[HN Gopher] MIT Aluminum Bicycle Project 1974 (2016)
___________________________________________________________________
MIT Aluminum Bicycle Project 1974 (2016)
Author : anschwa
Score : 164 points
Date : 2024-11-27 23:59 UTC (23 hours ago)
(HTM) web link (www.sheldonbrown.com)
(TXT) w3m dump (www.sheldonbrown.com)
| walrus01 wrote:
| The pinnacle of the modern tubular aluminum road bike frame was
| probably reached with the cannondale CAAD8 and CAAD9 frames,
| which could easily be built into UCI-illegal-weight bikes using
| expensive components and wheelsets.
|
| stripped example:
| https://weightweenies.starbike.com/forum/viewtopic.php?t=153...
|
| https://www.reddit.com/r/cannondale/comments/1d9nind/2009_ca...
| A_D_E_P_T wrote:
| > _He ruled out magnesium, which is best per unit weight in
| compressive buckling but is brittle and difficult to extrude._
|
| 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.
| 3eb7988a1663 wrote:
| Can modern material science model this computationally, or does
| everything have to be observed experimentally? This kind of
| insane just-so recipe - are researchers just iterating on
| hundreds of thousands of different alloy compositions and
| production techniques or are there strong theoretical
| principles on which some of this can be derived?
| choilive wrote:
| Its been some time detached from the mat sci folks deeply
| involved in the space but its both. There is a bunch of
| theoretical underpinnings but ultimately a lot of throwing
| darts on the board as well.
| A_D_E_P_T wrote:
| Yeah. It depends a lot on the type of material, too.
| Conventional metal alloys -- like LPSO-Mg -- are the
| toughest to model. Too many variables. Ceramics and
| intermetallics are a lot easier to model in principle, but
| they can have surprising properties on an atomic level, and
| there's really no predictive method for that sort of thing.
| Modeling _does_ get you pretty far with high-entropy alloys
| -- because to a substantial extent their properties hinge
| on how a bunch of different atoms might fit together
| randomly, and that 's something that can be computationally
| predicted. A lot of the recent interest in HEAs is because
| they're relatively easy to model.
| rjsw wrote:
| Computational materials science is a current research area.
| twic wrote:
| There was a magnesium bike frame back in the '90s, made by
| Kirk:
|
| 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.
| A_D_E_P_T wrote:
| > _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.
| UniverseHacker wrote:
| Carbon would cause galvinic corrosion in contact with
| magnesium, and would also visually hide dangerous cracks- I
| don't think a carbon wrapped magnesium bicycle would be
| safe.
| A_D_E_P_T wrote:
| I was just spitballing, but it's possible:
|
| 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.
| UniverseHacker wrote:
| The epoxy barrier might work, but in general encapsulated
| metals are risky because they are impossible to inspect
| for corrosion and cracking so fail without warning, and
| the encapsulation can block surface oxide formation which
| causes crevice corrosion- especially if small amounts of
| salt and water get in there, which they will over time,
| even in epoxy.
|
| 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
| ndsipa_pomu wrote:
| > I'm sure what you are saying could be done- especially
| to basically add stiffness to key regions of a carbon
| racing bicycle
|
| 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
| UniverseHacker wrote:
| Not really- even very thick carbon is quite flexible....
| It works great for applications where you want that like
| bendy sailboat masts and front forks on bikes, but it
| should be cored or replaced with something else if you
| are looking for stiffness
| ndsipa_pomu wrote:
| That doesn't match with my experience. I've got a carbon
| fibre road bike and some parts of the frame are
| remarkably stiff whereas other areas such as the
| handlebars have noticeable flex.
|
| 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
| impossiblefork wrote:
| If one wants to do that kind of thing it might be better
| to fill the CFRP with something else-- stiff foam, balsa
| etc.
| UniverseHacker wrote:
| Yes, that is how carbon fiber racing sailboats are made
| ndsipa_pomu wrote:
| If you're thinking of wrapping a material in carbon fibre,
| why not just use carbon fibre composite in the first place?
| Is magnesium stronger than CF for a given weight?
| A_D_E_P_T wrote:
| Magnesium, especially a casting, can be something like an
| order of magnitude cheaper. Carbon fiber is an
| intrinsically more expensive material, and manufacturing
| complex engineering parts solely with CF, to high quality
| standards, is almost an artisanal process.
