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

flecc · Feb 16, 2007

There's no problems with those equations Stuart, I use exactly those two for my calculations for both bike capability and bike + rider capability as I did for Quicken a few threads ago. They're permanently in memory and I just do them the individual way by calculator.

Incidentally, when measuring the speed of a bike/rider combination on a hill, the conversion of m/s to mph I use at the end is x 2.23, once more for the toolbox! I think you'll find that the mph to m/s you've given, divide by 2.16 needs correcting to 2.23.

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rsscott · Feb 16, 2007

Excellent post Stuart. I'm still very keen on a range/climbing ability guide for the site/forum!

Maybe if we start with the bikes we all have along with some common gradients people understand from road signs they see out on the roads we can start to build a list on this thread. I can them collate it and add it to the main site and forum FAQ and add to it as we come across more bikes. Also once we've knocked together the theory it would be great if folks are able to put it to the test and post results back here.

I guess start as simple as possible, try it out, modify it.

cheers
Russ.

flecc · Feb 16, 2007

Hi Russ

Can you say exactly what figures and facts you want us to publish in this thread? For example, maximum gradient possible bike only, ditto with rider. Guestimation of rider ability, age group, fitness group or watts. Speed bike and rider on a given hill gradient etc. Whilst make, model and range is easily given, should terrain be indicated?
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electric.mike · Feb 16, 2007

coop

I just hope the "brain exercise" hasn't driven anyone away

no it didnt drive me away basicly because i dont understand a word of it

flecc · Feb 16, 2007

Great reply Mike. That told 'em!

Right, here goes. To start on a pessimistic note and show what a minefield this is, I've already done plenty of work on this. On a typical list of eight popular high to medium powered bikes calculated to find the maximum gradient they could climb unassisted by a 75 kilo rider, the Quando came second with 13.8%. In practice it easily climbs 12% and will just manage 14% with a newly charged battery, so it just matches the calculation.

The Torq uses exactly the same power chain, battery through to motor, and it's lighter, so it should do better right? Wrong! It calculates as capable of 8.6% and came last of the eight bikes. As if that's not bad enough, in practice it can't even do that, it just scrapes 7%, half what the heavier Quando manages.

Why? It's because the motor in the Torq is in a 28" wheel, as opposed to the 20" wheel of the Quando, so is geared up by 40%. Instead of the maximum torque appearing at around 8.5 mph as in the Quando, it now appears at about 12 mph. At the higher speed much more power is needed to do the same thing. If the Torq attempts the 12% hill at the same 8.5 mph of the Quando's optimum, it's so far below it's power band that it's lost over 40% of it's power, so can't do it anyway.

Portraying the mighty Torq in this way isn't exactly going to excite it's makers or importers, and will bring dissatisfaction from owners.

Adding a fixed average rider power for that 75 kilo rider improves matters considerably for two reasons. The Quando has only a single gear so cannot use the rider input as efficiently. The Torq with it's 8 gears now has an advantage in one respect, but that still won't allow it to beat the Quando where the steep hill limit for bike and rider combined is determined, though the result will be much closer.

If we now fix a more moderate hill, say 8%, for both bike and rider combined, the Torq if restricted and the Quando will be about quits. This is because the Quando is restricted only by the motor which is free to help a bit above 15 mph, which the rider can just pedal to with the 70" gear. The restricted Torq will cut motor power at exactly 15 mph and the average rider won't be likely to push it more than a bit beyond that up a 8% hill. In practice they'll both possibly reach 16/17 mph.

Now if we derestrict the Torq, it wins easily, since it's free to assist the rider to beyond 20 mph, so in combination on an 8%, possibly 18/19 mph could be reached by bike and average rider. The Quando will not have advanced from the 16 mph before, due to the motor being at it's limit and the 70" gear preventing the rider from pedalling any faster.

So which is the better bike? The Quando won the first two, was quits on number three, but lost number four. I hope you can now see what a potential quagmire this is, just from using two bikes only for comparison. Who's going to accept the Quando is better than the Torq?

How this can be presented fairly in single form is beyond me, I'm afraid, but hopefully this contribution will inspire what is really needed to do something in this direction.
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flecc · Feb 16, 2007

We've posted together again Stuart! My contribution is just above your last one.

rsscott · Feb 16, 2007

As you both point out, it's important that this information is presented fairly i.e. showing a bike's strengths AND weaknesses. Using these statistics it would be possible for a newcomer to draw a conclusion that the Torq is not a good hill climber, but that is not the end of the story. On gentler gradients it really does fly and on flat terrain it is unbeatable. There are also many other factors one considers when buying an electric bike such as range, style of frame, seating position, extras, price etc. The 'guide' should present all this information together - not a simple challenge!

electric bikes for sale

flecc · Feb 16, 2007

The fact that I've used the equations to highlight this problem proves they definitely are useful, but the results need interpretation as I've shown. And that's where they can so easily fail to be useful as Electric Mike has shown above. He won't want "if this, here's the result, but if that, this is the result".

