Hi. I've never ride a pedelec and I can't understand one thing: most of Bosch propelled pedelecs have very low front gear, for instance 15T. Considering that bike is propelled by electric motor only up to 25 km/h, how can you go faster than that by just pedalling yourself with such a low front gear? Cadence should be huge in this case... I don't get it, could you explain it to me, please?
Simple question
- Thread starter janek5567
- Start date
that is a very clever arrangement.
SW, how fast is your cadence when you want to hit 30mph?
what are you talking about? I use 46T ring on my CD bikes.
I reckon Bosch engineers use the small sprocket at the front to stop people abusing their bikes.
In the Bosch system ( Haibike) the crank gear does not rotate at same rpm as crank. As SW says it rotates 2.5 x crank speed. Engineer told me a small front gear made preventing derailment easier and lifted ground clearance slightly.
The Yamaha (Haibike) crank and crank gear rotate at equal rpm..
I was a little confused when rode Bosch...same rear gears, same overall gearing but smaller crank gear...didnt make sense..until system explained..
The Yamaha (Haibike) crank and crank gear rotate at equal rpm..
I was a little confused when rode Bosch...same rear gears, same overall gearing but smaller crank gear...didnt make sense..until system explained..
They steal efficiency from the rider by transmitting pedal power through an epicyclic, just to make their system more efficient by decreasing the motor drive reduction ratio.
I think this is bad practice since average pedelec rider power is far more limited than their motor power.
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I thought the 2.5 reduction would reduce the load on the chain and torsion in the bottom bracket beside giving the bike a high tech look.
The load on the chain will be the same, it will consists of the rider power slightly reduced by the gearing loss, plus the corresponding increased motor power due to the more efficient internal gearing.
Their system brings more risk of the chain failing to release and wrapping around the sprocket, especially when the latter is worn with some hooking, something a few members have experienced. Greater chainwheel wear too, than a full size sprocket.
I bet Yamaha and Panasonic don't follow suit.
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You can add harder to clean to that list.
I've experience chain wrap twice now when forgot to engage XT derailleur clutch.
... It seems the postings have taken off on a life of their own. The answer to your question is that there is a 2.5 speed up gear between the cranks and the pedel and the small chainwheel. So yes even if the power is off, one rev of the pedel causes the chain wheel to go 2.5 times. The electric motor feeds power somehow into the same chainwheel . If the motor is off, or if travelling above the assist speed of 25km, there is a freewheel or clutch inside the unit so that the motor does not drag when on human power only. There is a little click heard, felt every rev when on human power. Without power the bike runs and feels like a pretty heavy conventional bike, but the motor is not interfering.
. The speed of the chain is the same as on a conventional big chain wheel bike, so the tension on it and the power transmitted will be the same. The only difference is that the little front chainwheel is going like the clappers. It also looks feels like the chain will not fall off, as can happen on conventional big chainwheels. It also makes it easier to put chainguards around it.
I also wonder if such arrangement (2.5 intermediate reduction stage) reduces the overall wear and weight of the gearbox.