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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: 79707" data-attributes="member: 1177"><p>I did manual calculations, but I think there are only a few things to be aware of. You need to know the diameter of the wire, which is easy to measure. Multiply that times 11,250,000 Lbs./in. Squared, which is the modulus for spring steel. </p><p></p><p>This will be divided by: 8 times the number of active coils (count all the coils and subtract one for the number of active coils), multiplied times the mean coil diameter (you can put the tips of your caliper at the center of the flattened and ground end coil or do the math).</p><p></p><p>The "free length" of the spring seems obvious, but in spring parlance the spring should be "set" after manufacture. This means that the spring should be compressed to coil bind once before you measure the free length. Just be aware that the free length may change slightly if the spring is not set first.</p><p></p><p>The inactive number of coils is usually 1/2 per end, that is the part of the coil that is touching down on the spring box and thus, not active. NASCAR fans often hear that the pit crew has put a "wedge" in a spring. By jamming in a rubber wedge the crew makes more of the spring coils inactive and this increases the spring rate. It can be yanked out if track conditions change and a softer spring is required. </p><p></p><p>Wallace Racing has a lot of good calculators: <a href="http://www.pontiacracing.net/js_coil_spring_rate.htm" target="_blank">http://www.pontiacracing.net/js_coil_spring_rate.htm</a> </p><p></p><p>David</p></blockquote><p></p>
[QUOTE="davidd, post: 79707, member: 1177"] I did manual calculations, but I think there are only a few things to be aware of. You need to know the diameter of the wire, which is easy to measure. Multiply that times 11,250,000 Lbs./in. Squared, which is the modulus for spring steel. This will be divided by: 8 times the number of active coils (count all the coils and subtract one for the number of active coils), multiplied times the mean coil diameter (you can put the tips of your caliper at the center of the flattened and ground end coil or do the math). The "free length" of the spring seems obvious, but in spring parlance the spring should be "set" after manufacture. This means that the spring should be compressed to coil bind once before you measure the free length. Just be aware that the free length may change slightly if the spring is not set first. The inactive number of coils is usually 1/2 per end, that is the part of the coil that is touching down on the spring box and thus, not active. NASCAR fans often hear that the pit crew has put a "wedge" in a spring. By jamming in a rubber wedge the crew makes more of the spring coils inactive and this increases the spring rate. It can be yanked out if track conditions change and a softer spring is required. Wallace Racing has a lot of good calculators: [URL]http://www.pontiacracing.net/js_coil_spring_rate.htm[/URL] David [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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