Zencranks???
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This is the point at we disagree.
The effective length of a crank is set by the distance from the center of rotation to where the driving force is applied. As long as the offset pedal is still attached to a bearing at 175mm from the center of rotation, it's a 175mm crank. Putting blocks on the pedal doesn't change that. The key is where the bearing is located and the line of force applied through that bearing.
If you consider this to act like a 190mm crank (with or without blocks) you've accepted the seller's premise, something which I don't. Think about this a while, and maybe you'll be the one to come around this time.
The effective length of a crank is set by the distance from the center of rotation to where the driving force is applied. As long as the offset pedal is still attached to a bearing at 175mm from the center of rotation, it's a 175mm crank. Putting blocks on the pedal doesn't change that. The key is where the bearing is located and the line of force applied through that bearing.
If you consider this to act like a 190mm crank (with or without blocks) you've accepted the seller's premise, something which I don't. Think about this a while, and maybe you'll be the one to come around this time.
the 175 on the chart is comparing their 190 with a standard 175. They are selling people longer cranks than they normally ride. If you ride a 170, they sell you a 178 (their shortest size)
Last edited by thirdgenbird; 09-07-13 at 11:42 AM.
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Correct. It is a 190mm crank from bb to spindle. They don't even sell a 175. We both agree on the physics but you think we are talking about a 175mm crank but we are not
the 175 on the chart is comparing their 190 with a standard 175. They are selling people longer cranks than they normally ride. If you ride a 170, they sell you a 178 (their shortest size)
the 175 on the chart is comparing their 190 with a standard 175. They are selling people longer cranks than they normally ride. If you ride a 170, they sell you a 178 (their shortest size)
IMO - Those tall enough to want these would be much better served with a higher BB, than this nonsense. Another alternative would be to use a Phil Centric BB mounted in the top position to raise the center of rotation without any drawbacks except the dough spent.
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OK, I missed that it their claims. So what we have in essence is a 190mm crank with the cornering pedal clearance of a 175mm crank. So any claims related to power are BS. I guess that if you really wanted 190mm cranks, and didn't want to coast through hard corners, or use the motorcyclists maneuver of leaning the body more than the bike, than these might make a bit of sense. But the issue of pedaling with a block will become a problem in short order if you pedal with your foot angled down.
IMO - Those tall enough to want these would be much better served with a higher BB, than this nonsense. Another alternative would be to use a Phil Centric BB mounted in the top position to raise the center of rotation without any drawbacks except the dough spent.
IMO - Those tall enough to want these would be much better served with a higher BB, than this nonsense. Another alternative would be to use a Phil Centric BB mounted in the top position to raise the center of rotation without any drawbacks except the dough spent.
not surprisingly, the inventor is also apparently the guy who fit Marco Pantini. I am guessing he is the reason 5'8" Marco was seen on 180mm record crank arms. I agree that a taller bottom bracket and lower Q factor is a better solution.
the only application I could see these making sense (in a shorter version) is on a mini velo that you want to keep low for easy saddle mounting and quick handling. A touring bike may also be an application (low bb is more stable)
Last edited by thirdgenbird; 09-07-13 at 12:06 PM.
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There's no benefit in terms of saddle height, since that's based on ass-to-pedal distance, not ass-to-BB distance, so the saddle would need to be raised by the thickness of the blocks. As for touring, lower BB's are only more stable if the entire center of gravity is lower, and since the saddle has to be raised, you're back where you started. Cornering clearance also barely matters, since tourists have no reason not to coast through hard turns, and most do because they find that the straight other, helps to stabilize the bike by forming a saddle to crank brace keeping the frame and body together.
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I agree that whether it'd make sense in terms of efficiency or not would remain to be seen, but the biomechanics might have something going for it. You'd get a longer crank where it'll be most useful, while "only" needing the knee bend of a significantly shorter crank. It's bound to be beneficial for one medical condition or the other.
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There is no application, except for fudging a long crank (for those who want it) onto a bike while keeping the cornering angle the same.
There's no benefit in terms of saddle height, since that's based on ass-to-pedal distance, not ass-to-BB distance, so the saddle would need to be raised by the thickness of the blocks. As for touring, lower BB's are only more stable if the entire center of gravity is lower, and since the saddle has to be raised, you're back where you started. Cornering clearance also barely matters, since tourists have no reason not to coast through hard turns, and most do because they find that the straight other, helps to stabilize the bike by forming a saddle to crank brace keeping the frame and body together.
There's no benefit in terms of saddle height, since that's based on ass-to-pedal distance, not ass-to-BB distance, so the saddle would need to be raised by the thickness of the blocks. As for touring, lower BB's are only more stable if the entire center of gravity is lower, and since the saddle has to be raised, you're back where you started. Cornering clearance also barely matters, since tourists have no reason not to coast through hard turns, and most do because they find that the straight other, helps to stabilize the bike by forming a saddle to crank brace keeping the frame and body together.
Your comments about touring bikes and corning clearance are true though. I still see a mini velo as a potential use, but it is still unnessisary complexity for potentially unused cornering clearance. What little is gained may also be removed by one pedal choice that appears to hang at a bad angle for city use.
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I agree that whether it'd make sense in terms of efficiency or not would remain to be seen, but the biomechanics might have something going for it. You'd get a longer crank where it'll be most useful, while "only" needing the knee bend of a significantly shorter crank. It's bound to be beneficial for one medical condition or the other.
The only ways to shrink the pedal circle and recuce the arc of flex at the knee is with a shorter crank, or by ankling, dropping the heel at the top, and extending the toes at the bottom.
