Yes I could keep my graphic high by abusing both bike and my legs.( ie falsely high gear, low cadence lowish speed) but moment I pedal " normally" ( correctly) current draw diminishes below the legal limit.

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...

Edited April 4, 201610 yr by (NoLongerRegistered#15675)

Chinese bikes with or without throttle don't have this naturally balanced rider x plus motor 3x or 4x.

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.

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...

 

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.

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.

 

Yep I see that..

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.

I think your power estimate is very high..have a look...

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..

Edited April 4, 201610 yr by (NoLongerRegistered#15675)

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.

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 drag force F is proportional to the square of speed, but power consumption is also proportional to speed (P = FV), hence power consumption is proportional to the cube of speed.

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..

the drag force F is proportional to the square of speed, but power consumption is also proportional to speed (P = FV), hence power consumption is proportional to the cube of speed.

 

You add them , they ain't compounded..

X squared plus x squared is 2x squared ...

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.

 

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.

.

Edited April 4, 201610 yr by flecc

You add them , they ain't compounded..

X squared plus x squared is 2x squared ...

 

Flud, you misunderstood my post. F is the drag force, the equation or drag force is:

F = 0.5 * Ro * V * V * Cd * A

Ro is the air density roughly 1.223kg/cubic m

V is speed, in m/s

Cd is the drag coefficient, for a bicycle + rider, between 0.7 for a racer to 1.2 for an average e-rider.

A is the area (or profile) of the bicycle + rider, in square meter

 

P is the mechanical power required to propel the rider and bike at V. P = F * V

 

Therefore:

 

P = F * V = 0.5 * Ro * V * V * V * Cd * A

 

P is proportional to V cube.

 

resource:

 

http://www.cyclingpowerlab.com/CyclingAerodynamics.aspx

 

???

 

So according to this untrained cyclists ( which is group I,d put myself in) can achieve 1.5 w per kg..I,m 105 kg so I,m looking at around 160w ??? When working hard???

Again from wiki...

and

Bike so efficient we can pedal along at 9 3 mph using less energy than walking at 5 ???

 

So giving your average cyclist ( who will only weigh around 75 kg) another 250w is way over doubling their available power...

 

But flec, very well written and good post...

 

But I,m inly referring to CD bikes and legal ones as described elsewhere.. Yes ungeared hub motors will have to draw way more than 250w...but isn't that the whole point of cd drive units ???

 

Trex

Your calculations and explanation are spot on. I stand corrected over calculations for total power required..They do go up extremely quickly with advancing speed, its even steeper than I,d estimated..but since legal pedelecs shouldn't be powered above 15 mph its a bit superflous..

Power required at 15 mph is not such a great deal..sub 100w..

Edited April 4, 201610 yr by (NoLongerRegistered#15675)

 

According to this a 70kg cyclist capable of producing 350w for an hour would be considered an elite athlete...

But I,m inly referring to CD bikes and legal ones as described elsewhere.. Yes ungeared hub motors will have to draw way more than 250w...but isn't that the whole point of cd drive units ???

 

It used to be the point of CD, especially in the early strict 200 watt days, but more recently they've got into a power race.

 

To give some idea of the situation, back in 2001 Panasonic's new CD unit was a true 250 watt one, not very powerful by today's standards and with an increasing power limiting system from 15 kph (9.4 mph) upwards.

 

In 2006 they introduced a new unit with higher efficiency but which operated similarly and became very popular with a number of European manufacturers of pedelecs, especially in Germany. Their only rival in Germany was the small company Daum with a more powerful CD unit.

 

It was then that Bosch woke up to the possibilities and produced their first unit which understandably perhaps had some faults. Among them that it was so high powered that it was destroying bike chains very quickly, leading to Bosch calming it a little. However they still became a subject of complaints from Shimano, since the unit still exceeded the loading limits of Shimano's hub gears and SRAMs for that matter. The Bosch answer to that was to slightly downrate the units supplied for hub gear bikes, the derailleur ones remaining the same.

 

Of course customers liked all that power and the Bosch units swept the market, knocking Panasonic right out. Panasonic who had always used 24 volt systems belatedly retaliated with a very powerful 36 volt one and also removed the power phase down on the 250 watt ones, but it was too late and they remain virtually absent from the European market.

 

Meanwhile German bike company Kalkhoff who had been using Bosch after dropping Panasonic units bought the Daum unit rights and developed it as the Impulse 1 unit to rival the Bosch power. Take off for them was quite good, but they then brought out the Impulse 2 which was even more powerful. The outcome was that started to chew up and destroy it's internal gears, causing the new introduction of a replacement model called the Evo, still powerful but hopefully no longer destroying itself. There's threads in here about the Impulse 2 troubles.

