Lyrebird Cycles

[Mark Kelly]

After I finished my stint in the Navy, where I’d trained as an aeronautical engineer, I went sideways into biological sciences and got as far as starting a PhD scholarship before figuring out that academia wasn’t for me. I then moved into winemaking where I’ve worked for most of the last thirty years with interludes working as a brewer, a process engineer in the food industry and running a business where I designed and built bespoke audio electronics. Within any of these fields I rapidly became the troubleshooter / problem solver, trading on my ability to absorb a lot of information quickly and apply bits of it to fields where it didn’t formerly belong. Basically, I have a brain made of flypaper: all kinds of random shit sticks to it.

While I was working as premium winemaker at the now sadly defunct Seppelt winery in Great Western, VIC in 2008-09, I spent a lot of time on my old steel road bike in the Grampians range, particularly the Mt William Climb, http://theclimbingcyclist.com/climbs/mt-william/ which is a beautiful road but a pretty rough surface. One day whilst dodging holes and cracks I found myself pondering the question of what made “ride quality” and the thought struck me that it was similar to a signal to noise ratio problem in acoustics, the signal being the responsiveness and road feel of the frame, the noise being ride harshness and road buzz. My original theory was that these things resulted from different vibrational modes of the bike, so I set about designing a way of encouraging the “signal” modes and discouraging the “noise” modes by selectively modifying the wall thickness of a titanium frame.

I proposed this idea to Darren Baum on a very memorable day http://www.velocipedesalon.com/forum...l%23post369554 in 2009 and although Darren made a very generous offer which would have helped with the development, I could not afford to take him up on it at the time. A little later I bought a cheap US made straight gauge Ti bike frame, a power file and an ultrasonic thickness gauge and did it myself. To provide something of a control, I rode the bike in its unmodified condition for long enough to become familiar with its character, the disassembled it, modified the frame and reassembled it exactly as it had been, including tyre pressures. The process took me around a week and I expected any effect to be subtle at best. It wasn’t, the bike was very different in feel.

I took this as a demonstration that the way the frame itself flexes / vibrates is important for road feel and that doesn’t seem like anything remarkable, though it’s news to some. Much of the process involved in the change was similar to externally butting the tubing so it was possible that this was the source of the effect I was seeing. BTW that’s also why I haven’t explained much about modal vibration theory, since it’s A: easily Googleable and B: no longer the basis for what I am doing. I became convinced that that the way the frame itself flexes / vibrates isn’t the entire answer to the ride quality riddle and may only be a small part of the answer.

At some time during this my Father in Law, who makes and repairs stringed instruments, pointed me in the direction of the types of woods luthiers use, known in the trade as tonewoods, and the increasing interest in the use of Australian tonewoods. I started investigating the acoustic and mechanical properties of these woods and became convinced that they would be able to be incorporated into the structure of a bicycle. I put this idea together with some of the materials research I’d done for the audio business to come up with “The Tonewood Project”.* http://www.velocipedesalon.com/forum...ect-31007.html

The first bike I built was in 2012, by which stage I’d been playing with these ideas for around three years, including a lot of time working out ways of fabricating the tubes and incorporating fibre composites. This first bike incorporated a lot of stainless steel because at first I wasn’t sure that the tonewood composite construction would be durable enough. After a year or so of trying to batter it to death with no success I became more confident and the next prototype had stainless chainstays and tonewood composite everything else.

By this stage I had enlisted VSalonista Rich the Roadie as beta tester - basically as a reality check because it’s awfully easy to become prey to confirmation bias http://www.sciencedaily.com/terms/confirmation_bias.htm when you’ve been working on something for this long. I asked Rich because he had a lot of experience with some excellent bikes and while he was interested in what I was doing he wasn’t convinced, so he would truly be a fresh pair of eyes. Rich has written about his impressions here: http://www.velocipedesalon.com/forum...s-39471.htmlin short, his response to the bike confirmed that at the very least if I was imagining this stuff it was a collective hallucination.



*The information in this post is now largely superseded, my techniques have been refined over the years since it was posted.

