Rocket stove slide allows for burning of 6 foot long firewood

Yes, the feed does have to be constrained to the same flow area as the horizontal tunnel. Air being forced down past the sticks is the only thing that forces the smoke / wood gas to flow down into the firebox instead of up. If the stick protrude above the feed lip, or if the feed is too large, or even if you get one big flat chunk acting like a damper up by the burn tunnel end and a gap behind it, there's an increased risk of smoke wicking back up the sticks without enough air drafting downward to suck it back down.

Such a wealth of knowledge here. I'm just getting started in this little adventure but I think I've stumbled on something that will help.
I just built a rocket stove for small scale testing before I continue and of course one of the things you see a need for is some kind of automated feed system.
My stove is a 4" burn tube of thick walled square tube (maybe 1/4") steel. Total chimney length is about 24".
For automated feed I decided to go with some kind of gravity driven system for simplicity.
I tried various configurations before that always resulted in some smoke up the feed tube or tray and after a few failed tries I made a chute that was canted at about 50-55deg, that results in a 4 x 5.5 inch tube about 6" long with a tray that extends another 8-10 inches that the wood sits on. I left the wood chute at 4 x 4 with the other section below as an air feed just like the shelf in a typical rocket stove. Instead of sucking all the air past the wood I think the air flow underneath creates a sort of venturi effect and a constant low pressure at the base of the wood feed chute.
Strangely, when the air tube was not parallel with the feed chute it didn't work nearly as well. I'm experimenting with tapering the air tube to increase the velocity but the cold weather has me hibernating just now.

The pics are poor and as soon as it warms up a bit I'll test some more to get the best configuration I can and weld it up and the clamps won't be in the way. I also made the whole feed tube hinged to make cleaning and initial lighting up easier.
More stove pics in that album if you want a better picture of the whole thing.
http://i828.photobucket.com/albums/zz206/Indyyeti/energy/rocketstove4_zpsa964f6e9.jpg
http://i828.photobucket.com/albums/zz206/Indyyeti/energy/GEDC1386_zpsf10708c9.jpg

Bumping an old topic here as I'm also interested in the idea of a way to automagically feed a rocket. It seems there was a lot of concern about the slide idea creating a chimney that would allow the smoke and/or fire to run back up the feeding slide. It occurs to me that if the feed slide were set at a much shallower angle, it would be much less likely to create a chimney. Of course, a really shallow slide wouldn't slide at all; the friction of the wood on the slide would stop it from moving. My thought is to replace the slide with rollers. Rollers create very low friction, so little that even a tiny slope is enough to cause anything resting on them to roll straight to the bottom. Companies like UPS & FedEx use them in their terminals and even their truck trailers to move freight easily from place to place:



Rollers would allow a very shallow angle gravity feed to work, thus making the chimney effect very unlikely. I drew it up real quick; now that I look at it again I drew it wrong as well. In practice, things would be oriented such that the wood would end up resting on the bottom of the firebox, not suspended in mid-air. But you get the idea.

I just watched a video series about a guy converting his rocket stove to pellets. One of his first problems was he kept his pellet supply and feed tube too close to the bell and they were getting too hot before they were entering the stove. He fixed this by using an angled approach like you have above. As long as your wood isn't all perfectly straight, you shouldn't develop a draft up between your logs. The only concern I have is if the logs hang up and stop going down. Will they actually stop burning, or will the fire move up the logs? I've been wondering about this myself, hope to see the results from your experiments.

Dale Hodgins wrote:   
    The plan is to build a U-shaped sheet metal slide which is set about 10° from vertical so that long lengths of firewood will lay straight and automatically feed into the rocket stove.

Hello Dale.

Did you ever try this?

What kinds of variables did you encounter?

jacob green wrote:

Dale Hodgins wrote:   
    The plan is to build a U-shaped sheet metal slide which is set about 10° from vertical so that long lengths of firewood will lay straight and automatically feed into the rocket stove.

Hello Dale.

Did you ever try this?

What kinds of variables did you encounter?

I found two people from the very bottom of the gene pool to occupy the cottage. They were afraid to have a rocket stove after talking to a few people with no knowledge of the subject. They are moving out in early March. I will build something there before the next heating season. Materials are on hand. I'll rig a simple slide, but only use it when I'm there. The first real test of the slide should be in heating a hot tub within a greenhouse. https://permies.com/t/31352/rocket-stoves/Dale-Oil-Tank-Hot-Tub

This video shows a similar concept at a smaller scale. A ring attached to the front side of the stove which hold sticks vertically over the feed tube.

http://youtu.be/ebGSAw2UKz0?t=3m56s

I've embedded the video below.

