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different propulsive forces for "tacking" to climb a hill

rec.bicycles.tech
subject: propulsive forces tacking to climb hill
07nov2

While "tacking" to climb up a steep hill, I found some moves different from normal cycling to help me get up the hill easier: swinging my shoulders sideways up the hill, and using my arms to "sweep" my wheels directly sideways toward down the hill. It enabled me to survive a long steep hill -- and doing it made the climbing sorta fun.

By "tacking" I mean turning my bike diagonally off my overall direction of forward motion, then turning my bike again to go diagonally toward the other side, and repeating to make a sort of curved zig-zag path. Of course I would only do this when I have lots of road-width available with no other vehicles using it. Using a "tacking" path can make it easier to climb up a steep hill by spreading a fixed vertical gain over a much longer horizontal distance -- effectively reducing the hill's steepness, and so reducing the minimum power output required to climb up it with losing control or stopping.

The zig-zag path also offers some different opportunities to add more propulsive work and power for the climbing. I found this out when I wanted to do this long steep climb on a rental bike that didn't have low gears. There was supposed to be an exciting descent on the other side that I wanted to try, but I knew I was going to have to "cheat" to get to the top without lots of walking. It was a remote area on a mid-week day with little car traffic, so I decided to try some "tacking". And that helped make it easier, as expected.

In the midst of the climb I got the idea that I could take some burden off my leg muscles by directly "throwing" the weight of my upper body up the hill. While riding mostly sideways across the hill, just as I started my turn to go the other way, I swung my shoulders sideways up the hill. And that made it easier to pedal thru the turn -- which is the tough part of tacking up a steep hill. This worked for me while pedaling either standing or sitting. So I did those upper body move lots more. Then my abdominal muscles got tired from doing all that the sideways "tossing" -- it's not something I trained for. So I went back to simple pedaling, then did some more sideways tossing again later.

"With this new tool, now I can take on even steeper climbs", I thought. So the next day I decided to try the east side of Colle dell'Agnello on the Italy-France border. It's the third-highest paved mountain pass in Europe, used in the Giro d'Italia recently, sustained steeper than Stelvio (and much steeper than Alpe d'Huez), also an automated time-trial course. Until that day it was unimaginable that I could survive climbing it on a rental bike lacking ultra-low gears. I started early in the morning, very little traffic, and when I reached the sustained steep part I started tacking again, and some of the "sideways shoulder-tossing" move -- and then I thought to try another move:

While pedaling sitting going diagonally across the road, just at the start of the turn to go the other way, I pushed my hand down on the uphill end of the handlebar, and pulled my hand up on the downhill end of the handlebar -- which pushed my wheels directly sideways in the direction diagonally down the hill -- sort of "sweeping" the wheels under me from the uphill side to the downhill side (thus toward the outside of the turn I was going into). It definitely helped me get thru the zig-zag turn more easily. It felt really different to be pushing the wheel directly sideways. And it was fun to play with: different timing of the start and finish of the move relative to the turn, mixing it with the "sideways shoulder toss", standing versus sitting, tighter higher-frequency zig-zags. I was the first rider up to the pass, and I felt so good I rode part of the way down the other side into France and climbed back.

This "wheels side-sweep" move is different from tilting the bike from side to side while standing, because the purpose of that standing move is to add more force thru the legs pushing on the pedals and drivetrain to help the wheels roll forward. This "wheels side-sweep" move also works while pedaling sitting, and transmits force thru the frame and axles directly to the wheels to push directly sideways, not thru the chain and cogs to roll forward. The physics is more like _skating_ than normal bicycling.

On my descent I went by the other cylists climbing the "correct" way, straight up the road in low pedaling frequency. There was no doubt it my mind that cheating with those strange moves was just more fun.

Ken

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