G70 Stove Pictures and Use Report

I made “morning coffee” today on this stove. Unfortunately, I was also “experimenting” at the same time, so it took longer to get a decent fire than it did with “First Fire”.

The report on “first fire” and the original build is in the prior posting:

https://chiefio.wordpress.com/2013/02/24/g70-brick-stove-first-fire/

Today I decided to test out the “charcoal mode” in addition. While, in the end, it did work well; along the way I got to learn that this stove is not a good ‘charcoal lighter’. You will want to start the coals in one of those can things that give good air flow to the bottom of the charcoal AND lets you apply ‘bottom heat’ via wads of paper and such. I was using ‘charcoal fluid’ and applying a match to the top after waiting ‘not so long’ with the predictable flair of fire up the chimney taking the heat away. Things I do when desperately seeking coffee… Briquettes also fill up the bottom chamber and slow air flow in the bottom air entry. Great for slow cooking when already lit. Not so good for ‘getting started’ and also makes burning sticks above the charcoals a very poor way to attempt to light them. (I really do much better after First Coffee…)

Eventually I raked out some of the briquettes, put in some wood bits and paper, and got a decent fire going, boiled water, and made my coffee. Then, and only then, I could appreciate some of the silly things I’d tried first…

So “on the list” is “make a charcoal lighter can” for 1/2 to 1/4 liter of charcoal briquettes.

As the first photo, this is the last one I took. Coffee in hand, flames long gone. Down the throat when in “charcoal mode” and with stick fire long gone.

G70 Charcoal mode

G70 Charcoal mode

You can see the nice cherry glow, stronger where the lower air intake is located. I have the air shut off through the wood feed and 1/2 blocked through the lower air feed. This is a nice ‘warming’ setting but would not effectively cook or simmer in any wind (which I have again today) without some kind of ‘pot skirt’. With a pot skirt and / or out of the wind, it is likely enough heat to do modest speed grilling and a light simmer. At a future time I’m going to try grilling and test actual pot temperatures over just charcoal. Maybe when it’s not blowing out… and I’ve had more coffee… or lunch time is coming ;-)

Hard to see in the picture, but below the ‘stick coals’ there is a stack of charcoal briquettes somewhat glowing. Finally hot enough, but out of the main air feed for now so will be burned up after the other bits are gone.

Construction Order

These pictures were taken in reverse order as I disassembled the stove from yesterday. At the end is a ‘rebuilt’ picture with the stove reassembled (that took all of about a minute… I spent more time fooling with picking up the camera than I did in assembling the stove)

The As Built G70 Stove

G70 Stove As Built

G70 Stove As Built

Here you can see that I put a small grill on top of it (from a $16 portable grill that I sometimes use). In use, it was a bit better with the grill raised. I found that stacking 2 x 4 inch ‘bathroom tiles’ on each corner of the chimney gave a nice height and was quite stable. ( I happened to have some in the ‘materials’ pile on the patio).

The odd greyish 1/2 brick is a ‘paver’ 1/2 brick I had laying around. ( I use them in making ‘garden squares’). It is presently blocking the wood intake. It is resting on top of a brick that can act as a ‘wood shelf’ or as ‘damper’ where that 1/2 brick is located. After using it a bit, I like just leaving that brick where it is and using a distinct damper brick. But that is because I’m lazy. ;-)

Also note to the lower middle of the right side is the ‘air intake’ port. The brick in front of it is laying flat in ‘wide open’ non-damping position. It can be put on edge or end then slid side to side for fine control of the lower air. So far I’ve just been boiling water, so not benefited from that damper control. I’m going to try ‘simmering beans’ a bit later and well find out how important it is to not ‘burning the beans’. (Anyone who has made thick chili in a thin pot over a camp fire knows that problem… )

You can also see how the bottom segment of the leg of the 7 layer is offset to the left to support the next layer up. That’s that odd brick poking out from the middle right front. The brick directly below it (the G stem) is slid slightly toward the back so as to support the brick above the lower air intake.

