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Post by pinhead on Aug 2, 2017 5:21:14 GMT -8
The barrel temp is meaningless without knowing what the ambient air temperature and wind conditions are.
If it's 100°F and sunny out it's not that impressive but if it's 40°F and windy, that's another story.
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Post by briank on Aug 2, 2017 13:45:45 GMT -8
The barrel temp is meaningless without knowing what the ambient air temperature and wind conditions are. If it's 100°F and sunny out it's not that impressive but if it's 40°F and windy, that's another story. Initial tests were 40-50 degrees this past April, cloudy, little wind. Barrel top temps got to 740, pizza oven temps 500. Recent tests were sunny weather, moderately windy, mid 80s, barrel top temp 775, pizza oven temp 615. I don't know how much of a difference weather made. I burned kiln dried hard wood cutoffs from a furniture shop for the initial tests, and compressed sawdust firewood bricks for these later tests with a short horizontal riser before turning upwards into a vertical riser, somewhat similar to the Walker riserless design.. |
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Post by drooster on Aug 3, 2017 9:46:29 GMT -8
I think that is a great design,
now put it into a big teepee and collect serious money off the hippies.
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Post by ringoism on Aug 3, 2017 10:01:58 GMT -8
Excellent. I think I need to work on something like this eventually... The long burn times are really impressive compared to my "J"'s, and the thing is still something like portable.
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Post by briank on Aug 3, 2017 15:39:58 GMT -8
Excellent. I think I need to work on something like this eventually... The long burn times are really impressive compared to my "J"'s, and the thing is still something like portable. Its definitely portable. I wheel it in and out of my garage each time I burn it. I'm still boggled by the long burn times with the compressed sawdust logs. I'm going to compare those times to regular hardwood firewood in the near future. I did burn 1/2" x 3" pine boards and packed the firebox, leaving air channels between the stacks. It didn't get near as hot (620 barrel top within 20 minutes of lighting fire, pizza oven 450 an hour after lighting fire) or burn near as long. Barrel top was down to 340 at two hours and then it rained :-( But there was still fire in the firebox at 3 hours after lighting (last photo.) Apologies, I don't know why these are rotating because they were originally right side up. Not sure how to fix.    |
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Post by briank on Aug 3, 2017 21:57:17 GMT -8
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Post by briank on Aug 5, 2017 18:21:47 GMT -8
I rearranged the fire path again and once again using 12 blocks of compressed sawdust logs the barrel top got 90 • F hotter, up to 865• from 774• (even though outside temps have fallen to 65• this evening, and prior tests days were hot and sunny in the mid 80s.)
You can see the strength of the natural draft here through the small mica glass viewport in the side of the firebox. The flames are moving/drawing so fast they're horizontal.
Edit to add:
At two and a half hours since ignition, barrel top temp is 400• and the firebox is still just less than half full.
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Post by Vortex on Aug 6, 2017 4:37:34 GMT -8
Nice project Brian.
I knew a man 20 years ago who built a machine to make sawdust briquettes. He used a hydraulic ram to compress them in a tube, but it kept exploding due to compression ignition (dieseling).
They vary a lot depending on the type of wood used to make them, some of them have clay powder added to them to make them hold together better, plus because they're heavily compressed their density would be closer to hard wood - both of which would make them burn slower.
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Post by briank on Aug 6, 2017 9:30:22 GMT -8
Nice project Brian. I knew a man 20 years ago who built a machine to make sawdust briquettes. He used a hydraulic ram to compress them in a tube, but it kept exploding due to compression ignition (dieseling). They vary a lot depending on the type of wood used to make them, some of them have clay powder added to them to make them hold together better, plus because they're heavily compressed their density would be closer to hard wood - both of which would make them burn slower. Thanks. I knew there were varying qualities of these fire bricks. In the mainstream wood stove field they are avoided as a sole fuel source because their use voids the warranties of several stove manufacturers. They often swell considerably while burning, bending secondary air tubes and ceramic baffles, and produce intense heat, warping metal components in the firebox of conventional stoves. For people burning firewood that's not well seasoned (moisture content >20%) they add in these bricks to bring down the total moisture content of a load. With an all ceramic core, temp spikes are not an issue, and so far swelling while burning has not caused any problems with these thicker ceramic fiber board layers. From an environmental standpoint, their use makes sense - it's already a carbon neutral fuel source, and we're adding the recycled aspect to that too. Plus it seems to prolong the burn. Win-win. |
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Post by briank on Aug 9, 2017 18:41:46 GMT -8
I finally had a chance to run a batch of hardwood firewood today, a combination of 6 pieces of ash, oak and cherry. The wood was well seasoned but unfortunately uncovered and with recent rains it didn't perform much better, hotter or longer than the (very dry) pine boards, with approximately the same barrel top temps and duration of burn, three hours and 560• on top after a half hour.
The compressed sawdust bricks still hold the record with almost 6 hours burn times and 865• barrel top temps. Wood stove users don't necessarily relate extended burn times with the compressed fire bricks but they sure seem optimal in this rocket stove application and they are the only way I can accurately compare changes in firebox and riser geometry and primary and secondary air adjustments.
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Post by drooster on Aug 10, 2017 10:33:47 GMT -8
It sounds like a very good method to use the same very dry blocks of consistent composition for testing purposes.
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Post by Orange on Oct 6, 2017 8:03:53 GMT -8
At five hours, open door pizza oven temp is 260• and barrel top temp is 256•. woah I thought the temps are in C. Maybe it needs more secondary air or the air isn't warm like in the metal P-channel. I guess oven is isolated from smoke because ceramic boards probably have some binder chemicals. Stove looks cool, especially round heat riser look edible  |
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Post by briank on Oct 6, 2017 9:13:54 GMT -8
At five hours, open door pizza oven temp is 260• and barrel top temp is 256•. woah I thought the temps are in C. Maybe it needs more secondary air or the air isn't warm like in the metal P-channel. I guess oven is isolated from smoke because ceramic boards probably have some binder chemicals. Stove looks cool, especially round heat riser look edible I’m not aware of any previous rocket heater barrels holding temps that long. They usually burn 1 to 1 1/2 hours then go cold. This had fire in the firebox for almost 6 hours using compressed sawdust fire bricks. My Second prototype was far better sealed up and the primary air was increased, and the load of bricks burned 4 1/2 hours. I’m not aware of any batch box burn times like that, but this type of compressed saw dust fuel may prolong the burn of any batch box. I don’t know. |
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Post by Orange on Oct 8, 2017 11:17:28 GMT -8
I'm sure you've built it correctly but I remember that rockets can reach around 1000C on top of riser so if you put a barrel on top the temperature can be slightly lower.
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Post by briank on Oct 8, 2017 19:41:01 GMT -8
I'm sure you've built it correctly but I remember that rockets can reach around 1000C on top of riser so if you put a barrel on top the temperature can be slightly lower. In the mainstream wood stove community it’s pretty much accepted that internal temps are twice temps found on the surface of stoves or single wall stove pipe, so I think these are reasonable numbers for a rocket stove where the top of the riser is 10-12” from the inside of the top of the barrel. |
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