going more than 15mph

[Straylight]

So guys, about this inertia thing then

Surely there comes a point when accelerating under power that the inertia of the bike plus rider is overcome by momentum, and mightn't this account for the sense of increased torque/power/that surging feeling in the seat of the pants, quite often described on this forum.(I know this has little to do with what you've been 'discussing' but I thought it might make for a welcome intermission).

For what it's worth, using nothing more scientific than my ears and the balls of my feet, my Wisper seems a lot more happy on hills above 10ish mph than below, where it feels like it's trying to grind to a halt.

 

[john]

So guys, about this inertia thing then

Surely there comes a point when accelerating under power that the inertia of the bike plus rider is overcome by momentum, and mightn't this account for the sense of increased torque/power/that surging feeling in the seat of the pants, quite often described on this forum.(I know this has little to do with what you've been 'discussing' but I thought it might make for a welcome intermission).

For what it's worth, using nothing more scientific than my ears and the balls of my feet, my Wisper seems a lot more happy on hills above 10ish mph than below, where it feels like it's trying to grind to a halt.

Hmmm.... not quite sure what you are getting at.
Inertia is really just another name for mass (in the context of a force being applied to it). Inertia is mass multiplied by your velocity, the two things can't really come into conflict as your mass doesn't change (Ignoring Einstein here of course).

I guess you do feel a bit of a surge as you get going. I'm not sure why that is. It may be psychological in that you are surprised at the increasing power from the motor (much more than you would get from pedalling or from an ICE vehicle).

I don't have a way of measuring acceleration but it would be interesting to produce a real plot for an e-bike setting off.

 

[Herb]

INERTIA

An example of inertia is when a post is full of - Mass/Velocity/precise definition/formula and cannot be stopped by simple common sense.

Herb

 

[flecc]

For what it's worth, using nothing more scientific than my ears and the balls of my feet, my Wisper seems a lot more happy on hills above 10ish mph than below, where it feels like it's trying to grind to a halt.

I know what you mean and it is true that from around the mid point of speed capability an e-bike climbs best. It's not really about inertia, more a matter of how the motor works.

That's the point I was making originally, that it's only when maximum power coincides with the torque curve that the hill climbing is optimal. From then as speed increases the efficiency also increases so the sense of the motor straining reduces.

The upper half of the speed range therefore gives the best sensation of climbing ease.
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[Straylight]

So would the ideal hub motor have two sets of internal gears to cover the normally used speed ranges, and stay efficient for more of the time? I know it'd make the design a lot more complicated, but surely it could be done.

 

[eddieo]

I'm going back to bed......D)

 

[lemmy]

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.

But I said 'knee -jerk reaction'. Yours is a considered reason with which (as a London cyclist myself) I agree.

What I mean is that if the powered limit were raised to 20mph, you would have people saying "why only 20mph, why not 30mph"?

I don't believe the future of e-biles is in greater speed, beyond, say 20mph, but in greater range through more efficient lighter battery technology.

If the pedal equipped e-bikes are produced with power that will take them beyond 25/ 30mph, I will bet that helmet and insurance laws will be enabled. The trouble is, legislators being what they are, these will be applied to all pedal equipped electric machine.

At the moment, no-one is even considering making helmets, insurance etc compulsory and I want to keep it that way. If as a result it takes me 45 minutes to central London instead of 42, I'll live with that. That's what I meant by 'knee-jerk' reaction.

 

[flecc]

So would the ideal hub motor have two sets of internal gears to cover the normally used speed ranges, and stay efficient for more of the time? I know it'd make the design a lot more complicated, but surely it could be done.

Yes, I made this point in my Technical forum article on Drive through gears on e-bikes:

There is a probability that two gears for the motor only and separate from the rider's gears, with maximum power/torque at a choice of either 6 mph or 10 mph would provide better for steep hill climbing,

Here's the full article link.

It's possible, though difficult, to combine the two gears as part of a hub motor's epicyclic gear train as I've explained in this forum previously. That would be by having the epicyclic reduction for steep hill climbing but the motor switching to direct drive for normal running at speed.
.

 

[Straylight]

Excellent! Why isn't anybody making it?

 

[flecc]

Excellent! Why isn't anybody making it?

Don't know! I first proposed this idea about two years ago.

It's tricky to implement with sensible ratios and a freewheel, so manufacturers have a good excuse to continue as they are, just using simplicity and high power as a sledgehammer to crack the nut.
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[Tiberius]

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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Gentlemen, please.

What is going on here? I go out for a day and come back to this. I was beginning to wonder if the start of the thread was a wind up, but there's no excuse for this.

John is right; flecc is wrong. That should be the end of it. John pointed out a minor inaccuracy in one of flecc's posts. What's wrong with that? If we can't have technical accuracy on here then what's the point? I don't think John was being pedantic; he was just trying to stop readers being misled.

In return, John seems to have been roundly condemned, and we get this spurious argument about "practical" reality rather than real reality.

Nick

 

[flecc]

Practical help is not spurious Nick, in this forum it's far more valuable than theory. It's all very well for scientists like you and others who are very technically aware to be pedantic about perfect accuracy, but that doesn't help those who do not have the full appreciation of the technicalities. As they so often have made clear when praising the way I post, they want to have understanding without all the complexities, they don't want a physics lesson.

