Keith Coldrain

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since Dec 27, 2014
British Columbia, Canada
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Recent posts by Keith Coldrain

Regarding sources of cob. I don't know. My only knowledge of it is what's left over after I eat the corn.

Should Glenn Herbert read this, congradulations!

About a month ago my curiosity lead me to investigate the materials used for those little backpack rocket stoves and sure enough, they used similar materials as used in blast furnaces. I'd seen mention of one of those materials on the donkey site, (ceramic fiber insulation).

But just a few minutes ago, I did a site search of both forums using Google and surprisingly enough, you were the only person on either site to mention refractory metal. Koodos to you.

Unfortunately that means all this talk about metal component failure has been about as useful as a bag of rocks to someone who's called overboard. Since it appears that those few who used, or may use ceramic fiber, don't or didn't know that refractory metal is used to help it structurally and prevent those nasty fibers from going places they shouldn't. Who knows, someday soon people might discover ceramic coatings also intended to help with the same products.

You would think that after all this time and the expenditure of effort by so many people, that this type of information would be common knowledge in both forums. Maybe now someone will make the effort to do a search for this info. I'm getting tired. Time for a break.


5 years ago

Glenn Herbert,

The fact that inflated or uneducated or unsupported claims have been made for RMHs does not invalidate the sober research and development that has been done on them, nor do the misled experiments posted on youtube.
~~~~~~~ snip ~~~~~~~

Yes, these will destroy metal, which is why metal is not used in durable builds by people who know what they are doing, but firebrick is very durable, and with matured practices the typical RMH might come to be designed like some masonry heaters, with a lining of firebrick at the highest-wear areas that is There is still research to be done.

Mistaken claims of metal "melting" temperatures aside, metal does distort and/or degrade at the reported temperatures in the presence of oxygen or combustibles. So nobody who knows what they are doing uses it in these areas. The reason there are so many failures is that this is a relatively new (to us, anyway) area with a lot of non-professionals experimenting. Some of them may hit on real improvements. Some already have. There are many, not just some, RMHs that work very well, and deliver heat with radically less wood than established technologies. That is a real-world measure of efficiency.

Research and experimentation are good, but it would help if there had been somewhere like a forum where peoples work was coordinated to record failure and success. And hopefully reduce the former.

Having a place that listed effective and recommended building materials, along with alternate optional products, (like premade cores, or ceramic fiber instead of ceramic lining, etc), would be nice. Similarly for things like heat exchangers for those that find "mass" impractical. I spent weeks hunting up and stumbling onto information. For instance, I thought a stainless steel heat exchanger would be hard to construct because one would normally need a plasma cutter, a tig welder and cnc machine to work with it. But then I found flux cored ss mig wire, masonry abrasive cutting disks and masonry (tungsten carbide) drill bits, could do the same job.

People shouldn't have to hunt for that information for that long a period. A forum should have a library of collectively gathered information relating to its purpose.

I didn't come here to be critical of constructive well intentioned efforts, I came to try and make sense of some radical claims and get the straight scoop on rocket stoves and heaters, but the information I've seen here goes from one extreme to the other.

And before anyone comments about a stainless H.E. doing a meltdown, they should know that when a column of hot flue gases enters a larger and cooler area, its going to cool down partly because its supposed to transfer heat to the metal and partly because the hot core mixes with the cooler surrounding gases.

Regarding the distortion of metal you mentioned, to thin a metal, or the use of common steel, instead of mild steel, would be my guess. Wood stoves/heaters have been around long enough that one would think most people knew they used thick metal. I don't know what they use on "Air Tight" stoves, but I've seen them buckle and bloat, (and rust out).

Looks like the weather is going to take a turn towards warmer here over the next few days so I may be able to squeeze in some experimentation of my own.

Good luck!


5 years ago
Misinformation is all too common when it comes to rocket stoves. The highest temperature I've seen reported was 1900F at the center of the flame inside the heat riser. If someone has a link to higher test results I'd like to see it.

I'm one of the biggest sceptics of the claims made despite not voicing my opinions here. But some of the things claimed just make me shake my head in disbelief. I have better things to do with my time that to take issue with all of them, but incorrect informaton about things as simple as the melting temperature of metals should at least be accurate. But no. I keep seeing numbers that are simply wrong.

All those YouTube videos with stoves made from steel pipe and boxed steel could have been made from wrought iron and been just as usable and just as resistant to meltdown, (although 446 stainless would be nice). Check out metal melting temperatures here:

I personally think these stoves when used as stoves are a poor to fair design that could be improved, but as heaters, they're ok stoves for use outdoors.

Since they can't be independently tested using epa testing, there's no way to know how they compare with two stage combustion stoves like the Lopi Endeavor rated at 82% efficiently. And given the choice, I'd rather build my own stove or modify an old one that's stood the test of time.

Now if only spring would come early.

5 years ago

This thread is about useful tips relating to; solar panels, charge controllers and batteries. It is NOT about complaining. I realize it can be hard to raise this topic without relating problems that can be encountered when dealing with this subject. And if someone wishes to start a topic for complaints, I'll likely chime in.

