I've lost the thread

flecc · Feb 27, 2007

The formula is an accepted one that's been around for some while, not exclusive to me.

I think the main problem is that you are not making the necessary adjustments.

First, the 576 watts for the Torq is the power consumed, the net power is less. That figure is not available, but if we assume a high efficiency, which it definitely is, say 80 to 85%, the net power is around 460 to 490 watts. This is what's used for the calculations.

Then there's the other losses, rolling resistance, friction, wind resistance etc. For this latter group it's best to make an estimated total. It will be affected by the bike's climb speed of course, since wind resistance will be almost non existent at 6 mph, but present at 12 mph. Think in terms of about 60 to 100 watts loss, the exact amount isn't critical since these are comparative calculations, not absolutes.

Finally, this is a hill climbing power formula, it has no relevance for riding on the flat since the constant is disproportionate for that. In fact the power used for riding on the flat in still air at up to 12 mph is generally just given a nominal figure of 50 to 100 watts, depending on the bike's variables, no calculation necessary.

Believe me, the various cycling formulas can easily mislead, as the above shows, there being so many ifs, buts and maybes. They are always best used only as comparatives as I've done, and never as absolute predictions for a particular bike and rider combination.

The orbital gearing reduction on the Torq is about 7 times which you don't really need, the revs of the hub at any given speed can be worked out from the wheel diameter with the standard Kenda tyre of exactly 28", giving 87.92" circumference. There's 63360 inches in a mile of course, so if that's divided by 87.92 to give 720.66 revs per hour, then divided by 60 to give the revs per minute, for the Torq it's conveniently exactly 12 revs per 1 mph. Just multiply the 12 by whatever speed you want for the revs per minute for that. e.g. 12 x 15 mph gives 180 rpm hub speed.

Hope that's some help to you.

P.S In one of my recent postings I did in fact state that the Torq won't climb a 1 in 8 unassisted, despite calculation indicating it should be possible. I also stated it would only just scrape 1 in 7 with my weight. The reason as stated there is the overgearing that the motor has in the Torq. It's design includes a nominal rider's power, unlike most electric bikes which are normally geared and have some optionality on whether one pedals or not. With the Torq it's not an option, rider power is essential in all but absolutely flat conditions.

That's why I always refer to the Torq as unique, in a separate class of it's own. If you want some further explanation of why the overgearing has this effect, post back.
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flecc · Feb 27, 2007

P.S. to the above.

The power required for hill climbing formula is only really accurate at around the middle of the gradient range. It progressively loses accuracy for lesser gradients, which is normally ignored since there's little point in calculation for minor gradients that are never a problem anyway.

Some authorities recommend that for steeper gradients, the fraction that's used for G (gradient) should be replaced with this in the formula:

sine[tan-1(rise/run)]

but I don't bother for my purposes, since as said, I'm not looking for absolutes. I think it pointless to do so where the extreme variability of any individual's performance is part of a calculation.

N.B. The -1 in the above formula is a power expression, which I can't display in it's proper position here.

flecc · Feb 27, 2007

I wouldn't like to guess at what rated means in the comparison of these two motors Peter. There's too many missing facts, plus the matter of trust in the figures we are presented with.

Here's more info on the Quando/Torq motor though.

In the Torq with motor power only, I can perceptible feel power still being transmitted at 24.4 mph on a fractionally negative inclined road near me, average 0.6% gradient.

That's not it's maximum though, wind resistance and overgearing denying that.

In the Quando on motor alone with a NiMh battery (nominally 36 volts) just off the charger, the Quando just tops 19 mph on the same stretch before the power stops driving.

That means the Torq should give that power up to 26.6 mph, with the motor in the larger wheel, particularly with it's nominally 37 volt volt Li-ion battery, so 319 hub rpm and motor rpm of roughly 2234.

On those Cyclone versions, since they drive through the gears, any of the motors will get you up a 1 in 8 (12%) if the gearing's ok, though the 180 watt might be going too slow to balance the bike! It's just a matter of each motor increasing the speed of climb depending on it's power.

Judging from my Twist motor which drives through the gears and has a peak 390 watts output, the Cyclone 360 (500 peak) might get me up 12% at about 7 mph without pedalling. That's very much a guestimate though, and could be up to 2 mph out either side. The Twist's pedelec mode which requires some pedal pressure makes accurate judgement very difficult.

On human output for hill climbing, I find the 300 watts for 5 minutes for a healthy male (NASA) is more useful, since 5 minutes covers most hills.

