Happy Easter to you also! You make it all look easy and did a great job. I like seeing the learning along the way. You’ve added a great bit of encouragement to all of us hoping to complete our own projects. I’m sorry you couldn’t continue to use your RMH in your house. I have a similar issue and have come up with a solution that may work for you also. Basically it’s making an outside wood boiler. I’d like to have someone check out my plans to give input. Please let me know if your interested.
Great job! Ingenious idea for the door slider that i havent seen anyone else explain how to make. I like it! Also learned just going by that crack in the heat risor that thares actually quite a bit of heat expansion. Good to know and really consider on my build this summer. Thanks! Keep it up!
Thanks chevy, glad you liked it. Yes, the crack in the heat riser became wider as the burn went on, suggesting there is expansion with heat. I couldn't film it as I needed both hands but I tried closing the gap with my hands to see how much force the expansion was exerting and it was negligible - the gap could be closed with barely a touch. I'm pretty sure that had the piece been mortared together, any cracks would have stayed closed. I really need to find somewhere that I can install the burner with mortar and make the chamber air tight. I won't know the effects of controlling the air until I can do that. Thanks again, Dave.
Hi, You have made wonderful and very informative videos, thank you very much. How is the rocket heater peforming indoors ? How big is the room and how high can you heat up the room ? Greetings from Holland.
Thank you for your kind comment Peter. I live in a small house, maybe 700sq feet, built in the mid 1800s, of brick. I installed the heater in coldest room on the ground floor. The room is under 4 x 3 metres and at that time, when I was renovating the house, very draughty. I built a lime-plasterd brick bench and bell sides, with a standard oil drum over the top of the riser. I have a solid concrete floor and don't think a suspended wooden floor would take the weight of what I built. The room had a brick chimney into which I vented the cooled gases from the bottom of the bell bench. The draw was good. It was very big, maybe 1.5 - 2 sq metres footprint , and the top of the drum was only about 0.5 metres below my 2.7 m ceiling, so not ideal in a small room. For this reason alone, I only kept it for one winter. It exceeded my expectations by a long margin. The quality of the warmth was amazing and it was far easier to use and maintain than I ever imagined possible. I burnt mostly waste construction lumber and probably lit it 3 times a day, letting it burn out completely in between. An hour after lighting, the room it was in would reach air temperatures in the mid to high 30s (Celsius) with the wall surfaces averaging about 25˚C (I'm not exageratting, I bought a laser thermometer and was fascinated by it). The ceiling immediately above the drum could reach 70˚C during a strong burn. The stone bench seat would reach around 50˚C (surprisingly comfortable to sit on with a thin cushion). The drum sides would heat to around 200˚C near the top, and around 100˚C near the base. The drum heats up very quickly, you feel radiant heat off the drum within minutes of lighting it. The room upstairs above, would be around 25˚C and the entire house was never below maybe 18˚C even in mid winter. In the morning (I always let it burn out before bed) I was greeted with low 20s ambient temperature in the room where it was housed, and the masonry was still warm to touch. For that whole winter, the only time I used the central heating boiler was if I had house guests staying in the attic room (the other radiator thermostats were turned off). Finding wood was easy as I live in a city with a constant supply of construction lumber from building skips. The only problem I had for that entire winter was the couple of times it became very windy outside, I might get a puff of smoke push out of the secondary air duct. This happened maybe three times in total. The smoke wasn't excessive but did need venting by opening the window (no problem as the room was so warm, drafts became benign). I imagine a modern flue pipe with a rotating cowl would not have this problem. A crack appeared in the masonry immediately above the core which required attention with fresh plaster a couple of times. When I dismantled the heater I discovered poor brcik joints there so I would take more care in the hot areas next time. I miss it but it was simply too large for my house. If I ever move to a larger one, it will be the first thing I install, especially with the way energy prices are going. I'm constantly thinking about developing my original plan, which was to build the heater outside and use it to heat water to supplement my central heating, but never seem to have the time to get on with it. Again, thanks for your comment, and good luck if you embark on a similar project. Dave.
@@batchrocketproject4720 Hi Dave, Thank you for the extensive respons.... Yes the energy prices is what made me go for it. I have been looking at rocket heater build for over 2 years. I like to build a square one out of steel and with a kind of removeble oven to bake bread. Thanks again and have a good one. Peter.
