Speedo measurements

[Eric Sheley <eric@xxxxxxxxxx>]

Well, as promised I tested the ST speedo against the Sigma BC800 computer
on Saturday. The Sigma is a bicycle computer that has been used frequently
by sport bike riders who are looking for a more accurate measurement of
speeds achieved. Radar tests have shown the sigma to be extremely accurate
when properly setup and will measure speeds of up to 180-190 mph (most
bicycle computers stop at 99mph).

Installation is pretty straightforward - a magnet is epoxyed to the front
rotor carrier and then the contact is mounted in such a way that they
magnet will trigger it. Front tire is then measured and input into the
computer - each pass of the magnet is then used to compute speed and distance.

The nice thing about the Sigma is that in addition to an accurate speed
measurement, you also get some neat features like 
- - top speed attained
- - average speed
- - trip time
- - continuous indication of over / under average speed

So - anyway on to the test ........

The good news is that the odometer is accurate - travelled 151.6 miles
according to the ST odometer on the test and the sigma indicated 151.3 -
close enough for me.

The speedo however was a different story - the following represents the ST
indicated speed, the actual speed (from the Sigma) and the RPM's shown on
the ST tach. I'm sorry there's not more data, but I had to stop after each
measurement - take off my gloves - open my jacket - take out pen and paper
- - record the 3 values and then start again - you get the picture  - I could
only take it so long before just wanting to keep riding - however if anyone
has a specific value they want tested, let me know and I'll do it in the
next few days.

MPH              MPH
Indicated       Actual         RPM
109-110          100            6400-6450
100                 92             6000
90                   83             5200
80                   73-74        4600-4700

I also tested RPM's vs actual speeds

RPM           Actual MPH
5000                78
4500                71
4000                63
3500                56

The RPM's on the first set of numbers are my best approximations of where
the needle was - at 100 mph its tough to see if it's 6400 or 6350 or 6450 -
I could just tell that it was under 6500 by a small amount but greater than
6250......

- - Eric





 *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *   *
 The ST Mailing list is sponsored by the Unofficial ST Website
   http://www.TriumphNet.com/st for ST and Mailing List info

=-=-=-= Next Message =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=