Re: the early hours posting, I'd just finished doing some theoretical workings on a design I'd been considering when I had a final glance at the forum. I'd have posted earlier but for that other work engrossing me.

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flecc · Feb 27, 2007

ITSPETEINIT said:
I don't think that this side of 50 yo I have been anywhere 300 watts. But I do recall the decline was very rapid over the last 10 years. I am concerned about the time I will hit Zero Watts

I easily matched up to that first sentence wattage at 57 yrs old when I did an intensive cycling year, getting out almost every day for the whole year regardless of weather for up to 54 miles of North Downs cycling, unassisted of course. At the end of that I weighed barely 61 kilos of muscle, bone and skin.

Didn't last though. Matched up to your second sentence in the last four years and at 71 yrs now about 74 kilos. I blame the invention of electric motors.

For convenience I've invented a new rule regarding healthy weight. From the age of 60, for perfect health a person's weight should be one kilo for each year of age, plus or minus 5%.

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coops · Feb 27, 2007

Found the thread, lost the internet connection!

Hi Peter,

(Excuse the lateness - I prepared this in the early hours today as a reply to your initial post and Flecc's reply which occurred while I was typing, but then my internet connection inexplicably went down till now so apologies if its not exactly current to the thread: I hope its still relevant & of interest

)

Is this the plea you refer to? :

ITSPETEINIT said:
I have a dream that Torq owners will DECLARE THEIR WEIGHT when posting observations about their bikes peformance. I have a Torq-friend who, compared with me, is diminutive and wizzes up 1 in 8's. I have trouble with the local 1 in 10 (I've yet to make it to the top without a rest) the A30 immediately west of Shaftesbury, Dorset.

- taken from this thread

(I hope your virus has cleared up by the way).

I'm not a Torq owner (does that exempt me from disclosure of my weight?

- lets just say I'd have a tougher time on hills than you!) but from what I've read about hub motors I tend to agree with Flecc's conclusion that the power output of the Torq is around 460-490W, and since this is the 'power' value required in the hill-climb formula you mention, its quantification (however approximately) is vital to any attempt at even a rough calculation. Weight of rider makes a big difference to ease of hill-climbing too as you say.

You are right, zero Watts power output required on the flat is anomalous (though it would be nice

) and yes, roughly speaking, the power required for hills is in addition to that required for the flat: as Flecc said the formulas can easily mislead and in this case the reason is that other forces (wind resistance, rolling resistance, friction etc) which can require a significant amount of power to overcome, especially at higher speed/stronger headwind or with knobbly tyres, low aerodynamic bike or riding position or clothing (!), are not included in the very simple model.

When a correction is made for these (wind resistance normally being the biggest factor - we've all experienced the difficulty of pedalling into a headwind) of, say, 60-100W (as Flecc said) at the sorts of speeds we're talking about, then, since this applies both to hills and flat, roughly this power output, rather than zero watts, is required to maintain a constant speed on the flat, while the additional power output needed for hills is given by the formula.

So from your figures and Fleccs "real-world experience" (taken from aforementioned thread) plus a little guesstimation, it would seem that a rough indication of Flecc's power input at various gradients would be:

[Guesstimates: Torq power output ~ 475W ; correction for drag etc ~ +60W]
[Torq with standard gearing 58" to 122"]

1 in 10 (10%) - ok - (527 + 60 - 475) = 112W legpower approx.

1 in 8 (12.5%) -bit hard, very hard if long: (~660 + 60 - 475) = 245W approx.

short 1 in 7 (~14%) really tough going and my limit: (738+60-475) = 323W approx.

Which seem not a million miles away from expected figures?

-and if your Torq is still lower geared than standard, at similar legpower levels and/or reduced speeds you may be able to equal/exceed these gradients? (I can't do the maths right now...

)

Additionally, it would seem that roughly 8-9% for Flecc or 7-8% for you Peter, is do-able unassisted on a Torq, as a conservative estimate...? How does this compare in reality?

I hope that helps?

Stuart.

flecc · Feb 27, 2007

coops said:
Additionally, it would seem that roughly 8-9% for Flecc or 7-8% for you Peter, is do-able unassisted on a Torq, as a conservative estimate...? How does this compare in reality?

Stuart.

I've real world tested this Stuart, and my Torq in good running condition with a freshly charged Li-ion will barely scrape up a fairly short 7% slope unassisted. Its a bit cruel to it too, and not recommended for that motor. It's just about comfortable on 6% unassisted. It can't get anywhere near the theoretical 8% with my weight.

