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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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<blockquote data-quote="timetraveller" data-source="post: 75534" data-attributes="member: 456"><p>Thanks Greg for the write up. Regarding the springs; these are now ordered and should be with me next week. I have ordered 10 off of the 30 lbs/inch and 10 off of the 36 lbs/inch. Chris Launders has been using the 36 lb one on his road bike for several months now and they are clearly not too strong. On the Lighting replica we raced at Brands and Goodwood earlier this year I fitted 30 lb springs and on that bike they were about right. We measure the total movement of the spring boxes by fastening a cable tie around the inner spring box at the level where the bottom of the outer spring box is and then see how far down it is pushed after using the bike over bumps at speed. Chris is getting about 2.5" of movement. He has shortened his spring boxes, inner and outer, by one inch to allow for more movement. Note that with the new set up the distance from the top to bottom fixing for the spring boxes is now one inch less than the standard set up so the shorter boxes do not show up as different. I have tried my own spring boxes and the inner will move fully up into the outer and is stopped at the top. So on these particular spring boxes the flared lower section is not doing anything and therefore in my case it would be possible just to cut off the top of the inner and the bottom of the outer.</p><p>Feedback on this project is the best way to ensure that anyone who wants to can benefit from it. So far the best feedback I have had is from Chris on his road going twin and Greg with his light weight racer. The extra information on the Comet is very useful. Once I have the new batch of springs my intention is to send two of the 30 lb ones to Chris to try on his road twin. My suspicion is that they will be too weak but we will see. I will also send out two 36s and one 30 to Greg and others who are prepared to road test them on twins. It is possible that one 36 and one 30 will be about right, or even two 30s. My guess is that on Comets two 30 will be about right but the springs might need to be shortened. At the moment the new springs are made to be 16.5" long which will give a 3" preload. This is to ensure that the ride height and the angle of the lower link is correct. That is that the front of the lower link is just pointing upwards when the bike is fully loaded with the rider on board. On the Comet, once you have the lighter springs I would suggest trying them out full length and then if they prove to be too stiff, cutting of half an inch progressively until the preload gives the correct angle at the front.</p><p>This now leaves the damper at the front. I lent Chris one of the new AVOs and at its lightest setting it seems to be superb. However, during this last week John Emmanuel has been in touch about the damping and other matters and it transpires that I, at least, do not understand damping. The new AVOs, even on their easiest setting are still only just moveable by hand. That is as delivered, so whether they free up a bit with use I don't know. Yet John, using a Thornton damper on the front found that about right. Now John has sent me his Thornton damper and it is very light on compression, about the same as my old Armstrong or Vincent dampers. John believes that a light damping is required. Chris finds the relatively firm damping of the AVO gives superb control. Clearly there is more to damping than I know about.</p><p>There is one final thing about dampers. Rob Staley (Hadronuk) who has done most of the development work with AVOs for their new Vincent dampers says that there is 3" of movement on their front dampers. This total movement is important as it affects whether short or long eyebolts should be used with these dampers. So far all Chris' test have been done with long eyebolts.</p><p>What I am trying to achieve here is that following John Emmanuel's development which improves the handling I am trying to find what spring strengths and lengths will give the maximum comfort and movement at the front end. Laney Thornton did this years ago for the standard set up but the modification to improve the handling deserves to be developed to give more comfort as well. Watch this space.</p></blockquote><p></p>
[QUOTE="timetraveller, post: 75534, member: 456"] Thanks Greg for the write up. Regarding the springs; these are now ordered and should be with me next week. I have ordered 10 off of the 30 lbs/inch and 10 off of the 36 lbs/inch. Chris Launders has been using the 36 lb one on his road bike for several months now and they are clearly not too strong. On the Lighting replica we raced at Brands and Goodwood earlier this year I fitted 30 lb springs and on that bike they were about right. We measure the total movement of the spring boxes by fastening a cable tie around the inner spring box at the level where the bottom of the outer spring box is and then see how far down it is pushed after using the bike over bumps at speed. Chris is getting about 2.5" of movement. He has shortened his spring boxes, inner and outer, by one inch to allow for more movement. Note that with the new set up the distance from the top to bottom fixing for the spring boxes is now one inch less than the standard set up so the shorter boxes do not show up as different. I have tried my own spring boxes and the inner will move fully up into the outer and is stopped at the top. So on these particular spring boxes the flared lower section is not doing anything and therefore in my case it would be possible just to cut off the top of the inner and the bottom of the outer. Feedback on this project is the best way to ensure that anyone who wants to can benefit from it. So far the best feedback I have had is from Chris on his road going twin and Greg with his light weight racer. The extra information on the Comet is very useful. Once I have the new batch of springs my intention is to send two of the 30 lb ones to Chris to try on his road twin. My suspicion is that they will be too weak but we will see. I will also send out two 36s and one 30 to Greg and others who are prepared to road test them on twins. It is possible that one 36 and one 30 will be about right, or even two 30s. My guess is that on Comets two 30 will be about right but the springs might need to be shortened. At the moment the new springs are made to be 16.5" long which will give a 3" preload. This is to ensure that the ride height and the angle of the lower link is correct. That is that the front of the lower link is just pointing upwards when the bike is fully loaded with the rider on board. On the Comet, once you have the lighter springs I would suggest trying them out full length and then if they prove to be too stiff, cutting of half an inch progressively until the preload gives the correct angle at the front. This now leaves the damper at the front. I lent Chris one of the new AVOs and at its lightest setting it seems to be superb. However, during this last week John Emmanuel has been in touch about the damping and other matters and it transpires that I, at least, do not understand damping. The new AVOs, even on their easiest setting are still only just moveable by hand. That is as delivered, so whether they free up a bit with use I don't know. Yet John, using a Thornton damper on the front found that about right. Now John has sent me his Thornton damper and it is very light on compression, about the same as my old Armstrong or Vincent dampers. John believes that a light damping is required. Chris finds the relatively firm damping of the AVO gives superb control. Clearly there is more to damping than I know about. There is one final thing about dampers. Rob Staley (Hadronuk) who has done most of the development work with AVOs for their new Vincent dampers says that there is 3" of movement on their front dampers. This total movement is important as it affects whether short or long eyebolts should be used with these dampers. So far all Chris' test have been done with long eyebolts. What I am trying to achieve here is that following John Emmanuel's development which improves the handling I am trying to find what spring strengths and lengths will give the maximum comfort and movement at the front end. Laney Thornton did this years ago for the standard set up but the modification to improve the handling deserves to be developed to give more comfort as well. Watch this space. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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