[Mark Kelly]

Meanwhile I dreamt up the name Lyrebird Cycles: The Lyrebird (Menura novaehollandiae) represents an extraordinary fit with what I’m doing. It is native to the montane forests of south eastern Australia which are both part of the inspiration for the bikes and the source of some of the tonewoods I use, plus it’s subtly beautiful and renowned for the musicality and complexity of its song:



I also had an idea for the script I wanted to use, taken from the lettering used on veteran’s honour boards around the country: the particular example I used was from Prahran, where one of the names on the board is “Monash, John Sir”:

Monash, John Sir.jpg

Sir John Monash was the commander in chief of Australian forces in WW1 and yet there he is on the board with the ordinary soldiers.
On a personal note: I didn’t realise until later that he was the signatory on the citation for my grandfather’s medals for bravery under fire at Albert (near Pozieres) in 1916.

Armed with an idea of what I wanted but not the talent to make it happen I asked for help on VSalon to get a font designed on this script and perhaps develop a logo. The depth of talent in this place is extraordinary: member Chooey (Melvin Choo) came on board and has done some extraordinary work.

Initially we spent an afternoon talking about what I wanted to achieve and where all this had come from, with me typically wandering off on long tangents about such things as the association of lyrebird habitat with the myrtle beech and the importance of the myrtle beech to the history of the concept of Gondwana whilst Melvin asked lots of pertinent questions about the relevance of these things to the project at hand.

Melvin then got to work on some concept sketches that embodied the more relevant ideas:

Scene 1 Lyrebird.jpg

It's worth clicking in these two images to see the detail in Melvin's work.

These are just some of the pages and pages of sketches he did: he put a huge amount of work into developing these ideas and liaising with me on how they fitted with what I wanted to do. Some things were very fluid: myrtle leaves went in and out of the design several times before finally being rejected. Some ideas came in and simply stuck, such as having the lyrebird “in song” and having five linear feathers to evoke the musical stave:

Scene 2 Lyrebird.jpg

The final design is wonderful:

Logo Black Gold.jpg

It balances elegance and complexity, it is at once laden with signifiers yet able to be taken as an entity by itself. I couldn’t be happier.

[Too Tall]

Your story is compelling and I LOVE the brand logo.

[Mark Kelly]

Josh

Thanks for your encouragement. This wouldn't have worked out half as well without VSalon.

Speaking from wine industry experience, it's normally hard to find a good designer and it's pot luck whether they actually understand what you are on about. Chooey is enormously talented and has shown great insight into how my made ideas could work.

[Mark Kelly]

Acoustics part one:

As I’ve mentioned before my Father in Law is a luthier, he makes and repairs stringed instruments; guitars and banjos (we try to forgive him for the latter). He pointed me in the direction of the woods luthiers use, known in the trade as tonewoods. These are woods which are believed to have properties which allow the instrument makers to “voice” their creations by manipulating the effect they have on tone colour. This appears to involve the material preferentially damping frequency ranges corresponding to certain overtones whilst allowing full energy recovery at primary vibration modes: too much damping at these modes would mute the “voice” of the instrument.

There is currently a lot of interest and research into Australian tonewoods: there are about 2000 species of hardwoods that grow here (and mostly nowhere else) and they include the tallest, largest and possibly the hardest hardwoods known. At the same time Australian Eucalyptus species are the first choice for feedstock in fine paper production worldwide: that may seem like a non-sequitur but it’s actually relevant, more on this later.

So I started looking at the properties of these tonewoods, focusing on the velocities of sound (yes, that’s a plural, there are several of them) and acoustic impedances. The acoustic impedance of a material is given by

z = ρ v,

eg it is the product of the density and the velocity of sound in the material.

For some years I have been involved in audio design as a side line, I’m primarily known for producing very high performance motor drives for turntables but I also did a lot of design work on other aspects of audio design. This included research on the way that motor vibrations propagate through the materials used in the turntable base structure and a large part of this work looked at the way that vibrations cross the interface between different materials, which is largely governed by the difference in acoustic impedance: the coefficient of reflection at a boundary is the proportion of energy which fails to pass across the boundary and is given by

R = ((Z1 - Z2) / (Z1 + Z2))^2

It therefore becomes important to minimize the differences between acoustic impedances of the parts of a structure to create an acoustically coupled whole. If two materials with very different acoustic impedances are to be coupled one method is to interpolate materials with intermediate impedances: because the reflection coefficient is governed by a square law, the net reflection is effectively reduced. Anisotropic materials like woods and fibre composites naturally have different acoustic impedances in different directions and this can be manipulated to achieve improved coupling by orienting the materials correctly.

