|
|
Post by ronyon on Oct 7, 2017 6:31:47 GMT -8
I was going to suggest that a long feed would cause the core to draw backwards,up the feed instead of up the riser.
I'm trying to water cool the feed in order to prevent this.
|
|
|
|
Post by Orange on Oct 8, 2017 11:11:00 GMT -8
That could certainly work... Although you would need something like 6 or more inches of perlite to match the 1" ceramic fiber blanket inside a 10" metal stove pipe held by just being slightly over the required circumference in width, that another forum member came up with. I can't remember who... But it was genius. I think perlite and ceramic fiber have similar thermal conductivity but yes, ceramic boards seem the best solution so far although there are also perlite boards... |
|
|
|
Post by ronyon on Oct 9, 2017 4:55:31 GMT -8
I'll be pushing forward with Perlite for now, but looking at the Grainger website, I see I might be able to get ceramic fiber insulation without high shipping costs.
At $15.65 1/2" x 24" x 5 foot roll,and no shipping cost,I think I could afford it.
|
|
|
|
Post by coastalrocketeer on Oct 11, 2017 1:26:25 GMT -8
I think perlite and ceramic fiber have similar thermal conductivity but yes, ceramic boards seem the best solution so far although there are also perlite boards... I think they are around the same at room temperature, but when you get above 1000F they are fairly different... But my memory my be failing me in thinking that I read that somewhere. Perlite will certainly work if you can come up with a good way to stabilize it and keep it in position. |
|
|
|
Post by coastalrocketeer on Oct 13, 2017 11:52:52 GMT -8
My combustion air will actually come from a port in line with the burn tunnel... It may not work, and I may wind up with a standard J and feeding one bundle at a time. But I'll definitely document my experiments and results here when I get going on it.
|
|
|
|
Post by pinhead on Oct 13, 2017 12:59:42 GMT -8
That could certainly work... Although you would need something like 6 or more inches of perlite to match the 1" ceramic fiber blanket inside a 10" metal stove pipe held by just being slightly over the required circumference in width, that another forum member came up with. I can't remember who... But it was genius. I think perlite and ceramic fiber have similar thermal conductivity but yes, ceramic boards seem the best solution so far although there are also perlite boards... No. Peter has mentioned it takes 6 inches of loose perlite to match one inch of ceramic-fiber blanket. |
|
|
|
Post by permaculturebob on Oct 14, 2017 19:00:18 GMT -8
First, I want to thank everyone here for their contributions, and likely my bit of experience has already been replicated many times over, but I will share it nonetheless.
I've been running an RMH for several years now, (I think this is the fifth), the first iteration used a double wall stainless steel 6" section of pipe as the heat riser. (it was getting colder and I had made a vow not to bring back the wood stove for another season) My mass was a mud bench about a foot high and 8-10 feet long, the pipe curved back and the loop ended right behind the barrel of the rocket stove going up a few feet and then out horizontal. (I totally abandoned the idea of a stack for draft and have used the push of the rocket as the primary exhaust force.)
In a month or two we hit a warm patch in the middle of winter, I knew the stainless would likely fail, and was surprised to open up the guts of the stove and find the riser perfectly in tact. But as I was ready to make a perlite clay cast riser, out it came, and when I set it on the floor there was a second clunk as the inner sleeve fell in pieces from the riser. (the insulation however was still mostly intact.)
being on the cheap I did not have hardly any refractory cement (maybe none) so the 6" clay perlite riser lasted the rest of the season and looking at it afterward (I was ready to upgrade to an 8")it was in pretty good shape. Even though the riser got bumped a bit taking it out, it remained mostly in tact even without refractory cement in the mix.
I cast a new riser over the summer and have been using the 8" riser for about three years now, and am ready to upgrade to a batch box rocket hybrid, The 8" riser had some refractory cement in the mold with the clay and perlite (but still not a super amount). I used a piece of light stovepipe for the inside and outside of the mold, the outside pipe I was able to remove after a few test firings that solidified the riser, the inside pipe fell out in pieces over time as it burned away--fortunately I could reach through the firebox into the space beneath the riser to retrieve the pieces, and yes a couple burns went wonky about the time the pieces were falling out.
Without good temp readings my thread is not perfect proof of the perlite, but I never observed any melting of the perlite. I will likely be dismantling things again to build a batch box, and may have more observations on this core that has been in service for a longer time.
I also have some plumbing adventures with hot water on this RMH that I will share another time, but since this thread seemed more about castings and materials I decided to save the hot water adventures for a more appropriate thread. Anyway, that's my story and I'm stuck with it.
|
|
|
|
Post by coastalrocketeer on Oct 18, 2017 14:36:19 GMT -8
I was going to suggest that a long feed would cause the core to draw backwards,up the feed instead of up the riser. I'm trying to water cool the feed in order to prevent this. My hope is that capping the feed tube will keep that from happening, (with the obvious risk of a flashover when the feed tube is opened while hot, so will have to experiment before "setting anything in stone", as it were... |
|
|
|
Post by pinhead on Oct 19, 2017 4:22:49 GMT -8
I was going to suggest that a long feed would cause the core to draw backwards,up the feed instead of up the riser. I'm trying to water cool the feed in order to prevent this. My hope is that capping the feed tube will keep that from happening, (with the obvious risk of a flashover when the feed tube is opened while hot, so will have to experiment before "setting anything in stone", as it were... I can assure you, it won't work. |
|
|
|
Post by horseshoehank on Nov 14, 2017 18:47:15 GMT -8
My core and riser both melted the perlite out of it. It was a dragon heater clone. I burned both sticks and pellets, with enough heat generated to make the barrel top glow red through the high temp paint. The biggest problem was the coals at the bottom of the feed generating so much hear that the roof of the burn chamber melted, even with the secondary air gap and tripwire.
|
|
|
|
Post by Orange on Nov 16, 2017 2:07:28 GMT -8
melted or collapsed? any pics?
|
|
Deleted
Deleted Member
Posts: 0
|
Post by Deleted on Nov 16, 2017 7:14:10 GMT -8
|
|
|
|
Post by mendobob on Nov 27, 2017 11:41:31 GMT -8
We are building a 6 inch rmh using Erica and Ernie's plans. We are using 1/2 firebricks for the heat riser, and are proposing using a 15 inch barrel packed with perlite to insulate the heat riser. That would give us 3 1/2 inch clearance inside the 55 gallon drum. Is that sufficient for good air flow? What would be the ideal diameter for the heat riser plus insulation inside a 22 inch 55 gal. drum? Thanks.
|
|
|
|
Post by Orange on Nov 27, 2017 13:42:43 GMT -8
calculate the cross section area of a riser and that would have to be the minimum surface throughout the whole system. You can post it in a separate thread.
|
|
|
|
Post by smokeout on Dec 11, 2017 13:40:57 GMT -8
I was going to suggest that a long feed would cause the core to draw backwards,up the feed instead of up the riser. I'm trying to water cool the feed in order to prevent this. My hope is that capping the feed tube will keep that from happening, (with the obvious risk of a flashover when the feed tube is opened while hot, so will have to experiment before "setting anything in stone", as it were... I built my rocket stove on this principle. I burn 3/4"X11"x 4' strips. It's scrap bundles from a pallet mill. Five $ for a 2500 lb bundle. Once my fire is going, I cap the top and open a vent at the bottom. My vertical pipe does get hot at the bottom ( not extreme) and I have some creosote buildup inside the pipe. I get around one hour of burn time with a five inch feed tube. |
|