| ndsipa_pomu wrote:
| > Magnesium, especially a casting, can be something like
| an order of magnitude cheaper.
|
| 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 PS1000 but I can't recall seeing a magnesium
| framed bike for PS100.
|
| Edit: looking at cheap frames on AliExpress, you're not
| too far off. I saw a magnesium alloy frame for approx
| PS80 and a carbon fibre frame for PS350. Not quite an
| order of magnitude though.
| gravelc wrote:
| I had a Merida Magnesium 909 road bike back in the day. They
| were common in Australia. Was (wrongly) convinced magnesium
| was going to overtake carbon. Never had any issues in 10
| years of ownership and a lot of kms. Welds looked shocking
| and it was very rigid and unforgiving though.
| TomK32 wrote:
| I have a Kirk Revolution frame sitting next to my desk
| waiting to be repainted as I don't like it's turquoise
| colour. Uncracked as many others out there. Looking at it as
| a very first puts the issue about cracking bottom brackets
| into a different light. How many other firsts in any tech do
| fail and show where the next iteration needs to happen? I
| think it's quite sad it didn't see any more iterations.
| giamma wrote:
| Vaast bikes [0] makes magnesium bikes today, I own one (A/1
| gravel) and it's a very pleasant ride.
|
| [0] https://www.vaastbikes.com/
| genter wrote:
| How would you fabricate a frame from extruded tubing? Welding
| would destroy the grain structure.
| A_D_E_P_T wrote:
| That looks like it's an active research problem: https://www.
| sciencedirect.com/science/article/pii/S266633092...
|
| At a glance, though, the problem doesn't seem insurmountable.
| FSW appears to work.
| le-mark wrote:
| Brazing has a long tradition in building bicycle frames.
| Scoundreller wrote:
| And lugs
| etrautmann wrote:
| Aren't truck chassis increasingly made with epoxy or other
| adhesive bonds?
| alanbernstein wrote:
| I learned about this company's magnesium frames recently:
| https://www.vaastbikes.com/company/
| metal_am wrote:
| Interesting. I haven't heard of them. Joining would still be a
| problem for a bike frame. Any idea on how well they work with
| other severe plastic deformation processes?
| A_D_E_P_T wrote:
| They appear to benefit from ECAP, if that's what you mean.
| For e.g.: https://www.sciencedirect.com/science/article/abs/p
| ii/S09215...
|
| 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.
| rich_sasha wrote:
| I'm looking forward to a sleugh of articles telling me carbon
| frames have a really harsh ride quality and lack a certain "je
| ne said quoi" compared to magnesium frames.
| philjohn wrote:
| Quite - the grass is always greener.
|
| 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.
| rfmoz wrote:
| Magnesium is common in suspension forks lower legs.
| m463 wrote:
| I thought stiff was a problem with aluminum - stronger is
| better but is stiffer better?
|
| That said, I wonder if there is a way to make frames more
| comfortable without having the flex absorb pedaling energy.
| ndsipa_pomu wrote:
| I don't believe that the frame material makes much difference
| to comfort. The part that can deflect/absorb bumps and
| vibration the best is the tyre. So the answer to your
| question is bigger tyres at lower pressures.
| david-gpu wrote:
| Yeah, whenever I hear people talk of the properties of bike
| frame materials it reminds me of audiophiles: plenty of
| strong opinions backed by a remarkable absence of data.
|
| 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.
|
| [0] https://www.youtube.com/watch?v=u1e3g8uqrJU
|
| [1] https://www.youtube.com/watch?v=rAkDaHlZQow
| mikeryan wrote:
| How's it compare to carbon which is the most common high end,
| lightweight bike material these days?
| A_D_E_P_T wrote:
| As of right now, nobody makes LPSO alloys in commercial
| quantities. Fuji Light Metals has a pilot plant that does
| small-scale production of extruded strips and plates, but
| their customers are all researchers and R&D labs.
|
| 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.
| leoh wrote:
| Favorite road bike I've ever owned was the aluminum Klein Quantum
| Race designed by Greg Klein.
| lbourdages wrote:
| Klein bikes of that era had the best paint jobs I have ever
| seen. I was way too young to even know about these bikes back
| then, which is a shame, as they are pretty much at the very top
| of what constitutes bike porn for me.
