WRT
20th November 2006, 11:39
I've looked around a bit over the last few months at various options on putting a speedo on my CR250. Having hunted around, you can start from around $20 for a cheap bike computer designed for a push bike, all the way up to around ten times that for a reasonable computer designed specifically for motorbikes. The "proper" ones are loaded with features, have a huge, easy to read screen on them, and can include the ability to switch between bikes, which is quite handy for those with more than one dirt bike in their stable.
With me having some Dutch in my ancestry, I went for the el-cheapo option. I went around a few of the cycle retailers (Bike Barn, Pack and Pedal, Hedgehog, etc), and settled for a Vetta RT33, which is available from iBike for $30. This has the five main features I was looking for, which are:
Vehicle speed
Trip meter
Odometer
Service Timer (in hours)
Clock There are cheaper models that have less features (for example, no service timer), and more expensive models with more features (such as average speed / max speed, etc) without having to resort to a $200 unit specifically designed for motor bikes. I figured that I'm just wanting the basic features, and given the amount of punishment it will receive offroad and the vibration on a two stroke bike, the unit should be as "disposable" as possible. You also have the option of having a wireless system, but I went for a wired one, which in hindsight might not have been the best idea.
Basically what your $30 buys you is a handlebar mounted display, a magnet to clip onto your spokes, and a pickup that mounts on your forks so that it gets "tripped" each time the magnet passes. Included with the pack are some cable ties, different thickness mounts for the handlebars and forks, some stickers and a set of instructions. The display itself has a quick release from the handlebar mount so that you can pull it off the bike easily between uses. It also goes into a powersave mode if no input from the wheel or the buttons are received for five minutes to help conserve the battery.
The actual configuration of the unit is quite simple. There are only two buttons on it, one used for cycling (excuse the pun) through values and one that acts as an Enter/Tab button. You are asked to enter the time, clock format (12/24 hour), whether you wish to have the readout in kilometers or miles, the circumference of your tyre, and what the service intervals are. The tyre's circumference is worked out by marking a spot on the floor, rolling your bike forward for one revolution of the wheel, and then measuring the distance in mm.
Mounting the unit seems relatively straight forward, and I would imagine on a pushbike it most probably is. However, adapting it to fit a motorcross bike took a little bit of work. First issue is that the spokes on a MX bike are significantly thicker than on a push bike, hence the pickup doesnt really fit on them. Second issue was the distance from the spokes to the fork - far to great for the pickup to register the passing of the magnet. Third issue was the distance from handle bars to wheel - with the forks fully extended the supplied cable was far too short.
The cable is a simple fix, I merely added a extra lengh of speaker wire to it. Five minutes with a soldering iron, a bit of heat shrink, and you're good to go.
The problem of where to mount the magnet and pick up was more problematic. Nowhere do the forks and spokes come close enough together. Realistically, you need to have the magnet pass with a couple of mm of the pickup, and given the punishment the front wheel of a MX bike takes the mounting points need to be pretty inflexible.
How I got around it was by mounting the pickup on the front axle spacer (which doesnt rotate), and making a small bracket to mount the magnet onto the disk bolts. Effectively the magnet is inside the disk, passing underneath the calipers as the wheel rotates. Fortunately there is sufficent room for this without anything being in jeopardy of getting snagged on the brakes - which would have disasterous results, as I'm sure you can imagine.
This actually works quite well, as from here its easy to run the cable up the front brake line, resovling the problem of getting it up past the suspension. Also there is a cover which goes over the whole brake assembly and protects the lot from damage.
First test ride was on Saturday, in the pouring rain up at Woodhill. A quick blat down the beach confirmed two things, the speed takes a little while to update, and that at pace the small screen can be hard to read. By the end of the day, the unit had been well and truly soaked and abused, but it came through with no sign of deterioration. The display is hard to read if you are blasting along, but normally you wouldnt bother with that as all your attention should be focused on the terrain ahead.
The clock is very handy to have, and the odometer/trip meter give usefull info as well. Once you know the distance you can get from a tank it will make it a lot easier to gauge on the fly how long you can keep riding for. The service interval timer should help out considerably as well, seeing as I dont currently have a motominder fitted to the bike.
In the mean time, I'll still be counting my hours until I come to fully trust the unit, but after the hard time it was given on Saturday it looks like the unit will work just as planned.
Final thoughts: I think that it might have been easier with the wireless option, however it would pay to check how far and how reliable the "connection" between the display and the pickup would be. Also, the magnets are a replaceable component - so perhaps it would pay to put two in place at opposite locations on the wheel. Then you could halve the circumference value you enter into the unit and theoretically also halve the time it takes the display to pick up speed changes.
