The Spares Company
Club Shop/Regalia
Parent Website
Contact Officials
Machine Registrar
Club Secretary
Membership Secretaries
MPH Editor and Forum Administrator.
Section Newsletters
Technical Databases
Photos
Home
What's new
Latest activity
Forums
New posts
What's new
New posts
Latest activity
Information
Bike Modifications
Machine Data Services
Manufacturers Manuals
Spare Parts Listings
Technical Diagrams
Whitakerpedia (Vincent Wiki)
The Club
MPH Material Archive
Flogger's Corner
Obituaries
VOC Sections
Local Sections
Local Section Newsletters
Miscellaneous
Club Assets
Club History
Club Rules
Machine Data Services
Meeting Documents
Miscellaneous
Essential Reading
Magazine/Newspaper Articles/Letters
Adverts and Sales Brochures
The Mighty Garage Videos
Bikes For Sale (Spares Company)
Log in
Register
What's new
New posts
Menu
Log in
Register
Install the app
Install
Home
Forums
Forums: Public Access
Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Golden numbers
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Monkeypants" data-source="post: 45532" data-attributes="member: 2708"><p>Perhaps the 21/46 sprocket combination on the twin was chosen with long wear life in mind. In any case it gets a very good wear index rating from the Gear Commander site. His spelling is weak but the math is correct. <table style='width: 100%'><tr><td><p style="text-align: left"></p> <strong><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">'Same tooth - same link' situation<br /> </span></span></span></strong><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">This happens when the number of links of the chain divided by the number of teeth on a sprocket is a round number. Let's assume you have a chain with 60 links, a front sprocket with 10 teeth and a rear sprocket with 20 teeth. <br /> (F = 10, R =20 L = 60) Not a very realistic situation but easier for the example.</span></span></span><br /> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">The number of Links divided by teeth on Front = L / F = 60 /10 = 6<br /> This means that after six rotations of the front sprocket, the chain made exactly 1 rotation and the first tooth on the front sprocket hits the exact same link of the chain.<br /> <br /> Same goes for the rear: L/R= 60/20=3. So every 3 rotations of the rear sprocket, the chain made 1 complete rotation and the teeth are exactly in the same position again. <br /> So when this chain rotates once, both front and rear sprockets are in the same position and hit the same link all the time. </span></span></span><strong> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #ff0000">This is not good.</span></span></span></strong><br /> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">It would be better if the chain had un uneven number of links, say 61. Since this is not very likely (chains almost always have an even number of links), lets take a chain with 62 links. The calculation now are:</span></span></span><br /> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">Front: L/F = 62/10 = 6.2<br /> Rear: L/R = 62/20 = 3.1</span></span></span><br /> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">This means that after 1 rotation of the chain, the front made 6.2 and the rear 3.1 rotations. This means other teeth hit the same link in the chain ! </span></span></span><strong><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #ff9900">That is better !</span></span></span><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000"> </span></span></span></strong><br /> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">Now how long (how many rotations of the chain) does it take this time for the teeth to hit the same link again? We then have to find the out how many links will have to pass before the division results in an even number. That is the case when we have the LCD of these numbers, the Least Common Multiple. This can be calculated using the GCD, the Greatest Common Denominator. The GCD for 62 and 10 is 2, that is the greatest number both can be dived by which results in an even number.<br /> Now the LCD = the multiple of 62 and 10 divided by the GCD: (62 * 10)/2 = 310.<br /> this means after 310 links, the front sprocket is in the exact same position again. <br /> 310 links means 310 / 62 = 5 rotations of the chain. So when having a china with 62 links instead of 60 links, results in less wear because now only every 5 rotations of the chain, the same tooth is hit.</span></span></span><br /> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">So what would be the optimum number of chain rotations then ? That would be when we have a maximum number of links needed for the same position. So the division LCD = (#1 * #2) / GCD should be maximum. That is the case when GCD = 1 cause the result would then be (#1 * #2) / 1 = #1 * #2.