Planing

[Mark Kelly]

Storing and releasing energy no doubt. But when it releases the energy how does that help move the bicycle? With a bicycle flexing laterally at the BB, and then returning, how can that propel the bicycle forward?

The whole smoothing power transmission thing I kinda get, but 'getting energy back' I'm not buying.

Dustin

I don't know how it happens, in fact I don't know whether it happens at all. I was pointing out that I thought Eric's response was a little narrow given how much we don't know.

Here's one possibility, to be taken purely as idle speculation: It could be the case that the energy return from the frame helps lift the leg at the end of the power stroke. My right leg weighs around 20 kg, so accounting for joint mechanics it will cost around 30 - 40 J to bring the pedal and attached leg from BDC to TDC. If we accept the previous estimate of 5 - 10 J stored as strain energy in the frame, it would in principal be possible for this to be entirely absorbed.

Note again, I'm not saying this is what happens, I simply don't know what happens and IMO neither does anyone else. I'm just not dismissing it until someone shows me, with instrumentation, that it doesn't happen.

[thollandpe]

How can the conversation about energy storage in a frame stand apart from what happens when wheels and other drive train components are attached atmo? How can a human being isolate the sensations and say the material allows X to happen when so many ingredients make up the whole?

You can't. It's a very complicated system. And accurately analyzing it would mean accounting for the asymmetry of the bike, as in the different stiffness with pedal inputs left and right (left includes torsional stiffness of the BB) and asymmetrical lateral stiffness of the rear wheel.

[jclay]

Cool. I misunderstood.

Yes, you do; I'll interpret: The fact that you have made boatloads of wonderfully crafted bicycles or have ridden wads of different bicycles many miles, does not mean you have the answer to these questions or that you recognize how to get them. The answers to these questions will be found by other methods.

[e-RICHIE]

Yes, you do; I'll interpret: The fact that you have made boatloads of wonderfully crafted bicycles or have ridden wads of different bicycles many miles, does not mean you have the answer to these questions or that you recognize how to get them. The answers to these questions will be found by other methods.

They are your questions, not mine.

[Mike Mcdermid]

The answers to these questions will be found by other methods.

images.jpg

you aint wrong

[Dallas Tex]

..............The fact that you have made boatloads of wonderfully crafted bicycles or have ridden wads of different bicycles many miles, does not mean you have the answer..........

It kinda does.

[fiveller]

Jan's latest article, for those who care to read what he says, is pretty interesting. Essentially, the energy is returned by the frame returning from the deformation of the downstroke and applying tension to the chain at the bottom of the pedal stroke.

One can agree with him or disagree with him but, at the least, he has proposed a falsifiable hypothesis and has endeavored to apply analytical and scientific methods to prove or disprove it. It's okay to disagree with him but for us to simply wave our hands in the air and say "I don't think it does" isn't a good example of the scientific process. His methods may not be perfect but, within the constraints of his budget and time, doing better than most.

https://janheine.wordpress.com/2014/...cs-of-planing/

the finite element analysis he refers to:
https://web.archive.org/web/20060214.../Frameflex.htm

a graph from the link (but not on brown bag paper ) Please read the entire article and don't depend on just this graph

Crank_on_spring_forces.gif

[Dallas Tex]

Put a riderless bike into a work stand. Have someone grab the fork and torque it clockwise then counterclockwise. Have someone grab the seat stays and do the exact opposite to simulate the flex that occurs when riding.

Tell me how much the crank the spins the rear wheel.

[progetto]

So glad it's summer here, just had a nice swim.

[jclay]

Put a riderless bike into a work stand. Have someone grab the fork and torque it clockwise then counterclockwise. Have someone grab the seat stays and do the exact opposite to simulate the flex that occurs when riding.

Tell me how much the crank the spins the rear wheel.

Assuming frictionless bearings, not at all. That test arrangement doesn't mimic the application of forces at the rider and road contact points. The BQ and BikeFix articles, and Evgeniy's comments, explain the physical, testing and statistical approaches. They're worth careful review if you want to understand the details of the hypothesis and investigative methods.

Josh, as to BQ's testing "rigor": Within the constraints of tiny budgets and limited resources I think they've done a good job of applying sound scientific principles to the inquiry. On the whole, the case is more than "Solid conjecture based on some data correlation", but even if not the work is a useful contribution and far more grounded in principles of scientific investigation than most of the opposing comments I've read over the past couple of years.

[Too Tall]

There is a test setup that could be used and I *think this hits all the stops to create validity of a initial BQ claim.

Colorado Univ. did or used to have a full size "Inside Ride" treadmill that was fully instrumented and possibility for hooking riders up to a CART during testing. ( Inside Ride Super Trainer Lets You Ride Gradients Like in the Pro Tour - Operation Gadget ) Take one very fit athlete and two bikes + a well designed series of testing and you'd see physiologic outputs which correlate to the bikes.

Who has some loose change to blow? Velonews you listening??? NixFrixShun will supply the chainlube, least we can do (and afford).

