Glenn Herbert

Rocket Scientist
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since Mar 04, 2013
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Early education and work in architecture has given way to a diverse array of pottery, goldsmithing, and recently developing the family property as a venue for the New York Faerie Festival, while maintaining its natural beauty and function as private homestead.
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Upstate NY, zone 5
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Recent posts by Glenn Herbert

I expect that would work, though you would need to break up or dissolve the pellets.Chunks of organic matter would make weak points in the cob instead of adding reinforcing fiber.
1 day ago
For your feed tube, I think you would get the most life by making at least the top 10cm or so of brick or metal, as that will have more wear than anywhere else. As for cooling the feed top, I made a liner of 1/8" steel for the upper 6" which contains the secondary air supply to the P-channel; it certainly preheats that air, but does not at all stop the fire from creeping up the logs. If your draft is strong enough to keep that from happening, I think the air would be moving so fast that you would have a ton of excess air which will only cool the system. I cover my feed at least 3/4 all the time I am burning and still get plenty of air for full combustion.

The feed interior will get to several hundred degrees at least, far above boiling, and I would expect any coil near there to be flashing to steam.
6 days ago
A few comments...
You show a mockup of cardboard tubes for formwork. The original experimenters found that a square cross section was better than a round one because it gave more scope for beneficial turbulence to form. Peter van den Berg in particular made many versions of mixing enhancers, and found the best one was the P-channel with trip wire in the ceiling (which you can find detailed specs for in many places.) If you want something that will be sure to work, I would suggest going back to that formula rather than experimenting with air feeds in various places... especially as you will not be making multiple feed versions to test them against each other, but one version which may or may not be optimum.

I think 48" is not an absolute maximum, but is probably long enough for full combustion to occur with good draft. A 30cm feed tube is pretty short, as you would be safest making the feed able to fit the fuel completely inside so as to be able to cover it airtight quickly in an emergency. If you have 30cm fuel readily available, fine, if not I would make the feed tall enough to hold the fuel you will have. I have found with my well-drafting system that 1:1.5:3 works fine, specifically 16" tall feed, 24" burn tunnel floor, and 48" riser (which due to installation clearances ended up more like 42", and still the flames seldom reach the top of the riser.)

Slanting the feed tube will not be beneficial; it will only give the fuel a wall it has to slide against with the chance of hanging up on any irregularity.
1 week ago
Unless your scrap wood is all straight and smooth, fuel can easily hang up on the edge of a slanted feed tube. So lumber yes, sticks no. A J-tube has less of an issue with this.

To get good combustion with less smoke (desirable regardless of efficiency concerns), you want the flame path long enough that big flames don't reach the top of the riser. A J-tube has a horizontal burn tunnel which increases the flame path for a given riser top height over a K-style. It also has more sharp changes in direction which increase beneficial turbulence.

For J-tube dimensions, I like a 1:1.5:3 ratio measured along the outside edge for feed tube, burn tunnel and riser. You could probably make the feed a bit taller and burn tunnel a bit shorter for cookstove use.

As a long steady burning unit, I like the L-tube style. It can accommodate long fuel completely within the burn tunnel so no danger of it hanging up or falling out, and no smokeback risk. I have used about 30" length and rise.

I would not make the air inlet, if that is somehow separate from wood feed, smaller than the combustion zone to try to get a jet of air. You probably want air restricted some at the entry so there is not a huge amount of excess air which will just cool the fire.

3 weeks ago
Gorgeous copper basin. It looks in fine shape; if there are leaks, they will just need to be soldered. A small leak can be closed with solder alone, while a larger one may need a copper patch soldered over the crack. Any plumber who works with copper piping can do this. Ideally you would use lead-free solder, as is required in the US at least for drinking water piping.
1 month ago
An earthfast post structure, unless there is significant diagonal bracing above grade, would be more stable if dug in three feet. Two feet is iffy. Frost heave could make the structure heave unevenly, but insufficient depth will let it tilt and eventually fall over. If the structure is heated, and there is any kind of insulation in the ground outside the walls, you will have much less danger of frost damage (as well as a more comfortable floor.)

The outer surface of locust will rot if not debarked, but the bark will fall off in a few years in any case if exposed to weather. Inside, the bark will harbor insects and slowly crumble and make a mess, and hinder a good connection between posts and wall infill. I would debark everything. When freshly cut, locust is pretty easy to debark, not so much when it has seasoned a bit.
The lumber value of a tree like black walnut depends entirely on the shape and size of straighter sections of the trunk or limbs. Long straight sections without major knots could be very valuable, while very knotty or complex ones like the photo above would be valuable only as specialty slabs for table makers or the like. Roughsawn walnut in upstate NY currently goes for somewhere around $4 a board foot, but the tree owner would get only a fraction of that.

Look on craigslist or FB Marketplace for someone offering lumber similar to what you would get from your tree, and contact them to see if they are interested.
1 month ago
I would think a round plate about the same size as the riser mounted an inch or so below your cooking surface would spread the flames so they hit nearer the outer edges. It would likely take some experimentation to find the best diffuser diameter and distance below cooking plate. A square plate will always be cooler at the corners absent a complex flame director; a round plate of the right size will be easier to heat evenly.

It might help to have a fin pointing downward around the edges of the cookplate, to gather heat under the whole surface. This might or might not be best attached solidly, or with a small gap between fin and plate.
1 month ago
Can you give any more details about your RMH? They are normally supposed to burn as hot as possible whenever they run, and the mass should absorb nearly all of that heat so that the exhaust is around 100-150 F. Much hotter than that is wasting heat unless the draft is so poor that an extreme temperature differential is needed to make it draw.

Where exactly is this 500 degree measurement happening?

Also, what is your riser made of that you are concerned about damaging it with heat? The whole core interior should be made of refractory material that is not affected by heat.
1 month ago