Post by sparks on Feb 24, 2014 20:46:56 GMT -8
Greetings Fellow Rocketeers,
I will begin by admitting that I wrote a long post which was "cremated" by the ether.
I have been studying rocket stoves and rocket heaters for some time now. I built a rocket stove which looks much like the classic "Grover" model utilizing 5" diameter 3/32" steel muffler pipe.
This was constructed using the classic Winiarski proportions using the opening of the combustion chamber as the standard...X.
Equation 1. Length of combustion chamber = 2X = 10"
Equation 2. Height of Heat Riser = X + (1.5X or 2 X) + 5 cm.
The basic structure required the CSA which in this case is:
Equation 3. Pi x (2.5 inches) squared = 19.63"2 to remain constant and the pipe being symmetrical met that requirement.
After a few minor calculation issues to set the legs, I finally achieved a product that looks like this:
Admittedly the welding was poor because I didn't have gas flowing from my wire welder and didn't realize it until some time later...I fixed that...needless to say.
Shortly thereafter, I saw a video by a guy on YouTube (ZeroFossilFuel) who build a "Rocket Heater" to heat his 12 x 24' shop. I really liked his design and started to copy it but I came across some very large, thick steel tubing which captured my attention.
m.youtube.com/watch?v=q2eJec82D3I
In his videos he takes you through the steps of the build. He used fire brick and materials locally obtained. If you view his Rocket Heater Video series, you will see that he even added a Pellet modification although he went through several steps burning wood with VERY satisfying results.
I decided to build a similar Rocket heater but the materials I had were somewhat different. I used 6" square steel tubing which is 3/8" thick. While I know fire brick has a longer life, I figured at the tender age of 64, the 3/8" steel would last as long as I needed it.
Here are some photographs of varying stages of the build.
In this photo, the pieces were cut with an industrial band saw and they are simply sitting together. After this, they were welded.
That saw cuts such an accurate 45 degree that the parts were very easy to weld.
Next, I built a platform on which it could stand out of concrete blocks and test fired it to see if it too, would burn "as advertised. It did fine. So on to the next step. I got an old water heater tank from the junk pile in town and created the "bell". The heat riser here is 47" tall and the combustion chamber is about 24" long, again attempting to stay within the "Winiarski" model for design. My reasoning for using this large steel tubing was to be able to burn larger pieces of wood thinking a 5" log would burn for quite some time in this stove thinking that due to the very large CSA of the burn chamber it should allow the burning of larger stock. (This turned out to be less than optimal. Hence the reason for this post)
Insulating the heat riser was accomplished with an 8" stove pipe, filled with Vermiculite. In retrospect I probably could have used a larger insulation container but that was a matter of availability. This gave a 4" spacing around the inside of the 16" diameter bell.
As you can see, I added a vertical component to the combustion chamber to make this into a J-Tube rather than the classic "L" shape described by Winiarski. I was careful to maintain the 2" spacing between the top of the heat riser and the top of the "bell". I used a portion of 5" steel muffler pipe (scrap from the other stove) as the exhaust tube.
In this photo, the bottom of the steel water heater tank is sitting next to the platform for the Rocket Heater. Of significance is the technical detail that I was able to cut most of the modifications to the tank with a power jig saw utilizing a hacksaw blade now made for this. The increased precision with which I was afforded made the product a great deal more satisfying.
(Doing it by hand would have been prohibitive and I am NOT all that good cutting with a torch. Perhaps a plasma cutter would have been easier but I don't have one "YET".)
Rather than weld everything together, i.e. the "rocket stove" and the "bell" I opted to cut the tank low enough to allow the rocket stove to sit on the convex bottom of the tank and welded some tabs and bolts to the bottom so it could be dis-assembled for modification. (See photo above with the insulation container)
One major error was NOT cutting out the opening where the heater coil for the water heater had been and managed to cut across the top of it, so that needed to be filled in. Had I avoided that altogether, I might have been able to use it for a "clean out" or accessory air "intake".
Initial Test burn (Seen here)
showed that the concept was indeed functional. I was able to burn somewhat larger stock, but not the size I had originally wanted. Splitting that 5 inch stock yielded a much better burn.
The draw of this particular stove is ordinarily quite good and I rarely have difficulty with back burn or smoke unless there is a change in the wind direction.
On occasion, I do get some smoke backing up and have found a small fan kept close by will overcome the backwards flow of air and get the flames going in the right direction again. This however is rare.
Some difficulty arises initially when the temperatures outside are in the sub-zero range because it takes a while for the heat riser to get hot. Once it does, the smoke soon becomes steam emanating from the exhaust piping and the temperatures on the stove are quite good.
Ordinarily, I get the temperature on the front of the "bell" to about 300*F to 350*F. The top can hit much higher and the combustion chamber can reach over 800*F. I have dropped a piece of paper on the horizontal burn chamber and it burst into flames almost immediately.
Now to the purpose of this post. In all my reading and all of my study (which includes the fabrication of the rocket heater) I have not been able to find any guidance or even suggestion as to the height of the vertical fuel magazine which changes the "L" into the "J".
Can anyone here offer any suggestion as to exactly what the limits are for the "J" tube? My difficulty with this particular Rocket heater is getting my hand in deep enough to clean it out. I could use a Shop Vac but my intent is to do this with out electricity in the event that becomes necessary.
