, and the diameter of the largest step is 18
inches. Calculate speed of counter-shaft and diameter of steps.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
