Ericoschmitt

First question: why are all bike chain links 1 inch long? (I mean, an inner plus an outer links, so you join both 1/2 inch to make a "complete" one). This seems to be a very arbitrary measure that some gentleman chose in late XIX century for his first chaindrive bike experiment.... and it stayed until today.

Now, have you ever wondered what could be the benefits of shorter links? For example, if all links were exactly half the lenght, and all teeth half the size proportionally, you could have "half step" cogs, which would be very useful for time trial fine tuning. And also, the higher you go on a normal cassete, the bigger the gap. If you change from a 21 to 20 cog, thats about 5%. But from 12 to 11 it would be 9%, almost double.

With shorter links, the chain would also get thinner, so you could also make cassetes with more gears, and smoother shifting due to smaller gap. But that doesnt necessarely means a more fragile chain: shimano dura ace chains have tapered link walls with a hole cut in the middle to dim weight. With a thinner chain you just dont do the hole and keep the same resistance.

It doesn't have to be half the lenght though. 30% shorter could give us 13speed cassetes with the same 10 speed hub most of us have on road bikes already.

One big con is that it wouldnt be compatible with anything else we have, unless you keep chain width and numer of gears. Basically you need new cogs, cranks, chain, shifters and derraileurs.
But if people spend the money to upgrade their bikes to Di2, why not? I'd buy it.

OBS: I know of the existence of the NuVinci hub, the problem is it creates considerable drag and is heavy as it is today.

FBinNY 

There are physical constraints to how small a chain can be scaled. Minimum diameters of the pins, the needed radius of the plates at the pin hole, the thickness allowed for the bushing and roller all come into play, the sprocket teeth, etc. So there's very little down side room for a chain system with the required strength.

However, there is a bit of wiggle room and some decades back Shimano introduced 1cm pitch track chains, citing the very advantage you mentioned, more sprocket sizes and closer steps in possible gearing. Here's a link to some info about it, and you'll find plenty more if you look.

CliffordK

There are certainly chains with shorter pitch.

This is ANSI standard chains.

https://www.renoldjeffrey.com/nmsrunt...=1006&sID=2750

25 (1/4") pitch is rated with a working load of 140 lbs, probably too light.
35 (0.375) pitch has a working load of 480 lbs, and may be acceptable.

So, maybe 3/8" pitch, but stock ANSI chains may not be suitable for bikes. Wider, pins sticking out, etc.

Friction is likely where the links bend, and interface with the chainrings, so more links might mean more friction...

FBinNY 

480#s is far too skimpy for bicycle chain. Figuring a typical 2:1 ratio between pedal and chainring circles, a 240# rider will snap a chain just by standing on the pedals. If he used a 24t granny with a 7:2 leverage ratio just about anybody could break a 480# rated chain.

There's a reason why the DIN spec for bicycle drive chain is something on the order of 900kgf. And that reason is why there's limited potential to scale down.

Marcus_Ti

Having more pivots per unit length, means more wear points per unit length. Which for derailleur chains means they probably don't last as long.

OTOH for a fixed or SS bike that wouldn't matter

HillRider

I think that will be too weak also. As an example lets assume:

1. A 170mm (6.7") crank arm,
2. A 24T granny ring with a standard .5" pitch whose radius is (24*.5/3.14159)/2 = 1.9"
3. A 200 pound rider putting his full weight on the crankarm at the 3:00 o'clock position while just starting from rest so the bike is momentarily stationary.

So the initial tension in the top run of the chain would be 200*6.7/1.9 = 705 pounds

That is well over the acceptable load for a 3/8" chain. And, since there are longer crank arms, smaller granny chainrings and heavier riders available, I don't think this example is unrealistic.

CliffordK

I presume that 1/2" chains are a pretty good compromise for bikes too, with a range of sizes from about 9T to 40T on the rear, and 20T to about 100T on the front.

With a smaller pitch, one either gets more teeth or smaller sprockets. But, it is really not needed.

fietsbob

Old skip link was a long then a shorter link .


Now bicycle chains are 1/2 inch, but 1 inner link needs an outer link

to connect to the next inner link so that is 2 pins.. 2 1/2"

there are bent side plate half chain links , even whole chains made up of those ..


Shimano tried a 10mm link chain drivetrain for Track , But UCI over ruled it.

I have seen gas motor bodge kits using a different Chain pitch ..

Gates belts, I think, are 11mm pitch.



