Does More Power Sometimes Decrease Rider Satisfaction?

General Discussion about electric bicycles.

Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby Sunder » Wed Dec 19, 2012 10:11 pm

dogman wrote:I agree, it's just that it's hard to compare the two. The electirc has this thing where it's full torque is nearly instant, then drops off with speed. While ICE tends to rev up to it's full torque. Once you have just 4kw of that instant torque, it's pretty fun. Once rolling, say 50 mph, the laws of physics dictate that if the drag of both bikes is equal, the power used to go 50mph is equal. Both may be using less than thier full hp to do that 50 mph, but in many cases the ICE bike will have more power to go faster if the rider chooses if it's above 150cc.


Here's the thing though - I could drag and win against 1000cc bikes in my Evolution lancer (11.2 second quarter mile car - and that was with a dodgy clutch, On paper, it should have been about 10.8). But I was never under the illusion that my car was faster than a Yamaha R1. Why? Because if an R1 rider came even close to to using the power they have available, they'd flip the bike, and be on their arse on the asphalt.

It's not the bike that's the issue - You can dump the clutch near the peak torque and have peak torque from the drop of the flag. It's just that most riders are not skilled and/or confident enough to do that.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby maydaverave » Thu Dec 20, 2012 6:24 pm

I have a low power 1000 watt bike. Its a great commuter for my small town and as time goes by I find myself going slower on it. I probably average about 18mph on an across town ride. About a year ago I bought a 24" inch specialized bmx bike with the intention of making a wheelie stairclimbing burnout hooligan bike. I fell in love with it the way it handles and jumps. I couldn't imagine electrifying it unless I could do it under five pounds. A bmx bike you can't bunnyhop is no bmx bike at all. That being said if I could put about a 1000 watts on it under five pounds with battery in backpack taking 25 mph sharp curves, improved off road capabilities, and endless mile long balanced wheelies would be amazing.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby pendragon8000 » Sat Dec 22, 2012 8:00 am

I got a 29 inch large cross country bike and put a hadron kit from hyena on it. Handles well although I doubled its wright to 30kg . Using the cycle analyst I have set the Max power to 1.2kw (less than half its Max output) with no pedaling at full throttle I get just over 55 KpH and I pedal on acceleration and cruising to get up to 60kph. I move with traffic well and get in front of trucks and busses often. Being able to cut across vertically any wear is a big advantage over a motor bike , going on foot path to get to tragic lights and be in front of slow trucks and busses, also great for trails, silently blast up hills and cover heaps of ground really fast without being totally destroyed from pedaling my ass off for an hour or 2.

I've had the bike going for a few weeks and still haven't gone faster than 65kph. The front wheel bounces as I pedal hard taking off with power limited at 1200watts so there's not much point in having more than that for general comuting IMO.

Having 3kw is really overkill for computing except for those situations where you may want to power out of a tight situation. But for my own safety I behave like a push bike pretty much.

Off road 3kw is cool for power slides and wheelies.

1 last point to consider is the question says power not volts or amps so... how many volts is too much - depends on required top speed, and amps - acceleration/hill climb.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby Arlo1 » Sat Dec 22, 2012 10:47 am

I found setting my 3sp switch to the 35km setting a relaxing way to get around in the less driven streets. It was a VERY relaxing zen kinda feeling and its like I was one with the world... But when I turned onto a busy road with a 50-60km speed limit 35 km/h is not fast enough and will get you and the drivers pissed off. So I turned to the hi speed setting and ripped though traffic like I was on a sport bike. Each setup has its place. I actually like the option of going slow and saving energy you get more time to check out the scenery especially in the summer when the scenery has skimpy clothes on ;)
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby Ken Taylor » Mon Dec 24, 2012 12:31 am

Thanks for the debate.