I will begin by admitting that I wrote a long post which was "cremated" by the ether.
I have been studying rocket stoves and rocket heaters for some time now. I built a rocket stove which looks much like the classic "Grover" model utilizing 5" diameter 3/32" steel muffler pipe.
This was constructed using the classic Winiarski proportions using the opening of the combustion chamber as the standard...X.
Equation 1. Length of combustion chamber = 2X = 10"
Equation 2. Height of Heat Riser = X + (1.5X or 2 X) + 5 cm.
The basic structure required the CSA which in this case is:
Equation 3. Pi x (2.5 inches) squared = 19.63"2 to remain constant and the pipe being symmetrical met that requirement.
After a few minor calculation issues to set the legs, I finally achieved a product that looks like this:
Admittedly the welding was poor because I didn't have gas flowing from my wire welder and didn't realize it until some time later...I fixed that...needless to say.
Shortly thereafter, I saw a video by a guy on YouTube (ZeroFossilFuel) who build a "Rocket Heater" to heat his 12 x 24' shop. I really liked his design and started to copy it but I came across some very large, thick steel tubing which captured my attention.
m.youtube.com/watch?v=q2eJec82D3I
In his videos he takes you through the steps of the build. He used fire brick and materials locally obtained. If you view his Rocket Heater Video series, you will see that he even added a Pellet modification although he went through several steps burning wood with VERY satisfying results.
I decided to build a similar Rocket heater but the materials I had were somewhat different. I used 6" square steel tubing which is 3/8" thick. While I know fire brick has a longer life, I figured at the tender age of 64, the 3/8" steel would last as long as I needed it.
Here are some photographs of varying stages of the build.
In this photo, the pieces were cut with an industrial band saw and they are simply sitting together. After this, they were welded.
That saw cuts such an accurate 45 degree that the parts were very easy to weld.
Next, I built a platform on which it could stand out of concrete blocks and test fired it to see if it too, would burn "as advertised. It did fine. So on to the next step. I got an old water heater tank from the junk pile in town and created the "bell". The heat riser here is 47" tall and the combustion chamber is about 24" long, again attempting to stay within the "Winiarski" model for design. My reasoning for using this large steel tubing was to be able to burn larger pieces of wood thinking a 5" log would burn for quite some time in this stove thinking that due to the very large CSA of the burn chamber it should allow the burning of larger stock. (This turned out to be less than optimal. Hence the reason for this post)
Insulating the heat riser was accomplished with an 8" stove pipe, filled with Vermiculite. In retrospect I probably could have used a larger insulation container but that was a matter of availability. This gave a 4" spacing around the inside of the 16" diameter bell.
As you can see, I added a vertical component to the combustion chamber to make this into a J-Tube rather than the classic "L" shape described by Winiarski. I was careful to maintain the 2" spacing between the top of the heat riser and the top of the "bell". I used a portion of 5" steel muffler pipe (scrap from the other stove) as the exhaust tube.
In this photo, the bottom of the steel water heater tank is sitting next to the platform for the Rocket Heater. Of significance is the technical detail that I was able to cut most of the modifications to the tank with a power jig saw utilizing a hacksaw blade now made for this. The increased precision with which I was afforded made the product a great deal more satisfying.
(Doing it by hand would have been prohibitive and I am NOT all that good cutting with a torch. Perhaps a plasma cutter would have been easier but I don't have one "YET".)
Rather than weld everything together, i.e. the "rocket stove" and the "bell" I opted to cut the tank low enough to allow the rocket stove to sit on the convex bottom of the tank and welded some tabs and bolts to the bottom so it could be dis-assembled for modification. (See photo above with the insulation container)
One major error was NOT cutting out the opening where the heater coil for the water heater had been and managed to cut across the top of it, so that needed to be filled in. Had I avoided that altogether, I might have been able to use it for a "clean out" or accessory air "intake".
Initial Test burn (Seen here)
showed that the concept was indeed functional. I was able to burn somewhat larger stock, but not the size I had originally wanted. Splitting that 5 inch stock yielded a much better burn.
The draw of this particular stove is ordinarily quite good and I rarely have difficulty with back burn or smoke unless there is a change in the wind direction.
On occasion, I do get some smoke backing up and have found a small fan kept close by will overcome the backwards flow of air and get the flames going in the right direction again. This however is rare.
Some difficulty arises initially when the temperatures outside are in the sub-zero range because it takes a while for the heat riser to get hot. Once it does, the smoke soon becomes steam emanating from the exhaust piping and the temperatures on the stove are quite good.
Ordinarily, I get the temperature on the front of the "bell" to about 300*F to 350*F. The top can hit much higher and the combustion chamber can reach over 800*F. I have dropped a piece of paper on the horizontal burn chamber and it burst into flames almost immediately.
Now to the purpose of this post. In all my reading and all of my study (which includes the fabrication of the rocket heater) I have not been able to find any guidance or even suggestion as to the height of the vertical fuel magazine which changes the "L" into the "J".
Can anyone here offer any suggestion as to exactly what the limits are for the "J" tube? My difficulty with this particular Rocket heater is getting my hand in deep enough to clean it out. I could use a Shop Vac but my intent is to do this with out electricity in the event that becomes necessary.