going more than 15mph

[john]

A bike with a top speed of 15MPH will not climb hills, unless the hub/drive is geared ridiculously for torque, which is rare.

I'm not sure what you mean by 'rare'. A typical direct drive motor with a 15mph top speed (not controller limited) will be a poor hill climber. Nearly all of the geared motors when used up to 15mph (except for the smallest) have more torque than fast direct drive motors and are hence better hill climbers.

 

[daniel.weck]

15MPH top speed is useless. Absolutely useless. It disappears with wind resistance, a headwind, soft tyres, and hills, poor roads. In order to hit 15MPH on most roads, you need to have 22MPH capacity to begin with.

First of all, I concur with other riders' feedback regarding torque / hill-climbing ability with geared hub motors (or bottom-bracket-located ones, for that matter). Because of the laws of physics, my 16"-wheeled 250W Bafang-powered folding bike is indeed a great climber. Yet, its *assisted* top speed is limited to 15mph-25km/h due to the RPM [1] rating of the motor (under nominal circumstances). The peak power consumption is around 400W under nominal voltage (36V) and at the recommended current: my LiFePO4 15Ah battery and my cheap controller safely delivers 12A of juice to the motor (the motor could deliver more power if I upgraded the other components, i.e. by raising the voltage and/or the current.

The point is that one rarely needs assistance above the legal assisted speed anyway, because the good-old legs and muscles are amply adequate (in my case, up to 50km/h downhill, and 20-25km/h average on my hilly local landscape). The electric contribution is most useful at lower speeds, where the demand in human effort is normally quite high: hills, wind, or simply because low velocity = less weight-induced momentum. Momentum, just like the effect of gravity on a downhill section, is a kind of assistance, right ? That's why the act of cycling, for most people, shouldn't require assistance at higher speeds.

I don't understand this obsession with moped / throttle-only riding...e-bikes are not e-scooters (which require crash-helmet, road insurance, etc.), and are not designed to replace ICE-powered bikes either [2]. There is value in these individual modes of personal transportation, but e-bikes are in the HPV category [3]: the whole point is to reduces the amount of effort a rider has to produce, not to totally replace muscle work. This enables us to cycle farther and on hillier terrain, whilst keeping the levels of sweat down (without getting exhausted).

E-biking has enormous value for people who have given-up on cycling due to health problems or because of sheer laziness (or whatever the reason might be). It helps people getting back in shape, by regaining control and confidence in their physical abilities. It is also extremely useful for those who want to rely on their own muscle to commute to work, without being all smelly at the other end. Personally, I am fit but I don't have strong legs, so e-cycling means I can carry heavy loads on hilly terrains without having to rely on my car. I also cycle to places where i would normally not be brave enough to venture.

I for one am a regular visitor of the Endless-Sphere forum, and although I am in awe with regards to the DIY skills involved in building these high-powered fast e-bikes, I just don't understand the point of keeping pedals on bicycles that are mostly designed for throttle-only riding. By contrast, the German Pedelec forum is geared towards low-powered (i.e. legal) e-assistance, with members that demonstrate some really cool DIY skills. There, just like here, depicts an e-cycling experience that is far from boring !

I guess there will always be the Jeremy Clarcksons of the e-bike culture: "Powaaaaarrh !"

[1] Rotations Per Minute
[2] Internal Combustion Engine
[3] Human Powered Vehicle

 

[john]

I just don't understand the point of keeping pedals on bicycles that are mostly designed for throttle-only riding.

From my point of view there are several reasons, others will have different reasons.

1. You get exercise - stay fit
2. The best central heating money can't buy!
3. You go (a bit) faster
4. You go further
5. Backup if the battery/motor fails

For me, this type of vehicle is far preferable to an ICE moped (polluting, noisy, no pedals etc)

Modes of transport are may and varied and people use them for many and varied reasons with many and varied preferences. Why would someone assume that their preferences apply to everyone?

 

[daniel.weck]

This is a polite exchange of views. I am not trying to convince readers to agree with me ...and I'm very interested in hearing the opinions of others.

1. You get exercise - stay fit

In practice, riders of high-power e-bikes seem to travel mostly in throttle mode, without pedaling. Ultimately, the low power requirements imposed by the law is a form of incentive to pedal / exercise. Let's put it another way: if the regulations allowed higher assisted speeds, the message conveyed to consumers would be ambiguous, and the line between a moped and a bicycle blurred beyond acceptable levels. A hybrid-HPV should remain a HPV, first and foremost (i.e. assistance is secondary). The Solex was a moped that could be helped when necessary with leg power...a different category in my opinion.