The thread is showing 760 views and 33 comments. Generally I can expect a comment per thousand readers so this is an extraordinary response. However, only 70 people thus far clicked across to the original article at http://blog.urremote.com/2012/12/what-w ... -when.html , a bit less than 1 in 10 thread readers. That suggests some comments are a reaction to other comments rather than the initial argument which was along the lines that with a little bit of assist you could win the Tour de France but with 500 W you'd have a dissatisfying motorbike. NeilP spoke for many:-
NeilP wrote:
Ken Taylor wrote:Do experienced ebike riders always get more satisfaction from more power?

:P YES YES YES YES YES!!! :D

and some like:-
maydaverave wrote:I have a low power 1000 watt bike. Its a great commuter for my small town and as time goes by I find myself going slower on it.

had a different definition of low power than I'd intended.

Kraeuterbutter at viewtopic.php?f=28&t=37785#p587951 is somewhat sceptical of the power requirements of Endless Sphere aficionados.

However, there was some with plenty of experience of high power bikes who saw merit in low power bikes which I'd define as not more than 2-3 times more power than pedalling. For example:-

chvidgov.bc.ca wrote:I've experienced this when I recently put a "Cute" motor on a nice light aluminum framed roadbike.... I've been very happy with the very bikelike experience


Jeremy Harris wrote:I started out with a fair bit of power, but find that the ebike I like best, and ride most, is the light one with the low power motor. The reasons aren't that straightforward, I think.


melodious wrote:....That article does have merit. A bike w/motor takes the physicality of the experience away. I'm really hesitant to taint my last true bike into a motorized vehicle. :|


Some commented on the psychology of power:-

dogman wrote:A great deal depends on the goals of your ride. As goals change, the mental attitude changes.


rocwandrer having never ridden an e-bike felt unqualified to add to the discussion but pointed out that:-

rocwandrer wrote: The vast majority of my riding time is purely recreational, with the destination being the departure point.


which is probably pretty common and my favourite version of cycling. After presenting the reasons he claims:-

rocwandrer wrote:If the benefit from adding pedal power does not FEEL proportionate to the effort, it is much harder to put in that effort....That all matches with Ken's hypothesis that if there is enough power on tap with the electric assist to make the human contribution feel less critical, or to make the return for extra effort feel too small, it is will psychologically difficult to even acknowledge that there is more in reserve in the human power side's controller.


Following a link provided by rocwandrer led to John Tetz's graph on the physiology of power.

Image

So with the benefit of all that input I can refine the original hypothesis:-
1. Uncontroversially - lightweight is always better.
2. Engineering, psychology and physiology all have to be optimised for satisfying electric bikes.
3. Like in robotics, electric assist on bicycles suffers an uncanny valley. A small amount feels good and the rider always wants more but at some point the criteria for satisfaction shifts so as that as the rider descends into the valley, despite desiring more,increased power reduces satisfaction. As power increases further the rider climbs the far side of the valley and more power again increases satisfaction until the desire is finally satiated at multiple kilowatts.


If there is merit in the hypothesis it follows that giving a rider more power on demand isn't always going to provide the most satisfaction. On the left side of the valley you might do better by reducing rider control. Some possibilities are:-
1. Run the motor at the point of maximum efficiency for whatever speed the bike is travelling and rely on the rider to add sufficient power to maintain speed. This would increase range for a particular battery size.
2. Hill flattening. Sense the grade and provide power to offset a portion of the riders weight on hills. If the portion was 100% a hill would feel no different to the flat. Especially good for people that are overweight.
3. Don't provide assist until the rider is putting in more effort than it takes to walk then add more as the rider adds more. This might encourage the rider to increase their effort rather than reduce it. Most of the assist would be spent overcoming air drag in this case which is non optimal for range.
4. Use heart rate as a sensor input. If the rider is not working at 80% of maximum they don't get any help but the more they go up the more help they get.
5. Don't provide much assist at the start of a ride but add assist as the time goes by in the proportion that the rider tires.
6. Vary the algorithm depending on the purpose, for example a ride for pleasure and exercise versus a desire to arrive at the office sweat free.


