Design and prototype of a personal ascending device based on the principle of a capstan winch

Abstract

The consumer market currently offers no options for a low-cost, personal ascending device. The purpose of this project is to propose a powered ascender, actuated by common power tool components and operating on the principle of a capstan winch, as a candidate to fill that void. The first objective was to design and construct a working prototype. The second was to explore the feasibility of manufacturing a low cost consumer version of the product. Safety, functionality, and cost drove the design process. The ascender was designed and built around the motor and gearbox from a Dewalt 36v hammerdrill. Individual components were machined in undergraduate machine shops on the MIT campus and in the MIT Hobby Shop. Testing of the ascender was carried out using standard gym equipment and weights. The completed unit can lift 100 kg at 0.4 meters per second with an overall efficiency of 8.5%. This result was 57% lower than the predicted speed of 0.7 meters per second with an expected 14.7% efficiency. Analysis revealed a design flaw which can account for most of the discrepancy in the predicted and observed performance and which can easily be remedied. Powered ascenders within the same speed and load range are sold for several thousand dollars, demonstrating the feasibility of a low cost powered ascender as a viable product.