XPost: alt.home.repair, alt.sci.physics, uk.d-i-y   
   From: CFKinsey@military.org.jp   
      
   On Fri, 25 Jan 2019 09:34:50 -0000, NY  wrote:   
      
   > "Commander Kinsey"  wrote in message   
   > news:op.zv490lwywdg98l@desktop-ga2mpl8.lan...   
   >   
   >> I knew steering played a big part (I thought about 50%) because I've seen   
   >> a trick played where people are given bicycles with fixed steering, and   
   >> it's very difficult to balance on them.   
   >   
   > Also there have been tests where a perfectly balanced human-size/weight   
   > dummy is attached to a bike, and it falls over even when it is travelling at   
   > a speed that a human could ride easily. That suggests that minute   
   > adjustments to balance and steering are a major factor in staying upright.   
   >   
   >> I'm sure the wheels play a big part too - if you remove a bicycle wheel   
   >> and keep the hub, then spin it holding the wheelnuts, it's difficult to   
   >> turn over.  Mind you, maybe that's not enough to prevent the weight of the   
   >> rider falling over too.   
   >   
   > That's the gyroscopic effect. If the wheel is rotating and you twist the   
   > axle side-to-side (in a horizontal plane), there is a force that tries to   
   > twist the axle up-and-down (in a vertical plane). It acts so as to correct a   
   > tendency to fall over: if you start to lean to the left and the front axle   
   > turns to the left, the gyroscopic force acts to try to move the bike back to   
   > vertical, and its magnitude varies with speed.   
   >   
   > I can see why people though that this was the only force that mattered,   
   > since it does play a small part in keeping balance - it's just that it's not   
   > enough on it own.   
      
   I would have said a large part.  Just try balancing on a bicycle that's   
   stationary.   
      
   > I read of an experiment where a bike was fitted with wheels that had discs   
   > of equal mass to the wheel that were rotated (electrically) in the opposite   
   > direction so as to cancel out any gyroscopic force. And the bike was still   
   > rideable, though it was slightly harder to keep one's balance.   
      
   I guess it's also harder if you have a very lightweight racing bike with   
   lighter wheels.  Mind you, I could never ride a bike with narrow handlebars, I   
   can only ride mountain bikes.  Not enough leverage to balance by steering in   
   those drop handlebar    
   types.   
      
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