A good algorithm would be one that encouraged the rider to exercise more rather than motivating them to minimise effort.
Last edited by Ken Taylor on Mon Dec 24, 2012 4:51 am, edited 2 times in total. View post history.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby mythprod » Mon Dec 24, 2012 1:52 am

I have a less scientific and more straight-forward mindset when it comes to ebikes - faster is better. At least so far it has been. My bike's a commuter. The faster I can get to work (and home) the better. I have no issues being motivated to help the motor out by pedaling as I would find it weird not to pedal anyway. I have a 1000W motor with a 48v 20ah battery and it can get me up to 30mph on flats and with pedaling I can get up to 35 mph.

I will say the only thing I don't like about the bike is its weight, but it's certainly not enough to bother me most days - especially now that I'm used to it. I joy ride on the bike also (did today in the freezing cold) and find I like having the power there if I need it, but since I use a throttle, I take what I need. If the battery runs out, I still pedal home (did a couple of weeks ago when my charger went out and had to pedal home - was quite wore out and sweaty manually pedaling a bike that's 40lbs heavier than it used to be before I converted it).

I do want to build a second ebike and haven't decided yet what I want to use. It would be disappointing to have a motor that's half the power / range but it would also be nice for it to be a lighter bike (something the wife could ride and not feel intimidated by its weight).

So for me - speed is paramount. Lightness is a luxury (lighter is always better of course, the reason LiFePO4 is better than SLA in my mind) and a great perk if you can get it and not compromise on the first priority - speed.
Last edited by mythprod on Mon Dec 24, 2012 1:52 am, edited 1 time in total. View post history.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby Jeremy Harris » Mon Dec 24, 2012 6:04 am

Ken Taylor wrote: A good algorithm would be one that encouraged the rider to exercise more rather than motivating them to minimise effort.


This is key to the success of a lightweight assist system, rather than an out and out electric moped or motorcycle, I think. The best system I've ridden is the Panasonic bottom bracket drive. It's low powered, almost silent and rewards rider effort by using crank torque sensing (i.e. to get more assist you have to push harder!). The major downside of the Panasonic drive is that it was originally designed to meet the very restrictive Japanese ebike laws and has since only been modified to meet the similar EU regulations. This means that all assist stops at 25km/h, far from useful if you like riding fast.

Right from the very first ebike I built (a SWB recumbent back in 2008) I've wanted a nice torque control system. I've even played around with ways to sense this, using chain tension, but without getting any decent results. My ideal would be a "bionic bike", one that accurately sensed my muscle input and provided assist that was proportional to this, so effectively making me seem to be fitter than I really am.

To get what I think you're after (and, curiously, what I'd quite like) probably means using a bottom bracket drive that can take advantage of the gears, in the same way as the rider. There's no good reason why something like the Thun torque sensing bottom bracket, coupled with a torque driven controller, couldn't do this fairly well. Whilst the torque sensor and suitable controller could be fairly readily obtained, I have yet to find a nicely engineered and quiet running bottom bracket drive that could be added to an existing bike. Units like the GNG and Cyclone are fairly crudely engineered and far from silent, the Gruber is very expensive and the bevel gears whine quite noticeably, I understand.

The quietest drive I can think of would be something based on a near silent low power hub motor, like the Tongxin, with it's internal roller reduction drive. If this was housed in a nicely engineered housing with a short chain or belt drive to the existing chain ring, then it might form the basis of a decent low power assist system. The problem then becomes one of creating the right sort of control response to take rider pedal input from the torque sensor (filtering out the steady motor torque contribution) and providing just the right level of assist (perhaps together with some form of rider selected assist level to allow for fatigue).
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby hjns » Tue Dec 25, 2012 6:56 am

Ken Taylor wrote:So with the benefit of all that input I can refine the original hypothesis:-
1. Uncontroversially - lightweight is always better.
2. Engineering, psychology and physiology all have to be optimised for satisfying electric bikes.
3. Like in robotics, electric assist on bicycles suffers an uncanny valley. A small amount feels good and the rider always wants more but at some point the criteria for satisfaction shifts so as that as the rider descends into the valley, despite desiring more,increased power reduces satisfaction. As power increases further the rider climbs the far side of the valley and more power again increases satisfaction until the desire is finally satiated at multiple kilowatts.


