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

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

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

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

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

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

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

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

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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