Can it be done? a hill-climbing & range calculator...

[flecc]

why not call it what to look for in an electric bike THE SIMPLE ANSWER and make it prominent,
mike

The trouble is Mike, it's not simple as I've been showing. One bike might only be capable of half the hill that another can climb. Essentially they are similar, except that one has twice the power.

But those power outputs aren't published, so telling people to look out for a high motor power won't help them, they'll still be in the dark.

We could do some calculation and give a good indication of the hill each bike could climb with a notional weight rider of notional ability. But if a buyer weighed three stones more and was much less of a rider than he thought, the hill climbing for him would be enormously compromised. Equally, a two stone lighter person than the notional rider, who was very fit in addition could substantially exceed the prediction.

The reason for these very big variations is the very low power of electric bikes, the slightest change in circumstance making a large change in result. On a small car with at least 75 times the power available at the minimum, the driver weight makes next to no difference, so car performance is predictable with much greater reliability, particularly since that's the sole power source.

The completely unknown rider power output which can be as great or greater than the hub motor's output makes electric bike prediction almost impossible.

It's like you saying to me, "Here's a car, I don't know it's weight, I don't know it's power output, and I don't know it's engine size. Now tell me what hills it can climb, how fast it can go, and how far will it travel on a gallon of petrol".

What hope do I have of telling you something reliable?
.

 

[coops]

Agreed!

Thanks Flecc & Mike - wow! These must be some of the longest posts I've ever seen! They don't seem that long as you type them, do they?...

Good points & great suggestions - I agree about the AtoB guide mike, I found it very accessible & informative, and I guess that is the most helpful way of entry in to ebikes and as flecc said, and I've seen him do, I guess the equations can be a useful tool, but only for a detailed analysis of characteristics of bikes, if necessary, and even then only on an individual basis!, with a large pinch of salt!!! And only in the hands of a skilled & experienced adviser who knows his stuff & to aid recommendation of bikes for others & to help people make a good informed choice of bike for their individual needs - it is a forum, after all, and thats its place I think, and no two people's needs are the same!

But I'm still pleased I've put the information up there, of how an analysis can be begun, and maybe those who are interested can now swap notes on the basis of such data to resolve the occasional little quirks and eccentricities of some bikes

Just to emphasize I'm not "trying to put the boot in" on this Stuart, some while ago I'd considered having a website dedicated to helping people choose an electric bike. Therefore I'd done a lot of work on these calculations with that end in mind. As you can now see though, the end result wasn't going to help anyone, least of all those who most needed the help, there being so many variables.

I never felt you were flecc, it all makes sense to me now...

Incidentally, the Quando isn't geared for lower speed as you've said, it's normally geared, and if anything a touch on the high side, although I don't think you meant quite that, it was just the context. It does what it does on sheer power alone. Of the group, only the Chopper is lower geared (13 mph), only the Torq higher geared (20+ mph).

Yes, I was a bit tired and trying hard to be true & clear, but I think my words were "geared for lower speed than torq" which covers a multitude of possibilities I know, & could mislead, so doesn't necessarily mean "low-speed" but thanks for the clarification.

My conclusion is that the most helpful thing for potential buyers, experienced or otherwise, is comparative road tests, on the same territory of the type A to B do. They're not perfect by any means, but they are readily understandable.

So what you're saying is.... RACE! RACE! RACE!... Hehehe! bring on Presteigne eh? and safe, fun competition .

Stuart.

 

[flecc]

Here's another look at the performance comparisons in hill climbing. This time three eZee models have been used with four typical riders covering the whole ability range to produce the calculations to determine the steepest hill that can be climbed at each bikes speed for maximum power. Each rider is male for consistency and is presented as a different numbered case study. Gradients numerical and percentage for personal preferences.

1) Rider very fit, athletic, at peak, late 20s, 10 stone/ 63 kilos

Torq: 1 in 5.8/17%, Sprint: 1 in 4.6/22%, Quando: 1 in 4.1/24.5%

2) Rider fit, 40s, 12 stone/ 76 kilos

Torq: 1 in 7.5/13%, Sprint: 1 in 6/17%, Quando: 1 in 5.3/19%

3) Rider a bit unfit, late 50s, 16 stones/ 102 kilos

Torq: 1 in 10/10%, Sprint: 1 in 8/12.5%, Quando: 1 in 7/14%

4) Rider unfit, early 60s, 20 stone/ 127 kilos

Torq: 1 in 13.3/7.5%, Sprint: 1 in 11/9%, Quando: 1 in 9.4/10.6%

NOTES: First there's the obvious disadvantaging of the Torq due to it's higher gears against the other normally geared bikes, the Quando using exactly the same Li-ion battery/motor power chain and being almost exactly the same weight. The Sprint is 4 kilos heavier and has 9% less peak power than the other two, but still has better ultimate climb ability. Against that is the fact that since each is climbing at it's optimum power to speed ratio, the Torq is 40% faster during each climb than the others. Therefore, in a run across country with equal conditions of rider and bike limitation, as long as the hills were within the rider's and Torq's climb ability, it will always get there well before the others.

Next are the massive differences according to rider ability, around 2.25 times difference overall. Even between the inner two riders there's a substantial difference, and it's also this which makes a fair presentation of electric bike performance so difficult as to be verging on the impossible. Rider 2 will be happy with the Torq's hill climbing, while rider 3 who can only make 10% will not be impressed. The difference of opinion on this between riders 1 and 4 will be extreme.

However, it's the relationships between the models, not the riders, which gives away each bike's intrinsic relative ability.
.

 

[rsscott]

Hi Flecc,

thanks for the additional information and all the hard work you've put into it.

I think what is clear from all this is that we've arrived at "a fair presentation of electric bike performance" and that is, there is no simple answer!

While it's now unlikely we can build an accurate hill-climbing calculator (there probably aren't many people able to guage their own fitness level accurately enough to arrive at their peak watts etc), I think the examples you given can most certainly help people place themselves in the relevent camp and therefore get an idea of what they and their bike will be capable of, on paper at least.

cheers
Russ.

 

[rsscott]

Flecc, would it be ok to use your above figures/calculations for an article on the main site / FAQ section in the forum ?

cheers
Russ.

 

[flecc]

Yes of course Russ, please feel free.