Is 250w enough power for modest speed up steep hills

Electrically assisted bikes, trikes, etc. that are legal in the UK
axel_knutt
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Re: Is 250w enough power for modest speed up steep hills

Post by axel_knutt »

Nearholmer wrote: 16 Jun 2022, 12:59pm Assuming that the 14% is devoted to the challenging bits of the route, you will be getting more low to medium intensity exercise, and less high intensity exercise. I’m no sports physiologist, but I understand both to be of value in different ways, so you are losing something, while gaining something else.
I've spent the last 11 years limiting the intensity of my exercise out of necessity, and I've lost all my fitness as a result.

Schnohr et al: Intensity versus duration of cycling, impact on all-cause and coronary heart disease mortality.
Copenhagen City Heart Study

“we found a significant inverse association between cycling intensity and risk of all-cause and coronary heart disease death, but only a weak association with cycling duration.”
“Our findings indicate that the relative intensity, and not the duration of cycling, is of more importance in relation to all-cause and coronary heart disease mortality. Thus our general recommendations to all adults would be that brisk cycling is preferable to slow”
“I'm not upset that you lied to me, I'm upset that from now on I can't believe you.”
― Friedrich Nietzsche
Nearholmer
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Re: Is 250w enough power for modest speed up steep hills

Post by Nearholmer »

I've spent the last 11 years limiting the intensity of my exercise out of necessity, and I've lost all my fitness as a result.
Some, not all, I venture to suggest, because if you’d lost it all then low-medium intensity cycling would be beyond you.

My bro does hold a degree in sports physiology, so I’ll ask him about that Copenhagen study, because the advice I received from a cardiologist was that the overall health benefits of cycling, including age-appropriate spells of intense effort, so vastly outweigh any specific cardio risk that comes with it that the cardio risk isn’t worth worrying about except in the case of a person with specific health conditions.

The age-appropriate bit is important though, because, until that consultation, I hadn’t realised that flogging yourself for prolonged periods at >90%HR once you are beyond about 60yo does indeed cause a significant increase in cardio risk. The chap was a keen cyclist himself, just passing that age, and was telling me how he was in the process of swapping from being a roadie to being a path-tourer for that very reason. He said that bashing up the odd hill was OK, but belting along at near-top HR for ages at a time wasn’t. We wasted a lot of NHS time talking about cycling and comparing bike choices!
Jdsk
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Re: Is 250w enough power for modest speed up steep hills

Post by Jdsk »

Nearholmer wrote: 16 Jun 2022, 1:46pmMy bro does hold a degree in sports physiology, so I’ll ask him about that Copenhagen study, because the advice I received from a cardiologist was that the overall health benefits of cycling, including age-appropriate spells of intense effort, so vastly outweigh any specific cardio risk that comes with it that the cardio risk isn’t worth worrying about except in the case of a person with specific health conditions.
I don't think that they're contradictory. But it's going to take need some precise wording to explore that in detail.

And it's always difficult in this forum because people taking intense exercise are grossly over-represented in comparison to the whole population.

Your general assertion is fine.

Jonathan
Dingdong
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Re: Is 250w enough power for modest speed up steep hills

Post by Dingdong »

We're all heading to the box, might as well enjoy ourselves every pedal turn of the way
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Cugel
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Re: Is 250w enough power for modest speed up steep hills

Post by Cugel »

Dingdong wrote: 16 Jun 2022, 3:58pm We're all heading to the box, might as well enjoy ourselves every pedal turn of the way
Troo, troo - but there are various modes of enjoyment on a bike, some of which don't require your eyeballs to be a-pop at all times. Personally I try to get all the different pleasure-modes into one ride.

For example, today I did a 47 kilometre ride of 960M up (and the same down) through Brechfa Forest. There was lots of grinding up and lots of fleeing down - very satisfying; but also some pootling whilst enjoying views. When the heart rate began to rattle my ribs and my quads turned to a painful jelly, I switched on the electric motor for a brief time or three, since I knew that if I didnae, there would come a time at about 5K from home when grovelling would have to be done. I only like grovelling on the ladywife's back wheel and she wasn't there today.