All in all however, I'm quite happy with the unit and for $30 its a bargain.
Pictures below, please excuse the quality as they were taken with my phone. I'll take some with the camera if anyone is interested in better res images.
With me having some Dutch in my ancestry, I went for the el-cheapo option. I went around a few of the cycle retailers (Bike Barn, Pack and Pedal, Hedgehog, etc), and settled for a Vetta RT33, which is available from iBike for $30. This has the five main features I was looking for, which are:
Vehicle speed
Trip meter
Odometer
Service Timer (in hours)
Clock There are cheaper models that have less features (for example, no service timer), and more expensive models with more features (such as average speed / max speed, etc) without having to resort to a $200 unit specifically designed for motor bikes. I figured that I'm just wanting the basic features, and given the amount of punishment it will receive offroad and the vibration on a two stroke bike, the unit should be as "disposable" as possible. You also have the option of having a wireless system, but I went for a wired one, which in hindsight might not have been the best idea.
Basically what your $30 buys you is a handlebar mounted display, a magnet to clip onto your spokes, and a pickup that mounts on your forks so that it gets "tripped" each time the magnet passes. Included with the pack are some cable ties, different thickness mounts for the handlebars and forks, some stickers and a set of instructions. The display itself has a quick release from the handlebar mount so that you can pull it off the bike easily between uses. It also goes into a powersave mode if no input from the wheel or the buttons are received for five minutes to help conserve the battery.
The actual configuration of the unit is quite simple. There are only two buttons on it, one used for cycling (excuse the pun) through values and one that acts as an Enter/Tab button. You are asked to enter the time, clock format (12/24 hour), whether you wish to have the readout in kilometers or miles, the circumference of your tyre, and what the service intervals are. The tyre's circumference is worked out by marking a spot on the floor, rolling your bike forward for one revolution of the wheel, and then measuring the distance in mm.
Mounting the unit seems relatively straight forward, and I would imagine on a pushbike it most probably is. However, adapting it to fit a motorcross bike took a little bit of work. First issue is that the spokes on a MX bike are significantly thicker than on a push bike, hence the pickup doesnt really fit on them. Second issue was the distance from the spokes to the fork - far to great for the pickup to register the passing of the magnet. Third issue was the distance from handle bars to wheel - with the forks fully extended the supplied cable was far too short.
The cable is a simple fix, I merely added a extra lengh of speaker wire to it. Five minutes with a soldering iron, a bit of heat shrink, and you're good to go.
The problem of where to mount the magnet and pick up was more problematic. Nowhere do the forks and spokes come close enough together. Realistically, you need to have the magnet pass with a couple of mm of the pickup, and given the punishment the front wheel of a MX bike takes the mounting points need to be pretty inflexible.
How I got around it was by mounting the pickup on the front axle spacer (which doesnt rotate), and making a small bracket to mount the magnet onto the disk bolts. Effectively the magnet is inside the disk, passing underneath the calipers as the wheel rotates. Fortunately there is sufficent room for this without anything being in jeopardy of getting snagged on the brakes - which would have disasterous results, as I'm sure you can imagine.
This actually works quite well, as from here its easy to run the cable up the front brake line, resovling the problem of getting it up past the suspension. Also there is a cover which goes over the whole brake assembly and protects the lot from damage.
First test ride was on Saturday, in the pouring rain up at Woodhill. A quick blat down the beach confirmed two things, the speed takes a little while to update, and that at pace the small screen can be hard to read. By the end of the day, the unit had been well and truly soaked and abused, but it came through with no sign of deterioration. The display is hard to read if you are blasting along, but normally you wouldnt bother with that as all your attention should be focused on the terrain ahead.
The clock is very handy to have, and the odometer/trip meter give usefull info as well. Once you know the distance you can get from a tank it will make it a lot easier to gauge on the fly how long you can keep riding for. The service interval timer should help out considerably as well, seeing as I dont currently have a motominder fitted to the bike.
In the mean time, I'll still be counting my hours until I come to fully trust the unit, but after the hard time it was given on Saturday it looks like the unit will work just as planned.
Final thoughts: I think that it might have been easier with the wireless option, however it would pay to check how far and how reliable the "connection" between the display and the pickup would be. Also, the magnets are a replaceable component - so perhaps it would pay to put two in place at opposite locations on the wheel. Then you could halve the circumference value you enter into the unit and theoretically also halve the time it takes the display to pick up speed changes.
All in all however, I'm quite happy with the unit and for $30 its a bargain.
Pictures below, please excuse the quality as they were taken with my phone. I'll take some with the camera if anyone is interested in better res images.