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#281
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On 2004-09-06 17:51:47 -0700, "Trevor" said:
wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? |
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#282
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On 2004-09-06 17:51:47 -0700, "Trevor" said:
wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? |
#283
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On 2004-09-06 17:51:47 -0700, "Trevor" said:
wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? |
#284
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On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd
wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel |
#285
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On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd
wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel |
#286
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On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd
wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel |
#287
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wrote in message ... On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel So what's your point Carl? That Trevor is a liar? Or you enjoy playing Perry Mason to this group? I think some people really need to get a life here. Makes me wonder when they have time to actually ride. If he says he gone 70 mph then so what? He could say he's gone 100 mph and I wouldn't even bat an eyelash. -tom |
#288
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wrote in message ... On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel So what's your point Carl? That Trevor is a liar? Or you enjoy playing Perry Mason to this group? I think some people really need to get a life here. Makes me wonder when they have time to actually ride. If he says he gone 70 mph then so what? He could say he's gone 100 mph and I wouldn't even bat an eyelash. -tom |
#289
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wrote in message ... On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel So what's your point Carl? That Trevor is a liar? Or you enjoy playing Perry Mason to this group? I think some people really need to get a life here. Makes me wonder when they have time to actually ride. If he says he gone 70 mph then so what? He could say he's gone 100 mph and I wouldn't even bat an eyelash. -tom |
#290
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On Tue, 7 Sep 2004 13:00:15 -0700, "Tom Nakashima"
wrote: wrote in message .. . On Tue, 7 Sep 2004 10:30:38 -0700, Bill Lloyd wrote: On 2004-09-06 17:51:47 -0700, "Trevor" said: wrote in message ... It gets worse at higher speeds. Here's a table for the same bike on a 17% grade, where it reaches 70.1 mph and needs 204 rpm to engage a 2124 mm 700c tire with 54 x 12 gearing: mph rpm watts 70.1 0 0 coasting, not pedalling 62.6 204 0.1 coasting, but pedalling w/no power 70.1 204 1046 pedalling 52 x 12 gear I think it was E. Merckx whose measured o/p was 1 1/3 hp or 1700Watts which is 650 watts more than that required for 70mph. High power is produced at high rpm so a slower cadence is not required. Merckx might have maxed at 1700 watts (actually, I doubt it), but that's something he could maintain for 5 seconds. So there's no way he'd be doing that on a descent. Also, 204 RPM is ridiculous... nobody is going to sustain that sort of cadence for more than a few seconds. Certainly you won't be making good power at that RPM (of course, these days you'd use a 53x11 instead of a 52x12, that's silly gearing if you're going down a big downhill fast, welcome to the 90's). Not all riders are alike, at what speed would 1700watts attain on a 1in10 grade with this calculator. Use 53x12 700x25C 167.5 cranks, flat back. Not physically possible, even for Merckx. Because, recall, to go that 70.1 mph you have to do the work of accelerating from 60 mph to 70 mph by pedaling. And a 17% grade? Where are you going to find a sustained 17% grade? Dear Bill, The closest thing to a sustained 17% grade in Wales appears to be Bwlch-y-Groes (not the Bwlch Trevor mentioned): http://www.salite.ch/groes1.htm There's 2 km of 16% grade at the top. It's much steeper than any of the 53 other grades in Wales listed at: http://ciclismo.sitiasp.it/motore.as...ngua=eng&da=az Unfortunately, the site just shows a distance versus altitude graph, so there's no easy way to tell if turns make high speed descents impossible.. Trevor, of course, claims to have hit 70 mph on what he judges to be only a 10% grade, not the 17% that I used for my example. (Wales is awfully short of 10% grades, judging by the site above, which doesn't mention the A494 road as having outstandingly steep sections.) Trevor eventually remembered a tailwind of less than 10 mph that was later upgraded to 15 mph. He also proposes some drafting theories that don't seem to be exactly