Hey there dood! How are you doing? Thought I would write to you and let you know that I have just uploaded a series of videos of my batch rocket heater project that was inspired largely by you. Thanks so much for your films they were a great help (clay balls aside!!) big thumbs up to you and Peter. All the best. Tanc
Thanks for persisting with the video series Gary. At this stage, because of the cracks, there is still an excess of primary air but it's another step along the way.
Soudal do a high temperature fire cement / glue in a 330ml cartridge . excellent for sealing cracks and air leaks . a wet sponge to dampen the surface and it works wonders . not expensive .€8 Euros a 330ml tube/ cartridge. it washes off hands and tools with water before it sets . it also makes a good bedding sealer / glue for ceramic rope.
Thanks for the tip. I used a home made stone glue from sodium silicate, magnesium silicate, and a little fireclay. I repaired the cracks with that and they were fine when I finally installed the burner. After a winter of use, the remained sound. I'll have a look for the Soudal product if I ever get around to another install in future.
I realize that now it’s been 2 years since you had the big crack in your stove. I think waterglass would probably seal up that crack. It worked pretty well on mine. 👍
Yes, I made a paste of waterglass and talc and it glued the cracks closed nicely (although I still haven't found the time to make a follow-up video, the repaired pieces lasted a whole winter of daily burns and were fine). Thanks for the comment.
Any luck with the water heater? I made a simple copper coil one in the upper part of the flue (beyond the heat riser) for a basic J type rocket stove. It works well but the fire needs constant re stocking. Hence looking to build a batch rocket equivalent. Have you had any thoughts about how you'd go about it? Great videos! Keep up the good work!
Unfortunately 'life events' got in the way of progress and I never built a working water heater. I did instead install the burner indoors as a mass heater and it was fantastic. I'm still really keen to one day progress the water heating as I think it could be installed outside of a house and make hot water that can be used inside the house as heating. I've had lots of ideas but won't be able to judge their merit until I experiment! The only thing I would say is that a batch heater even larger than this (maybe 9" system, rather than the 6" I built) would be better as the burns would last longer. Did you experiment with placing your copper coil in different places? I was planning on having it inside the bell but below the top of the heat riser, to catch gases as they were forced downwards by the bell. If I understood your comment right, you had it above to catch direct heat - were there any problems with that? Keep experimenting Pete!
I notice a lot of smoke coming from around the stove and can see the color red made by flames of the fire. Would using some sore of sealant give more reliable results to increase the overall efficiency of the stove ??? Maybe use a temperature reader to see just how hot the combustion was??? Maybe make an burn chamber design to even raise the heat to the limit for ultimate efficiency ??? Please respond with your thoughts. Nice job fella.
Much of what looks like smoke coming from the outside of the burn chamber is actually steam caused by the casting getting rained on. You're definitely right that the efficiency depends on the gaps being sealed. I eventually installed the burner and closed all the gaps with mortar and there were no further problems or cracks. Thanks for the comment.
wonder if you moved the slot in the back of the batch box over to the left side of the insulated riser, could you then create a clockwise swirl around the riser wall? north equator.
Mine didn't have that but yes, I've seen videos that guide the burn into a nice vortex. We definitely need to experiment to see if the direction of the swirl changes either side of the equator!
First video I watched on your channel. Sorry I don’t have a link but search UA-cam for honey do carpenter. He is using silica gel (water silica?) for protecting the burn chamber heat riser etc. Got to get going here. Peace.
Thanks for the tip. I've watched honey-do's videos and they're great. My early experiments used sodium silicate (purchased as no one has yet convinced me that 'home made' is actually sodium silicate) and found refractory cement products were superior. I believe the commercially-available forge bricks are made by binding perlite or vermiculte with sodium silicate so there's clearly possibility. Whatever works, works!
Thanks for the tip. I wondered if reinforcement might help, not sure whether metal mesh might introduce stresses due to the heat. Kevlar sounds like a good option.
Yes, I installed it indoors as a mass heater for a winter (it was fantastic). I hope to do a follow-up video but I used a brick box with a 200L drum over the riser. The final venting was at floor level through a conventional brick chimney already in the house.
Might consider mixing some Rock Wool fibers into the refractory next time to reinforce the cement. I just cast a riser from 2700°F cement and Perlite in a 3:4 mix. Hopefully it resists cracking.
