Wheelco – unicycle computer

I have installed a wheelco (bike computer on an electric unicycle) in my generic X3 clone. The mod was  explained there. It was well integrated but very long to install.

This new version is much easier and faster to mod, more than repairing a flat tyre.
It doesn’t require drilling or cutting the wheel’s housing and doesn’t void the warranty.

With adequate ajustment, the wheelco can reach surprising accuracies for distance and thus speed, at better than 0.1%, easily.  The wheelco can be so accurate as to detect a low pressure tyre by riding a known and calibrated distance and comparing it to the reading : with low pressures, distance readings will be higher than real distance and vice versa. It is also be a usefull gadget to watch the wheel’s range with more accuracy than the wheel’s leds, especially for wheels with small batteries.

Pictures are taken on my Gotway but the same principles apply to most any other wheels (see a wheelco on my Firewheel). Click pictures to zoom.Image

The eureka moment had been to use two rigid and solderable wires as electrical links and as a holder. The wire are enough rigid to keep the wheelco in position and enough flexible to allow for some displacement in case of a fall. After some months of testing on my Firewheel and several “controlled” falls (ie without faceplanting), the system appears to be reliable even when heavily exposed to shocks.

Profile view of the wheelco. The two rigid wires (0.8mm diameter) are connected to the ILS magnetic sensor by a X3 terminal block. The rigid wires are bent to pass between the housing and the cover or between the two half-housing. It can also pass through the housing provided 2 small holes are drilled.
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Back view of the wheelco. The rigid wires are directly soldered to the bike computer pins and zig-zag bent to allow for some flexibility to avoid breaking by a shock. The ILS sensor has been pried open then covered by a shrink wrap to reduce its overall thickness, otherwise, it won’t fit in the Gotway’s batteries compartment.
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Wheelco installation, consisting simply of snaping it into place. The ILS sensor must be exactly placed as in the picture, otherwise it won’t detect the magnet.
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Batterie pack installed. The ILS sensor in solidly anchored by the black foam.
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Make to notches in the cover at the position of the two rigid wire to allow remounting of the cover.
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The cover can now be screwed to the housing. The wheelco will be solidly attached once the screws are in place.
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Remove one of the motor cover screw and remount it with the magnet. No need to open the wheel’s housing.
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Magnet with a 1.3 mm diameter very rigid wire. The motor cover’ screw has some theadlock (in blue. If you don’t add liquid theadlock when remounting, check after 1 week that the screw is still in place and has not moved because of vibration.
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Wheelco mounted. The whole mod should last less than 20 minutes if all parts have been prepared. The screen is maximum at the forefront to ease reading during the ride.  In this tutorial, the wheelco is on the right and the wires are right-arranged. In another setup (wires passing inside at the midle between the two half housing) the wires can be left-arranged.
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The holding system is solid, invisible and doesn’t add to the thickness of the bike computer.
Choose a wheelco with colors assorted to you wheel (red & black, black, white…) to have a well integrated mod. It’s a totally reversible mod, ie if you don’t like it, just remove it..
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Wheelco on a Firewheel. Much more exposed to shocks (but ideally placed for reading) so the wires must make turns to allow for more flexibility. Extra wire length inside the housing helps keeping the wheelco in position.
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Complete kit


Options

  • Options 1, colors : black & red, black, white
  • Option 2, wire arrangment : left, right, straight

 

 


Bike Computer

Sunding brand, user manual (pdf).
Displayed variables
Intantaneous speed : with big digits
*Max speed : not always reliable because of spurious values
*Mean speed
*Trip distance : accuracy up to one meter
*Trip time : in h:mn:ss
Clock : about 2s/day drift compared to internet clock, not bad. To change time, move to this mode clock, and hold left button > 3s to enter adjustment mode.
Odometer : measure total distance since installation (value lost if battery removed so remember the value and update it after a battery change)
* : hold left button > 3s to reset before each new trip)

Adjustment

Wheel circumference must be entered in mm. For a 14″ wheel theorical value is
14 inch x 25,4 mm/inch x pi = 1117 mm
With values of 1116 or 1118, the adjustment can be made up to +- 0,1% accuracy.

Wheel diam “ 10 12 14 16 18
Wheel circonference mm 798 976 1117 1277 1436

Accuracy tests

I made three times the same trip around the neighbourhood. Real distance 454 m measured by  Google Earth ; distances indicated by the wheelco :

  • 456 m
  • 458 m (some zigzags to avoid a car)
  • 454 m

It works flawlessly without any adjustment needed.
Conclusion : total success ! Such accuracy would never be possible with a GPS because of interpolation, not to mention that the GPS doesn’t work correctly in an urban environment or in underground parking lots. Using the wheelco and comparing it in realtime to the Gotway Android app shows that the GW odometer is consistent with the whelco odometer (see table) but the GW’s speed counter is inflated by about 10% (20km/h wheelco => 23 km/h Android app), clear evidence that Gotway makes exagerated claims on its speed specifications.

Wheelco (km) 9.12 31.82 12.59 30.31 21.82 31.42
GW Android app (km) 9.20 31.97 12.46 30.00 21.53 31.03

3 thoughts on “Wheelco – unicycle computer

  1. Bruce

    I agree a wired version is better, I tried the wireless type and tried to wear the computer otn wrist. That is a no good, the wireless computer must always be facing up or horizontal to earth plane to receive signals, it will not receive signals if vertical, as when my hand is to the side of body, most of the time… And I tried hotgluing sensor to outside of body, held for a good portion, at least good enough for testing. I also hotglued big round magnet on the rim near wheel, this should have been epoxied and never near toughing tire, but good for testing…. I got readings only when looking at computer, so it did not record total distance…

    Reply
    1. hobby16 Post author

      Not sure epoxy will hold stuffs very long : because epoxy tend to harden, difference in thermal dilatation with metal will end up cracking the bond. I tried hotglue too without much success because mine is of bad quality and becomes very hard when cold and then, it’s not good at anything.
      Good glue exists to enable good bonding to metal but it’s so variable I prefer not to recommend glueing.

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