HPVS

hpvs@lists.lysator.liu.se

3 participants
7341 discussions

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 23 Oct '02

23 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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Re: Vevarmar -->pedalling technique
by Frederik Van De Walle 16 Oct '02

16 Oct '02

Hej hej, My name is Frederik and I have been trying to read along with your Swedish mailing list, sometimes very interesting. BTW, I'm from Belgium and I study at KTH in Stockholm in an international program in English, jätte trevligt :-) Anyway, I have an 'opinion' on all the Bikedrive, Biopace stuff and even short and long cranks for that matter. I think, if these alternative systems have any gain, it is from making better use of the pedalling technique the cyclist uses. With this I mean that, if there is a gain with these systems, it is not because they are 'wonder' system of mechanics by themselves, but of adaptation to the individual biomechanics (=the pedalling style/technique). To remind: P = F x V or P = F x L x C with P = power F = force on pedal in circular direction V = speed of the pedal L = Length of the crank C = cadence I think a effective pedalling style on traditional cranks can be quantified as followed: A The force on the pedal is always in the direction the pedal moves B Good use is made of the circular momentum of the spin to smoothen out peak forces and to overcome the upper and bottom dead points C The cadence is so that you can apply all your force without discomfort and as such that you can still keep good technique from A and B. If this pedalling technique of a certain rider is not good, we are offered two options: - Change the geometry of the movement - Improve your pedalling technique/ style Now take Biopace and Eggrings etc. this is a classical case I would say of adapting the geometry to the cyclist. From a pure mechanical point of view, there is no reason to believe that one or the other is better if your style is good. But, if it feels better and more fluent, than it is probably better (usually if you like to excercise a lot of force in the downward stroke). So this could improve point B for some people. Length of cranks. Basically, if you shorten the cranks (L), you have to increase your cadence C to keep the same power P. And the other way around. So you can use this to change cadence. Since most recumbent cyclist find it difficult to keep a high enough cadence, shorter cranks could be a solution for a better pedalling technique with more 'momentum'. So you can use this to influence point C for a better pedalling technique. Bikedrive is a difficult proposal to say something about. In a way it is similar to eggrings or biopace, with the difference that when you load the spring with a certain force F, it coincides with a higher momental speed V and when the spring unloads, it coincides with a reduction in speed. Basically this effect seems comparable to riding a bike with not enough stiffness in the chain line of the frame, but with less actual losses as a frame would have. I personally find this effect very unpleasant... but I can imagine it could work for some people. Some ;-) Powercrank is very interesting, because it addresses a major flaw in the pedalling technique of most cyclist: in the backstroke the leg gets lifted by the opposite pedal, effectively having force in the wrong direction. I think everyone should at least try a powercrank-equipped bike. So this can improve point A for a better technique. I think my point is, the importance of an effective pedalling technique and possible improvement of it seems to me not often mentioned in general. The way you pedal seems to be accepted as a fixed fact. Pedalling is more complex than just pushing down. Also, our leg is sometimes too easily compared with a piston(engine), forgetting we can also exert considerable power in the other stages of the pedal stroke. Some literature I once read, said that the force we think are using to pedal is not necessarily in the instantaneous direction of movement of the pedal, although we think it is. Together with the backstroke this is what I suspect could be the main cause for lost efficiency of the pedal movement. Ideal to improve your technique would be to be able to measure the actual forces on the pedal real time and so adjust your technique. But more realistic, I would recommend the following tips that, I think, could possibly be way more effective than the costly wonder solutions like Bikedrive can give: 1 Get used to SPD or any other fixed but quick releasing link!! And use them. Without it, you HAVE to push in the wrong direction of the backstroke to keep your foot on the pedal. This IS BAD for efficiency!! Avoiding this can be practised then by pedalling with one foot. 2 Experiment now and then with different cadence. - Very low cadence so you can focus on pushing in the right circular direction, also pulling/pushing your leg up and down on a recumbent. - Very high cadence to get used to making a very fluent movement, not just in circles but also with constant pedal speed (no peak forces of bouncing in the saddle) 3 Our mind and feeling has some delay. So instead of thinking of pushing your foot forward when you are already doing it, think of pushing when you foot is going up. Similarly, think of pulling down in the top position, pulling back in the forward position, pushing up in the lowest position of the pedal. You could say a 90 degree advance thinking is needed. This cannot be solved with any crank trick, so if you get this right, your power can go up seriously without using more effort. Of course this is only my experience. I usually think of pedalling technique when I have a little down in average speed. And usually just thinking about it raises my speed with 2-3 km/h :-) Anyway, I hope this was of some help, Frederik P.S: I will soon regain recumbent mobility, so if anyone in the neighbourhood would like to go for a spin I live in Upplands Väsby, near Stockholm. You can call me on 070 469 7210 _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx

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Leitra i Göteborg & efterlysningar
by Jan-Inge Ljungberg 15 Oct '02

15 Oct '02

Hej kamrater liggister. Hyggeturen avslöjade många hemligheter! En var t.ex. att det kanske finns en Leitra i Göteborg. Kanske något för spårhunden Peter Markusson att sniffa upp! Namnet på köparen var Bill och efternamnet har just trillat ur min övre hårddisk (huvét!) men Tero skrev upp namnet. Bill var/är någon sorts uppfinnare och utrustade Leitran med en sort roddmekanism förutom fotpedalerna. Några Leitror till ska finnas förutom de två som är kända i HPVS: Kalle Hallbom på Gotland och Tero i Flyinge. Någon Leitra har sålts till en Stockholmare och en till någon militär i Kalmar. Göran Hartzell har tipsat om en som fanns i Eskilstuna men numera är såld till Norge. Börja leta man vet aldrig vad som finns i stugorna. Det ska till exempel finnas någon röd Peer Gyynt (ursäkta stavningen) med framkåpa i Malmöområdet som var med på en utställning 1995 arrangerad av Kalle Hallbom men som sen dess inte synts till. Fridhems cykelaffär i Malmö påstås ha sålt några stycken sådana. Vänliga hälsningar *:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_,.-:*'``'*:-.,_:-.,_,.-:* Jan-Inge Ljungberg webmaster(a)liggister.org www.liggister.org

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Re: [hpvs] Leitra i Göteborg & efterlysningar
by Henning Wright 15 Oct '02

15 Oct '02

>Börja leta man vet aldrig vad som finns i stugorna. Det ska till exempel >finnas någon röd Peer Gyynt (ursäkta stavningen) med framkåpa i >Malmöområdet som var med på en utställning 1995 arrangerad av Kalle >Hallbom men som sen dess inte synts till. Fridhems cykelaffär i Malmö >påstås ha sålt några stycken sådana. > Johodå, den har dykt upp igen. Det är dels ingen Peer Gynt, men dock tillverkad av Radius som gör (gjorde) Per gyntarna. Den dök upp i Eslöv i somras när vi hade ett litet möte i samband med SM i vanlig cykel. Ägaren fich nätadresser så vi får väl se om han hör av sig, fast har han väntat så här länge kan han väl inte vara överdrivet intreserad. Henning

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HPVS