[Dallas Tex]

That test arrangement doesn't mimic the application of forces at the rider and road contact points.

My 'test arrangement' is not trying to mimic those things. My test arrangement shows that no forward motion is generated by the sideways flexing and unflexing of a bicycle.

[Will Neide]

My 'test arrangement' is not trying to mimic those things. My test arrangement shows that no forward motion is generated by the sideways flexing and unflexing of a bicycle.

That's because it's locked in a bike stand. :)

[Dallas Tex]

That's because it's locked in a bike stand. :)

Only by the seatpost. Give us a minute. We will do the repeat without the bike stand, it won't take a but a moment.

[Dallas Tex]

That's because it's locked in a bike stand. :)

Test repeated without bike stand.

No wheel movement / no forward motion produced.

No energy energy release producing forward motion.

[GrantM]

Jan's latest article, for those who care to read what he says, is pretty interesting. Essentially, the energy is returned by the frame returning from the deformation of the downstroke and applying tension to the chain at the bottom of the pedal stroke.

But if the frame doesn't flex at all, doesn't the energy just go in the chain?
Saying that the energy returns at the bottom of the stroke only reinforces the fact
the energy doesn't all get in somewhere else in the stroke. I'm not science friendly,
admittedly, but I'm sure that at best 2 plus 2 still equals 3 plus 1. Moving around
the power transfer doesn't make it more effective? Does it?

With regards to the muscle fatigue and "peak force" theory... This makes sense.
But you'd think the rider is the better arbiter of effort, not the bike. just How much
force goes into each stroke is what we do managing our effort, I'd think that we
have much more effect by moderating how hard we push and at what cadence we
pedal, than the frame lopping off peaks for the point of 'saving' our legs.

As has been pointed out, it's no coincidence this discussion has been carried by
long distance, steady state riders. For other scenarios, ymmv.

Grant McLean

[GrantM]

as to BQ's testing "rigor": Within the constraints of tiny budgets and limited resources I think they've done a good job of applying sound scientific principles to the inquiry.

I'd be interested in seeing blood lactate levels, rather than "my legs felt warm and tingly".

The guys at GCN have done several lab tests; clipless vs flats, standing vs seated climbing; slow vs fast cadence.
All produced results with power, lactate, oxygen consumption, and heart rate. Perception was often different
than the numbers. (Videos of experiments on YouTube)

[Matthew Strongin]

I'd be interested in seeing blood lactate levels, rather than "my legs felt warm and tingly".

The guys at GCN have done several lab tests; clipless vs flats, standing vs seated climbing; slow vs fast cadence.
All produced results with power, lactate, oxygen consumption, and heart rate. Perception was often different
than the numbers. (Videos of experiments on YouTube)

Yep. Perception will often be different than data when the human brain is included as one of the variables in a test. To really get to the bottom of this, one should start by isolating as many variables as possible to understand how each component of the system works in isolation and then start to piece together the entire system with further testing. But any test that relies on a person to relay how something felt to them will be skewed. Back in school I studied Neurophysiology. I had the opportunity to work in a lab studying hearing and otoacoustic emissions. Instead of a traditional hearing test, which is often skewed by people predicting when a tone would be played, we were using a tiny microphone to capture the sounds the inner ear makes in the process of hearing. The data showed pretty clearly that what people thought they heard and what sounds actually stimulated their cochlea were not the same. My point is that a test of whether a frame stores and releases energy in a productive manner should remove as many variables as possible. Humans are a huge variable.

[GrantM]

Perception will often be different than data when the human brain is included as one of the variables in a test.

The thing is, what exactly are these tests for? What if the flexy frame is slower than the stiff frame,
but people like the ride quality of the flexy frame better? Doesn't that make it test 'better'?
Or what if they like the feel of a stiffer frame better, and it's a tiny magnitude slower? Who cares?

Mostly this whole issue strikes me as a contrarian exercise on the part of the advocates.
It seems to me to be about trying to demonstrate that blue is faster than red,
because red is what the majority of people think is better. I see no reason not to like blue,
if that's what floats your boat.

-g

[Matthew Strongin]

The thing is, what exactly are these tests for? What if the flexy frame is slower than the stiff frame,
but people like the ride quality of the flexy frame better? Doesn't that make it test 'better'?
Or what if they like the feel of a stiffer frame better, and it's a tiny magnitude slower? Who cares?

Mostly this whole issue strikes me as a contrarian exercise on the part of the advocates.
It seems to me to be about trying to demonstrate that blue is faster than red,
because red is what the majority of people think is better. I see no reason not to like blue,
if that's what floats your boat.

-g

I totally agree. I was coming from the angle that if one wanted to prove the theory an attempt to limit variables in an academic or scientific manner would be key. Personally, I think that the flex of the frame matters little compared to other real world factors such as nutrition, rest, temperature, fatigue, tire pressure, etc.. I'm always fastest on whichever bike I'm riding the day I am most fit. That's good enough for me.