The Base

G70 Base Layer

G70 Base Layer

Not much to say about it, really. Just that the direction the bricks lay in is determined by the desire to have bricks overlap in a ‘bond’ pattern in the next layer up. You can see where I swept off the ashes from the prior day burn.

Also note that I’m building on top of a cement concrete 16 inch slab. It has faux brick texture on the other side, so I just turned it ‘flat side up’. It is in turn sitting on top of the flagstone side shelf of my present monster built in brick / cinderblock BBQ Grill. It is unlikely that you really need both layers. On the “someday try it” list is to just leave out this 6 brick base layer entirely and use only the cement concrete tile.

The G Layer

G70 Stove G-Layer

G70 Stove G-Layer

The brick closest to the front, in the lower left of the picture, is the one used for the wood shelf or that can be used as a damper when the wood is not being used. In practice, I found that just leaving it in this position is very convenient. So mostly I’ve used that other small 1/2 brick as damper and just left this one ‘as is’ as a sideways shelf. In the next picture I show it pivoted out as a longer shelf. In practice, longer sticks don’t really need the support and are just held straight by the confines of the wood feed hole bricks.

Note that the right lower brick (the “stem” of the G as opposed to the ’1/2 circle part’) is slide upward just a bit. That is so the next brick up on the 7 layer that makes the roof of the air flow hole can rest on it. While it will work if the brick roof is just cantilevered into free space, I like the added strength of the ‘span’ supported at both ends.

The 7 Layer

G70 Stove 7-Layer

G70 Stove 7-Layer

In this picture I’ve ‘pivoted’ the wood shelf brick (on the G layer) so it pokes forward out of the stove. You can see how the bottom brick of the 7 (most forward and right) is offset to the left just a bit and so sits on top of this brick, holding it in place. In practice, long sticks didn’t need this ‘feature’, so I’ve generally not pivoted that brick out in that way in use.

Having that ‘stem’ of the 7 layer offset a bit to the left also lets the brick of the next layer up, that makes the roof of the wood feed hole and part of the chimney, rest on top of it rather than be cantilevered into free space and unsupported. As bricks are not exactly 2 x 1 in proportions, but are a bit longer ( allowances for expected mortar gaps) it is possible to build this without such offsets, but I’d rather have them Something about heavy pots of boiling sauce and fire…

In the fire pit you can see the ash leftover from the prior day burn. Easy to remove when the stove come apart in 20 seconds or less..

The Chimney Layer

G70 Stove with one Chimney Layer

G70 Stove with one Chimney Layer

Pretty simple, really. Four bricks in a square with a hole in the middle. Notice that the ‘long way’ bricks are in the opposite direction of those below them and those in the next chimney square up. That lets them overlap each other in a ‘bond’ and makes the whole structure more stable.

You can also see that I’ve put the ‘wood shelf’ brick back into the more normal sideways position.

As Rebuilt

Rebuilt Charcoal Mod

Rebuilt Charcoal Mod

You can tell this is the ‘rebuilt’ as now it has a pile of ashes to the right side just outside the lower air intake… Also note that the damper brick on that air intake is in the ’1/2 covered on edge’ position. That is the position it was in for the ‘down the chimney glowing coals’ picture up top.

And, for completion, here is the stove with some sticks being fed into the ‘wood feed’ port.

G70 Stove Stick Feed

G70 Stove Stick Feed

I have a US Quarter sitting on one of the brick for scale. Also note that the ‘wood damper’ 1/2 brick is set aside and the lower air feed damper brick is on end pushed toward the back of the stove out of the way.

After the whole thing cools off, I will likely add a picture with the small tiles holding up the grill 1/2 inch or so. that seemed to work very well, so will likely be the ‘final’ design. Just two small tiles on top of each other at each corner of the chimeny square.

Usage Notes

One feature of building the stove on the big concrete cement paver was that I could turn the whole thing. A decent wind ran down the side of the house that points right at the front of the stove and into the wood feed port. When gusting, this would ‘puff’ some ashes and smoke out the lower air port (that is supposed to be air in, not out…). Having “ram air” into the wood feed port is not desired. Well, though it was a bit heavy, I was able to just turn the whole thing on the slab while it was operating” and fix that. Playing with the 1/2 brick air damper helped a little bit. But clearly this stove is best built with the wood feed port NOT facing the expected wind direction.

