Project 1 - How to do Rolldown Tests

A guide by Chris Freear and Scott Campbell

One of the things that many recumbent builders and riders do is mess around with fairings of one sort or another for their machines. The problem comes when trying to compare relative performances of one arrangement against another. Few of us have the fancy equipment necessary to do live, on-the-road testing.

However, it is possible to do your own testing with very little equipment other than pencil and paper, a cycle computer and a certain amount of patience, as long as you don’t mind doing it at a particular place.

In our Special Issue #5, we describe a location near Christchurch which is a suitable place for rolldown testing. This is the bottom part of Kennedy's Bush Road near the Halswell quarry. If you intend on doing some rolldown testing, you'll find it worthwhile to purchase a back issue of Special Issue #5. Find out how ...

The detail of the method is given in the article, but the calculations as described may put off some people. As an alternative, you can download a spreadsheet for doing the calculations from this page.

There are two formats available:

• rolldown.xls - MS Excel 2.1 format.
• rolldown.wk1 - Lotus 1-2-3 format.

The spreadsheet has a section of Constants at the top. Don't change these numbers. The measurements from your rolldowns (Mass, Max Speed, and Total Distance) are entered in the main part of the table marked Measurements. Some working is done in the columns next to the measurements. You may want to hide these columns. The final results appear in the righthand columns marked Results (Frontal Area and Rolling Resistance).

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