Smaller chainrings for English 3 speeds.
02-16-08, 10:14 PM
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Smaller chainrings for English 3 speeds.
When a person needs very low gears, sometimes bigger cogs aren't enough. There was a question about this on an earlier, mis-titled thread.
Today I installed a 40t chainring on my wife's 1965 Robin Hood, without the expense of alloy cranks and a new BB. I had salvaged a set of cottered 6-1/2" cranks, with detachable chainrings, from a small frame Raleigh Grand Prix 10 speed. I installed a single 40t ring in place of the 40-52 pair.
I had to raise the chainguard to clear the 3 arms of the spider as there isn't much offset between the spider and the arm. The arm clears the chainguard by about 2mm on the outside.
I've occasionally had trouble with the chain jumping off of larger rear cogs made from freewheel or cassette cogs. I am curious if it had anything to do with running 1/8" chain on them. The 40t ring is made for derailleur chain so I installed one, and a 26t cog made by welding a Suntour freewheel cog to an SA cog with the teeth machined off.
With her S5 hub she now has gears of 60, 51, 40, 32 & 27 inches. Too low for most people, but she's not too fast, coasts downhill and is a spinner.
Today I installed a 40t chainring on my wife's 1965 Robin Hood, without the expense of alloy cranks and a new BB. I had salvaged a set of cottered 6-1/2" cranks, with detachable chainrings, from a small frame Raleigh Grand Prix 10 speed. I installed a single 40t ring in place of the 40-52 pair.
I had to raise the chainguard to clear the 3 arms of the spider as there isn't much offset between the spider and the arm. The arm clears the chainguard by about 2mm on the outside.
I've occasionally had trouble with the chain jumping off of larger rear cogs made from freewheel or cassette cogs. I am curious if it had anything to do with running 1/8" chain on them. The 40t ring is made for derailleur chain so I installed one, and a 26t cog made by welding a Suntour freewheel cog to an SA cog with the teeth machined off.
With her S5 hub she now has gears of 60, 51, 40, 32 & 27 inches. Too low for most people, but she's not too fast, coasts downhill and is a spinner.
02-17-08, 07:45 AM
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Wow, those are some VERY LOW gears. My singlespeed is 74 gear inches. That's some good ingenuity at work, though.
Was your chainline nice and straight? If it wasn't, the thicker, less flexible chain may have had trouble and would decide to jump at the first sign of stress; ie. a big hill. My WAG of the morning, anyways.
Was your chainline nice and straight? If it wasn't, the thicker, less flexible chain may have had trouble and would decide to jump at the first sign of stress; ie. a big hill. My WAG of the morning, anyways.
02-17-08, 10:33 AM
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I think I'm the author of the mistitled thread you mentioned earlier. That's a resourceful setup--I may try something like it. It's a challenge riding a three-speed in the headwaters of the Vermont valley where I live, because I have to grind up almost a mile of 10 percent grade on a dirt road (maxing out at about 13 percent) to get back to my house after every ride. I experimentally had a 28-toooth cog on back for a time, and it did give a comfortably low gear for the big hills, even though that meant pedaling around in high on anything approaching flat, and quickly spinning out. But my feeling is that the old three-speeds are more about comfort than speed, anyway. I think Howlin' Wolf used to ride one.
My hope in finding a larger Raleigh Sports chainring/crankarm was to retain the cool-looking heron design on the chainring. Vanity, vanity, all is vanity.
My hope in finding a larger Raleigh Sports chainring/crankarm was to retain the cool-looking heron design on the chainring. Vanity, vanity, all is vanity.
