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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
My continuing woes with a 5 inch speedo - now 10 cables gone - help????????
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<blockquote data-quote="Hugo Myatt" data-source="post: 26967" data-attributes="member: 99"><p>Hi Cornelis and Nobby,</p><p></p><p>I have the same problem. My garage is down a steep slope with no possibility of turning round at the bottom so I have to wheel the bike backwards 20 meters or so. The cable does not always break at the time. It gets wound up like a spring and can break later. I have just sent the following to Stuart in a PM but I'm sure he won't mind my putting it on the forum. Pardon the lack of technical vocabulary.</p><p></p><p>'I’ve been thinking about the speedo head gearbox. I may have misled you as memory is possibly playing up. It may have been 17 turns of the cable rather than 17 turns of the wheel in the reverse direction. I have just dug out the old gears, which were returned to me by Speedograph Richfield. This is what I have discovered and now I begin to remember what they said.</p><p></p><p>First this is the gearbox that has a protruding worm gear for insertion in the speedo. Let’s call this the speedo gear and call the other into which the cable is inserted the cable gear. Both are supposed to have a minute (3/32”?) ball bearing between the gear end and the end plate to take up end thrust. The speedo gear always has one but it seems that sometimes on the cable gear it is missing. Whether it was omitted during manufacture or lost at a later date is unknown but is found to be common with these gearboxes.</p><p></p><p>Now the helical pinion on the speedo gear has a nicely machined chamfer on the ball bearing end however the cable gear pinion was not originally chamfered and was machined straight across. In practice this means that when the cable is turned in reverse the cable pinion tends to ride up the speedo pinion towards the endplate. Should the ball be missing, or if there is even a minute amount of wear in the pinions or housing, it allows the pinion to tilt slightly so that the sharp corners of the helical teeth dig into the end plate and the gear jambs. This can be witnessed by scuff marks on the end plate. Another way to check if this is happening is to compare both helical gears. The cable gear may at first sight appear to have a slight chamfer but compared with the properly machined chamfer on the speedo gear it becomes apparent that this blunting of the edges of the helical teeth on the cable gear is due to wear as it is forced against the end plate.</p><p></p><p>As I said Speedograph Richfield returned the gearbox with new gears saying they had modified it. In retrospect I think they must have machined a proper chamfer on the cable gear.'</p><p></p><p>Hugo</p></blockquote><p></p>
[QUOTE="Hugo Myatt, post: 26967, member: 99"] Hi Cornelis and Nobby, I have the same problem. My garage is down a steep slope with no possibility of turning round at the bottom so I have to wheel the bike backwards 20 meters or so. The cable does not always break at the time. It gets wound up like a spring and can break later. I have just sent the following to Stuart in a PM but I'm sure he won't mind my putting it on the forum. Pardon the lack of technical vocabulary. 'I’ve been thinking about the speedo head gearbox. I may have misled you as memory is possibly playing up. It may have been 17 turns of the cable rather than 17 turns of the wheel in the reverse direction. I have just dug out the old gears, which were returned to me by Speedograph Richfield. This is what I have discovered and now I begin to remember what they said. First this is the gearbox that has a protruding worm gear for insertion in the speedo. Let’s call this the speedo gear and call the other into which the cable is inserted the cable gear. Both are supposed to have a minute (3/32”?) ball bearing between the gear end and the end plate to take up end thrust. The speedo gear always has one but it seems that sometimes on the cable gear it is missing. Whether it was omitted during manufacture or lost at a later date is unknown but is found to be common with these gearboxes. Now the helical pinion on the speedo gear has a nicely machined chamfer on the ball bearing end however the cable gear pinion was not originally chamfered and was machined straight across. In practice this means that when the cable is turned in reverse the cable pinion tends to ride up the speedo pinion towards the endplate. Should the ball be missing, or if there is even a minute amount of wear in the pinions or housing, it allows the pinion to tilt slightly so that the sharp corners of the helical teeth dig into the end plate and the gear jambs. This can be witnessed by scuff marks on the end plate. Another way to check if this is happening is to compare both helical gears. The cable gear may at first sight appear to have a slight chamfer but compared with the properly machined chamfer on the speedo gear it becomes apparent that this blunting of the edges of the helical teeth on the cable gear is due to wear as it is forced against the end plate. As I said Speedograph Richfield returned the gearbox with new gears saying they had modified it. In retrospect I think they must have machined a proper chamfer on the cable gear.' Hugo [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
My continuing woes with a 5 inch speedo - now 10 cables gone - help????????
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