[Stoves] Burning charcoal

[Lanny Henson]

I have been testing the simple two can stove
http://www.lanny.us/twocan.html, and I noticed that if I stacked charcoal
around a pipe to retain a hole in the center, that there was a small flame
above the hole. http://www.lanny.us/charf3.jpg. But when I used a steel wire
frame made from bucket handles http://www.lanny.us/charf1.jpg to maintain
approximately the same diameter hole that I got a larger, continuous flame
through out the burn. http://www.lanny.us/charf2.jpg
http://www.lanny.us/charf4.jpg.
I wonder why.
Lanny Henson