Hi folks. Brand new here. Signed up today to comment on this post. I do not have a rmh yet but live in michigan and have propane forced air furnace and its either rmh or the poor house. So I have been studying everything I have been able to find on rmh for several days several hours a day (Im on disability) former auto mechanic 30 yrs and try to hot rod most things and have been thinking about the same thing auto feed of longer lengths. My best thoughts were bell mouthing the feed opening on the rmh some and using either a V or 3 side shaped roller system. The rollers every 6 inches would not effectively constitute a chimney effect and I believe the wood wouldnt bind up either. I do think you will want to somewhat limit the blatantly warped and twisted wood. Also noticed some of the feed tubes on rmh are angled somewhat and believe these type would better work with the long feed addition. I know Im a rookie and may be wrong but it is what I thought. These thoughts came to me for a different reason. Im in a 2100 sq. ft. modular home and not to sure if my floor joists can handle the mass part. Im gathering parts now and hope to build my heater within 2 weeks using an old air compressor tank and J tube constructed of firebrick furnace cemented together with an angled feed tube and a 6 foot roller feeder. Exhaust will exit the tank and run inside as far as needed to cool enough to exit the house through an open window filled with cement board and to radiate as much heat from the exhaust as possible. The other reason Im wanting long feed is Im a little scared of the insane heat these produce and along with not having mass Im going to try a smaller longer lasting fire. Going to build and test in my garage first. If anyone here has thoughts they think might help me I welcome them and I of course hope I may have helped. When I find out if my long feeder works I will let you folks know. Thanks

I have been toying with this concept for about 3-5 years now, not having the chance yet to build it. But with all this info we all toss back and forth over the volleyball net of this forum, I continue to grow in my confidence that this is a great concept, naturally practical and efficient, and even work-saving. It is a concept worth all efforts put into it, as I think it is the best thing since the Ben Franklin stove.

First, where the wood comes into any burn chamber is really not too important. It could simply be a proper size and shape hole in the side. Anything further is improvement on a theme.
If designed so, that hole of whatever sort could/would also act as your intake of fresh air. There are various ways and mechanisms for tightening the tolerance and space around a log as it goes into the burn chamber.
- and along that like of thought, if you design cleaverly enough to produce an especially strong draft and intake, you could utilize that like the vacuum system on a car engine to do things.
The simplest of which, if nothing else, would be simply to suck up the debris that would inevitably collect under this feed system from the logs.
Brancjing up from that, there might be potential for central home vacuum - start the fire raging, vaccum the floors, the dirt is instantly removed and incinerated. - No bags or filters to change!

Onto my main intended point here -
In my own concept, one of the best utilizations for this would be if instead of the average wood pile, you have a large rack on which you put the logs.
There would of course be work in putting the logs anywhere anyway, but once on the rack, when you need the next log, all you have to do is turn a log to get it to roll off onto the feed and fgo back into the house!
So if it's horrid weather out, or its late at night, or you're busy with something else, or you're just being lazy, putting the next log on is quick and easy.

The design I am working on would actually be one, and inherent part of the structure itself. In constructing the home/building vent tubes are laid into the floors, walls and ceiling. It owuld be essentially air-tight.
Being a part of the fireplace/ventilation system, they could both warm and cool the structure whenever needed.
(Yes, there would be circulation/fresh air/etc.) This would all be done in a very rounded adobe/shotcrete type of construction. The right material for the vent tubes could mean that they could be used as framing superstructure, serving two purposes and saving materials/costs
The vent tubes in the ceiling take freash air and the the waste heat up there, and go back and open end at the far corners of the building, where it would naturally otherwise be the colder places.
Nearby, in other logical locations would be the vent tubes that go under the floor, taking the warmer air to warm the floor on the way to the burn chamber.
At the burn chamber, there would be 2 or three different kinds of tubing or channels around in circles both the base and the chimney of the burn chamber, the largest being for heating air, another for heating water, and possibly a third for something else. The air-tight system would use the draft up the chimney to work the system, and drawing in fresh air for circulation.
In this design, the various vent tubes could be switched, reverse the flow, individually regulated or closed by the most curious system you may have ever heard of, but one that would work like a charm!