Of 12 ounces of water put into the 2 quart pot I was using, about 4 ounces evaporate before I got a good boil going. Using a large shallow thin pot with no lid and no wind screen and no pot skirt in a nice breeze is “sub optimal”. Using a lid would have gotten me and coffee together much faster.

Trying to use an air controlled small burn chamber with air on only one side and cold bricks on three (and below) and that air through a controlled air channel is NOT the ideal way to get charcoal briquettes started. Using old damp ones that have sat out for a few rainy days and had 2 nice sunny days to dry out is also “not ideal”… This stove is not a good ‘charcoal lighter’. Use an external can / chimney for that. Once lit, it has good control of air flow for metering charcoal use and will produce low to medium heats. For high heat it works best with no charcoal pile clogging up the air intake and wood feed into the wood feed port.

I’m going to try making lunch over it, in ‘stick mode’, and testing the stability temperature of a pot of water in ‘charcoal mode’ with two damper settings to see what the performance values are. In “stick mode” you need to keep feeding in the sticks, so leave it and it dies down fast. Probably a feature…

For a family, it is likely too small to cook a lot of food fast. I’m pondering another brick arrangement that would increase the burn chamber size and double the ‘over charcoal’ area. Perhaps with a 1/2 height chimney for better grilling effect. We’ll see if that is needed or desirable. As it stands now, it’s fine for one or two people, as long as you don’t want all three courses hot together… (Grilled meat, fried potatoes, boiled green beans…)

As an ‘emergency stove’ it would be fine.

Build the stove out of the wind, or with the non-air channel sides facing away from dominant wind positions. If the wind shifts, use the damper bricks to prevent ‘ram air’ down the ports…

The bricks stay hot for a while, so if taking it apart after running, remember that the cold end you grabbed to take it apart is next to a hot side that was the chimney or burn chamber in use. I took the chimney down one layer while in operation, carefully picking up bricks by the ‘cold end’. On putting it back together I started to pick one up and discovered the ‘hot edge end’ was still hot. Not enough to burn, but enough to remind… In an emergency situation, using one of these for late dinner and hot beverages would yield many warm bricks for keeping a lean-to / improvised shelter a bit warmer into the night…

So, in summary, it does work as expected. It is ‘right sized’ for one or two folks, more taking turns. The stove can be modulate to simmer / low fairly easily. Start charcoal outside of it. Be ready to feed small sticks fairly steadily. Dry sticks work better, but even the ‘left out in the yard’ during the rain last week sticks I used were “OK”. (They did snap when bent). Use a pot with a lid, and making a pot skirt / windscreen is likely very valuable. Stoves and wind don’t get along all that well together… any stove and any wind.

Next step? After further performance testing / characterization of this one, I’ll be looking at ways to keep the features in this one, but ‘upsize it’ a little. Maybe a taller wood feed port or a larger air feed. More chimney area for more grilling area. Testing the performance as a grill and seeing if it really wants less chimney separation between meet and coals. (It looks like it to me). Working out a pot skirt / wind screen of some kind. Finalizing the tiles under the grill for decent height / air flow.

I’d not toss out my Weber for it, and I’d not give up my Coleman Gas Stove either. For camping, I’ve got a few ultra lite alcohol and ‘tab’ stoves that I’d rather use. For ‘car camping’, even the Sterno Stove beats it and just about anything beats it for portability. Yet the idea that I can take a dozen or two of the bricks I use for walkways and garden square dividers and make a stove ‘post quake’, quickly and easily, with not tools or pre or other materials, and that it will efficiently burn ‘found fuels’ from my yard (as it just did). Well, that’s kind of nice. That I can make a pot of chile and leave it on ‘warm’ perhaps for hours, untended, that’s ‘special’ in an emergency “I have things to do” situation.

