Horizontal Feed Experiments cont.

[matthewwalker]

Just thought I'd share some stuff I've been experimenting with, and figured we needed a new thread on this to keep Peter's from getting any more off track.

As you guys know I built a bunch of horizontal feeds this summer using various methods. I'm still really happy with the latest model of half barrel burn chambers. The latest version of which I removed one side window and used clay/perlite to shape the firebox into a box/nozzle shape similar to Peter's batch burner. The exception is I put the nozzle "slot" against the remaining side window to keep it clean, something I learned during my summer experiments. That stove works amazingly well.

Since Peter's great thread I've now cast a couple burn chambers following his design using a homemade refractory mix. 3 parts Portland, 4 parts sand, 4 parts fireclay, and about 12 parts perlite.

The first one I made was a 6" system, and built to Peter's dimensions for the most part. No door, no P channel. It runs well, but needs a bit of babying to not smoke back out the wide open end. Closing the feed about halfway off with a piece of steel stops pretty much all smoke back when the stove is hot, unless I over feed it. It makes a ton of heat, and is currently running into a three half-barrel mass. The barrels are mostly cobbed and the stove runs great, and really puts a lot of heat into the mass. Pretty encouraging.

The second firebox is an 8" system, and is slightly taller than Peter's, and a bit longer. I found a masonry stove door with air control that fits the profile quite nicely, and installed that on it last night. No P channel, 'cause I'm trying to keep it really simple and with no wearing parts.

I ran that one for hours yesterday with a straight stack on it, and one of those "heat reclaimer" thingys inline on the stack heating my shop. Dang, this thing is a beast. I was able to burn all the big knotty things that wouldn't go inside my house stove. When it's up and running looking through the window in there is amazingly violent. Similar to the video Peter posted of the fellow with the cooktop. I'm pretty encouraged, this is good stuff. The straight stack allowed me to see pretty clearly the smoke or lack there of from changing the air inlet size and configuration, using the draft control and or opening the door. Once it was hot it could burn pretty cleanly with a surprisingly small amount of air, and burned for a couple hours at one go without reloading. Good stuff, I'll try to get some photos for you guys soon.

[grizbach]

Good job Matt. I am interested in the shape of your burn chamber. I like that you can get a couple hours burn out of a batch. I suppose the heat isn't as crazy as if it were to all burn up at once!

How durable would you say is your refractory? The mix that went into my build is insulating and it is isolated from wood abrasion.

[matthewwalker]

Thanks Griz. The burn chamber looks pretty much exactly like Peter's. Roughly 14"h x 8"w x 18"d, with the bottom corners 45'ed to a 2" wide flat on the bottom. The refractory seems pretty tough. I have a bit of a different philosophy on the castings, as I have been burning my straight fireclay/perlite mix in my house stove for a year now, almost. I'm of the mind that it's okay for it to crack, as long as it doesn't go anywhere. I plan to use these castings essentially as a "liner" for a monolithic cob stove, so they don't need to be structurally sound, just strong enough to get into place and then stay generally together. It makes it a lot easier since I believe anything with this shape and going through the cycles they do is going to either crack or need expansion joints. Pretty easy to cover the whole thing in cob and not have to worry about it's integrity. As long as it doesn't just crumble away, I'm happy with it. All that aside, it's too early to tell about this mix, but it does seem like it will be pretty resistant to abrasion from the wood. It feels pretty hard. Much, much harder than my all clay castings.

And yep, I think insulating is the number one factor. I've built a few heavy brick stoves now and man, the difference between insulated and uninsulated is amazing. I'd rather patch up a good stove every year than have a crappy one last forever. Just my opinion, but the more I experiment, the more I believe this to be the number one factor in performance. Whenever I read of folks having trouble with smoke back, the first thing I think after manifold opening size is that they must have an uninsulated feed, probably heavy brick.

[peterberg]

Nov 29, 2012 13:55:57 GMT -8 matthewwalker said:

No P channel, 'cause I'm trying to keep it really simple and with no wearing parts.

It's a pity, I've written a lot about this channel thingy and the positive effect is very much proved by now. Besides, because of the air cooled nature of this p-channel it won't burn out, at all.

As you've find out, when the stove is up to maximum working temperature it's able to function properly with very little excess air. With the addition of the p-channel the same can be done when started from cold. ;D

[matthewwalker]

Thanks Peter, I'm not saying they won't have one. I am absolutely convinced of their effectiveness through your postings. I thought I would start dead simple and get a baseline. It will be very easy to drill an entrance for a P channel for the next phase. I have a question regarding that.

In one of the postings I believe it was stated that the P channel should be roughly 5% of system CSA. I believe a 1" pipe should be roughly 5% CSA of an 8" system. Do you think that the shape would be acceptable? Again, trying to keep from having to fabricate another part if possible.

[peterberg]

Nov 30, 2012 9:55:34 GMT -8 matthewwalker said:

In one of the postings I believe it was stated that the P channel should be roughly 5% of system CSA. I believe a 1" pipe should be roughly 5% CSA of an 8" system. Do you think that the shape would be acceptable? Again, trying to keep from having to fabricate another part if possible.

When you mean a round pipe, I can't give you a proper answer. All the channels I've used where also the same width as the port. So, a round channel isn't tested at all. It's quite possible to make a flat one from a square duct of the correct size. The channel itself will be like a U-shape this way.
Hope this is clear.

[matthewwalker]

It is clear, thank you for the answer. I do have a small welder and fabrication tools so I will most likely end up following your lead. I may try a round pipe on one of the stoves as an experiment, but without proper testing equipment I'm probably better off staying within your tested parameters. Thank you again.

[grizbach]

Hey Matt, correct me if i'm wrong.
8"system is 50sq".
5% would be 2.5"

1" pipe is .78sq"
You could place three 1" ports into the burn tunnel to get 2.35 sq".

[matthewwalker]

Yeah, I think you are right Griz. I was kinda struggling with the math there and since I posted I looked it up again. I can do the basic CSA calc. but throw in a fraction like .5 for r and I get all confused! Lol. Anyway, if I do it I think I'll start with a 1 1/2" pipe which should get me 1.76" CSA. Three 1" pipes would take a lot of the structure out of the casting. I suspect I'll probably dig around for some channel or square stock and just do it right as Peter suggests.

[Donkey]

If you DO plan to try round pipe (or if you use square), remember that the side facing the heat riser (downstream) should be cut up a little higher than the side facing the fire (upstream).
It's an easy detail to overlook and it's important for the P-channel to work properly.

[jpalombo50]

I'm working on a horizontal feed as well. Is there anyway you could post any pictures of your design? What are the dimensions of the combustion chamber, 7x7ish?

[Donkey]

Dec 14, 2012 15:44:11 GMT -8 jpalombo50 said:

I'm working on a horizontal feed as well. Is there anyway you could post any pictures of your design? What are the dimensions of the combustion chamber, 7x7ish?

Dood.. it's ALL OVER the "Adventures with horizontal feed" thread.
Gotta read all the way through it, man.. Good info!