The reason is purely that it's overgearing has taken the geared speed range to a position well above it's unassisted performance ability. In other words as said before, rider power is an essential component.

The same motor normally geared in the Quando can treat the rider as superfluous on everything 12% or less.
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flecc · Feb 27, 2007

coops said:
So from your figures and Fleccs "real-world experience" (taken from aforementioned thread) plus a little guesstimation, it would seem that a rough indication of Flecc's power input at various gradients would be:

[Guesstimates: Torq power output ~ 475W ; correction for drag etc ~ +60W]
[Torq with standard gearing 58" to 122"]

1 in 10 (10%) - ok - (527 + 60 - 475) = 112W legpower approx.

1 in 8 (12.5%) -bit hard, very hard if long: (~660 + 60 - 475) = 245W approx.

short 1 in 7 (~14%) really tough going and my limit: (738+60-475) = 323W approx.

Which seem not a million miles away from expected figures?

Those three wattage figures for my cycling do match up with my experience and past performance measures Stuart, must say quite accurate despite my generally not approving of measurement for a specific peformance.
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coops · Feb 28, 2007

flecc said:
I've real world tested this Stuart, and my Torq in good running condition with a freshly charged Li-ion will barely scrape up a fairly short 7% slope unassisted. Its a bit cruel to it too, and not recommended for that motor. It's just about comfortable on 6% unassisted. It can't get anywhere near the theoretical 8% with my weight.

The reason is purely that it's overgearing has taken the geared speed range to a position well above it's unassisted performance ability. In other words as said before, rider power is an essential component.

The same motor normally geared in the Quando can treat the rider as superfluous on everything 12% or less.
.

Yes, I appreciate that the Torq's most appropriate use is very much a power-assisted bike, not pure motor powered, and I'm sure it wasn't too happy on those gradients unassisted, its just to get an idea of the useful limits of the motor alone, taking the bike's drivetrain gearing out of the equation to allow analysis of rider & motor's separate contributions to performance of bike as a whole

.

I think my estimate of 8-9% for the torq + 76kg rider unassisted was a bit optimistic: with different guesstimated corrections for "drag" at the different speeds of the quando & torq (say 80W @ 12mph & 40W @ ~8.5mph) and with the peak power output @ ~475W, the predicted gradient limits for a 100kg (bike+rider) unassisted would be:

Torq ~ 7.5%
Quando ~ 11%+

Which, while not exactly what you have found in reality, is near enough (about 1% gradient difference) for me, as a rough guide to motor limits in each bike.

Incidentally, applying the same to your case, Peter, would give (Torq @12mph):

limit of motor alone ~ 6.5%
limit with 100W rider input ~ 8%
limit with 150W rider input ~ 9%

- check my figures & take with a pinch of salt

.

Stuart.

coops · Feb 28, 2007

flecc said:
Those three wattage figures for my cycling do match up with my experience and past performance measures Stuart, must say quite accurate despite my generally not approving of measurement for a specific peformance.
.

...Probably more by luck than anything else

. My subsequent less optimistic Torq recalculation probably reduces the accuracy somewhat - you'd have to add about 20W to each of the three figures for consistency... still, they're a "ballpark" figure

. Hope you didn't mind being a "guinea pig" for the calculation, its just your figures were available since you've posted so much useful performance data

Hope the information is useful for you too Peter.

Stuart.

flecc · Feb 28, 2007

coops said:
I think my estimate of 8-9% for the torq + 76kg rider unassisted was a bit optimistic: with different guesstimated corrections for "drag" at the different speeds of the quando & torq (say 80W @ 12mph & 40W @ ~8.5mph) and with the peak power output @ ~475W, the predicted gradient limits for a 100kg (bike+rider) unassisted would be:

Torq ~ 7.5%
Quando ~ 11%+

Which, while not exactly what you have found in reality, is near enough (about 1% gradient difference) for me, as a rough guide to motor limits in each bike.

Stuart.

When within a bike's capabilities, the calculation limitations of usefulness can show up more easily. You're right that minus 1% makes the Torq figure fit with reality, and plus 1 % brings that Quando figure to what I've indicated as an average.

However, if I now took the Quando with freshly charged NiMh out onto an adjacent 14%, it will climb that unassisted. The error is getting quite big now, that 3% being an increase of over 27% in that indicated climb ability. With a freshly charged Li-ion it even does that with 8 kilos of shopping as well, throwing the calculated result even more adrift. Less than five minutes later it couldn't do either of those, once the first flush of charge had gone.

