Winch Sizing
As a general guide to sizing the right winch for the job, the following detail
may be of help:
Load
Calculate the total weight of all the loaded railcars to be moved simultaneously.
For example, if four loaded railcars, each weighing 85 tons are to be moved together,
the total load will be four times 85 tons, for a combined weight of 340 tons.
Rolling Resistance Under
Ideal Conditions
Resistance to rolling is influenced by the wheel journals, type of lubrication used
and the ambient temperature. Assuming the railcars are to be moved along a straight,
level and well-maintained track, select the running line pull for the lowest anticipated
temperature, using Table 1.
Example: If the lowest anticipated
temperature is 32°F, the required running line pull from Table 1 will be
15 lbs/ton. Multiply the total weight of the railcars 340 tons by 15 lbs/ton
and the total running line pull becomes 5100 lbs.
Table 1
|
Temperature |
More than
32°F |
Less than
32°F |
Less than
0°F |
Less than
-20°F |
|
Running Line Pull (lbs/ton) |
12 |
15 |
20 |
25 |
Track Gradient
For each one percent gradient a rise of one foot for every 100 feet of track
the running line pull must be increased by 20 lbs/ton.
Example: If the track has
a 1.5% grade, the additional running line pull is 20, multiplied by 1.5, or 30 lbs/ton.
The new running line pull is the original 15 lbs/ton plus the 30 lbs/ton adjustment
for grade or 45 lbs/ton. The new running line pull is now calculated by multiplying
45 lbs/ton by the 350 tons of railcars for a total of 15,300 lbs.
Diagram 1
Track Curvature
To overcome the effects of wheels binding against rails on curved sections of track,
running line pull must be increased.
Track curvature is expressed
in terms of radius or degree of curvature. When this information is not available,
the chordal factor can be easily measured. Simply stretch a 50-foot tape along the
inside of the curve and measure the distance 'A' in Diagram 1.
Select the appropriate additional
running line pull from Table 2 using either radius, degrees of curvature or chordal
factor. (Interpolation for a measure of curvature is not shown.)
Table 2
Radius
(ft) |
Degree of Curvature
(degrees) |
Chordal
Factor A
(inches) |
Additional
Running Line Pull
(lbs/ton)
|
|
1146 |
5 |
3.50 |
3.75 |
|
573 |
10 |
6.50 |
7.50 |
|
383 |
15 |
9.75 |
11.25 |
|
288 |
20 |
13.00 |
15.00 |
|
231 |
25 |
16.50 |
18.75 |
|
193 |
30 |
20.00 |
22.50 |
|
166 |
35 |
23.50 |
26.25 |
|
146 |
40 |
27.00 |
30.00 |
Example: Chordal factor
A was found to be 6.5 inches. The additional running line pull from Table 2 is 7.50
lbs/ton. Now the running line pull has increased from 45 lbs/ton to 52.5 lbs/ton.
Again, multiplied by the 340 tons of railcars, the total running line pull is 17,850
lbs.
Track Conditions
If track conditions are substandard soft ballast, uneven or deteriorating ties
or debris on the track additional running line pull will be needed. Since the
condition of substandard track can vary considerably, Jeamar recommends that line
pull be measured with a dynamometer.
|