MIT Aluminum Bicycle Project 1974 (2016)(sheldonbrown.com) |
MIT Aluminum Bicycle Project 1974 (2016)(sheldonbrown.com) |
There's a fascinating, and very new, class of nano-laminate magnesium alloys called Long Period Stacking-Ordered (LPSO) alloys. These are very lean -- the standard version is 97% Mg + 1% Zn + 2% Y -- and they have outstanding mechanical properties. At an equal weight, they're much stronger and stiffer than 6061 aluminum, and the kicker is that this is generally true only if they're extruded. If they're not extruded, the laminate-like grain structure doesn't form properly.
Could make excellent bike frames.
Magnesium corrosion would still be a problem, though. I got some LPSO-Mg samples from Fuji Light Metals, in Japan, and they were quite badly degraded within weeks.
https://www.elmycycles.co.uk/m21b0s365p4804/1992-Kirk-Revolu...
https://www.bikeforums.net/classic-vintage/1279777-kirk-prec...
https://www.independent.co.uk/news/uk/magnesium-in-frame-to-...
https://www.flickr.com/photos/11521783@N05/albums/7215764801...
A friend had one. It cracked.
> "Kirk Revolution cast magnesium"
Cast magnesium is really weak/brittle compared to forgings and extrusions. Its use was not a great design decision on Kirk's part. I suppose they could have wrapped the casting in carbon fiber or something like that, to give it extra bending strength and spread out loads that might cause fractures, but then it would get expensive.
With modern understanding of composites, and complex layups with UD fibre, the "not comfortable, too stiff" is less and less true. The reduction in road buzz I got when I finally moved to CF handlebars was noticeable.
Presumably they'd also benefit from SMAT and other forms of surface modification.
That said, they're really good as extruded, and they don't appear to benefit as much from SPD as some steel and aluminum alloys do.
At a glance, though, the problem doesn't seem insurmountable. FSW appears to work.
That said, I wonder if there is a way to make frames more comfortable without having the flex absorb pedaling energy.
That said, we can extrapolate from mechanical properties. If we assume that both materials are tubes with the same wall thickness, and that we're looking at T300 carbon fiber (by far the most common type) in epoxy resin vs a standard research grade of LPSO, then:
- The CF will be stiffer
- The CF composite will be slightly less dense (1.6 gm/cc vs. ~1.8 gm/cc)
- The CF composite will have a slightly higher tensile strength, but the difference is very small and could be nonexistent in practice.
- LPSO-Mg will be more damage tolerant -- with better resistance to abrasion and better capacity to flex in a recoverable way in response to extreme mechanical stress. (Cast Mg alloys are undoubtedly worse than CF, but LPSO-Mg is a lot more like an aluminum alloy in this respect. It's a pretty ductile material.)
- LPSO-Mg should in principle be cheaper, though this is likely not going to be the case for a long time.
- LPSO-Mg will have better mechanical damping properties, so might transmit fewer vibrations to the rider.
That was when I realized what site I was on.
stripped example: https://weightweenies.starbike.com/forum/viewtopic.php?t=153...
https://www.reddit.com/r/cannondale/comments/1d9nind/2009_ca...
This time it was “Sheldon Brown’s personal bicycles” https://sheldonbrown.com/org/bicycle.html
That’s the essence of a great website.
https://en.wikipedia.org/wiki/Graeme_Obree
With his "old faithful" bike he built himself
I was looking at it in the museum last week and it still impresses me how intuitive he was about cycling. Things like integrating the pedal and shoe to save on height, and also reducing the q-number with the narrow bottom bracket.
I remember doing time trials with Graeme before he had created "old faithful" and he was just incredible
Graeme wrote a book on training a few years ago - its very home brew - but he was ahead of his time saying that you need to ride 25-28mm tyres on the road, rather than the 20-23 which were fashionable at the time.
I remember seeing an old aluminium bike in the Manchester industrial museum
This is from 1896 https://collection.sciencemuseumgroup.org.uk/objects/co84092...