Like many, he needs a conclusive definitive answer, but as I've shown, with those two bikes it isn't possible to give a single acceptable answer. The result of those four tests, that the Quando won, would be acceptable to hardly anyone, although as a Quando and Torq owner I know how very capable the Quando is, so I'd be more understanding of it's true relative position. For nearly everyone else who don't own both, that result could leave them baffled.

And it's not only those two bikes that produce such a quandary, there are others.
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flecc · Feb 16, 2007

rsscott said:
and on flat terrain it is unbeatable.

Only if derestricted. If the Torq's restricted, other bikes naturally designed to reach motor limits round about the legal speed limit can beat it, since they are free to run a bit beyond on power, 17/18 mph in some cases, so giving more help, given equal riders on both. That's my third example, where the Quando only failed to get ahead because of it's single 70" gear.
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electric.mike · Feb 16, 2007

coops
the main reason i didnt understand it is i gave up half way through, probaly every thing you say is correct and a good idea, but i learnt my lesson in photography, in the early days it was film i new the resolving power of film and lense combinations ie nikkor and kodachrome 25 gave cracking results, 6x6cm gave better tonal gradation than 35mm, but kodachrome 25 was too slow, 6x6 was bulky and slower to use with seperate light metres,and tons more info i stuffed into my head, i made similar mistakes when i turned digital i tried to know too much and it didnt help my photography one bit,in the end i joined a photo forum explained my interests took advice from several people, and bought a digital camera and lenses that was highly rated on the forum.
i bought my first electric bike without being able to talk to anyone,and i was lucky, the only reason i have purchased a second one is because i never thought i would want to do this much towing.
the second one was purchased after asking advice on this forum and then ignoring it.
ime sure if you turned your idea into a few boxes that i could just enter a few figures into i could then get involved without having to understand it and may find it usefull.
i am probaly saying from a point of total ignorance there must be too many variables even down to where you live surely a battery would perform less well on winters day in scotland than the south coast so if you only end up with set of figures that have prefixes like "up to" or "should achieve" or "with nominal pedaling" will it be of any more help than asking other users on this growing forum.
i nearly didnt post this because it sounds a bit like ime having a pop at you and i am NOT i just doubt you can vector in enough variables.
its strange when something is said in conversation it never seems as critical as when writen.
mike

flecc · Feb 16, 2007

electric.mike said:
its strange when something is said in conversation it never seems as critical as when written.
mike

How true Mike, but I'm sure that as experienced 'net users, no-one in here will take exception.

Your position on this is the same as mine essentially, that the possible variables are so great that producing something genuinely widely useful is going to be somewhere between extremely difficult and impossible.
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flecc · Feb 16, 2007

Here's some of those figures I produced previously. The first group is the eight bikes, showing the steepest hill their own power could climb by calculation. As said above, the Torq in practice can only manage 7%, this being a very unfair test for it, as it's not it's designed purpose.

Below there's two more bikes, this time very low powered models to illustrate another presentation problem. It might appear that they are virtually useless on hills, but that's not in fact true. Once a rider's power is added, there's considerable equalisation. For example, adding an average rider's 250 watts to the 576 watt Quando will add 43% to it's power, but the same 250 watts nearly doubles the Windsor's 270 watts. The Windsor's lower peak torque point makes up some more of the difference, so although it couldn't begin to compete with the former, the Windsor is much more capable than it appears at first. Likewise the low geared Bliss.

eZee Chopper - - - - - - - - -14%
eZee Quando - - - - - - - - - 13.8%
eZee Sprint - - - - - - - - - - 11.1%
Heinzmann/14 kg bike - - - - -11%
BionX/Tivoli Miele - - - - - - - 10.9%
eZee Cadence - - - - - - - - -10.9%
Giant Suede. - - - - - - - - - - 8.6%
eZee Torq. - - - - - - - - - - - 8.6%

Powacycle Windsor. - - - - - - 5.9%
Bliss Folder - - - - - - - - - - - 5.5%

In this next example, the bikes speed is calculated for an 8% hill. This time the Torq and Chopper results appear turned on their head to some extent, but since the Torq in practice can't climb the 8% unassisted, the Quando is tops.

eZee Torq - - - - - - - - - - 13.15 mph
eZee Quando. - - - - - - - - 13.00 mph
eZee Sprint. - - - - - - - - - 11.3 mph
Heinzmann/14 kilo bike. - - - 11.3 mph
eZee Chopper - - - - - - - - 11.3 mph
BionX/Tivoli Miele. - - - - - - 11.2 mph
eZee Cadence - - - - - - - - 11.2 mph
Giant Suede. - - - - - - - - - 10.6 mph

The other problem illustrated in both lists, but especially in the second, is how close the results are for most bikes. In the first list, the steepest hill test, the Chopper won due to it's Sprint motor in a smaller wheel gearing it down at the cost of a lower top speed of about 13 mph. The Quando came second due to the sheer power of it's motor and normal gearing. The next four typical bikes are almost identical.

