Cytronex Cannondale Super Six Ultegra

[flecc]

I should have guessed! Still, perhaps as electric bike use becomes more popular, people will be willing to trade some efficiency for cleaner trousers...

I think I'll either stick to cycle clips or a chainguard as on my present bike.
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[Rab C Nesbitt]

Years and probably never!

Toothed belt drive is very inefficient compared to chain drive and the difference is quite obvious in riding when comparing the two. In fact the Zero shaft drive is better than toothed belt in efficiency terms.

Strida use toothed belt on their "triangular" folder for cleanliness/convenience reasons and Harley-Davidson have used it on some of their massive V twins which have no bother with overcoming the inefficiency. Otherwise it's never made inroads into two wheelers after many failed attempts to introduce them, despite toothed belts having been around for more than half a century.
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Flecc

I know I'll probably get my ar$e kicked here as you are better versed in these things than most of us - I heard (through the day job) that there was some R&D (research & development) money being thrown at Gates Rubber Company in Dumfries to try and push forward a "rubber" belt that was suitable for bikes as they reckoned the worldwide market would make it worthwhile.

Do you not see any immediate progress on the horizon given that they would obviously use modern Nexus hubs for example giving the bike that nice straight "chain" line ?

Ok , I'll get my coat . . . . .

Rab


YouTube - Ditch the Chain, a New Type of Bicycle Is Here


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[flecc]

. Not going to kick anything Rab!

The problem is inherent to these belts, firstly in that the rubber has to bent around each toothed pullet from it's natural state. That means the inner rubber layer below the unstretchable synthetic fibre inner cords has to compress into a smaller length while the outer rubber layer has to stretch into a longer length around every turn. Then to exacerbate that, the rubber of the teeth has to slide against each pulley tooth face as each tooth enters and slides out again afterwards, and rubber is a very good material for grip but not so good at sliding freely, why we use it for tyres of course.

The chain by comparison bends very freely around each turn with no compression/extension losses and the chain rollers roll along the tooth faces at entry and exit with virtually no friction. You can see there's no comparison on efficiency.
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[Bigbee]

It must be your browser setup as that link takes me to the page showing the bike

Maybe try it in another browser firefox or iexplorer whichever one you are not using.

Regards

Jerry

Hi I was in Firefox,I can see it in IE,thanks.

 

[Barnowl]

. Not going to kick anything Rab!

The problem is inherent to these belts, firstly in that the rubber has to bent around each toothed pullet from it's natural state. That means the inner rubber layer below the unstretchable synthetic fibre inner cords has to compress into a smaller length while the outer rubber layer has to stretch into a longer length around every turn. Then to exacerbate that, the rubber of the teeth has to slide against each pulley tooth face as each tooth enters and slides out again afterwards, and rubber is a very good material for grip but not so good at sliding freely, why we use it for tyres of course.

The chain by comparison bends very freely around each turn with no compression/extension losses and the chain rollers roll along the tooth faces at entry and exit with virtually no friction. You can see there's no comparison on efficiency.
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The Trek district uses a Gates Carbon fibre drive belt. They claim it's as efficient as a standard chain.

"The carbon cords inside the patented Gates Carbon Drive™ belt offer, for the first time, the necessary tensile strength and high modulus to provide the smooth, clean, and long lasting ride advantage of a “belt” driven system in a bicycle application. The specially designed tooth pitch and meticulously engineered sprocket profile afford the belt efficiency equal to that of a standard chain, with the low tension necessary to prevent unnecessary bearing load on other components."

I have tried the bike and it felt very good. Of course any inefficiencys would probably only show over distance.

 

[flecc]

The Trek district uses a Gates Carbon fibre drive belt. They claim it's as efficient as a standard chain.

"The carbon cords inside the patented Gates Carbon Drive™ belt offer, for the first time, the necessary tensile strength and high modulus to provide the smooth, clean, and long lasting ride advantage of a “belt” driven system in a bicycle application. The specially designed tooth pitch and meticulously engineered sprocket profile afford the belt efficiency equal to that of a standard chain, with the low tension necessary to prevent unnecessary bearing load on other components."

I have tried the bike and it felt very good. Of course any inefficiencys would probably only show over distance.

That doesn't alter what I said about the compression and extension of the rubber and the rubber tooth friction, those are the source of the inefficiency, not the cords. The tooth profiles were perfected many years ago as were the high tensile cords, since these belts are used extensively in the motor industry in vehicles to drive the water pump, alternator, camshafts etc from the crankshaft, and the cords do not affect the efficiency so long as they are high tensile and unstretchable.

To say they've achieved equal efficiency to chains is bunkum which I've heard many times previously, but they would say that, wouldn't they, they're selling something.

What I've said is from long experience of working with these belts and I know their strengths and shortcomings well. However, they are long lasting and could outlive a bike, so if some inefficiency doesn't matter to a rider, they are a good way of avoiding chain maintenance and changing.

Not for me though, my human watts are too few and too precious to waste.
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[Barnowl]

Not for me though, my human watts are too few and too precious to waste.
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I'm still carrying enough to waist

 

[flecc]

. Good for you!

Seriously though, with average fit humans through their best years only capable of about 200 watts fairly continuously, every few are precious which is why chains have lasted the course despite their annoying sides. They are as close to a 100% efficient way of transferring continuous drive from shaft to shaft that's ever been devised, nothing else known comes close.
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[Pedalo]

I guess I'd be willing to give up a little efficiency but not a lot. I'm very pleased that my bike rides very much like a normal bike when the electrics are not switched on and I wouldn't really want to compromise on that.

However the idea of no mess does appeal. Perhaps I just need a bit of practise/training getting the back wheel on & off. Whenever I need to do so to repair a puncture or replace the inner tube I manage to get my hands/clothes/everything! covered in grease getting the wheel back on. I tend to carry a couple of rags in my toolkit now which helps a bit.

 

[Mark/Cytronex]

Hopefully that whole cycle - dental web site scenario has been sorted out now,
so if anyone finds themselves (after refreshing their browser) on our dental site when they clicked on a cycle link please let me know and I'll be inserting an electric toothbrush in an appropriate place!

The new link for our range is now on the no-hills retail site at:

Cytronex Electric Bikes --- Cytronex - The UK's leading electric bike


Thanks,

Mark