Fabian
Well-Known Member
Originally i used a tetra chainwheel system which allowed me to have 3 chainrings to power the final drive. In operation i rarely used the midrange gear (being the dished 30 tooth sprocket) so i've ditched the tetra chainwheel system and gone for a tri-wheel setup; removing the 30 tooth sprocket from the final drive and only using the 24 tooth sprocket as "low range" and the 38 tooth sprocket as "high range.
The dished 30 tooth sprocket still stays in the system but is now reversed to enable a lead-in ramp when the chain jumps to the 38 tooth sprocket. By doing this, there can be a larger gap between the 48 tooth jackshaft sprocket and the 38 tooth final drive sprocket, and a smaller gap between the 24 tooth sprocket and the 38 tooth sprocket, much better mimicking the sprocket gap found on a mountain bike triple chainwheel setup, which works in nicely with the indexing of a typical front derailleur.
A side note: the need for a right hand side chain tensioner can be plainly seen in the photo, as the front wheel sand blasts the chain drive system when on dirt roads. I have had chain stretch go from 25% to 80% in around 3 hours riding a trail that has a surface consisting of Lilydale Topping (a combination of sand, fine stones and cement powder) which is exactly what you see sand blasted onto the sprockets in the photo.
This particular surface mercilessly grinds away at the sprocket teeth and chain, and without a chain tensioner you are forever stopping to get out your spanners and adjust the tensioning rod.
The dished 30 tooth sprocket still stays in the system but is now reversed to enable a lead-in ramp when the chain jumps to the 38 tooth sprocket. By doing this, there can be a larger gap between the 48 tooth jackshaft sprocket and the 38 tooth final drive sprocket, and a smaller gap between the 24 tooth sprocket and the 38 tooth sprocket, much better mimicking the sprocket gap found on a mountain bike triple chainwheel setup, which works in nicely with the indexing of a typical front derailleur.
A side note: the need for a right hand side chain tensioner can be plainly seen in the photo, as the front wheel sand blasts the chain drive system when on dirt roads. I have had chain stretch go from 25% to 80% in around 3 hours riding a trail that has a surface consisting of Lilydale Topping (a combination of sand, fine stones and cement powder) which is exactly what you see sand blasted onto the sprockets in the photo.
This particular surface mercilessly grinds away at the sprocket teeth and chain, and without a chain tensioner you are forever stopping to get out your spanners and adjust the tensioning rod.
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