| leoh wrote:
| Yeah they were good
|
| Don't need a bike manufacturer to do that for you though
| mtillman wrote:
| I still own a Klein Performance '81 and an Adept Comp that has
| its own amazing story. Love Klein bikes. In fact, I kind of
| expected this article to be about Klein since it also came from
| MIT in 1975.
|
| https://en.wikipedia.org/wiki/Klein_Bicycle_Corporation
| loeg wrote:
| It's interesting that trackies in the 70s were trying to reduce
| weight that much. I don't think it's perceived as especially
| advantageous these days. The high-ish end track bike I'm
| assembling now will be a little over 8 kg (almost 18 lb). We also
| race much bigger gears (typically 95-110 gear inches in mass
| start racing, bigger for sprinting) than mentioned in the article
| (72 gear inches). The position that is considered aerodynamic is
| also much different -- there is much less focus on getting that
| insanely low, and instead the focus is on being narrow and
| getting the forearms parallel with the ground.
| Gualdrapo wrote:
| Not sure if you know about Merckx's bike for his hour record -
| they did many interesting modifications to it aiming to reduce
| its weight
| loeg wrote:
| Yeah, Sheldon mentions it in this article. I don't think
| those mods helped. Weight has no impact on sustained speed.
| kevin_thibedeau wrote:
| You slow down incrementally between every power stroke.
| sudosysgen wrote:
| A heavier bike would slow down less. At the end of the
| day the energy is lost to friction.
| xpe wrote:
| > Weight has no impact on sustained speed.
|
| 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.
| loeg wrote:
| You're not going up and down the track during an hour
| record. Just doing laps at the bottom (zero elevation
| change). Track surfaces aim to be very smooth in general.
| xpe wrote:
| > You're not going up and down the track during an hour
| record.
|
| 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.)
| dahart wrote:
| It's an interesting question & thought experiment! To the
| degree that it even matters compared to all the other
| bigger forces, I would put money on riders naturally
| adjusting for CoM changes by riding slightly higher
| during the turns; I'd bet they already take approximately
| the ideal racing line you suggest. I just watched a
| couple of velodrome rides on YouTube, and it does seem
| like riders are often closer to the red line during the
| turn and the black line during the straightaway,
| statistically, but it's noisy and would need to be
| measured.
|
| 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.
| matsemann wrote:
| Wouldn't you mainly get the energy back? Like, you use
| some going up the wall, and then gain it all back going
| lower.
| ndsipa_pomu wrote:
| Surface irregularities (bumpiness) are the reason why
| lower pressure tyres are now preferred on bikes. The idea
| is that a very rigid tyre will deflect the bike and rider
| up and down which wastes some energy/momentum as well as
| fatiguing the rider, whereas a lower pressure tyre can
| absorb those irregularities and "roll-over" the bumps.
| This is part of the reason that recent thinking has moved
| from skinny high pressure tyres, to wider medium pressure
| tyres. (Wider tyres will tend to roll quicker than a thin
| tyre at the same pressure - something to do with how the
| contact patch deforms the rubber).
|
| However, cycling tracks are designed to be very smooth
| which is why high pressure tyres are still used there.
| xpe wrote:
| Any bump results in some energy transfer. In the case of
| small enough bumps and tires at ideal pressures, most
| energy is returned, but not all. These losses accumulate.
| The question is "how much does it add up to?" This is why
| I recommend using the phrase "negligible effect" instead
| of "no effect".
| hackingonempty wrote:
| Rolling resistance increases linearly with weight, so it
| does have some impact.
| loeg wrote:
| Ok. _Almost_ no impact. Worth keeping in mind we 're
| talking about a system weight of like 180 lb vs at most
| 185 lb here (Merckx was ~163 lb), for a relative
| difference of up to 3%.
| hackingonempty wrote:
| It largely is the streetlight effect: we all have or can easily
| get tools to measure weight, we all have significant experience
| with weight, etc... Aerodynamics are much more difficult,
| especially in the 1970s where you can't just do some CFD
| simulations on your computer. There also weren't cheap solid
| state strain gauges to outfit wind tunnels or the bike
| drivetrain. Since only tiny aero gains are available without
| banned aerodynamic devices, there isn't much optimization you
| can do and need sensitive tools.