The scale at which this is relevant is governed by the wavelength of the vibrations which is in turn a function of the frequency and the velocity of sound in the material. The velocities of sound through a material are a function of the stiffness and density: according to the Newton – Laplace equation

c= ((δp/δρ)s)^(1/2)

eg the velocity of sound is the square root of the stiffness to weight ratio. This is obviously a useful metric for materials to be used in making lightweight highly stressed structures like guitars or bicycles. It turns out that the extensional velocities in some of these woods are equal to those of titanium and aluminium alloys.

It seemed to me that these were good candidates for an experiment on the effect of acoustic materials on ride quality, so I started looking at how to incorporate all this into a bicycle frame. I knew from the outset that I would need to incorporate fibre composites to achieve the properties I wanted, so I set out to look at the acoustic properties of the various available fibre composites. One key decision here was to get hold of some boron fibre composite; Gary Klein’s original research way back in the 80s indicated that it had interesting acoustic properties. I spent quite a bit of time looking at ways of constructing tonewood /composite hybrid structures and formed some theories about how the interactions between the materials affect the propagation of vibrations through them.

A further explication of this will require another post with lots more equations.

[Too Tall]

Read every word. This is fascinating.

[Mark Kelly]

Thanks Josh. More following.

[Mark Kelly]

Much of this post is a digression on the physical basis of acoustic transmission in solid materials, it can be skipped completely if you don’t like maths but that will limit your understanding of what comes later.

In the second post I mentioned that the speed of sound in a material and the acoustic impedance of that material are functions of the density and stiffness(es) and that not all the acoustic energy in one material can pass across the junction between it and a material of different impedance. Now imagine a pulse of vibration entering a long thin structure like a bicycle tube, each end of which is attached to something with different acoustic impedance. Some of the energy that reaches the end will be reflected back and some will go through. Of the energy reflected, some will travel back to the other end where the same thing happens again. If the various reflections add to one another, the energy travelling within the structure will continue to build until the amount that escapes at each end or is dissipated by damping balances the amount coming in. That's a resonance.

The energy coming in doesn't need to be constant, it can occur once every few cycles so the resonance can occur at multiples of the input frequency as long as the energy doesn't dissipate completely between the energy inputs. If more than one frequency is present resonances can also occur at multiples of sum and difference frequencies (although this generally requires some non-linearity to be present). There are, of course, complications:

Firstly, the way that the energy reflects at the boundary depends on the nature of the impedance difference as well as the amount. If impedance at the boundary is higher than the impedance of the element, the reflected wave will be in phase whereas is the material at the boundary is of lower impedance the phase will rotate by 180 degrees. In phase reflection favours even multiples of the original frequency, combining in phase and out of phase reflection favours odd multiples. This is partly why a flute sounds different from a clarinet, for instance: the flute has two “open” ends so it favours even multiples while the clarinet has one closed end so it favours odd. Even harmonics are euphonic to humans so we interpret the flute sound as smooth and the clarinet as honking.

Secondly, whilst air can only support longitudinal waves, where particle motion is in the same direction as the propagation, solids can support both longitudinal and transverse waves: a transverse wave has, as the name suggests, particle motion at right angles to the direction of propagation. These are called P waves and S waves respectively, because in seismology the longitudinal wave is the first to arrive (the primary wave) and the transverse wave comes later (the secondary wave). This shows that they travel at different speeds, but I said speed was a function of density and stiffness, so how could that be?

Because the stiffness of a material is not the same for all possible stresses. The various kinds of stiffness are related through a property known as the Poisson’s ratio of the material. Poisson’s ratio is fairly easy to demonstrate: grab a rectangle of anything moderately flexible like a pencil eraser and try to either compress it or stretch is in only one direction, say along the length. You’ll notice that it does the opposite across the direction of stress: if you extend it, it gets thinner, if you compress it, it gets fatter. The ratio between how much you stretch it and how much thinner it gets is called the Poisson’s ratio, (symbol is lower case nu (ν)). BTW for the rubber eraser it is 0.5 so there’s no change in volume, this will become important later.