That's an excellent idea Kentucky, thanks for sharing it. A viewer on an earlier video, @changeindirection, suggested chopped basalt fibres but they seem difficult to get here in the UK and are quite expensive. Did you chop your own fibres from a regular rock-wool insulation batt? How much fibre do you add to a given quantity of concrete? Was it easy to incorporate the fibres into the mix? Sorry for the questions; I'd really like to try something similar and I'd be really interested to hear how your casting fares. Thanks. Dave
@@batchrocketproject4720 I have access to rock wool batt here at work. I just tossed a couple handfuls into the bucket I used to mix everything and it broke down on its own during mixing. I messed up the drying process, unfortunately, by moving the riser before it was fully cured, causing the bottom to crumble. I used large cardboard tubes as molds and they held the moisture in much longer than I expected, so it was still soft when I moved it. Once I removed the tubes, the riser cured and hardened remarkably well in about a day, save for the bottom section. I'll make another one eventually since I know how to do it correctly now. I actually dropped the whole thing on its side just to test it since it was already broken, and it held together.
I thought about trying some mesh reinforcement but was worried steel might expand at a different rate to the surrounding mortar and introduce additional stresses under heat (I've read that Coventry cathedral collapsed during the German fire-bomb attacks because the stone pillars had steel inserts that expanded under heat and stressed them). I eventually installed the burner and, once everything was mortared in place, no cracks occurred. Thanks for the comment.
Just found your channel and watched the lot, very interesting stuff. I'm sure if your set up was inside and kept dry it would be just fine. I really like how you've tried to do it all yourself from basic materials. Has the project stalled, or has there been any progress?
Thanks Roger. I eventually installed it as a mass heater for the winter of 2019-2020 and hope to report on that soon. I repaired the cracks rather than re-casting pieces and they worked fine when installed.
I think the main reason for the weakness it had during the experiments was that the casting absorbed moisture. When I finally installed the burner, there was never any problems with cracks and, although soft, the castings didn't spall or flake. I'm not sure heat made them stronger but it didn't seem to weaken them.
You may find it useful to use some high temperature caulking to seal the largest cracks in the batchbox, so that you can test the control you've developed with the sliding grill. This may also reduce cracking by forming a cushioned interface between the pieces, rather than allowing the pieces to impact with each other.
Thanks for the comment Lictre. Yes, some flexing at the stress points should help keep it intact. The cracks, and gap around the door frame probably exceed the area of the primary air grille and so I will definitely need to seal everything to be able to control the air. The perimeter of the door frame is around 1.4 metres, so, even with a 2.5 mm average gap around it, the gap area would be equivalent to the whole primary air grille, which is around 3,500 square mm. Dave
Looks great!, a Nice clean burn!. I would reinforce your casted batch box with galvanized chicken fence. Then the box is allowed to crack becouse evrything will be held together by it.
Thanks for the comment Johan. I may well try reinforcements in any future castings. I finally installed it as a mass heater, bonding the cracks with fireclay and a home-made cement. After three months burning, none of the cracks have reappeared - they were more a result of the fragility of the unsupported and often damp castings than of any strong exansion forces of the heat.
When I installed the heater, I mortared everything together with a simple lime mortar. I expected it to fail under heat but was pleased to discover all the joints were still sound after a winter of use. Thanks for the comment.
You're definitely right on that Richard! Especially if the concrete has perlite or vermiculite as both absorb some moisture even after setting in concrete.
I know, I need to do a follow-up. I installed and used the burner as a mass heater for the winter of 2019-2020 and hope to share some stuff on that soon.
Those are not cracks. Those are automatic, temperature controlled secondary air inlets. Anyway, after learning from your experiment I'd make the riser of two of half cylinders to avoid crackings.
ha ha, yes, there was no shortage of air for secondary burn with those cracks. Two half cylinders may well be a better way to do the casting. I repaired the cracks and installed the burner - once everything was mortared in place, there were no more cracks so the forced generated by the heat are not that much of a problem. Thanks for the comment.
The rectangle is the open end of a steel tube that takes air to the base of the heat riser in order to feed a secondary burn (where much of the smoke ignites).
