Wattbike
- Thread starter 10mph
- Start date
In a gym....?? I can afford a pedelec but I don't think I could stretch to a gym membership!
I began to perspire at the very thought!
Indalo
ps "Wattbike" sounds to me like it would make a good title for a new magazine about electric bikes.
I began to perspire at the very thought!
Indalo
ps "Wattbike" sounds to me like it would make a good title for a new magazine about electric bikes.
I'm not too sure I'd trust in those claims, especially where friction loadings are used which by their nature wear and vary.
Find yourself a suitably consistent hill and accurately measure it's gradient in this way.
Then with your bike equipped with it's accurately calibrated speedometer, climb the hill under pedal power only at whatever force you want to apply, maximum effort or comfortable effort, noting the steady speed of climb in each case.
Now stand on your scales at home dressed as you rode and carrying your bike, noting the weight in old or new money.
Tell me the weight, speeds and gradient and I'll tell you your wattage outputs accurate to within 10 watts.
.
Interesting calculator, on my old purely human powered bike it appears i was consistantly outputting 80-100 watts, with peaks of up to 300w for less than a minute, and i consider myself fitter than average.
They say top pursuit track riders can hit 2000w from a start, although that tails off throughout the race and they finish outputting about 350w. It shows you just how sueprhuman the likes of Chris Hoy and Bradley Wiggins are!
They say top pursuit track riders can hit 2000w from a start, although that tails off throughout the race and they finish outputting about 350w. It shows you just how sueprhuman the likes of Chris Hoy and Bradley Wiggins are!
Thanks for the points.
I have done a web search for accurate bike ergometers, and the Wattbike seems to be the thing that professional cyclists and other athletes are getting. There are claims of accurate calibration of the chain force load cell by a defined procedure and accuracy. If one believes these claims then could be better than the average gym's unit displaying calories burnt or something vague like that with no set up calibration procedure.
I want to measure my steady ouput for one hour. The idea is you go to a gym (hopefully for a free trial day, or at worst pay a one hour usage fee) and ride at 80 watts for an hour and see how you feel at the end of it.
Over 15 years ago I used to run long distances. So I learnt in pratice that if you want to achieve very long distances in the shortest time the best strategy was to run at nearly constant speed, cutting back to provide roughly constant effort on the hills. The greater the distance the slower you set out. Biking is a bit more complictaed because we have much greater effect from hills, but similar principles must apply in relation optimising the rider's power output time profile.
Also I know that if I can achieve 80 watts for an hour, then I could knock it back a bit and achieve 2 hours effort at around 70 watts. There are curves published of typical fall off with duration.
Now the probelm is I dont have any hills that go on steadily at 1% or whatever for 10 miles. In fact gradients are changing all the time. So that is why I thought a calibrated ergometer might be more useful than my bike.
I was out on Monday measuring the gradient of my nearby steep hill, and isnt it amazing, Flecc, your 2007 posting describes exactly the method I was using with a 75cm long spirit level and a spring loaded tape measure! (The problem with pedelecs forum is there is so much material only accessible through a search engine with a very unfriendly captcha system - I wish we had an easy to use index of useful topics) Much to my surprise this hill which I thought had a uniform gradient over one stretch has one section of 13% - no wonder the lactate builds up on it! By eye looking down the gradient I can now locate the steeper section, but it is not very obvious.
NRG: Smashing calculator. I will compare its formulae with my spread sheet formulae. Incidentally I am going to measure my crossectional area by taking a head on photo.
Streethawk: If you are fitter than average and output 80-100watts, maybe I should be aiming at 60 watts since I am undoubtedly less fit and quite frequently get overtaken by ladies when I am walking, once even in heels! Alas walking speed now tends to slip below 4mph for anything over a mile or two.
I have done a web search for accurate bike ergometers, and the Wattbike seems to be the thing that professional cyclists and other athletes are getting. There are claims of accurate calibration of the chain force load cell by a defined procedure and accuracy. If one believes these claims then could be better than the average gym's unit displaying calories burnt or something vague like that with no set up calibration procedure.
I want to measure my steady ouput for one hour. The idea is you go to a gym (hopefully for a free trial day, or at worst pay a one hour usage fee) and ride at 80 watts for an hour and see how you feel at the end of it.
Over 15 years ago I used to run long distances. So I learnt in pratice that if you want to achieve very long distances in the shortest time the best strategy was to run at nearly constant speed, cutting back to provide roughly constant effort on the hills. The greater the distance the slower you set out. Biking is a bit more complictaed because we have much greater effect from hills, but similar principles must apply in relation optimising the rider's power output time profile.
Also I know that if I can achieve 80 watts for an hour, then I could knock it back a bit and achieve 2 hours effort at around 70 watts. There are curves published of typical fall off with duration.
Now the probelm is I dont have any hills that go on steadily at 1% or whatever for 10 miles. In fact gradients are changing all the time. So that is why I thought a calibrated ergometer might be more useful than my bike.
