Effort or Speed?

Electrically assisted bikes, trikes, etc.
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Mick F
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Effort or Speed?

Postby Mick F » 25 Jun 2020, 8:54pm

Seen a few cyclists on electric bikes round here.

There's a hill on the lane that is a bit of a pig to a cyclist. It's one of those hills that you come to whizzing away in top gear, then the hill starts gently and you change down, then soon you're into granny ring, then into the bottom-est gear you have to get to the top.
Not a long hill, but it gets steeper and steeper and steeper as you go up it.
Concave maybe.

The electric cyclists come along and gracefully crest the hill.
No effort, no heavy breathing, no changing gears to speak of, and effortless and simple.

I understand that electric bikes are limited to 15mph, but below that you can climb hills using electricity rather than leg power.
This makes everywhere "flat".

If they are limited to 15mph in "assist", and that any speed over that is unassisted, why don't they un-assist up the hills when you put more effort in?

Why can you go up a steep hill at a speed less than 15mph on full assist?
Mick F. Cornwall

stodd
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Re: Effort or Speed?

Postby stodd » 25 Jun 2020, 9:36pm

To get speed up a hill needs power. Legal pedelecs are limited to motors with a nominal power of 250w. The word 'nominal' there is very open to interpretation. It is meant to be the power the motor can deliver consistently/continuously. Many so-called 250w motors can easily deliver 750w for the length of a small or even medium length hill. Such motors are often sold as 250w in UK/EU, and the same motor as 350w in UK because it is legal and sounds more powerful.

There is nothing in the regulations to say what power can be delivered at what speed; as long as the maximum assisted speed is 15.5mph and the nominal power is 250w or under that is OK. The limitations are then technical. Generally the higher revs a given motor runs at the more power it can generate; up to some point where power falls off quickly. That point can be adjusted by varying the gearing and winding details of the motor; so you can have a motor good at hill climbing slowly or going fast on the flat. Can the motor deliver power at lower revs? If the motor is at the crank it benefits from the gears the same way you do; that helps it deliver more power at high motor revs but lower speed.

Also, may e-bike cyclists ride with motors that are not technically legal by the 250w/15.5mps rules.

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al_yrpal
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Re: Effort or Speed?

Postby al_yrpal » 26 Jun 2020, 9:43am

Mick,

The simple answer is a pedelec goes at the speed you pedal at and the gear you are in. If you select turbo theres way much less effort. Your speed is a function of how much the motor is giving you and how fast you are managing to turn the pedals. My bike has the Bosch Performance Line motor which is the most powerful. Around here there are some hills that I can only just pedal up in turbo mode in the bikes lowest gear, they are real stinkers. No way anyone can fly up them, my legs are pretty strong. I always ride in the least battery draining mode Eco, and I step up to Tour mode for any hill only switching in more assistance to Sport or Turbo if I need to. Changing down on the derrailieur at any point makes things easier but slower.
From observation I would say 'non cyclists' seem to ride in turbo all the time and go about half my speed. Unlike me, they arent trying to maintain fitness. I seek out hilly terrain and go long distances to keep my fitness up.

Al
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Re: Effort or Speed?

Postby Oldjohnw » 26 Jun 2020, 9:50am

Like Al said. On max power and lowest gear I have still on a couple of occasions had to get off and push.

When I started in got 49 miles on a battery. Ok now get up to 100 because of the humannimput. But I still cannot glide up steep hills. Modest hills I do get up with reasonable ease.
John

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Re: Effort or Speed?

Postby Cyril Haearn » 26 Jun 2020, 9:58am

You should try one Mick, that is the best way to find out
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Re: Effort or Speed?

Postby simonineaston » 26 Jun 2020, 10:02am

I have such a hill at the end of my commute (or used to, anyway...). I've learnt that there's no point in changing down in anticipation of the steep portion, as years of regular bicycle riding had taught me - indeed I stay in a gear that would be way too high were I without the electric assist. I understand that its all to do with torque. The maximum torque that the hub motor * can produce is available from the instant the motor starts turning, thus as I approach the super-steep hill, having negotiated a tight turn up a short section of footpath, I'm travelling at walking pace. The hub motor doesn't flinch - indeed if the surface is at all greasy, it'll readily break the front tyre's grip momentarily. It will dish out all that torque, providing I keep rotating the pedals, even gently. Once on the straight section, I pedal as hard as I can, and between us the motor and me - whoosh, up the hill I go, flying past all other cyclists, twiddling away in their lowest gear. It's a bit embarrasing, sometimes!
* I forgot state the bloomin' obvious - that is, the reason the motor can do this 'cos it's an electric motor... don't ask me why and how 'leccy motors can produce max. torque the instant they start to rotate, but they can! Compare with a typical car diesel motor (max torque at 3,000 rpm)... I think it's something to do with the availability of the power - that is the current is all there, in the coils, from the get-go, whereas an internal combustion engine has to build up speed in order to increase the amount of fuel available to burn.
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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Mick F
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Re: Effort or Speed?

Postby Mick F » 26 Jun 2020, 11:50am

Thanks for the replies, guys.

Maybe I'm asking my question in the wrong way.