And theres this https://collection.sciencemuseumgroup.org.uk/objects/co25722...
Doesn't give a date, but this is the one I remember, and seem to recall it being 1901
It's his wife! Harriet is Sheldon's wife!
This trend has continued -- it is very noticeable in road and mountain bikes.
But this trades off against impact resistance, aerodynamics, and the can-it-fit-between-your-legs-metric.
Frame “tube” dimensions driven by layup mold & mandrel/bladder requirements to minimize tooling and layup time
Press fit to reduce inserts and post mold operations with a “simpler” molded interface
Flat mount brakes to simplify mold shape and support simpler insert components
UDH and direct mount again the simplicity of molded in shape, minimal inserts, reduced post mold operations.
“Modern” UDH hangers move threaded components off the frame. much simpler than the old syntace style which need both precise thread alignment and/or frame tooling operations and/or additional inserts.
You could probably throw head tubes in here too; split races to avoid reaming, molded bare pseudo-press fit “cups”, and the absolute ridiculous sizes like IS47 and larger.
Many/most of those only help manufacturing costs for major frame factories. And are middling to suck for other materials and small volumes. Ex steel flatmount and IS47 is an absolute joke.
Rider weight massively outweighs the relevance of bike frame material, especially in the West where obesity epidemic has biased BMI upwards over the last half century.
I learned last week that my colleague bought a commuting bike from an old friend. A true once in a lifetime barn find. Mid 90s Klein Attitude, only used for a few weeks before being stored in the barn until 2023. My colleague is currently putting it through its second winter on salted, snowy roads.
What's the alt. timeline for the bike? Stored as a collectors item?
Ships in the harbor and all.
https://web.archive.org/web/20061103174315/http://www.kleinj...
I've have a lite ghisallo frame which I think was under 2lbs. The whole bike is under 15lbs and still manages to carry my 200lbs of weight.
Cinelli also had a version of their legendary Laser [2] bike with that setup.
1: https://bikecult.com/works/archive/03bicycles/takhionVVVV.ht...
2: https://www.pedalroom.com/bike/cinelli-laser-aero-pursuit-34...
There's some good info on bike frame materials here: https://bike.bikegremlin.com/11144/bicycle-frame-materials-e...
With a "diamond shaped" traditionnal cycling frame you have nearly 0 chance of a frame failing catastrophically. Usually the weaker part crack and your bike just end up creaking horribly and/or feel noodly. I have suffered and witnessed a number of alu and alu+carbon bonded frame failing at the glued joints.
Don’t need a bike manufacturer to do that for you though
Even Mullvad ad-blocking DNS is available for free, no app (and def no account!)
https://mullvad.net/en/help/dns-over-https-and-dns-over-tls
Nice thing is you can set your DHCP to hand this out to all devices.
On the flat, weight only affects you during accelerations - at a steady speed, it has no significant impact on performance. Aerodynamic drag and rolling resistance are constantly sapping away power, so features that reduce these losses are nearly always worthwhile even if they increase weight. Even on a moderately hilly road stage, aero trumps weight by a considerable margin; on the track, weight is almost entirely irrelevant, particularly in longer events.
A lot of riders like the feel of a lightweight bike, a lot of them believe that light bikes are faster, but that's only true on exceptionally steep stages or hill climbs.
The discipline of cycling that's the most weight-motivated is hill climbing. Track cycling really doesn't have that as an issue, and definitely does have a materials strength issue, so I'm not shocked they're not building to a weight limit.
Also, heavier riders are generally faster downhill as they have a greater terminal velocity.
No, unless they're Russian, they're not free falling. They have greater potential energy. And also increased traction, increased rolling resistance, and increased losses in wheel bearings and drive components due to friction.
If you push 300W on a 5kg bike or 20kg bike, the "workout effect" will be the same.
