Geo Schoonmaker

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since Nov 04, 2012
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Recent posts by Geo Schoonmaker

I've been using the Fiskars 36" splitting axe for a couple weeks now, I think it can replace my 8lb head maul that I've been using since I was 15. The fiskars is lighter, swings faster, easier to aim, and seems to have a lot of one strike splits. It also works reasonably well as a heavy axe, making it a lot more versatile out in the woods.
4 years ago
Thanks for the bump, Allen! I've done a lot of modifications to the boiler since I posted in this thread and have documented it all on video. Here's my youtube playlist from start to finish:

Video #7 shows the old insulation after I removed it from the boiler. It held up well except for the very top, the constant abrasion of putting in firewood was too much for it.

This year, I switched to a more proper material. I used a ceramic fiber blanket, coated with a hard liner to protect it. So far, it is holding up so much better. For those who don't have broadband to watch videos, I've got a lot of pictures on my blog:

You'll notice the heavy inspiration from batch burning rocket stoves in the videos and pictures. This setup creates more of a side/down draft combustion than a down draft found in commercial smokeless wood boilers. The firebrick in the back and secondary chamber all glow a brilliant orange to yellow when it is up to full temperature. The secondary injectors bring air back to that chamber whether or not the induction blower is going.

Since shooting my last video, I've been able to procure some well seasoned wood. What a difference it makes! It burns smokeless within 5 minutes of startup. When the induction blower kicks off, it doesn't smoke. When wood is added, no smoke. I have yet to see a spark or ash make it out of the stovepipe. It has been the most successful wood burner I have built, and I believe it to be the cleanest. No wood burning odor at all, and unlike my first rocket boiler, no fly ash is released(I know that's a coal term, but what I mean is the ash that gets swept along with the exhaust, to be deposited outside the stove). I plan to do a new update video next Friday showing how well it burns with all the tweaks I've done since the last video and using good seasoned oak.

The biggest negative is the small firebox. If it is cold out (20F or below), I do have to fill it every 4 hours. That will be my project next year, along with building an insulated shed to house the boiler in for better efficiency.
5 years ago

Jared Blankenship wrote:Very interesting! I stumbled onto your rocket boiler videos a few months ago while searching for heating options. What happened with the rocket project? Is this one going to be more efficient?

I have radiant tubing in the slab of my berm home that I'm currently not utilizing. I'd like to do something like this in conjunction with solar thermal collectors to heat a 500+ gallon storage tank. Do you think it would be feasible to heat that much water with a system like one of yours?

I liked the rocket stove, but the feeding system was a chore. The extra steps of bundling the wood and dropping wood down the chute was not worth the effort. Because of that, I wanted to try a different way of achieving clean combustion. So far, I've been very happy with this system and have made several modifications already to make it even better.

A system like this or the rocket stove will work great for heating a large storage tank. I, too, am interested in using solar for heating. The sun doesn't have to be felled, cut, split, and stacked for use

My old family motto is, if it works don't fix it, I really ike the Float, easy to make and replace if and when needed ! Big AL

Thanks, Al! We must me distantly related
6 years ago
Here's the simple circulation system I designed for this boiler:

Earlier today, I measured the internal temperature at 1246 *F and rising. My thermocouple is only good to 1400 *F, so I didn't push my luck and removed it before seeing how high it would top out at. The exhaust 343 *F, so the boiler manages to extract a lot of heat from the system. I'd like to get that down to 275 *F if I can.

The homemade insulation works really well. The highest temperature I've measured on the stove body after several hours of use is 250 *F. This means a temperature difference of around 1000 degrees! I plan on using this waste heat to preheat combustion air to further increase efficiency.
6 years ago
With winter rapidly approaching, I decided to try a real simple outdoor wood boiler build. I had an old water heater and air compressor tank to use as raw materials. Here's what I came up with:

With the heavy insulation (the outside of the boiler for the most part is under the boiling point of water) and ample air supply, the burn is quite clean. It can also manage several hours between reloads. Here's a short video that shows the exhaust:

The real expense with this was hooking it up to a simple hydronic system. Fortunately, I had most of the stuff lying around from previous projects. I'll show how to hook it up in a future video. I also have several planned modifications that I'll document as well.

At any rate, it works quite well as is, so I'll have cheap heat this winter
6 years ago
Double post, but I wanted to share an update on my stove project. I've managed to slow the btu production while still producing pretty clean exhaust. With a bit more tuning, I think it can get back down to odorless exhaust. Here's a video of some of the things I've been trying:

The vortex generator, crude though it may be, seems to promise a shorter riser length. I'm planning on putting one in each of the firetubes of the boiler I'll be building over the next couple of months. The idea is to swirl the hot exhaust gases in contact with the firetubes, hopefully promoting better heat transfer. I'll test it with and without to see if it makes a difference.

