General Machine Products 89300 AirStream Cable Blowing Machine - Manual (Page 37)

Page 37 of 44
3 Referring to the chart below. The “x” axis (the bottom line) represents the coefficient of friction; 1 is very
low: 10 is very high. Look along this line from left to right. Pick a vertical line that is approximately the
value of the coefficient of friction. Look vertically upward along this line. It crosses a series of angled
lines, these lines are numbered U1, U2 etc. where the vertical line crosses the angled line with the U
figure determined from step 1 make a mark on the chart. Draw a horizontal line (parallel with the other
horizontal lines on the chart) from the marked point. Where this line crosses the “y” axis (the vertical
line at the extreme left hand of the chart), make a second mark on the chart. The height of this line
represents the % of maximum clockwise rotation of the torque control. If this line is very close to the
figure 0.5 marked on the “y” axis, set the torque control potentiometer approximately one half of the
way around its maximum travel etc.
There is an alternative way of arriving at the appropriate setting for the torque control potentiometer. Do the
following.
Select a sample of the cable to be used. Pass the cable through the machine as described in the manual.
Feed the cable into the beginning of a length of sample tube (say 5 meters long). Seal the open end of the
tube. Position the torque control potentiometer at the position determined by the recommendations in this
Appendix, Start the machine. Drive the cable hard into the sealed end of the sample length of tube. The
rollers will stop turning, this is because the torque limit has been reached. Repeat this procedure, each time
turning the torque potentiometer a little further clockwise. Eventually, the cable will buckle. The setting of the
torque control potentiometer is now a little too far clockwise. Turn it back (counter clockwise) a little. This is
the optimum setting.
Torque potentiometer setting
0
0.25
0.5
0.75
1
1 10
Coeff of friction
%
o
f
m
a
x
im
u
m
r
o
ta
ti
o
n
(
c
lo
c
k
w
is
e
)
U1
U2
U3
U4
U5
U6