<br /> So when the GCD is 1 we reached our goal. This happens when one of the number is uneven. Lets say we take an 11 sprocket instead of a 10 sprocket, Rear =20 and Links = 60. This results in a GCD of 1 and the number of links needed is: (11 * 60) / 1 = 660 links. This means the chain has to rotate 660/60 = 11 times before the same tooth hits the same link again. <strong>This is the optimum !</strong></span></span></span><br /> <p style="margin-left: 20px"><p style="margin-left: 20px"><strong><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000"> <img src="http://www.gearingcommander.com/help/gc_how27_1.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /> <img src="http://www.gearingcommander.com/help/gc_how27_2.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /></span></span></span></strong><br /> </p> </p> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000"><strong>So what the relative chain wear indicator 'Same tooth - same link' table does</strong>, is showing the number of chain rotations it takes with selected number of teeth and links to hit the same tooth-link combination and also marks them. </span></span></span><br /> <br /> <ul> <li data-xf-list-type="ul"><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">The </span></span></span><strong><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #ff0000">Worst</span></span></span></strong><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000"> is of course 1 rotation (background marked red) when every rotation of the chain all teeth hit the same link all the time. </span></span></span><br /> </li> <li data-xf-list-type="ul"><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">The <strong>Optimal</strong> combination (background marked green) is when the chain has to rotate "the number of teeth on the sprocket" to hit the same tooth again. </span></span></span></li> </ul> <span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">In general, the more chain rotations it takes to hit the same tooth-link or link-tooth combination, the better. <br /> This way you can check if your chosen sprockets and chain are a better or worse combination then to one you have of was stock. So it is relative compared to the other combination, it is no absolute indication for chain wear.</span></span></span><br /> <p style="text-align: center"><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #008000">Next: </span></span></span><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #0000ff"><a href="http://www.gearingcommander.com/base/gc_howto28.htm" target="_blank">Number of tooth-link contacts</a></span></span></span></p> <strong><p style="text-align: center"><span style="font-family: 'Verdana'"><span style="font-size: 10px"><span style="color: #0000ff"><a href="http://www.gearingcommander.com/base/gc_main.htm" target="_blank">Back to Gearing Commander main page</a></span></span></span></p> </strong></td></tr><tr><td></td></tr></table><p><span style="color: #0000ff"><hr /><p></span><p style="text-align: center"> </p></blockquote><p></p>
[QUOTE="Monkeypants, post: 45532, member: 2708"] Perhaps the 21/46 sprocket combination on the twin was chosen with long wear life in mind. In any case it gets a very good wear index rating from the Gear Commander site. His spelling is weak but the math is correct. [TABLE] [TR] [TD][LEFT][B][FONT=Verdana][SIZE=3][COLOR=#008000][/COLOR][/SIZE][/FONT][/B][/LEFT][B][FONT=Verdana][SIZE=2][COLOR=#008000]'Same tooth - same link' situation [/COLOR][/SIZE][/FONT][/B][FONT=Verdana][SIZE=2][COLOR=#008000]This happens when the number of links of the chain divided by the number of teeth on a sprocket is a round number. Let's assume you have a chain with 60 links, a front sprocket with 10 teeth and a rear sprocket with 20 teeth. (F = 10, R =20 L = 60) Not a very realistic situation but easier for the example.[/COLOR][/SIZE][/FONT] [FONT=Verdana][SIZE=2][COLOR=#008000]The number of Links divided by teeth on Front = L / F = 60 /10 = 6 This means that after six rotations of the front sprocket, the chain made exactly 1 rotation and the first tooth on the front sprocket hits the exact same link of the chain. Same goes for the rear: L/R= 60/20=3. So every 3 rotations of the rear sprocket, the chain made 1 complete rotation and the teeth are exactly in the same position again. So when this chain rotates once, both front and rear sprockets are in the same position and hit the same link all the time. [/COLOR][/SIZE][/FONT][B] [FONT=Verdana][SIZE=2][COLOR=#ff0000]This is not good.