Manual screw jack detailed informations:

A hand wheel is a convenient solution for manual operated a screw jack or screw jack systems. When using screw jacks in intermittent positioning applications. Hand wheels are available in a range of diameters from 5 to 12 inches and customized follow clients' need.
Hand Wheels do not include a brake. Hand wheels are not recommended for use with ball screw jacks. When using hand wheel with a screw jack that can backdrive an additional locking mechanism may be required to prevent "creep".

For precise position display, a range of digital counters are available for use with screw jacks. These digital counters measure the rotation of the input shaft and display corresponding position in a counter window. The display value per input shaft revolution is variable and is achieved through a series of gear reductions configured to accommodate different jack ratios, lifting screw pitch and travel distances.

Human Force Calculation Formulas:
HF=(G*P)/(R1*R2)
HF:human force (kgs)
G :working load (kgs)
P :screw pitch (mm)
R1:gear ratio
R2:hand wheel radius
Example, working load 50 kgs,the fast speed,manual operated.
Check specification table, 50 kgs with manual operated, use the smallest model RN-0.5T(pitch=5mm) enough. Fast speed 1/5.Usually,RN-0.5T jack with 5"(125) diameter hand wheel. How much about human force?
HF=(50*5)/(5*62.5)=0.8 kgs.

Every model has three speed ratios.
RN-0.5T,RN-1T,RN-2T,RN-3T,RN-5T,RN-10T and RN-15T
Fast speed: 1 turn 1 mm travels
Mid  speed: 1 turn 0.5 mm travels
Low  speed: 1 turn 0.25 mm travel
The larger models screw jacks are not suitable for manual operated.

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