Hill climbers

[Phil the drill]

This is a bit of a recurring theme for me, but please indulge me if you will.
For many people, speed appears to be an issue with electric bikes and bikes with high cruising speeds ("off road" modes, de-restrictable etc) seem to dominate. However, we are all pretty much lumped with the 200 - 250w of useable (continuous) power, so compromises need to be made.
Inevitably this boils down to one of two things:-
1) Going fast - limited to minor inclines and the flat.
2) Not going so fast, but getting up steeper hills.
The perception that I have is that the former is winning, by a country mile, and this seems to be the area most manufacturers are targetting. Perhaps I should not be surprised since many buyers seem to be city commuters, often based in London / home counties / Oxford / Cambridge etc. i.e areas where the definition of a hill is something along the lines of "Can I park without the handbrake on?" I don't wish to denigrate those souls, they are a big market sector, and manufacturers must obviously cater for that.
The rest of us however struggle to find electric bikes that cope with our needs. Worse, if you make a mistake and live in flattish area, then all that happens is your commute takes a little longer. If you make a mistake in my area you are left with something that is useless to you, and an expensive artefact.
I can't test ride hardly any e-bikes within a 50 mile radius, and I don't know a single other user in my county (I've lived here for 14 yrs, and I'm pretty sociable really). Perhaps this is why?
If I want to try a range of ebikes I literally have to make a round trip of hundreds of miles, with no idea if what I find when I get there will be suitable, and only flat areas to try them out when I get there - so again no way to find out if they are suitable.
So, my point (finally) - manufacturers give us a break TELL us what are the optimum speeds at peak power for your motors when loading them - and how does that relate to their gearing. This is nothing to do with better or worse - just fitness for MY purpose (and everyone's is likely to be different).
As a final note - I know of the potential of gear drive systems such as the Kalkhoff's, but of the HUB motor driven bikes, which ones are best getting heavy loads up steep hills. Don't laugh, but is there anything out there that beats the heavy, slow, old tech., unfashionable, Powabyke commuter 24spd. for getting big loads up steep hills, without popping your knees out? If so I haven't yet found it. (I currently have a Wisper 905se on which I have had to modify the gearing, so don't anybody please tell me this is a better (steep) hill climber - it ain't. Great bike in many other areas though).
Looking forward to some interesting replies
Cheers, Phil

 

[flecc]

The standard Heinzmann motor has something in common, older design, brush motor, and it has it's peak power at about 8 mph, so bikes using that like the Estelle are good hill climbers.

Among newer designs, the Quando has peak power at around 8.5 mph and it's 576 watt peak motor is a Hall effect one, the broad spread of power making it a champion climber on motor only. Unfortunately it's a single gear folder, so not much good for a rider working with it, making it unable to cope with a 20% since the single gear is too high for the rider at that steepness. And no, it can't readily have gears added.

The eZee F series are very powerful, but again they have a rather high peak power speed, meaning that below about 8 mph they just stall, best kept to around 11 mph or more which is impossible for any other riders other than athletes on a 20% or steeper.

All the other British legal hub motor bikes are like the Wisper 905se or less able on motor hill climbing power.

The Chinese influence is critical in this, and I'm reliably informed that they don't cycle up hills, thinking that out obsession with that is distinctly odd. I must admit that of the huge number of photos I've seen of cycling in China, I've never seen anyone hill climbing, though I've seen them pushing bikes up hills.

Another factor is that the bikes are designed for world markets, and in the USA and some other places they have to do 20 mph. That presets the designed peak power point higher than is suitable for our market.
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[Steveb63]

Hi

It's big, heavy and expensive but my gazelle easyglider gets me to work and back over the route shown below quite happily.

It's a solid bike that came with all the bells and whistles and hasn't let me down in the first few months

I often feel like it should go faster on the flat (I'm often above the assisted speed on the flat) - but then on the very steepest bits when i'm down in second or third I'm still able to pedal quite comfortably - and fit I aint! not yet anyway!

http://www.pedelecs.co.uk/forum/attachments/electric-bicycles/256d1208988039-panasonic-system-power-delivery-explanation-route-work.jpg

Steve H

 

[flecc]

But that's a Panasonic motored bike Steve, Phil specifically wants a hub motor bike that's suited to hill climbing. That brings another set of problems.

 

[Phil the drill]

The Quando has a 20" wheel I believe. I presume this means that when you say the motor is geared to max power @ 8.5mph the same motor fitted to a 26" wheel would be giving max power at just over 11 mph - which puts the motor into a similar design category to most of the other Chinese hub motors?
I heard a rumour that Powabyke were supposed to releasing some brand new models soon, I wonder if they will keep within similar design parameters for the motor, or whether they will also opt for a more common off the shelf design with similar characteristics to most of the other hub motored bikes. It will be interesting to see.
Are the Heinzmann 24v or 36V?

