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yeehaamcgee
Joined: 07 May 2007
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 Posted Sat Nov 7, 2009 11:22 am |
How does that apply to belt drives? WHY would we want belt drive?
(and I still think you're making this a fit for purpose argument, whereas, ironically, belt drives are less fit for the purpose of bicycle transmission than chains)
Mae'n enw i wedi ei grafu, hefo hoelan wedi rhydu, ar y lechan las
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Northwind
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yeehaamcgee
Joined: 07 May 2007
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Posted Sat Nov 7, 2009 6:57 pm |
right, how about this, what are the metrics by which you can measure the performance of a chain or belt drive?
Weight, strength, durability, ease of repair, ease of fitting?
For virtually all those, a chain is better than a belt. Feel free to add your own points if you want.
(I'm enjoying this discussion, by the way - it's rare that one goes on this long here without turning into a slanging match  )
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Northwind
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Posted Sat Nov 7, 2009 7:24 pm |
Yeah, me too.
<edit for different info I just found, looks like my first post was wrong>
OK, weight should come out in favour of the belt. Info here:
http://www.gates.com/ptdesign/trek.html
http://www.bikeradar.com/news/article/interbike-gates-expanding-belt-drive-reach-23455
80 grams for the carbon-reinforced belt apparently. I was told 240g but that appears to be wrong.
Also, the sprockets can be different, you don't have metal-on-metal wear so an all-alloy design is quite practical (though the drive face is bigger). I'd expect an aluminium belt sprocket to come in less than a steel chainring without the lifespan sacrifice of an alloy chainring. Plastic's even a possibility, some motorbike belt conversions use delrin sprockets on an alloy carrier.
Durability and lifespan- belt should win hands down, if done right, though the question of what mud will do to them isn't answered yet. Same goes for maintenance, belts don't need lubed and the cleaning should be simple, though we'll need to see how that really works out. Gates say they expect twice the lifespan of a well maintained chain.
Ease of repair- chain wins by a mile (not to mention ease of replacability, ie, no need to stock 50 different lengths of belt as chains can be shortened). But belt should need repairing much less often. So, not sure, we'd need to see rela world performance here to give any sort of sensible answer.
Likewise ease of fitment, chains are always going to be easier but they'll need fitted more often. Looking at the Dirstrict, the fitting's actually going to be pretty simple, you break the frame by removing the dropout I think, so 2 bolts. Not quite as fast as a chain but not a chore either.
Another metric is flexibility, where chains just plain win, as a result of being able to run traditional gearing not rohloffs etc. And I guess efficiency, but these belts should be comparable to chains.
We still do it because we're forever chasing what we've already found |
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yeehaamcgee
Joined: 07 May 2007
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Posted Sun Nov 8, 2009 5:31 pm |
hmm. interesting.
I'm not sold on the wear lifespan of the belts though. If you have two materials, of differing hardnesses (is that a word?) being forced against each other, then the softer one WILL wear out. So, either the belt wears out, or the "sprocket" does.
Biggest issue of all as far as I'm concerned is the requirement to completely overhaul suspension designs.
See, the trouble is, we can't just have the chain's drive wheel being in line with the swingarm axis - or you'd get incredible amounts of pedal induced bobbing - although suspension feedback into the cranks would be minimal.
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Northwind
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Posted Sun Nov 8, 2009 8:12 pm |
| yeehaamcgee wrote: | Biggest issue of all as far as I'm concerned is the requirement to completely overhaul suspension designs.
See, the trouble is, we can't just have the chain's drive wheel being in line with the swingarm axis - or you'd get incredible amounts of pedal induced bobbing - although suspension feedback into the cranks would be minimal. |
Yup. Or y'all could buy proper manly hardtails.
We still do it because we're forever chasing what we've already found |
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yeehaamcgee
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supersonicLives Here
Joined: 25 Nov 2005
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Posted Sun Nov 8, 2009 8:38 pm |
| yeehaamcgee wrote: | hmm. interesting.
I'm not sold on the wear lifespan of the belts though. If you have two materials, of differing hardnesses (is that a word?) being forced against each other, then the softer one WILL wear out. So, either the belt wears out, or the "sprocket" does.
Biggest issue of all as far as I'm concerned is the requirement to completely overhaul suspension designs.
See, the trouble is, we can't just have the chain's drive wheel being in line with the swingarm axis - or you'd get incredible amounts of pedal induced bobbing - although suspension feedback into the cranks would be minimal. |
Like the old cove G spot. And to an extent, most speshes and Konas...
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yeehaamcgee
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Posted Sun Nov 8, 2009 9:52 pm |
Which part of it is like the old cove G-spot? suspension feedback, pedal bob, or pivoting round the BB shell?
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Northwind
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supersonicLives Here
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Posted Sun Nov 8, 2009 10:15 pm |
| yeehaamcgee wrote: | | Which part of it is like the old cove G-spot? suspension feedback, pedal bob, or pivoting round the BB shell? |
Pivot around the BB shell (concentric pivot to bb axle).
The Kona was the same.
No pedal feedback, but minimal anti squat which counters the suspension sag or bobbing from accelerating.
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yeehaamcgee
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Posted Sun Nov 8, 2009 10:22 pm |
None of the konas or speccys pivot around the BB though. They might be close but It would still be enough of a difference to mean a slack belt.
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supersonicLives Here
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Posted Sun Nov 8, 2009 10:27 pm |
It would, but I was pertaining more to the antisquat charecteristics with those two specific bikes.
There was a Kona with a BB pivot for singlespeeders, and Scwhinns first rocket too (though used an extra link)
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yeehaamcgee
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Posted Sun Nov 8, 2009 10:30 pm |
| Northwind wrote: | | Are there any current suspension designs with the BB on the swingarm rather than on the main frame? |
Not that I know of these days, apart from possibbly some cheap catalogue bikes.
They used to refer to them as an Unified Rear Triangle design (URT)
They had some major drawbacks, not least of which is that your whole body becomes part of the unsprung weight.
Also, the suspension action really only worked if you were sat down. When standing up, you already had your weight on the swingarm, so the suspension action was effectively locked out.
If you were sat down, it felt really strange, because your feet would move back and forth relative to your riding position - in fact it felt a little as though your frame had snapped!
The advantage was that you had no chain growth, so you got no pedal feedback, and minimal pedal-induced bobbing.
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yeehaamcgee
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supersonicLives Here
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yeehaamcgee
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supersonicLives Here
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ride_whenever
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Posted Sun Nov 8, 2009 10:43 pm |
the old g-spot was bb concentric 4 bar (or faux bar cannot remember)
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. But there are some advantages or potential advantages (since there's not really enough real world applications out there to say how it'll really work) as discussed in this thread. And since the big disadvantage is gearing, once you take that away (ie, you are a weirdy beardy singlespeeder 