At the end of the day, if you are looking for "workout effect", it means that you're trying to achieve something, like winning races or going faster.
And for a given rider, with a certain weight and certain physiological abilities, they will go much faster on a 5kg bike than on a 20kg bike.
There is a whole world between <$1k bikes and those >$2k ones. Weight being an important part. Not only because it reduce the total weight of bike + rider, but also because a 5kg bike behave in a very different way than a 20kg.
It's like saying that cooking with a chef knife is the same as cooking with a sword.
Sure, after a certain point, the race for removing a few grams here or there is a luxury and many people tend to believe that spending $$$ on a lighter bike will fix their lack of fitness.
But modern bikes provide a completely difference than the old, heavy ones.
Yes, rider weight trumps it, but modern bikes in general just ride nicer and most of us who are not pros only test a dozen different bikes at most. It's a hobby, people like to splurge.
I'm less convinced. Firstly, I'm not convinced by the frame flex theory of ride comfort - I believe that the tyres are by far the biggest contribution to ride comfort due to the amount that they can flex which is far more than the tiny amount that the frame can.
Secondly, aerodynamics is far more important (if you care about speed/effort) and titanium is tricky to get into highly tailored shapes unless you resort to fancy 3d-printed frames.
Carbon would be my choice due to the design flexibility - by orienting the carbon fibres differently, components can provide strength/stiffness in one direction whilst allowing for compliance in other directions. Also the shape can be relatively easily changed - no need to always use circular tubes.
It'd be interesting to see a 3d-printed titanium frame that uses some kind of honeycomb internal structure to provide super strong/light frames, but I suspect it would be exorbitantly expensive.
However, you might find this interesting -- No. 22 bicycles has a (very expensive, prototype) titanium aero bike: https://22bicycles.com/products/reactor-aero . It hasn't actually seen a wind tunnel but at least it looks like an aero bike and they're talking about putting it in one. It is made using 3d printing (additive manufacturing) at least in part.
> Pricing for the final production version has not yet been finalized, but we anticipate a frameset (frame, fork and headset) price in the range of USD $10,000 to $15,000.
You would need enough force for the tires, wheels, saddle, handlebar, stem and seatposts to break/explose before the double triangle start flexing.
A typical bike frame follows a truss structure: stiff and unyielding by design. Vertical compliance is going to be found elsewhere: tires, exposed seatpost, chamois/saddle, fork, handlebar, tape.
Yet, how many roadies do you find talking about suspension seatposts? It's all because in that subculture emulating present and past pro racers is seen as cool, and anything else isn't.
If you are curious, a few people like CYCLINGABOUT [0] and Overbiked Randonneuring [1] have done some measurements and the data suggests that suspension seatposts provide even more reduction in vibrations than wide tires.
Rolling resistance increases are pretty marginal with compensating tire pressures (i.e., higher). Wheel bearing losses are de minimis.
Drivetrain component friction is not a function of rider weight.
Wheel bearing friction, duh. If the rider stands up while pedaling, it does. :)
It's about optimizing the whole system, not just one part of it.
That said, given how many of us are overweight, worrying about a couple of kilos on the bike is funny talk anyway.
For titanium, I'm seeing Black Friday deals starting at like, $3200-3500 (Lynskey / Litespeed). But they're often sold at higher prices than carbon bikes. (For my money, I prefer carbon frames -- you get more flexibility in tube shapes and the end result can be lighter and stronger than titanium.)
The specific 2000EUR figure might be European pricing. The lowest I'm seeing for any carbon road bike from e.g. Specialized with US pricing is $2400 for a two generation old Tarmac SL6 (this generation was current 2019-2021) or $2800 for a current Roubaix. The least expensive carbon road bike offering from Giant is $3300 US (TCR or Defy). (Though I'd expect to be able to find better deals at retailers trying to move old inventory than direct from the manufacturers.)
