geekonabike (Addict)  |
| Sat Aug 27, 2011 11:07 am |
| I'm not sure it is either, so I used "might." |
| Wes- wrote: |
| A chain with the proper amount of slack will not have extra internal resistance due to roll-binding. A looser chain will ride up the sprocket, putting more force on a smaller area, increasing wear; this phenomenon is well documented in the literature.
So, a looser chain does more work, the power must come from somewhere -- the fuel tank. By what mechanism does your hypothesis allow for a tight (but in spec) chain to do more work than a loose one? I am fairly certain that any gearing advantages achieved by the chain riding up in the sprocket will not result in measurable changes in fuel economy, based on observed changes with significantly larger sprockets. Wes |
I should have hedged twice I suppose, as in "it might have loosened up (stretched), maybe giving less resistance."
I think there are a lot of factors, but at the extreme, certainly a tighter chain would increase "force normal" on the usual surfaces that are interacting, even if the lube is (for the most part) in between. I'm thinking about anything that rolls, including the countershaft in its bearings and the wheel with its bearings and axle. However except at damaging extremes it might be miniscule compared to the force these things will encounter anyways to actually propel the bike. There is loss in the final drive chain/sprockets setup, though less than with a belt or shaft so it's still popular (and cheaper).
If someone wanted to be absolutely scientific, he/she would have to put the same load on the rear tire on, say, a dyno, and run the bike at the same speed but with the chain at different resting tensions, and look at fuel consumption. One could also look at how hot the chain gets under the two circumstances as a proxy to fuel consumption, since that is wasted energy, though that might not be the complete picture.
I seem to recall reading about a much older model bike that didn't enclose the chain because it heated up too much, and the calculation of how many watts was consumed by just the chain heating was remarkable. That model was old enough that it probably didn't use o-ring chains, but I'm not sure. (I get too many motorcycle magazines. Hmmm...is that possible?)
Certainly increased wear you cited is evidence of lost energy, unless you're really talking about concentrated wear instead of more distributed wear, but I think what you refer to is likely an increased in total wear, whether concentrated or not, so I'll concede that a loose chain is a bad thing, perhaps even a net energy drain. I think you'd also see increased wear with a too-tight chain, but the original poster's chain was within specs. The belt on my HD Sportster is incredibly tight, but I get to save some money on lube I guess.
--Mike D.
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I'm not sure that's a valid hypothesis — Wes-, Sat Aug 27, 2011 9:31 am -
I'm not sure it is either, so I used "might." — geekonabike, Sat Aug 27, 2011 11:07 am