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Ou are missing their conversion chart. They recommend using a longer crankset but the block effectively shortens it at the bottom. The whole crank circle doesn't move up. The bottom (where saddle height is measured) stays the same. The rest moves "up an forward" on the bike. Their goal is to use a longer crankset while maintaining the distance from saddle to pedal platform at the bottom of the stroke.
Last edited by thirdgenbird; 09-07-13 at 01:34 PM.
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Ou are missing their conversion chart. They recommend using a longer crankset but the block effectively shortens it at the bottom. The whole crank circle doesn't move up. The bottom (where saddle height is measured) stays the same. The rest moves "up an forward" on the bike. Their goal is to use a longer crankset while maintaining the distance from saddle to pedal platform at the bottom of the stroke.
IMO, the folks are using a bit of sleight of hand to make theory look better. They have the circle of a 190mm Zen and that of a 175mm standard crank spinning on the same center super imposed. This correctly shows the ground clearance benefit realized, but can camouflage what the deice actually does. If you plot the foot circles of the 190mm Zen next to a plain 190mm crank, you get two nearly identical circles one higher than the other by 15mm (or whatever the block height is. There is no difference in circle diameters, just a vertical offset.
To get the benefit Dabac was referencing you'd need a system whereby the pedal were above the bearing at the bottom and below at the top, so the foot travelled a flattened oval. That would require more machinery, and where I originally thought these guys were headed, but aren't
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Depends on what foot angle you're counting on. As an extreme, imagine a ballerina turned cyclist, doing the downstroke on pointe. In that scenario basically the whole block height would create a virtual crank extension for that part of the circle. Variable leverage the easy way. And a good way to create schematics for marketing by turning a circle into all kinds of interesting cam shapes by assuming different foot angles for different sections of the stroke.
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IMO, the folks are using a bit of sleight of hand to make theory look better. They have the circle of a 190mm Zen and that of a 175mm standard crank spinning on the same center super imposed. This correctly shows the ground clearance benefit realized, but can camouflage what the deice actually does. If you plot the foot circles of the 190mm Zen next to a plain 190mm crank, you get two nearly identical circles one higher than the other by 15mm (or whatever the block height is. There is no difference in circle diameters, just a vertical offset.
foot angle will slightly change the shape of the circle, but I don't believe there would be any performance gain from it.
To get the benefit Dabac was referencing you'd need a system whereby the pedal were above the bearing at the bottom and below at the top, so the foot travelled a flattened oval. That would require more machinery, and where I originally thought these guys were headed, but aren't
Last edited by thirdgenbird; 09-07-13 at 02:13 PM.
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This isn't very much, and unless one has very short feet, pales in comparison to the effects that ankling would provide on a simple crank.
I know that I can be very thick, and invite anyone less skeptical than myself to give these a shot f they think they make sense. OTOH having grown up in the city before there were the "scoop the poop" laws, I've gotten pretty adept at recognizing sh*t before I step in it.
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#41
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Depends on what foot angle you're counting on. As an extreme, imagine a ballerina turned cyclist, doing the downstroke on pointe. In that scenario basically the whole block height would create a virtual crank extension for that part of the circle. Variable leverage the easy way. And a good way to create schematics for marketing by turning a circle into all kinds of interesting cam shapes by assuming different foot angles for different sections of the stroke.
This torquing effect at the pedal platform is something we all feel every day, as the back of the pedal digs into our feet while the front doesn't. It's the reason that we've had 100 years of effort to get the the foot closer to or below the pedal's center of rotation.
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Hi,
I think you are missing something, and that is if you assume the the foot circle is moved
up but still the same, the centre of the torque, the crank, does not move, so the two
cases are not the same. Analysis by extreme is useful, consider say 50mm lift, and
the relative torque through the crank at 1 o'clock and 5 o'clock for the two cases.
rgds, sreten.
Assume for vector analysis the angle between the extension and the crank resolves
to a straight crank directly connected to the pedal spindle, look at that length.
I think you are missing something, and that is if you assume the the foot circle is moved
up but still the same, the centre of the torque, the crank, does not move, so the two
cases are not the same. Analysis by extreme is useful, consider say 50mm lift, and
the relative torque through the crank at 1 o'clock and 5 o'clock for the two cases.
rgds, sreten.
Assume for vector analysis the angle between the extension and the crank resolves
to a straight crank directly connected to the pedal spindle, look at that length.
Last edited by sreten; 09-07-13 at 07:02 PM.
#44
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I've no dog in the fight, and everyone is free to draw their own conclusions. As far as I'm concerned, I've made all my points and am happy to let it rest.
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#46
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If you read my prior posts and dialogs with others, you'll see that I've already given this more thought than it's probably worth.
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#49
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Used 40 years ago when exhaust pipes ran to the side of the "then new" wide 4 cyl engines. A hard right turn and your outside tube hit pavement. Thump and you did a quick boot scoot to the left.
Hang off the saddle, hold the bike upright..............lower center of gravity and you're around the corner in style. Wearing leathers, a shot of WD-40 on the butt made things easier.
Header manufactures learned to route the tubes under the center of the motor. Then tires got better. Anymore, hangin' off is about the same as skid stops on a fixie. Looks good for the squrls (I think they call gals these days). And, please don't use the passenger pegs to get the "rear-set, Ricky Racer" look.
Off topic.
I like products to stand the test of time before I invest in them. One of my latest purchases was a pair of 105 crankarms with a JIS taper. They worked then, they work now. I don't have the power to know any better and my bike goes forward.