Wheel Build
- mikesbytes
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Postby mikesbytes » Tue Nov 27, 2007 1:50 pm
- sogood
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Postby sogood » Tue Nov 27, 2007 2:01 pm
Well, the question is how much, hence the doubt. 0.2% is probably something a rider can make up if the situation calls for it. But what if it's 1%? Does that become very significant in a chase situation? Does a fraction of a second missed in the acceleration make a difference to one's ability to catch a wheel? At 30km/h, a second missed equates to 8m in separation. A loss of 1/8th of second equals to a meter of separation. How much more energy would one need to close that meter gap in a hurry? These are my questions.artemidorus wrote:Noone said that 0.2% wasn't significant at an elite level, or even if you're sprinting uphill against your mate. It's not only going to increase the steady state workload uphill, but it is going to increase the wattage required for a given acceleration, slightly. Nothing to doubt.
To the extent that many well versed forum participants pushing the line that weight makes ignorable difference while basing their arguments primarily on static state calculations. I think there's some more to the story.
I wonder if a decent power meter has the necessary resolution to differentiate?
RK wrote:And that is Wikipedia - I can write my own definition.
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Postby artemidorus » Tue Nov 27, 2007 2:12 pm
You're not happy with a=F/m? Increase m by 0.2% and F has to increase by 0.2% to maintain a. (I'm still happy to ignore rotational inertia as being 2 or more orders of magnitude less important).sogood wrote:Well, the question is how much, hence the doubt. 0.2% is probably something a rider can make up if the situation calls for it. But what if it's 1%? Does that become very significant in a chase situation? Does a fraction of a second missed in the acceleration make a difference to one's ability to catch a wheel? At 30km/h, a second missed equates to 8m in separation. A loss of 1/8th of second equals to a meter of separation. How much more energy would one need to close that meter gap in a hurry? These are my questions.artemidorus wrote:Noone said that 0.2% wasn't significant at an elite level, or even if you're sprinting uphill against your mate. It's not only going to increase the steady state workload uphill, but it is going to increase the wattage required for a given acceleration, slightly. Nothing to doubt.
To the extent that many well versed forum participants pushing the line that weight makes ignorable difference while basing their arguments primarily on static state calculations. I think there's some more to the story.
I wonder if a decent power meter has the necessary resolution to differentiate?
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Postby artemidorus » Tue Nov 27, 2007 2:15 pm
I really doubt it. You'd need two, cross-calibrated to measure less than a watt's difference beyond the predictable 0.2% difference.sogood wrote:I wonder if a decent power meter has the necessary resolution to differentiate?
- mikesbytes
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Postby mikesbytes » Tue Nov 27, 2007 2:30 pm
Poorer aerodynamics, things hang out more as you get oldersogood wrote:Where should we stick that age variable in the equation? I am sure it'll significantly affect the calculation.
- toolonglegs
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Postby toolonglegs » Tue Nov 27, 2007 2:42 pm
Poorer aerodynamics but a more devious cunning mindmikesbytes wrote:Poorer aerodynamics, things hang out more as you get oldersogood wrote:Where should we stick that age variable in the equation? I am sure it'll significantly affect the calculation.
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Postby sogood » Tue Nov 27, 2007 3:07 pm
If you read my earlier posts, I was referring to total bike weight rather than dwelling on the much smaller impact of inertial issue.artemidorus wrote:You're not happy with a=F/m? Increase m by 0.2% and F has to increase by 0.2% to maintain a. (I'm still happy to ignore rotational inertia as being 2 or more orders of magnitude less important).
F=ma is without doubt real. But the question is how much does 0.2%, or 0.2+x% (where x could be a multiple of 0.2) in an uphill acceleration, make to one's ability to catch a passing attacker?
RK wrote:And that is Wikipedia - I can write my own definition.
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Postby sogood » Tue Nov 27, 2007 3:11 pm
Not sure of the need to have two PMs. With two and calibration, it's still likely to have greater variance than measuring it using a single unit. Given the best power meter has an error band of 3%, the difference may truly be hiding in the noise. Yet again, could the x in the (0.2+x)% be equal or greater than 3?artemidorus wrote:I really doubt it. You'd need two, cross-calibrated to measure less than a watt's difference beyond the predictable 0.2% difference.
