Ruben Verhaegen

Hi Thomas,
Thabks again. Another small question. Is it possible to make the clean-out holes and ash-hole entirely from cob or do you a way of making it from entirely recycled materials? Thanks again.

Ok, great. How many inches of cob and rocks would you add on the sides and on top as isolation? Maybe around 6-inch (considering also that we have thick bricks that form the exhaust pipe (around inch thick)) on all sides? Purpose is really heating the room, not cooking. I will put pictures! Ruben

Hi Thomas,

Thanks for the answer. Yes, we were thinking about putting around 8 cm of cob (3-4 inch). The cob is however made with manure instead of straw but i suppose that is fine?

The floor of the building is also made out of cob, do you think this will decrease the capacity of the system to heat?

Thanks

Ruben

Hi guys,

Thanks a lot for the feedback. We built the combustion chamber the last 2 days and it is working fine.

Today we are starting to build the exhaust duct out of the same bricks. Would it be fine to make this 18 by 18 cm if the cross section of the combustion chamber is 17 by 17 (exhaust duct will be around 4m excluding the chimney).

Also, we are thinking to first put a thick layer of cob and make the duct directly on top of it. Would this work well (so no other layer of bricks under it)?

Thanks a lot,

Ruben

Hi all,

I am building a rocket mass heater with feed tunnel, heat riser (normal barrel over it) and exit haust from bricks and we are trying to test the combustion chamber today. In this setup, we built the heat riser of bricks with a big barrel over but without isolation (we will add metal sheet with 5cm of wood ash isolation but should not matter for testing). We tried to light it on a few times but we don't manage to get it going. I have the impression the smoke is going in the right direction when we put the paper but than the flames stay rather outside high on the wood. I included 2 pictures of the setup and 2 pictures from when we light it on.

Does anybody have an idea why it is not working and if we should light it in another way? Maybe it has something to do with the fact that there is a lot of air between the old uneven bricks?

Thanks a lot for the feedback

Ruben

Hi Thomas,

We wanted to test the combustion chamber today (in the we made the feed tunnel and horizontal burn tunnel at 13 to 22.5 cm whereas the heat riser at 18 cm squared) but the bricks are so uneven that I am afraid we cannot build the heat riser all the way up without putting any mortar under it. Also, it seems quite difficult to lite it as in attached set-up (difficult to get the flames going)

Do you think it would be fine if we mortar (1:1 mix of sand and clay) the ground base, feed tunnel, horizontal burn tunnel and first part of the heat riser and start testing in from that  point?

Thanks a lot for your answer.

Ruben

Hi Thomas,

i searched a bit around and there is a guy in the village who can cut  top and bottom from a barrel so that I can use the part in the middle as metal sheet (he will cut a part from the sides if needed to make it smaller). You think this should be fine to keep the wood ash as isolation (I also obtained wood ash meanwhile)?

Thanks

Ruben

Hi Thomas,

Thanks a lot for the very useful feedback.

So for the isolation after the clay brick heat riser, you would use only wood ash without putting any clay? I am not sure if it will stick together in the case of the wire I have, I think it will start falling through the holes without any clay. I can try to find sheet metal but not sure I will find it.

With respect to dimensions, the thing is that the bricks I have are all 26.5*13.5*8.5 centimeters. As it is not so easy to cut these clay bricks in straight shapes, It therefore decided to use 13.5*22.5 as cross section for the feed tube, horizontal burn tunnel and heat riser so that it equals 17.8 square as described in Ianto Evans book for 8 inch tube systems (This is also the reason why, on my pictures, the wholes are more rectangular than square). Does this make sense.

A last thing is that I will also have to build the exhaust system with the same type of bricks as I don t have big steel pipe available. Would it be ok if I also use also 13.5*22.5 cross section for this exhaust system (with bench of around 5 meters long) or is this not appropriate (I will use bricks from surroundings and cob as layers on top of it (around 7-8 on top of the bricks for the exhaust system)).

Thanks a lot again

Ruben

Hi Thomas,

According to what I understand from Rebecca, the design didn't work out for her so what should I do it exactly the same way? In all cases, I was thinking to build the heat riser out of bricks as I have a lot of bricks available in the village (although most bricks or not shaped very straight). I tried to make a first set up of the feed tunnel and the heat riser (first layers) today as you can see on the attached pictures (attachment 1-4) and I also gathered some wire and a 55 inch barrel  (attachment 5-6). So I have a few questions on this if possible:

1) Does this set-up entirely out of bricks make sense? I was thinking to put everything together with mortar in the coming days as the bricks are so unevenly shaped that I cannot build the heat riser without the rest of the structure collapsing. I would therefore also only test it the first time (put the fire) when the basic structure is with mortar

2) Do I understand it well that you suggest to make a mix of 50% wood ash/50% clay, put the wire around it and than poor more wood ash in? In the attachment a picture of the wire I found.

3) Do you think the barrel in attachment is fine as it is or should more paint be taken out? It doesn't allow to take the top off but maybe you know if we could cut the top with a tool and attach it with something?

Thanks for the feedback and I really start building tomorrow

Ruben

Hi all,

Many thanks for the useful information and sorry for the late reply.

@Thomas Rubino:I asked a bit around and should be able to have some wood ash tomorrow (I found on some other forums that this should indeed work better than sawdust)
However, how long should it actually burn before I would know if it is a good insulation or not?

I will post a picture of the first set up today or tomorrow and it would be great to have your feedback on this

Thanks

Ruben