Questions about purchasing bicycles and parts
I have a giraffe which is a tall unicycle. The sort as below where your pedals drive 1:1 to the wheel below by a conventional chain.
On a giraffe you do a lot of short heavy torque work which loads the chain possibly more than average. Consequently mot serious giraffes and all extra tall ones use TWO chains to share the loads - one on each crank. There are a few downsides to the extra chain but the stretch problem is worse.
My giraffe is a relatively small value-for-money giraffe with a single chain doing the work. Probably the most popular one available.
With this sort of thing the chain is always losing some tightness due to stretch. Unlike what you guys are used to, there is no tensioner to take up slack and, with the need to have it firm at all times in both forward and reverse direction a loose chain makes a difficult skill more so.
If anyone has advice on a chain that is especially good for holding it's length then I am thinking to replace the existing with it. Other than that it does not need any exceptional performance characteristics. Anything that will fit, say, a five speed cluster I would guess.
I doubt you'd get one that'd never stretch Colin.
Maybe a KMC 1/8 jobbie for Fixed gear bikes would last a while but it's only guesswork, mine hasn't passed 100hrs of use yet (just).
Campy chains are supposedly a lot longer lasting than the other popular brands. Might be worth trying.
Contrary to what you might think, the amount of torque a human being can put into a bike chain doesn't have that much to do with how much the chain stretches over time (or wears, to be more accurate, none of the metal bits actually "stretch", the holes in the side plates just get bigger).
I do appreciate that you have responded. However I assure you, the chain does stretch. Specifically the side plates of course.
The cogs (mostly the rear cluster) get scooped out on one side of the tooth. This is in response to the very small stretch. When you replace that chain with a new one that small difference in link length then plays havoc with a cluster that only fits the old one. (The chain keeps on trying to skip one forward on some gears when under load.)
And on a giraffe, with no tension wheel even that miniscule stretch is noticed. Fortunately giraffes all have an easy adjuster to take it up, though it is still better to reduce it, if for no other reason than to reduce the scooping wear on teh cogs. (Though the adverse affects on a giraffe is not so extreme as for a rear cluster as the cog is somewhere between a rear cluster and a chain wheel.
Indeed, it is possible that what I will do instead is get another two chains and simply rotate them so that I can keep the wear and cog matched for the duration of three chains life. ie increase the time before I need to repace the cogs by three. It is what I used to do with my bike.
Last edited by ColinOldnCranky on Tue Mar 19, 2013 11:48 pm, edited 1 time in total.
I would suggest a track chain for single speed use, and I'd reckon a bushed chain should give you slower wear and longer life. No real expert opinion but I'd recommend Izumi or KMC chains - perhaps something like the KMC B1RB 1/8" bushed chain.
Or maybe a chain like the DID track chain.
Chain stretch aka wear definitely does occur (this is a bushless chain). You can see the wear on the pin and on the folded psuedo-bush of the inner side-plates.
It is mostly a function of:
2. Shortage of lube
I'd think on a unicycle dirt would be lower. lube very manageable and mileage low *- all standing you in good stead for better life. I would also recommend steel 1/8" sprocket and chain-ring of course for longer life/reduced wear rate.
* Well, maybe not if the uni is a substitute for your commuter or touring ride
KMC 'fixie' chains are rubbish.
I have a 'Daido NJS D.I.D Racing Chain' on my track/fixed gear bike. 1/8th and absolutely bulletproof.Very little stretch (if any) in 12 months / 2000+ km use. $30 off http://www.tracksupermarket.com (Someone else has already linked to this chain).
They will fit on a 5 speed sprocket, if there are no other sprockets around it!
Just to be clear, most of the attributes of a great chain are not required. AThings like wear and tear etc as a giraffe does little distance. It doesn't even bet very gritty as it is well clear of most of what comes off the ground and not used much in wet weather. So while extra hard bushes and stuff may be nice, for my purposes a k-mart product is fine.
Although I imagine that a superior side plate will be accompanied with superior everything else, I do not need to be fussed with anything except the stretch performance.
btw I do appreciate the advice I am getting. I just thought it needed to be stated clearly the unique attribute that I am chasing.
"Stretch" is wear. So a more durable chain will not "stretch".
