A blower fan is described for use with an ultralight blower stove. It can make the stove very hot, clean and able to burn damp fuel sticks. Why use a blower fan? Because it turns a few sticks into a powerful clean source of heat.
Hear the gentle roar in this short clip.
Initially, without a blower fan, my simple small wood-burning stoves for ultralight backpacking were smoky, slow to cook, difficult to start and failed to work adequately with wet, damp or green fallen sticks. It meant that my fuel was invariably sub-optimal when it was most needed for warmth, drying, hot drinks and food preparation.
Much later I discovered that Robert Jung and others from Coast and Mountain Walkers had been using improved versions of these wood-burning stoves for several years, using the natural draft formed between the walls of the stove body and the billy can. Robert Jung has documented tests and interesting observations with these innovative wood-burning stoves in his article. Twig stoves
Without knowledge of the above stove developments, I took another path. I simply added a blower fan to my stoves. It became ‘fire breathing dragon’ that could burn damp and wet wood. The blower made the stove consume more fuel, but eventually, the blower also provided the opportunity to make the stove smaller, hotter and cleaner and made possible many other stove design/functionality improvements including a second cooking position and the use of convenient long sticks for fuel that more than offset the higher fuel consumption.
For a detailed story of my stove development please see my full article Blower Stove Article.
Blower fan. I use Laptop fans (5V DC ~0.28A for the blower. They provide a more than adequate airflow to drive a powerful cooking stove when using damp wood for fuel. Although they are not designed for rugged outdoor use, they have given me years of service and many hot drinks and meals. I make a small modification to the fan cable by firmly anchoring it to the fan housing to protect the fine soldered electrical contacts from being pulled off their connections to the motor.
Blower manifold. I make a fan manifold (the connection between the rectangular blower fan outlet and the round air tube) from folded and welded stainless steel foil. This foil is only as thick as printer paper and seems quite fragile, but when shaped by rolling and/or bending and then joining by welding it is very strong and ultra-light. The manifold has an integrated and captive shutter that can be used to restrict airflow during the initial stove start-up, so the flame is not blown out like Elton’s ‘candle in the wind’. The shutter can also be used to regulate airflow to control ‘stove heat output’ and ‘temperature’, when used in conjunction with various fuel types and loadings (If you are interested, I discuss these issues in Stove Fuels And How They Influence Stove Performance And Survival )
Air tube/s. These are also made from stainless steel foil so that they break down into parts for easy pack up within the cooking pot along with all other stove parts. For my single pot stoves, there is no wing wall to control the flame and there is a risk of the stove flame being blown back to the blower and power supply. To help to keep the fan and battery out of harm’s way I provide an air tube extension tube. I also provide an alternative bent air tube that has the same effect (see below and also Air Extension & DragonHead).
LED snorkel light. The blower unit can also support a LED Snorkel Lighting Module that can be mounted on the fan housing and it shares the power supply with the fan and is described in snorkel-lighting-module/.
Fan motor survival. I use cheap laptop fans (not the quality that I would put in my laptop) because they are so cheap to replace if ever that is needed. I have melted one in my first prototype stove where it was just too close to the stove and it was connected with a short manifold that was made of highly conductive aluminium.
“Importantly, it still worked, and it did not diminish the euphoria of the moment when I discovered this fire breathing dragon.”
Also, I accidentally pulled the soldered power cable off the printed circuit board that is connected to the fan motor (solder and all). Luckily it happened near the end of a long trip. I have addressed the above issues firstly, making the fan manifold out of stainless steel that is much less conductive than aluminium. Secondarily, I added a long air tube/s to keep the fan and power supply further away from the radiant heat from the stove. Lastly, I mount the power supply on the fan manifold so there is no tension in the cable and I also strongly anchor the power cable to the fan body so there is no tension in the cable leading to the delicate soldered joints.
My field-tested fans have been exposed to dust, ash and rain and have periodically had the smoke pass backwards through the fan when it has been turned off and the wind has blown in in the wrong direction. They have survived all this and I am certain that they will go on for a lot longer.
Probably the worst risk is the fan being trodden on by bushwalking boots when someone stagers away from a campfire in a cloud of blinding smoke. The LED light is good protection in this regard.
“When I am on a long through hike with a group where we are largely dependant on the stove for most cooking I carry a spare fan (26 g), ‘just in case’. Refitting in the field is a bit fiddly but not difficult. No need for tools, it just requires good light, steady hands and a groundsheet to catch any fallen parts”.
Check out my little video of blower stove startup and boiling two pots of water.
Other blower uses. For the walker who does not even wish to carry a stove, the blower unit can be used to effectively provide a cooking stove by using some carefully selected rocks or a little hole in the ground (see Rock-N-Hole stoves.)
While I have focused on the blower as a part of an improved stove, I have also discovered that it is a useful tool for other purposes. It can be used as a handheld campfire starter, barbecue starter, running a charcoal furnace and a stump burner when used with a long extension tube (from household hard rubbish of course!).
Last word/s. The power supplies for the blower unit are discussed in Power Supplies For Blower Units.
Addendum. Since preparing this page I have developed a switching system to pulse the fan to extend battery life. In the same page, I also describe an automatic vent/valve to prevent smoke and flame blowback through the fan during pulsed fan operation.
Tim
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