Roller Chain - Tsubaki

Roller ChainInstallation & Maintenance4. RS Roller Chain Installation and Layout4.1 Speed Ratio and Chain LapThe speed ratio of roller chain can range up to 7 : 1 undernormal operating conditions. However, a speed ratio of 10 : 1 ispossible if the speed is very slow. Chain lap on the smallsprocket must be at least 120° and at least 90° in the case oflifting chain.˚˚In the following cases, the slack should be about 2% of thespan.(1) Vertical drive or close to vertical drive (tensioner isrequired)(2) Center distance between two shafts is greater than 1 m.Drive ChainFig. 14 Amount of chain slack˚4.2 Distance between shaftsSprockets can be separated by any distance as long as theirteeth do not touch. Optimum distance is 30 to 50 times the pitchof the chain. However, the distance should be up to 20 times thepitch of the chain when there is a fluctuating load.4.3 Amount of Slack1) It is not necessary to apply initial tension to roller chain likeV/horizontal belt drives. In general, roller chain is used with asuitable amount of slack. If roller chain is stretched too much,the oil film between the pin and bushing will be torn anddamage to the roller chain and shafts will be accelerated. Onthe other hand, too much slack will cause the roller chain tovibrate, or ride up on the sprocket teeth resulting in damage toboth the roller chain and the sprocket.˚Fig. 13 Chain Lap(3) Chain is operated under heavy load and frequent starts.(4) Chain drive is suddenly reversed.3) Roller chain tends to slightly elongate (about 0.05%) in thefirst few dozen hours of use. This elongation causesexcess slack, so the amount of slack needs to beadjusted. Use a tensioner if the system has been designedfor it. If a tensioner is unsuitable, adjust the slack bymoving the shafts.4.4 Horizontal Precision and Parallelism of the ShaftsInstallation accuracy of the sprockets greatly affects thesmoothness of the roller chain drive and also influences thewear life of the roller chain. Make sure to carry out the followingimportant steps correctly.1) Check the horizontal specification with a level. Adjust theshafts so that they are horizontal to within ± 13002) Check the parallelism with a scale. Adjust the shafts so thatthey are parallel to within ± 1 A– B300= ( ).LFig. 15 Horizontal positioning of the shafts2) Generally, the slack of roller chain should be on the lowerside. Adequate slack is calculated by moving the chain byhand in a downward direction from the center. The chain slackthat you move by hand (SS’) should be about 4% of the span(A-B) (Ex. The amount of slack when span length is 31.5”would be 31.5” × 0.04 = 1 1/4”). See figure 14.Fig. 16 Parallelism of the shaftsA-111