Watched a few vids built a heater

Hiya guys

As the subject states, came across this concept ont tinterweb watched a few vids and thought I had all the materials needed on my plot to build one of these. My cob is a little unorthadox consisting of sand cement and manure and is taking an age to dry out but is heading in the right direction. The burn chamber and heat riser is in the J formation and made from storage heater bricks. Which brings me to the first question which is, do I still need to put a layer of insulation around the heat riser will it make that much difference? The first problem that I solved thanks to this forum was to stick a vertical flue on the end of it as was getting some smoke back issues all solved now. The issue I have at the moment is that unfortunately as I am doing this on the cheap aka free, the only exhaust pipe I have is twin walled so no latent heat to warm the seating so have not bothered to make any yet, which leads me to my next question where can I source cheap pipe? in the US pipe seems infinatly cheaper than here UK so if any of you guys coud point me in the right direction that would be great.

Thanks Steve

Steve, for cheap pipe, check the half barrel system.

( mathewwalker, at donkey's site)

Yes you need insulation, at least for the burn tuinel and heat riser.

Thanks for that pointer Antone pretty good idea.

All in all I am very happy with my RMH, it always pulls well and frequently is white hot in the burn chamber making that lovely wooshing noise. Considering I do not have any insulation and only a 4 1/2 in exhaust pipe its doing really well. I cannot get my hands on anything suitable to insulate the Hr with so thought I could possibly wrap with tin foil then render with vermiculite and cement in thin layers and build it up to about an inch thick. Will the CV mix stick to the tin foil?. Todays R M H question answered wa,s can I fill the feed tube with sawdust at the end of the day and let it burn itself out? answer no I filled it thinking to myself there is plenty of oxygen in there and air can pass through it and all went well for about a minute and then some sciencey maths air pressure thing happened and it got sucked in and then spat out like a mini volcano! I was showered with sawdust and sparks. Lesson learnt. :

Steve Allotment : I hope I am misreading what you are trying to do with cement and vermiculite, You can not use a portland type cement as the lime in portland
type cement will not survive contact will the high temperature found in a Rocket Mass heater, also if you use a non portland type cement (Pricey) or just common
clay to make a mix, by the time you get enough of ether to mix with vermiculite to make a rigid structure with enough strength there is very little insulation left
to the vermiculite. Most of your fellow members use a clay slip and perlite mixture !

I am not a great fan of U-Tube and the 'Flaming units of Death' found there, but if you go to you-tube and then type in Sawdust heater you will find several
examples of working sawdust heaters most of which can be said to have an internal chimney of Packed Sawdust much like a heat riser. For the Good of the
Craft! BIG AL

Thanks Al No you are not misreading although I was not planning on using normal cement. We dont have much clay around here very sandy soil. Perlite over vermiculite fair do,s. I have just looked on ebay and found 25kg bags of fire clay for reasonable money not sure how much coverage a bag would give me though. I have seen the sawdust heaters great if you are outdoors not so good in my shed though. Had some success with the sawdust today though, I used a sawn off broom handle to ram it into kitchen towel cardboard tubes and put those in the RMH decent result. I have sacks of the stuff from cutting logs You would think it was gold the way I swept it up and saved it. Too good to throw away.

Steve : The same rules on both sides of the pond, Excavation contractors will know the soil types for 50 miles around, where they have found clay, and how deep
it is, and they have to pay to haul it away and to dump it, also the road crews know where they have to check after heavy rains, the hill side cut thru by a road
that slides down and blocks the road or plugs a culvert under a road !

Really nasty weather finds them at the shop, doing repairs and maintenance, so give them a gallon nasty days to catch them home ! Then you can mix in some
good bagged clay with local clay and have the poor stuff go up to 5 Xs as far ! Good luck hope this helps and is timely ! For the craft ! Big AL !