Stove technology,efficiency new materials for a stove!

Its only a 'rule' for those trying to make their own stoves.. 99.9999% of coal burners buy their stove..
A few of us try to make our own the end up buying one anyway,
A few of us have successfully made an improved stove or boiler.


Yes, but your conclusion came at the end of two pages of exchange of ideas and exported knowledge and experience..
the conclusion would not have been accepted or understood if simply stated at the first three posts in the discussion. it's just the
way human's minds work.

So, are you going to try to find a grate to start your project around?

Here is a round grate off ebay from an old round firepot stove:
http://www.ebay.com/itm/220938001650?ss ... 1438.l2649

This type of grate sits on several flat 'tabs' so gravity and the weight of the coal keeps it on the tabs, when you shake the ashes down, you put an
extension handle on the short handle, and move the grate in a circular manner, it won't grind up clinkers or unburnt coal, but will aggitate the coal bed
enough to get the ash to fall out and through the slots into the ashpan below.

Remember the entire underside of the fire MUST be sealed, so you can control the air feeding the fire,, the amount of air to feed 50# of coal is very small.
the sum of several leaks in a bad design or leaking door will be enough to cause a runaway or uncontrolable fire.. you must design it to be able to stop ALL air to the fire, or else the fire is uncontrolable.

So your pipe supplying the ashpan area with fresh air you mentioned in some previous posts must ahve a valve on it to control the combustion.

Good luck,, did you google some stove sites and look at the cut-away drawings ??

Greg L

Guess I'm a bit more "stubborn" when it comes to using things!
Although , anyone should know how a thing that he bought , actually WORKS...
It's like a new and complicated car...
The last time I did that I was "blocked" and desperately looking for the manual
...
Of course you can improve a thing , but experimenting would get you a lot more results!
That's why the "R&D" research and development department exists , right?
Yes, it's been nice thinking how those coals burn after all!
I was drawing, measuring, thinking about that grate and between buying and diy a grate I ended up yet again on the "diy side"!
I don't really understand why some manufactureres use cast iron on their grate; it has a lower melting point , it can crack and I really think a stainless steel grate or a steel one would be better!
I mean , the grate could melt anyway if one "forgets" the draft/air door open and the fuel is anthracite...
Maybe if it would be made out of tungsten or other high temperature alloy
If that grate "sits" on those tabs wouldn't it lose heat on those points?
I took rather "seriously" the "in the air fire pot" for better insulation and higher burning temperature/efficiency!
Of course it will be sealed, air tight!
The air "intake" will be made of steel pipe 2 inches diameter(50 mm) and probably with a valve/tap used to close water in normal conditions!
The steel pipe close to the stove I was thinking of beeing "clean" with no zinc(toxic fumes) or paint on it...
I "googled" some stoves (Hitzer 983)but haven't found too many results...
I'll try a bit more !
I found some firebricks here in Romania with an interesting composition
60% Al2O3 and 30 SiO2 , phoned them and the boss there said these types (round ones, OT7) weren't on stock and I may have to wait some time until they will be available!
The nice thing is that these bricks resist 1450 degrees celsius!
I have read some use even clay or glass wool to insulate a furnace and keep the heat in there and losses low!
You can acces this link to see the round bricks 195 diameter inside and 225 diameter outside!(scroll down to see the dimensions).
I also managed to get some 4 liter of SiO2 of 98,5 purity from another source!
Could come handy sometimes in the future if I want to make my own mortar!
Some perlite would be good but still haven't found a supplier!
I was thinking of using all these methods to insulate the furnace(heat bricks,a mix of heat resistant cement+SiO2 98% purity+some perlite and glass wool on the outside the last layer!
Not mentioned here is the method of supplying coal to this thing...
That's gonna be a even bigger headache...
http://www.sobateracota.ro/Caramida-refractara
P.S. : this guy here made me really curios about furnaces :
http://www.rotblattsculpture.com/Articl ... onzec.html

I've "got it"
This design "seems promising":
http://www.freepatentsonline.com/4290410.html

gowriel wrote:I've "got it"
This design "seems promising":
http://www.freepatentsonline.com/4290410.html

Well known here @ this forum...
COAL CHUBBY

Cast iron is used to make grates because it works, holds up best in the heat and oxygen rich area under the fire.. it's the best material for grates..
There are reasons for each and every design, material, and construction/design practice..

Remember, very smart people have been burning Anthracite for well over a hundred years.. and these people who designed, experimented
and failed and tried again, and again, were from the generations of innovative thinkers, engineers, inventors, entrepaneurs [sp?] that
created the car industry, the industrial revolution etc etc.. NOT a bunch of dummies.. at all.

I've made grates from steel, the are too soft and sag, I've used rebar, and keep coming back to cast iron.. Nothing much survives in the
2200-2500* combustion environment but Cast iron and some special alloys.. regular mild steel will erode away in a week, been there, done that.

Greg L.

Hello LsFarm!
I was just about to answer you this morning but I had to shovel A LOT of snow , take care of a tile stove wich had to be "converted back" to burning wood (the one in the kitchen ), a lot of work and trouble in finding the things needed to finish the darn thing...

on-topic now:
I've "spotted" today a grate made out of cast iron but it was rectangular; I would like a round one or something similar for using with the round furnace refractory large bricks wich I intend to use , assuming your experience and others from here is 100% corect(coal must burn in a round , well insulated refractory "pot fire" and only the heat resulting from this burning to be used/discharged in the air through a heat exchanger and not the direct heat from coals, wich would mean to lower their temperature wich will result in a "bad burn"/incomplete).
I was thinking even of a flat cast iron round plate with lots of holes drilled on a certain pattern!
Considering that in a round refractory pot the coal will burn at a higher temperature and more completely/efficient , the holes would not have to be big (maybe 8 mm each) since the ash will be fine/small!
I can mold/pour some cast iron here in my town at some friends of my uncle(my uncle worked in a cast iron foundry for 18 years and knows a lot about cast iron!