I was out on Monday measuring the gradient of my nearby steep hill, and isnt it amazing, Flecc, your 2007 posting describes exactly the method I was using with a 75cm long spirit level and a spring loaded tape measure! (The problem with pedelecs forum is there is so much material only accessible through a search engine with a very unfriendly captcha system - I wish we had an easy to use index of useful topics) Much to my surprise this hill which I thought had a uniform gradient over one stretch has one section of 13% - no wonder the lactate builds up on it! By eye looking down the gradient I can now locate the steeper section, but it is not very obvious.
NRG: Smashing calculator. I will compare its formulae with my spread sheet formulae. Incidentally I am going to measure my crossectional area by taking a head on photo.
Streethawk: If you are fitter than average and output 80-100watts, maybe I should be aiming at 60 watts since I am undoubtedly less fit and quite frequently get overtaken by ladies when I am walking, once even in heels! Alas walking speed now tends to slip below 4mph for anything over a mile or two.
I think you guys may be capable of more than you think. From my Website:
As part of their efforts at lobbing people into space in the 1960s, NASA researched human performance and came up with a variety of useful numbers on many activities, including for cycling. Their wattage output figures for "healthy men", presumably meaning fit males from about 25 to 45 years old given their astronaut profiles at the time, showed the following outputs:
300 watts for about 10 minutes continuous.
200 watts for about 1 hour continuous.
100 watts for about 5 hours continuous.
.
As part of their efforts at lobbing people into space in the 1960s, NASA researched human performance and came up with a variety of useful numbers on many activities, including for cycling. Their wattage output figures for "healthy men", presumably meaning fit males from about 25 to 45 years old given their astronaut profiles at the time, showed the following outputs:
300 watts for about 10 minutes continuous.
200 watts for about 1 hour continuous.
100 watts for about 5 hours continuous.
.
In that case the calculator must be way off, or the figures i'm feeding it are. I know my hub motor on the cyclamatic is meant to be 250w and comfortably does 16mph on the flat on throttle. I can match that with the throttle turned off, for a couple of miles at least, and i can sprint to over 30mph on the flat for a few seconds.
No it is not as I keep on pointing out!
These 200 or 250 watt ratings are notional only for legal purposes, they have absolutely no technical significance whatsoever.
The average hub motor sold in the UK such as yours typically has a steady output capability of around 400/450 watts, your 24 volt one likely to be about 400 watts. The most powerful hub motors on 36 volts can be very much more powerful. For example, the gross steady output capability of my eZee Torq/Quando motor is over 700 watts with a short term peak capability of just over 1000 watts. It's net power output capability onto the road is over 550 watts.
The lowest powered hub motor bike on the market still pumps out over 300 watts net power.
The actual output capability depends on the motor revs, which on a hub motor means the road speed. Typically the maximum output comes in at about 8 to 10 mph and drops off slightly thereafter.
Manufacturers arrive at the "legal" figure by assessing an average power output over time when on the road, not what the motor is capable of at best.
.
Last edited:
D
Deleted member 4366
Guest
10mph, If you're already a gym member, use the Wattbike. I'm sure it will give an accurate repeatable result because that's what they're designed to do, so It'll give you exactly what you want. If you're not a gym member, be careful: It can be expensive to join and check the agreement carefully because some are difficult to cancel.
Yes, it is a problem that often frustrates me too. That's why I try to maintain a folder of typed and link entries from my past postings, plus postings from others who may have left the forum which I re-post at times with credits.
.
10mph,
This is the cheapest Power Meter that I can find that might fit your requirements for power usage.
Dave
CycleOps Powertap Pro Power Meter wCervo : Bikes | Mountain Bikes | Road Bikes| Winstanleys
Power Meters
This is the cheapest Power Meter that I can find that might fit your requirements for power usage.
Dave
CycleOps Powertap Pro Power Meter wCervo : Bikes | Mountain Bikes | Road Bikes| Winstanleys
Power Meters
Thanks. Nice gadget. I note that over the last decade this sort of thing has come into use in the Tour de France. So even proper cyclists need to monitor their power output and cant just rely on the feel of their body, heart rate, and their brain. Perhaps it is the trainer who mostly needs the power data for the post race analysis.
At more than £600 for these, I think I would instead pay for a go on a Wattbike at first, since I think I only need a one off measurement. The closest Wattbike I have found so far is in Evesham. No reply from my email to Wattbike HQ yet.
I have a nice 80 minute ride which I did 2 years ago on my push bike. 4 laps of a reasonably flat 3 mile loop. I have the GPS traces, therefore all speeds and timings. The last lap showed a slight slowing, and I remember that I was getting tired, so it will give a good idea of the steady 1 hour performance in terms of speed on my push bike. I will look at the numbers more closely but I think it does come out at around 80 watts for typical air resistance and rolling resistance.
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