Yes, the air control made no difference while the gaps were there! When I installed the burner, all the gaps were sealed and the air control worked well. I could close the air down once the burner was very hot and it would gas away calmly - the flames almost looked like they were in slow motion. I hope to eventually do a follow-up video when I get chance. Thanks for the comment.
Peter - yes, a firebrick riser, and burn chamber would work well, there are sketchup designs on Peter van den Berg's webiste: batchrocket.eu/en/designs#brick1 I considered using firebrick but wanted the insulated type which would have proved prohibitively expensive. For me it was easier and more economical to make the casting.
Marco - I'm still trying to find somewhere to make a more permanent installation so I can experiment with various bell options. It's been a little frustrating and I'm having to repair some brickwork before I can make an installation. I'm itching to get on with it and have many plans. As a side project I've been working on a datalogger with thermocouples and temperature probes so I can monitor temperatures in the hot gases and, ultimately, heat transfer to water. I was not sure the electronics would be of interest here and had hoped to have been back on the actual burner stuff by now. Hopefully soon! Thanks for your interest, really appreciated. Dave.
BatchRocketProject I feel your pain there my friend! And while the burner stuff got me here, I do enjoy a good Arduino or Raspberry Pi data logging vid.. just sayin!
Thanks Marco. I'll have a think putting a video together about my (arduino-based) datalogger, it's been interesting developing it and maybe some fire enthusiasts would like to record temperatures.
I loved watching fire coming that far above the heat riser, that’s a powerful heating machine you have made.
What a nice batchbox you have created. The amount of thought and planning shows. Looking forward to updates on your project.
Thanks Brian. I hope to post an update soon
Happy Easter to you also! You make it all look easy and did a great job. I like seeing the learning along the way. You’ve added a great bit of encouragement to all of us hoping to complete our own projects.
I’m sorry you couldn’t continue to use your RMH in your house. I have a similar issue and have come up with a solution that may work for you also.
Basically it’s making an outside wood boiler. I’d like to have someone check out my plans to give input. Please let me know if your interested.
Great job! Ingenious idea for the door slider that i havent seen anyone else explain how to make. I like it! Also learned just going by that crack in the heat risor that thares actually quite a bit of heat expansion. Good to know and really consider on my build this summer. Thanks! Keep it up!
Thanks chevy, glad you liked it.
Yes, the crack in the heat riser became wider as the burn went on, suggesting there is expansion with heat. I couldn't film it as I needed both hands but I tried closing the gap with my hands to see how much force the expansion was exerting and it was negligible - the gap could be closed with barely a touch. I'm pretty sure that had the piece been mortared together, any cracks would have stayed closed.
I really need to find somewhere that I can install the burner with mortar and make the chamber air tight. I won't know the effects of controlling the air until I can do that.
Thanks again, Dave.
Hi, You have made wonderful and very informative videos, thank you very much.
How is the rocket heater peforming indoors ? How big is the room and how high can you heat up the room ?
Greetings from Holland.
Thank you for your kind comment Peter. I live in a small house, maybe 700sq feet, built in the mid 1800s, of brick. I installed the heater in coldest room on the ground floor. The room is under 4 x 3 metres and at that time, when I was renovating the house, very draughty. I built a lime-plasterd brick bench and bell sides, with a standard oil drum over the top of the riser. I have a solid concrete floor and don't think a suspended wooden floor would take the weight of what I built. The room had a brick chimney into which I vented the cooled gases from the bottom of the bell bench. The draw was good.
It was very big, maybe 1.5 - 2 sq metres footprint , and the top of the drum was only about 0.5 metres below my 2.7 m ceiling, so not ideal in a small room. For this reason alone, I only kept it for one winter.
It exceeded my expectations by a long margin. The quality of the warmth was amazing and it was far easier to use and maintain than I ever imagined possible. I burnt mostly waste construction lumber and probably lit it 3 times a day, letting it burn out completely in between.
An hour after lighting, the room it was in would reach air temperatures in the mid to high 30s (Celsius) with the wall surfaces averaging about 25˚C (I'm not exageratting, I bought a laser thermometer and was fascinated by it). The ceiling immediately above the drum could reach 70˚C during a strong burn. The stone bench seat would reach around 50˚C (surprisingly comfortable to sit on with a thin cushion). The drum sides would heat to around 200˚C near the top, and around 100˚C near the base. The drum heats up very quickly, you feel radiant heat off the drum within minutes of lighting it. The room upstairs above, would be around 25˚C and the entire house was never below maybe 18˚C even in mid winter. In the morning (I always let it burn out before bed) I was greeted with low 20s ambient temperature in the room where it was housed, and the masonry was still warm to touch.
