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12 July, 2013
The Quad Crank
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This what happens when we have too much free time. It's a Grand Cru 50.4bcd crank set up with four chainrings. In this case it's a twin half-step. This may have possibilities, instead of running a 1x5 on your city bike, you could run a 4x1. Or how about a 4x11--so many gears? Boggles the mind.
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In other news: We have the Maryland made Grand Cru handlebar bags in stock again. The first production run sold out fast.
We also have these cool stickers. You'll get one free with every order, and you can order extras.
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9 comments:
Seems to me you should use this with a Rohloff -- 50-47 gives you 28 about equally spaced gears (6% gaps going down). 50-48-46 gives you 42 and 3% gaps. To get 4 without using fractional teeth, I think you need a tiny cog in the rear and 35-34-33-32 in front (13T cog in the rear, sub-100kg rider).
I concur. You have too much time on your hands.
This calls for a Sturmey Archer 3-speed cassette hub + a 10 speed cassette (11, if you can fit it on there). 120 mostly-useless gear ratios!
Sheldon lives!
Alex Singer did a similar thing.
Phil Brown
At the suggestion of my engineer brother, I put a double chainwheel on a bike that has an 8-speed Alfine hub with a chain tensioner. It works surprisingly well, giving 16 usable gears in perfect half-step, while retaining the ability to shift while coasting or standing still.
But does it plane?
My DaVinci tandem has a quad crank. Low gear is 24/34 and high gear is 60/11. I call that outer chain ring "HyperDrive"
I put a quad crankset on our tandem for a while - the chainline is quite wide so there was room to put a second inner ring on the 74 mm BCD mounts. We then had 24-32-42-54 with a 12-28 10-speed cassette. The front deraileur only JUST had enough range to get the chain to move to the inner and outer rings, but it sometimes took a bit of effort and timing. We've since gone back to a more conventional setup with 26-39-52 rings and an 11-32 cassette.
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