>> The point is that 100W will definitely feel like work, but normal reasonably
>> fit people can maintain that level for quite a while if the right muscles
>> are used in the right way (like walking).

Yes.
My 50 W and 100W figures were based on actual electrical output
figures from a pedalled alternator using a reasonably efficient
alternator.

> My inspiron 8200 laptop needs a 90W PSU. I should fit a traditional
> Sewing Machine treadle and keep fit while programming etc..

Sewing machine treadle would probably be VERY hard work at 100 W-=
maybe OK at 50 W.
Bicycle action is liable to be easier to make more power from.

> Does anyone sell this? Using a gym treadmill, cycle-machine or rowing
> machine seems so mindlessly pointless (Ok for Hamsters?). If I had the
> time, I'd rather hike the hills.

I intend to produce a commercial design for this requirement OR
identify existing products that do it cost effectively. My target is
third world* energy source where grid power is unavailable. Target is
probably 100 Watt . Much more is possible without much design effort
but I'll have to see if there is too much cost penalty in a higher
output - quite probably not.
(*  To use a perfectly good but now largely shunned term).

You can get a reasonable result without much effort - no great rocket
science involved.

Commercial units are on the market in Tanzania. I don't know the spec
or efficiency or how well built and they did not respond to my
queries. If they are doing well enough cheap enough I'd base my
intentions on their product, for middle African use, but chances are
that it doesn't meet spec one way or other.
Possibly they are the same as these with the alternator units hand
made in Nepal :-).
http://news.cnet.com/2300-13840_3-6242378-8.html

I used to do the controllers for these. (No, I've never met the lady pictured).
        http://www.treadmillwarehouse.com.au/index.php?fuseaction=product.zoom&bigpic=product_pic%2Flpictures%2FINF_ET_011.jpg&w=500&h=747&suppressLayout=1&title=INFINITI+VG+60
The alternators are good for well over 500 Watts, depending on how
fast you want to spin them.

I can achieve 500 Watts of output for a few seconds , followed by an
overwhelming urge to lie down for an extended period :-).

         Russell
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