For 3rd World folks the more ‘constructed’ stoves are likely better. They can be made a bit bigger, and cleaning out ashes will not happen as often. Larger wood feed ports would also be helpful. Feeding a family would need something bigger than this. Yet, were I cooking with a ’3 stone open fire’, having one of these to let the beans simmer untended or even just keeping a pot of water hot for tea, coffee, whatever. That would be a nice feature. That I could build it in ‘no time’ and be at least a little better off, even if only while building my “Rocket Kitchen”, well, a week or two of “better than before” while on the way to “Much better” is still a good thing.

This video shows making such a “Kitchen”, and in passing a kiln for making the parts. Much better, but much more work too.

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About E.M.Smith

A technical managerial sort interested in things from Stonehenge to computer science. My present "hot buttons' are the mythology of Climate Change and ancient metrology; but things change...
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10 Responses to G70 Stove Pictures and Use Report

  1. E.M.Smith says:

    My comments on charcoal starting need a ‘do over’. I tried lighting a pile of them in a flat BBQ and it took forever. So I went to move the bag… the bottom fell out. It had gotten rain to it sitting at the edge of the patio cover. Bottom layer were charcoal sponges of water, top layer was “not dry”, in between….

    So who knows how well this would like ‘fresh dry charcoal’. That will have to be worked out later.

    Along the way, though, I’ve got the bricks in a fairly nice BBQ shape. Just did a burger over coals on it (now that I got some going…) Pretty good. So a “future posting” will be the 12 brick BBQ. Once the “tuning” is done with decent charcoal…

  2. adolfogiurfa says:

    @E.M.: When some first world NGO´s sponsored, twenty years ago, terrorism in my country, we had to be resourceful as to get a heat source, when black outs were almost every day. In those days one of the things I made was to get a one gallon empty paint can, make it four 1/8″ inches (at 90º each around and at the middle of it) to allow air intake, put half an inch high of alcohol inside, light it up, and put a cooking pot on it. Another way, which I have told it to you before, was to produce an exothermic between aluminum scrap and sodium hydroxide in water, so as to put in the middle a pyrex glass and boil water in it to prepare my coffee. You see?….those same idiots around spoiling our lives…

  3. Roger Sowell says:

    E.M., you might try a rounded brick or two on the G level to increase air flow. The rounded end, or half rounded, would be at the air inlet. This would be the upper-right brick, and the lower-right brick. An alternative would be chipping away a corner from a rectangular brick.

    Another aspect for untended operation, or self-feeding, is to use wood pellets as fuel. A metal can with a suitable hole on the side near the bottom might work. Place the can with the hole lined up with the fuel feed hole in the bricks.

    All the best…

  4. E.M.Smith says:

    @Adolfo:

    I’ve got 3 or 4 alcohol stoves of various designs, a couple of them commercial. It is very easy to make an alcohol stove. (So easy it isn’t much fun ;-) But I’ve never made one gallon sized. Always smaller… Maybe I’ll try a gallon sized one just to see how hot it gets ;-)

    But realistically, if you have alcohol, even just a metal cup or old tunafish can is a stove.

    Part of what makes the wood stoves interesting it that it is easy to burn wood in a very dirty way, but hard to burn it in a very clean and efficient way. Even harder to do that with near zero money. So it is an attractive problem. That it also could benefit folks in a variety of very hard times and places, well, that just makes it all the more satisfying if / when you come up with something.

    At some point I’m going to try a ‘cement (concrete) bucket’ version, just because they are so common and I think I ought to have a skill in making them. But they just seem kind of ‘inelegant’.

    FWIW, the ‘Brick BBQ’ variation I put together today was very effective (once I got the coals to go…). I used the grate off of an old “cheap” tin BBQ. Inspecting the base of it showed that winter had not been kind to it, either. They tend to rust out in a season or three if ‘left out’. The lid is still OK, and the grate is fine… So the reasonable (and at this point certain) result is that I’m going to be making this “brick BBQ” my standard charcoal one. I’ll use the grate and top from the old tin one, but don’t need that ‘rusty base’ any more.

