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# Calculation Formulas

Input Torque: T=(F*p / 2*π*i*η) + To
Input Power: P=F*V / 60*η, P=T*n/9550, V=n*p / 1000*i
Worm Gear Ratio: I=(n / 1000*V)*p
* Travel Speed: V=n*p / i

* Travel Per Turn Of Input Shaft: L=p/i
* Hand Turnning Force: HF=T/R, HF=F*p / i*R*1000
T = Input torque (Nm)
p = Screw pitch (m)
i = Gear ratio (ex. 24:1, i = 24)
η = Jack efficiency
To = Idling torque (Nm)
P = Input power (kW)
V = Screw axial speed (m/min)
n = Jack input speed (rpm)
S = Stroke (mm)
L = Travels (mm) per turn of jack input shaft
HF = Hand turning force (kg)
R = Radius of hand wheels (m)

* Total Equivalent Load Ws (N): Ws=Wmax*f1 (N)
f1: factor for driven machine
 Load Characteristic Example Factor for driven machine (f1) Uniform load, small inertia Shifting device for switches, valves and conveyors 1.0 < f1 ≤ 1.3 Moderate shock load, medium inertia Moving devices and elevators 1.3 < f1 ≤ 1.5 Heavy shock load, large inertia Heavy trolleys and railway lifts 1.5 < f1 ≤ 3.0

Equivalent Load Of Single Jack W(N): W=Ws / (Arrangement Factor*Number Of Jacks In Arrangement)
Ws: Total Equivalent Load Ws (N)
 Number Of Jacks In Arrangement 1 2 3 4 5~8 Arrangement Factor 1 0.95 0.9 0.85 0.8

Verification The Stability Of Screw: Pcr=fm*d4/L2    ensure    Pcr>W*SF (SF=4)

d = Thread root diameter (mm)
fm = Support factor
L = Distance between load supporting point and mounting point as drawing (mm)
W = Equivalent load of single jack (N)
SF = Safety factor (generally SF=4)

Verify the screw stability when the axial compression load exists. If the load is greater than the critical load, increase the sizes before calculation.
A =
2.5*104, B = 1*105, C = 2*105 Duty Circle %ED: ED=work time in one load circle / (work time in one load circle+rest time in one load circle).
Trapezoidal screw: the unit of %ED for single screw jack is 1 minute duty circle max. 40%ED; 10 minutes duty circle max. 30%ED; 60 minutes duty circle max. 20%ED.
Ball screw: the unit of %ED for single screw jack is 10 minutes duty circle max. 50%ED; 30 minutes duty circle max. 30%ED; 60 minutes duty circle max. 20%ED.
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