In the second list, the climb speed with the Torq excluded, the Quando was first for the same reason of it's power and normal gearing. All the rest of the bikes were almost identical. Putting an equivalent rider on them would change very little, other than the Torq being back in with a vengeance.

So it wouldn't really tell anyone anything other than a little folder from eZee being much better than most begin to realise.
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flecc · Feb 17, 2007

Stuart, as an afterthought to your comment re: accepting the 2.23 conversion factor for m/s to and from mph, the error from using that is 0.178%.

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electric.mike · Feb 17, 2007

here we go again, when we bought the two sakuras i new nothing about electric bikes but now i have moved on to the next knowledge step "next to nothing" but as i say i was lucky they are great for steady plodding around a relatively flat area like grimsby.
when we started to go to work on them on the cycle paths, there is one piece that was a road bridge over the railway line, it is steep, my wife sailed up with minimum pedalling,with me i don't know if it was the bike or me creaking but it was a struggle(this is the only place like this for us).so i started to look on the net for the reasons and the information i gathered was piece meal from different places and none mentioned my make of bike.
i realised that being 3 stone heavier didn't help, i thought gears might make it easier for me to help the motor,but i didn't know anything about power, because i understood the max legal power was 200watt. then i learnt that the battery has more to do with it than i thought, with my 36v 7ah i would never get the peak surge that would come with 36v 14ah.
i think what i am trying to say is what i would have found more help would have been simple explanations of how each part of the equation helped or hindered all electric bikes, like i found on the a to b site.
if you do it bike specific rather than a guide to how electric bikes work you would be of less help to a new purchaser,than if they could run the spec of any bike or motor kit, type of motor, battery power from different types of battery, and then decide if that bike met there needs.
as i say this info is out there even things like why a ni mh battery has less amps than a sla but can be better, but i feel we should have this basic info on this site in a easy to understand format so people can make informed descisions.
why not call it what to look for in an electric bike THE SIMPLE ANSWER and make it prominent,all the way through we could put words like "need help to understand then why not register and ask the question" when ever i go on to the pedalec site there are always people viewing, what are they looking? for what can we put on to encourage them to register.
mike

flecc · Feb 17, 2007

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.

Essentially the figures cannot be presented without all sorts of conditional statements to make them have real world meaning. That close group of bikes in the second list above will widen their gaps under real world conditions for various reasons. The Quando has one 70" gear, the Cadence and Sprint have 7 speed hubs, and if the eZee Liv had been included it would have been close to the Cadence on paper being the same weight, but it's 3 speed hub would not have allowed the rider to perform at their optimum. Given that many people do not understand the concept of gearing anyway, all that would be lost on them.

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. The equivalent for us would be members reports on their bikes, but from experience I don't think that would help at all when I get some members telling me that the worst hill climber of all is one of the best! In other words, the errors of perception are far too great for the information to be reliable and comparable. In addition, the widely different territory in members areas would make the results even less useful, and peoples pride in their bike and their choice (ego!) tend to facilitate exaggeration.

It's frustrating, and no-one would like a solution more than me, but your expression "can of worms" is perhaps more fitting with e-bike testing than anywhere else. In essence I think calculation would end up with lots of very close figures as above, and graphs with lots of lines grouped together in bunches.

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).

The norm for the whole European market for hub motor bike gearing of the motor is for a bike to attain about 15 mph at maximum revs on the specified voltage, this leaving maximum torque at about 8 mph, thus fixing the hill climb ability to a considerable extent. Since most bikes roughly conform to this and bike weights are not too different these days and are such a small proportion of the whole weight, only the motor power output is any real measure of the hill climb performance on normally geared bikes, hence the Quando's top position in this.

Another variable in the test conditions for members is voltage, which is high immediately after charging. Again using the unpedalled Quando as an example, on a Li-ion battery straight off the charger, it will run to 18.4 mph on the flat and climb 14%. Ten minutes later it runs to about 15.5 mph and will only manage about 13%. On an NiMh battery the hill climbing results are almost the same, the lower peak voltage balanced by the lower voltage drop under load than Li-ion, but the respective speeds are 17.5 and 15 mph. I could be reporting any of these, and they are rather different.
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Can it be done? a hill-climbing & range calculator...

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