http://www.theengineer.co.uk/1003600.article?cmpid=TE01&cmptype=newsletter

Discuss.

I don't think I really understand how that works. I'm sure it's dead clever and all, but it doesn't look terribly durable or idiot-proof. But then, neither do derailleurs. 🙂

’While every other part of the modern mountain bike has changed to meet the modern demands of downhill racing, the gear system has barely changed for more than 100 years'

I see. I thought the modern rear mech was only about 70 years old?

/pedantry

Andy

Looks like the four segments of chainring move out to three set radii so the effective chainring size still meshes with the pitch of the chain. Not sure I believe all the claims about extended chain life etc 😯

it's a neat idea but I don't see a problem with pedalling for 2 seconds down a hill. As well, given the ring is going to be square, with round corners (when in 'big ring' mode) won't it be a bit biopacey? but twice as bad?

If each segment moved out by a DIFFERENT amount, so it looked like those hideous 'power-optimised' ovalish road road rings that Wiggo et al are so fond of I can see people falling over themselves to buy it on the back of some "85% of 72 MTBers agree it gave me more power" made up statistic 😉

Nice idea, whether it works or not…

yeah it's a neat idea, would like to see it in action
Seems like he just missed the boat on triple front ratios though, so 2008!

The mechanism must be a bit cleverer than it looks – I can't immediately see how you can 'change gear' with chain on. If to try and move all four quadrants out at once, surely it would try and stretch the chain between adjoining segments?

err – if the size of the chainring changes, won't you still need a wotsit to pickup the slackness you get when the chainring is small? Won't that basically be a similar weight to a derailleur?

won't you still need a wotsit to pickup the slackness you get when the chainring is small?

Yeah, a rear mech 😉

By my reckoning it'd need to shift fixed amounts so the gaps between the chainring quarters was a multiple of 1/2" but given that it's a clever idea though it'll take some clever design to make it practical.

Does it not just expand one at a time when not in contact with the chain?

…won the Xerox Innovation Award for designing a safer system for gear changing downhill, a well-known problem among cyclists.

I'd better be more careful changing gear downhill then. I never realised it was such a well-known problem. 😀

Does it not just expand one at a time when not in contact with the chain?

Could be – that would be the 'easiest' way of doing it.

actually, I don't see it working

for the chain to go from a segment in position '2' to position '3' its going to have to go left one more 'bit' and up one more 'bit' – unless you have this diagonal an exact number of links (as well as having 2-to-2 being an exact number of links and 3-to-3) it's either going to cause the chain to stretch, or cause slack which means your whole pedaling force will go through the first 2 teeth on the first bit of the 'out' segment until you've wound the cranks round. so you have to pedal without any force going through the chain. so its about the same as today's setup

I think the first variable size chain ring for bicycles were designed roughly 100 years ago and pre-date the derailleur. I pretty certain there's one in "Bicycles & Tricycles: A Classic Treatise on Their Design and Construction By Archibald Sharp" – a great read BTW! Originally published in 1896 and great at demonstrate how little bicycle technology has actually changed. There's also been numerous attempts in the intervening years. They've all been gash too 🙂

I expect there's a clever thing with springs and levers that allows the gear changing.

One would hope this wouldn't get an award if it didn't work at all.

yep nothing new under the sun

I can't find any publish patent application yet so only time will tell if it is new and gets a patent, or even if it works.

Celever idea and so thoughful of Brunel University to take out a patent in their name.

so thoughful of Brunel University to take out a patent in their name.

I am fairly sure that is standard practise for undergrad and postgrad students

I thought I'd stick Brunel University in the European patent office search, but the results are just taking the piss

I thought it might be. Does that mean any revenue goes to the uni rather than the inventor?

Does that mean any revenue goes to the uni rather than the inventor

If you play by the rules, yes – if you want to take a good idea further the idea is you form a spin-out micro company so the Uni isn't liable when it goes tits-up, but then you get to grow it as big or as small as you like.

Don't know how they can call it an invention.

The first I know of was the Linley & Biggs Expanding Chainwheel in the 1890s, and there was one floating around in the mid 1930s.

The Cambiogear is the most recent version of this invention. Here's a pic of mine:

It's an idea that will only work properly if you enclose it in an oilbath chaincase, and if you are going to do that there are other alternative gear systems that would be more compact.

You can still patent something that's already been invented cant you? I thought it was a race to the patent office not a race to invent something. (I'm thinking specialised/horst link)

Can't see how it's going to work under load but I'm no engineer*

*massive understatement

the segment with no chain on it presumably pushed out to make a gap between it an the next segment equal to an interger number of links, the number of links between each segment in its in and out position must be an interger, which is probably why it onluy has 3 possible combinations rahter than the 7+ needed to give a good spread of gears.

Good idea, possily a more novel aproach than the hammershmit, but looks like it could get busted fiarly easily (the hammersmit is nice and small and contained, this looks like its got more exposed buits thana dereilieur.

No, you can't patent something that's already been invented. It must be new and contain an 'inventive' step. Plus it must be makeable. (No perpetual motion machines.)
But as no one can find a patent or patent application yet it may get rejected at the examination stage.

Falling off is my main problem when going downhill, not changing gears…

I've never had a problem changing gears down hill. Still. When at "big ring" position it's going to have linear section of chain between "corners" so the extensions to each diam must be slightly out of kilter with if it were to match the equiv diam ring. It's going to have notable wear problems (the chain now has fewer teeth to hook up on, so higher load per tooth) Each tooth section needs to be particularly stiff as they're now on their own, rather than part of a ring, and at the end of the day it still needs a tensioner. The shift mechanism is going to have to involve a slip ring -type system and as mentioned, the only quarter to move can be the unloaded one, so needs to be timed nicely to coincide with rearward pointing.

Too much faffing for my liking, but a nice design problem. Remember product design awards don't necessarily mean the product has to be functional or anything more than marginally tested (I've been involved with a few and seen some of the stuff that gets marked highly!).

HAMMERSCHMIDT

That is all.

Hammerschmidt looks like one heavy clunky bit of kit, and at £500, christ on a bike.

It might not need a tensioner if only one of the quarters of the ring is lifed at TDC to provide the gear ratio and then it retracts as the next section is lifted and takes over the drive duty.
If the four sections are independently sprung and are lifted into position by a moveable roller on the backplate, the springs will tension the chain automatically round to BDC past the 3 O'clock position.
I've been toying with a similar idea based on variomatic transmission. But that would need a tensioner so I didn't follow up on it because current mechs are cheaper.
It's a very good idea if works in the manner i'm picturing.

To make it as light as a derailleur setup, it's going to have to be made out of some very exotic materials or be flimsy.

It looks like it would be a lot less tolerant of mud than a derailleur too.