Sarra M Donathan

Yes it does look like that first link. The burn tunnel may be 4.5 inches... I have it going all the time so it's pretty hot and never thought to measure beforehand but it is smaller than 6 inches.. but 4.5-5 maybe right. I will definitely pull it apart this weekend and or next to redo some of the points that have been mentioned.

Byron Campbell wrote:Al's got a good handle on it. But I'll go ahead and post what I've written apparently at the same time as Al:->

Sarra, you mentioned that the burn tunnel is 4" high, which is difficult to achieve with standard firebrick, unless the builder did something really creative when constructing it. This assumes standard dense firebrick, when stood on edge to construct the burn tunnel, and would make tunnel height at minimum the width of a single firebrick, that being 4.5" + mortar thickness. Or perhaps a different that usual brick layout was used. Is your J-tube built like the brick layout example at the top of this page?->

https://permies.com/t/40994/rocket-stoves/Rocket-Mass-Heater-Builder-Guide

About insulating the riser, no steel pipe in that configuration -- it'll burn out shortly. Think about wrapping the firebrick riser's exterior with a singe 1" thick layer of ceramic fiber blanket insulation, then wrap that with something like 1/4 inch holes hardware cloth, wired in place around the blanket. There's a good photo of this on Kristie's page here, lots of photos really, of a workshop built cob rocket mass heater:

https://permies.com/forums/posts/list/1000/26232

Insulating under the J-tube will require a complete core rebuild. To avoid that, one option is to make the burn tunnel taller than the correct size to accommodate lining its floor (front to back) with about an inch thickness of refractory insulating material. I.e. ceramic fiber board, or insulating kiln brick. Both can easily be cut to size with an ordinary carpenter's hand saw and won't need to be mortared in place or anything. These are soft materials and will tend to wear out quickly with wood abrasion, cleaning and etc. But with care it will last long enough to get you to your move.

I will pick up some of that the insulate it with chicken wire and try and reduce the top by an inch as well.

allen lumley wrote:Sara ; About lighting everything up when you re-shoot Your Rockets Video ! Try this as a mental exercise, its late at night, dark cold, and you and a friend are alone

on a lonely road with a front flat tire and dead batteries on your cell phone ! Got the picture? You have jack, spare tire, owners manual, lug wrench ! Now if you just

had some light ! You have some laundry in the Car. You leave the car running with the lights on, Your friend stands at the front corner of the car holding the sheet to

reflect light from your headlight towards the front wheel well, the glow of diffuse lighting is Even better than a flashlight !

O.K. with a sheet or two and a table lamp you will be able to light up the back side of your RMH like a professional Video Shoot !


Your Feed tube is big enuf, regardless of what you do and how many further versions of your rocket stove you live with, partially blocking off the top with that brick

will help you many more times !

When building up your burn tunnel you should err on the side of tall rather than wide !

I am concerned that you have used refractory cement to coat Bricks and things. When thou move, you will have to be very careful and work slowly to salvage as

many of those bricks without breaking them, you can however cement them back together this way !

Yes, the outside of the stack of bricks that is your heat riser should have insulation around it, your question about putting any stove pipe down the center of your Heat
Riser is a good one, but that pipe will not stand the temperatures created, it would be destroyed before you move !

Roxul or rock wool insulation comes in batting, and you should be able to get it at most building supply stores ! Lowes, home depot, Mennards - - - - at that location,

on the outside of your Heat Riser it can be held in place with a wrap of chicken wire ! If while you are in there you can use a little more structural Cob (like you used

to seal the bottom of the barrel last time) to shrink the gap between the Riser and the Barrel 1 full inch, I will guarantee an increase in temperatures at the top of the

barrel and more heat in your basement ! the gap between the wrapped riser should never be smaller than 2'' and can be Bigger!

For the good of the Craft! Big AL

I measured the top of the barrel in the center of the top by placing a magnet stove pipe therometer on it and it got to 430 degrees. Before I was using a digital thermometer that wasnt reading correctly.