I have the ability to post in the way you and John want, but what is the point if it's not helping?

The point I made is valid, in what way did John pointing out that maximum torque occurs at zero revs help anyone, they can't climb hills at zero revs? John's admission of the inefficiency of climbing below the point I mentioned is further acknowledgement of the limited value of such advice.

I used to be able to post practical advice of the sort that the majority of e-bikers understand and appreciate without constant criticism, but it seems to be increasingly impossible recently.
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[fishingpaul]

Yes, I made this point in my Technical forum article on Drive through gears on e-bikes:

There is a probability that two gears for the motor only and separate from the rider's gears, with maximum power/torque at a choice of either 6 mph or 10 mph would provide better for steep hill climbing,

Here's the full article link.

It's possible, though difficult, to combine the two gears as part of a hub motor's epicyclic gear train as I've explained in this forum previously. That would be by having the epicyclic reduction for steep hill climbing but the motor switching to direct drive for normal running at speed.
.

The cytonex trek bikes nano motor had two speeds i thought,one for use on hills or to conserve power and one for assistance above 11mph.

 

[flecc]

The cytonex trek bikes nano motor had two speeds i thought,one for use on hills or to conserve power and one for assistance above 11mph.

It's two controller switched power levels Paul, not two geared speeds.

There's a way of switching some types of motor winding formations to give climb or speed ability.

However, what we are referring to here is two internal mechanical gears for the optimal result.
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[Tiberius]

The point I made is valid, in what way did John pointing out that maximum torque occurs at zero revs help anyone..

Well, it would help someone who was trying to get their head around the way electric motors work. On the other hand, in what way did it harm anyone?

Wouldn't it have been better to just say "Good point, what I meant to say was......"?

Nick

 

[flecc]

On the other hand, in what way did it harm anyone?

It harmed me. Quoting from my post to say I was wrong would leave anyone I'm advising thinking I was incompetent. The truth of course is that I have the dual competence of knowing that theory but having the abilty to simplify it where that's desirable.

Wouldn't it have been better to just say "Good point, what I meant to say was......"?

Nick

I've done that previously Nick, but I don't see why I should have to post that repeatedly every time John or someone else takes issue. I've explained many times my intentions in posting in a practical manner, explaining why precision isn't helpful to the majority. I really shouldn't have to do it every time I post on such issues.

If I was in a scientific forum I would expect to be upbraided, but not in a practical forum like this. It's destructive and unnecessary. Those like you and John who are technically aware will already know the precise position. Those who aren't technically aware largely don't care, they just want a little understanding learnt through simple explanation.

Think of the oft used explanation of voltage and current by comparison with the water from a tap. We know it's not precise, but it's immensely useful in spreading basic understanding, and for the great majority, that's all that's needed or wanted.
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[Tiberius]

If I was in a scientific forum I would expect to be upbraided, but not in a practical forum like this.

I don't think you were being upbraided. John just pointed out a mistake. And this is a thread with technical content. Its not fair to then shift the ground and argue that we're in a place where technical accuracy is neither helpful nor wanted. I agree there are threads on here where technical accuracy would be out of place, but this is a thread about speed, power and hill climbing, so the torque and power curves of a motor are important.

Nick

 

[john]

Gentlemen, please.

What is going on here? I go out for a day and come back to this. I was beginning to wonder if the start of the thread was a wind up, but there's no excuse for this.

John is right; flecc is wrong. That should be the end of it. John pointed out a minor inaccuracy in one of flecc's posts. What's wrong with that? If we can't have technical accuracy on here then what's the point? I don't think John was being pedantic; he was just trying to stop readers being misled.

In return, John seems to have been roundly condemned, and we get this spurious argument about "practical" reality rather than real reality.

Nick

Cheers Nick, I was kind of hoping you might come in on the thread.

I had no desire to wind flecc up, the vast majority of his advice is invaluable. To be honest I was beginning to doubt my own understanding and perhaps there was some reason whey maximum torque was not a zero rpm. So my reason for posting was partly to engage in a discussion on that fact. The 'scientist' in me wants to challenge my beliefs and understandings. The other reason is that it grates on me when information is posted on the internet for the everyone to see which is factually incorrect. The last time I let it go but this time I thought it was worth correcting. I know not everyone is interested in the physics but reason that they can quickly pass over my post if they wish.

 

[richardmu]

Everyone's posts and opinions are appreciated!

As a relative newcomer to e-biking I follow these posts every day and find them extremely informative and very entertaining sometimes!

flecc is the Guru and I look forward to and appreciate his opinions. Just the right mix of technical and practical detail for me and I am sure that goes for many that read this forum.

Keep it up flecc and thanks to everone that posts and makes this forum so special to all of us the have an interest in e-bikes.

 

[flecc]

Thanks Richard, I know from the many comments, PMs and emails I get from here and from my websites that my approach to explanation is appreciated.

The more technical members don't seem to appreciate the intent or desirability of this approach to the facts. Possibly their thorough understanding leaves them too close to the subject to see the bigger picture, i.e. that most just don't want scientific exactness and prefer simple explanations, even if some accuracy is sacrificed.

I do find it tiresome dealing with this sort of thing when all I want to do is give the maximum effective service to members.
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