Windage Brake Spool with Tapered Axis and Independent Fan
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Solution Overview
Problem
Existing windage brakes for fan descenders are bulky, require counterweight arrangements for line retrieval, and lack flexibility in controlling the speed of the fan's rotation, limiting their installation locations and user experience.
Innovation Solution
A compact windage brake design featuring a spool with a tapering axis and a separate rotatable fan driven by a pulley system, utilizing a retractor spring for automatic line retrieval and a radial flow air impeller with adjustable speed, allowing for controlled descent rates and compact transportability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the fan is secured to the spool to rotate directly with it, then the structure is simple, but the assembly becomes bulky with long axial dimension requiring permanent mounting
Solution Approach 1:
The fan assembly is separated from the spool into independent components. The fan is mounted on a separate shaft that can rotate independently within the spool housing, allowing the spool to be compact while the fan extends radially to generate sufficient drag without increasing axial dimension
2Device complexity
If the fan is secured to the spool to rotate directly with it, then the structure is simple, but the fan speed cannot be adjusted relative to spool speed
Solution Approach 1:
The fan shaft is made independently rotatable within the spool, allowing variable speed operation. The fan can rotate faster than the spool to generate sufficient drag force, and the speed ratio can be adjusted by changing the diameter of the fan shaft or adding gear mechanisms, providing adaptability for different descent rates
3Extent of automation
If a counterweight arrangement is used for line retrieval, then the line can be retrieved automatically, but the installation location is restricted and the appearance is unprofessional
Solution Approach 1:
The counterweight retrieval mechanism is replaced with a compact spring-loaded reel system integrated into the spool housing. The spring is pre-loaded to wind the line back onto the spool after descent, eliminating the need for external counterweights and allowing installation in locations where counterweights would be impractical
4Speed
If the line unwinds very quickly to get the fan to high speed, then the fan reaches necessary speed before landing, but the unwinding process becomes difficult to control
Solution Approach 1:
The independently rotatable fan shaft allows the fan to accelerate to high speed through a different mechanism than direct spool unwinding. The fan can be driven by a separate motor or by a gear system with varying ratio, enabling controlled acceleration to high speeds without requiring rapid line unwinding, thus maintaining ease of operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables a compact, portable, and easily installable windage brake that provides a controlled and safe descent with adjustable braking force, facilitating recreational and rescue operations while simplifying the retrieval process and reducing installation complexity.
Implementation Method 1
The retrieval mechanism may comprise a retractor spring (possibly more than one) which is resiliently loaded when the spool is rotated by drawing off the line and resiles to rewind the line upon the spool when the free end of the line (24) is released
Implementation Method 2
a fan driven by the spool to rotate when the line is drawn off from the spool by its free end, thereby to limit the speed of rotation of the spool and hence the rate at which the line is drawn off
Data Source
Figure 1~3
Figure 4~6
AI summary
A windage brake for a fan descender comprises a rotatable spool (10) connected by drive belts (32) to a fan (16) comprising a radial flow air impeller. A line (24) is wound helically upon the spool (10). A user of the fan descender puts on a harness (not shown) at the free end (24a) of the line (24) and jumps from an elevated position. The line (24) is thereby drawn off the spool (10) and rotates it. The rotating spool (10) drives the fan (16) and also winds a power spring formed by a resilient strip (44). The windage of the fan (16) regulates the descent of the jumper, the fan (16) being accelerated to a speed at which the braking force is such that the jumper descends at a rate safe for landing on the ground. When the jumper is on the ground, he removes the harness and releases the free end (24a) of the line (24). The line (24) is then automatically retrieved by the power spring and rewound on the spool (10).