Belt Drives Pwn You All

inzane · *by **inzane** on Fri 5/Sep/08 12:03pm*

jeremyb wrote:
Robbie wrote: All the normal places: at the contact point with the cogs, and within the belt itself as it flexes.

More contact area = less friction I would've thought, plus no rollers in the chain to rotate and wear!

What sort of engineer are you?? More contact area is always going to equal more friction!!

Also bending a flexible material is likely to need more energy than rotating a link about a pivot, especially if the pivot is oiled.

What about the energy wasted by stretching the belt when power is being applied to the rear wheel... there is likely to be more energy wasted in a belt than in a chain!

radical_edward · *by **radical_edward** on Fri 5/Sep/08 12:16pm*

Belt drives are one of those technologies where theory and reality diverge.

Yes, in theory they are marginally more efficient than chain drives, and they are most certainly lighter.

But to stop them slipping, you must keep them tensioned tightly. There is a tiny window of optimum tension. Above that, you increase axle friction and belt wear.

If they were so efficient, where are they in velodrome racing? Where are they in motorcycle racing?

jeremyb · *by **jeremyb** on Fri 5/Sep/08 12:17pm*

inzane wrote:
jeremyb wrote:
Robbie wrote: All the normal places: at the contact point with the cogs, and within the belt itself as it flexes.

More contact area = less friction I would've thought, plus no rollers in the chain to rotate and wear!

What sort of engineer are you?? More contact area is always going to equal more friction!!

Also bending a flexible material is likely to need more energy than rotating a link about a pivot, especially if the pivot is oiled.

What about the energy wasted by stretching the belt when power is being applied to the rear wheel... there is likely to be more energy wasted in a belt than in a chain!

Software engineer

The belts don't really stretch like a chain and you don't have all those links tugging back and forth against each other and grinding paste from dirt and sand messing them up, you can't keep a bike chain lubed properly and working efficiently in those conditions!

jeremyb · *by **jeremyb** on Fri 5/Sep/08 12:19pm*

radical_edward wrote:
If they were so efficient, where are they in velodrome racing? Where are they in motorcycle racing?

I assume for cycling they have to run a chain and sprockets, would be interesting to do a belt or shaft drive fixie :thumbsup:

ratrod · *by **ratrod** on Fri 5/Sep/08 12:25pm*

Engine manufacturers are went from timing chains to belts and now back to chains, well some of them anyway.
The belts don't stretch, but they do snap. A chain will last much longer than a belt before snapping.

istepinyards · *by **istepinyards** on Fri 5/Sep/08 12:26pm*

jeremyb wrote:Harley and Buell have been using drive belts for years and you never hear about them breaking

Both bikes are ridden by raving homosexuals. Now Ducati and Moto Guzzi there is 2 bikes that make even a nun moist

bikeys · *by **bikeys** on Fri 5/Sep/08 12:59pm*

Punter wrote: Buells have been gay since the came out and so is that

I worked at the Waterford factory for 2yrs because of this bike I attached. I have personally met Eric & I can confirm he is very happy since Harley bought 51% of his company that he started in a shed in Wisconsin. In my old age I try to stay reserved about passing judgemment till I actually meet the designer personally so I can form my own opinion based on my own facts. It just makes for honest journalism, you no what I mean?
Gotta admit that coment made me piss myself.

big_d · *by **big_d** on Fri 5/Sep/08 1:08pm*

ratrod wrote: Engine manufacturers are went from timing chains to belts and now back to chains, well some of them anyway.
The belts don't stretch, but they do snap. A chain will last much longer than a belt before snapping.

I learnt that one the had way â€“ Cambelt snapped at 8000rpm :crazy:

The head did not look pretty after that :blush:

Colin · *by **Colin** on Fri 5/Sep/08 1:24pm*

Orange have been showing a belt drive single speed for the last 6 - 12 months.

From a belt drive manufacturer pushing their product

Due to their high efficiency ratings (as high as 99% on a continuous basis in a Poly Chain GT2 drive system), synchronous belt drives can also lower energy costs compared with roller chain drives, which typically operate at 91-94% efficiency, or V-belt drives, which when properly tensioned, operate at 93-95% efficiency.

What I don't understand is why Moto GP bikes aren't accessing all that free horsepower.

If true, going from 94 - 91% of power reaching the back axle to 99 - ?? % must be a worthwhile gain

pb · *by pb on Fri 5/Sep/08 1:34pm*

Colin wrote: Orange have been showing a belt drive single speed for the last 6 - 12 months.