The other aspect to apparent stretch is the load distortion of your chain-ring. This does occur with alloy rings under high loads (have a close look at worn chain-ring tooth one day) and the solution to a large degree is steel chain-rings. You can see the sideways distortion or flaring on the teeth here:
Whoa. That is extreme. I have only ever seen it so obvious on the rear rings - they are smaller, the tension is greater for a given torque and the number of teeth taking the load is very much fewer as you step up to a higher gear. But to see it on a large ring where the load is many times less is quite startling.
Methinks the cyclists of today work a lot harder than I ever did.
I have two words for you & they're not Happy Birthday. (Just thought I'd throw that in there cause it's on the front of one of fav t-shirts.)
Actually..........Belt drive !
As the other posters have stated, they don't stretch they wear. What that means is as the chain wears the links get looser resulting in more movement between the links and because of the extra movement the chain get longer.
The track chains have more meaty components and some have bushes as they run on wider spockets and don't need to flex sidewise. The end result is that the chain will take longer to wear
Unicycle. Needs positive chain loading in both directions in order to stay aboard
Such a tensioner would just get pulled out or twisted off by the pressure.
Last edited by il padrone on Wed Mar 20, 2013 11:05 am, edited 1 time in total.
I would be gob smacked if a spring loaded tensioner worked for Colin as he is using the chain on his unicycle & needs to be able to pedal backwards as well as forward
Belt drive could be good for a new unicycle, but I suspect there would be a lot of difficulties retrofitting. My experience with them so far also suggests they are quite sensitive to getting the right tension, so probably not suitable for this unicycle that has no means of adjusting tension.
I was at Rottnest last week and noticed most of the hire bikes are belt drive. They had really loose tension, so I suspect would skip if anyone tried to pedal hard, that would be very unpleasant on a unicycle.
Yes. But the funny thing is you're going to be very unlikely to find a good quality 3/32" bushed chain these days. Most 1/8" chains are bushed however.
As some have indicated, a chain tensioner is not applicable to a unicycle for the reasons that they have given. Need to be able to apply loads both front and rear and with close to zero unloaded travel in either direction. Unfortunate. Life is not so easy for a minority group.
As for stretch, it happens. Opposed to bikes (which always have some slack on their chain) where it unnoticed over the life of the chain, a chained unicycle is uniquely configured to show it's effects. And it manifests itself very quickly with a small but disconcerting angle of slop when idling (peddling back and forth to stay on the same stop), a necessary and constantly used skill. When I first rode I would have to reset the tension regularly to get no slack. But, as I got better I could accommodate it. However it is still something that a unicyclist is better off doing without.
Also, because there are usually some small eccentricities between the two cogs, a chain that is tight throughout the complete rotation will be, in some places in that rotation, excessively tight. This increases the forces that stretch even further.
Ride a giraffe and you will be regularly reminded of it.
After all is said and done I may just initiate a three or four or five chain rotation policy with quick-release links which is a bit of a pain. But at least the rings will not need replacing so soon. Which, frankly, is probably not worth it on a giraffe as unicycles do not run into the high prices that bikes do. And if those chains have less stretch then the life of the rings will be even greater. Hence this thread.
We are actually saying the same thing. It's just definition. The chain does "stretch" in that it gets longer. I was just being pedantic in pointing out that the metal plates do not stretch, the holes in them just get bigger. The amount of elongation, though, has very little to do with the force you put on it because it's a unicycle, it's much more to do with number of cycles round and round. And obviously it's much more noticeable compared with a derailleur equipped bike when there's nothing to tension the chain.
Hope you find a good solution. Seriously, Campy chains are regarded as a lot longer wearing than the other usual suspects (and I don't ride Campy).
Use a 'Ghost Chainring'.
I used one as a chain tensioner with great success on a previous tandem, I have also seen some discussion of using them as a chain tensioner of 'fixies'.
If the chain does lengthen, then you can just use a bigger ring (or two). You can use any old worn out ring as a ghost, since they only make contact for a few teeth at a time on either side, which does not present nearly the same issues as wrapping the chain all the way around, on this basis an LBS is likely to have a selection of worn out rings to choose from.
You'd think that a giraffe could/should be built with an eccentric built in.
I just googled that, funky !!! Curious to know if its a solid long term solution.
Also fits in well with mikebytes comment .
Who is online
Users browsing this forum: MSNbot Media