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Shaft supporting length Lshaft end freeJack fixed15001250100075050040030025020015010075502510251100Graph1 fixed-freelySizenf =1/450010000500020001000kNAxial Supporting length(㎜) Axial direction loadJACKE-35JB Allowable axial direction loadBall screw jack, depend on application, mustprevent effect of bucking on screw, there islimitation of apply of axial direction load. Allowable bucking-load can be calculated by thefollowing formula.W=nf・π2・E・Ⅰ・α(Eulers formula)L2W:permissible bucking-load(N)E:vertical modulus elasticity factor 2.06×105(N/㎜2)Ⅰ:minimum sectional secondary moment of screw shaft(㎜4)Ⅰ=πd464d:screw shaft root diameter(㎜)L:shaft supporting length(㎜)nf:factor by installation methodFixed-freenf=1/4(0.25)Supported-supportednf=1Fixed-supportednf=2α:safety factor0.25Example of calculationJack size JB100From the basic specification, screw shaft rootdiameter d=38㎜, minimum sectional secondarymoment of screw shaft is,Ⅰ=π×384=102353(㎜4)64Shaft supporting length L=1000(㎜)Installation method: fixed-freely nf=1/4Permissible bucking-load is:W=0.25×3.142×2.06×105×102353×0.2510002≒12993(N)=13.0(kN)In addition, in the case of permissible bucking-loadexceeds nominal capacity, the permissible axialdirection load should be limited to nominalcapacity.

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