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.