I understand that the electric assist is there for you irrespective of how tough the hill is.
I get the impression that riding one allows you to put the power of your legs at a constant level.
The more power required to get you and the bike up a hill, the more power comes out of the battery, whilst your legs are giving a constant power which means that the hills for you, don't exist.

This is the way I've witnessed these bikes.

Only on Wednesday, I was riding in the Helston area and a chap on an electric bike was flying along up a long gentle hill. I couldn't catch him up even doing my level best in the hot 30deg sunshine. At the top of the hill, I caught him up easily, and I seem to have this feeling that his speed was constant throughout. This made the hill non-existent to him.
Mick F. Cornwall

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Re: Effort or Speed?

Postby Oldjohnw » 26 Jun 2020, 12:00pm

A car has power but it requires gear changes on steep hills. Sometimes even struggles. A more powerful car will climb up without missing a beat. A little car might need work on the driver's part.

I guess cycling is much the same. Whilst all (legal) bikes cut out power supply at 15 mph, power can vary. I can fly up a long gentle hill if I maximise power. A strong cyclist will pass me on the level. Of course, if I constantly maximise power I will run out of battery much more quickly. It might not matter on a short run. It matters greatly on a long run.

I consider that my assistance is not meant to do the work. Rather it has the effect of making me feel stronger than I actually am.
John

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Re: Effort or Speed?

Postby simonineaston » 26 Jun 2020, 12:06pm

which means that the hills for you, don't exist.
Correct.
I'm in an unusual position, in that I ride both a 'leccy bike and a "manual" bike. I can certainly tell you that the difference is pretty much down to hills. When I'm riding my Brompton, I don't thumb the motor control when on level ground or going down any sort of gradient, and I will reserve its use for going up hill. The steeper the incline, the more juice I apply. When I'm on the Moulton, the only way I can compensate for the extra effort required is to change down the gears. It's when I'm cycling on the Moulton and going uphill, that I realise how much help I get from my mate Mr Volt!!
ttfn, Simon in Easton
(currently enjoying a Moulton TSR & a nano Brompton...)

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Re: Effort or Speed?

Postby kwackers » 26 Jun 2020, 12:19pm

It was always about the wind for me.

Wind is a speed and energy sapper, assisted bikes kept the average speed up although I did feel guilty passing all the struggling cyclists particularly on the Liverpool waterfront where the wind frequently whips up to 30+ mph.

I always rode my e-bike with a decent amount of assist - the point of it was to reduce my commute time not to help me out with exercise, I get plenty of that anyway.

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Mick F
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Re: Effort or Speed?

Postby Mick F » 26 Jun 2020, 4:08pm

Seems I'm correct then.

I have two very different bikes: a heavy laborious non-aerodynamic power-sapping Moulton, and a light and fast 531c Mercian.
I ride Moulton mostly as it's more versatile, but having ridden the heavy laborious non-aerodynamic power-sapping Moulton for ride after ride, then go off on Mercian, I find it amazing how easy the hills are. I fly up them and fly along generally! :D

On thing I've noticed about eBikes, is that they're all heavy and laborious - except for the electric assist. I never see a lightweight sporty bike with dropped 'bars and a motor, as they're all sit-up-and-beg MTBish and chunky.

Why are they all so heavy?
I know you can covert any bike, but why are the complete eBikes always heavy and ungainly contraptions?
Mick F. Cornwall

Jdsk
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Re: Effort or Speed?

Postby Jdsk » 26 Jun 2020, 4:36pm

This sort of thing?

Image

Jonathan

Oldjohnw
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Re: Effort or Speed?

Postby Oldjohnw » 26 Jun 2020, 5:40pm

https://www.ribblecycles.co.uk/ribble-e ... l-e-sport/

Ribble have several lightweight bikes.
John

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Re: Effort or Speed?

Postby stodd » 26 Jun 2020, 5:52pm

Mick F wrote:Seems I'm correct then.
Why are they all so heavy?
I know you can covert any bike, but why are the complete eBikes always heavy and ungainly contraptions?

As post above shows, not all so heavy and ungainly. If you only want a small a amount of help that you'll only need on the hills it is easy to make a bike with a small hidden battery and keep the weight down; the range will be great with a fit rider because the motor is hardly ever used. There are quite a few of those about, but it remains a somewhat niche market because for most cyclists that want that style of riding a non-e bike is lighter and cheaper.

When you get to less sporty bikes the battery needs more capacity; and hence heavier, bigger and more difficult to hide. The weight doesn't matter too much because the motor will overcome it (*) (**). The apparent ungainliness doesn't matter because it's a utility and pleasure item, not a fashion item.

(*) There's a bit of a conundrum here as the heavier it is the more battery you need so the heavier it is so .... Luckily its a convergent series, so even when you've fitted all the comfort and convenience extras it converges to 25kg.

(**) The weight is actually more of an issue when NOT riding it

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Re: Effort or Speed?

Postby wirral_cyclist » 26 Jun 2020, 11:09pm

Oldjohnw wrote:https://www.ribblecycles.co.uk/ribble-endurance-sl-e-sport/

Ribble have several lightweight bikes.


I ride with a few friends with Ribble ebikes and most of them struggle a bit at junctions as they forget to change down and then they can't spin the cranks easily enough to get assist :shock: