Nominal Power misunderstood?
- Thread starter (NoLongerRegistered#15675)
- Start date
Amongst other things it means I know the law which you very clearly do not. You've taken one aspect of the EAPC law and an engineering reading of power output and had the nerve to lecture those who know far more than you on the subject.
Pedelec law exists in four parts of different laws. In respect of motor power I suggest you read EN15194 and understand it thoroughly before lecturing on the subject.
.
What, Smart man? Let's friggin hope not
So what you're saying, is that in certain situations your bike DOES output more than 250W.
So, does it, because you can't have your cake and eat it?
And nobody has said anything along lines select a particular gear, a 1 in 8 hill, a cadence of ... And continue for . . minutes...
And yes I,ve said all along my motor/controler are probably capable of supplying well in excess of 250w but the bike/rider as a system ,taking speed cut off and the torque reduction with increased cadence, make this highly unlikely if not almost impossible.
As said earlier I could pedal at cadence of 20 ( or so) up very steep hill in high gear and keep graphic high but a) my legs don't want to sustain this and b) I wouldn't abuse bike in this way.
(I haven't and wouldn't sustain this as no rider would but yes if I did perhaps the current draw is over 250w but the bike/rider as a whole system do not continue this, so bike does not exceed 250w continuous, so I can not drain my 400wh battery in under an hour.
In essence what I,m saying for my Yam haibike ( not soundwaves or anyone elses) is that 250w (from motor) plus a third of 250 w from rider. ( an highest setting mine is roughly 3 times rider contribution) gives 330 w ( or so) which is adequate to climb any hill. The bike doesn't need to draw 700 on steep climbs. We change gear, keep cadence up, bike gives its 250 and rider gives 80...
Lance Armstrong only puts out 450 or so on steep long ascents, we go probably under half his speed.( except Soundwave?)
The bike isn't designed to keep us up with tour riders on ascents. Its designed to get us there at cyclists pace with minimal current draw. It does that perfectly and with 250w not this magical 750 or so.
Apologies about earlier " none sense" comment. It was uncalled for...
And yes I,ve said all along my motor/controler are probably capable of supplying well in excess of 250w but the bike/rider as a system ,taking speed cut off and the torque reduction with increased cadence, make this highly unlikely if not almost impossible.
As said earlier I could pedal at cadence of 20 ( or so) up very steep hill in high gear and keep graphic high but a) my legs don't want to sustain this and b) I wouldn't abuse bike in this way.
(I haven't and wouldn't sustain this as no rider would but yes if I did perhaps the current draw is over 250w but the bike/rider as a whole system do not continue this, so bike does not exceed 250w continuous, so I can not drain my 400wh battery in under an hour.
In essence what I,m saying for my Yam haibike ( not soundwaves or anyone elses) is that 250w (from motor) plus a third of 250 w from rider. ( an highest setting mine is roughly 3 times rider contribution) gives 330 w ( or so) which is adequate to climb any hill. The bike doesn't need to draw 700 on steep climbs. We change gear, keep cadence up, bike gives its 250 and rider gives 80...
Lance Armstrong only puts out 450 or so on steep long ascents, we go probably under half his speed.( except Soundwave?)
The bike isn't designed to keep us up with tour riders on ascents. Its designed to get us there at cyclists pace with minimal current draw. It does that perfectly and with 250w not this magical 750 or so.
Apologies about earlier " none sense" comment. It was uncalled for...
Last edited:
Physics is physics - a universal constant. This stuff doesn't change just because you're riding a specific bike.
With your average upright bike (aerodynamic profile) on flat ground, it takes roughly 250W to sustain 15 mph. The ratio of motor to human input is irrelevant. That is where your 250W continuous comes from. On a legal pedelec, once you're travelling over 15mph (or thereabouts), the motor is contributing zero. If you manage to sustain close to 15 mph up any kind of gradient, I promise you that it is taking more than 250W continuous to do so.
The problem here is that you do not have any cold hard numbers at your disposal and could really do with a numerical power meter to show you what's going on.
At the very least, you should have a play with this motor simulator to gain a better understanding about what happens in various scenarios:
http://www.ebikes.ca/tools/simulator.html
Select a high gear and ride up a steep hill and you stand the best chance of seeing higher levels of motor power for longer periods of time. If the Yamaha control system prevents you from doing so, then IMO, you have bought a pup of a bike.
With your average upright bike (aerodynamic profile) on flat ground, it takes roughly 250W to sustain 15 mph. The ratio of motor to human input is irrelevant. That is where your 250W continuous comes from. On a legal pedelec, once you're travelling over 15mph (or thereabouts), the motor is contributing zero. If you manage to sustain close to 15 mph up any kind of gradient, I promise you that it is taking more than 250W continuous to do so.
The problem here is that you do not have any cold hard numbers at your disposal and could really do with a numerical power meter to show you what's going on.
At the very least, you should have a play with this motor simulator to gain a better understanding about what happens in various scenarios:
http://www.ebikes.ca/tools/simulator.html
Select a high gear and ride up a steep hill and you stand the best chance of seeing higher levels of motor power for longer periods of time. If the Yamaha control system prevents you from doing so, then IMO, you have bought a pup of a bike.
Hi Flud,
I assume you are able bodied and your bike fulfills your needs and therefore feel the current laws are sufficient but unfortunately the laws of nature take precedence and cannot be altered even though governments and trade bodies believe they know better.
