Belt drive fixed

ok, i get this now. after some googling which is didn't do before.

Although a cyclist can exert more torque/force (pulling on the chain) momentarily, it's not constant and not at high revs, whereas on a bike it's constant (especially at high speed) and at considerably higher REV's.

If a bicycle chain were used on a motorbike it probably would work, but would wear out very quickly since there is much less material bearing the load and no o-rings to stop the oil dissipating causing more friction. Also the cogs and sprocket, being smaller would wear out quickly.

So the reason is more about longevity of the chain rather than the actual strength, where a bicycle chain is strong enough (surprisingly) just not robust enough for any appreciable length of time if it were used on a motorbike .

Talk about going off topic. We are now drifting into the arena of the pedant.

The clue with torque is in the lb/ft measurement. A bike crank is over 6 inches (half a foot) so the lb per foot number is high with just body weight alone. The way a car/motorbike engine is designed means that the leverage on the crankshaft is tiny meaning torque is low except on large engines (which motorbikes don't have)

It's because a cyclist can develop a lot more torque than a motorbike engine.

Now considering that a Ducati 996 motorbike produces 93Nm at its maximum.
Now a 70kg cyclist standing on the cranks will be developing 9.8x70x(17/100) 116.62Nm

Because the sprockets they are applying this force to are almost equal radius (a 996 comes with 15 tooth sprocket as standard) it means the cyclist will be creating more chain tension.

isn't it 93nm at the flywheel and therefore CONSIDERABLY more after it's been shot through the gearbox? Reducing the silly 9000 or so RPM to something more usable, and more torque-y

isn't it 93nm at the flywheel and therefore CONSIDERABLY more after it's been shot through the gearbox? Reducing the silly 9000 or so RPM to something more usable, and more torque-y

No it's from the drive sprocket.
You actually don't want that much talk on a motorbike for a very good reason, once the torque exceeds the limit of what can be transferred the bike will automatically do a wheelie, meaning that it's actually almost impossible to snap a motorbike drive belt or chain.

a 996 can do 0-60mph in 3 seconds. Lets presume it does it with linear acceleration.
60mph = 27m/s
acceleration during 0-60 run = 9 m/s/s

f=m x a
weight of 996 = 200kg
f = 200x9
f= 1800n

The 996 runs on 190/50/17 which have an overall diameter of around 26" or 0.66m

to provide 1800n of force 0.33m from the moment of rotation, the rear axle/sprocket has a torque value of 600n/m

I love how ridiculous this thread now is.

So, are we all agreed? The carbon belt doesn't stretch and is a nice addition to the choices available to cyclists.

I love how ridiculous this thread now is.

So, are we all agreed? The carbon belt doesn't stretch and is a nice addition to the choices available to cyclists.

I'll agree to that. I didn't even read how this motorbike chat started, the figures just didn't sit right with me.

this bloke makes (or supplys) a really neat liitle coupler to allow the belt through the frame...

http://www.shandcycles.com/2010/02/23/carbondrive-beltdrives/

Torque is only half the equation, the other half is RPM. On a bicycle we're talking around 100 RPM (YMMV) and on a motorcycle we're talking 3,500 > 5,500 RPM on some racing machines.

I don't know much about torque or tension but I think you missed a step with the above..

Surely the high RPM stops once the driveshaft or whatever it is motorbikes have meets the gearbox. The chain will only go round as fast as the wheels, which means what, at 60kph you're talking 1000 metres/min with a tyre diameter of what, about 60cm? That's about 4m circumference which means that the rear wheel's doing something of the order of 250RPM. Unless there's gearing between the rear sprocket and the wheel that's the speed the chain's going. A smaller sprocket at the front would obviously be spinning faster, let's say 4:1 which seems a bit extreme..

So that's 1000 RPM at 60kph, 2000 RPM at 120kph.

Definitely an order of magnitude faster than most people would pedal, I'd wager.

I love how ridiculous this thread now is.

So, are we all agreed? The carbon belt doesn't stretch, is a nice addition to the choices available to cyclists, and Smallfurry is more powerful than a 900cc Harley.

I can live with that.

A few points, now that I have some proper off-rod miles on the belt.

Having rode through some deep swamps last night, I can confirm that the system stands up to dirt. It felt as smooth on the way home as it did on the way out.

Apon arriving home I just sprayed the bike down with the garden hose. The shite on the drive train just droped off.

I had some big tumbles, yet the belt stayed perfectly tensioned throughout.

The system is uber smooth. Thought TBH, you just forget about it on the trail (which is how I like my components).

Definitely an order of magnitude faster than most people would pedal, I'd wager.
Speak for yourself! ;)

this bloke makes (or supplys) a really neat liitle coupler to allow the belt through the frame...

http://www.shandcycles.com/2010/02/23/carbondrive-beltdrives/

he doesn't supply, he just fits them to your frame - think he gets them from fixie inc.

just had my Surly Cross Check altered by him - not cheap at £80 plus sprockets/belt

he doesn't supply, he just fits them to your frame - think he gets them from fixie inc.

just had my Surly Cross Check altered by him - not cheap at £80 plus sprockets/belt

That's pretty damn cheap all in.

Speak for yourself! ;)

Video k pls thx!

That's pretty damn cheap all in.

sorry, it was £80 for the chop and another £180 for belt/sprockets.

did a good job though

£80 is still pretty cheap to make your bike belt compatiable.

£80 is still pretty cheap to make your bike belt compatiable.

It is very resonable, but its worth restating that the belt-ring is very thick and will quite likely rub the chainstay on a typical track frame.

You can 'crimp' the chainstay though.

Yep, sure can't beat a good crimp

Crimpity crimpity now now
Crimpity crimpity ask me how
Crimpity crimpity humble pie
Crimpity crimpity ping dong
paping ping tong
Crimpity crimpity ping pong

sugarman
light sauce
why did you come to me
put me in a coma
woke up in the future
robot man can you help me find my wayyyyyyyyyyyyyyyyyy
bom bom bom bom bom bom
i cant understand the things you say

cute mouse
i took you from the underground
& brought you home

i put you in my jacket pocket
and took you to the meeting
i put you in my jacket pocket
and took you to the meeting

put you in my jacket pocket X3
put you in my jacket

jean claude jackette
with his jacket on
jean claude jackette
with his jacket off
jacket on
jacket off
jacket on
jacket off

oooh oooh ooh i did a twisty
oooh ooh oooh a tiny twisty

Crimpity crimpity now now
Crimpity crimpity ask me how
Crimpity crimpity out my way
Crimpity crimpity you will pay

bing bong bing bing bong

Crimpity crimpity fuck you

:d

I always like the 'Bouncey bouncey' crimp myself.

[ame="http://www.youtube.com/watch?v=CCR_Z7Fsa3k"]YouTube-
Mighty Boosh Crimps - The Complete Collection[/ame]

Bouncey Bouncey is my all time favourite crimp, really addicting.

I've a overwelming urge to seek out the nearest bouncy castle for a hop about.

Only £80 for fixie inc couplers? wow.

phew... glad that torque/motorcycle bit seems to have petered out.

im putting together a fixed gear belt drive bike pretty soon here. i didnt like any of the hub options out there for using a single speed one, so i decided to make my own rear cog. anyways, ive got a solid model i can upload to the site if anyone would like, so they can make their own too (or have someone do it for them). it mounts on a six bolt IS disk brake flange.

** note: requires a CNC