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Bicycle Trip Computer

Words and Pictures by
Craig Sinclair

Recently I fitted a Sigma Sport BC700 Bicycle computer to my Dominator. There are a number of different models available and there a number of sites on the net that explain installation but the instructions that follow should be applicable to installing any of the Sigma Sport models to a Dominator.

Cost was about A$35 three years ago from a bicycle shop (it sat in the box a long time before I decided to install it!).

The BC700 has 7 functions. They are:

  • Speed (in either kph or mph)
  • Trip Distance
  • Total Distance
  • Clock
  • Trip time
  • Maximum speed
  • Average speed

    The BC700 kit consists of:

  • Computer
  • Handlebar mounting bracket with cable and sensor
  • A magnet
  • A number of o-rings

    As the system was designed for a push bike, the cable supplied from the computer to the sensor needs to be lengthened by about 10-15cm. This was done by cutting the cable and splicing a 15cm length of thin cable to each end.

    The sensor was glued (I used a 2 part epoxy) to the front left fork (just left of the A in Figure 1), while the magnet was glued to the front disk (just below the B in Figure 1. The position is more clearly seen in D in Figure 2 - the magnet is mounted just left of the D). The magnet should be glued first and the sensor second making sure that when the wheel is rotated the sensor is as close as possible to the magnet without actually touching. If they are too close then they will hit - if they are too far apart then the sensor won't work. An alternative is to use a stronger magnet - then the distance between the two isn't as critical.

    Figure 1

    Figure 2

    The cable from the sensor is then tie-wired to the brake line (C in Figure 1) in a number of places, keeping the wire behind the brake line for protection. Make sure there is some slack in the cable further up to allow for suspension travel and turning the handlebars.

    The computer was attached to the handlebar using the O-ring supplied (E in Figure 3).

    The last step is to measure the diameter of the front wheel and enter this into the computer (instructions supplied).

    Figure 3

    So far, everything has survived 1500km of a mixture of dirt and tar without problem. The speedo on the BC700 is supposed to be accurate to 2kph and will record up to 300kph. It is interesting to see the difference between the bikes normal speedo and the BC700 speedo.

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