This bike isn't even on sale and it's under $4k and not a bad bike: https://www.giant-bicycles.com/us/tcr-advanced-2-pc-2025
10-speeds are most common, so you have to be ok with that; although some vintage bikes did have 3 chain rings. Older road bikes tend to have narrow tires, because everybody thought they were faster; 1/4" tires are workable on unpaved mixed use trails, but 1/8" will be pushed around easily by tree roots and ruts.
First you coat or anodize the magnesium, which I imagine needs to be done in any case. Then you apply a layer of epoxy. Then you wrap in carbon/epoxy. Done properly, there's no direct contact between carbon and magnesium, and you're probably less likely to see corrosion in the Mg-CF composite than you are with magnesium by itself.
I’m sure what you are saying could be done- especially to basically add stiffness to key regions of a carbon racing bicycle, but it would be experimental and I would not trust it to last a long time
That doesn't seem to be borne out by bike prices - it's entirely possible to buy a very usable carbon fibre bike for approx £1000 but I can't recall seeing a magnesium framed bike for £100.
Edit: looking at cheap frames on AliExpress, you're not too far off. I saw a magnesium alloy frame for approx £80 and a carbon fibre frame for £350. Not quite an order of magnitude though.
https://www.bike24.com/road-bikes.html?dynamicAttributes%5B2...
On a nice track, assuming a perfectly smooth surface and zero elevation change, I'm willing to accept the effect may not matter enough to care. But introduce even just a little bumpiness or some elevation change (perhaps in the track curves), and it might matter for someone pursuing the hour record.
However, cycling tracks are designed to be very smooth which is why high pressure tyres are still used there.
Here the English language obscures the physics. Sure, the black line on the track is at a constant elevation. But the tire's point of contact is different from the system's center of mass (CoM). CoM is key here. When a rider tilts in the turns, the CoM lowers. In the straights, it raises. So, you _are_ going up and down during the hour record.
The question now becomes: how much effect does this elevation change have?
It is one thing to be aware of the effect, run the calculations, and find the result is negligible. Has anyone done this? That would be an interesting analysis, and I'd like to see it.
With this in mind, I will make another claim: for a particular rider, there is an ideal line around a velodrome that would minimize center-of-mass elevation change. This line would be faster than the current black line. How much faster? This would be a fun simulation problem.
Another interesting connection: center of mass and bicycling explains why pumping works on a BMX track, a pump track, a trail, and so on. (There are other mainstream explanations, but I think the CoM explanation is the most elegant.)
The microaccelerations in the dead zone will be lesser in magnitude when you have a heavier bike plus system, but it will be more calories per m/s to recoup - while a lighter system will accelerate easier but have more acceleration to do. In the end the dead zone acceleration are calorically going to be exactly the same no matter the weight.
The CoM’s elevation change on a velodrome track is due to roll rotation around the direction of travel, not to climb & descent. You can’t pedal harder to recover from a lean, so this is a different kind of up and down than straight line elevation changes. It makes sense that work is being done somehow if the CoM moves up and down, but the turns come with necessary changes to the higher moments of inertia anyway that flattening the CoM elevation doesn’t change. I’d speculate that the ideal CoM line might not be flat, in the presence of mandatory high speed banked turns; the fastest line and the line minimizing CoM elevation change might be two different lines. Do also keep in mind that on a velodrome track, a higher elevation line is a slightly larger radius turn & longer travel path. It’s also possible that trying to compensate for CoM elevation change adds as much time as it saves.
I reckon it'd be a lot easier to just increase the wall thickness if you want that section of a carbon frame to be stiffer
It can be surprising to people just how tough/strong carbon fibre parts can be - here's Danny MacAskill's destructive testing of some CF wheels: https://www.youtube.com/watch?v=VfjjiHGuHoc
Yeah, they can do it, but they'll be a little heavier than those relatively light rim brake steel bikes linked earlier. (The rotors/calipers, hydraulic, fluid, stronger fork leg required all just add mass.)
I'm also in Seattle! Disc brakes all day.