    While I like alcohol stoves much more than most (easy and clean, very effective) the problem is getting cheap alcohol. Methanol is hard to get and toxic (at least, hard to get here in gallon and larger sizes). Ethanol is, well, legislated into painful. Isopropanol starts to be smokey, but is my fuel of choice for erstaz stoves, but doesn’t work well in the commercial camp stoves. Oh Well.

    @Roger Sowell:

    The rounded brick is an interesting idea… have to hit up the ‘decorative brick’ section and look for ideas ;-)

    Don’t know that I’ll try the wood pellets thing. It’s a good idea, but I don’t know of anywhere that sells wood pellets around here. Probably have to leave the bay area for the country somewhere to find them. Certainly outside the Bay Area Air Quality District (who believe nothing ever ought to be burned… but can’t get cars banned… yet…)

    As I have a yard full of self generating wood (sticks and bamboo) I’m more likely to play with them. At least until the “Fireplace Police” come to arrest me ;-)

    (Well, only 1/2 ;-)… I had a visit once… the “password” is “cooking”… If you have a plate of cold hotdogs sitting next to your bonfire, you can say “I’m doing an open BBQ for dinner.”… and that puts you into the “back yard BBQ” exemption from “burning is illegal”… Don’t know if it works for a ‘brick stove’ in the fireplace on ‘no burn in the fireplace’ days… but it would be interesting to try ;-)

    Ah the joys of petty bureaucrats and nosy neighbors…

    Oh Damn… you’ve got me pondering wood pellets… Can, large old style wood bit on very slow motor, chute into fire box… pellets going ‘pingidy dingidy plop’ into the fire box about 10 per minute… Hmmmmm…. (Maybe I can make my own wood pellets out of the yard waste…)

    Probably easier to buy a gunny sack of feed corn…

    I’m pretty sure I’ve seen rounded brick or tile end caps. I could see working some tiles in… I think I’m going to visit Home Depot tile department looking at “rustic clay” tiles…

  5. Judy F. says:

    EM,

    Gosh, I can get a sack of vermiculite in the gardening section at Wal Mart, wood pellets by the pallet and sacks of corn for corn stoves at the local farm hardware store. Next time you are driving east ( as in cross country), let me know and I will take you to some “real” supply stores and you can load up with all kinds of goodies for experimenting with. Then you can stop at a Wal Mart in Utah, where they supply items to families who store large quantities of food and water at home. I was surprised when I was there to see plastic 50 gallon water storage barrels, 25 pound sacks of wheat berries for grinding and other items that I can’t even get here where I live. You could probably find all kinds of survival stuff for your bugout kit. You might not be able to get back over Donner pass on your way home, but oh well, if you got delayed for any reason, you wouldn’t have to eat anyone.

  6. E.M.Smith says:

    @Judy F:

    But but but…. what if I wanted a bit of BBQed “long pig” …
    ;-)

    (My kids went to Reed School… named for one of the survivors of the Donner Party that settled down here and became a local success… It was, er, ‘fun’, explaining to them that their school was named for a cannibal… )

    Yes, Walmart does great job of ‘tuning’ to local needs. Odds are that just driving 100 miles inland I could get a much more ‘rural’ mix. Here everything is tuned to “city slicker”. Drives me nuts as I was raised 220 miles away in real country…

    I have about 100 lbs of wheat berries in the garage along with a good mill. 80 miles inland my sister and her guy have a very nice wood burning home heating system. etc. etc.

    I’m married to a city slicker who can’t survive more than 20 miles from a Macy’s. So I’m sunk.

    Oh Well. I’ll die soon and the conflict will end…

  7. p.g.sharrow says:

    @EMSmith I have one of those city girls. She has tremors and shakes if she can’t see a shopping mall in the distance. ;-) We live in the mountain foothills about a 40 minuet drive from the shopping malls of Chico. Strange thing, If I need to shop for tools or materials at Home Depot there is a great gnashing of teeth! I can’t understand it. It is shopping. 8-) pg

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