Insulation vs inertia for the burn tunel?

Hi everybody.

Well, daft'ish question.

What we want in a rocket is high temps in the flame path, very high ones if possible.

I was wondering, even tho firebricks aren't insulative, they have inertia, so a burn tunel made only of firebricks oughs to work all right. Since heat will take it's time to travel through the brick, temps inside will raise to a high temp.

Am i completely wrong? What's your opinion on the subject.

The idea behid my thinking is to try to extract a smidge more "primary" heat out of a small rocket.

Thanks.

Max. http://www.traditionaloven.com/articles/81/insulating-fire-bricks

IMO insulation is always better than inertia for combustion. Inertia means you will be burning in a cooler chamber for longer, so fuel will be wasted. Insulation means the chamber gets up to temperature faster and so burns everything sooner.

Insulation is the ticket down in the burn-works. Period.

So insulation firebrick should do no?

You mean that really light weight stuff?
Yeah, that'll work. Might not hurt to insulate around that too, the more the merrier.
Oh, and I wouldn't use the ultra light weight brick for the feed, the stuff is fragile and should really only be where you won't accidentally poke it or smack it.

Satamax Antone wrote:Hi everybody.

Well, daft'ish question.

What we want in a rocket is high temps in the flame path, very high ones if possible.

I was wondering, even tho firebricks aren't insulative, they have inertia, so a burn tunel made only of firebricks oughs to work all right. Since heat will take it's time to travel through the brick, temps inside will raise to a high temp.

Am i completely wrong? What's your opinion on the subject.

The idea behid my thinking is to try to extract a smidge more "primary" heat out of a small rocket.

Thanks.

Max. http://www.traditionaloven.com/articles/81/insulating-fire-bricks

The "standard" RMH uses firebrick for the burn tunnel. Insulating cob outside of it generally. I have seen the riser (where heat is even more important) made from fire brick too. The time to heat up is not that long and it is robust physically. Try and see. For trial clay brick or even cement brick will work... though the cement brick will not last long.

Thanks a lot Len.

Well, i've seen it all too. My litle thing in the workshop works all right. Tho, it's not big enough i need a faster way to heat the workshop up.

Satamax Antone wrote:Thanks a lot Len.

Well, i've seen it all too. My litle thing in the workshop works all right. Tho, it's not big enough i need a faster way to heat the workshop up.

A forge? All kidding aside, you may actually have a use for an iron stove. Even if it has to be close to a door for an exhaust to run out. Mass is good for long lasting heat, but iron with little mass is better for fast heat. A rocket style may be able to work... but you may need a 8in or larger riser for the amount of heat you want. You have a stone shop, once you get the temp. of that stone up it will keep things warm for a bit. there is not a one size fits all solution. Even in Russia they might opt for an iron stove for your use.

hanks a lot guys.

Len, i have another requirement, no smoke. I was wondering how clean a pocket rocket burns. Because this would be about the best aproach. With an insulated heat riser and barrel to extract the most heat as possible.

But without an insulated burn tunel.

Satamax Antone wrote:hanks a lot guys.

Len, i have another requirement, no smoke. I was wondering how clean a pocket rocket burns. Because this would be about the best aproach. With an insulated heat riser and barrel to extract the most heat as possible.

But without an insulated burn tunel.

heat in = heat out. Getting the hottest flame is best (least smoke). If that means insulating the burn tunnel, the heat generated there will still get to the heated space farther down the flue path. The real measure is the exhaust temp. Put a second barrel at the output of the first (or several feet away to spread the heat) input and output at right angles or use a mini-riser to get the input gas sort of moving up... add a third barrel if there is any heat left in the exhaust of the second... the exhaust of the third barrel may be cool enough to want to travel downhill If the burn area gets hot enough there should be no smoke so let it run down a hill... maybe lift the third barrel so the flue can run downhill out of the shop. (and so water can drain ) Don't do this in a hollow as the CO2 will collect.

Note: no experience here, just speaking off the top of my head...

Pocket rockets don't burn as cleanly as a full blown rocket stove, but they do fairly well for themselves.
Attaching a bell, or multiple bells to a pocket rocket is an interesting proposition. Never been done before (to my knowledge) and I've no idea how it would work.
It DOES sound promising, so, I think I'll try it.

Kirk Mobert wrote:Pocket rockets don't burn as cleanly as a full blown rocket stove, but they do fairly well for themselves.
Attaching a bell, or multiple bells to a pocket rocket is an interesting proposition. Never been done before (to my knowledge) and I've no idea how it would work.
It DOES sound promising, so, I think I'll try it.

I hadn't meant with a pocket, I would still use a burn tunnel/riser in the first bell... just in this case no mass. He has a large uninsulated, stone walled, shop IIRC, and a 4-6inch pocket rocket is not going to give enough heat. 8 inch or bigger, I think. Even then it would be going the whole time he was using the shop... I don't know what that would do for the wood at night getting chilled, but if enough heat soaked into the walls it might be ok.

