Project:RMH,horizontal feed Batchbox model 6",

[radek]

hi dvawolk When i have plastered concrete lid on top of my bench i have used a clay slip first on conrete to create some adhesive layer .I just used brush and painted a thick clay slip on to the concrete and than i cobed it.It did worked.

[dvawolk]

Radek, how thick was your cob and did you add more than one layer after slip? You probably only waited for the slip to slightly firms up or did you dry it all the way?
My first layer did stick to the concrete when it dried but after the second layer added, both came off...

[Donkey]

Cob into the slip while it's still wet. Remember to really shmeer the cob in, rubbing it into the surface of the concrete.
The cob that goes right up against the concrete can be quite sloppy with slip. It sounds like maybe you placed the cob on fairly dry.

[dvawolk]

I can't say that it was too dry. It was rich in sand and when it was piled, I could vibrate it and it will flatten quite nice. There was no clay slip under and probably I should have wetted the concrete even more. The thing is that the first layer staid on the concrete firmly. But when I rewetted it and when I added second layer the bond between concrete and cob wasn't there anymore...

[dvawolk]

HM. I think I haven't posted photos for awhile. Here is the stove. The vertical part lacks a smooth layer over the yute mesh. I should have done it before I started to use it... this will probably be a spring project... anyway, aesthetically it is not finished yet, but functionally it is.


And il gato says it is okay :-)


And some more photos... below is the link to photobucket album...
s1275.photobucket.com/user/dvawolk/slideshow/HORIZONTAL%20FEED/Batchbox%20SEPTEMBER%202013

Today I had a nice burn, good draft over all burning time. There was about 3kg of wood burning, but air inlet was open to the max,70sq cm. first my exexhaust temperature was 46C (15 minutes from start) then I added the rest of 3kg of wood and it started lowering exhaust temp and coincidentally the draft also. Here I opened the inlet to 70sq. Cm and the temperature went to 57C. At the begin of coal phase the max exhaust temperature was achieved : 63C...

Now I make two burnings a day, one in the morning and one in the evening. The surface temperatures in vertical part are from 35 to 65C and for the bench up to 37. I will check lower bench temperature in the morning.

When I start to burn the full batch (6-7kg) the bench will probably be to hot at maximum temperature, which is around 1 to 1.5h after the coal phase. The bench top is 13 to 14cm thick...

[matthewwalker]

It's really beautiful Klemen! Excellent work, I'm sure kitty agrees. My cat thinks I've built her own personal cat heater, and waits there in the morning making sure I light it first thing.

[dvawolk]

Thanks,Mathew.
So this is a new version of rocket stoves, RCH -rocket cat heater. They prefer it because of efficiency :-)

[Donkey]

Oct 9, 2013 23:32:24 GMT -8 dvawolk said:

I can't say that it was too dry. It was rich in sand and when it was piled, I could vibrate it and it will flatten quite nice. There was no clay slip under and probably I should have wetted the concrete even more. The thing is that the first layer staid on the concrete firmly. But when I rewetted it and when I added second layer the bond between concrete and cob wasn't there anymore...

Ahh.. DON'T vibrate it. That will shock it off of the concrete.
Push the stuff on, no slapping, shaking, vibrating, etc.
Also, shmeer the edges of each little bit, make the seams disappear AS YOU WORK. This will slow you down, but it will give a better connection between the parts. Make sure that the concrete is SATURATED with slip.

[dvawolk]

Is clay slip also needed when adding a new layer of cob to an existing dried cob layer?

[dvawolk]

From the last wet work on my rocket heater i started to burn fires twice a day (morning and evening firings). I was writing down exhaust temperatures to see if it is advancing or not. I don't have much experiences with drying of stoves and it is hard to belive that the thing is still loosing humidity although the color of earthen plaster turned lighter a week or so ago... (I didn't say that i don't believe, but it is hard for me to believe...)
I am concerned about exhaust temperatures. Will they reach 100°C or not? After a few days of statistics it looks promising:

Date, ammount of wood, max exhaust temperature

9th Oct, 3.0kg, 43°C
10th Oct, 3.5kg, 63°C
11th Oct, 3.7kg, 74°C
12th Oct, 3.7kg, 78°C

From now on i will stick to 3.7kg of wood for easier comparison.
On 9th of October those 3kg of wood was a margin for the batchbox (not) to stall. When the fire was starting to bite all the wood, the rocket sound started to dissappear, the temperature started to drop and inside of the bench a saw (after the burning)black coloring of smoke... Luckilly the smoke never took the path back into the room... When the problem started to occur i opened the air intake to the maximum (70 sq. cm), this did help slightly, but not enough. After opening the door to make a gap of 1cm things started to get better...

