Weekend project: Adding a cycle computer to my Ludix Blaster

Ludix BlasterA few weeks ago I bought a Peugeot Ludix Blaster RS12 scooter. It’s really just to get me to work and back. Between parking and petrol, taking my car to work was costing me about 9 a day (4.50 petrol + 4.50 parking, and that doesn’t account for tyres, petrol, servicing, etc). The scooter isn’t properly run in yet, but already it’s costing me just 1.50 a day in fuel and is free to park at my work. At that rate, it’ll have completely paid for itself in about nine months.

The only thing that annoyed me about the Blaster as standard was its instrument panel. The odometer is in kilometers, there’s no trip counter, the speedometer is pretty inaccurate and it doesn’t have a clock. I decided the best way to solve all those problems at once was to fit a cycle computer.

I settled on the Specialized Speedzone wired cycle computer. It has a fairly heavy duty cable and two well-spaced, hard plastic buttons — perfect for operating with thick motorcycle gloves. It cost me 20 from Dales in Glasgow.

Details of how I fitted it are after the jump…

Step 1: Fitting the handlebar bracket

Speedzone bracketThe Speedzone handlebar bracket curves round approx 1/4 of a standard cycle handlebar. As I wanted to keep the plastic cover and visor on my handlebars, I had to mod the bracket to fit. First I removed the soft rubber underside of the bracket. Using a Dremel, I shaved off the curved plastic parts of the bracket. I then refitted the rubber and drilled a hole through the bracket and rubber. I attached the bracket to the handlebars using a small nut & bolt (see pic).

Step 2: Running the cable

I ran the cable down through the handlebar cover, again using the Dremel to make a small notch for the cable. At first I tried to take the full front fairing off to run the rest of the cable, but I quickly realised that there were a lot more Torx screws involved than I could be bothered with. Instead, I dropped the wheel sensor down through the plastic fairing, trying to follow the path of the front brake hose. After a couple of attempts, the sensor dropped through the bottom of the fairing.

Step 3: Attaching the sensor

Speedzone sensorAt first I considered following the route of the mechanical speedo cable and attaching the wheel sensor to the end of that. However, I was concerned that the cable would move around too much, potentially causing the sensor to move too far away from the magnet. After trying a few different positions I finally settled on the very bottom of the forks, just above the wheel nut. In this position it gives about 3mm clearance between the sensor and the magnet.

Step 4: Attaching the magnet

The magnet that comes with the Speedzone is the usual screw-onto-a-spoke type which wasn’t really suitable for the scooter. As the scooter was brand new, I didn’t fancy trying to drill a hole in the alloy wheel to screw the magent on, so I brought out the Dremel again…

Using a cutting disc, I made several cuts into the magent housing, eventually getting it to the point where I could ‘peel away’ the metal housing in sections. What I was left with was the magnet on its own. It was a bit rough around the edges, but still did what magnets do best. What really surprised me was how light the magnet was. In its standard housing the whole thing is quite heavy, but the magent on its own was feather light. I attached it to the wheel using some two-part Superglue. The magnet and sensor are visible in the pic above.

Step 5: Calibrating the computer

Speedzone on Ludix BlasterOnce everything was in place, all that was left to do was calibrate the wheel size on the cycle computer. I measured a full revolution of the front wheel using the standard ‘roll out’ method. I think it came out somewhere around 1460mm. It’s good to get this measurement as accurate as possible, but don’t worry about it too much. Even if you’re 5mm out, that still equates to an error of less than 0.4%. Compare that to the standard speedo which is out by over 15%!

Step 6: Road test

Once the computer was calibrated I took it out for quick run. The results were pretty surprising. When the standard speedo read 30mph my real speed was more like 24mph. In restricted form the scooter’s speedo claimed a max speed of about 36mph which in reality was more like 30.4mph.