For that whole winter, the only time I used the central heating boiler was if I had house guests staying in the attic room (the other radiator thermostats were turned off). Finding wood was easy as I live in a city with a constant supply of construction lumber from building skips.
The only problem I had for that entire winter was the couple of times it became very windy outside, I might get a puff of smoke push out of the secondary air duct. This happened maybe three times in total. The smoke wasn't excessive but did need venting by opening the window (no problem as the room was so warm, drafts became benign). I imagine a modern flue pipe with a rotating cowl would not have this problem. A crack appeared in the masonry immediately above the core which required attention with fresh plaster a couple of times. When I dismantled the heater I discovered poor brcik joints there so I would take more care in the hot areas next time.
I miss it but it was simply too large for my house. If I ever move to a larger one, it will be the first thing I install, especially with the way energy prices are going. I'm constantly thinking about developing my original plan, which was to build the heater outside and use it to heat water to supplement my central heating, but never seem to have the time to get on with it.
Again, thanks for your comment, and good luck if you embark on a similar project. Dave.
@@batchrocketproject4720 Hi Dave,
Thank you for the extensive respons....
Yes the energy prices is what made me go for it. I have been looking at rocket heater build for over 2 years.
I like to build a square one out of steel and with a kind of removeble oven to bake bread.
Thanks again and have a good one.
Peter.
Hey there dood! How are you doing? Thought I would write to you and let you know that I have just uploaded a series of videos of my batch rocket heater project that was inspired largely by you. Thanks so much for your films they were a great help (clay balls aside!!) big thumbs up to you and Peter. All the best. Tanc
Excellent, I look forward to going through them later today. Well done!
I’m now beginning to see where this could go , so keep at it maybe there will be a point.
Well done !
Thanks for persisting with the video series Gary. At this stage, because of the cracks, there is still an excess of primary air but it's another step along the way.
Really enjoyed this video.
Thank you.
Soudal do a high temperature fire cement / glue in a 330ml cartridge . excellent for sealing cracks and air leaks . a wet sponge to dampen the surface and it works wonders . not expensive .€8 Euros a 330ml tube/ cartridge. it washes off hands and tools with water before it sets . it also makes a good bedding sealer / glue for ceramic rope.
Thanks for the tip. I used a home made stone glue from sodium silicate, magnesium silicate, and a little fireclay. I repaired the cracks with that and they were fine when I finally installed the burner. After a winter of use, the remained sound. I'll have a look for the Soudal product if I ever get around to another install in future.
I realize that now it’s been 2 years since you had the big crack in your stove. I think waterglass would probably seal up that crack. It worked pretty well on mine. 👍
Yes, I made a paste of waterglass and talc and it glued the cracks closed nicely (although I still haven't found the time to make a follow-up video, the repaired pieces lasted a whole winter of daily burns and were fine). Thanks for the comment.
very nice work my friend 👍👍
One more thought.
A bit of steel to hold the refractory together might help minimize the cracks.
Any luck with the water heater? I made a simple copper coil one in the upper part of the flue (beyond the heat riser) for a basic J type rocket stove. It works well but the fire needs constant re stocking. Hence looking to build a batch rocket equivalent. Have you had any thoughts about how you'd go about it? Great videos! Keep up the good work!
Unfortunately 'life events' got in the way of progress and I never built a working water heater. I did instead install the burner indoors as a mass heater and it was fantastic. I'm still really keen to one day progress the water heating as I think it could be installed outside of a house and make hot water that can be used inside the house as heating. I've had lots of ideas but won't be able to judge their merit until I experiment! The only thing I would say is that a batch heater even larger than this (maybe 9" system, rather than the 6" I built) would be better as the burns would last longer.
Did you experiment with placing your copper coil in different places? I was planning on having it inside the bell but below the top of the heat riser, to catch gases as they were forced downwards by the bell. If I understood your comment right, you had it above to catch direct heat - were there any problems with that?
Keep experimenting Pete!