While it may be a nice working hypothesis for whatever you are aiming at, it does leave unjustified some prior assumptions.

  1. light weight is always better - assumes that there is no limit to how far we can decrease the weight of an ebike. This is unfortunately not true, and a certain minimum weight but also a certain maximum weight usually will play a role in the equation. Therefore, I disagree with the "uncontroversially" part. Giving up the motor to save weight is like throwing the baby away with the bath water. At least, from an ebike perspective.
  2. satisfying electric bikes - assumes that there is one set of characteristics that identifies a "satisfying ebike". I disagree, and in the previous responses you may have seen that some people responded that they have different bikes for different purposes. Furthermore, by using ebikes and identifying their strengths and weaknessess for different purposes, the expectations of the owner changes, and thus more or less satisfaction may occur. If the expectation is to get some exercise, decreaseing power may well increase satisfaction. If the expectation is to enable a fast commute without sweating, increasing power will increase satisfaction. I think it is a mistake to lump these together.
  3. I disagree based on the above, due to the variety in expectations and thus the change in satisfaction. While you may see this nice U-curve, it is not representing the individual's needs. I would actually assume that if you would specify better the purposes of the various ebikes, and thus the possibility for satisfaction, you will almost always see an (inverted) S-curve. For exercise, you will end up with more satisfaction towards the light low power bike with excellent adjustment to human power input, whereas for high speed commuting, you will end up with more satisfaction twoards the high power more heavier bike, with excellent adjustment to other traffic.
Last edited by hjns on Tue Dec 25, 2012 6:57 am, edited 1 time in total. View post history.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby dogman dan » Tue Dec 25, 2012 7:30 am

Re reading your blog, don't forget that to match Chris Horners average output, you'd have to also have a motor system with 100% efficiency to do it with just 100w more. Plus, you'd also have to be able to match his maximum output at some points along the way. I bet a 500w system, often run at 200w would be closer to what you'd need. Bear in mind, on the hills, you might be getting no more than 300w out of a 500w throttle setting to the rubber.

I am of the opinion that less than 400w is fairly useless in hilly terrain for hubmotors. Though a mere 100w of assist is greatly appreciated, a lower power setup really needs to be through the chain to use less than 400w up a 5% grade. I have such a bike, but found it worked poorly because the original designers did not gear it low enough. Even on the largest rear sprocket, it's geared too high for really steep hills. Since it's a bottom bracket drive, I can't lower the gearing any either. It already has a big rear gear, and you can't change the front.
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Re: Does More Power Sometimes Decrease Rider Satisfaction?

Postby rocwandrer » Tue Dec 25, 2012 9:55 pm

dogman wrote:Re reading your blog, don't forget that to match Chris Horners average output, you'd have to also have a motor system with 100% efficiency to do it with just 100w more. Plus, you'd also have to be able to match his maximum output at some points along the way. I bet a 500w system, often run at 200w would be closer to what you'd need. Bear in mind, on the hills, you might be getting no more than 300w out of a 500w throttle setting to the rubber.

I am of the opinion that less than 400w is fairly useless in hilly terrain for hubmotors. Though a mere 100w of assist is greatly appreciated, a lower power setup really needs to be through the chain to use less than 400w up a 5% grade. I have such a bike, but found it worked poorly because the original designers did not gear it low enough. Even on the largest rear sprocket, it's geared too high for really steep hills. Since it's a bottom bracket drive, I can't lower the gearing any either. It already has a big rear gear, and you can't change the front.


It would be nice, but probably isn't realistic, to standardize discussions like this on output power when talking assistance power. Then the above might read more like "a larger motor might be required so that it is capable of putting out the burst power desired even at inefficient operating rpm". And so on...
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