air-tight, if you'll pardon the pun. Riders can reach 70 mph just by coasting, given some combination of grade, weight, and tailwind. But Trevor claims to have reached 70 mph routinely by pedalling a 52 x 12 at 200 rpm on a stretch of Welsh road whose grade he claims is about 10%. I'm skeptical, but I think that his 70 mph claim may be a little more likely than his claim that a sprinting rider was swerving ten feet from side to side when the gearing produced only 12.5 feet of forward movement with each stomp on the pedal. Or than his claim that any decent sprinter can reach 50 mph on level ground (Mark McMaster pointed out that the flying 200 meter sprint record is just under ten seconds--only 45.4 mph.) Or than his claim that both his tires routinely came off the ground at the same time during sprinting in a sort of kangaroo-hop tribute to his wheel-building technique, power, and poor form. Or than his claim that he has a wheel with spokes worn a third of the way through where they cross. Or . . . well, you get the idea. Carl Fogel So what's your point Carl? That Trevor is a liar? Or you enjoy playing Perry Mason to this group? I think some people really need to get a life here. Makes me wonder when they have time to actually ride. If he says he gone 70 mph then so what? He could say he's gone 100 mph and I wouldn't even bat an eyelash. -tom Dear Tom, My point is that although 70 mph is quite possible, given the right combination of grade, weight, tailwind, and possibly amazing pedalling, an awful lot of claims look implausible when we ask for details. Asking for details and pondering the replies is how I learn more about this sort of thing. Until I pursued the question, I would have dismissed any claim by Chalo Colina that hecan easily hit much higher speeds downhill than the rest of us. But now I know that a bicycle and rider weighing 400 pounds really can roll down a modest hill at ungodly speeds. I also have a theory that the Fury RoadMaster rolls down my daily hill roughly as fast as my touring bike, despite the handicap of its huge, soggy tires because of its extra mass. And I've learned why the damn bike always slows down a little when I start pedalling on the runout from a good hill, no matter how hard I try to stay tucked in--pedal motion increases wind drag. In short, I want to know why I bat an eyelash and whether I should be raising my eyebrows. When I first saw Jobst's absurd claim that bicycles stand on their lower spokes, my eyebrows turned into a handsome toupee. But after I pondered things and read what other people said, my eyebrows descended enough for me to scratch my bald head and eventually admit that Jobst seems to be right. Right now, I have one eyebrow lifted about spoke-squeezing stress-relief claims. Some days, it lowers a little, but on other days it's joined by the other eyebrow. Right or wrong, the theory does come from someone with a history of being right about a lot of bicycling physics. Whether Trevor is Baron Munchausen on a bicycle or the victim of unjustified doubts, it's still interesting to look into his claims. (The real baron wasn't what the book made him out to be: http://www.fact-index.com/b/ba/baron_munchhausen.html See how interesting a little poking around can be?) IfTrevor has a picture of the wheel with the spokes worn a third of the way through, then that will be damned interesting. Wouldn't you click on a link to a picture of something like that? Or a picture of a sprinter with both tires coming off the ground? Or a diagram of how a sprinter can swerve ten feet sideways as he stomps down on a pedal? Or a link to a site that explains how to reach 50 mph on a level course? Or a post from some of Trevor's fellow riders testifying to their amazing speeds ten years ago in the Welsh countryside? Unfortunately, a Welsh corgi seems to be thriving on a diet of Trevor's homework. In the latest example, the wheel with the badly worn spokes can't be found--which gives Trevor the opportunity to tell us that this missing wheel with the worn spokes is also the wheel that proved that Jobst is utterly wrong. Possibly the wheel is lying under a piece of the true cross? Or maybe there really is such a wheel and within a month we'll have some fascinating pictures of what look like badly worn spokes. ( I'm wondering whether the galvanized spokes that Trevor favors might corrode at the crossing and then erode, something that the stainless-steel-spoke-folk of rec.bicycles.tech wouldn't be likely to encounter.) But so far I can't see the cannonball that Trevor rode to the moon on the A494. Or how he pulled himself past those riders at 70 mph by his bootstraps. (Read the link above.) But I do expect that he'll surprise me and that I'll have fun looking into his future claims. He does seem to have done a good deal of bicycling, so he might well have some fascinating points that turn out to be true. Carl Fogel |
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