Introduction: Wood Stove With Recycled Materials
I belong to a rural part of India and here we make use of wood stove as a source for heating and cooking. Usually, the stove is made of three clay bricks placed in a " c " shaped structure with an open end for wood insertion. These are simple and does not require much space but with these type of stoves a lot of energy is eliminated since a large portion of the stove is open and due to the heat eliminated in the form of hot smoke. And these are pretty messy, the ash which remains after burning cannot be contained properly. Now being a mechanical engineering student I have started lerning about boilers and superheaters and this intrigued me.I wanted to build a stove that will be helpful for my family and efficient.
In these Instructables, I am going to show you how to make a wood stove using a recycled LPG cylinder and fire extinguisher cylinder.
And yes I am using a fire extinguisher to provide better fire.
Step 1: Materials
Materials to be recycled
Steel plate 6mm thick
Steel strip 6mm thick
Square Steel bar
Arc welding machine
Drill machine and drill bit
Step 2: Where to Recycle the Materials From
I got most of my materials from a scrapyard but here I am listing possible ways you can recycle some of these materials.
Metal sheet and strip: I got these from a scrapyard it had rust all over it I had to remove the rust with the help of an angle grinder. I think these were used as steel flooring in some industry
Lpg cylinder: I was wandering around a scrapyard and I found this cylinder which was rusted and deformed at the bottom. I cannot think of any other way where you will be able to get it.
Fire extinguisher cylinder: You can contact your local fire department they usually keep damaged fire extinguisher for recycling it into a new one.
Exhaust fan: These can be salvaged from the old CPU power supply box. Just make sure the exhaust has two wires. If it has three wires then you will need an extra electronic speed controller to run it.
Batteries: These can be recycled from old laptop batteries.
Step 3: Dimensions of the Materials
Here I am providing some of the major dimensions, hope these will be helpful.
Cylinder height 600 mm
Cylinder thickness 3mm
Outer diameter of cylinder 295mm
Fire extinguisher height 445mm
Fire extinguisher outer diam 175mm
Fire extinguisher Thickness 2.5mm
If these are the same you can use my dimension provided in further steps.
Step 4: Prerequisites
Some basic practice of welding and metalworking is required to make this project. Such as grinding welding and drilling.
Step 5: Removing the Brass Valve From LPG Cylinder
Usually, the person who owns the scrap disassembles the upper brass valve but if the valve is not removed follow these steps to remove the valve
Press the valve with a stick or screwdriver and let the gas be released out if any, hold the screwdriver for at least a minute or two. Once the gas is released, use a properly sized spanner to open the valve. A pungent smell will be released as soon as the valve is opened. We need to remove this pungent smell. Fill the cylinder with soap water and leave it for 24 hours before emptying it.
Step 6: Disinfecting
Once the inner surface of the cylinder is cleaned properly wash the outer surface of the cylinder since we are going to work with for a longer time and do not want to infect ourselves with the infections from the scrapyard.
Step 7: Disassembling the Fire Extinguisher
Repeat the same steps as we did for the LPG cylinder. I got the fire extinguisher with the valve removed hence cannot provide images of disassembling.
Step 8: 3d Model
Here is the proposed 3d model of the stove you can view it from different angles to get a proper understanding.
Step 9: Cutting the Cylinder
Mark a line along the circumference of the cylinder just below the end of the upper curve. I used masking tape for proper display of the marked ink since the outer surface was not smooth and rusted and a piece of rope for proper line marking.
Cut the cylinder with a grinder or any other tool you wish if it does the job.
Step 10: Cutting the Fire Extinguisher Cylinder
Repeat the same step as we did for the Lpg cylinder for cutting but for marking the height follow these steps.
Measure the depth of the LPG cylinder from the top cut edge to the bottom curved surface.
Now we need to provide some clearance for air delivery and ash collection. I left 15 cm of clearance. So that leaves out 60 cm from the top of the cut cylinder. Calculate this according to your height of the cylinder and mark it on the fire extinguisher and cut open the extinguisher.
Step 11: Drilling Holes
We need a proper air inlet for the fire pit from the bottom of the fire extinguisher. Drill hole on the bottom of the using a 25 mm hole saw. Make sure the holes are evenly spaced. For proper spacing, I drew lines on a circle dividing it into equal parts, and stick it onto the bottom of the extinguisher. Make sure you punch the extinguisher before drilling or else the drill may slip since the surface is curved.