I have redesigned this many times, and continually, and the funny thing is the question of how to implement such venting and regulation, and flow control, etc.... What hardware??? - NO hardware! lol...
Nomex and fiberglass Pillows ! These would not be exposed to fire ever, but considering the nature of this beast, would seem to make some sense.
In the construction of the building, quite rounded in various ways, very organic looking, the walls and/or ceiling might have ribs from the vent tubes and superstructure, and where the vent tubes meet would be a little hole, looking much like the hollow of a tree. There would be a pillow or two there, maybe attached with cords, that you could stuff into this spot or that spot to direct the flow of warm or cool air or shut it off to a particular spot.
Some few vent tubes could have a particular route for effect, like one dedicated to the bathroom, so that air from there would be taken directly out and not recirculated to any extent. - Like a 'fart' fan', lol... - but silent!
There could be a small vent tube, or system of tubes that could take fresh air from outside and instead bring it right to a particular spot, like above the bed.
If I can figure out the best, best, best way to make this, these vent tubes themselves could BE THE superstructure, overwhich abobe/shotcrete would be formed.
I have also accounted for and designed the system to work without any fire.

I have been studying the RMH and other types of rocket stoves/concepts. This whole concept I have just explained is very similar in function. You are maximizing draft, and utilizing it to do work, such as giving your fireplace its own bellows in effect, almost turning it into a blast furnace. I would simply suggest that tubes or channels or chambers around all burn chambers or hot hardware/areas to heat water and air, etc. and also using it to run a ventilation system for the whole structure would make the best and most use of that heat. You could also actually use that heat to COOL a building, if done right.

This log conveyor is the next logical step to the concept. I you use wood, you are going to have to move logs. But this saves cutting those logs into small chunks, which saves hours of labor, fuel and wear and tear on chainsaws and other tools, and if your are sick or thw eather is bad, getting more wood could literally take only seconds.

I can't remember if the other autors here have covered this, but I think the best place for most of this, especially the feed system itelf, should be outside the building.
You have a rack of logs, and a thing of wheels, rollers, or belt that is the feed stystem, the fireplace/etc. being on the other side of the wall, inside the building.
No firewood inside the home. No firewood associated debris, dirt, insects, etc. All that gets incinerated with the logs.

Also, where the feed system goes into the building, you could have a little door underneath, at ground level, where you could use a broom to sweep log debris into the burn chamber to use as kindling or just to get rid of it and put it to immediate use.

Also, personally, I am working on a system that would include the use of fryolator/deep fryer oil as a secondary, tertiary, or simultaneous fuel to accent the wood, and could also be used when needed as fire starter if you ever let the fire go out in the burn chamber. I am not persuing it with much gusto though, as most places do sell thier fryolator oil, whereas in the past many places actually had to pay to have it removed, and were glad to give it away.

I am also wondering that if you can make woodgrain alcohol with these same concepts, which would produce yet another resource or fuel back into the system.
- (No, that would not be the most efficient thing, but if you can find and use any waste heat to do it, then it would be beneficial and productive.

Ok, I wrote a small novel here.... Do I get a gold star??? lol...

John Abacene wrote:
Ok, I wrote a small novel here.... Do I get a gold star??? lol...

Course you do! It's an apple shaped one though...

kent smith wrote:Dale, glad to hear about the maples. Most of our wood lot is covered with maples and I need to thin some out. The crowns are so thick that on a sunny day it is dark and damp while walking around. Maples are the predomenent new growth on our place in the woods, but out in the pasture it is black locus and sumacs.

I hope you cherish and foster those locusts as we do. One of the most important trees on any farm. I hated to see them lumped in with the sumacs:-)
The guy we bought our homestead from took a saw along during our walkabout and proceeded to cut down every locust we came upon. Man did we give him an earful. He stopped that habit in short order.

John Abacene wrote:...
Brancjing up from that, there might be potential for central home vacuum - start the fire raging, vaccum the floors, the dirt is instantly removed and incinerated. - No bags or filters to change!

l...

Yeah, I want some of that!!

I have built a masonry stove and simulated a slide. Even with no actual slide, wood held in place by a thin stick , still can create a chimney effect.

This is something for outside only. I may determine that it is unsuitable anywhere. Time will tell.