| cenamus wrote:
| Maybe that's just mostly due to the UCI regulations? No point
| to develop a fully fitted 5kg bike if it has to be 7kg anyways
| I suppose
| ndsipa_pomu wrote:
| Unless you can hide away a 2kg battery/motor combo. (Just
| joking really as they do scan for hidden motors nowadays)
| bluGill wrote:
| If you have a 5kg bike you can put the extra 2kgwhere you
| want it. this can make a difference in a race.
| jdietrich wrote:
| Most competition bikes weigh significantly more than the
| 6.8kg limit, because weight just doesn't matter very much. A
| lot of state-of-the-art road and track bikes weigh around
| 8kg.
|
| 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.
| cenamus wrote:
| So it only matters on basically every classic non time
| trial race?
| matsemann wrote:
| With the speeds the pro's climb these mountains, aero is
| still a big deal. For you and me slogging along it's
| almost all weight that matters. But not for the pros.
| david-gpu wrote:
| Keep in mind that arodynamic drag is not a function of
| ground speed, but airspeed. If you ride slowly in a
| relatively windy place, your airspeed can easily be twice
| of your ground speed.
|
| That said, given how many of us are overweight, worrying
| about a couple of kilos on the bike is funny talk anyway.
| Tostino wrote:
| Did you ignore the part where GP was talking about the
| tradeoffs made, and how aero improvements are almost
| always worth the extra weight?
|
| It's about optimizing the whole system, not just one part
| of it.
| loeg wrote:
| If it mattered, though, every track bike would be exactly 6.8
| kg -- and they aren't.
| eftpotrm wrote:
| I remember hearing Callum Skinner talk about the British
| track team preparing for the Olympics, and how the biggest
| problem they had was strength - I remember the number 2400
| for their best track sprinters, I forget if that was in watts
| or newtons but either way it's a massive force and they were
| snapping frames.
|
| 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.
| fnord77 wrote:
| I'm convinced titanium is a pretty optimal bike material. I hate
| aluminum frames, too stiff, some amount of flex makes a bike so
| much nicer. Hate carbon, too. Steel is nice.
|
| 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.
| xpe wrote:
| Titanium frames have a devoted fan base. Personally, I tried to
| notice the difference back when I did road racing but didn't.
| Maybe I didn't want to: Ti ain't cheap.
| __mharrison__ wrote:
| What is cheap these days?
| loeg wrote:
| Low quality steel is very cheap but also really heavy. You
| can get a whole crappy bike for a couple hundred bucks.
| Higher end steel isn't as cheap but is still relatively
| heavy (compared to aluminum or carbon). You can get this
| kind of bike in the $1000-2000 price range (e.g. Surly).
| Aluminum bikes tend to be inexpensive, but also not the
| lightest. These can also be priced at $1000-2000
| (Specialized, Trek, Giant, ...). Carbon comes in a range of
| prices with various tradeoffs. You can get very budget
| carbon frames at like $1500 (Winspace) or whole bikes at
| like $3000 (Giant) (maybe $2000 in non-major brands, very
| discounted during current market conditions).
|
| 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.)
| insane_dreamer wrote:
| Prices shot up during the pandemic and never really went
| back down. You're lucky to find a good carbon bike for
| under $4K these days where you used to be able to find
| them for $2K.
| loeg wrote:
| Everyone's in oversupply now, inventory is listed at
| steep discounts to 2022-2023 prices.
|
| 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
| grogenaut wrote:
| Check these out
| https://www.rodbikes.com/profiles/profiles.php?tag=ultra-
| lig... steel bikes ~13.5 lbs.
| loeg wrote:
| Yeah. Very expensive and with significant compromises.
| grogenaut wrote:
| could you expand? I get the expensive part, but they're
| also hand built customs so...
| tpm wrote:
| For about the last year and a half you can usually get a
| carbon road bike from major brands with basic components
| starting from 2000 euro (right now I see Bianchi, BMC,
| Cannondale, Cube, Giant, Specialized listed around that
| price).
| loeg wrote:
| Yeah, I think in particular prices have come down
| dramatically in the past 3-6 months.
|
| 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.)
| toast0 wrote:
| Quality used bikes are remarkably affordable. I'm a sucker
| for 80s road bikes; $200 gets you something decent, bring
| it to a shop for a tune up and probably new brakes.
|
| 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.
| tokai wrote:
| Custom ti frames are cheaper than the high end carbon frames
| nowadays.
| gield wrote:
| You wouldn't feel the stiffness of an aluminium frame as much
| on a track. On the road, stiffness is a more important factor
| for rider comfort.