It does not have to be round, it is just that round does not tend to leave ash in the corners as much. Many good stoves have rectangular fire pots.

gowriel wrote:I don't know about boilers...

By "zoned heating" you are refering to multiple small stoves or how?

Water is more efficient at transporting btus than air.

A boiler heats water then thru pipe/ pumps/valves puts the heat where you want it with minimal losses and max efficiency.
Baseboard is an efficient way to get those rooms you want only without having to have three stoves. It will also produce dhw for shower, dishwashing, etc.
With thermostats you can control the heat on each loop/run/zone making it follow you around the house if you want.

Get the book.

8mm holes will not let the ash down into the ashpan.. think of gritty coarse damp sand.. this is roughly what ash is like.. it will resist falling through a hole or slot narrower than 13mm, I'd use 15-16mm slots.

Take a look at the ebay grate I sent you, the slots would rub against the chunks of coal as it grate was rotated back and forth about 2", or 15*.. If you build the grate with too small of holes, you won't get air up or ash down.
you could always take it all apart and mill slots over theholes or drill out the holes to 15mm

Greg L

@franco b : No way anymore for a rectangular fire pot; round and out of refractory brick able to resist 1450 degrees celsius(2642F).
I've made up my mind

@ValterBorges : I'll get the book you mentioned although , right now I have central heating/zoned and what you say could be bought from here ready to install, it's called wood central heating and it's working on the principle of wood gaseification; just a few days ago I was "given the pleasure" to load with wood such thing at another friend's house close to where I live , a Viessmann Vitoligno 80kw.
http://www.centrale-termice.info/centra ... -1184.html
I don't afford this kind of heating right now to be 100% honest with you, although it would be a lot easier to remove the gas central heating unit and put in that spot/region a wood burning central heating unit!
Also, in the schematic of this wood burning unit , the wood burning firepot is out of firebrick; some of you were quite right regarding the need for an insulated "fire zone"!


@LsFarm: I'll either buy the rectangular grate from a shop close to me or build it out of a cast iron flat round sheet with 14-15 mm slots; I have no ideea how big is the coal around here/never bought any and I hope it's not too small in size!
That was my reason for small holes!

Thanks for your responses!

gowriel wrote:
@ValterBorges : I'll get the book you mentioned although , right now I have central heating/zoned and what you say could be bought from here ready to install, it's called wood central heating and it's working on the principle of wood gaseification; just a few days ago I was "given the pleasure" to load with wood such thing at another friend's house close to where I live , a Viessmann Vitoligno 80kw.

Do you have lots of wood? cost? time cut/split?

I was thinking more coal boiler like a leisure line 110k for around 4000 USD.
But for the size home im sure a good stove or base heater will heat up all space with a little circulation help from fans.
Some have even added dhw coils to stoves. Just search this site.

"strangely" enough , but you remind me of a copper coil somewhere in the attic + a radiator forgotten there for about 1.6 years...
They were intended for a solar water heater wich "never made it"
Maybe these would be good for something...
I have about 1 cubic meter of wood different "species" , but I thought I'd give it a try and see how good could that tile stove heat the kitchen;
the answer is it can and A LOT more...
Half of the house has "warmed up" just from a little fire , and the curios thing it STAYS that way...
Now I really start to think the gas company is up to some very dirty things with this gas thing!
And I say this well good knowing that the gas heating unit is working 100% PERFECTLY having it checked last summer!
How can it be that from an "arm of wood"+a tile stove with a cast iron plate , half the house is heated as if the gas central heating unit is working at almost full capacity?!
I'm almost "scared" to think what a small coal "furnace" with a loading capacity of 5-6 kg of coals at one time+ a thin stainless steel sheet large surface heat exchanger could actually do in the long term...
Here's a photo of the tile stove WORKING/burning(the steel plate above it is just as a "precaution" because the cast iron was "kind of" rusted out in some places...
All in all, now I'm SURE the next winter the gas central heating unit will just be similar to a chair in the kitchen...
Coal + maybe wood will be the main heating source in my house!

@LsFarm :
Something is starting to take "shape" but still,the guy to whom I talked about the round refractory bricks 23 cm in diameter capable of taking 1450 degrees Celsius hasn't answered me...
Maybe I'll have to "stress him out" with lots of phone calls ...
Above the refractory bricks seen in this photo I'll put 2 rows of round bricks that will raise the whole thing by 24.6cm!
So nothing near the burning coals will actually be in phisical contact with metal, the firepot will be round and DEEP , the grate will be out of thick cast iron with 15 mm slots in it but the box will still be rectangular!
I was thinking that for a heat exchanger it would work even a long flexible stainless steel tube wich is thin and has a BIG surface area + good heat resistance capabilities, something around 700 degrees celcius!

Check out this video on YouTube:

http://www.youtube.com/watch?v=0rbiPFJY ... ata_player

@ValterBorges:
Nice video , but the surface of those pipes and fins is small in comparison to a , let's say a car radiator or a condenser from a refrigerator!
Also, the location is not that "good" at all...
Since heat goes up "usually" , then the best location for a heat-exchanger or water heater is the top of the stove, be it wood or coal!
I was thinking of this for some time , and the sun was my object of attention(solar water heater), but since in winter you rarely get to see the sun , yes a way of heating water with the coal/wood stove would be ideal!
Not so much in the summer
Even a copper flat coil encased in a copper casing with good thermal insulation placed right above the stove would heat the water in time, and the boiler would keep it that way until you get in the shower!