Poisson’s ratio is a result of the mechanism of distortion within the material: if there’s a crystal lattice eith regular bond patterns these act like springs and some of the energy used to distort the springs in one direction shows up as distortion in the others while some of it shows up as a change in volume of the material. For materials which are essentially cooled fluids (like the rubber of your eraser) there is no crystal lattice so essentially all of the energy used to move the molecules in one direction shows up in the other directions, therefore there’s no change in volume.

There are four important kinds of stiffness that come from this. The first is the resistance to change in volume, called bulk modulus (symbol is capital K).

The second is the most familiar kind of stiffness, the elastic or Young’s modulus (symbol E), which is the ratio of how far your rubber stretched to how hard you pulled it. It is related to the bulk modulus by

E = 3K.(1 - 2ν)

If you try to move some bits of a material sideways with respect to the other bits, called shearing, you strike a different modulus called shear modulus (symbol G). It is related to bulk modulus by

G = 3K.(1-2ν) / 2(1+ν)

The last is the P-wave modulus (symbol M) which is like the elastic modulus but for uniaxial strain*. It is related to the bulk modulus by

M = 3K.(1- ν) / (1+ν)

For most metals Poisson’s ratio is about 0.3, so the shear modulus is about 28% of the P wave modulus. Since the propagation velocity is the square root of the stiffness to weight ratio, the propagation velocity for S waves is correspondingly slower than for P waves, again in metals the S wave velocity about half of the P wave. Since the resonant frequency is a function of path length and propagation velocity, the resonant frequencies for S waves and P waves will also be different.

Ok, so now we’ve covered acoustics in solid materials 101, how is this relevant to bikes? That’s the post after next, I need to provide some detail on composite tube construction for it to make sense so that’s the next post.

*The explanation of uniaxial strain requires an understanding of vector physics so I'm not even going to try. There's a good one here

[RichTheRoadie]

I don't want to interrupt the flow of Mark's instalments too much here so I'll add more after he has completed what he has to say.

All I will say for now is, the more I read the more I understand that the ride quality of #2 of the bikes Mark has built for me to test isn't an accident at all. I really wish more of you could ride them (particularly #2). For that matter, I wish more of you could see the finish in person too.

[Mark Kelly]

No, fire away, the next section is proving a bitch to write, the first draft is total gobbledegook.

[Too Tall]

I won't like reading this requires intense focus and I like to do it all at once AND I'd love to ride a bike to see what you've accomplished.

The "story" as such could be summed up with prose but we are the lucky ones who get to peek into your process.

Do these bikes feel like [ ] anything familar to me such as a light tubed steel bike?

[corko]

Glad to see that you've finally been 'smoked out'...... No one can accuse you of not having put much thought into it..... Jewish......

I need to reread these posts......

[corko]

Glad to see that you've finally been 'smoked out'...... No one can accuse you of not having put much thought into it..... Jewish......

I need to reread these posts......

Damn auto correct....... Should have read 'jeesh' ......apologies etc.

[Too Tall]

Damn auto correct....... Should have read 'jeesh' ......apologies etc.

LOL. Autocorrect is a bear. Carry on.

[Mark Kelly]

I'd love to ride a bike to see what you've accomplished.

I'd be really interested to see how my techniques work out building a bike your size.

Do these bikes feel like [ ] anything familar to me such as a light tubed steel bike?

IMO they are unlike anything else. This thread is about why.

People who come to one off a metal bike tend to remark on the Lyrebird being smoother and flowing over the surface better.

People coming to them off carbon tend to remark on the Lyrebird feeling lighter and more responsive.

One thing no-one's ever said is that they feel "wooden".

[RichTheRoadie]

I'd be really interested to see how my techniques work out building a bike your size.

I'd love to understand whether the ride qualities I feel are translated to a Toots-size machine.

Mark - Your own bike is on the larger size, isn't it?

IMO they are unlike anything else.

Seconded. Similarities with the ride of steel, but different. Comparisons with the ride of carbon, but different. Damping along the lines of Ti, but different.

I've struggled to pinpoint and formulate what that 'different' equates to in each case. It's become so hard to decide what it is that I have begun to conclude that it is Mark's theory about resonant frequencies working that is creating that 'different'. I am beginning to really believe that this 'different' is simply how this 'wood composite' (which seems like a more appropriate term than simply calling them 'wood') rides as a material, in the same way that we describe how each of the other materials tend to ride. And, FWIW, it feels bloody good.