From a belt drive manufacturer pushing their product
Due to their high efficiency ratings (as high as 99% on a continuous basis in a Poly Chain GT2 drive system), synchronous belt drives can also lower energy costs compared with roller chain drives, which typically operate at 91-94% efficiency, or V-belt drives, which when properly tensioned, operate at 93-95% efficiency.

What I don't understand is why Moto GP bikes aren't accessing all that free horsepower.

If true, going from 94 - 91% of power reaching the back axle to 99 - ?? % must be a worthwhile gain

More efficient yes, but can the belt withstand the large tension involved? Efficiency drops to 0% when the belt breaks.

radical_edward · *by **radical_edward** on Fri 5/Sep/08 1:40pm*

Colin wrote:What I don't understand is why Moto GP bikes aren't accessing all that free horsepower.

If true, going from 94 - 91% of power reaching the back axle to 99 - ?? % must be a worthwhile gain

My guess is that dealing with a changing 'chain length' requires keeping the belt tensioned within a much much narrower window than chains. Belt slippage or disintegration is not good for the race plan.

My experience with belt drives is restoring old turntables. Even a 3mm difference in a ~280mm 'rubber band' results in slippage or the motor running slow due to lateral pressure on the motor spindle. And this is not a high torque situation. Sure, bikes used toothed belts, but the torque is considerably higher than an early 80s Acoustic Research.

istepinyards · *by **istepinyards** on Fri 5/Sep/08 1:48pm*

bikeys wrote:
Punter wrote: Buells have been gay since the came out and so is that

I worked at the Waterford factory for 2yrs because of this bike I attached. I have personally met Eric & I can confirm he is very happy since Harley bought 51% of his company that he started in a shed in Wisconsin. In my old age I try to stay reserved about passing judgemment till I actually meet the designer personally so I can form my own opinion based on my own facts. It just makes for honest journalism, you no what I mean?
Gotta admit that coment made me piss myself.

I have an opinion regardless of meeting the designer hence it being called MY opinion.
I am not shy about giving it either

I personally dislike Buell and Harley because they are shite in my books but I'm no journalist so therefore no need to be worried about advertising space through my thoughts.
Please refer to my Ducati and Moto Guzzi comments for another of my apparently "ill informed" opinion.
I am also a massive fan of Tim Tams but have yet to meet Mr or Mrs Arnott.

znomit · *by **znomit** on Fri 5/Sep/08 2:11pm*

inzane wrote:
jeremyb wrote:
More contact area = less friction I would've thought, plus no rollers in the chain to rotate and wear!

What sort of engineer are you?? More contact area is always going to equal more friction!!

Also bending a flexible material is likely to need more energy than rotating a link about a pivot, especially if the pivot is oiled.

What about the energy wasted by stretching the belt when power is being applied to the rear wheel... there is likely to be more energy wasted in a belt than in a chain!

errr, no engineer but I did do some mechanics in physicist school. Friction isn't a function of area, but if you spread the friction over a larger area you get less heat hence big tyres for performance.
No belts on GP bikes? Harleys have them because they are low power bikes. Check out the width of the belts, for GP bikes they would need to be huge.

Regading guzzis, the only thing that stopped me trading my 1100 guzzi on a firebolt was the numerous stories of belts snapping. Seems a sharp stone was all it took. The newer ones have guards and not such an issue. The new motor/styling on the 1125 is fugly.

Tristan · *by **Tristan** on Fri 5/Sep/08 2:11pm*

inzane wrote:
jeremyb wrote:
Robbie wrote: All the normal places: at the contact point with the cogs, and within the belt itself as it flexes.

More contact area = less friction I would've thought, plus no rollers in the chain to rotate and wear!

What sort of engineer are you?? More contact area is always going to equal more friction!!

Contact area has nothing to do with frictional force. Frictional force depends only on the coefficient of friction (basically how slippery the two objects are) and the normal (perpendicular to direction of motion) force pushing the two objects together.

philstar · *by **philstar** on Fri 5/Sep/08 2:19pm*

inzane wrote:
jeremyb wrote:
Robbie wrote: All the normal places: at the contact point with the cogs, and within the belt itself as it flexes.

More contact area = less friction I would've thought, plus no rollers in the chain to rotate and wear!

What sort of engineer are you?? More contact area is always going to equal more friction!!

friction is independent of surface area (provided both surfaces are hard), its is dependent on force per unit area.

which works for chains but not rubber belts. but as a rule the softer the more friction. but there friction arrangements between a chain and a belt are totally different.

Belt Drives Pwn You All

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