Etiquette on hills

Electrically assisted bikes, trikes, etc. that are legal in the UK
hemo
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Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Etiquette on hills

Post by hemo »

mattsccm wrote: 6 Aug 2021, 12:22pm "There’s a legal limit to the Wattage assistance, for a road legal eBike ( I think it’s 250 Watts ). That would equate to a very useful speed on the flat, but rubbish on a steep, long climb. Of course, YouTube and other video sharing type sites are very good at instructing people, in how to get around / hack legal motors. That’s up to the riders in question I guess."
Nope. Other way round surely?
15mph isn't much cop on a nice flat road but being able to keep that up on a nice long steep hill is.

Motor wattage is 250w nominal and is it's rating and not it's max output power. For instance if you ran a 250w motor at 48v with 20a current it can output 960w from the controller and approx. 750w at the motor. There are no max output nmbers for pedelecs only that the nominal rating of the hub is 250w. The rating is that which the maker so wishes to rate it at.

On the Pedelecforum.de a trike/tadpole user modded his basic Bafang SWXK 250w hub motor to produce some 1500w power from the motor. Simply providing oil cooling internally and supplying 40a the hub produced nearly 2kw from the controller and successfully ran without overheating.
mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Etiquette on hills

Post by mattsccm »

What on earth is the above post on about? How does that relate to 15mph being a decent, or not speed?
:D
stodd
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Joined: 6 Jun 2018, 10:24am

Re: Etiquette on hills

Post by stodd »

mattsccm wrote: 7 Aug 2021, 1:48pm What on earth is the above post on about? How does that relate to 15mph being a decent, or not speed?
That post (and my similar one) was about the 250w limit (clarifying the point raised by you), and also relevant to the thread topic as power makes a big difference to hill speed and hence indirectly to hill etiquette. 15 mph is part of the same regulations but not that relevant to the thread topic. Very few legal ebikes can get near 15mph on a significant hill even with a strong rider; for many of us it's just nice to be able to get up it at all!
mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Etiquette on hills

Post by mattsccm »

Wasn't even questioning the 250w thing. Was disputing the idea that 15mph was a decent speed on a flat road.
stodd
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Joined: 6 Jun 2018, 10:24am

Re: Etiquette on hills

Post by stodd »

mattsccm wrote: 7 Aug 2021, 7:18pm Wasn't even questioning the 250w thing. Was disputing the idea that 15mph was a decent speed on a flat road.
There are lots of threads on that; this isn't one of them.
Grumpy-Grandad
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Joined: 2 Apr 2021, 11:25am
Location: Crewe, Cheshire

Re: Etiquette on hills

Post by Grumpy-Grandad »

kylecycler wrote: 5 Aug 2021, 5:59pm Clubmates who ride e-bikes in my local cycling group have explained to the rest of us that when we're climbing especially steep hills we need to keep out of their way and let them by, not hold them up, or at least not cause them to come down to our lowest speed, because below a certain speed the e-bike's motor will 'stall'. Maybe not quite the same as a petrol engine stalling but I think they just mean they'll eventually lose the power assistance and get stuck.

Those who ride e-bikes might be able to explain that better, but AIUI it's a thing.
Basically ..... the harder you pedal, the more assistance from the motor ..... if you are hardly pedalling i.e. slowly, you get little or no assistance ...... at least that the case on my Carrera Crossfuse ...... steep uphills I use Turbo mode and a low gear to keep up a good rhythm ..... I think you call it cadence?
Steve
stodd
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Joined: 6 Jun 2018, 10:24am

Re: Etiquette on hills

Post by stodd »

Grumpy-Grandad wrote: 8 Aug 2021, 10:53am Basically ..... the harder you pedal, the more assistance from the motor ..... if you are hardly pedalling i.e. slowly, you get little or no assistance ...... at least that the case on my Carrera Crossfuse ...... steep uphills I use Turbo mode and a low gear to keep up a good rhythm ..... I think you call it cadence?
Just to clarify, that is correct for torque sensor bikes, where the motor power is a multiple of the power provided by the rider. Typically from 50% (2/3 rider, 1/3 motor) on low or eco settings and 300% (1/4 rider, 3/4 motor) on highest setting. The exact numbers vary between models.

