| To
obtain maximum service-life and efficiency from a chain drive, it is necessary
that certain precautions in installation be taken.
Chain drive installation
is relatively simple and good results may be obtained when the following
conditions are met:
-
The roller chain, sprockets,
and other components are in good condition.
-
The sprockets are properly aligned.
-
Provision is made for adequate
lubrication.
-
The chain is correctly tensioned.
Condition
of Components
Shafting, bearings, and foundations
should be supported rigidly to maintain the initial alignment. Roller chain
should be free of grit and dirt. Wash chain in kerosene when required.
Relubricate!
Drive
Alignment
Misalignment results in uneven
loading across the width of the chain and may cause roller linkplate and
sprocket tooth wear. Drive alignment involves two things: parallel shaft
alignment and axial sprocket alignment.
-
Shafts should be parallel and
level. This condition may be readily checked by the use of a feeler bar,
and a machinist's level. It there is axial movement of the shaft (as in
the case of an electric motor), lock the shaft in the normal running position
before aligning the sprockets.
Aligning
Shafts
-
Sprocket axial alignment can
be checked with a straight edge which will extend across the finished sides
of the two sprockets. Normally, it is good practice to align the sprockets
as close to the shaft bearing as possible. For long center distances, use
a taut cord, or wire long enough to extend beyond each of the sprockets.
|
Aligning
Sprockets
Installing
the Chain
Recheck all preceding adjustments
for alignment and make certain all setscrews, bolts and nuts are tight.
Fit chain around both sprockets and bring the free ends together on one
sprocket for connection, The sprocket teeth will locate the chain end links.
Install the connecting link, and connecting link coverplate, and the spring
clip or coffer pins. On larger pitch chains or heavy multiple strand, it
may be necessary to lock the sprockets for this operation. When press fit
coverplates are used, be careful not to drive the plate on so far as to
grip the roller links. Stiff joints can result if this is done. On drives
with long spans, it may be necessary to support the chain with a plank
or bar as the connection is made.
Chain
Tension
Check chain tension to be
certain the slack span has 4-6% mid-span movement in horizontal drives
and 2-3% in vertical drives.
Recommended
Possible Mid-span Movement AC
Tangent Length Between Sprockets
| Drive
Center-Line |
5" |
10" |
15" |
20" |
30" |
40" |
60" |
80" |
100" |
| Horizontal
to 45 degrees |
.25" |
.5" |
.75" |
1" |
1.5" |
2" |
3" |
4" |
5" |
Vertical
to
45 degrees |
.12 |
.25 |
.38 |
.5 |
.75 |
1 |
1.5 |
2 |
2.5 |
|
AC
= Total Possible Mid-Span Movement
Depth
of Free Sag = .866 AB, approximately.
|
