http://www.youtube.com/watch?v=Rlse9h74Q8Y&NR=1
Cheap chain tensioner for you fixie lot!
That's not true is it? Depends on the dropout doesn't it?Fixie's don't have chain tensioners!!
But how would a setup like the one demonstrated in the video be detrimental to a fixie setup (if there's inadequate dropout for chain tension adjustment)?
Err, now having actually watched the You tube video, yes I suppose you could use an old chainring as a form of chain tensioner, but in order to adjust the tensioner, you'd need horizontal dropouts anyway. In rare fortuitous circumstances the floating ring might fit on non adjustable (vertical) dropouts but the coincidence of this would be about the same as a chain length being perfect over a given drive chainring and rear cog on a non adjustable dropout.
What I'm saying is that with vertical dropouts, you invarabily need an adjustable chain tensioner, this floating ring is not adjustable.
What I'm saying is that with vertical dropouts, you invarabily need an adjustable chain tensioner, this floating ring is not adjustable.
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shrubb face
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Considering that the floating ring is not fixed to any spider or device which is designed to give it strength, I would not be suprised if the ring simply crumbled the moment you put any real power down.
Yes, I understand the mechanics, but was just pushing the boundaries here.Err, now having actually watched the You tube video, yes I suppose you could use an old chainring as a form of chain tensioner, but in order to adjust the tensioner, you'd need horizontal dropouts anyway. In rare fortuitous circumstances the floating ring might fit on non adjustable (vertical) dropouts but the coincidence of this would be about the same as a chain length being perfect over a given drive chainring and rear cog on a non adjustable dropout.
What I'm saying is that with vertical dropouts, you invarabily need an adjustable chain tensioner, this floating ring is not adjustable.
I guess the point of this chainring chain tensioner is that it can be adjusted through the use of different sized chainring to achieve greater or lesser chain displacement.
I have no idea how much force the ring can take under power but it shouldn't be that weak, should it? A bit of rough road may bounce it out if the tension wasn't quite right... Nice bit of lateral thinking by whoever came up with the idea.
You obviously also need to have the right tools at the same time... Chainring bolt tool and chain breaker.If one broke off one's rear derallier & didn't have a chain breaker & it was too far to walk home I wonder if you could take off your big ring from the front & insert it as shown to tension a chain enough?
Under your scenario and by simple geometry, the position where one insert the chainring would also have an effect on how much additional chain it takes up. The closer it's placed to the rear hub, the greater the take-up. Ummm...
I can see no theoretical reason why you couldn't use a ghost ring on a fixie to give adequate tension. Even though there is no specific adjustment mechanism (except changing the size of the ring) the fact is that the ring will position itself at the point along the chainline where all of the forces are equal. So... the ghost ring will stop at the point on the chainline where the chain has the lowest tension. A self-adjusting mechanism if you like...
Now the problem is that you would need a pretty big ghost ring to give adequate tension. It would need to be something like 25% bigger than the drive chainring. The larger the ghost ring you use, the more space it needs. So... unless you are going to use a really small drive chainring like the one in the video, you are probably going to have the ghost ring rubbing against the chainstay all the time. Even if the ghost ring doesn't pop out, it's going to be noisy.
Even if you use a ghost ring which is small enough not to strike the chainstay in smooth pedalling, accelerating and slowing cause the tension in the top half of the chain to change. This doesn't affect the fore-aft position of the ghost ring, but it will momentarily affect the vertical positioning of the ring. (Remember the ring always self-adjusts.) You can see the ghost ring "bouncing" in the video, even when there are only small changes in chain velocity. Even a small ghost ring will probably strike the chainstay often.
I'd say it's a good emergency fix, but not one you'd want to use regularly.
Now the problem is that you would need a pretty big ghost ring to give adequate tension. It would need to be something like 25% bigger than the drive chainring. The larger the ghost ring you use, the more space it needs. So... unless you are going to use a really small drive chainring like the one in the video, you are probably going to have the ghost ring rubbing against the chainstay all the time. Even if the ghost ring doesn't pop out, it's going to be noisy.