RK wrote:And that is Wikipedia - I can write my own definition.
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- Bnej
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Postby Bnej » Tue Nov 27, 2007 3:21 pm
All I know is every time I lose someone on a hill, it's because they have a lighter, more expensive bike. That's my story and I'm sticking to it!sogood wrote:F=ma is without doubt real. But the question is how much does 0.2%, or 0.2+x% (where x could be a multiple of 0.2) in an uphill acceleration, make to one's ability to catch a passing attacker?
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Postby sogood » Tue Nov 27, 2007 3:31 pm
You have to be truly objective about all these. The real reason was because that Record and DA had a superior and faster shift action and that's where you really lost time!Bnej wrote:All I know is every time I lose someone on a hill, it's because they have a lighter, more expensive bike. That's my story and I'm sticking to it!
RK wrote:And that is Wikipedia - I can write my own definition.
- toolonglegs
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Postby toolonglegs » Tue Nov 27, 2007 4:12 pm
The only time i lose time to anyone on a hill is when my hand slips off the tow carsogood wrote:You have to be truly objective about all these. The real reason was because that Record and DA had a superior and faster shift action and that's where you really lost time!Bnej wrote:All I know is every time I lose someone on a hill, it's because they have a lighter, more expensive bike. That's my story and I'm sticking to it!
- sogood
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Postby sogood » Tue Nov 27, 2007 4:17 pm
Serve you right for picking up those non-grippy and non-aero gloves off the back of that tow car.toolonglegs wrote:The only time i lose time to anyone on a hill is when my hand slips off the tow car
RK wrote:And that is Wikipedia - I can write my own definition.
- toolonglegs
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Postby toolonglegs » Tue Nov 27, 2007 4:25 pm
Did I say tow car!...i meant chair liftsogood wrote:Serve you right for picking up those non-grippy and non-aero gloves off the back of that tow car.toolonglegs wrote:The only time i lose time to anyone on a hill is when my hand slips off the tow car
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Postby MichaelB » Tue Nov 27, 2007 5:30 pm
Yeah, but gravity works with you downhill.Bnej wrote:All I know is every time I lose someone on a hill, it's because they have a lighter, more expensive bike. That's my story and I'm sticking to it!sogood wrote:F=ma is without doubt real. But the question is how much does 0.2%, or 0.2+x% (where x could be a multiple of 0.2) in an uphill acceleration, make to one's ability to catch a passing attacker?
I have passed my mate many a time downhill. About the only place though
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Postby Bnej » Tue Nov 27, 2007 6:47 pm
People on dual suspension bikes always leave me for dead on any rough downhill.MichaelB wrote:Yeah, but gravity works with you downhill.
I have passed my mate many a time downhill. About the only place though
When I was coming back from Jenolan with two others ages ago, they both had dual suspension MTBs (Anthem 0 and Top Fuel) and I was on my road bike, and this long downhill on caves road they got waaay ahead of me. I had to keep my speed down to save my wrists & body from the pitted and cracked road surface, while they did it at speed in plush suspended comfort.
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Postby mikesbytes » Tue Nov 27, 2007 6:52 pm
Yeh, but once you reach the bottom your bike is the better option.Bnej wrote:People on dual suspension bikes always leave me for dead on any rough downhill.MichaelB wrote:Yeah, but gravity works with you downhill.
I have passed my mate many a time downhill. About the only place though
When I was coming back from Jenolan with two others ages ago, they both had dual suspension MTBs (Anthem 0 and Top Fuel) and I was on my road bike, and this long downhill on caves road they got waaay ahead of me. I had to keep my speed down to save my wrists & body from the pitted and cracked road surface, while they did it at speed in plush suspended comfort.
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Postby sogood » Tue Nov 27, 2007 7:25 pm
RK wrote:And that is Wikipedia - I can write my own definition.
- mikesbytes
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Postby mikesbytes » Tue Nov 27, 2007 8:25 pm
I'm peddling downhill. Years of experience and a motorcycling background make me a bit braver.sogood wrote:I have similar experiences where the heavier riders would gradually move ahead of me on those down-hills during our RNP rides. The annoying part was that I couldn't make up by peddling at those speeds. Most frustrating. Just had to do the catch ups on the up-hill... Painful!
