HPVS October 2002

hpvs@lists.lysator.liu.se

23 participants
39 discussions

trasig fälg + bygget
by Göran Thyberg 29 Oct '02

29 Oct '02

Hej visserligen ingen liggcykelfråga men ändå. En fälg med skada enligt nedan: http://medlem.spray.se/tuben7/galleries/021026/ Vad kan orsaka en sådan skada tror ni? Har jag kört på något som slagit sönder den eller är det ett utmattningsproblem? Den har gått ~400mil vara hälften på en trainer. Det är fråga om drivsidan på ett bakhjul med 32 oreducerade ekrar. Fälgen är specificerad som "Custom made for Bianchi by FIR". Mitt långsamma lowracerbygge går för övrigt framåt steg för steg. Nu har jag kommit fram till ett fungerande rullande chassi med sits och styrning klart. Håller på med drivlinan och vet inte hur jag ska få undan kedjan så den inte är i vägen för låren när jag trampar. http://medlem.spray.se/tuben7/cykel/lowracerbygge/index.htm Mvh göran -- Göran Thyberg, LM/ERA/RJZ/IT, epkgant, +46 13 287350 __o __o __o __o /\_ _ \\o (_)\__/o (_) _`\<, _`\<, _`\<, _`\<, _>(_) (_)/<_ \_| \ _|/' \/ (_)/(_) (_)/(_) (_)/(_) (_)/(_) (_) (_) (_) (_)' _\o_

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Fwd: Liggcykelargument
by Peter Markusson 29 Oct '02

29 Oct '02

Hej allihop! Vidarebefordrat brev: > Från: Seinegård Marieanne <Marieanne.Seinegard(a)gp.se> > Datum: tis 29 oktober 2002 kl 09.56.34 (Europe/Stockholm) > Till: "'peter.markusson(a)telia.com'" <peter.markusson(a)telia.com> > Ämne: Liggcykelargument > > Ett argument för liggcyklar hämtat från FL-Net:? > > Tvingar du upp mannen i sadeln? > Precis bakom pungen finns det ett litet nervcentra. Det sitter inte så bra > till för cyklister, konstaterar Berlingske Tidende. Enligt forskarna kan > lång tids cykling göra att nervcentrat inte mår så bra och det kan leda > till > både bekymmer med potensen och till smärtor vid samlag. Fast forskarna är > noga med att påpeka att cykling trots allt är bra för hälsan och att de > positiva sakerna överväger nackdelen med potensen. (FL-Net) > > /Pöss > __________________________________________________________ > Marieanne Seinegård, Webbutvecklare > gp.se > Göteborgs-Posten > (...) > ___________________________________________________________ > > Med vänlig hälsning, Peter Markusson ----------------------------- Ekokompaniet Rådgivning - Bildelning - Miljö (Advice - Carsharing - Environment) Hemsidor/Homepages: http://www.ekokompaniet.se/ http://www.bildelning.nu/ Tel: +46 (0)31 775 26 36 Postadress/Mail: Svalebogatan 16 414 75 Göteborg Besöksadress/Visitors: Corps de Logiet, vån. 2 Klippan 6, Göteborg

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RE: [hpvs] pedalling technique
by Fridqvist, P.A.S. 28 Oct '02

28 Oct '02

As always I cannot resist these technical discussions. Please forgive me... Richard Wizins wrote: > Maybe you are right Frederik, maybe not. I am personally not > convinced that > we can pedal very much more efficiently than most skilled > cyclists already do. This seems plausible. There is so much money in pro cycling that it would be unlikely that the pro teams haven't already done what's within the reach of scientific investigation to promote the highest possible efficiency. This, of couse, dosen't exclude new scientific discoveries... > B. We have the issue of aerobic limitations. I.e. the > cardiovascular system > can not support an increase in power over any lenght of time > even if we have > the muscles to do it. This I agree is the limiting factor for power output for most cycling activities. > energy. One could argue that it "only" prevents us from > actually resting on > the pedals on the upstroke and thereby counteracting the push > on the other > pedal. There is no telling how much power we actually add - > it could well be > nil. Yes. The idea of Powercranks is to avoid spending some energy counteracting youself, i.e. pushing 'backwards' with one leg and 'forwards' with the other. Some energy would undeniably be saved if this can be avoided. It might be very little, though, maybe too little to bother. And maybe the action of actively lifting one leg instead of just letting it be lifted causes involvement of additional muscles, resulting in a nil gain or a loss. The human body is mechanically quite complicated (sic) and activating one muscle here generally requires another muscle there to be counteracting, to avoid the having body severely twisted... > Bikedrive on the other hand does address the problem of > erratic power. If > we accept that we have an spike of force on the down stroke > (or up stroke by > the way) which is in part lost on trying to overcome the bike's (and > rider's) moment of inertia (weight basically, in this case) we have an > interesting opportunity here. By storing part of the access > force (energy > actually) in the spring instead of "burning" it on a > fruitless attempt to > jump the bike forward we can use that energy during the > otherwise virtually > powerless 12-6 o'clock part of the cycle. Thereby we would add no new > energy, but we would waste less of what we have on fruitless short > accelerations (F=m*a). Well, storing energy as spring tension or as momentum would make no difference, would it? Only the momentum storage is more light-weight, and has no termal losses... BTW, the energy provided by each pedal stroke is small compared to the moving energy of the bike with rider, I think. I the energy of the moving bike was plotted, the pulsing caused by pedalling would be a tiny riddle on top of a comparatively steady line. > - My first impression of the Powercranks was a bit flawed. Their main > principle is preventing "resting" (pushing if you like) on > the pedal in the > up-stroke. Learning to use muscles to lift the foot will > increase effective > power (theoretically). If the power contribution in the > up-stroke remains > small (but not negative) it will do nothing to smooth the > power curve. This might work, but I'm sceptical. I am, too. But read the last lines below:

