the 4 tea light & flower pot heater I did my first instructable on a year or so ago has proved too large to use in a cold frame to keep it frost free. This is a quickly produced heater that uses a single 8 hour duration tea light as fuel.
Step 1: Materials
8 hour tea light.
tin can it fits in.
larger diameter tin to use as a lid.
Step 2: Tools
Small hack saw.
quite a bit of miss use of tools happened here a pair of pliers might have made things safer but I got away with just fingers without cutting myself which is a serious risk without the pliers.
Step 3: Construction
using the chisel (abuse of tool a dremel would have been better) I cut 3 pairs of slots about 15mm apart and evenly spaced around the base of the tin. I then cut through the base of the tin with the hack saw between each pair of slots. then I folded the tabs in at 90° forming a stand for the tea light and air vents at the same time.
using the metal shears I cut 3 pairs of slots down from the top of the tin and folded the tabs down flush inside the tin. so forming the exhaust vents. (in hind sight it might have been better to fold them down the outside)
Step 4: Operation
drop the tea light into the can and light.(it might not be clear in the image but there is a gap all around the tea light between it's case and the can) Invert the larger tin over the top this reflects the heat back down (otherwise the heat from the flame will just rise) & acts as a radiator surface.