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Postby toolonglegs » Tue Nov 27, 2007 8:54 pm
went riding with my mate bubbles on the way to and from eastern creek on sunday...he is about 8 kilos heavier than me and it was the first time i have had to pedal downhill to keep up with some onemikesbytes wrote:I'm peddling downhill. Years of experience and a motorcycling background make me a bit braver.sogood wrote:I have similar experiences where the heavier riders would gradually move ahead of me on those down-hills during our RNP rides. The annoying part was that I couldn't make up by peddling at those speeds. Most frustrating. Just had to do the catch ups on the up-hill... Painful!
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Postby Bnej » Tue Nov 27, 2007 9:31 pm
Tried using a really flat aero tuck to go faster? Of course they can counter by doing the same thing. You could try a ski tuck where you sit on the top tube.sogood wrote:I have similar experiences where the heavier riders would gradually move ahead of me on those down-hills during our RNP rides.
Downhills is all mass & power vs drag, uphill is all power vs weight. Unless it's off-road in which case downhill is all confidence vs terror.
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Postby artemidorus » Tue Nov 27, 2007 9:34 pm
Sorry, I'm really not sure where your mysterious x is coming from. Do you mean that the rims weigh more than 100g above the competition? I'm not sure that we're getting anywhere.sogood wrote:Not sure of the need to have two PMs. With two and calibration, it's still likely to have greater variance than measuring it using a single unit. Given the best power meter has an error band of 3%, the difference may truly be hiding in the noise. Yet again, could the x in the (0.2+x)% be equal or greater than 3?artemidorus wrote:I really doubt it. You'd need two, cross-calibrated to measure less than a watt's difference beyond the predictable 0.2% difference.
You couldn't use a single PM as you need to have two bicycles accelerating at exactly the same rate, side by side.
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Postby sogood » Tue Nov 27, 2007 9:50 pm
They are in as much a conventional tuck as I was in. As for superman position, well, I'll endure the up-hill catch ups than becoming a statistic.Bnej wrote:Tried using a really flat aero tuck to go faster? Of course they can counter by doing the same thing. You could try a ski tuck where you sit on the top tube.
Downhills is all mass & power vs drag, uphill is all power vs weight. Unless it's off-road in which case downhill is all confidence vs terror.
With some of the roads in RNP, down-hill is also confidence vs terror.
RK wrote:And that is Wikipedia - I can write my own definition.
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Postby toolonglegs » Tue Nov 27, 2007 9:55 pm
You can always tell me in the bunch,I am the one sitting straight up trying to catch as much wind as possible so i dont have to hit the brakes ...will miss all that soonsogood wrote:They are in as much a conventional tuck as I was in. As for superman position, well, I'll endure the up-hill catch ups than becoming a statistic.Bnej wrote:Tried using a really flat aero tuck to go faster? Of course they can counter by doing the same thing. You could try a ski tuck where you sit on the top tube.
Downhills is all mass & power vs drag, uphill is all power vs weight. Unless it's off-road in which case downhill is all confidence vs terror.
With some of the roads in RNP, down-hill is also confidence vs terror.
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Postby sogood » Tue Nov 27, 2007 9:59 pm
Sorry if I didn't make it clear. The x refers to the additional efforts required for an acceleration to catch another rider. So with 0.2% being the effective difference caused by the weight difference under steady state (constant velocity) while it acted against a constant deceleration force (gravity). With an additional acceleration, the total difference would be 0.2 plus another amount attributable to the effort required for the additional acceleration (to catch the attacking rider).artemidorus wrote:Sorry, I'm really not sure where your mysterious x is coming from. Do you mean that the rims weigh more than 100g above the competition? I'm not sure that we're getting anywhere.
You couldn't use a single PM as you need to have two bicycles accelerating at exactly the same rate, side by side.
The reason you don't need two PMs is that this really is an intrinsic test, one that determines at what level of weight difference would there be a significant change in the ability of the same rider in latching on.
RK wrote:And that is Wikipedia - I can write my own definition.
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