This post describes an improved large fuel port and a fuel stick lifter to make the combustion hotter and make fuelling easier in Miniature Dome Stove.
Background to the Miniature Dome Stove improvements
In my previous post on the Miniature Dome Stove, I discussed the possibility of adding a larger fuel stick port and fuel stick lifter. This was to improve the power of the combustion by reducing ‘air skip’ over the top of the fuel sticks and encouraging airflow under and through the sticks and charcoal bed. The larger port will also allow the stove to use lager and more convenient fuel sticks with less preparation effort.
Here is a link to an Instagram video of the Miniature Dome stove .
Design of the fuel stick lifter. A fuel stick lifter, by necessity, when deployed, would significantly reduce the already small (40mm dia), fuel loading aperture in the Miniature Dome Stove. The aperture already greatly restricts the number/quantity/size of sticks that support the combustion.
However, in the same post, I also discussed the possibility of having a bigger fuel stick port to increase the number of sticks that can be involved in the combustion. This increase should be able to more than offset some or all of the fuel loading capacity that is lost by using the stick lifter. The combination of both changes may make the stove even better.
Increase in the fuel loading area. Increasing from 40 to 50mm diameter (the biggest port that can fit in the wall of the fire dome) may not at first seem very much. However, this change in diameter increases the area available for fuel sticks by 56%. This also means that the companion fuel sticks can be thicker. For example, the diameter for a pair of sticks can go from 2*20 to 2*25mm or 15+35mm and still fit side by side across the fuel port.
Note: Having one large stick as the fuel supply is a tempting idea. However, from experience, it does not sustain good combustion in such natural draft stoves. Splitting into two or four parts and loading as a ‘tight bundle’ improves the sustainability of the combustion. However, while camping with ultralight gear, this is not practical. The better alternative is to feed in the separated parts of the same sticks when they have been split into several parts and loaded in somewhat random order. The sharp angular surfaces irregular gaps between the stick greatly enhance the combustion.
Fuel preparation with larger sticks. I find that it is easy and more efficient while camping to break large fuel sticks over-my-knee or under my boots. Sticks up to 25mm dia sticks are easy to comfortably break this way.
Also, larger sticks can be; cross-cut with an ultralight saw, broken with the aid of a rock crevis or the fork of a tree etc.
These thick stick portions can easily be split with a knife to quickly and efficiently make solid and sustaining fuel sticks. “Many such Eucalyptus sticks, when fresh, dense and energy-rich, even oblige by splitting as they are broken. I may make a brief post on this just to shame all these carriers of; axes, knives and macho weapons of destruction.”
Modification of Miniature Dome Stove with a large fuel port and a fuel stick lifter
The experimental stove is a bit ugly as I made it out of a previous experimental Pudding Bowl Stove. I put extra 40 and 50mm dia holes, adjacent to one another in the wall of the fire dome. Then I placed stainless steel foil covers under the two holes in the top of the fire dome to prevent excessive air entry through them.
Note: “I used this pudding stove because it was a useful experimental step toward my ideal stove “Also, I am a materials conservationist or a tightarse, depending upon your perspective”. Anyway, it was a ‘dead-ended design’ without a good cooktop.
I also had another test to do with this fire dome with four holes in it. Can you guess what it might be? It could be the subject of another post.”
I made two little holes in the fuel slide to act as pivot points for the curved fuel stick lifter wire. The hard wire was curved to fit the bottom of the stick slide when in the down position. When in this position it nestles against the edge of the 50mm dia cone that connects the fuel stick slide to the fuel port. This means that, when lowered, it does not obstruct the normal entry of ends of new fuel sticks and allows the maximum loading of fuel sticks when required.
The fuel stick lifter has a bent arm that can be used to raise and lower the lifter. The arm has a hook on the end that can be clipped over the fuel stick slide to hold the wire in the half-raised position. When the wire is raised the fuel sticks are lifted so that more air can enter under the sticks and into the charcoal bed. The lifting action also closes the ‘air-skip-gap’ above the sticks and encourage more airflow below the sticks.
The lever can be lifted and rotated forward to raise the lifter to the top position with maximum airflow under the sticks and into the charcoal. It also minimises the ‘air skip’ over the top of the fuel sticks.
Results
I first tested the stove with the enlarged fuel stick port without the fuel stick lifter and the combustion was quite persistent, and fuel sticks were much easier to load, particularly thick sticks with lumps, bumps and splinters. However, I was rather disappointed that the stove was not as hot as I would have liked.
My disappointment dissolved when I deployed the fuel stick lifter. It still allowed easy loading when the fuel stick lifter was ‘down’. Then the raising the lifter closed the ‘air slip zone’ and encouraged air entry under the sticks and into the charcoal bed. Raising the lifting wire made the stove burn considerably hotter. It meant that hot burning with easy fuelling could be achieved by using this fuel stick lifter.
This Instagram video of the stick lifter deployment shows the subtle change in combustion that can be achieved with the simple fuel stick lifter wire. The response is a little slow to fully describe within a 1min video.
Discussion and conclusion on the Miniature Dome Stove modification
Enlargement of the fuel port allowed the loading of more fuel and thicker sticks. It also allowed the deployment of an effective ‘three-position’ fuel stick lifter. The two changes make the Miniature Dome Stove easier to fuel and allows the stove to burn hotter with larger fuel sticks and make better use of the charcoal bed to sustain stronger pyrolysis of wood gas.
I think this modification/s tends to make the air entry and mixing through the sticks and charcoal bed just a bit more like my ‘J-burner stoves, but without the problems of charcoal choking, failure of stove draft and reverse burning that is associated with them.
The simple bent wire fuel stick lifter worked amazingly well, considering it was the first prototype. The design of the wire means that it holds in place while in use, but it is easy to remove for backpacking.
With the larger fuel/air port, the stove’s combustion seemed to benefit by covering the 20mm hole in the fire dome. I have welded a tiny long handle to the cover so that it can be deployed and removed safely when the stove is very hot.
I could hear a distinctive increase in the chuffing sound of the burner and an increase in the flame intensity each time I closed the opening.
I think the two improvements have probably optimized the design of the Miniature Dome Stove. Or, maybe there are just one or two more improvements? So keep looking.
Tim
Addendum
A big improvement in simplicity and performance has been made with the development of the KISS Stove in the link below.
