[Stoves] HydroFan etc

[Crispin Pemberton-Pigott]

Dear Geoff

This is what was proposed by someone (not me) a few weeks ago.  I think the 
basic problem is the amount of weight required to give perhaps 1/2 a watt 
for moving air, at the right pressure and volume.  The clock uses quite a 
lot of air at a low pressure.  A stove, as far as we see them, uses 
relatively high pressure and low volume, often controlled quite accurately.

John Davies in South Africa uses a tall chimney (2.7 to 3 meters) to create 
the necessary air flow, and quite unusually, controls the draft by allowing 
in excess air to reduce the chimney gas temperature and also to break the 
'suction'.  Obviously a chimney has $ consequences.  But at least his system 
does not need batteries or a fan.

What I have seen shows that the fan has to be proportioned for the right 
airflow range and pressure which will probably be a squirrel cage rather 
than a propellor type fan.  I have a squirrel type fan hissing under me as I 
wrote this on my laptop.  It has a volume/pressure profile very different 
from the power supply fans we are (mostly) talking about.  It is likely that 
a big weighted bellows (as suggested by another contributor) would be a 
better and probably more efficient device than anything spinning.  Makes 
sense, right?  It also involves periodically lifting a weight to recharge 
the system.  Maybe old inner tubes attached together?

Anyone near falling water could use a trompe for a free and continuous 
supply of compressed air!

Regards
Crispin


----- Original Message ----- 
From: "Geoff Thomas" <wind at iig.com.au>
To: <stoves at listserv.repp.org>
Sent: Monday, January 01, 2007 11:23 PM
Subject: Re: [Stoves] Stoves Digest, Vol 6, Issue 46 message 1, HydroFan etc


Hi Crispin and all, I wonder has anyone considered using a device to power 
their cookstove fan, -
that is the old method for cuckoo clocks, - which consisted very simply of a 
weight on a loop of
string or chain, the weight pulled down and powered the clock, - every week 
of so you had to lift
the weight back up to the top of the loop, but for a stove just one charge 
would be enough, - ie
you could use all the energy in the slowly descending weight to do a charge, 
then simply lift the
weight up again for the next charge, and the shaft from the output, - 
presumably two cogs to gear
it up, could simply be a piece of string as when it is wound around and can 
not form any knots
because of the tension, will turn as if it was solid, - like a tow-along 
turbine on sailboats.
Hopefully of help?
Cheers,
Geoff Thomas.
Advanced Wind Technologies.
Australia.