Re: [workbike] PIGS (long)

jim gregory wrote:

> As you have pointed out before, bicycle gearing makes it
> possible for one to exert a greater tractive effort (=
> force) using a bike than could be exerted without using a
> bike.  Wouldn't it be easier to ride the bike up the hill
> rather than push it if the bike was geared lower than 1:1?
> Granted, it would take longer, but then that's the tradeoff
> again between speed vs. effort....

Your are absolutely correct of course, that if the gearing 
is better than 1:1 the HPV could be better use of human 
effort than the shoe. At that point the wheeled vehicle 
becomes a force multiplier.  Depending on drive train 
efficiency, for a 170 mm crankset, force in will equal 
force out at about 12 - 13 Gear inches.

Yet, there might be a practical limit to gearing on a 
bicycle based on how slow one can ride. Slightly, 
under 2 mph (3.2 km/h) I find walking easier than dealing 
with the wobblies, upright or recumbent.  Not an problem 
with a multi-track vehicle. 

The other concideration of how-low-can-we-go might be 
determined by "good" tire friction -- tractor style traction. 
It is fully possible to gear down low enough to generate a
force that exceeds the point where the tires begin to slip.

I remember recently towing the trailer with a couple sacks 
of concrete on board (100 lb. ea.) . Gravel road of course. 
Short steep hill naturally. Gonna' show those young 
whipper-snappers in their pickup trucks how it's done. I 
stood up on the pedals, grabbed the bar-ends of the MtB and 
honked down hard. ...and the back wheel just spun around 
and around  kicking up a little handful of rocks. The bike 
didn't move. So much for looking cool. As soon as I hopped 
off the bike the tongue and back wheel scissored up into 
the air. I finished the climb pushing while leaning an elbow 
on top of the saddle. A humble but honorable way of getting 
to the top.

John

• References:
  • Re: [workbike] PIGS (long)
    • From: "jim gregory" <jim@bikesatwork.com>