That's what I mean about using the calculations as absolutes. As comparatives with the same conditions applied in the calculations, they are useful. As indicators of actual performance, they have very definite and quite large limitations.

You may have noticed that in all the time in this forum I'd never used calculations until the thread on calculating bike performance cropped up, and all these subsequent discussions have arisen from that. That's because I think for the majority they aren't useful except for making the eyes glaze over. I've just looked at the number who've viewed this thread, 128, a lot less than half that for other established threads around it, indicating what I mean!

I bet the comment "are they still at it?" passes through many minds.

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coops · Feb 28, 2007

some hopefully useful ideas, Peter

Peter,

I'm very sorry to hear that your virus persists: I have virus tussles and know how troublesome they can be and I wish you a full and speedy recovery

.

Talking of tussles... please don't wrestle with those figures if its detrimental to your health! Suffice to say that 1 in 8 is clearly quite a challenge for you on a Torq even with pedalpower, which you've already found, though I admire your determination! (and you mustn't think it is a weight issue, it just seems to be the way the Torq is geared). I'm also intent on using an ebike to combine exercise, utility & cleaner local travel.

The same motor as the Torq but in 20" wheels - the quando - would probably fare better: as Flecc has said, it is a very able climber, but I'd guess that for you on that 1 in 8 hill progress would slow a little - maybe around 6.5 mph? (Unless you can pedal the 70" gear with a very slow cadence, which I wouldn't like to try!) but I think it should do it, I'm just not sure whether its within single battery range (16-20 miles round trip?) - not forgetting that the battery's range will decrease with time. Maybe if you can be economical with the power in other parts of the route it may be done? Shame the quando has only one 70" gear - if it had a more useful range of gears I'd be very tempted to get one myself, but it is a folder after all - which also may be useful to you occasionally?

Did you try the Twist again? From what I read it's just about the most popular & complete ebike around, and its documented all-round performance - efficiency, range, hill-climbing aswell as pedalability with the motor off - is enviable and would seem to suit your requirements very well? Though I'm uncertain whether the hub-gear alterations are necessary for your hills - other members & their posts here will have more information on that aswell as its suitability for your needs

.

Hope that helps.

Stuart.

coops · Feb 28, 2007

ok, ok...!

flecc said:
You may have noticed that in all the time in this forum I'd never used calculations until the thread on calculating bike performance cropped up, and all these subsequent discussions have arisen from that. That's because I think for the majority they aren't useful except for making the eyes glaze over....

... I bet the comment "are they still at it?" passes through many minds.
.

Yes, absolutely right Flecc: I'm making a "spring" resolution now, to cease the calculation discussion forthwith (and that's not sarcasm - I genuinely mean it!).

My thanks to both Peter & yourself though, for pointing out the need for a wind/rolling resistance correction in the "equation", and I've added a note & link to this thread in my initial post in the hillclimbing calculator thread - for information purposes only

.

I bet you can't wait till I get an ebike and stop talking theoretically, and start discussing more real-world issues! All the bits for my kit should be in next week, so hopefully not long now (until I'm posting on how to put together my electric bike

).

Stuart.

flecc · Feb 28, 2007

coops said:
I bet you can't wait till I get an ebike and stop talking theoretically, and start discussing more real-world issues!
Stuart.

No. not in any hurry at all Stuart, and my comment was in no way an admonition, just an expression of why I don't normally use calculation. The subject is fascinating, and I've enjoyed these discussions, though far more than the majority of members have, I suspect.

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coops · Feb 28, 2007

flecc said:
... my comment was in no way an admonition, just an expression of why I don't normally use calculation. The subject is fascinating, and I've enjoyed these discussions, though far more than the majority of members have, I suspect.
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Don't worry Flecc, I didn't take it that way

my view is that it is only of interest if it is useful, and as you say it is of limited inherent usefulness or practical useability to most (confusing at best and sometimes even misleading) and risks boring (at best) and/or bewildering (at worst) many others... so I feel now its best to keep any of that stuff in its place, else its not polite or helpful

.

Things did seem to go kind of quiet when it was under discussion, now you mention it!

Stuart.

flecc · Feb 28, 2007

coops said:
Things did seem to go kind of quiet when it was under discussion, now you mention it!

Stuart.

Yes, I noticed that too! I did worry a little that a potential newcomer to e-biking visiting the forum and opening one of our entries first might have felt they were in the wrong sort of place, fatal since they are our lifeblood for growth.

I've lost the thread

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