2. The best central heating money can't buy!

I'm afraid I don't get the joke

3. You go (a bit) faster

How much over 20km/h (assisted) would be deemed acceptable ? Personally, I am all for increasing the legal speed a little, providing some amount of human effort is required to put the vehicle in motion. Effectively, due to the high pedal cadence involved at higher speeds, the average e-rider faces a natural limitation of HPVs. I am in favor of allowing throttle-only mode for speeds below a given low threshold (because it is very useful to start from a standstill, in traffic or uphills, etc.). Any speed above that threshold should be subject to human contribution

4. You go further

I suppose you mean "go further for a given amount of time". Sure, time is a finite and scarce resource in today's busy world, so going faster is useful. However the beauty of HPVs is that it gives us an opportunity to appreciate time (and space) from a different perspective and to enjoy life at a human pace. Thus why I think e-bikes will eventually be regulated under different sub-categories.

5. Backup if the battery/motor fails

This sounds like an electric Solex then. A moped with pedals..."just in case"

For me, this type of vehicle is far preferable to an ICE moped (polluting, noisy, no pedals etc)

Fair enough. I guess somewhere between bicycle and "motor"-cycle, there is a hybrid world where assistance is either provided whilst pedaling (my preference) or as an alternative to pedaling (what you are talking about, I think).

Cheers, Dan

 

[andyh2]

This is interesting for me at present. I was considering a more powerful, though still legal, hub than my tongxin hoping for better hill climbing and a bit more top end. Reading through this I realise that better hill climbing is definitely the more important of the 2 for me and would probably give better average speeds than a motor geared for higher top speed.

I'd be very happy to have stricter control of the 15mph maximum speed in exchange for greater legal power which could give better climbing and load carrying ability. eg the currently illegal 500w stokemonkey set up for 15mph max would be a very capable unit.

On an off topic note it would be great if there were a 'Euro' version of the panasonic which condensed the power down phase. My understanding is that the Japanese regs mean the power reduction phase is clearly laid out and starts at around 10mph? That could start later for Europe allowing greater assistance nearer the 15mph limit. I'd have thought the sales to Europe would be enough to have a different version of the software.

Back on topic whilst there could undoubtedly be improvements in the legislation surrounding electric assist bikes I am very pleased there is a vehicle category which can provide assistance, be used anywhere a bicycle can and maintain the cycling experience.

It would be great if there were more (or even some! widely available) mainstream makers of quality electric scooters (Honda, Peugot, Vespa etc) in the market and available now. That way there'd be a clear choice for folk.

 

[flecc]

On an off topic note it would be great if there were a 'Euro' version of the panasonic which condensed the power down phase. My understanding is that the Japanese regs mean the power reduction phase is clearly laid out and starts at around 10mph? That could start later for Europe allowing greater assistance nearer the 15mph limit. I'd have thought the sales to Europe would be enough to have a different version of the software.

15 kph (9.4 mph) is the start of power phasedown under Japanese law, power ending by 15 mph. That Panasonic haven't seen fit to change that characteristic isn't without reason.

The new Yamaha unit which we have now in the Gepida bikes is virtually a Panasonic clone, but they have changed the power characteristic to one that gives the maximum power for longer. The downside to that according to reports is that the power cutoff seems abrupt compared with the silky smooth power phasedown of the Panasonic.

In practice this means the Yamaha seems to constantly switch in and out of power assist when riding around the limit point, rather disconcertingly to some. The full phase down near the assist cutoff point on the Panasonic means there's no sensation of power constantly cutting in and out then.

Obviously it's best to try the Yamaha to see if it suits, since individual tastes are different.
.

 

[lemmy]

I am interested that a bike with a max powered speed of 15mph won't go up hills - my Kalkhoff I bought for its hill cimbing ability and it seems to me, at least, that it would happily climb any hill I'm likely to meet in the UK.

Also, a bike with a powered max of 15mph is perfectly capable of traveling at speeds faster than that. On general roads, I keep up about 17/18mph on my Kalkhoff and rather more on my non e assisted bike.

If I wanted to go faster, personally I'd use a car or motor-cycle. I'm not convinced that the future of electric assisted pedal cycles consists in going faster. Why do we have this knee-jerk 'faster is better' reaction?

 

[flecc]

I am interested that a bike with a max powered speed of 15mph won't go up hills - my Kalkhoff I bought for its hill cimbing ability and it seems to me, at least, that it would happily climb any hill I'm likely to meet in the UK.

Hub motors are the problem. Not having the benefit of being able to select a lower motor gearing for climbing means that any hill that forces them below the coincidence point of maximum torque and power (commonly around 8 to 10 mph) means a failure to cope without greatly increased rider effort.

Up to about 10% hills with an average rider, hub motors cope ok, but with hills of 14% or steeper they get progressively more feeble.
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[HarryB]

Why do we have this knee-jerk 'faster is better' reaction?

Because sometimes faster is better and safer! As a regular cyclist in London I can say that I felt much safer keeping up with traffic on a bike that can marginally break the 15.5 mph limit - it doesn't even have to be by much. The fewer cars that overtake the better in my view and since riding electric bikes I have not had a single "turn left on me" experience, when the vehicle cannot make up its mind if it should overtake you before turning left at the junction (you are particularly vulnerable going up hills). That said the Torq 1 sometimes felt too fast at 22-23mph. I think an overall speed limit of 20mph for cars and ebike in residential/commuter areas seems a bit of a no-brainer to me.