*************
A habit of pushing yourself to max effort, heart rate and muscle thrust at least twice a ride does seem to have benefits to the body and its workings. But so does the pootle, although that's not just because of having a bit of a rest but also because one can "bathe" in the gorgeous countryside - good for the mentals. Mind, the bathing might be difficult if you have to cycle around central Birmingham rather than Brechfa Forest. :-)

Cugel, using it so as not to lose it.

PS I still hope to drop dead of excess thrust whilst on a bike trying to beat the ladywife up a hill somewhere. Better than the lingering kind of demise on a perch in a gimmery, eh!? She says she'll just heave my corpse into a ditch, where the red kites will feast on it, lucky birds.
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
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Dingdong
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Re: Is 250w enough power for modest speed up steep hills

Post by Dingdong »

Rotting in a ditch is not a bad way to peg it. Though unfortunately illegal in these heavy times. Of old, my ancestors liked to be laid out on mountain tops, surrounded by stones and artefacts what they liked.

Their bones to be picked clean by crows, and of course the Eagles. What remained would be put into the river. This was of course a very long time indeed before Hotel California (yuck!)
stodd
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Re: Is 250w enough power for modest speed up steep hills

Post by stodd »

Dingdong wrote: 17 Jun 2022, 6:55am Their bones to be picked clean by crows, and of course the Eagles.
Problems in some cultures in India where bodies were left to be picked by vultures, as vultures die out.

https://india.mongabay.com/2018/02/decl ... 0carcasses.
(also many similar articles around)

(Sorry, but not sure how that relates to getting up a steep hill on a 250w motor.)
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Cugel
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Re: Is 250w enough power for modest speed up steep hills

Post by Cugel »

stodd wrote: 17 Jun 2022, 9:40am
Dingdong wrote: 17 Jun 2022, 6:55am Their bones to be picked clean by crows, and of course the Eagles.
Problems in some cultures in India where bodies were left to be picked by vultures, as vultures die out.

https://india.mongabay.com/2018/02/decl ... 0carcasses.
(also many similar articles around)

(Sorry, but not sure how that relates to getting up a steep hill on a 250w motor.)
The red kites around here (a sort of Welsh vulture) do have a worrying habit of doing a few circles low overhead as one wanders in a field or goes more slowly up a steep hill on a bicycle. Can they see something of my body language that says: about to go phut and lie still enough for long enough to enable extensive pecking of the juicy parts (those eyeballs look tasty and are popping out)?

Perhaps speeding up a bit - courtesy of an electric motor - whilst showing less stress will suggest that the pedalling one is not yet about to become available for pecking at?

Eventually the beady-eyed rascals depart the scene with a disappointed air. But one day ....

Cugel, just a large juicy morsel, from the perspective of those beaky aeronauts.
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
Bonzo Banana
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Re: Is 250w enough power for modest speed up steep hills

Post by Bonzo Banana »

Cugel wrote: 31 May 2022, 12:27pm
stodd wrote: 31 May 2022, 9:06am
mattsccm wrote: 30 May 2022, 9:05pm It needs enough power to get the rider to the top at the speed of a normal, not especially fit non ebike equiped rider. So, as in my case yesterday, on the local 25% hill, about 4mph.
We are talking bikes with a bit of boost for the less fit here, not a new form of motorised transport.
Absolutely.

As a matter of interest, do you have a hub drive or a crank drive motor? Most hub drives are getting really inefficient by the time you slow to 4mph. eg our XF07 is down to just over 40% efficient at 6mph and only just over 40% at 4mph.

https://ebikes.ca/tools/simulator.html? ... h&grade=13
Now that is a highly relevant statistic! It suggests that a mid-motor drive through the gears is going to remain much more efficient (assuming you have low enough gears) at very slow or just-rideable speeds. For some, that would be a primary consideration when deciding on which type of motor system to go for.

