Walnut Shells & Corn Cobs in the SSM TLUD Prototype

This photo of 554 grams of walnut shells is from a recent test by Flip and Jon Anderson in the natural draft SSM TLUD prototype. The shells were cracked using an adjustable hand crank. Near the end of the burn, the fire died down and became smoky and then went out. Blowing through the primary air pipe, they were able to re-ignite the fire. 

As the shells burned, they compacted and formed a dense layer that had reduced the flow of primary air up through the shells. Five liters of water boiled in 25 minutes and the fire burned for another five minutes.

In a second test, they used 505 grams of larger shells, thinking that would allow for more air space between the shells. The volume was about identical to the previous test. The water boiled at about the same time. Two minutes later the fire converted to charcoal. 

Once the fire lit, Flip and Jon had reduced the primary air. By opening the primary air cap, the flames became strong again before going out. Using larger pieces of shell seemed to have been a good idea. 

Here’s a short video of the flames while the shells were burning, and then flames from the resulting charcoal.

In a recent experiment with corn cobs, 614 grams of cobs boiled water and kept it simmering over the resulting charcoal for more than half an hour.

We value their enthusiasm and careful reporting as they keep exploring the versatility of this experimental stove!