 

[john]

the coincidence point of maximum torque and power

As I have mentioned before, for any BLDC motor, maximum torque is always at 0 rpm, maximum power is somewhat higher (around half the max rpm). This is because torque is proportional to motor current and this current drops as the motor turns due to the back EMF produced.

 

[john]

Because sometimes faster is better and safer! As a regular cyclist in London I can say that I felt much safer keeping up with traffic on a bike that can marginally break the 15.5 mph limit - it doesn't even have to be by much. The fewer cars that overtake the better in my view and since riding electric bikes I have not had a single "turn left on me" experience, when the vehicle cannot make up its mind if it should overtake you before turning left at the junction (you are particularly vulnerable going up hills). That said the Torq 1 sometimes felt too fast at 22-23mph. I think an overall speed limit of 20mph for cars and ebike in residential/commuter areas seems a bit of a no-brainer to me.

I agree! (apparently my message has to be at least 10 chars long )

 

[flecc]

As I have mentioned before, for any BLDC motor, maximum torque is always at 0 rpm, maximum power is somewhat higher (around half the max rpm). This is because torque is proportional to motor current and this current drops as the motor turns due to the back EMF produced.

Zero revs is no use to them for hill climbing. As I've said more than once before John, there is a point at which the torque remains high as the power reaches the maximum region, and that is what matters to the e-bike rider. That point is indeed around half way up the rev range and it is the point of maximum torque/power in the sense of when the highest torque is coincident with maximum power. Thereafter torque falls away. It is the point that is most useful to the e-bike rider when hill climbing.

Theory and technical pedantry doesn't get them up hills, it just confuses those who wish to receive practical advice. I prefer to give practical advice and not have to constantly explain this point every time in answer!!!!!!!
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[john]

Zero revs is no use to them for hill climbing. As I've said more than once before John, there is a point at which the torque remains high as the power reaches the maximum region, and that is what matters to the e-bike rider. That point is indeed around half way up the rev range and it is the point of maximum torque/power in the sense of when the highest torque is coincident with maximum power. Thereafter torque falls away. It is the point that is most useful to the e-bike rider when hill climbing.

Theory and technical pedantry doesn't get them up hills, it just confuses those who wish to receive practical advice. I prefer to give practical advice and not have to constantly explain this point every time in answer!!!!!!!
.

"Torque" is a physics term with a precise definition. Unlike a few other terms used in physics, I don't think it has a definition outside of that. Using it incorrectly causes confusion.

 

[daniel.weck]

"Torque" is a physics term with a precise definition. Unlike a few other terms used in physics, I don't think it has a definition outside of that. Using it incorrectly causes confusion.

I think Flecc's point is that the great majority of readers on this forum are interested in knowing what the practical implications are for a given theoretical definition. Very few can fully comprehend the scientific nature of torque, let alone grasp the complex relationships with all the other mechanisms / factors involved in human+e-power bicycle motion.

I too like a bit of science, but the statement "maximum torque from zero rpm" (i.e. no motion) doesn't tell much about the distinct real-world surge of "power" experienced when riding with electric assistance.

I remember the first reviews of the Tesla sports car: editors were hard at work trying to come-up with plain English descriptions of the unusual power delivery and uncanny feel of relentless forward motion experienced with this vehicle. Readers may actually be able to appreciate the statistics, pretty graphs and scientific underpinnings, but at the end of the day, we all want to know what it means in practical terms.

I think that Flecc's use of language is exemplary, and his claims are always backed-up by scientific facts. I don't think he creates confusion, quite the contrary.

Regards, Dan

 

[flecc]

Thnaks Dan.

John, no-one comes into this forum for lessons in physics and electrical theory, they do often come in here for practical advice on e-bikes and their usage.

Since no hill will ever be climbed by a motor at zero revs, your post had no value other than point scoring.

It is your use of such theory that is confusing, since it is worthless in a practical context to any e-biker.
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[daniel.weck]

Thnaks

I withdraw my statement about your use of language !

 

[flecc]

I withdraw my statement about your use of language !

It's not the language, it's my utterly incompetent use of keyboards that's the problem Dan.
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[john]

your post had no value other than point scoring.

It is your use of such theory that is confusing, since it is worthless in a practical context to any e-biker.
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We can discuss facts or we can hurl insults. I see little value in doing the latter.

 

[john]

I too like a bit of science, but the statement "maximum torque from zero rpm" (i.e. no motion) doesn't tell much...

What it means is you get the biggest push from the motor and hence can climb the steepest hill when you are going slowest.

It should be noted however that a slow turning motor is rather inefficient and will generate a lot of heat, so not something to be engaged in for any length of time.

 

[flecc]

We can discuss facts or we can hurl insults. I see little value in doing the latter.

You can post your lecture on torque any time you wish John, but when you accompany it with a quote from my post, it's point scoring, since you know from my previous responses that I don't need a lecture from you on this subject.

Just give the point scoring a rest and leave me to give practical posted answers that are of use to e-bikers.
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