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MIT Aluminum Bicycle Project 1974 (2016)

sheldonbrown.com

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Re: MIT Aluminum Bicycle Project 1974 (2016)

#41

Post by gravelc »

twic wrote: post #7
A_D_E_P_T wrote: post #3

> 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 stif…

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.

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.

Re: MIT Aluminum Bicycle Project 1974 (2016)

#42

Post by loeg »

insane_dreamer wrote: post #36
loeg wrote: post #30

Earlier quoted context omitted.

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, ...…

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.

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

Re: MIT Aluminum Bicycle Project 1974 (2016)

#43

Post by donavanm »

xpe wrote: post #23

> 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-me…

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.

Re: MIT Aluminum Bicycle Project 1974 (2016)

#44

Post by grogenaut »

loeg wrote: post #30
__mharrison__ wrote: post #25

Earlier quoted context omitted.

What is cheap these days?

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, ...…

Check these out https://www.rodbikes.com/profiles/profiles.php?tag=ultra-lig... steel bikes ~13.5 lbs.

Re: MIT Aluminum Bicycle Project 1974 (2016)

#45

Post by tpm »

loeg wrote: post #30
__mharrison__ wrote: post #25

Earlier quoted context omitted.

What is cheap these days?

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, ...…

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).

Re: MIT Aluminum Bicycle Project 1974 (2016)

#46

Post by mollusk »

fiatpandas wrote: post #32

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?

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...

Re: MIT Aluminum Bicycle Project 1974 (2016)

#47

Post by TomK32 »

twic wrote: post #7
A_D_E_P_T wrote: post #3

> 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 stif…

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.

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.

Re: MIT Aluminum Bicycle Project 1974 (2016)

#48

Post by rich_sasha »

A_D_E_P_T wrote: post #3

> 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 stif…

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.

Re: MIT Aluminum Bicycle Project 1974 (2016)

#50

Post by ndsipa_pomu »

xpe wrote: post #22
loeg wrote: post #12

Earlier quoted context omitted.

Yeah, Sheldon mentions it in this article. I don't think those mods helped. Weight has no impact on sustained speed.

> 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.

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.

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