Building a Solar Engine Dynamometer

Introduction

In the last Starting Block article, Mycroft2152 introduced many of us to the concept of testing solar engines using scavenged computer mice. In this article, I am going to show how to build a dynamometer using a mouse, and provide software for measuring and saving test results.

Here are the design goals for this project:

Use the mouse and dynamometer simultaneously. This is accomplished by using the mouse’s scroll wheel as opposed to the X-Y bars, and by using USB for hot swappable support.

Single unit construction. This article first presents instructions on building BETS1. You can use this separately, or complete the base and finish the dynamometer. When completed, the dynamometer features a BETS1, detachable breadboard, and space for a power supply in one convenient unit.

Support changing the test motor. Different motors produce different performance under any given solar engine. The dynamometer’s base features a motor mount with several holes for testing motors of differing sizes.

Include protection from ambient light. As pointed out by Mycroft2152 in the earlier article, some mice can fail to register properly if too much light hits their sensors. The motor mount doubles as a shade for the BETS1 mouse.

Easy construction and wide tolerances. The dynamometer base is made from Sintra. Bending Sintra to exacting standards takes both practice and luck. I have tried various different techniques for building the dynamometer, and have selected this one for the article as it allows for the greatest tolerance in bending and shaping.

Dedicated testing application. You can download the accompanying dynamometer software for this article, along with its source code. I wrote this software explicitly for testing solar engines and running calculations that provide an indication of overall performance.

Acknowledgements

This write-up was made possible in large part to the collaboration with Mycroft2152. Mycroft2152 shared his experiences with various BETS1 configurations, patiently tested the dynamometer software, and reviewed my initial drafts. His comments have greatly improved my test stand and this article.