Of course, I myself always ride at 37mph so don't need the motor. :-)

Cugel, a little liar.
Efficiency varies at different times with all motor systems. Mid-drive motors deliver their power through the drivetrain so already you have 2-3Nm lost through the chain itself and then inside the mid-drive motor you have a series of nylon cogs and sometimes a belt that loses power again and they still lose efficiency on hills which is common to all motor types. When a Bosch motor is peaking at 800W a huge amount of that power is lost in heat and of course such high wattage is inefficiency in itself peaking far higher than other motor types to achieve its higher torque. That simulator tool is done by Grin Technology and they do a video explaining motors and their efficiencies and from memory there isn't a lot in it between motor systems although its clear they have a preference for direct drive motor hubs overall because of their engineering superiority with regard reliability and lifespan and lack of commercial exploitation of consumers with very proprietary parts you see on many pre-built mid-drive ebikes, not such an issue with kit mid-drive motors as those typically use more open components and don't require specialist frames that are expensive and sometimes difficult to replace. The general rule of 10Wh per kilometre is applied to all motor types. I.e. a 600Wh battery should give you about 60Km or 40 miles range with normal use. A direct drive hub motor with regen enabled and only used for hills and using regen down hills could achieve maybe 200 miles range on one charge but if instead you used it all the time at full power with no regen and didn't assist the bike clearly you would be sub 20 miles. Its not just about the range though, a hub motor is independent of the drivetrain so can make the drivetrain last around 3x as long as a conventional bike because now climbing hills is split between the drivetrain and the motor independently. Contrast that to mid-drive where drivetrains can wear around 3x as fast as a conventional bike because all the motor's power and the riders power are delivered through the same chain.

Also direct drive is the only motor system that can use statorade/ferrofluid to allow direct connection cooling between the stator and outer shell. So not only does direct drive have by far the best cooling anyway because of its larger surface area but using such fluid increases that cooling significantly by about 40% so it means the motor runs far cooler at all times and can perform long hill climbs more easily. So while geared hub motors and mid-drive may have more torque for hills they will be thermally restricted in power far sooner for longer hills. So a direct hub motor maybe 30-45Nm in torque going up a hill and a geared hub motor maybe 12-65Nm and the mid-drive 40-95Nm depending on models that is not the full picture if the motor reduces power as the temperature increases.

https://www.youtube.com/watch?v=dxJe_gygRGU
Airsporter1st
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Re: Is 250w enough power for modest speed up steep hills

Post by Airsporter1st »

Nearholmer wrote: 16 Jun 2022, 12:59pm Assuming that the 14% is devoted to the challenging bits of the route, you will be getting more low to medium intensity exercise, and less high intensity exercise. I’m no sports physiologist, but I understand both to be of value in different ways, so you are losing something, while gaining something else.
Very true, I’m sure - although the ebikemotion system doesn’t eliminate the high intensity effort, just ameliorates it (Orbea’s slogan is “Just Enough Assistance”). I still have to work hard on the hills and arrive at the top breathing hard. The only real difference is that I don’t have to get out of the saddle or, worse get off and push!
Jdsk
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Re: Is 250w enough power for modest speed up steep hills

Post by Jdsk »

Cugel wrote: 17 Jun 2022, 11:13am
stodd wrote: 17 Jun 2022, 9:40am
Dingdong wrote: 17 Jun 2022, 6:55am Their bones to be picked clean by crows, and of course the Eagles.
Problems in some cultures in India where bodies were left to be picked by vultures, as vultures die out.

https://india.mongabay.com/2018/02/decl ... 0carcasses.
(also many similar articles around)

(Sorry, but not sure how that relates to getting up a steep hill on a 250w motor.)
The red kites around here (a sort of Welsh vulture) do have a worrying habit of doing a few circles low overhead as one wanders in a field or goes more slowly up a steep hill on a bicycle. Can they see something of my body language that says: about to go phut and lie still enough for long enough to enable extensive pecking of the juicy parts (those eyeballs look tasty and are popping out)?
The Oxfordshire red kites draw the line at grey squirrels...

