Transmissions by Cross+Morse

More catalogs by Cross+Morse | Transmissions | 88 pages | 2009-08-24


Page 6 of Transmissions

roller chain drive design cross+morse · shafts centre distance for optimum chain life shaft centres within the range 30 to 50 times chain pitch should be used refer to page 9 drives with centres up to 80 times pitch will perform satisfactorily providing adequate adjustment of chain tension is available for very long centres consideration should be given using two stage drive with idler or alternatively for lightly loaded slow speed up to 1 m/s drives supporting both strands of chain on chain guides these drives suffer high rates of wear due to the number of sprockets involved and combined with necessary long chainsolutions power transmission length require inclusion of an idler with a lot of adjustment within the drive sometimes a number of adjustable idlers are used te l +44 121 360 0155 long centre drive using supporting guides light live roller conveyor drives can be powered using a single loop of chain with sprockets running on top the chain should be supported on plastic chain guide to maintain constant contact with sprockets alternatively where rollers are well spaced idler sprockets can be positioned opposite between each pair of sprockets this increasing the angle of contact on the driven sprockets the small contact between driven sprocket and chain requires that torque on any one roller should never exceed 15 of rated power for the drive chain speed should never exceed 1 m/s an advantage of this layout is that the driven sprockets and shafts can be easily removed · centre distance adjustment when designing a chain drive ability to adjust the position of one shaft to compensate for chain wear should be included ideally equal to a minimum of 2 pitches of chain if this is not possible correction for chainwear can be achieved by the incorporation of adjustable idler or sprung loaded tensioner on the slack strand of the chain automatic adjustment for chain wear is recommended for drives with an inclination of more than 60° to the horizontal see sketch idler or tensioner sprockets should be applied to the outside of the unloaded strand of the chain close to the driven sprocket but allowing at least 5 pitches free length of chain between idler and sprocket at all times ideally at least 3 pitches of chain should engage with idler sprockets automatic tensioners cannot be used on reversing drives or applications where high torque reversals could be encountered idlers also are not generally suitable for reversing drives fax +44 121 325 1079 powered live roller conveyors usually have the rollers connected by coupled simple drives often with the use of double simple sprockets to keep chain loads to a minimum it is preferable to connect input drive to centre roller this keeping wear to a minimum a simple chain drive operates with an efficiency of 98 therefore an allowance of 2 should be made for power loss in each loop of chain in determining chain selection and drive motor requirements multi-shaft drives standard roller chain loses some of its performance capability at elevated temperatures and also is more prone to corrosion problems hardness of pins and bushes become reduced affecting operating life at temperatures over 170°c chain drive capacity is reduced and this must be included in drive selection by applying the factor f3 from the table below standard chain should not be used in temperatures over 250°c for elevated temperature applications it is preferable to select stainless steel chains with standard series suitable on applications to 325°c and 300 series chain for temperatures to 500°c stainless steel chain has lower wear resistance at all temperature and therefore factor f3 in table blow should be applied when making chain selection · elevated temperature and stainless steel chains email factor f3 stainless and elevated temperature typical serpentine drive drive to 7 pairs rollers in film process m/c roller chain is often used to connect a number of shafts within one drive three arrangements are most common serpentine drives have the chain laced through a number of sprockets so that some can be driven contra-rotation to the others temperature -5 to 170°c 170 to 200°c 200 to 250°c 250 to 325°c 325 to 425°c 425 to 500°c standard roller chain stainless roller chain 300 series stainless 1.0 1.35 2.0 ­ ­ ­ 2.0 2.3 2.6 2.75 ­ ­ 2.6 2.75 2.9 3.2 4.0 5.0 useful formulae the following formulae can be used in the design and selection of chain belt drives power kw torque nm x rev/min 9550 belt/chain speed m/sec zxpxr.p.m 60,000 6 z no teeth in sprocket or pulley p belt/chain pitch mm further design formulae and conversion tables are provided in the catalogue appendix cd contents catalogue selection index transmissions index back next