That being said, I offer the following words of wisdom and experience.

Just about two years ago, I bought a couple of deep cycle batteries from Napa to replace the Trojan brand ones that came with my old travel trailer. The Trojans were previously charged off the tow vehicle but having sat for a couple of winter months, they had bloated and shorted out a couple of cells each. Hindsight is great, but foresight would of been more help, as I should have replaced with the same brand of battery.

So I ordered the biggest panel I could afford, a 100 Watt 12 Volt that came with a 12v/24v, 20 amp PWM charge controller. Fast forward past some issues with the batteries.

If not for the issue with lack of sunshine, I'd say all is well. Despite what people said about cheap Chinese stuff, the panel has worked just fine, survived s few hail storms and wind storms with no noticeable blemishes. And i don't think the bouncing around on my little trailer has helped preserve it.

Likewise withe the charge controller.... But...

Had I known then, what I know now. I would have bought a 30 or 40 amp MPPT charge controller and a higher wattage panel, (at least 200 watt), but only one battery, (about 110 amp hours).

Then when I had the cash to spare I would have doubled up on what I had, running each set of panel/controller/battery separately. I would have the load connected through blocking diodes, allowing proportionately equal draw on each system.


1) try to get batteries with an amp hour rating that's at least double your panels wattage rating.

2) Try to find a MPPT charge controller. It will convert slightly more of your panels output into stored usable power in your battery. It also works better than the PWM type in cold temperatures.

3) For small to medium sized systems, try to use a charge controller for each battery.

A) Despite what the pro's say, its virtually impossible to find two or more batteries to use for a battery bank that are and will continue to be exactly the same after years of use. And you can be sure that the weaker battery will keep all better ones connected with it from charging properly.
B) Better charge controllers have a remote temperature sensor to tell the controller if a battery is getting hot, (I guess). Having more than one battery means likely different temperature readings that could mislead the controller.
C) Likewise with the controllers ability to properly detect the batteries SOC (State Of Charge). With more than one battery the controller will only detect the lowest voltage in a set of batteries and charge all the batteries connected to it based on that information.

4) Reason why solar doesn't work as well in northern climates at this time of year. Its winter. Which means shorter days and less sunshine on panels, due to the angle of the sunlight in relation to the earths axis. What can be done about it? Try something shiny to reflect more light onto the panel, (like a mirror). Google it. You'll see.

More to come.

5 years ago

Yeah type of wood, moisture content, dampener settings and loading wood sideways for longer burns etc, can all prolong or shorten burn time/heat output. Personally, the fewer times I have to fuss with a stove, the better.

If that means I have to experiment in order to get the stove I want, then that's what I'll do. Hopefully when the time comes I'll have researched some more and have the benefit of not repeating other peoples mistakes.


I just like the look of this stove.

5 years ago
Hey Glenn:
I was going to post in the thread of yours with that link but I have a battery problem with this phone. Also means I can't watch that YouTube video until I get a replacement. If I find any similar links I'll post them.

Good luck with your project.

5 years ago

I'd been thinking of doing a retrofit myself, but I'm still looking for a suitable stove. I think there's two basic options for modifying an existing stove.

One being to modify the interior like in the link I posted. The other would be to add a deflector/reducer inside to limit the primary burn and prevent the drastic 30% or so increase in heat. Then add an insulated external secondary combustion chamber sans rocket stove style heat riser and add a preheated air supply to either option. (Preferably ducting the air from outside through an insulated duct.)

At least that's my thoughts on the matter. Hopefully when it warms up here in spring, I can locate a stove and
go to work on it.

I hope you can keep those of us interested informed on your progress

5 years ago

I know there are likely other diy wood stove heaters out there on the web, (with secondary combustion chamber and air supply), but this is the most complete one I've seen:

Its not for rocket scientists but you might need to experiment a bit. Looking at and getting measurements from, a newer model stove that has the secondary combustion chamber with secondary preheated air supply would be your best bet. If you have a wood stove sales outfit nearby, it might be worthwhile to visit them.

5 years ago
Jimmy Smith ^ ©

I'm wondering just how different your "older" lopi stove is from that newer very efficient lopi endeavor that has the secondary burn chamber? Maybe you could upgrade it with a little modification?
Just a thought.

And just a suggestion here, you might want to visit the website for advise on getting more out of your current wood stove.

As for your quedtion. There may be other mass heaters, but the only other one's I've looked at are at

They have some really nice units. Some with ovens too.

5 years ago
Hi Beth.
Regarding the earlier mention of:
"Iron and/or steel
can not withstand the effects o"High Temperature Hydrogen Attack'' and ''Hydrogen /steam Embrittlement '.
This applies respectively to steel exposed to over 400°C and copper exposed to heat. If your building an all masonry heater then it wouldn't apply. If your going to build a typical metal rocket thing, then using either a pre-made core, or diy ceramic, or diy ceramic fiber with or without a coated refractory metal lining, for the "heat riser"/ secondary combustion chamber.

Personally I wouldn't build one of these, but that's me. Having the skills and materials needed, I'd prefer to build a unit something like one of epa certified dual combustion wood stove/heaters. At about 400 lbs they're semi portable and burn longer and passed polution and efficiency tests.

5 years ago