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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
ATD Springs
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<blockquote data-quote="Ken Targett" data-source="post: 43352" data-attributes="member: 521"><p>Good to hear you've got the ATD sorted Martyn.</p><p></p><p>Good point, Sid. Got me thinking. A magneto ATD is very different to an auto advance in a coil ignition's distributor. In the distributor, the bob-weights are working against nothing much other than the springs, and so the spring characteristics are fundamental to the performance of the thing. In a mag ATD however, the bob-weights attempting to advance the timing are working against the magneto trying to retard it, and the springs merely provide, I'd say, a bit of 'fine tuning.' I did some experiments at the weekend, represented by this graph:</p><p><img src="http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20ATDs/Lucas%20ATD%20modified.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p>By "100% preload", I mean that the tension in the spring at fully-retarded is the same as the tension in a non-preloaded spring at fully-advanced.</p><p></p><p>Further details at <a href="http://brightsparkmagnetos.com/faqs/FAQs%20about%20ATDs/How%20critical%20is%20the%20spring%20rate%20and%20preload%20in%20an%20ATD.htm" target="_blank">http://brightsparkmagnetos.com/faqs/FAQs about ATDs/How critical is the spring rate and preload in an ATD.htm</a></p><p></p><p>Ken.</p></blockquote><p></p>
[QUOTE="Ken Targett, post: 43352, member: 521"] Good to hear you've got the ATD sorted Martyn. Good point, Sid. Got me thinking. A magneto ATD is very different to an auto advance in a coil ignition's distributor. In the distributor, the bob-weights are working against nothing much other than the springs, and so the spring characteristics are fundamental to the performance of the thing. In a mag ATD however, the bob-weights attempting to advance the timing are working against the magneto trying to retard it, and the springs merely provide, I'd say, a bit of 'fine tuning.' I did some experiments at the weekend, represented by this graph: [IMG]http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20ATDs/Lucas%20ATD%20modified.jpg[/IMG] By "100% preload", I mean that the tension in the spring at fully-retarded is the same as the tension in a non-preloaded spring at fully-advanced. Further details at [URL]http://brightsparkmagnetos.com/faqs/FAQs%20about%20ATDs/How%20critical%20is%20the%20spring%20rate%20and%20preload%20in%20an%20ATD.htm[/URL] Ken. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
ATD Springs
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