bob golding

Cindy Mathieu wrote:

cindy, on your video of assembling the vermiculite riser i noticed the inside seemed to be a different colour to the outside. do you use anything like iITC100 or satanite. on the inside of the riser?

Good eye, Bob

I am not familiar with ITC 100 or satanite.

Yes, the inside has a heat reflective coating which is supposed to increase the temperature of the exhaust and extend the life of the material. It's very expensive and we never did the side by side tests it would take to confirm that it did any good in our application.

i discovered both ITC100 and satanite after having a look at some blade and knife forging sites. it is very expensive, but for small forges it does seem to have a good reputation for extending the life of the refractory. given that it is the same price as replacing the riser using it just to extend the life of the riser may not be worth it. raising the temperature of the burn is another thing though. as i don't possess any test equipment apart from a IR laser thermometer i couldn't really tell if it made a significant different or not. a set of high temperature thermcouples is on the shopping list, but i have to built something worth testing first.

Cindy Mathieu wrote:

Also in consideration, Dragon Heaters cast their rocket cores in a single piece.

Dragon Heaters casts cores in a left and right piece and ties them together with the paper gasket in between using stainless steel banding, as you recommended to Thomas Rubino.

In the image, you can see the stainless steel banding in 2 places on each size (4" 6" & 8"). The heat riser is made from vermiculite board and there is a paper gasket under it as the interface to the burn tunnel. There is also a paper gasket between the feed tube (which has a P-channel in it) and the burn tunnel.

The burn tunnel design is as Peter van den Berg discusses on page 111 of the 3rd edition of Rocket Mass Heaters. We have licensed his design for commercial production in the U.S.[/quote

cindy, on your video of assembling the vermiculite riser i noticed the inside seemed to be a different colour to the outside. do you use anything like iITC100 or satanite. on the inside of the riser? i am planning on making a riser from vermiculite after i finish experimenting on the outside test RMH. seems like together with the cast core it will save quite a bit of weight, not counting the thermal mass of course. the plan is experiment ion the bus before installing it in the yurt with the thermal mass.

hiu matt i am a newby so may be wrong here as i have no personal experience of this,but... you could use a peltier driven fan or even 2 or 3 on top of the drum to stir up the air. plenty of youtube vids on how to make one cheaply. i live in a very damp granite house in cornwall UK so know a bit about cold. we use a desiccant dehumidifier in the winter. it really does make a big difference depending on whether you live in a damp climate or a dry cold one. draws about 300 watts or so.

yes i thought it looked like easy wood to split. looks like sycamore. like to see him chop our monterey pine that fast.

i am cross posting this from the other forum. hope that is ok.
as i want to use the heater in my yurt i like the idea of having the feed outside as done by fishermans Daugher a few years ago. as i want to be able to cook on the top of the drum i don't want it too high. i can bury the burn chamber to some extent but was wondering about the ratios. if i keep the burn tunnel the same CSA as the 6inch riser but use a 8 inch riser would that allow me to have a longer burn tunnel with out increasing the height of the riser too much?

thomas rubino wrote:Hi Bob; when i built my 8" core using matts plan's, I had 2, 50 # bags of fireclay on hand and I didn't have quite enough! I needed 3 bags ! Even on a 6" I would have no less than 2 bags. I'm sure that rockwool will work fine as a binder. Plywood will work as well as hardy board or aquaboard, what ever you use will burn out quickly. Also matt has plans for a cast riser with the same ingredients , You will need a bag of fireclay for this also . Matt used a piece of stove pipe for his sacrificial inner form , I used a piece of (soni tube) cardboard concrete form as my inner form and it worked great! Good luck Tom

thanks thomas, i have ordered one bag for now to make the riser with so i have some idea of quanities. i am going to use cardboard tube and paint it with cement slip as suggested by someone either here or on donkeys site.
should i make the riser wall 4 inches as well? i have some oil drums 11 inches diameter, but i could easily extend them up to 14 inches if needed. i have plenty of those so easioer to do that than find a 14 inch drum the right height.

been messing about with the bricks a bit and seem to have the dimensions about right now. so i want to move on to a cast core like matt walkers one. i am going to be using a 6 inch riser rather than 8 inch as the rmh will be heating a 16foot yurt insulated with celotex. the sq footage is around 1200 so from what i have read 6 inch will be plenty.
his video is for a 8 inch riser so i need to reduce everything by about 40% or so. trying to get an idea of how much fire clay to order. he recons around 92 pounds total weight so if i keep the insulation at 4 inches thick should i assume around 60 pounds or one 25kg bag of fire clay. i have 100 litres of perlite but no fire cement as yet.
would rockwool mixed in with the mix work as well as fibreglass matting? i have both but a lot more rockwool. i know it isnt a precise art but does that sound about right?
its either 25kgs or 50kgs of fire clay.
i got a sheet of aquaboard today similar to hadiebacker board. i am going to try and add a trip wire and the ski slope at the back if i can as well. plus the p channel just to keep right up date. i thought i may try to mould the tripwire into the aquaboard separately cook it in the oven and then fit it on the top of the mould before i finish casting the rest of the mould. not sure if it will work or not.

i am about to start on a similar system for my yurt so another bump. anyone know if the OP is still around? i know the thread is 4 years old but it is is such a good design i am interested in finding out if it is still working.

i think that would counter productive. you want to insulate the riser not make it more thermally conductive.

Mikael Long wrote:Hi Den

I did something like that. While the drum that sits on top of the stack was heating up I put mud/clay on it. Even with it steaming I could get it to stick but it was not easy and talk about water vapor release. At one point it was a tropical rain forest in the small space I was working. It was about 50F outside so not freezing but still cold to be working with wet clay. Starting and keeping a fire in a wet RMH is hard and requires constant attention and may not run if its too cold. Use a torch or heat gun to get it going first. I also did multiple coats on the whole RMH which took about two weeks start to finish I could run it in between to stay warm it just looked well unfinished. I looks nice now minus some small cracks which I will fix next fall or this spring. I probably will redo the whole thing and go for a larger unit. This was my first attempt and I want to pull it apart and make change to get even more from less.

Good luck
Mikael69

https://www.youtube.com/watch?v=I6voGcuedxY

trying to post youtube link not sure if that is right but it is a video of my unit in action.

hi, i am a newby so may / does not know what i am talking about yet, so please forgive me if i have this wrong. from what i have read the outer barrel acts as a cold area for the hot gases to descend into as they leave the riser. this needs the outer barrel to be relatively cool i thought for this process to work properly. covering the barrel with clay will hinder this process somewhat i would have thought.