I notice a lot of smoke coming from around the stove and can see the color red made by flames of the fire. Would using some sore of sealant give more reliable results to increase the overall efficiency of the stove ??? Maybe use a temperature reader to see just how hot the combustion was??? Maybe make an burn chamber design to even raise the heat to the limit for ultimate efficiency ??? Please respond with your thoughts. Nice job fella.
Much of what looks like smoke coming from the outside of the burn chamber is actually steam caused by the casting getting rained on. You're definitely right that the efficiency depends on the gaps being sealed. I eventually installed the burner and closed all the gaps with mortar and there were no further problems or cracks.
Thanks for the comment.
wonder if you moved the slot in the back of the batch box over to the left side of the insulated riser, could you then create a clockwise swirl around the riser wall? north equator.
Mine didn't have that but yes, I've seen videos that guide the burn into a nice vortex. We definitely need to experiment to see if the direction of the swirl changes either side of the equator!
The coriolis force is BS.
Is been proven nonsense many times
First video I watched on your channel. Sorry I don’t have a link but search UA-cam for honey do carpenter. He is using silica gel (water silica?) for protecting the burn chamber heat riser etc. Got to get going here. Peace.
Thanks for the tip. I've watched honey-do's videos and they're great. My early experiments used sodium silicate (purchased as no one has yet convinced me that 'home made' is actually sodium silicate) and found refractory cement products were superior. I believe the commercially-available forge bricks are made by binding perlite or vermiculte with sodium silicate so there's clearly possibility. Whatever works, works!
Have you considered using Helix, a new type of micro reinforcing bar, there are metal ones and Kevlar types, in the mix
Thanks for the tip. I wondered if reinforcement might help, not sure whether metal mesh might introduce stresses due to the heat. Kevlar sounds like a good option.
Did you ever put a barrel (as a bell) over everything and install a low exit for the exhaust gases?
Yes, I installed it indoors as a mass heater for a winter (it was fantastic). I hope to do a follow-up video but I used a brick box with a 200L drum over the riser. The final venting was at floor level through a conventional brick chimney already in the house.
Might consider mixing some Rock Wool fibers into the refractory next time to reinforce the cement. I just cast a riser from 2700°F cement and Perlite in a 3:4 mix. Hopefully it resists cracking.
That's an excellent idea Kentucky, thanks for sharing it. A viewer on an earlier video, @changeindirection, suggested chopped basalt fibres but they seem difficult to get here in the UK and are quite expensive. Did you chop your own fibres from a regular rock-wool insulation batt? How much fibre do you add to a given quantity of concrete? Was it easy to incorporate the fibres into the mix? Sorry for the questions; I'd really like to try something similar and I'd be really interested to hear how your casting fares. Thanks. Dave
@@batchrocketproject4720 I have access to rock wool batt here at work. I just tossed a couple handfuls into the bucket I used to mix everything and it broke down on its own during mixing. I messed up the drying process, unfortunately, by moving the riser before it was fully cured, causing the bottom to crumble. I used large cardboard tubes as molds and they held the moisture in much longer than I expected, so it was still soft when I moved it. Once I removed the tubes, the riser cured and hardened remarkably well in about a day, save for the bottom section. I'll make another one eventually since I know how to do it correctly now. I actually dropped the whole thing on its side just to test it since it was already broken, and it held together.
Would using light gauge square screening help prevent the refectory from splitting ???
I thought about trying some mesh reinforcement but was worried steel might expand at a different rate to the surrounding mortar and introduce additional stresses under heat (I've read that Coventry cathedral collapsed during the German fire-bomb attacks because the stone pillars had steel inserts that expanded under heat and stressed them).
I eventually installed the burner and, once everything was mortared in place, no cracks occurred.
Thanks for the comment.
Just found your channel and watched the lot, very interesting stuff. I'm sure if your set up was inside and kept dry it would be just fine. I really like how you've tried to do it all yourself from basic materials. Has the project stalled, or has there been any progress?
Thanks Roger. I eventually installed it as a mass heater for the winter of 2019-2020 and hope to report on that soon. I repaired the cracks rather than re-casting pieces and they worked fine when installed.
Does the refractory get more brittle the more times it is burned ??? Thanks
I think the main reason for the weakness it had during the experiments was that the casting absorbed moisture. When I finally installed the burner, there was never any problems with cracks and, although soft, the castings didn't spall or flake. I'm not sure heat made them stronger but it didn't seem to weaken them.