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Re: pedalling technique
by Frederik Van De Walle 26 Oct '02

26 Oct '02

Hey all, I think that things have been discussed 'sufficiently' and it is now time to wait for Dick to try and test Bikedrive. So what follows is just some ideas and stuff I thought about when I followed the past discussion... that might be interesting for you. -Some guy named Harrison measured already in 1970 that the rowing motion can give higher power than pedalling when the exercise lasts longer than 30 seconds, as in, not in sprints. This is when inertia of the rowing movement is maintained with a flywheel (in a test laboratory) but a bike at speed also has quite some inertia,... The explanation that for the fact that no HPV rowing records exist (well, actually, Derk Thijs had some records, for some time at least) is that the motion takes more space and so ultimately, aerodynamics suffer more. Ah yeah, also the power was greater with the butt fixed and the legs moving, instead of the whole body moving. It is quite obvious that THAT causes a lot of lost acceleration forces... -I actually once road an alternative drive that really worked. It was on an upright bike invented by a Belgian... inventor ;-) Anyway, he used a connecting rod system attached to the cranks that lengthened the crank length in the push position and drastically shortened it in the back stroke, so no need for clipless. Not only this, he also succeeded in having the time spent in the back stroke reduced and the time in the front stroke enlargened. As a result, it was a piece of cake to pedal HUGE gears, like 65-11 on 26 at a speed of 30 km/h was comfy. It really worked; yet sadly, his work is hardly acknowledged by anyone. Well, the construction is quite elaborate and cannot be implemented on a recumbent since the whole rod system would then point downward. Well, not in the form it was when I saw it anyway. Still to bad no one picks it up in the upright world. -If Bikedrive lessens peak force with 20%, it is because the resistance is 20% lower. Or because the local speed is about 20% higher (right?). OK, then you spend 20% more time in the dead points, transferring stored energy and inertia into the drive system. My question is, why not learn to pedal 20% faster and skip the dead points +40% faster? That is the whole trick of the 500W of professional record power, it is done at 110rpm. The change of inertia in the legs with a bikedrive system, +20% to -20%, 220 times per minute, must be quiet interesting at those rpm... and so the story goes on... forever ?? ;-) Just test it :-) Regards, Frederik _________________________________________________________________ Protect your PC - get McAfee.com VirusScan Online http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963

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RE: [hpvs] kul
by Fridqvist, P.A.S. 25 Oct '02

25 Oct '02

Jo, den var kul! Var kan man se den i verkligheten? Sverker

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kul
by Johan Fohlin 25 Oct '02

25 Oct '02

[Image]

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Re: Vevarmar -->pedalling technique
by Frederik Van De Walle 24 Oct '02