On 10th Oct i am quite sure that the stalling would occur if i would close this 1cm door gap (that is 70sq. cm AND door gap together for air intake). I i closed the door the temperature didn't rise anymore or it even dropped. But after reopening the door it got back up again. I checked the p-channel and it did draw air even with door gap...

Based on those temperatures, it looks that i am getting somewhere (although with door gap)...

One plus is also that after the burn the floor in the bench is dry (wet floor was a problem in my tests under the balcony for a long time). Also at the end of the burn i open the cleaning door in the bench to encourage the drying process...

I am away untill tomorrow, but sunday evening i start a fire with 3,7kg and i hope that it brings me something new...

[dvawolk]

Oh man.. I checked my test temperatures on page 8,bottom post,third test. Do you think that I am experiencing some kind of bottleneck? Provided that now I have better chimney stack and with less than 4kg of wood I fight with stalling?

[Donkey]

Oct 12, 2013 9:04:03 GMT -8 dvawolk said:

Is clay slip also needed when adding a new layer of cob to an existing dried cob layer?

With cob-on-cob, you can just wet it with water.. Slip works better though.
At this point, I put slip on EVERYTHING that's dry before trying to stick cob to it.

[dvawolk]

Oct 13, 2013 20:15:05 GMT -8 Donkey said:

Oct 12, 2013 9:04:03 GMT -8 dvawolk said:

Is clay slip also needed when adding a new layer of cob to an existing dried cob layer?

With cob-on-cob, you can just wet it with water.. Slip works better though.
At this point, I put slip on EVERYTHING that's dry before trying to stick cob to it.

Donkey, so if i understand you, even if the concrete (or other surface) is dry, you don't wet it - you just paint it wit clay slip?

[dvawolk]

This is how the story goes.

There is another info about my chimney stack that i probably should tell. Although it is 11 meters high, there are three stoves connected to it(mine and two others). I am at the ground levels, other two are 4 and 6 meters above the ground.As i said, the chimney is chamotte, 20cm diameter and my system is maid for 15cm diameter. Other two metal stoves are maid for 13cm stack and users are very slow burners (unclean with little air intake).
Usually those stoves weren't burning when mine was. But i suspect that some part of draft is lost due to two additional holes in the chimney that are certainly never airtight. So some part of air is for sure sucked from those two, too. This is first problem and i cant really do anything about it.

Second problem (solved). After cleaning the chimney i found out that at the top there was a thick layer of creosote (from upper two unclean burners). At some parts it was thick even more than 3cm. This was mainly on the top 3 meters of chimney - i was on the roof. The first burn after cleaning (with 3.7kg wood) was an obvious difference. I could have doors closed all the time of burnwith air intake quite large (100 sq.cm) and any evidence of stalling never appeared. This was repeated with similar results.

But i was again skeptical if maybe the ISA was slightly too large to achieve good enough draft, given the more complicated design of a single bell system. So a very simple solution came to my mind.
Through a cleaning hole i added AAC (siporex, ytong...) (as shown in attached image - look for green thing). This was a simple task, i could even add wood because the temperatures here are way below 150°C.

So this barrier works like that all the place on the right is a pool of cold(er) and dead air that can not go anywhere. Thatswhy it works like an insulation and its ISA in not useful for the stove. With this i removed a bit less than 0.3 sq. meters of ISA and now the stove has even more draft.

Today i will try a full batch of wood to see how it is going...


With this kind of barrier one can easily fine-tune the ISA of the bell. But if one wants a larger ISA, more bricks can be put into the bell.

P.S.: i think there is no bottleneck.

[morticcio]

Interesting theory - did you block it off completely or just use the one block as per the image?