In an earlier post on the new Sam Hillborunes coming in Sept,
“New batch of Sam Hillbornes this fall” 5/16/20 The discussion went OT to the longer top tubes RBW uses in the MIT Atlantis, and the need for shorter stems when using drop bars . Patrick Moore expressed concerns about the stability of short stems: “How do such short stems affect the handling of the Atlantis?” I went to my copy of Bicycling Science, 3rd Edition, 2004, and read the chapter on Steering & Balancing. One main point made is the importance of Mechanical Trail, steering torque, and the fact the steering axis is inclined to the horizontal and is not vertical or near vertical on the stability of a bicycle. I assume stability and handling are somewhat synonymous. I made a new post for this issue I could not find any discussion of stem length, except on pages 288-289, in a qualitative discussion on the importance of the ‘tilted’ steering axis. I typed the words from this section below. The text includes a personal communication from John Allen discussing the effects of stem length on stability. Instability section of Chapter 8 Steering & Balancing Bicycling Science, 3rd Edition, 2004, pages 288-289, Nonoscillatory Instability section of Chapter 8 Steering & Balancing “ Who was the genius who thought of tilting a bicycle’s steering axis? And was this tilting valued for its stability benefits, or for something more mundane like minimizing hand-force steering disturbances during stand up pedaling or preventing rearward bending damage from striking a pothole (Brandt 2000)? The development of a tilted steering axis is one of the major mysteries of bicycle evolution. John Allen (2001 personal communication) writes: ‘In the early days of the safety bicycle, the handlebars were placed close to the cyclist, as had been the tradition and necessary with high wheelers, with their very serious pitchover problem. High wheelers had little or no forward angling of the front fork: it would not have been practical because it would have prevented the cyclist from standing over the pedals , and would have placed the force vector from pedaling too far from the steering axis, making steering difficult. Bicycle evolution involved innumerable experiments, but the answer is most likely mundane: the fork was angled forward in order to keep the handlebars close to the cyclist, and for the front wheel to clear the feet, in spite of what intuitively would seem to be a stability reduction. This development occurred before the discovery (by Major Taylor?) that a greater distance to the handlebars improved both power production and aerodynamics. A longer stem also greatly improves stability when riding with one hand on the handlebar, an important side benefit which would not accrue simply by lengthening the top tube and keeping the fork vertical’” It seems the only stability issue with a shorter stem would be some decrease in stability when riding with one hand on the bar. John Hawrylak Woodstown NJ -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/7aeafb41-aca2-4594-8bc3-e999739c6c10%40googlegroups.com.
