Shop Rocket Heater Questions

Hello all I am Billy, I live in central Alabama. I am knew to the forum but I have been reading and researching the Rocket stove/ heater design for roughly a year. And I think that I may have more questions now than before I started. The best thing that I HAVE found is that this is the best place to get the correct answers to my questions.
I am wanting to build a heater for my new garage that I am in the process of building now. I want to build a free standing heater that will warm the shop up, but still not take up a lot of floor space. Any and all help will be Highly regarded as well as appreciated.
These are some of the things that I asking for help on:
1. What would be my best and most cost effective way of insulating the burn chamber?
2. Will adding an adjustment for air below the feed box really be necessary?
I am sure this is going to lead to a lot of other topics with some great answers . There is such a broad spectrum across the net about these. Thank you in advance for all help. Billy

First a few questions. Do you plan to use the shop every day, or just once in a while? How big will it be, including height? What sort of insulation will it have, and how many doors/openings?

1) "Best" and "most cost effective" are often different answers. They also depend on what resources you have, and the price of some materials in your area. Insulating firebrick, or various types of ceramic fiber board, may give the best insulating performance but can be expensive. A mix of perlite and fireclay can be very inexpensive and work quite well. Cob with lots of straw or sawdust in the mix can work and be dirt cheap.

2) A rocket mass heater does not typically have adjustable air controls, and should not have a damper in the chimney. It is designed to run full bore whenever it is burning, and be dead out the rest of the time. You can typically cover the feed tube with a couple of bricks to keep drafts out when the fire is not burning. If your floor space is limited, and you don't anticipate needing to keep the area warm around the clock or have a warm bench to sit on, you may want to try a vertical "bell" type of heater with minimal mass.

Hi Billy.

I'm in the middle of building a batch rocket workshop heater.

http://donkey32.proboards.com/thread/1817/starting-build-220mm-rocket-double

If that could give you ideas.

And it started last spring like this.

https://permies.com/t/44806/rocket-stoves/Cobbling-workshop-heater

Hi Glenn, I will be heating almost every day and the area that I'm heating will be 20 X 24 X 9. Insulated with R-13 with two windows and a bay door. The windows are thermal so I will have a good area to work with. I have tried to find perlite but so far no luck. I can get fireclay with no problem so that part is good.
I think maybe what I'm wanting to build is a bell setup, I'm not sure. But I will do some more checking to understand the difference. I hope I answered your question's and I know that you have helped me. Thanks Billy

Satamax Antone wrote:Hi Billy.

I'm in the middle of building a batch rocket workshop heater.

http://donkey32.proboards.com/thread/1817/starting-build-220mm-rocket-double

If that could give you ideas.

And it started last spring like this.

https://permies.com/t/44806/rocket-stoves/Cobbling-workshop-heater

Thanks Satamax, I checked out both of the links and I like the setup. I do have a couple of question: is the first part of your build what is called a bell style? and if so that is what I'm trying to build. How much of a difference will the box to the right make and how? I understand that it is a collector box. But for the room would it be worth it in a small shop? You guy's have the answers I just have the questions..... Thanks for the help Billy

So Billy, both setups are kind of bell ish.

The first one with barrels

The first barrel on top is like a normal rocket, heat riser going to one foot from the top. People call that a bell sometimes but it isn't it's a downdraft radiator. Doesn't make much difference at this point.

Bottom barrel, where the firebox is, is filled with perlite, so it's not active.

The second column, was a mix of bell, above the inlet tube, where the gases rise when hot, and drop down once cooled against the walls. And downdraft radiator below that inlet tube.


A downdraft radiator or channel has more effect on gases, hindering the draft a bit more than a bell, as the hot gases, being less dense than heavier ones, get pushed upwards by the later. We usualy say, hot gases rise. So the downwards movement in such a channel is not as natural as what occurs in a bell.

In a bell, you have the downdraft movement occuring before entering the bell. Via a pipe or another bell or downdraft channel. Or you could have a raised bell, which doesn't have that problem.

Then, you have the gases entering the bell, rising upwards inside, cooling at the contact of the walls, then droping down being replaced by hotter lighter gases , exiting into the chimney, at the bottom. The gases being still hotter than the surounding environement, they rise again, creating the draft.


