[SEL] Attention Aussies - Austral Question

[Rob Skinner]

On Mar 8, 2007, at 2:53 AM, Patrick M Livingstone wrote:
> My engine is running its original mild steel primary coil but I do
> not have a starting coil in the lower chamber. Some of the guys  
> have been
> experimenting with various materials to try and stop the cooling  
> off problem
> of an unloaded engine. Some have tried replacing the coil by  
> filling the
> chamber with brass nuts.

Ok Patrick.  You opened the can of worms.  I'm gonna fling 'em all  
over the place.  It might take the PhD or the Nukular Scientist to  
clean up the mess.

I contend that changing the material or the configuration of the  
material is utter bollocks.

Consider the stock coil.  When the engine fires, the coil TAKES heat  
from the fire depending on a heat-exchange coefficient.  Then over  
the "miss" cycles, the coil gives up heat using the same  
coefficient.  Eventually there is a compression stroke, and the coil  
will still be giving up heat using the same coefficient.  The rate of  
heat exchange for a particular coil is dependent on the pressure in  
the coil case and composition of the gas in contact with the coil.   
These will be constant independent of the coil.

If we change the composition of the coil or the surface area of the  
coil, we can affect the rate of heat exchange.  BUT, if the coil  
TAKES heat more quickly, it will COOL OFF more quickly.

Furthermore, the mass of the coil is what, three grams?  The mass of  
the entire vaporizer is what, a couple kilos?  The mass of the coil  
is miniscule compared to the entire mass of the vaporizer.  The  
surface area of the coil compared to that of the entire vaporizer is  
equally miniscule.  Futzing around with the coil is an exercise in  
futility.

There you have it.  The Emperor has no clothes.

Rob
All enraged Roo Eaters, please send your complaints to  
helen at insulate.co.uk