| ndsipa_pomu wrote:
| > I'm convinced titanium is a pretty optimal bike material.
|
| 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.
| danburbridge wrote:
| Ti is difficult to weld - there are a lot of cracked Ti frames
| out there - often at the welds :( A shame as they (can) look
| great.
| prmoustache wrote:
| Frame flex of ti bikes is pure fantasy/placebo (at least on the
| vertical plane) on traditionnaly shaped frames.
|
| You would need enough force for the tires, wheels, saddle,
| handlebar, stem and seatposts to break/explose before the
| double triangle start flexing.
| xnx wrote:
| R.I.P. Sheldon Brown. I'm glad his pages still exist both as
| useful resource and as a time capsule of what the best of the old
| web looked like: useful, content rich, no ads, fast loading,
| stable urls.
| webnrrd2k wrote:
| I was at another OG-style web page [1] today, and thought the
| same thing. I found a Badger airbrush, a 155 Anthem [2], that I
| completely forget I had.
|
| [1] https://sites.google.com/site/donsairbrushtips/home
|
| [2] https://sites.google.com/site/donsairbrushtips/home
| rob74 wrote:
| No ads? I assume you have an adblocker installed? Without one,
| you do see some ads, although by far not so obnoxious as on
| other sites...
| Kuinox wrote:
| There is an aliexpress ad on top of the page.
| mikeryan wrote:
| I got down to the bit about Sheldon Brown being Harriet's
| husband and was "wait _that_ Sheldon Brown?"
|
| That was when I realized what site I was on.
| xpe wrote:
| > Use larger diameter tubular components - Strength goes up as
| the cube of the diameter so unless there are geometric
| constraints, use larger diameter tubes with thinner walls to get
| a lighter structure with increased strength and stiffness.
|
| 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.
| donavanm wrote:
| If youre thinking modern carbon frames most of that is actually
| driven by design for manufacturability, not
| strength/weight/performance optimizations per se. Off the top
| of my head:
|
| 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.
| ginko wrote:
| My main gripe with those large diameter tube frames is that
| they're just ugly.
| fiatpandas wrote:
| Two things jumped out at me: the simple/non-adjustable saddle
| support, and the absolutely slammed bars affixed just above the
| fork. Was that normal for track bars at the time?
| loeg wrote:
| Yeah, both are relatively insane choices by modern lights. You
| see some other track bikes of that era with fork-mounted
| handlebars (it's not unique) but I believe conventional stem +
| bars were more popular.
| fiatpandas wrote:
| Tbh I love the simplicity of the hard coded saddle post +
| support. Both being made out of the same tube size.
| mollusk wrote:
| Check out the Soviet Takhion [1] track bike for a similar
| handlebar setup.
|
| 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...
| fiatpandas wrote:
| Great references! Thank you.
| car wrote:
| A modern alternative are bamboo frames, e.g. https://my-boo.de
| ndsipa_pomu wrote:
| Whilst bamboo is an interesting "green" material, it doesn't
| really compare well to a carbon fibre frame. Modern thinking is
| that the frame weight is secondary to aerodynamics and one of
| the advantages of CF is that the frame "tubes" can be shaped
| specifically to help with that. Of course, the main aerodynamic
| advantage to be gained is from the human sat on top of the
| bike.
| brudgers wrote:
| Every time I've visited a Sheldon Brown page, I've gone down a
| rabbit hole.
|
| This time it was "Sheldon Brown's personal bicycles"
| https://sheldonbrown.com/org/bicycle.html
|
| That's the essence of a great website.
| ndsipa_pomu wrote:
| I've only just found out that he suffered from Multiple
| Sclerosis: https://www.sheldonbrown.com/org/ms.html
| rfmoz wrote:
| Gary Fisher has an insteresting paper too about alu frames:
|
| https://web.archive.org/web/20061103174315/http://www.kleinj...
| fiftyacorn wrote:
| For me the biggest innovation in bicycles was Graeme Obree -
|
| 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.
| yapyap wrote:
| nice story but the ads are awfully annoying, and b4 u suggest an
| adblocker, I'm on a phone.
| Scoundreller wrote:
| I suggest an adblocker for your phone
| ndsipa_pomu wrote:
| Various VPN services provide ad blocking and a phone app e.g.
