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actionbent part2
Peter Clinch wrote: Oh dear. I'd regard him with quite a bit of suspicion, to be honest! ;-/ When testing 'bents at Ligfietswinkel in Amsterdam the owner cut and remade chains as needed for customers to try bikes. He had it down to about 20 seconds. Now, practice makes perfect, and /I/ certainly couldn't do it that fast, but 20 minutes to shorten a chain? There just isn't any excuse. I do (regard the mechanic hesitantly), because he seemed to be the kind of backyard mechanic my friends are -- "good enough for government" quality work: I told him there was a gold-colored link in the chain, but he just undid it somewhere arbitrarily, and while joining the chain again he didn't use the chain tool at first, but a regular whachamacallit, that hand-held "vice" with the scissor-like construction...while shortening the boom he used a rubber mallet but still no cloth over the bike until at my suggestion...little things like this. But, to be fair, a good quarter of the time he was struggling to get the chain back through the teflon tubing since the whole line slipped off. =) And he hadn't worked on recumbents before, so perhaps the novelty of it all, even though a chain is a chain is a chain, had him a bit distracted. If the chain itself is running smoothly with no stiff links this is likely to be derailleur adjustment, I'd guess. What's a "stiff" link? I'd never had a chain follow the chain ring back up, ever! But again I gasp in horror... 20 minutes to shorten a chain!? :-0 Yeah, and I'm really not exaggerating. But I am referring to the whole process involved, from undoing to redoing, and at least 25% of the time was spent trying to "thread" the chain back through the teflon tubes and underneath the idler (that big flywheel, right?). Nothing compared to 20 seconds, for sure, but certainly far better than I would've been able to do, not having heard of chain tools until just yesterday! And now, having seen it once, I at least have the framework against which to gauge my own attempts. Yep, I always knew a 'bent was gonna mean hands-on...just didn't expect it quite so soon! What's the fastest you can run yours on the flats? At the middle gears (front and back), I seem able only to acheive 16-17 mph! This is what I do leisurely cruising along on my DF!!! I do have on them Schwalbe Marathon Plus tires, though.... Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
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actionbent part2
NYC XYZ wrote:
SNIP and while joining the chain again he didn't use the chain tool at first, but a regular whachamacallit, that hand-held "vice" with the scissor-like construction... AKA "pliers." (How embarrassing!) |
#3
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actionbent part2
On 23 Apr 2006 03:16:33 -0700, "NYC XYZ"
wrote: [snip] I'd never had a chain follow the chain ring back up, ever! But again I gasp in horror... 20 minutes to shorten a chain!? :-0 Yeah, and I'm really not exaggerating. But I am referring to the whole process involved, from undoing to redoing, and at least 25% of the time was spent trying to "thread" the chain back through the teflon tubes and underneath the idler (that big flywheel, right?). [snip] Dear N, It seems counter-intuitive, but one of the reasons for that idler pulley and those long teflon tubes is that without them, the chain is likely to "follow the chain ring back up" on the unusually long chain runs of recumbents. See this industrial chain troubleshooting list, which includes several other causes and remedies for what we call chain suck: Symptoms: The chain winds onto the sprocket (poor separation from the sprocket teeth.) Possible Causes: Span between axles is too large. Remedy: Install an idler. http://chain-guide.com/basics/7-1-6-...eshooting.html Cheers, Carl Fogel |
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actionbent part2
NYC XYZ wrote:
I do (regard the mechanic hesitantly) snip So why say he seems cool and you'll be back? Doesn't seem to scan... What's a "stiff" link? Just what it says: links should move completely freely, but a stiff chain link has marked reluctance in pivoting relative to its neighbour. Yeah, and I'm really not exaggerating. But I am referring to the whole process involved, from undoing to redoing, and at least 25% of the time was spent trying to "thread" the chain back through the teflon tubes and underneath the idler (that big flywheel, right?). So we're still at 15 minutes to break a chain in a couple of places and pop it back together, which is still not very good. What's the fastest you can run yours on the flats? No idea, I don't have a speedo and I'm not really that interested. At the middle gears (front and back), I seem able only to acheive 16-17 mph! This is what I do leisurely cruising along on my DF!!! If you want to go faster, that's what the Speedmachine is for... I do have on them Schwalbe Marathon Plus tires, though.... Shouldn't be /that/ much slower than the plain Marathons I use. Make sure they're running at 100 psi. Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
