This letter in published in the October issue of months Motorcycle Consumer News.
I am a former MC dealer, gear head, analytical type, well read in MC engineering (just finished Tony Foales new book, thank you for printing the info on it in a prior issue) have worked as a MC mechanic and built hundreds of wheels. Regarding the letter from John Fredrikson on the failure of an aftermarket wheel, page 4 of August 2002. When I read it I wondered if this was finally a wake up call for a style of wheel that I keep seeing on Harleys that is designed so wrong it makes my skin crawl! I contacted John, he emailed me before & after photos and it is the design I had worried about! In the interest of public safety we need you to expose this to the next level.
In a proper spoke wheel all spokes are under tension only! To illustrate visualize a wheel that the spokes are made of cable! Cable will hold tension, not compression or bending forces and that is how a proper spoke wheel is designed. In a proper spoke wheel the spoke angles from the rim to a point partly wrapped around the hub with each spoke crossing the others. There are several patterns such as "Cross one", "Cross two" "Cross three” ETC., each having more angle to the spoke than the prior which wraps further around the hub and the more a sharp load pulls the hub together instead of apart! In all of those designs there are spokes going in 4 directions, clockwise angled right, clockwise angled left, counter clockwise angled right and counter clockwise angled left. When the bike is at rest a minimum of four spokes are at or near straight up and are suspending the bike thru tension! When power is applied all of the spokes that go clockwise (viewed from the right from hub to rim) are under tension and at no time is a compression or bending load applied to a spoke! That spoke angularity is crucial for coping with acceleration and braking forces!
The design that failed on John’s HD had 40 spokes ½” in diameter in a “Cross Zero” design AKA Radial (as if that was a good thing)! In such as designing the spokes are under tensions at rest but under a bending load under power or braking loads! They use huge spokes such as ½” on the subject wheel so the spoke can cope with the application of torque but as happened here it ripped open the spoke holes. That style wheel should be limited to the auto shows only but are being sold for street use. John is a mature police office with a show grade HD so I doubt he was abusing it but it should withstand anything you can do to it including most crashes anyway, it ripped the spokes out of the rim with only 300 miles of touring type use.
Engineers have worked for decades to bring the motorcycle to where it is today and someone who does not understand the design principles can endanger their customers lives by ignoring sound engineering principles and developing a product that is based on a “look”!
I am a former MC dealer, gear head, analytical type, well read in MC engineering (just finished Tony Foales new book, thank you for printing the info on it in a prior issue) have worked as a MC mechanic and built hundreds of wheels. Regarding the letter from John Fredrikson on the failure of an aftermarket wheel, page 4 of August 2002. When I read it I wondered if this was finally a wake up call for a style of wheel that I keep seeing on Harleys that is designed so wrong it makes my skin crawl! I contacted John, he emailed me before & after photos and it is the design I had worried about! In the interest of public safety we need you to expose this to the next level.
In a proper spoke wheel all spokes are under tension only! To illustrate visualize a wheel that the spokes are made of cable! Cable will hold tension, not compression or bending forces and that is how a proper spoke wheel is designed. In a proper spoke wheel the spoke angles from the rim to a point partly wrapped around the hub with each spoke crossing the others. There are several patterns such as "Cross one", "Cross two" "Cross three” ETC., each having more angle to the spoke than the prior which wraps further around the hub and the more a sharp load pulls the hub together instead of apart! In all of those designs there are spokes going in 4 directions, clockwise angled right, clockwise angled left, counter clockwise angled right and counter clockwise angled left. When the bike is at rest a minimum of four spokes are at or near straight up and are suspending the bike thru tension! When power is applied all of the spokes that go clockwise (viewed from the right from hub to rim) are under tension and at no time is a compression or bending load applied to a spoke! That spoke angularity is crucial for coping with acceleration and braking forces!
The design that failed on John’s HD had 40 spokes ½” in diameter in a “Cross Zero” design AKA Radial (as if that was a good thing)! In such as designing the spokes are under tensions at rest but under a bending load under power or braking loads! They use huge spokes such as ½” on the subject wheel so the spoke can cope with the application of torque but as happened here it ripped open the spoke holes. That style wheel should be limited to the auto shows only but are being sold for street use. John is a mature police office with a show grade HD so I doubt he was abusing it but it should withstand anything you can do to it including most crashes anyway, it ripped the spokes out of the rim with only 300 miles of touring type use.
Engineers have worked for decades to bring the motorcycle to where it is today and someone who does not understand the design principles can endanger their customers lives by ignoring sound engineering principles and developing a product that is based on a “look”!
