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
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I agree, in fact my last message was trying to sum it up. I think we can all agree that we don't really know... And I am probably going to test Bikedrive, they offer a two week try-it period :). I'll be back with my observations.
/Dick
----- Original Message ----- From: "Frederik Van De Walle" frederixie@hotmail.com To: hpvs@lists.lysator.liu.se Sent: Saturday, October 26, 2002 5:51 PM Subject: [hpvs] Re: pedalling technique
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
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Frederik Van De Walle -
Richard Vizins