'/,

AlexCyclistRoch

There is a myriad of standards from the 19th century that we just accept today, because changing them would just be too difficult. Electricity is produced in 3 phase AC, 60Hz (North America, 50 Hz elsewhere) mostly because that's what Nicola Tesla wanted. We drive on the right most places because that's what Napolean wanted. No real logic, that's just how it happened.....

cny-bikeman

I do not see a full application of logic in your statement above. The smaller pitch cogs at the high end of the gear ratios would of course be smaller in diameter - too small to be installed on a standard cassette body, so one would be required to up the tooth count on them. But to maintain the same ratios at the high end the chainrings would then have to have a proportionately larger tooth count as well. To have a wide range cassette would then need to have larger low-gear cogs, which would require a wider range derailleur (with of course different pulleys.

I also don't see any reason that the chain would be thinner at a smaller pitch. Finally, on a multispeed bike there would be serious concerns with the chain having enough flexibility to handle the deflections necessary for shifting and cross-chain engagement (which is likely why 10mm pitch chains were introduced for track usage but not for derailleur bikes).

HillRider

Of course these standards are arbitrary but necessary or there would be chaos.

AC (Westinghouse and Tesla) current won out over DC (Thomas Edison's baby) for many, many practical reasons, not the least of which it's ability to be transmitted long distances with minimal losses. As to the voltage and frequency we use, do you know of any better combination that has advantages?

As to driving on the right side of the road, it's not universal as anyone who has been to the UK, Japan or a few other countries can testify. However, in a given location, it's essential we all follow the arbitrary but accepted standard.

sch

Bicycle chains and socket wrench squares are among the very few INCH designated standards world wide. Socket wrenches are universally
1/4, 3/8 etc in size. Ditto bike chains are 1/2" pitch world wide.

HillRider

There are quite a few other bicycle items actually made in inch sizes but usually advertised in metric units.

Derailleur clamps are 1-1/8" (28.6 mm), 1-1/4" (31.8 mm) and 1-3/8" (34.9 mm).

Fork steerers are made in 1" and 1-1/8" OD as are the matching headsets and stems.

Handle bar centers and stem clamps are made in 1" (25.4 mm) or 1-1/8" (31.8 mm) with 26 mm being a true metric size.

Steel frame tubing was originally made in all inch size diameters but tubing is all over the place for size and shape these days.

Anyway, the inch isn't dead yet, even world wide.

fietsbob

Britain, (etc.) and Japan , the pass on the left is historical because that was the predominate sword hand.


back to the topic,
You can use a non standard chain if you are able to make your own sprockets for your bicycle..

Ericoschmitt

Thank everyone for the answers! The 10mm dura ace was about what I was thinking.

Just to make my idea clear, its not about keeping the tooth count and scaling things down, as the 10mm Dura ace did. Its about keeping the same size and weight, and getting more teeth.

In a 1/2 size scale, to keep math simple, instead of 53/39 x 11-25 standard, you would get a 106/78 x 22-50, keeping all cogs at the same diameter. Smallest possible would still be 22 and fit normal hubs.

The advantage of this imaginary example would be having the in-betweens (for time trials for example) where you you dont need the lighter cogs. Some time trialists use 12-21 cassetes and still never need anything bigger than the 16. They could very well be racing on 5 speed bikes OR get the "half size system" with a 24-33 count, which gives the same ratius as a 12-16.5 with lots of fine-tuning.

Chain would be thinner if you scale down everything proportionally, but as mentioned in other answers, would be weaker. I don't see why it would be less flexible in this case. But the point is, how many broken chains have you seen during pro-tour sprints? Would they snap the chains if you got it 20% weaker? But then, if you make it 20% narrower, you wouldn't need to drill holes in the chain walls as you get in Dura-Ace chains, just make it without holes and you might get the same strenght and weight?.. and 20% narower means 2 more gears.

A possible workaround on chain weakness is making both the cogs and cranks bigger. 20% weaker chains with 20% bigger cranks and cogs gives you the same gearing and stresses the chain the same. And gets you 12 or 13 speed cassetes.

Or maybe they made it for track bikes because it was cheaper to produce.

Today it would be possible for these electronic derraileurs to be able to handle different speed cassetes after setting up the config electronically. They just have to change the step size, the engine just follows the computer... So you wouldnt need to change the shifters if such a system existed, just cranks cassete and chain.

But after all, I'm no engineer. Maybe some is reading and gives it a thought. Who knows how the future of cycling will be... But I bet on internal hubs and axis or belt drive will be the norm someday!