Flexible Shafts

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CEF flexible shafts typically consist of a rotating core shaft with metal end fittings for attachment to mating parts. When needed, a protective outer casing is used. This casing includes ferrule fittings that keep it stationary while the flexible shaft rotates inside.

Flexible shafts transfer torque through a bi-directional wrapped wire system with nearly unlimited connection ratios and no U-joint connections. In practice, flexible shafts should be operated at the fastest feasible speed. Higher speed lowers torque load and can increase service life.

CEF flexible shafts are designed for rotary power transmission through, around, under, and over structural members, bulkheads, and other aircraft obstructions. They are a simple, efficient, and economical solution for difficult rotary motion transmission requirements. Flexible shafts are stiff and responsive in applications requiring both forward and reverse operation, and can perform similarly to a solid steel shaft while providing significant integration benefits.

Typical Applications

Flap-slat actuation systems
Engine thrust reverser and afterburner nozzle vane control systems
Manual pilot controls, including landing gear, nose wheel steering, and canopy systems
Aircraft scavenger pumps
Variable bleed valves

Capabilities, Benefits, and Advantages

High degree of design freedom

Flexible shafts enable flexible placement of drive sources, including electric or hydraulic motors and manual drives. This design freedom reduces reliance on gear boxes, chains, pulleys, universal joints, and torque tubes. When designed into an aircraft, flexible shafts can reduce design time and lower unit costs by simplifying power transmission.

Alignment and large offsets

Most flexible couplings allow limited offset, and U-joints typically allow larger offset but can incur major efficiency losses at high angles. Flexible shafts can accommodate up to 180° of offset while maintaining high efficiency, and do not require the tight alignment tolerances that solid shafts typically demand.

High efficiency

Flexible shafts are typically 90% to 95% efficient. Belts, pulleys, gears, and U-joints generally have lower power transmission efficiency due to friction losses, which can require larger power sources.

Power-to-weight ratio

Flexible shafts can offer more than a 3:1 weight advantage compared to other design approaches for similar power loads. Torque tubes can be stiff and heavy, while flexible shafts provide a lightweight option with routing flexibility.

Lower rigging and installation costs

Flexible shafts can often be installed in minutes without special tools or skills. They reduce the need for precise alignment and can help accommodate aircraft tolerance stack-ups.

Reduced parts cost

Bearings and housings for torque tubes and gear systems can require precise machining, plus additional purchase, assembly, maintenance, and qualification costs.

Safer to operate

Because flexible shafts can be enclosed, they can be safer in open areas than exposed gears, belts, or spinning torque tubes.

Vibration and torque shock resistant

Flexible shafts are designed to withstand sudden load changes during starts and stops, and they can absorb and isolate vibration without degrading performance.

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Need a flexible shaft solution for a rotary power transmission challenge on your aircraft platform? Contact CEF Industries to discuss routing constraints, torque requirements, interfaces, and qualification needs.