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Computers on Cokers
chirokid wrote: *The computer has no idea where the magnet/sensor are mounted, nor does it matter. It can be near the rim or very close to the hub. All the computer knows is to count 1 revolution each time the magnet goes past the sensor. Hope that helps. If not, I'm sure someone else will explain it much better.* Actually, that helped immensely. I wasn't halfway through reading the first sentence of your reply when the roar of a gigantic DUH! started building underneath my desk. Clearly I should have taken fewer trips out into the woods before my high school science classes. I can't believe I asked such a stupid question.... Thanks for the reality check....I'm going to go try my superglue and washer setup. -- tomblackwood - Under-prepared Dork (UPD) My other brake is my face! ------------------------------------------------------------------------ tomblackwood's Profile: http://www.unicyclist.com/profile/3762 View this thread: http://www.unicyclist.com/thread/25753 |
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#2
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Computers on Cokers
Actually, the position does matter, but in a way that may not be relevant. The position inboard/outboard determines the width of the electrical pulse generated by the sensor at a given speed. The computer electronics are designed to handle a certain sense of what "pulse" is. We can't know exactly what that is because we haven't been given the information with the computer. The optimum placement for the magnet/sensor, then, is the place which would make it most closely match the bicycle setup for which it was designed, because this would match the range of pulse widths most closely. To complicate things, the instruction manual doesn't state where on the bicycle wheel the sensor should be placed. However, there are some limitations due to sensor wire length which govern the magnet's placement. On the Enduro II, though, there is an internal setting "B" which makes slower speeds, such as mountain bikes would encounter, more accurate. Presumably this changes the computer's expectation of what a pulse will look like, perhaps by changing the sampling rate, or one of many other possible adjustments to the signal processing. In short, I'd put the sensor a little farther out than on a mountain bike, and use the "B" setting. Here's a pic of a sensor on a Coker, shimmed-out to meet the spokes at the optimal distance. Placing the sensor at the hub, although a) impossible due to the default sensor wire length limitation, and b) theoretically counting 1 revolution like any other location, is not desirable simply because it would lengthen the electrical pulse put out by the sensor so much that the computer readout most likely would be unreliable. It would make an interesting experiment to perform, just to see what happened! +----------------------------------------------------------------+ | Attachment filename: shimmed sensor and magnet (small).jpg | |Download attachment: http://www.unicyclist.com/attachment/153261| +----------------------------------------------------------------+ -- U-Turn - Mounting a Revolution Weep in the dojo... laugh in the battlefield. 'Strongest Coker Wheel in the World' (http://www.unicyclist.com/gallery/albup39) -- Dave Stockton ------------------------------------------------------------------------ U-Turn's Profile: http://www.unicyclist.com/profile/691 View this thread: http://www.unicyclist.com/thread/25753 |
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Computers on Cokers
tomblackwood wrote: * John: I'm not sure if you've tried the setup yet with one of your new Schwinns. I purchased the WalMart model, and in installing today, the magnet unit definitely doesn't fit over the spoke. What my current intended solution is will be to pry the groove on the magnet unit wide enough it that it can fit far enough over the spoke to show metal on the other side, then superglue a small metal washer or some other flat piece to hold it on. If you've already solved the problem in some more elegant fashion, would love a tip. * You are correct there. The slot in the magnet is not wide enough to fit around the Coker spoke. I just removed the magnet off my Coker to see what I had done to make it fit. I can see that I had filed the slot to make the slot wider. I don't have a metal file that thin so I must have used a fingernail file (emory board) to file it. It's soft metal so it files easily. It's a bummer that the magnet doesn't fit the fat Coker spoke without modifications. One strike against an otherwise excellent low cost cycle computer for the Coker. I don't remember having to file the slot wider, but obviously I had done so. The obvious file markings on the magnet are evidence enough. -- john_childs - Guinness Mojo john_childs (at) hotmail (dot) com ------------------------------------------------------------------------ john_childs's Profile: http://www.unicyclist.com/profile/449 View this thread: http://www.unicyclist.com/thread/25753 |
#4
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Computers on Cokers
The pic above is of stainless 14g spokes obtained from Tom Miller, so the magnet went on with no modifications. -- U-Turn - Mounting a Revolution Weep in the dojo... laugh in the battlefield. 'Strongest Coker Wheel in the World' (http://www.unicyclist.com/gallery/albup39) -- Dave Stockton ------------------------------------------------------------------------ U-Turn's Profile: http://www.unicyclist.com/profile/691 View this thread: http://www.unicyclist.com/thread/25753 |
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Computers on Cokers
I went with U-Turn's reccomendation (thanks) and got the Cateye Enduro II. It went on beautifully with no modifactions at all, just like the above photo. I didn't know about advantages of using the "B" setting, I just set it up with the "A". I used the # I got from a seated roll-out. It's been working great. It adds a nice bonus motivation factor to "Cokering". The wire is a heavy-duty one and, as I mentioned earlier in the thread, it only cost 16.99 through Performance Bikes. - Frank -- Frank A. - off-road "Man's maturity: to have regained the seriousness that he had as a child at play." - FRIEDRICH NIETZSCHE, Beyond Good and Evil ------------------------------------------------------------------------ Frank A.'s Profile: http://www.unicyclist.com/profile/1710 View this thread: http://www.unicyclist.com/thread/25753 |
#6
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Computers on Cokers
The distance from the magnet to the receiver has to be less then a quarter of an inch. The way it works is the receiver is a magnetic switch, which means that every time it passes a magnet it closes, it then closes a circuit. The computer DOSEN'T measure the speed the magnet passes the receiver it's just a switch. The computer counts how many circuits, or spins, it makes in a specific time frame. The problem with that is how dose the computer know how big every spin is? For that they made the calibration system, you put in how many millimeters you wheel goes on every spin, the switch tells the computer every time it spins once, the computer times the amount of time in between, and out comes the speed. So the truth is that it doesn’t make a difference where on the spoke you put the magnet since every time the wheel goes around once the spoke goes around once. Now most computers don't have the calibration input for the size wheel a Coker has, so the solution to that is to tell the computer the total distance on every spin by dividing up the spin. Meaning you put in half the rollout distance and put 2 magnets so the computer counts the distance twice which at half the rollout value is the right speed. Now to make things simple Step 1. Buy any computer. Step 2. Rollout you wheel at proper inflation. Step 3. Check if you computer goes that high If it does Step 4. Set the computer Step 5. Attach the computer Step 6. Attach the magnet Note. The computer and magnet could be at any height. If not Step 4. Set the computer at half the rollout distance Step 5. Attach the computer Step 6. Attach 2 magnets across from each other (9 spokes) Note. Always make sure the magnet passes the receiver. -- chaim ------------------------------------------------------------------------ chaim's Profile: http://www.unicyclist.com/profile/2146 View this thread: http://www.unicyclist.com/thread/25753 |
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