June 9, 2004
MnHPVA Meeting 		Notes by Tim Dunsworth and Mark Stonich

Photos & HTML: Mark Stonich
Meeting Notes Below
Show-N-Tell Pages
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There was a long enough gap in the on-and-off rain we had all week so that we could stay out in the parking lot until about 7:30 before going in to the large meeting room. People spent that time schmoozing and trying out Carl's Ego electric scooter and Mark's three speed recumbent.
Carl showed a few miscellaneous goodies:
  • The front half of a small push scooter, free for the taking, that could theoretically be used for a folding something or other (?).
  • A Rotor crank with two sets of pedal holes to offer regular and short lengths. He will loan it out to anyone with a serious interest in trying it out and reporting back to the group.
  • A nice foldable cargo trailer that attaches to his Ego scooter, and is made by the same company.
  • A set of Shimano MTB controls that were an attempt to do a MTB version of their combined brake and shift controls. It didn't go over too well with the MTB crowd, so Carl thinks they may be available fairly cheap if one has the right contacts. They seemed pretty slick, though they were made for use with hydraulic brakes and thus wouldn't be useable for very many of us.
Mark gave us a short report on this year's 3 Speed Tour of Lake Pepin. There were inquiries from 35-40 riders, but with iffy weather only about 28 showed up, from as far away as Winnepeg and St. Louis. The weather actually cooperated pretty well (just enough drizzle to make it a proper British ride!), and everyone seemed to have a good time. The bikes ranged from a $5 garage sale special to a painstakingly (and expensively) restored semi-antique. Mark said he has never seen so many British Carridice saddle bags in one place, and there was a special photo op just so people could get a picture of them all in a line. Mark would like it known that Jane, his asthmatic, great-grandmother of a wife, was one of those who made the Bay City hill without walking.
Mark showed some tires, which led to a brief digression onto the subject of rolling resistance. Basically, Mark trying to get Carl straight on how a small fat tire could possibly be a good roller (Carl swears by the 700 x tiny tire on the back of his Gold Rush). Rolling resistance is a complicated issue involving tire width and diameter and pressure and construction in relation to rider weight and surface characteristics, but Mark's main point is that a fat tire can roll very nicely if it is built with a relatively thin and flexible carcass. Even at speeds where a fatty it isn't quite as fast on a smooth road, it can still be faster on a rough road because it flexes to absorb bumps so easily. Chris Burbank had recently competed in the State Time Trial Championships, where he noticed a 1.5 to 2 mph loss of speed on the rougher parts of the course.

A fat tire is especially beneficial at smaller diameters because it doesn't have to flex as much as a narrower tire to produce the required contact patch size (which is determined by the total weight divided by the tire pressure and would be about 2.5 square inches total for front and rear tires on my bikes, or about 4 square inches on Mark's lower pressure ones). On a smooth velodrome or race course the ideal may still be a narrow and very high pressure tire of 26” or 700c diameter, but in the real world (especially the world of recumbents) something smaller and fatter can perform quite well.

Turned out the club champion of bad rolling resistance is probably Dennis Diekhoff, who swears by Hookworm tires for their durability but is then stuck with their very stiff carcasses (made even worse by the thorn-proof tubes he runs in them). This is one case where higher pressure may be good (or necessary anyway) in a fat tire just to reduce the amount that stiff bugger has to flex to form the required size contact patch.

Mark's comment; The bigger issue is the total resistance of a tire, aero and rolling combined. If you double the speed, it takes twice as much power to overcome rolling resistance, but 8 times the power to overcome aero drag. So, there is a speed above which a good skinny tire will have less total resistance than a good fat tire. While the exact velocity at which this crossover occurs will vary with load, road conditions and which two tires are being compared, I'm sure I spend much more time below this speed than above it.

Editorial comment
I've often written words to the effect that sometimes a basement full of tools and decades of experience reduce the need for imagination when building bikes. I should clarify this.

To solve any given problem, the guy with the fewest resources needs the most imagination. However, in order to keep the brain cells challenged, guys with experience, skills, too many tools etc. simply take on projects other people wouldn't or couldn't.

To confirm this hypothesis, check out any of Chis Burbank's recent "Show-N-Tell" presentations.

Mark Stonich       
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