People who come to one off a metal bike tend to remark on the Lyrebird being smoother and flowing over the surface better.

Absolutely. Even the first one of mine with its über-stiff front end rides more smoothly - at least in terms of muting road buzz, which is how I would describe a smooth ride - than my steel Gaulzetti did.

People coming to them off carbon tend to remark on the Lyrebird feeling lighter and more responsive.

Both of mine are definitely more responsive than my Trek Emonda was and the second one is very comparable to how I remember my Cervélo R3 being - perhaps even bordering on being slightly more lively (and the R3 is still one of my favourite bikes, which says a lot to me).

Pinpointing whether or not they feel lighter is tricky, but I can believe it. My second Lyrebird is currently setup with a standard chainset and it somehow feels easier to ride than my Gaulzetti on a semi-compact chainset and lighter wheels. I guess that could be translated to it feeling lighter. I even managed a 4km climb on the standard chainset with the tyre rubbing the frame after popping a spoke on my first ride on #2 - when I repeated the same climb on my fully-functioning Gaulzetti the following week I couldn't understand how it felt so hard (obviously there could be a whole heap of other factors at play here though).

I've been challenged as to whether my perception of these bikes has been down to 'new bike elation'. This could be fair comment, except that in my experience that only applies when you buy a bike that you really want to be good, whereas I was lucky enough to be asked to test these. Additionally, as Mark has said, I wasn't convinced by his theory and, despite having really liked #1 (even with the über stiff front end), I had feared that #2 might go backwards in terms of ride quality because Mark was trying so many different things over #1 (compact geometry, OS HT, different [and shorter] chain stays, Serotta dropouts, truly integrated Di2, speedboat-inspired finishing). In reality, and as I have said a number of times now, #2 might well be the best bike I have ever ridden - and I really, genuinely mean that.

My wife commented the other day how I seem more keen and excited to ride at the moment. Even she asked whether it was "that new wooden bike" that was making my riding more enjoyable. She might just be right.

[Mark Kelly]

Mark - Your own bike is on the larger size, isn't it?

Not that big. First one was ~60 cm as it was intended as a touring bike. Second one is 58.5, more of an allroad bike.

Mark was trying too many different things over #1

FIFY.

[cp43]

I'd be really interested to see how my techniques work out building a bike your size.



IMO they are unlike anything else. This thread is about why.

People who come to one off a metal bike tend to remark on the Lyrebird being smoother and flowing over the surface better.

People coming to them off carbon tend to remark on the Lyrebird feeling lighter and more responsive.

One thing no-one's ever said is that they feel "wooden".

Do you have numbers on the acoustic properties of steel/ti/carbon bikes? I'm curious to know if it's possible to quantify the differences in ride feel. Hopefully my question makes at least some sense :)

Thanks for putting the time and effort in to writing all this up. I can't say I'm following all of the math, but it's been a great read!

Chris

[RichTheRoadie]

Do you have numbers on the acoustic properties of steel/ti/carbon bikes? I'm curious to know if it's possible to quantify the differences in ride feel. Hopefully my question makes at least some sense :)

That would be good to see - especially as a direct comparison to a built Lyrebird - if such a measurement is possible?

I can't say I'm following all of the math

Likewise! As I said before on the Gallery thread for Lyrebird, this is me reading the math:



...but seeing it published for all to see somehow gives more weight to what Mark is doing, so I'm glad it is out there to be read.

[Mark Kelly]

Do you have numbers on the acoustic properties of steel/ti/carbon bikes? I'm curious to know if it's possible to quantify the differences in ride feel. Hopefully my question makes at least some sense :)

Thanks for putting the time and effort in to writing all this up. I can't say I'm following all of the math, but it's been a great read!

Chris

I have some numbers and am in the process of generating more: I need to buy a new transducer kit to feed the signals to the cumulative spectral delay analysis package on my computer. The project is to run a spectral analysis on frames with similar geometry but made from different materials: I have tonewood composite (natch) and Ti already. I will shortly build the steel and carbon test mules and I intend to buy the Al one (not worth the learning curve).

I intend to publish some of this in due course but it won't be until much later this year.