Yes the burn tunnel is has a 4 inches tall by 6 inches wide hole and goes for the length of three firebricks. The j tube is not insulated because I needed the stove to last about 3 -4 months as we are moving soon. I thought since it's a small house that wouldn't be important. It just has fire bricks with the barrel over top and then the cob is around it to seal up everything. Under the J tube is a layer of bricks held by refractory cement. Below that is concrete floor. I say 4 inches in the feed tube because was three bricks high - the bottom as the bottom of the tube and the top as the top of the tube and the middle is essentially the feed tube .. which is about 4 inches tall maybe 5. It is a firebrick stood on it's side. Then on the back of the barrel, I believe you said it was a manifold is a 8 inch pipe then an 8 inch tee with cleanout a reducer to a 6 inch pipe and it stays 6 inches.

The burn tunnel needs to be bigger I can see as it is too small. Both from you explaining that is why the brick is helpful and in generally I would like it to be bigger so it is a little easier.

The manifold area definitely does not have the pipe protruding inside the barrel it is just on the outside to give the pipes something to attach to.

So basically you recommend the heat riser to be insulated and the feed tube to be larger. One thing we had thought of using to insulate the heat rise was a 6 inch stove pipe the heat riser is a 6-6.5 inch hole that would fit a stove pipe inside. Can I just stick the pipe in or does it also need to be filled in with something? If so what would you recommend?

- Thanks for your comments and explaining of terms.

The hole for the wood is 6 inches I believe. The horizontal area (think that is called the flue?) is 4 inches tall and six inches wide .. it's the area from where you put the wood to the second stack that is where the barrel. The barrel is 3 inches from the second stack of brick. The hole from the back of the barrel is 8 inches and has a decreaser and goes to 6 inches and stays six inches throughout. Here is a video after I modified a few things including some ducting.

Also turns out my digital therometer was not reading the barrel temp right. The actual temp of top of barrel is 430 degrees. Anymore modifications you think I need.

https://www.youtube.com/watch?v=48uCn_ldNu0

I have a small home maybe 600 sq ft. I work at home in the basement which is where the rocket heater is because that's where the chimney is. But there isn't a lot of space done there maybe 150-200 sq ft including the space the heater is in. What we did was do a later of fire bricks and make a small stack. FYI I use refractory cement to go around every fire brick there is 2-3 bricks where the flame goes horizontally and then a stack of fire bricks going up in a larger stack. It is 3 inches from the barrel I put on top. Then I mixed clay water straw and sand until it was a thick paste so if formed into a ball and dropped it stayed in a ball. I placed this mixture maybe 2 inches thick on the bottom 1/3 of the barrel. On the back of the barrel is a piece of stove pipe welded on. There there is a tee clean out as it angles a little because I need to go around the back if the chimney to get to the hole. After the clean out there is stove pipe going up at an angle and connecting to chimney. The piece that connects to the chimney also has a clean out. It's fairly easily to light concerning this is the first wood burning stove I have ever lit. The cob is now dry as it has been going for a week now and the wood is dry wood too. But the barrel only gets 200-250 max. Upstairs from the basement is a room to the left about 90-100 sq ft and a bathroom maybe 60 sq ft this area stays maybe 70-72. To the right of the basement is a gallery kitchen open dining room/living room maybe 300-400 sq ft. Then if you curve around the Kitchen and past the living room is my bedroom. FYI there is no ducting upstairs to the basement all heat is traveling up the stairs. The far right hand seems to stay about 66-68 when it's 15-30 outside. I am trying to get the temp 72- 73 on both sides of the house.

I will be going to pick up plastic for windows today to see if that helps. But I think the barrel should be getting hotter. Oh and I have a fan downstairs hanging trying to blow some of the heat.

I will go take a video and post on YouTube so you can see everything better and post it here. But ideas on what I can do?