Perry your pop-can-heater looks sweet.
Hope you have time to answer a few questions.
Any difference in your heating bill?
How many sq feet is it heating?
Do you have any plans that you can post?
What did you build your frame out of? Is that white paint or some type of covering on the frame? What did you use for the back of the frame? What about fire hazard?
I notice that your covering is not flat are your cans also in an arch to match your cover? Does it mater if it is flat or arched?
What did you make what appears to be a manifold out of?
Are each column of cans connected so that air enters in can #1 and works its way out at can #240 or does air enter each column at the bottom and exit at the top of the column?
What about toxic off-gassing from the glue, paint or other materials in the construction?
What do you do with the unit in the spring, summer months?
Thanks for your time.