I've got the burn time up to 2.5 hours, with the btu output down to 18k, so it makes a killer outdoor cookstove now.

Hope you all liked that update, I'm doing videos start to finish on the larger insulated build as well.
6 years ago
I live in Missouri, so our winters are really unpredictable. Last winter was horribly cold, of course, but most are up and down. A week or so of cold, then it warms up to 60 degrees, and then comes the snow or cold rain Wash, rinse, repeat lol

6 years ago

allen lumley wrote:

I Am surprised with the longevity you are getting from your concrete blocks, as you said some of them came from one of your earlier (forced air?)
Rocket Mass Heater RMH Builds -could you comment on the percent of your concrete blocks that were reusable from that earlier project ?!

On my outdoor rocket boiler, I used 8 solid blocks, 7 of which are reusable. Those all came from an homemade wood stove I built three years ago used to heat a steam boiler.

Being ready for the power outages and personal financial problems is about all the prepping I do myself.
6 years ago
Its been awhile since I've built a stove. I found that the gravity feed that I used in my outdoor rocket boiler, while it worked and was reliable, it was inconvenient to use. Bundling wood and dropping it down a 7 ft tall stack isn't fun when there is snow and its freezing cold outside.

I set out to build a stove that would be clean burning, not need constant attention, and be built with common materials. What I've ended up with is a hybrid between a wood gasification stove and a rocket stove. Even if smoke, soot, and smell is absent from exhaust, there can still be combustible gases such as CO, H2, and CH4 that are invisible and odorless. This became evident to me through a small rocket stove I built from a exhaust elbow inside a metal paint can. The inside was insulated with perlite. I noticed flame jets popping up around where the exhaust pipe came out the lid of the paint can. I believed this to be caused by heated air inside the paint can combining with unburnt fuel being exhausted, much like a wood gas stove.

This observation inspired me to add a secondary air injector to the heat riser of a rocket stove.

To get longer load times, I've constructed a larger firebox designed to burn entire logs at a time. The logs gasify inside the firebox and the wood gases are then channeled to the heat riser. They mix with air from a secondary air injector where they spontaneously ignite, thus providing clean combustion. Air temperatures from the air injector range between 650 and 700 C.

Here's a video playlist I put together on my prototype stove:

This small stove puts out a peak of 31K BTU and lasts 1.5 hours between needing to be reloaded. When you consider the only insulation this stove has is the concrete block that makes up its body, the clarity and lack of odor of the exhaust is quite impressive. It definitely works well as a outdoor cookstove.

In my full sized version, I will be insulating the firebox and heat riser to hopefully obtain even better results. Calculated run time with the larger firebox is 6 to 8 hours. Waste heat from the stove body will be reclaimed to further preheat combustion air, both primary and secondary. Heat will be extracted from the exhaust gas at the top of the heat riser by means of a firetube boiler (non pressurized) and pumped to an exchanger.

I hope you enjoy the videos on my little project. I'll be doing more videos on the larger version that I plan to heat my house with this year.
6 years ago

Frank Rasmussen wrote:Geo,

Thanks for your comment. I've read your web page and a few of your posts and it seems that you have had a similar idea to me. One of the first things that occurred to me when thinking about RMH technology was to create a water heater, storage and radiator system as you have done. Well done on your implementation.

I keep thinking of how to make the system safer, e.g. by making an insulated fire box rather than using a feed tube. Obviously if you do that, you have to incorporate some secondary air into the system for secondary combustion. This system then starts to look a lot like the EPA non-catalytic stoves, since they have somewhat insulated fireboxes and preheated secondary air.

Thanks for the feedback. The firebox and heat riser is actually heavily insulated, about 8" thick refractory. The feed tube in my more recent videos simply guides new fuel into the fire, no gasification or combustion occurs there. Waste heat that travels up the bottom portion of the feed tube is used to preheat combustion air and the fuel, adding to efficiency. My feed tube and no jam method of bundling the fuel is the secret behind not having to tend the fire constantly. In fact, with the weather websites that show hourly temperatures, you can add wood sized to meet temperature demands automatically.

Another benefit of the feed tube is that you do not need a thermal mass to store the heat produced, simply create heat as you need it. This works really well where I live where night time temperatures can be quite cold, while the day is very mild. If I had a large thermal mass radiating heat, I'd have to open my windows and let it out during the day, wasting fuel.

The only time I ever tend the fire is to fill the feed tube every 6 to 8 hours or if I need extra hot water for bathing or cleaning. In that case, I simply add a piece of wood horizontally into the firebox, giving the extra boost needed. This is where I came up with the dual plane rocket stove name.

This upcoming winter will be my third year using this system, each year I improve on it based off my experiences the year before. Once I get all the kinks worked out (hopefully after this winter), I intend to distribute detailed construction plans for those interested.
7 years ago