24 Oct '02

Richard Vizins wrote: >My main objection is that there is (as far as I know) very little evidence >that even the most skilled proffesional cyclists use more than a small part >of the down-stroke to produce power. I disagree :-) I am pretty much convinced that if that was really the case, it would be a very bouncy ride!* ;-) Also I know of a clear example where two brothers were doing the final sprint for a race (on lowracers) The one that had the better technique won very easily from his brother, although they had been racing together the whole race. The catch is, he won using ONE leg!! And the next year, when the other brother improved his technique, he couldn't even beat him anymore using both.... (I'm sure there are some other factors in play here, but still...) >It was this knowledge(from experiments) that initiated Shimanos ill-fated >BioPace project. >BikeDrive for instance is just another try at the same thing but with a different approach. Powercranks are very different visually, but really >also adress the same problem. By preventing the cyclist from lifting >his up-stroke foot with his down-stroke foot it prevents forces in the >wrong direction, thus smoothing the power over the pedal cycle. >BikeDrive does the same thing but by storing energy. I agree and I disagree. The explenation of powercranks is right, but I think Bikedrive and Powercranks are completely different issues. Bikedrive in no way punishes wrong pedalling technique as powercranks do! Maybe even to the contrary.... >Powercranks develops new muscles, I think that you can actually learn to pull pretty hard on pedals too. During continuous riding, I can keep up the same power only pulling the pedals and relaxing during the push, for quite some time. Sprinting and climbing capacity improve a lot when I have clipless pedals so I can really pull.... >Bikedrive doesn't require a lot of training and adaptation - which is best? Well, as I said before, I don't think very highly of bikedrive and I would like to try out a powercrank, but I wouldn't actually buy it. Yet. I would need to try it first, it's the law of stubborness ;-) >Do any of them make a difference? Even if there is scinetific 'proof', for me it does not guarantee it works for you, as I believe there is room for a lot of different pedalling techniques for different people. So I say, try it!!! If you buy it, you can always sell it... maybe to see how many people want to get rid of theirs is a better indication if it works ;-) Cheerio, frederik *a bouncy ride: a simple calculation: Let's say we assume 'one-hour record' power: 500W @ 110 rpm equals a torque of (500 * 9,54 / 110)= 43Nm average. For one leg this means 21,5 Nm. If only during one fourth of the pedal stroke there is effective torque (downstroke), then the torque should be 21,5 Nm x 4 = 86Nm. With a crank length of 0,17m this means an upwardds force of (86Nm/0,17m)=506N or for normal gravity 51,56 kg! So if the assumptions made here were true, the rider has to withstand blows of 50 kg, 220 times per minute!! To me it is clear no such forces exist, because in any aerodynamic position and certainly Boardmans 'superman' position, these forces would be unbearable. Of course very simplistic calc, but there should be some truth in it _________________________________________________________________ Unlimited Internet access for only $21.95/month. Try MSN! http://resourcecenter.msn.com/access/plans/2monthsfree.asp

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Ny bentrideronline + omslagspojke!
by Jan-Inge Ljungberg 22 Oct '02

22 Oct '02

Hej kamrater liggister Lite dött på listan. Tänkte liva upp lite om det går i vinterkylan. Hoppas ni inte gått i ide. Nya www.bentrideronline.com har kommit med ett nytt nummer. Lite mindre än vanligt i väntan på ett decembernummer som utlovas bli extra stort. I den nya testas ICE Trice Micro något att dregla över verkar det som men med en prislapp som får en att gråta blod. Det rapporteras från en stor amerikansk cykelmässa och bentriders läsare har utsett årets liggcyklar, mycket amerikanskt men årets europeiska är Optima Stinger. Det första numret av Ligfiets& som nederländska hpvklubbens medlemstidning heter numera (fd HPV-nieuws) pryds på sitt omslag av mig! Tyvärr står det några hundra människor framför mig men jag är med! Har ni bra ögon så står jag strax framför Henry Riedels cykel kallad Dyno. Strax till höger om mig står någon man i blåa kläder.Numret är kraftigt dominerat av sommarens evenemang Cyclevision. Det andra innehållet sitter jag och kämpar med för jag är inte så bra på nederländska men skam den som ger sig. Kylslagna hälsningar *:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_:-.,_,.-:* Jan-Inge Ljungberg webmaster(a)liggister.org www.liggister.org

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omröstning på dn.se om trängselavgifter
by Per Eric Rosén 22 Oct '02

22 Oct '02

Hej alla gröna HPV-människor! På dn.se (Dagens Nyheter) är dagens webfråga om trängselavgifter i Stockholm. Och det vill vi ju ha?! Även icke-08:or får rösta. Folk bryr sig om dessa omröstningar, även om de är ostatistiska, så * rösta direkt på förstasidan http://www.dn.se - går jättefort. * skicka vidare till andra om du vill :-) Detta kom ursprungligen från Fältis Stockholm-Uppsala-Gotland-lista. Hoppas inte någon ogillar detta mail ... /Per Eric, Uppsala -- ^): Per Eric Rosén http://rosnix.nu/~per/ / per(a)rosnix.nu GPG 7A7A BD68 ADC0 01E1 F560 79FD 33D1 1EC3 1EBB 7311

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nästa sommar....
by Anderz Näslund 22 Oct '02

22 Oct '02

Hittade ett kul projekt http://www.underwaterbike.co.uk/ Anderz

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HPVS October 2002