This is a unique use, probably not something that would work anywhere else. (at least not in a wood framed insulated "stick house") There may actually be enough mass in the building that a high mass heater won't work... This would be a great situation to play with as it would test out stuff we don't see anywhere else. I don't think that will happen though the testing will be, "it feels nice" or "well it's better than before" or "that didn't work, I'm still cold".

Len Ovens wrote:I hadn't meant with a pocket, I would still use a burn tunnel/riser in the first bell... just in this case no mass. He has a large uninsulated, stone walled, shop IIRC, and a 4-6inch pocket rocket is not going to give enough heat. 8 inch or bigger, I think. Even then it would be going the whole time he was using the shop... I don't know what that would do for the wood at night getting chilled, but if enough heat soaked into the walls it might be ok.

Ah, right.. I misunderstood.
Still, I can imagine piping pocket rocket exhaust into a series of bells. You'd get a LOT more out of pocket rockets that way, they typically pump a HUGE amount of heat, it's just that they pump it straight out the chimney. :>/

This is a unique use, probably not something that would work anywhere else. (at least not in a wood framed insulated "stick house") There may actually be enough mass in the building that a high mass heater won't work... This would be a great situation to play with as it would test out stuff we don't see anywhere else. I don't think that will happen though the testing will be, "it feels nice" or "well it's better than before" or "that didn't work, I'm still cold".

In cob houses, we get a good deal of thermal mass. The comparison wouldn't be exact, far from it. Stone is more conductive(depending on the stone), heat tends to move through it faster than cob.

Anyhow, An ultra-light rocket stove, running into successive bells is an interesting idea too. Brilliant, I'd say.
Remember that BOTH the intake and exhaust come into the BOTTOM of each bell. It's helpful to set the exhaust slightly lower than the intake.

Kirk Mobert wrote:

Anyhow, An ultra-light rocket stove, running into successive bells is an interesting idea too. Brilliant, I'd say.
Remember that BOTH the intake and exhaust come into the BOTTOM of each bell. It's helpful to set the exhaust slightly lower than the intake.

Right, and make the exhaust in such a way it drains any water (not steam) somewhere it won't hurt anything or freeze before clears away.

I've seen a stove made from a 100lb gas cylinder, with a brick lining work well. It didn't have to be continuously stoked. It wasn't even a proper rocket. It was run for about an hour to get the whole thing hot, then drip fed. It was just a radiant heater, and you needed to get out of line-of-sight if you wanted to cool off at times.

Len, you've been inspiring me.

So, i have bought castable. I will reuse the tall gas bottle i've used as a barrell earlier on. Make the burn tunel and first cast part of the burn tunel into a small 13kilos gas bottle, as per my first rocket. I will cast the rest of the burn tunel too. So that's durable. Vermiculite mixed with castable mix. I have all the proper tubes but one iirc. I will use the other gas bottle i have leftover as a bell, with the tap on the bottom as a drain. Inlet into the bell, 6 incher. Outlet 4.3 incher. Do you think this ough to work?

Big question i've asked somewhere else too.

How do i mix? I guess i mix once the castable wet? Half and half by volume? More vermiculite than castable? Do i vibrate?

Thanks a lot.

Max.

Satamax Antone wrote:Len, you've been inspiring me.

So, i have bought castable. I will reuse the tall gas bottle i've used as a barrell earlier on. Make the burn tunel and first cast part of the burn tunel into a small 13kilos gas bottle, as per my first rocket. I will cast the rest of the burn tunel too. So that's durable. Vermiculite mixed with castable mix. I have all the proper tubes but one iirc. I will use the other gas bottle i have leftover as a bell, with the tap on the bottom as a drain. Inlet into the bell, 6 incher. Outlet 4.3 incher. Do you think this ough to work?

Big question i've asked somewhere else too.

How do i mix? I guess i mix once the castable wet? Half and half by volume? More vermiculite than castable? Do i vibrate?

Thanks a lot.

Max.

As you can probably tell by looking at my project... I have zero experience mixing that stuff. I think the idea is to have mostly vermiculite, with just enough cement to hold it together. The stuff they show in the video is with cob, so I don't know how well that translates to castable.

Yes Len, i know. And i think most of the people besides Peterberg don't know either. Well, we'll see!

Hey Max, Maybe I'm not so crazy after all... or else there is someone else just as crazy

Take a look at this one with the downhill exhaust:

http://mha-net.org/docs/v8n2/wildac12b.htm

It looks to me to exhaust about 10 feet lower than the firing hole. It is kind of a brick rocket... but with a larger fire box. The builder is thinking it could be exhausted into the sewer...

The one problem seemed to be getting the exhaust temp. low enough. You can see they draped a wet blanket over the exhaust pipe at one point. I think a lot of the smoke when they first ran it was steaming from the still wet heater. I think running the exhaust through the ground could work well. Maybe even running "fins" or sheet metal into the surrounding earth might help. Cold out side air could be run beside the pipe for prewarmed fresh air.

Hello. I am currently making a RMH out of fire bricks. The test burns worked out great. This week we will be insulating the heat riser. After it is all insulated (hopefully today) I will post another video to see the improvements.