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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
New Gearbox: Help Needed
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<blockquote data-quote="oexing" data-source="post: 106090" data-attributes="member: 1493"><p>Paul,</p><p>I guess you are thinking of a shape like that below from a /5 series BMW box, with all these humps on the o.d. of the camplate :</p><p></p><p>[ATTACH=full]26638[/ATTACH]</p><p></p><p> Actually that was meant to be an "improvement" to the older shape similar to the Vincent camplate. The older BMW plate was like this:</p><p>[ATTACH=full]26639[/ATTACH]</p><p></p><p>You can see the indexing lever just above the camplate, that is where I got my idea from for my mod to the poor Vincent indexing plunger type which induces a lot of friction in its bore from side loads when shifting gear. </p><p> I said the new type of camplate on the 2 valve flat twin BMWs was a bad idea because all gears in a BMW gearbox do about crankshaft speeds , no reduction from a primary drive there. So gearchanges are widely known to be very clunky on these BMs when going down , say, from third to second gear as you are faced with big differential in gear speeds at a high reving gearbox. </p><p> With the older type of camplate, circular o.d. , you have the chance to find a "false" neutral between all gears so you can perform truck/ tractor changes like on unsynchronized boxes. </p><p> I got my 1965 R 69 S in 1972 so am used to its gearbox quite well. So it is second nature to do downshifts with false neutrals and extra clutch action so real SILENT gear changes on a BMW for sure. I had clutch Bowden wires snap once or twice far from home so this came very handy to do gear shifts without clutch at all BUT using false neutrals for silent changes nevertheless. No way to do that with the humped camplates ! </p><p>Well, this is no argument with the Vincent gearbox, certainly. When looking at the Vincent camplate I do not see a lot of scope for extra humping: You´d have to shorten the bore of the plunger pin but same time it had to do a longer stroke into the deeper v-slots, making things even worse friction-wise with the pin-in-bore design. In that case the lever indexer would help a lot - I hope. </p><p></p><p> Vic</p><p>[ATTACH=full]26640[/ATTACH]</p></blockquote><p></p>
[QUOTE="oexing, post: 106090, member: 1493"] Paul, I guess you are thinking of a shape like that below from a /5 series BMW box, with all these humps on the o.d. of the camplate : [ATTACH type="full"]26638[/ATTACH] Actually that was meant to be an "improvement" to the older shape similar to the Vincent camplate. The older BMW plate was like this: [ATTACH type="full"]26639[/ATTACH] You can see the indexing lever just above the camplate, that is where I got my idea from for my mod to the poor Vincent indexing plunger type which induces a lot of friction in its bore from side loads when shifting gear. I said the new type of camplate on the 2 valve flat twin BMWs was a bad idea because all gears in a BMW gearbox do about crankshaft speeds , no reduction from a primary drive there. So gearchanges are widely known to be very clunky on these BMs when going down , say, from third to second gear as you are faced with big differential in gear speeds at a high reving gearbox. With the older type of camplate, circular o.d. , you have the chance to find a "false" neutral between all gears so you can perform truck/ tractor changes like on unsynchronized boxes. I got my 1965 R 69 S in 1972 so am used to its gearbox quite well. So it is second nature to do downshifts with false neutrals and extra clutch action so real SILENT gear changes on a BMW for sure. I had clutch Bowden wires snap once or twice far from home so this came very handy to do gear shifts without clutch at all BUT using false neutrals for silent changes nevertheless. No way to do that with the humped camplates ! Well, this is no argument with the Vincent gearbox, certainly. When looking at the Vincent camplate I do not see a lot of scope for extra humping: You´d have to shorten the bore of the plunger pin but same time it had to do a longer stroke into the deeper v-slots, making things even worse friction-wise with the pin-in-bore design. In that case the lever indexer would help a lot - I hope. Vic [ATTACH type="full"]26640[/ATTACH] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
New Gearbox: Help Needed
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