On cadence sensor bikes the power generated is more on/off depending on whether or not you are rotating the pedals at all; with the amount of power dependent on the settings.

Keeping the motor running at a good speed helps it motor to be more efficient; that is obviously easier on crank drive systems where the motor benefits from the chosen gear. With a hub drive you benefit from the good cadence in appropriate gear, but the motor speed depends only on the wheel speed. On either if the motor gets too slow efficiency drops, so you get slower, and efficiency drops more, and ... eventually you stall. If you want the see the power./efficiency effects in detail there are good graphs at https://ebikes.ca/tools/simulator.html. You may even get graphs for your own particular motor but in any case the overall shape is similar for different motors/drives. with the peaks coming at different speeds depending on motor/gearing.
Marcus Aurelius
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Joined: 1 Feb 2018, 10:20am

Re: Etiquette on hills

Post by Marcus Aurelius »

mattsccm wrote: 7 Aug 2021, 7:18pm Wasn't even questioning the 250w thing. Was disputing the idea that 15mph was a decent speed on a flat road.
This is exactly the reason why judging your effort from your speed is a bad idea. 250 Watts ( natural ) is a fair effort, for an average non-pro level cyclist, on the flat, for a sustained time. It could quite easily only yield 15mph on a flat road if the conditions dictated it ( a strong headwind, or they’re particularly heavy) for example. However, that’s a whole different topic, not for this thread.
But what I was actually originally getting at, is that 250W assistance, or 15mph legally limited speed, with just the electric motor, would ( almost certainly) be a very decent speed on a flat road, for the typical rider who actually needs a motor assist in order to enjoy their riding ( keeping up with groups they’re riding with and the like), as (for many reasons) they tend to have all the natural power ( power / weight ) of a potato clock normally. If pedelecs help them enjoy riding, and keep them riding, that’s got to be a good thing, right?
mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Etiquette on hills

Post by mattsccm »

And I was saying that 15 mph is too bloody slow for a road ride. I average that over 100 miles. Stuff how knackered I am.
Absolutely no relevance to the initial thread title but thats what a forum is for. :lol:
peterb
Posts: 392
Joined: 2 Dec 2017, 10:13am

Re: Etiquette on hills

Post by peterb »

Marcus Aurelius wrote: 18 Aug 2021, 1:47am
mattsccm wrote: 7 Aug 2021, 7:18pm Wasn't even questioning the 250w thing. Was disputing the idea that 15mph was a decent speed on a flat road.
This is exactly the reason why judging your effort from your speed is a bad idea. 250 Watts ( natural ) is a fair effort, for an average non-pro level cyclist, on the flat, for a sustained time. It could quite easily only yield 15mph on a flat road if the conditions dictated it ( a strong headwind, or they’re particularly heavy) for example. However, that’s a whole different topic, not for this thread.
But what I was actually originally getting at, is that 250W assistance, or 15mph legally limited speed, with just the electric motor, would ( almost certainly) be a very decent speed on a flat road, for the typical rider who actually needs a motor assist in order to enjoy their riding ( keeping up with groups they’re riding with and the like), as (for many reasons) they tend to have all the natural power ( power / weight ) of a potato clock normally. If pedelecs help them enjoy riding, and keep them riding, that’s got to be a good thing, right?
'they tend to have all the natural power ( power / weight ) of a potato clock normally' - that's quite insulting isn't it? 15mph is quite a low speed for a group of club riders on a leisure ride on a flat road.

edit: just back from the evening club ride - average speed 15.1mph over 20.55 miles. Not flat, but no big hills. On flat stretches the group were edging up to 19, 20, 21 mph. Not exceptional, just a group of average club riders out for an evening ride. Just the one riding an e-road bike.
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