Flexible shafts provide rotary power transmission along curved or adjustable axes. They are used in a wide variety of remote control, valve actuation, and power transmission applications.
There are two basic types of flexible shafts:
- Unidirectional shafts rotate in a clockwise or counterclockwise direction as viewed from the motor or drive-end of the shaft. They are used for power transmission along non-linear axes in industrial automation, heavy-duty, and specialized applications such as agricultural equipment, speedometers, dentistry, woodworking, and jewelry tools.
- Bidirectional flexible shafts can be rotated in either direction or reversed. They are well-balanced in both directions and suitable for cyclic applications. Some flexible shafts are corrosion resistant or can withstand environmental contaminants such as dust, fluid, and oil. Others have a casing around the shaft for protection and safety.
Specifications for flexible shafts include
- Maximum speed
- Torque capacity
- Minimum bend radius
- Length, stiffness
- Torsional deflection
- Axial stretch
Maximum speed is the maximum, rated rotational speed under load. Units of measure include
- Revolutions per minute (rpm)
- Revolutions per second (rps)
- Revolutions per hour (rph)
Some Important Measurements for selection are:
- Torque capacity is the maximum, continuous torque transmission for which flexible shafts are designed. Torque, the measure of force applied to a member to produce rotation, is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied.
- Shaft diameter includes the shaft casing and helps determine speed and torque requirements.
- Minimum bend radius is measured during shaft operation.
- End-to-end length is measured along the centerline of the shaft.
Applications and Materials
Flexible shafts differ in terms of materials and applications. Most products are made of
- Carbon steel
- Stainless steel
- Tempered steel
- Music wire
- Rocket wire
- Bronze alloys
- Copper alloys
The aerospace industry uses flexible shafts in
- Thrust reverser actuation
- Variable bleed valve
- Magazine drive shaft
- Rescue pump
- Scavenger pump
- Flap actuation systems.
Automotive applications include
- Automatic pedal adjustment,
- Sliding door adjustments, a
- Power seating tracks
Industrial and Medical
Flexible shafts are also used in industrial power tools and reach rods for valve removal. In the medical field, flexible shafts are used in
- Biopsy probes
- Magnetic resonance imaging (MRI) drug delivery
- Orthopedic instruments
- Eye surgery.
DIN 75532-2 - Transmission of rotary motions; flexible drive shafts
DIN 75532-1 - Transmission of rotary motions; types of connection to gears, intermediate gears, flexible gears, fexible drive shafts and equpment
JIS D 5602 - Flexible shafts for speedometers and tachographs of automobiles