After drilling check for burrs or irregularities and remove it using a file.
Proper spacing of holes will help for the proper and equal flow of air into the fire pit.
Step 12: Drilling Holes 2
Mark a point on the cylinder at a distance of 100mm from the top cut edge of the extinguisher and draw a line along the circumference of the cylinder. The line should be parallel to the cut edge. Drill holes with a 10mm drill bit on this line. The drilled holes have to be equally spaced for the stove to work properly.
For proper spacing, I measured the. Circumference of the extinguisher and divided it into equal parts taking into account space between two drilled holes. Give proper spacing between two holes, we do not want our fire pit to be weak and should withstand the changing temperature and weight of wood.
Step 13: Preparing Steel Ring
The steel ring is made of steel strip. To make it into a circular shape initially try to hammer it to form an arc so that it will be helpful for future steps.
These steps can be eliminated if you have a bender.
Step 14: Temporary Welding
Once you have provided an approximate curve to the steel strip now wrap the strip around the cylinder. Make use of clamps to hold the strip along the circumference of the outer surface of the cylinder. Start bending the strip and place another clamp to hold it into the place.
Weld a small spot as shown in the picture this will help the strip to stay in the same shape when the initial clamp is removed. If the strip does not bend with the hand make use of a hammer. Progress in the same manner as before by placing the removed clamp further ahead until the strip has formed a ring around the cylinder. cut the strip and weld it to the start point of the strip.
Note: these welds are temporary, make small weld spots, larger weld spots will be difficult to cut.
Step 15: Cutting the Ring Out
Once the ring is properly formed cut the welds and remove the ring from the cylinder. Grind irregularities formed by weldments on both the ring and the cylinder. Once the ring is out check if the ring is properly formed.
Step 16: Grinding the Ring and Cylinder to Fit
Grind the rings to remove burrs and irregularities formed by the temporary welding and check whether the ring fits properly into the LPG cylinder. Make sure the ring is seating properly and is not tight fit since when the stove is going to work the metal will expand.
Step 17: Upper Circular Covering
Measure the diameter of both the cylinder and extinguisher. Draw the circles concentric to each other on the steel plate. I did not have a proper tool to draw a large circle so I flipped the cylinder onto the steel plate with the cut edge of the cylinder touching the plate and marked the circle. For the inner circle, I measured the circumference of the extinguisher and drew it on a paper, and glued it to the steel plate. Now for the circles to be concentric, I found out the center of the bigger circle using basic geometry and glued the smaller circle which already had a center point over one another.
Both the inner circle and outer circle was cut with the help of angle grinder I know there must be another proper method to cut the circles but I find this to be the best solution since I do not have proper tools to cut circles on metal. This made my circles a bit irregular hence I had to grind it to the proper shape.
Step 18: Welding Fire Extinguisher to the Plate
Now weld the fire extinguisher to the cut circular steel plate with extinguisher cut edge coinciding with a small circle on the steel plate.
Use a try square to check for perpendicularity of the extinguisher make sure there is no small tilt this will distort the equal airflow in the stove. Now definitely the extinguisher from scrap yard will not be in good shape but try your best to align it properly.
The extinguisher I have had rust on the open edge hence it started to melt when I tried to weld it to the plate. Make sure the weld has perfectly sealed the extinguisher on to the plate and no air can pass through it.
Step 19: Welding Ring to Circular Steel Plate
Place the ring back onto the cylinder and then place the circular steel plate with extinguisher on the cylinder. Properly align the circle on the ring and weld the ring to the steel plate. Make sure it is airtight.
Now the stove is almost ready.
Step 20: Exhaust Inlet
Measure the dimensions of the exhaust fan that is the length breadth and thickness
Weld a simple square box with a metal sheet according to the dimensions of with 1 mm clearance so that the exhaust can slide easily. I created a cardboard box template first so that to understand the fits and requirement of the steel plate box dimension. The sheet with which I have made the box is the same cutouts from the sheet used for making the circular lid.
Now just before you attempt to make this box make sure to check the next two steps.
Step 21: Necessary Banking
The exhaust fan which slides into the metal box as discussed in the previous step needs to have a small tilt or bank of 1° to 5° inwards, why? Well, this provides proper primary air supply to the fire pit.