 

[Phil the drill]

I heard the comment from someone that Powabyke changing to lithium battery power and aluminium frames was like putting carbon fibre on a tractor. In fact although it won't improve speed much, shaving 12Kg off the weight has got to be a considerable help on the hills and given its good performance here in the first place I can certainly see the sense of it. Perhaps I should have stuck with the old stuff I knew for most of my commuting...

 

[poppy]

Let me start by saying that Phil has summed up very eloquently the concerns and doubts of prospective buyers. Many of you may know that I had a clone of the Wisper 905. And precisely because it was a clone it had many defects. Sent it back after using it for 2 months. It had two main problems: motor stalling and unreliable battery.
I´m sure the original doesn´t have those problems.
But once you knew the weaknesses and took then into account, it was a very good bike -all around- for the first 15 km. Fast, good climber. If you look up where i live you´ll find nice hills in a 10 km radius. When the motor stalled all i had to do was switch off, wait a min. and switch on.
Now I´ve got a BH e-motion +Panasonic. Flecc is more than aware of it! As Tony warned me, it´s a different style of cycling. You have to work harder and it´s slower. But it´s lighter, more manageable. You set the pace. Seems more stable. And good range:I did 56 km on my first discharge, always with power on and mostly on the top power mode.
Even now I can´t say which one I prefer. Luckily, thanks to a prior mistake I don´t have to choose one or the other. I have both type of bikes. So it is the Wisper type for business and the Pansonic type for pleasure.
I am discharging the BH battery for the second time. I´ll do it on top mode all the time to get an idea of the minimum range.

 

[flecc]

The Quando has a 20" wheel I believe. I presume this means that when you say the motor is geared to max power @ 8.5mph the same motor fitted to a 26" wheel would be giving max power at just over 11 mph - which puts the motor into a similar design category to most of the other Chinese hub motors?

Yes, the Quando has a 20" wheel, in fact the Torq 1 was born out of it. The Quando motor was put into a 28" wheel to make a fast bike, but of course it's hill climbing was very poor.

Powabyke are about to disappoint you I'm afraid. Although the current alloy bikes have lithium options, the new bikes comimng later in the year are different. I believe they will have Hall effect motors of 400 watts peak power, so more of a mainstream medium powered design.

The Heinzmanns were both 24 volt and 36 volt systems, but they are settling on 36 volts now with lithium batteries.
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[Phil the drill]

Ah. Powabyke is a letting the side down a bit now then. If thats their plan prospective buyers are probably best to save their pennies and buy a Powacycle......(unless the Powabykes are a lot cheaper than they were).
Looks like the Heinzmann motor fitted in a lightweight tourer could be a good route (I have a ridgeback meteor which might make a suitable receipient). Do you know if any of the other motor conversion systems (for example the cytronex or alien (or any others I don't know of)) have similar characteristics?

 

[flecc]

Ah. Powabyke is a letting the side down a bit now then. If thats their plan prospective buyers are probably best to save their pennies and buy a Powacycle......(unless the Powabykes are a lot cheaper than they were).
Looks like the Heinzmann motor fitted in a lightweight tourer could be a good route (I have a ridgeback meteor which might make a suitable receipient). Do you know if any of the other motor conversion systems (for example the cytronex or alien (or any others I don't know of)) have similar characteristics?

Not the Powacycle for hill climbing, that's the lowest powered system of the lot.

The Alien and Nano (Cytronex) systems are both medium powered. The Nano motor is efficient and a good climber, but not in the brute power Powabyke slogging way you are thinking of. In bikes like the Cytronex it seems to be a motor best suited to working with a reasonable cyclist, not having moped like abilities. The Heinzmann is much more like the usual Powabyke motor, and just as heavy.

The ones I mentioned are it, I know of nothing else with those older design climbing characteristics.
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[frank9755]

The other obvious option would be Crystalyte (available from ebikes.ca - good overview of range and details on performance characteristics there) - which has some very powerful motors in the range, but are also heavy.

Alternatively, a Suzhou Bafang motor (the type used in the Quando and Wisper) might work if you got the 185 rpm version, which is geared for a 28inch wheel, and put it in a 26 inch (or smaller) wheel. If you're willing to take a risk on their reliability (and reports from the Cytronex guys are encouraging), a 160rpm Tongxin motor in a smaller wheel would also have reasonable torque while offering a better cycling experience.

Frank

 

[bode]

New Powabyke

Powabyke are about to disappoint you I'm afraid. Although the current alloy bikes have lithium options, the new bikes comimng later in the year are different. I believe they will have Hall effect motors of 400 watts peak power, so more of a mainstream medium powered design.
.

Maybe Phil should have a word with Powabyke HQ. I was recently able to try a prototype of one of their new bikes (I don't really know any details except that it was rather in the Wisper etc. style). Its hill-climbing abilities were certainly on a par with their old tanks, especially as it was about half the weight. The lithium battery was one of those disguised as a water bottle, but with only about half the capacity of the older ones.