System 1.5, with the barrel, and big tank, was quite nice, as the first downdraft radiator didn't have near enough surface area for cooling the gases, the bell tank, where you can see inlet and exhaust at the same level on the bottom, was nicely radiating heat on it's whole surface.

Now, system 2, the evolution in the same spot, has 4.25m² of internal surface ( aproximately 43sqft) and despite the bigger firebox, it's shedding a lot of heat. And the big tank, which is planned to be covered by the bricks you see at the bottom, and thoses filled with mortar; that big tank barely gets more than lukewarm now, for the first hour of burning. Well, it all depends on tha rate of burning, and how cold it is outside.

Altogether, i have about 10.6m² of ISA (internal surface area) Which is about the limit for a 9 incher batch rocket. I want to add mass now, but lack time!

Hth.

Max.

http://donkey32.proboards.com/thread/1359/bell-explanation

http://donkey32.proboards.com/board/6/reference-library

Satamax Antone wrote:http://donkey32.proboards.com/thread/1359/bell-explanation

http://donkey32.proboards.com/board/6/reference-library

Thanks Max. That answered a lot of my questions. It was so interesting that I started following links from those forums and ended up reading for a couple of hours. I finally found vermiculite yesterday and picked it up, so that is out of the way. My plan is to start work on the 6" tubing this weekend and get the burner assy. welded up and maybe get it mounted so I can start insulating around it. I will post my progress as I can. You have been a huge help and I'm sure that I will be getting back with you. please lets keep in touch. Thanks Billy

You mention 6" metal tubing for the burner - are you aware that that extreme heat area will corrode and destroy a metal liner within a couple of heating seasons more or less? The combustion zone of a RMH needs to be masonry (preferably firebrick) to avoid deterioration. Ask Max about this, he can tell you about how one of his early experiments died quickly.


You have probably seen lots of youtube videos of people welding up their rocket cores... what you don't see are videos where they show how well those cores held up to a winter's hard use. A few have done this, as a post-mortem showing how they failed.

not mine, bur best vid to be aware!

https://www.youtube.com/watch?v=7RyvsZD1_CU

Glenn Herbert wrote:You mention 6" metal tubing for the burner - are you aware that that extreme heat area will corrode and destroy a metal liner within a couple of heating seasons more or less? The combustion zone of a RMH needs to be masonry (preferably firebrick) to avoid deterioration. Ask Max about this, he can tell you about how one of his early experiments died quickly.


You have probably seen lots of youtube videos of people welding up their rocket cores... what you don't see are videos where they show how well those cores held up to a winter's hard use. A few have done this, as a post-mortem showing how they failed.

Hi Glenn, I'm not going to build a RMH. What I am going to build is a stand alone vertical bell heater, I have thought about the short term life of the metal J-tube and that is acceptable with me due to the fact that this one is temporary until I get my new shop set up and arrange it to see if I can install a RMH. Thanks for bringing this up though. All advice is welcome and appreciated. Thanks Billy

Hey Max I would like to see a pic. of the one you are using completed. I am still contemplating a batch unit if I find that I have room later on. I was wondering would it still work if you moved it farther away from the heat source, but insulated the pipe. Just a thought......... Have you had a chance to take any temp reading yet or is it to soon? When you do could you post them? Thanks Billy

Hi Billy.

Well, this is prety much what it looks like as of late.

Firebox with hinged door



Whole stove, without the hinged door. The right bell (tank) will be covered with the red bricks you see at the bottom. And thoses will be filled with concrete.



Batch rockets with bells are a type of RMH. The batch evolved from the cooking L tube , and the fact that J tubes need constant attention, tend to smoke back etc. First attempt was done by Donkey and Canyon, and the most work done refining thoses has been done By Peter van den Berg. See this thread.

http://donkey32.proboards.com/thread/511/adventures-horizontal-feed



And please, don't use metal inside the firebox nor the heat riser. In my early attempts at a J tube (a cyclonic one!) i killed industrial hydraulic tubing, within 14 burns. About 32 hours iirc. The metal in the elbow had swolen like puff pastry, Literaly, the 8mm thick walled tube was more like 2cm thick, and flaking off, spalling. And the gas bottle i formed the cyclonic chamber out of collapsed under it's own weight. That meand that i got the metal to the white. So if you want a working stove, even temporary, use refractory materials. Dry stacked bricks held by wire do the job, and can be reused.

Anyway,


"Metal is doomed!"