Jonathan
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Cugel
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Re: Is 250w enough power for modest speed up steep hills

Post by Cugel »

Airsporter1st wrote: 18 Jun 2022, 12:38pm
Nearholmer wrote: 16 Jun 2022, 12:59pm Assuming that the 14% is devoted to the challenging bits of the route, you will be getting more low to medium intensity exercise, and less high intensity exercise. I’m no sports physiologist, but I understand both to be of value in different ways, so you are losing something, while gaining something else.
Very true, I’m sure - although the ebikemotion system doesn’t eliminate the high intensity effort, just ameliorates it (Orbea’s slogan is “Just Enough Assistance”). I still have to work hard on the hills and arrive at the top breathing hard. The only real difference is that I don’t have to get out of the saddle or, worse get off and push!
It's an easy assumption that an e-bike just makes it all easier. In practice it can do so of course - but it can make it just as hard or even harder!

Although I resisted an e-bike for some years after the ladywife got hers, a couple of borrows of her electrified steed intrigued me, as I came back from riding it more knackered than when I went out on my unpowered bike. I did try to minimise the use of the motor; and her e-bike is 7kg heavier than my racy bike, but ..... .

Thinking on those experiences, as well as about those of the rides I've done since getting my own e-bike about a month ago, I realised that I hadn't stopped outputting my own max sustainable power up the Welsh hills, whether I had the motor switched on or not. In some ways, being able to go faster up hills than when on a non e-bike encourages you to try even harder yourself. You know that the whole climb will take a lot less time than heretofore so you can afford to give it "fool gas" as there's less risk of blowing up before the top. In fact, no risk really as you can still progress well up the last hundred yards or so, if your legs & lungs insist "no more", as that e-motor is still working.

Adjusting the Fazua motor profiles for its three modes is a good way to tailor the e-assistance to the sort of riding you want to do. There are many possible settings that can reduce the assistance to the minimum, demand a lot from your legs before you get lots from the motor or .... allow you to input only 75 watts when you've got close to the bonk with the motor adding 150 or 200 watts to get you the last three miles home.

One way of accelerating an increase in fitness is to do plenty of max-heartrate intervals. Another is to cycle far enough to get close to bonking. Normally you have to limit that sort of riding carefully as you don't want to be knackered & bonked 15 miles from home. You might be tempted to call for the taxi-of-shame! So instead, you can use an e-motor and only feel motor-shame, which no one but you and the motor need be aware of. :-)

Cugel, playing like a big kid with a new toy.
“Practical men who believe themselves to be quite exempt from any intellectual influence are usually the slaves of some defunct economist”.
John Maynard Keynes
Nearholmer
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Re: Is 250w enough power for modest speed up steep hills

Post by Nearholmer »

but it can make it just as hard or even harder!
One option you might consider is a “constant effort e-bike”. This would have a combination of software, gearing and control arrangements so that it could be set to demand any given constant effort from the rider.

On difficult bit, the battery and motor would top-up above rider effort, and on downhill bits the rider would be required to continue providing constant effort, which would be used to charge the battery, and if that wasn’t enough to require all of the constant effort, because the down-grade was too steep, the mechanical brakes would be applied to add drag for the rider to work against.

To get interval training, you would simply toggle between effort settings.

I rather doubt that such a bike exists, but as a mostly-retired engineer I find imagining how it would all work a useful distraction from the rain.
stodd
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Re: Is 250w enough power for modest speed up steep hills

Post by stodd »

Nearholmer wrote: 18 Jun 2022, 1:34pm One option you might consider is a “constant effort e-bike”.
Nice idea, I think that could work well for flat and uphills; and probably be easy to engineer with a tweak to torsion controller software.

It doesn't seem worth it for downhill. It seems generally accepted that regenerative breaking is too complex to be worth it on typical crank drive or geared hub motors, and direct drive motors have lots of problems of their own (weight and inefficiency). Of course, just because something is generally accepted doesn't make it true; it would be great if somebody came up with an effective regenerative breaking. I think you will find considerable consumer resistance to the idea of applying the brakes harder on downhill so the rider has to work harder. Maybe even that though; people are willing to pay out for bicycle exercise machines.
Nearholmer
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Re: Is 250w enough power for modest speed up steep hills

Post by Nearholmer »

Couldn’t regen be implemented by having the motor drive permanently connected to the wheel, and the pedals connected into the drive via a centrifugal clutch?

I still like the idea of making people pedal hard downhill. It has a certain perverse appeal.
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