Even if you use a ghost ring which is small enough not to strike the chainstay in smooth pedalling, accelerating and slowing cause the tension in the top half of the chain to change. This doesn't affect the fore-aft position of the ghost ring, but it will momentarily affect the vertical positioning of the ring. (Remember the ring always self-adjusts.) You can see the ghost ring "bouncing" in the video, even when there are only small changes in chain velocity. Even a small ghost ring will probably strike the chainstay often.
I'd say it's a good emergency fix, but not one you'd want to use regularly.
If you think a bit deeper about it, the position of the 'ghost ring' won't move around. It'll just stay at the same spot you put it at rather than moving to the point of least tension. The two-way running chain will ensure it won't move away from its initial position. So under this scenario, you can indeed alter the chain displacement by moving it closer and further away from the rear axle. Of course, the stupid drive side chain stay will get in the way at some point.Even though there is no specific adjustment mechanism (except changing the size of the ring) the fact is that the ring will position itself at the point along the chainline where all of the forces are equal. So... the ghost ring will stop at the point on the chainline where the chain has the lowest tension. A self-adjusting mechanism if you like...
Weiyun, you are correct. I realised that after I'd written it. The ghost chain doesn't move along the chain horizontally. It moves vertically as the relative tensions vary. I altered one reference to this, without realising I had made 2 references, and you've caught me out!
Still, even though it can't move horizontally, we all agree that the vertical movement, plus the fact that chainstays aren't really long enough to accommodate 3 sets of gears turning without touching means trouble sooner or later.
Still, even though it can't move horizontally, we all agree that the vertical movement, plus the fact that chainstays aren't really long enough to accommodate 3 sets of gears turning without touching means trouble sooner or later.
Having recently had an accident where my single speed setup (on vertical dropouts) decided that it didn't like the single gear on the back and would rather mesh with nothing. I am not sure that I would ever like to ride a bike with this sort of tensioner, even as a temporary measure.
I can see something going wrong in a horrible way, when you would want it to do so the least. Probably when it is under load.
I can see merit in the idea, and it may work in an emergency, but it would have to be where I have to ride the bike, and I need to ride it as a single speed.
One problem with trying to take off your own chain ring to do this, is that your chain ring bolts would then be too long for a single chain ring.
James
I can see something going wrong in a horrible way, when you would want it to do so the least. Probably when it is under load.
I can see merit in the idea, and it may work in an emergency, but it would have to be where I have to ride the bike, and I need to ride it as a single speed.
One problem with trying to take off your own chain ring to do this, is that your chain ring bolts would then be too long for a single chain ring.
James
I agree. Vertical movements on rough roads may bump the ghost ring out of its position, so not a dependable system without some additional features.Still, even though it can't move horizontally, we all agree that the vertical movement, plus the fact that chainstays aren't really long enough to accommodate 3 sets of gears turning without touching means trouble sooner or later.
a much simpler solution for those without track type dropouts is to use a half chain link.
These are available for both 3/32 and 1/8 chain.
Not to easy to find in oz but they are easy to obtain from the US via mail order. There is a picture on sheldon's page here http://sheldonbrown.com/fixed-conversion.html
note the note on not using chain tensioners on a fixed gear bike.
These are available for both 3/32 and 1/8 chain.
Not to easy to find in oz but they are easy to obtain from the US via mail order. There is a picture on sheldon's page here http://sheldonbrown.com/fixed-conversion.html
note the note on not using chain tensioners on a fixed gear bike.
Note what Sheldon actually said... "You CanNOT use any sort of pulley type chain tensioner on a fixed gear bike!"note the note on not using chain tensioners on a fixed gear bike.
Just no pulley type chain tensioner, not a generalization of all chain tensioners.
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