[/COLOR][/SIZE][/FONT][/B] [FONT=Verdana][SIZE=2][COLOR=#008000]It would be better if the chain had un uneven number of links, say 61. Since this is not very likely (chains almost always have an even number of links), lets take a chain with 62 links. The calculation now are:[/COLOR][/SIZE][/FONT] [FONT=Verdana][SIZE=2][COLOR=#008000]Front: L/F = 62/10 = 6.2 Rear: L/R = 62/20 = 3.1[/COLOR][/SIZE][/FONT] [FONT=Verdana][SIZE=2][COLOR=#008000]This means that after 1 rotation of the chain, the front made 6.2 and the rear 3.1 rotations. This means other teeth hit the same link in the chain ! [/COLOR][/SIZE][/FONT][B][FONT=Verdana][SIZE=2][COLOR=#ff9900]That is better ![/COLOR][/SIZE][/FONT][FONT=Verdana][SIZE=2][COLOR=#008000] [/COLOR][/SIZE][/FONT][/B] [FONT=Verdana][SIZE=2][COLOR=#008000]Now how long (how many rotations of the chain) does it take this time for the teeth to hit the same link again? We then have to find the out how many links will have to pass before the division results in an even number. That is the case when we have the LCD of these numbers, the Least Common Multiple. This can be calculated using the GCD, the Greatest Common Denominator. The GCD for 62 and 10 is 2, that is the greatest number both can be dived by which results in an even number. Now the LCD = the multiple of 62 and 10 divided by the GCD: (62 * 10)/2 = 310. this means after 310 links, the front sprocket is in the exact same position again. 310 links means 310 / 62 = 5 rotations of the chain. So when having a china with 62 links instead of 60 links, results in less wear because now only every 5 rotations of the chain, the same tooth is hit.[/COLOR][/SIZE][/FONT] [FONT=Verdana][SIZE=2][COLOR=#008000]So what would be the optimum number of chain rotations then ? That would be when we have a maximum number of links needed for the same position. So the division LCD = (#1 * #2) / GCD should be maximum. That is the case when GCD = 1 cause the result would then be (#1 * #2) / 1 = #1 * #2. So when the GCD is 1 we reached our goal. This happens when one of the number is uneven. Lets say we take an 11 sprocket instead of a 10 sprocket, Rear =20 and Links = 60. This results in a GCD of 1 and the number of links needed is: (11 * 60) / 1 = 660 links. This means the chain has to rotate 660/60 = 11 times before the same tooth hits the same link again. [B]This is the optimum ![/B][/COLOR][/SIZE][/FONT] [INDENT][INDENT][B][FONT=Verdana][SIZE=2][COLOR=#008000] [IMG]http://www.gearingcommander.com/help/gc_how27_1.gif[/IMG] [IMG]http://www.gearingcommander.com/help/gc_how27_2.gif[/IMG][/COLOR][/SIZE][/FONT][/B] [/INDENT][/INDENT][FONT=Verdana][SIZE=2][COLOR=#008000][B]So what the relative chain wear indicator 'Same tooth - same link' table does[/B], is showing the number of chain rotations it takes with selected number of teeth and links to hit the same tooth-link combination and also marks them. [/COLOR][/SIZE][/FONT] [LIST] [*][FONT=Verdana][SIZE=2][COLOR=#008000]The [/COLOR][/SIZE][/FONT][B][FONT=Verdana][SIZE=2][COLOR=#ff0000]Worst[/COLOR][/SIZE][/FONT][/B][FONT=Verdana][SIZE=2][COLOR=#008000] is of course 1 rotation (background marked red) when every rotation of the chain all teeth hit the same link all the time. [/COLOR][/SIZE][/FONT] [*][FONT=Verdana][SIZE=2][COLOR=#008000]The [B]Optimal[/B] combination (background marked green) is when the chain has to rotate "the number of teeth on the sprocket" to hit the same tooth again. [/COLOR][/SIZE][/FONT] [/LIST] [FONT=Verdana][SIZE=2][COLOR=#008000]In general, the more chain rotations it takes to hit the same tooth-link or link-tooth combination, the better. This way you can check if your chosen sprockets and chain are a better or worse combination then to one you have of was stock. So it is relative compared to the other combination, it is no absolute indication for chain wear.[/COLOR][/SIZE][/FONT] [CENTER][FONT=Verdana][SIZE=2][COLOR=#008000]Next: [/COLOR][/SIZE][/FONT][FONT=Verdana][SIZE=2][COLOR=#0000ff][URL="http://www.gearingcommander.com/base/gc_howto28.htm"]Number of tooth-link contacts[/URL][/COLOR][/SIZE][/FONT][/CENTER][B][CENTER][FONT=Verdana][SIZE=2][COLOR=#0000ff][URL="http://www.gearingcommander.com/base/gc_main.htm"]Back to Gearing Commander main page[/URL][/COLOR][/SIZE][/FONT][/CENTER][/B][/TD] [/TR] [TR] [TD][COLOR=#0000ff][/COLOR][/TD] [/TR] [/TABLE] [COLOR=#0000ff][HR][/HR][/COLOR][CENTER] [/CENTER] [/QUOTE]
Insert quotes…
Verification
What was Mr Irving's Christian Name?
Post reply
Home
Forums
Forums: Public Access
Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Golden numbers
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
Accept
Learn more…
Top