Parker Randall

Rowing Machine

(Fall 2020)

This was my school project for Design Methodology (ME 366J). The objective of this project was to carry out the full design process (from identifying customer needs to constructing a working prototype) to create a DIY aerobic exercise machine that costs less than $150 to build. The project consisted of identifying customer needs, deriving design requirements, generating ideas and concepts, designing the leading concept, analyzing the design, and manufacturing a working prototype.

A door damper and a workout resistance band are used as the resistance and return mechanisms. Thus a stiffer resistance band can be installed to add more resistance. The angle of the central beam can also be adjusted to give more resistance, as a steeper angle will require the user to push harder with his/her legs. The paracord connecting the handle to the mechanism can be adjusted in length to accommodate users of different heights.

The general size of the machine was determined via intuition, but, once the frame had been built, the footrests could be mounted in a comfortable location. One interesting challenge of this project was finding the best geometry for the resistance mechanism. We could have used mathematics to determine the geometry that provided the best workout "feel". But since the spring and damping characteristics of our components were unknown, it made more sense to build a test rig, take force measurements, and perform a design of experiments to arrive at a good geometry.

The design had two main flaws that were discovered in the working prototype. One of them was that the seat could be unstable and the front wheels would sometimes lift off of the central rail. This could be alleviated by elongating the wheelbase of the seat. The other problem was that the rear stand would sometimes fold inwards and the rowing machine would fall flat. This issue could be resolved by adding longer supports at either end of the base of the rear stand.