Derailing the Carbon Drivetrain
Aug 28th 2007News & Rant & Media & The Industry
Sometimes, I find myself faced with crises of purpose. What am I doing here? Why can’t I figure out what I want to do with my life? Will I ever find something that satisfies me? It’s enough to really get me down sometimes. It’s a good thing I’ve got the boneheadedness of the bicycle industry to set me right again.
I suppose it was only a matter of time until some high-watt decided to apply the word “carbon” to drivetrains, and it’s a good thing the folks at Carbon Drive Systems did just that - otherwise I would have mistaken their “innovation” for a glorified fan belt. Anyway, it’s about time someone beefed up those flimsy polyurethane straps - they last a mere 60,000 miles while running in my car. With the glut of other unsuccessful belt-drive bicycles out there, it’s clear to see the addition of carbon fiber must do something to make this product newsworthy - perhaps by making it laterally stiff yet vertically compliant!
And really, isn’t a revamping of the single-speed drivetrain long overdue? I mean, it’s just so hard to maintain that single cog, single chain ring and chain. Sure, when it gives you 20, or even 30 gearing options, a chain drive is worth the painstaking process of applying a coat of lubricant, turning the crank a couple times, then wiping it clean. But when you’ve only got one gear, the reliability, adaptability and near-perfect efficiency of a chain drive simply can’t make up for the extra weight and apparent mud shedding issues.
One of the nice things about attending a college with an engineering school is that you get to dissuade people from pursuing a lot of really silly ideas. Occasionally, you you get to see something cool (though that’s not really how bike balance works) but for the most part, you just shoot down bad ideas. Overlooking than the general sensation of pedaling through sand, the belt-driven protoype I rode slipped under power at low revs, and derailed entirely at the cog around 100 RPM. Good thing none of these will ever be an issue on a singlespeed MTB…
6 Comments »
spokejunky on 29 Aug 2007 at 6:28 pm #
Yeah, but imagine this carbon drivetrain mounted to a NuVinci:
http://www.cyclingnews.com/tech.php?id=/photos/2007/tech/news/01-31/NuVinci_cutaway
hub, while riding my white carbon commuter, listening to my mp3 shorts:
http://www.pearlizumi.com/product.php?mode=view&product_id=758231
sloshing down my Starbucks with my coffee mug:
http://www.somafab.com/morningrush.html
all the while emailing my friends on my bike mounted blackberry:
http://www.ram-mount.com/index_files/ramb149zaq2.jpg
Kevin on 30 Aug 2007 at 11:12 am #
^^
Sweeeeeet… Now THAT’S how to ride a bike…
gtveloce on 31 Aug 2007 at 8:46 pm #
Setting aside the carbon marketing spin, I’ve no problem with people investigating alternative drive chain methods. Although as Phil has pointed out this is hardly new. The Johns Hopkins research (original source article here with more pics) doesn’t compare belts with chains, and I’m no engineer, but however elegant chains may be they are made from many, many more moving parts than a belt. All of which pose frictional, wear and lubrication challenges.
From a practical point of view removing one row of cam-drive chain from a car engine will release 3-5 additional horsepower and allow the engine to rev more freely. Replacing the chain with a belt appears to also release a few extra horses and will definitely reduce maintenance. The chain in my old Alfa is a wonderful, noisy and fiddly thing to adjust, but the belts in modern cars need no adjustment or lubrication, are quieter, last longer and are replaced ‘just in case’. They also retain cam timing spec far longer, which keeps the engine within exhaust pollution standards.
But there’s little in common between a car revving to 8,000 rpm and delivering umpteen kW and a bike rider spinning at 100 rpm. Other than the inevitable chain stretch, the need for lubrication, wear and quite frequent replacement. A belt drive may or may not be more efficient but it will require less maintenance, is simpler and will probably last forever.
Combined with hub gears or some other gearing method belts may well have a big future on bikes. Or maybe shaft drive will deliver even greater benefits? Mind you, the UCI will probably ban it anyway.
gtveloce on 31 Aug 2007 at 8:50 pm #
Of course it wasn’t Phil who said that, I’m just losing my mind and confusing my bike bloggers. But I still think belts are interesting ;-)
frank scurlock on 10 Sep 2007 at 12:04 am #
Would dig passing on some “real” information about the belt system. Geez, rough crowd in here.
Frank Scurlock
Carbon Drive Systems
frank@spotbikes.com
Jim on 05 Sep 2008 at 10:06 am #
Re gtveloce - most engine manufacturers have now gone back to chain drive for cams, mainly for reliability, they seldom snap, belts do this frequently, do not need changing and frictional losses are minimal - certainly not in the 3-5 bhp range you quote. (I worked for Lancia, Lotus and Vauxhall)
The Chain cam 2.0 Fords are significantly more powerful than the previous cam belted versions despite near similar architecture, and chains do not suffer the slap that belts can when decelerating rapidly, and in my experience hold cam timing far more accurately than belts, you seldom see chains jump a tooth or two, yet this is common with cam belts. Yes maintaining tension can be fiddly, my duratec V6 needs this nearly every 60,000 miles…but this is far cheaper and quicker than replacing a belt.
Drive belts don’t work that well on motorbikes, and yes I have ridden both and had a chain snap on a motorbike. For a cycle you would have to make it split somehow to get it inside the frame, or design a completely new drive train outside of the frame. A chain has had 100 years development and refinement, are cheap, and adjusting and lubing must take at least 20 minutes a month…