Transmissions by Cross+Morse

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


Page 72 of Transmissions

`hv chain selection cross+morse there are seven good reasons to use hv in your design hv transfer cases provide weight and cost savings because 1 2 3 4 5 6 7 power transmission solutions te l fewer shaft and bearings are required lighter loads on shaft bearings chain bearing loads are compressive placing case in compression unlike gear forces which are tensile +44 121 360 0155 hv cases are lighter as compressive loads mean thinner sections can be used centre distance is less critical and more flexible than required by gear and belt drives elasticity of hv chain accommodates normal thermal expansion and helps `cushion the drive simplified design results in a positive cost saving `hv drive selection design of a `hv chain drive involves correct selection of chain and sprockets combined with correct casing design and lubrication system the power rating tables opposite giving power ratings per inch width of chain enable selection of chain with drives operating under ideal conditions of smooth power source and load to use these tables for other drives involving shock loads the actual power must be modified by a service factor to obtain the design power which can then be related to the tables service factors s.f type of load smooth moderate shock heavy shock int comb eng hydraulic drive 1.0 1.2 1.4 electric motor 1.0 1.3 1.5 int comb eng mechanical drive 1.2 1.4 1.7 fax +44 121 325 1079 `hv drive selection 1 2 3 4 5 determine the r.p and diameter of the high speed shaft .m determine the total power to be transmitted from application detail determine proper service factor from table refer page 7 in roller chain selection for machine types establish design power by multiplying total power to be transmitted by the service factor design power kw motor power s.f select the chain pitch and width and number of teeth in the small sprocket from the power rating tables a for quiet and smooth drives use sprockets 25 teeth or more b be sure the small sprocket will accommodate the high speed shaft diameter as a guide with steel sprockets pitch circle diameter should be minimum twice shaft diameter pcd zp c email if the high speed shaft diameter exceeds the maximum bore in the selected small sprocket it will be necessary either to increase the number of teeth in the sprocket or select the next larger pitch chain 6 determine the required drive ratio rpm high speed shaft rpm slow speed shaft ratio 7 multiply the number of teeth in the small sprocket by the ratio to obtain the number of teeth in the large sprocket 8 to determine chain length and centre distance refer to page 9 centre distance and sprocket combination must always provide an even number of pitches of chain for fixed centre drives it is recommended to use centre distance tables hv drives should always be installed with a slight preload and to provide this the actual centre distance is obtained by increasing the theoretical by 0.07 manufacturing tolerances should always be on the plus side further advice on centre distance requirements can be obtained from cross+morse engineering 9 as more than one pitch of chain could be selected for most applications consideration should be given that the shaft centre distance should never exceed 60 times pitch and that large pitch narrow width selections are better for shock loading and commercial considerations however small pitch chains operating on sprockets with high numbers of teeth give smoothest drives with minimum noise level whilst preliminary drive selection can be made from the tables it is recommended that all `hv drives be referred to cross+morse engineering department for final approval 10 the design and manufacture of the sprockets is critical for correct drive operation general dimensional details are provided on page 75 sprockets with 35 teeth or less are best manufactured from low carbon alloy steels with teeth carburised and hardened larger sprockets can be manufactured from medium carbon steels or mechanite castings and induction or flame hardened teeth must be generated to the special involute form for smooth drive operation for 1:1 drives it is preferable to use even tooth sprockets for smooth drive but on all reduction drives it is best to use odd number teeth in small sprocket for maximum drive life idler sprockets should never be used cross+morse can offer the full range of `hv sprockets manufactured to meet customers requirements if not specified through bore length hub diameter and all manufacturing tolerances will be morse standards materials and tooth hardness will always be to morse specification 72 cd contents catalogue selection index transmissions index back next