| Mullvad
| Scoundreller wrote:
| It's not perfect, but carefully choosing DNS
| resolvers/profiles can get you a lot of the way there.
|
| 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.
| prmoustache wrote:
| I was browsing this page on my smartphone in an airport with
| the ublock origin extension blocking the ads...not sure what
| you are talking about with that weak phone excuse.
| trhway wrote:
| aluminum is nice, yet once in a blue moon you get something like
| this year an aluminum hiking pole broke when i lost my balance on
| a slippery slope and put a lot of weight on the pole and falling
| i almost got skewered by it's broken off jagged lower piece. I
| really want steel poles now, yet can't find them to the point of
| pondering DYI-ing from some Home Depot steel tubing.
| ndsipa_pomu wrote:
| That's a problem with aluminium - no fatigue limit. This means
| that cyclic loads on an aluminium frame (or pole) will
| eventually cause it to fail. Steel does have a fatigue limit
| such that cyclic loads below that threshold won't cause
| eventual failure.
|
| There's some good info on bike frame materials here:
| https://bike.bikegremlin.com/11144/bicycle-frame-materials-e...
| mtillman wrote:
| Wasn't this solved by Klein?
| ndsipa_pomu wrote:
| No
| prmoustache wrote:
| It is only really an issue with aluminium forks and non
| traditionnal construction.
|
| 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.
| eigart wrote:
| Just an anecdote thats been horrifying me for the last week since
| Klein is mentioned.
|
| 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.
| briansm wrote:
| I find the obsession minimizing bicycle weight funny. It's not
| the bicycle weight that matters, it's the combined weight of
| bicycle and rider that counts.
|
| 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.
| tomaskafka wrote:
| That's what I tell myself when picking the bike - just get a
| competent basic $700-ish bike, and if you want it 2 kg lighter,
| lose those 2 kg instead of paying thousands.
| briansm wrote:
| In evolutionary terms, being taller, fatter and more muscular
| is advantageous, but in practical terms it's just a lot of
| extra weight to drag around for a lifetime, along with all
| the extra calories of energy needed to do so.
| magic_smoke_ee wrote:
| Yep. That's what I keep telling myself. ;) In the end,
| those will all kill me sooner because they're each opposed
| to longevity in a safe environment.
| wink wrote:
| It's not bike weight per se, but there's also a somewhat direct
| link between weight and component quality and age. I.e. no one
| really tests a 20y old bike with current top-end components, no
| one really puts 10y old groupsets on a 2024 frame.
|
| 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.
| ndsipa_pomu wrote:
| Weight isn't that important for bike racing unless you're
| specifically doing hill climbs. Aerodynamics will make more of
| a difference, so there might be some advantage in having a bit
| of belly fat to enable a smooth airflow.
|
| Also, heavier riders are generally faster downhill as they have
| a greater terminal velocity.
| magic_smoke_ee wrote:
| > 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.
| magic_smoke_ee wrote:
| Yep. A heavier bicycle is cheaper, less fragile, and also
| increases the workout effect. As long as a bicycle isn't 20 kg
| / 50 lbs, what is the real problem? I believe the real goal for
| lightness is luxury conspicuous consumption to maximize cost
| using exotic materials like beryllium.
| matsemann wrote:
| In Tyler Hamilton's book he describes going out for hour long
| rides, then taking some sleeping pills and going to bed, all
| without eating, just to shed weight before the tour. Just
| crazy.
| benj111 wrote:
| What was the patent for?
|
| 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
| prmoustache wrote:
| I also rode an aluminium frame my granddad owned that was from
| the 1950's, with weird 700A wheels by today's standards.
| mjs wrote:
| > She did spend another year in France, but not until 1988/1989
| with her husband, _Sheldon Brown_ ...
|
| It's his wife! Harriet is Sheldon's wife!
| magic_smoke_ee wrote:
| I was going to say it looked like a Cannondale TT. It was too
| stiff, unstable, difficult to control, and rode poorly compared
| to heavier steel frames. Steel is heavier but at least you'll
| still have teeth left after a ride on a road that isn't perfect
| like a freshly-asphalted bike path.
| btbuildem wrote:
| With all the mods ("hardcoded" seat, no stem, custom shafts and
| bearings) It's funny he decided to keep the toe clips -- would've
| easily shaved a few ounces there!
___________________________________________________________________
(page generated 2024-11-28 23:01 UTC)