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Happy New Year from all at RCUK! Over the 12 days of Christmas, we’ll be reposting an existing article from this year – one from each month.
Pre-production examples of a radical new chainset concept from 3T proved one of the highlights of RCUK’s first day’s attendance at Eurobike 2010.
The innovative design, named META, has been arrived at following extensive finite-element analysis aimed at determining the precise loadings on a crank and chainrings constructed using the standard five-bolt chainring fixing system. The FEA programme was used to create an overall form and then progressively remove unstressed material from it.
The end result contains the minimum of material and is claimed by 3T to offer a potential weight saving of 30% over the best of current designs with no loss of stiffness.
Said 3T technical director Richard McAinsh: “An important driver in reducing weight was to eliminate the bulky ‘boss’ at the center of the crank spider. We did this by separating the crank and the axle. The axle is now a separate, full-carbon sub-assembly carrying the five mounting points for the crank and chainrings. Our studies showed that this does not have to be heavily reinforced, and in fact the crank itself needs fixing at only three of the five mounting points. This will surprise many, but it’s very clear from the FEA analysis.”
The 3T META crankset is slated for release during 2011.
www.thenew3t.com
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Perhaps the most interesting feature of the META chainset is the separation of the right-hand crank from the chainring spider and bottom bracket axle.
The right-hand crank can be removed without disturbing the chainrings or the bottom bracket bearing assemblies, as can the left-hand crank. This allows mechanics quickly and easily to alter crank length.
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The crank is fixed to the spider using three of its five chainring bolt holes, simultaneously securing the chainrings themselves. The spider is in one piece with the carbon-fibre axle.
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The 3T META right-hand crank arm uses three of the five chainring bolt holes as attachment points and, by integrating the form of the crank arm into that of the spider, achieves a sleek appearance that does not depart to a great extent from the aesthetics of many current composites designs.
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The META left-hand crank employs a short machined aluminium spigot shaped as a Reuleaux triangle with rounded vertices to transmit torque and tapered along its length to ensure a secure fit inside the bottom bracket axle. The crank spigot is retained by a bolt tightened from the right hand side through the spider and axle.
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