To provide tilt and to stop the exhaust entering the box we need to weld a plate with a hole equal to the exhaust fan outer diameter at an angle inside the box.
So for the box weld the three sides first viz upper lower and right side of the box and then weld the inner stopper plate.
Once the weld is complete close the box by welding the remaining side plate.
Step 22: Position of the Box
The box is placed at the bottom of the cylinder for proper airflow into the fire pit. It is common logic that the box should not be placed at the most bottom position since the ash of the burnt wood will be falling down in the bottom curve.
Once you have understood the steps cut a hole in the cylinder where the box will come into place and weld it to the cylinder. As usual the weld needs to be airtight.
For proper understanding please refer to the images provided.
Step 23: Battery Pack
I will not go into detail about the battery pack since there are many tutorials available on the internet but to say it in a few lines. The battery pack can be made with four laptop battery cells in series. Each of these batteries has 3.7 v and 3600 mAh ratings hence are enough for our purpose. To be honest I am using a recycled laptop charger with a 12 v rating.
Step 24: Finalizing
Check for irregularities and fits properly and remove rust if any.
Step 25: Firing Up
Start by burning a small piece of paper or a bunch of small twigs and place it into the firepit. Place the wood into the firepit and wait for 10 seconds to let the fire catch-up, now place the exhaust fan properly with the blower side into the cylinder, and voila you are ready to cook.
Step 26: How to Know If It Works
If everything is in the proper place and if the stove is turned on you will be able to see bright orange flame bursting out through the fire pit and a slight light blue flame will be visible where the upper holes are drilled in the fire pit. If the intensity of the main orange is not proper or if you are not able to see the blue flame the stove needs some troubleshooting.
Step 27: Removing Ash
Steel expands when heated hence the circular lid will be tightly secured when you run the stove. Let the stove cool down and hammer the lower edge of the lid to release and then remove the lid and set aside. You will notice the bottom of the LPG cylinder filled with ash empty the ash and you are good to go another burning.
Step 28: Troubleshooting
Now the real part of this type of stove is to burn the smoke or wood gas. Some times it might happen that the smoke(wood gas) is not burning properly if this is the case then drill a secondary set of holes just below the primary hole on the circumference of the fire extinguisher.
If you notice the main flame is not burning properly that is if the intensity is not high enough then you will have to check the holes drilled on the bottom of the fire extinguisher which is the primary inlet for fire pit. Increase the hole diameter by drilling or by filling.
The distance between the outer surface of the fire extinguisher and the inner surface of the LPG cylinder need to as minimum as possible for proper secondary jets of fire.
If you think the speed of the fan is low then substitute it exhaust fan salvaged from old laptops these have higher speed and provide more air .
Step 29: Comparing
It will not be logical to compare the stove with my traditional c type stove since the wood in these stoves fades too quickly and requires regular check so instead, I am going to compare it with an LPG cylinder stove.
The wood gas stove needs around 20 min for 10-liter water from 28°c to reach 80°c.
The LPG gas stove needs 15 min for 10-liter water from 28°c to reach 80°c.
Step 30: Painting
Although it is not required to paint the stove but the material which I have recycled needed to be painted since they rusting at a faster rate.
I used fire-resistant paint for the stove upper section that is a lid or the firepit and normal paint for the rest section of the stove.
The paint and the welding rod might be the only materials I have used which were not recycled.
I have used the stove 4 to 5 times before painting.
Step 31: Handles (optional)
I kept this as optional because handles are not needed except for transporting the stove in most cases the stove will be transported when it is cold and not operating.
The handles were made with simple triangular cutouts welded to the LPG cylinder and bamboo for gripping.
Step 32: Advantages and Disadvantages
- Easy lighting of wood.
- Complete combustion of wood.
- Less or no smoke
- Limited fuel size.
- Batch wise fuel input hence cooking has to be calculated.
- Heat output is not easy to regulate.
Step 33: Final Thoughts
The stove turned out good and I am using it to heat water and it works amazingly, in future modification I would be trying to integrate the ashtray with a fire pit so that I need not lift and turn the LPG cylinder upside down for emptying the ash.
Most of my materials are recycled except for the welding rods and paint.
Any queries or constructive feedback would be appreciated.
Participated in the
Recycled Speed Challenge