The current EU law and the proposed law does not take this into account and discriminates against disadvantaged riders introspective of age hence the call for more powerful motors and the use of an independent throttle.
All high power demands are over 15mph..hence cut off.
At 15 mph , no wind this suggests around 80 watts..
But I do agree riding just under cut off speed up a gradient is going to be most expensive in current terms..
Riding under 5mph wind drag is negligible and in a low enough gear a tiny motor would suffice.
Acceleration is costly, takes approx 7.5kw to get a ton of metal to 15 mph.( from my rolling mill days) so getting a 100kg rider will be around 750w ??? but bike doesn't do it in a hurry so not very much really. ( time is irrelevant )
Think we,ll have to agree to disagree ,..again..
At 15 mph , no wind this suggests around 80 watts..
But I do agree riding just under cut off speed up a gradient is going to be most expensive in current terms..
Riding under 5mph wind drag is negligible and in a low enough gear a tiny motor would suffice.
Acceleration is costly, takes approx 7.5kw to get a ton of metal to 15 mph.( from my rolling mill days) so getting a 100kg rider will be around 750w ??? but bike doesn't do it in a hurry so not very much really. ( time is irrelevant )
Think we,ll have to agree to disagree ,..again..
Last edited:
You know what, I might be a bit out on the consumption figure - it's probably closer to 200W, but I don't have a reliable source to hand. Definitely more than 80W though.
the average value for air resistance depends very much on your profile against the air, if you crouch, wear lycra and ride your aerodynamically optimized bike in a velodrome then 80W at 15mph makes sense. The real world figure for e-bikers riding at 15mph in a little bit of wind is 200W to 250W depending on your bulk.
In any case, the air resistance is proportional to velocity to the power of 3.
In any case, the air resistance is proportional to velocity to the power of 3.
Its to power of 2...but rises exponentially yes..( ie double speed will create quadruple drag...ie 2 squared, treble speed will be x9..( 3 squared)
The graph is for upright ordinary cyclists..Armstrong and co maintain 30 mph with around 450watts..( yes in sprints they might go upto 1.5kw but continous is 450 ish)
The graph is for upright ordinary cyclists..Armstrong and co maintain 30 mph with around 450watts..( yes in sprints they might go upto 1.5kw but continous is 450 ish)
Look at this way...
Lets assume a pedelec can give out 720 w fairly continuous.( ie for half an hour) ( 720 from max controller current(20) @36v)
Even on high setting rider would have to be putting in a steady 230 w..( that equates to pedal pressure of about 35lb)
First of all would any rider capable of chucking in 230w continuous be on a pedelec ?
How many if us are fit enough to sit on a leg squat machine set to 70lb and push reps out at rate of 30 a minute for half an hour? Not many..
Lets assume a pedelec can give out 720 w fairly continuous.( ie for half an hour) ( 720 from max controller current(20) @36v)
Even on high setting rider would have to be putting in a steady 230 w..( that equates to pedal pressure of about 35lb)
First of all would any rider capable of chucking in 230w continuous be on a pedelec ?
How many if us are fit enough to sit on a leg squat machine set to 70lb and push reps out at rate of 30 a minute for half an hour? Not many..
Let me put a few things straight Flud. First you greatly underrate rider power, an averagely fit rider can maintain a steady 200 watts, the third of 250 watts you suggest is quite puny at 83 watts. We consume 50 watts just sitting still in an armchair.
The 330 watts that you suggest is sufficient to climb any hill is well short of that required by legal wheel hub motors which, unlike crank drive units, can gain no gearchange advantage. They require very much more power on many steeper hills.
On your prior comments that companies such as Bosch would not knowingly break the law, that shows a misunderstanding of the law. A company can supply an e-bike/pedelec with any power they wish and many do. For a example, one, a long term member of this forum, supplies machines with around 2 kilowatts of motor power. There is no law forbidding companies from doing this, an offence is only committed in the public use of such machines, the liability falling entirely on the consumer.
To illustrate this, our UK EAPC law restricted all e-bikes/pedelecs to 200 watts of continuous maximum power from 1983 to 6th April 2015. But from 1999 Yamaha supplied 250 watt rated pedelecs throughout that period and from 2001 Giant did also. From 10th November 2003 to that 2015 date almost all companies did also, and after a warning notice issued by the DfT in 2005, almost all of the companies continued to knowingly supply 250 watt machines which could not be used legally in the UK. The late entrant Bosch joined in that knowingly for more than four years.
In essence, there is no such thing as an illegal pedelec, there is only illegal usage.
Finally a practical example since you asked for one. From 1999 for over a decade Powabyke, one of the longer established companies, supplied their e-bikes with a legal 200 watt rated wheel hub motor. At one point published data on one of their popular models showed it consumed a stable continuous 600 watts at 7 mph climbing with around 60% efficiency at that point. That means its net power output was around 360 watts continuous, near to double it's nominal legal rating. It's prodigious hill climb ability supported that.
I have other practical examples, including two on the Bosch unit.
.
Last edited:
Related Articles
-
MTF Enterprises announces acquisition of EMU Electric Bikes- Started by: Pedelecs
-
Wisper 806T folding bike wins Which? ‘Best Buy’- Started by: Pedelecs
-
Sustrans calls for protected cycle lanes- Started by: Pedelecs
-
Amazon launch their first UK e-cargo micromobility hub- Started by: Pedelecs