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actionbent part2
Peter Clinch wrote: So why say he seems cool and you'll be back? Doesn't seem to scan... He still knows more than me! And when I say "cool," I mean that I can ask why he's doing something, and suggest some other way of doing things, and he ain't offended...very easy-going personality. I can ask questions, learn, and he didn't seem to mind. Of course, I keep it respectful, too. I don't bother him with constant questions. But I just get the sense I'm not dealing with a frustrated amateur racer, know what I mean? Who'd rather be doing the Tour de France and instead has to humor a dummy who has no mechanical inclinations at all.... Just what it says: links should move completely freely, but a stiff chain link has marked reluctance in pivoting relative to its neighbour. Yes, I've since found a picture that "explains" it perfectly. So we're still at 15 minutes to break a chain in a couple of places and pop it back together, which is still not very good. No, I guess not...I didn't know how long it was supposed to take. But surely you exaggerate with your claim of 20 seconds! Fixing a flat is like five minutes, and surely cutting a chain (and then making sure it's working right thereafter) is at least five minutes, too? No idea, I don't have a speedo and I'm not really that interested. I just hope I'm not more than 3 mph behind my DF on the flats -- bad as that is (a mile is like 20 NYC blocks...3 mph less would make me a whole neigbhorhood or two behind after an hour!). If you want to go faster, that's what the Speedmachine is for... I seriously doubt the SpeedMachine is that much faster...it's certainly the same damned weight! Yes it's even more reclined, but no big deal. I can't wait for HP Velotechnik's new machines...I'm guessing it'll be another year or two.... Shouldn't be /that/ much slower than the plain Marathons I use. Make sure they're running at 100 psi. Oddly enough, the tires say that maximum psi is 70-lbs.!!! Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
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actionbent part2
NYC XYZ wrote:
No, I guess not...I didn't know how long it was supposed to take. But surely you exaggerate with your claim of 20 seconds! I wasn't timing him, but I think that's a fair guesstimate. What you have to do is wind in a lever 3 times (once for each end of the break, once to reconnect the two ends. Fixing a flat is like five minutes, and surely cutting a chain (and then making sure it's working right thereafter) is at least five minutes, too? Fixing a flat generally means removing the wheel, unseating the tyre, removing the inner tube, putting in a new one, reseating the tyre, replacing the wheel, reinflating the tyre. That's a much bigger to-do list than doing up lever to remove one pin, removing another, popping one pin back in. If you want to go faster, that's what the Speedmachine is for... I seriously doubt the SpeedMachine is that much faster...it's certainly the same damned weight! Yes it's even more reclined, but no big deal. No, very big deal indeed. At 18 mph about 80% of your power is overcoming air resistance, and there's significantly less frontal area to catch the wind on a Speedmachine. There's a clue in the name! Oddly enough, the tires say that maximum psi is 70-lbs.!!! I'd assumed, incorrectly as it turned out, that the M+ would be the same dimensions as the plain Marathon, but looking at the specs they are fatter and run at lower pressures. So they will probably be slowing you down :-( For a still reasonably puncture proof and capable touring tyre a swicth from the 1.75" M+ to the 1.5" Marathon running at higher pressure will probably help you with rolling resistance and hence speed you up. Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
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actionbent part2
Peter Clinch wrote:
I wasn't timing him, but I think that's a fair guesstimate. What you have to do is wind in a lever 3 times (once for each end of the break, once to reconnect the two ends. Fixing a flat generally means removing the wheel, unseating the tyre, removing the inner tube, putting in a new one, reseating the tyre, replacing the wheel, reinflating the tyre. That's a much bigger to-do list than doing up lever to remove one pin, removing another, popping one pin back in. But you've got to check the gears, too, afterwards, to make sure they're shifting right and all. I don't think they did too much of this, though...he probably checked for half a minute! No, very big deal indeed. At 18 mph about 80% of your power is overcoming air resistance, and there's significantly less frontal area to catch the wind on a Speedmachine. There's a clue in the name! Now now, we all know about names and marketing...but I didn't know 80% of effort expended in on behalf of air resistance! Still, my point is that I should be at least as good as a DF, given my better aerodynamics on the SMGTe, but that's not been the case so far...even given my Schwalbe Marathon Plus tires, the hit seems too big...I can only hope it's