Roller Chain Drives


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: 

  1. The roller chain, sprockets, and other components are in good condition.
  2. The sprockets are properly aligned.
  3. Provision is made for adequate lubrication.
  4. 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. 

  1. 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
  1. 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.

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