52T vs 70T (pic)
#26
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The Bonneville bike that made the news last year used the mid drive from a Da Vinci tandem to achieve the needed ratio
#27
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This thread...cant say it delivers quite yet, but it's shaping up to!
#28
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With a Schlumpf High Speed , 2.5 X overdrive internally geared crankset
you could do a 70t equivalent with a 28t actual chainring...
you could do a 70t equivalent with a 28t actual chainring...
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Your "reality" is clearly not everyone else's reality. Aka, your inadequacy only reflects on others via all-knowing over confident narcissism... "It's physically impossible". What a bold statement from someone who can't push 38-11 up a mild gradient.
You didn't mention anything regarding my bet? What are you hesitant about? Aren't you confident in your super modest knowledge of cycling and gearing?
You didn't mention anything regarding my bet? What are you hesitant about? Aren't you confident in your super modest knowledge of cycling and gearing?
I'm guessing it's going to be fully faired for some kind of record attempt. Two weeks is going to be a long time.
#30
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Thanks!
--edit after some quick research, apparently you lose up to 5% efficiency. And considering it's over 800$, you could find a 70t chainring for less than 100$. Only benefit is the ability to hit a lower gear. Cool but not for me.
Last edited by tellmethetruth; 03-17-19 at 08:27 PM.
#35
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#36
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On a tandem, I’ve wanted more than 54X11. But that riding partner is no longer around.
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Vintage, modern, e-road. It is a big cycling universe.
Vintage, modern, e-road. It is a big cycling universe.
#38
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That 70T would be a little high for a lowracer with a 20" drive wheel but not outrageous. Good for someone who doesn't like spinning, or maybe just doesn't like using an 11T cog in back.
Schlumpf speed drive? Internally-geared bottom bracket with a +2.5x multiplier. 28 Teeth becomes 70 Teeth in Overdrive.
Schlumpf speed drive? Internally-geared bottom bracket with a +2.5x multiplier. 28 Teeth becomes 70 Teeth in Overdrive.
#39
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104-teeth
#40
Non omnino gravis
The OP has never made any sort of indication that this is about a recumbent, just that he's going to do 50mph on flat ground. Even if it does turn out to be something not diamond-framed, we're looking at a sustained effort of ~120rpm @ 1,300-1,400W. Unless it's fully faired, in which case who cares. Fully faired can go really fast without a pie-plate in the front.
#41
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I find it interesting to try different things. I'll be curious how this turns out. No harm in trying.
#42
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I mean, it exists for a reason to be sold. I can't criticize what it would be used for if I don't even know, that's silly.
People use 60T front rings on normal TT bikes in flatter courses. Avoiding using the 11t or 12t can save watts worth paying attention to. And since two in the front is worth one in the back, going from 50t/11 to a 13 for efficiency would mean needing a 54t in front. Downwind or downhill you'd use it.
I'd assume for speed records you wouldn't want a ludicrous cadence as it might hurt the stability of the rig.
People use 60T front rings on normal TT bikes in flatter courses. Avoiding using the 11t or 12t can save watts worth paying attention to. And since two in the front is worth one in the back, going from 50t/11 to a 13 for efficiency would mean needing a 54t in front. Downwind or downhill you'd use it.
I'd assume for speed records you wouldn't want a ludicrous cadence as it might hurt the stability of the rig.
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#44
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The OP has never made any sort of indication that this is about a recumbent, just that he's going to do 50mph on flat ground. Even if it does turn out to be something not diamond-framed, we're looking at a sustained effort of ~120rpm @ 1,300-1,400W. Unless it's fully faired, in which case who cares. Fully faired can go really fast without a pie-plate in the front.
The world record for fully-faired upright on level ground with no outside assist is 51.28 mph on a Moulton AM 7. That record is about 33 years old. Jim Glover did that with a full cowl and 82x10 gearing.
Godspeed OP!
#45
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That's not the way ratios work. The difference between 11 and 13 is roughly 18%. The difference between 50 and 4 is roughly 8%. You'd need a 59t paired with a 13t for the gear ratio to be the same as the 50/11
#47
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If you're upright, without fairing, and entirely unassisted, you're going to hit a brick wall of wind well below 50 mph, I don't care how fit you are. The evidence for that is simple--no one on earth has ever done it.
Even with fairing, the 30+ year old world record is only 51.28 mph, upright and unassisted. And that was done with a much bigger gear ratio than you're using.