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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
New ESA Design
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<blockquote data-quote="Tim Kirker" data-source="post: 91049" data-attributes="member: 200"><p>I'm afraid I don't often contribute to the Forum because I just can't find the time to keep up with all the threads I'm interested in, but my attention has been drawn to this discussion about the ESA profile. As draughtsman for the Technical Committee TC, I was insrumental in developing the latest cam design that is now available from VOCSC. </p><p></p><p>The first thing to emphasise is that the TC's terms of reference are not to develop new and improved designs, unless there is clear evidence that the current design is dangerous or clearly an error made by the factory. Our objective is to compile new manufacturing drawings that will allow new parts to be manufactured as close as possible to the original design intent.</p><p></p><p>In the case of the ESA, we came to the view that the then standard of ESA being made was not what PEI originally intended, and had all the faults observed by Vic. So I set out to reproduce a cam profile as close as possible to what PEI originally designed. We did not have original drawings but we did have drawings for the Velocette ESA, also designed by PEI. What I came up with is about the best compromise between that Velocette design and the slightly different surrounding dimensions of the ESA. (Like the amount of axial lift possible, the outer radius etc.) We also looked at some very early Vincent parts, which tended to confirm that the product then available had drifted a long way away from the original design.</p><p></p><p>All of this was written up, at some length, in MPH 808 in May 2016, together with photos similar to Vic's. I'm surprised and disappointed that nobody in this thread has referred back to that article, which I think you will find addresses most, if not all of the concerns raised by Vic and others. We may not have "solved" them in the same way as Vic proposes, but we have solved them pretty well within our terms of reference.</p><p></p><p>The BMW design that Vic is copying is very interesting but is only possible if you accept that the two cams will not be identical, and the drive will be through two lobes, not three - thus you can accommodate a much greater radius in the trough of one side, and a much finer radius for the lobe in the other side. The down side of this approach is that contact between the cams is restricted to two places (or three, if there are three lobes), whereas the Vincent/Velo design has contact in six places. Also, the Vincent lobes are much more robust than Vic's modified lobes. How long before one breaks off? As the Technical Authority for the VOC, the TC cannot take a punt on what might, or might not, work. Our Product Liability Insurance would be blown away. </p><p></p><p>Final thought, I seem to remember that Prof Higgins studied the movement of the ESA with strobe lighting years ago and concluded that it didn't need much torque/revs before the cam locked solid and it looks like the BMW design will effectively be solid under load. In the BMW case the limitation is that the cam faces effectively become vertical, in the Vincent case it is because the top plate stops any further compression of the springs. I'm sure the rider will not be able to feel the difference!</p></blockquote><p></p>
[QUOTE="Tim Kirker, post: 91049, member: 200"] I'm afraid I don't often contribute to the Forum because I just can't find the time to keep up with all the threads I'm interested in, but my attention has been drawn to this discussion about the ESA profile. As draughtsman for the Technical Committee TC, I was insrumental in developing the latest cam design that is now available from VOCSC. The first thing to emphasise is that the TC's terms of reference are not to develop new and improved designs, unless there is clear evidence that the current design is dangerous or clearly an error made by the factory. Our objective is to compile new manufacturing drawings that will allow new parts to be manufactured as close as possible to the original design intent. In the case of the ESA, we came to the view that the then standard of ESA being made was not what PEI originally intended, and had all the faults observed by Vic. So I set out to reproduce a cam profile as close as possible to what PEI originally designed. We did not have original drawings but we did have drawings for the Velocette ESA, also designed by PEI. What I came up with is about the best compromise between that Velocette design and the slightly different surrounding dimensions of the ESA. (Like the amount of axial lift possible, the outer radius etc.) We also looked at some very early Vincent parts, which tended to confirm that the product then available had drifted a long way away from the original design. All of this was written up, at some length, in MPH 808 in May 2016, together with photos similar to Vic's. I'm surprised and disappointed that nobody in this thread has referred back to that article, which I think you will find addresses most, if not all of the concerns raised by Vic and others. We may not have "solved" them in the same way as Vic proposes, but we have solved them pretty well within our terms of reference. The BMW design that Vic is copying is very interesting but is only possible if you accept that the two cams will not be identical, and the drive will be through two lobes, not three - thus you can accommodate a much greater radius in the trough of one side, and a much finer radius for the lobe in the other side. The down side of this approach is that contact between the cams is restricted to two places (or three, if there are three lobes), whereas the Vincent/Velo design has contact in six places. Also, the Vincent lobes are much more robust than Vic's modified lobes. How long before one breaks off? As the Technical Authority for the VOC, the TC cannot take a punt on what might, or might not, work. Our Product Liability Insurance would be blown away. Final thought, I seem to remember that Prof Higgins studied the movement of the ESA with strobe lighting years ago and concluded that it didn't need much torque/revs before the cam locked solid and it looks like the BMW design will effectively be solid under load. In the BMW case the limitation is that the cam faces effectively become vertical, in the Vincent case it is because the top plate stops any further compression of the springs. I'm sure the rider will not be able to feel the difference! [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
New ESA Design
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