You may find it useful to use some high temperature caulking to seal the largest cracks in the batchbox, so that you can test the control you've developed with the sliding grill. This may also reduce cracking by forming a cushioned interface between the pieces, rather than allowing the pieces to impact with each other.
Thanks for the comment Lictre. Yes, some flexing at the stress points should help keep it intact. The cracks, and gap around the door frame probably exceed the area of the primary air grille and so I will definitely need to seal everything to be able to control the air. The perimeter of the door frame is around 1.4 metres, so, even with a 2.5 mm average gap around it, the gap area would be equivalent to the whole primary air grille, which is around 3,500 square mm. Dave
Looks great!, a Nice clean burn!. I would reinforce your casted batch box with galvanized chicken fence. Then the box is allowed to crack becouse evrything will be held together by it.
Thanks for the comment Johan. I may well try reinforcements in any future castings.
I finally installed it as a mass heater, bonding the cracks with fireclay and a home-made cement. After three months burning, none of the cracks have reappeared - they were more a result of the fragility of the unsupported and often damp castings than of any strong exansion forces of the heat.
I see a small gap between the two halfs of the burn chamber. Didn't you use aluminium vilt between the two halves?
When I installed the heater, I mortared everything together with a simple lime mortar. I expected it to fail under heat but was pleased to discover all the joints were still sound after a winter of use.
Thanks for the comment.
leaving the rocket stove out in the rain then burning it like crazy will crack it every time .
You're definitely right on that Richard! Especially if the concrete has perlite or vermiculite as both absorb some moisture even after setting in concrete.
Y porque no usas metal en lugar de hormigón?
Yes, many designs use metal. I preferred to experiment with concrete as, for me, it was easier and cheaper. Thanks for the comment!
Looks great. Where’s the next video?
I know, I need to do a follow-up. I installed and used the burner as a mass heater for the winter of 2019-2020 and hope to share some stuff on that soon.
Those are not cracks. Those are automatic, temperature controlled secondary air inlets.
Anyway, after learning from your experiment I'd make the riser of two of half cylinders to avoid crackings.
ha ha, yes, there was no shortage of air for secondary burn with those cracks. Two half cylinders may well be a better way to do the casting. I repaired the cracks and installed the burner - once everything was mortared in place, there were no more cracks so the forced generated by the heat are not that much of a problem.
Thanks for the comment.
Whats the little open rectangle at the bottom?
The rectangle is the open end of a steel tube that takes air to the base of the heat riser in order to feed a secondary burn (where much of the smoke ignites).
Possibly all the gaps are a free secondary burn
Yes, the air control made no difference while the gaps were there! When I installed the burner, all the gaps were sealed and the air control worked well. I could close the air down once the burner was very hot and it would gas away calmly - the flames almost looked like they were in slow motion. I hope to eventually do a follow-up video when I get chance.
Thanks for the comment.
How about making the heat riser out of fire brick?
Peter - yes, a firebrick riser, and burn chamber would work well, there are sketchup designs on Peter van den Berg's webiste: batchrocket.eu/en/designs#brick1
I considered using firebrick but wanted the insulated type which would have proved prohibitively expensive. For me it was easier and more economical to make the casting.
Beautiful!
Thanks Attilio!
Any progress on the water heating?
Unfortunately not. Instead I've made a temporary install as a mass heater. I hope to post a video soon. Thanks for your interest.
Any updates or improvements ?
Marco - I'm still trying to find somewhere to make a more permanent installation so I can experiment with various bell options. It's been a little frustrating and I'm having to repair some brickwork before I can make an installation. I'm itching to get on with it and have many plans. As a side project I've been working on a datalogger with thermocouples and temperature probes so I can monitor temperatures in the hot gases and, ultimately, heat transfer to water. I was not sure the electronics would be of interest here and had hoped to have been back on the actual burner stuff by now. Hopefully soon! Thanks for your interest, really appreciated. Dave.
BatchRocketProject I feel your pain there my friend! And while the burner stuff got me here, I do enjoy a good Arduino or Raspberry Pi data logging vid.. just sayin!
Thanks Marco. I'll have a think putting a video together about my (arduino-based) datalogger, it's been interesting developing it and maybe some fire enthusiasts would like to record temperatures.