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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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<blockquote data-quote="davidd" data-source="post: 98686" data-attributes="member: 1177"><p>Bill,</p><p></p><p>I think the easiest way to understand how a coil spring works is to think of a torsion bar. A torsion bar is a straight round bar with a spline or square on both ends that provides springing by being twisted. If you put the square end of a torsion bar in a vise and put a wrench on the the other end you can try and twist it to see how strong it is. You can imagine that the diameter of the torsion bar has a lot to do with the ease of turning the bar...a .20" bar will turn easily and a 1" bar will be a bear. What about the length of the bar? Taking the .20" bar, if it is 12" long it will provide a lot of resistance to turning (it will feel stiff). But if it 5 feet long, it will turn more easily. </p><p></p><p>If you think of the coil spring as a torsion bar that has been wound into a coil it becomes easier to understand. (The coil spring does twist when used and you may have seen evidence of this. Some coil spring platforms have rotary bearings, for example.) Cutting an inch of a torsion bar will make it stiffer, just like cutting an inch off a coil. The short piece of coil spring or torsion bar will be a very stiff spring. In fact, wildly stiff, because it is so short. (That is why die springs are so stiff, they tend to be short with larger diameter wire.)</p><p></p><p>If you cut an inch off a torsion bar and reattach it by splining or squaring the ends you would have two stiffer torsion bars, one so short, it probably would not provide any noticable twist and the rest of the bar that is shorter and would provide a little more stiffness. This would turn out to be much stiffer than the single torsion bar that you started with. The same is true of a coil spring. The inch of coil that you cut of a 30 lbs rate spring has now become a die spring that has a 500 lbs. rate and will become coil bound very quickly. The two springs together will provide much higher stiffness, so to speak.</p><p></p><p>There is a formula for coil springs used in series, but if you think of the general situation, if you use two shorter springs in series it will make the total springing stiffer unless you adjust the wire diameters (smaller) to suit.</p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 98686, member: 1177"] Bill, I think the easiest way to understand how a coil spring works is to think of a torsion bar. A torsion bar is a straight round bar with a spline or square on both ends that provides springing by being twisted. If you put the square end of a torsion bar in a vise and put a wrench on the the other end you can try and twist it to see how strong it is. You can imagine that the diameter of the torsion bar has a lot to do with the ease of turning the bar...a .20" bar will turn easily and a 1" bar will be a bear. What about the length of the bar? Taking the .20" bar, if it is 12" long it will provide a lot of resistance to turning (it will feel stiff). But if it 5 feet long, it will turn more easily. If you think of the coil spring as a torsion bar that has been wound into a coil it becomes easier to understand. (The coil spring does twist when used and you may have seen evidence of this. Some coil spring platforms have rotary bearings, for example.) Cutting an inch of a torsion bar will make it stiffer, just like cutting an inch off a coil. The short piece of coil spring or torsion bar will be a very stiff spring. In fact, wildly stiff, because it is so short. (That is why die springs are so stiff, they tend to be short with larger diameter wire.) If you cut an inch off a torsion bar and reattach it by splining or squaring the ends you would have two stiffer torsion bars, one so short, it probably would not provide any noticable twist and the rest of the bar that is shorter and would provide a little more stiffness. This would turn out to be much stiffer than the single torsion bar that you started with. The same is true of a coil spring. The inch of coil that you cut of a 30 lbs rate spring has now become a die spring that has a 500 lbs. rate and will become coil bound very quickly. The two springs together will provide much higher stiffness, so to speak. There is a formula for coil springs used in series, but if you think of the general situation, if you use two shorter springs in series it will make the total springing stiffer unless you adjust the wire diameters (smaller) to suit. David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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