a matter of developing the muscles and riding technique, as well as those nagging chain issues (chain hop, chain suck, stiff shifting, no shifting...it's rideable, but not smoothly so, especially for a new machine with brand new components). I'd assumed, incorrectly as it turned out, that the M+ would be the same dimensions as the plain Marathon, but looking at the specs they are fatter and run at lower pressures. So they will probably be slowing you down :-( For a still reasonably puncture proof and capable touring tyre a swicth from the 1.75" M+ to the 1.5" Marathon running at higher pressure will probably help you with rolling resistance and hence speed you up. Yes, I knew this going in, but I figured that I'd rather have more puncture-proof or puncture-resistance than speed, if the penalty isn't too large and way out of proportion. Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
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actionbent part2
NYC XYZ wrote:
But you've got to check the gears, too, afterwards, to make sure they're shifting right and all. I don't think they did too much of this, though...he probably checked for half a minute! This is fair comment, but 30 seconds should be enough in the first instance, which still leaves us rather a lot of time. Tweaking the gears is easy enough with the adjuster screw where the gear cable goes into the rear mech, just needs the odd tweak to tune the shifting. Now now, we all know about names and marketing...but I didn't know 80% of effort expended in on behalf of air resistance! That is, IIRC, the approximate figure on a DF, though I can't remember if that's on the hoods, in a heavy tuck or what. But it does show approximately the degree to which speed is dominated by aerodynamics any time you get any sort of fast. Still, my point is that I should be at least as good as a DF, given my better aerodynamics on the SMGT They're not /that/ much better. I have my seat reclined as far as possible and it's pretty clear that cycling with pals on DF leaned over the drops that the frontal area catching the wind isn't all that different. When they go into a full speed crouch it's quite obvious they have less frontal area than me. If you want better aero, that's what the Speedmachine is for (and to some extent, the Grasshopper). Yes, I knew this going in, but I figured that I'd rather have more puncture-proof or puncture-resistance than speed, if the penalty isn't too large and way out of proportion. To put the dangers into perspective, I've had 2 punctures on mine in 5 years running standard Marathons. They give very good puncture resistance. The M+ is only really an issue if you're in Puncture Hell, otherwise they'd be standard issue rather than the plain Marathon. Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
#9
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actionbent part2
Peter Clinch wrote: NYC XYZ wrote: [snip] Now now, we all know about names and marketing...but I didn't know 80% of effort expended in on behalf of air resistance! That is, IIRC, the approximate figure on a DF, though I can't remember if that's on the hoods, in a heavy tuck or what. But it does show approximately the degree to which speed is dominated by aerodynamics any time you get any sort of fast. Still, my point is that I should be at least as good as a DF, given my better aerodynamics on the SMGT They're not /that/ much better. I have my seat reclined as far as possible and it's pretty clear that cycling with pals on DF leaned over the drops that the frontal area catching the wind isn't all that different. When they go into a full speed crouch it's quite obvious they have less frontal area than me. If you want better aero, that's what the Speedmachine is for (and to some extent, the Grasshopper). [snip] Dear N & Peter, It's common to assume that recumbents have an aerodynamic advantage over the traditional diamond frame, but the advantage is actually limited to fairly extreme recumbents. You can see some of the surprising details on this speed calculator page: http://www.kreuzotter.de/english/espeed.htm Hovering the mouse over the radio button for the type of recumbent will pop up a picture that gives an idea of what a particular model looks like. After selecting a model, clicking on calculate at the bottom will give a predicted speed for the default values and the drag area used for the calculation. mph frontal type 17.1 4.3433 recumbent long wheel base 17.3 4.7889 df hands on tops 18.5 3.3781 recumbent short wheel base 19.4 3.2559 df hands on drops 20.5 2.7111 df triathlon bars 21.2 2.1748 recumbent short wheel base racer 22.3 2.0397 df superman position 23.1 1.5504 recumbent lowracer Obviously, these are idealized guides to what a particular bike and rider will do, with different tires and transmission efficiences affecting things. But for the same rider and power, it takes a recumbent that stresses speed instead of comfort to improve on the aerodynamics of an ordinary diamond frame: http://www.bicycleman.com/history/im...-record_lg.jpg Cheers, Carl Fogel |
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