 

[flecc]

Maybe Phil should have a word with Powabyke HQ. I was recently able to try a prototype of one of their new bikes (I don't really know any details except that it was rather in the Wisper etc. style). Its hill-climbing abilities were certainly on a par with their old tanks, especially as it was about half the weight. The lithium battery was one of those disguised as a water bottle, but with only about half the capacity of the older ones.

That sounds like good news as it means they may not have internally geared the motor too highly, which is Phil's worry. It was also my concern since it appeared to be following the "me too" school of design. It will certainly need to be a better climber than the 905se if it's to match the old "tanks".
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[emotivepete]

Looks like the Heinzmann motor fitted in a lightweight tourer could be a good route (I have a ridgeback meteor which might make a suitable receipient).

Phil,

This Ridgeback looks very similar to the Estelle Sport. The Sport is best known in its Speed variant but hill climbing, UK road legal variants are available.

All components found on the Sport. whether Speed or E-bike/Pedelec variants, are available in kit form to fit to other suitable bikes such as the Ridgeback.

The hill climbing motors top out at around 14mph in 28" wheels and, as Flecc has already posted see their peak pulling power at around 8mph.

 

[john]

Maximum Thrust

To go uphill, what we need is thrust. The more we have, the steeper we can climb. So, if you want to know what hill you can climb you just need the maximum thrust in Newtons (F), total mass in kilograms (m) and the following formula (ignoring friction):

slope (%) = F x 10 / m (10.2 to be more precise)

e.g. if you have a thrust of 100 Newtons you can push 100 kg up a 10% slope

To find out how much thrust a hub motor will produce you just divide its torque by the wheel radius (in meters).

e.g. a 33 N-m motor in a 26 inch wheel will produce 100 Newtons of thrust and so climb a 10% slope

Of course you can add more thrust by pedalling and go up a steeper hill.

If you apply more thrust than the slope requires, you will accelerate until the thrust inevitably drops to match that requirement plus rolling and air resistance.

To compare hill climbing ability of e-bikes, we should ask for either the maximum thrust provided by the motor, or (for those with a throttle) the maximum slope that the bike can climb without pedalling for a given weight of rider (say 70kg).

 

[emotivepete]

To compare hill climbing ability of e-bikes, we should ask for either the maximum thrust provided by the motor, or (for those with a throttle) the maximum slope that the bike can climb without pedalling for a given weight of rider (say 70kg).

Thanks John,

The Heinzmann hill climbing motor (179rpm) I have suggested is rated at 53 Nm and 14% hills in 28" rims. For comparison standard (road legal 189 rpm) Heinzmann motors are rated at 43Nm or 12% hills.

The Speed version (290rpm) is rated at 35.9Nm or 7.7% hills

Hope this helps

Pete

 

[MaryinScotland]

I have a standard Heinzmann motor in an Estelle Comfort bike, with 26" wheels. Today I had a go at the only hill in Oxford which rates a singe arrow on the OS map (>14% slope). I had a load of shopping aboard, and including me, the bike was carrying 89 kg. I supplied moderate pedal power, not straining by any means, dropping through the gears as the speed dropped. On the steepest bits, speed never went lower than 8 mph, in second gear, and the bike wasn't struggling. I'm happy with that, given that that is not the special hill-climbing motor. (Although, if I understand it correctly, by choosing the 26" rather than the 28" model, I should have improved torque but slightly lower max speed.)

A few years ago I had the 24V Heinzmann kit built into a Dawes street bike with 700C wheels. I tried the same hill on that combo, and although I got up it, I had to do a lot more work myself. I don't know whether the difference is due to the present 36V motor, or the wheel size.

Mary

 

[flecc]

So, if you want to know what hill you can climb you just need the maximum thrust in Newtons (F), total mass in kilograms (m) and the following formula (ignoring friction):

slope (%) = F x 10 / m (10.2 to be more precise)

The trouble with this is that climb speed isn't taken into account in an informative way, and for that reason I prefer to calculate using peak net power in watts in an equation including mass and climb speed.
.

 

[john]

The trouble with this is that climb speed isn't taken into account in an informative way, and for that reason I prefer to calculate using peak net power in watts in an equation including mass and climb speed.
.

We could use the same formula, taking thrust at peak power and that would give a kind of 'optimum' climbing ability. I guess that is the figure you work to and a good one for practical use.

We can find thrust from power in watts (P) and speed in mph (v) with:

F = 2.24 x P / v

which then gives:

slope % = 23 x P / v / m

(watts, mph, kg)

 

[flecc]

Yes, that works well John. I've just got into the habit of using my present equation since I have the fixed factor and main metres per second speeds in mind at any time, so for me it's the lazy option.
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