 

I think from all this you can appreciate what we are saying about the power of modern units, 250 watts is not going to destroy bike chains in two or three hundred miles or chew up gears that had previously always been ok at 250 watts. It's been obvious for a long time that the Bosch and Impulse units have been far in excess of 250 watt capability and German sources reckon the Bosch has an easy 500 watt capability.

 

In support of that is that Bosch make the one unit which they rate as 350 watts when supplying for the high speed 45 kph S class or to the US market. For the legal pedelec market they call it 250 watts and set the speed limiting to 25 kph instead of 45 kph. The power is unchanged, only the speed limiting is changed. As a result there are "dongles" on the market to override the speed limiting so legal pedelec owners can unleash the speed potential by spoofing the signal the unit gets from the rear wheel rotation speed, illegal of course since it makes 50 kph assist possible. A similar dodge is possible on the Impulse units.

 

Another indicator of the excess power is the introduction of automatic power easing during gear changes to alleviate the problems the high power was causing during changes.

 

Incidentally, all these units are torque sensing, the power depending on the rider input. The full power is only unleashed with sufficient rider input, so your admitted lower inputs are probably not releasing the potential.

.

Edited April 4, 201610 yr by flecc

 

Using an example from my exercise bike, we could possibly achieve 5000 mpg when consuming only edible oils

Me and my Exercise Bike.pdf

if you get a dh pro you can rip the de railer in half:eek:

Flud, you don't seem to be getting it. Let's try and put you in the picture. Going back to the old Panasonic 26v crank-drive system, some people took measurements of the power leaving the battery. I guess Flec will be able to post a graph from his archives to show that the power was round about 400w from the battery. Most motors are around 70% -80% efficiency, say 75%. Add another loss of say 10% for controller and primary drive efficiency brings the power down to 252w at the output sprocket. That motor was absolutely gutless by todays standards. Go and try one to see what I mean.

 

I made a measurement on the first Woosh crank-drive, which showed 14 amps from the battery, so that's 560w to the controller and 365w at the drive sprocket. You could feel that that motor was a lot more powerful than the Panasonic, but still some way behind the Bosch. Since then, Bosch increased their torque, which one would assume also increased it's power because at the same speed, power is proportional to torque. Although I haven't taken any measurements, my information is that Woosh increased their maximum current to 20 amps to get similar power to the Bosch, which would make it 800w from the battery and 500w at the drive sprocket.

 

I've experimented a lot with crank-drives and hub-motors over the years, taking actual measurements of the current from the battery with a wattmeter. After a lot of tests, you get a feel for the relationship between maximum current and the perceived power of the motor. I would say that the Bosch is running at at least 18 amps - maybe 20A. That would mean around 750w from the battery and about 500w at the drive sprocket.

 

Don't forget that the legal requirement is for a motor to be a maximum of 250w nominal continuous output power, not peak power, for which there's no regulation as such.

 

In your example of Lance Armstrong on his 8 kg bike producing 450w to go up a hill, don't forget that he and his bike are something like 40kg or more lower than one of us riding a Bosch/Yamaha MTB. We'd need closer to 675w in the same circumstances.

 

Here's an example of logging data from my present bike that shows the actual current coming from the battery whilst riding. I would say that this bike has approximately the same power as the latest Bosch/Yamaha. The steps are where I change the power level on the display. the controller, fixes the maximum current at each level:

 

http://i451.photobucket.com/albums/qq236/d8veh/rides/speedict%20climb_zpswmvpj536.jpg

Here's a journey graph of the second series Panasonic unit from 2007 when the unit was well below Bosch and Impulse power levels. It can be seen that it almost reached 500 watts at times and routinely to 400 watts. From this graph you can see that this relatively low powered unit averages 250 watts, rather than that being its maximum:

 

Great replies all of you..

I,ll read them all again, do some more research and peddaling!!!

 

 

I have said all along motor/ controller are capable of way more than 250w...Putting bike into a situation where it demands it is quite different ,but I haven,t the evidence to substantiate anything ,whereas your graphs etc speak for themselves. Points accepted....

Thanks for patience. Apologies for pedantic attitude, no offence meant to anyone..

Great thread tho...

I promise to try harder to flatten my battery quicker...and start a new argument afterwards.!!!!

 

The bike is superb..Couldn't recommend it more highly.

Take care.. Good cycling...

 

 

Me and bike top of Neulous. The Alberes..not bad for a pup???

Picture taken at around 3600ft. Climbed up from 198..Took 1hr 48 mins..(and 92%) to just over 4000ft.( top was in cloud as village (Laroque Des Alberes) was when I left..

Edited April 6, 201610 yr by (NoLongerRegistered#15675)

https://www.badassebikes.com/en/typ3-3-yamaha/a-105/

 

for testing only mind lol:)

http://www.pedelecs.co.uk/forum/threads/blackped-range-yamaha-400wh.23756/