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AGA stove rocket conversion

                        


Joined: Jul 24, 2011
Posts: 13
hi.. we have an AGA stove.. the AGA's are a heat storage range cooker.
have been looking at ways to convert it to fire on a rocket conversion.. any ideas??


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Len Ovens
pollinator

Joined: Aug 26, 2010
Posts: 1306
Location: Vancouver Island
    
  16
ptrfid wrote:
hi.. we have an AGA stove.. the AGA's are a heat storage range cooker.
have been looking at ways to convert it to fire on a rocket conversion.. any ideas??


Need to know more about how it works.... I would suggest one would only be able to do one hob (burner?) though.. at the top of the barrel. Put  a two inch insulating ring around a thin can (say 4inchs thick/high) filled with tin and add an insulating cover like the AGA. I am not sure how fast the bottom would loose heat after the fire went out though. And as it is a sealed unit. Does the AGA have insulation under the hob?
                        


Joined: Jul 24, 2011
Posts: 13
hello.. thank you for the reply.. the AGA firebox is on the left hand side, is fed from the top (coal coke) the combustion is at the bottom and gases exit around the firebox cylinder and across to right hand burner then up the flue.. (hot plate and simmer plate, both would be heated as per normal) the firebox is two concentric cylinders not unlike the rocket mass heater.. will try to find diagram to post.. regards peter
                        


Joined: Jul 24, 2011
Posts: 13
Regarding how long it stays hot when fire goes out.. 3 days before you can start to work on it and still it is quite warm..
Len Ovens
pollinator

Joined: Aug 26, 2010
Posts: 1306
Location: Vancouver Island
    
  16
ptrfid wrote:
Regarding how long it stays hot when fire goes out.. 3 days before you can start to work on it and still it is quite warm..


Sounds like a good deal. Are you sure you want to mess with it? I think I get the picture. There is (as with most wood cookers) a very small gap between the hobs and whatever is underneath. I suspect that rather than a cast iron plate the the hob surround insulates. I think the part below the hob (on the bottom of the flue gas path) will have a similar shape to the insulator lid (dished) and there may be more mass under before an insulating layer. It will have been designed as a whole unit just for cooking and will probably do a better job as is than anything you can put together on top of a RMH. I would expect that the amount of wood used is not that much and that it heats the kitchen less than most wood burners. Great in the summer.

That said, I do think something could be done with the RMH that would hold cooking temp heat for a number of hours (not 3 days though). I would think it would best to design the cooktop to stay warm as long as the heating mass does. It would only be used in the winter and therefore would be no use in the summer for cooking.
Len Ovens
pollinator

Joined: Aug 26, 2010
Posts: 1306
Location: Vancouver Island
    
  16
Hmm, I was mistaken. I thought it was a wood burner, but when I went to the AGA webpage I found that is the only thing it doesn't burn. I would guess from the gas stove beside yours that it is a gas version you have? (not oil or electric) You want to convert what you have to wood burning, but want it to be clean burning like a RMH? There was at one time a "solid fuel" AGA so finding the burner part for an older solid fuel model would work... It would take tinkering.

The wiki:

http://en.wikipedia.org/wiki/AGA_cooker

Says they use a lot of fuel.... I guess because it takes so long to get the heat core to temp, they are designed to burn all the time. This would be a problem in the RMH world where the heater is designed for short burn work.
Irene Kightley
pollinator

Joined: Apr 13, 2009
Posts: 347
Location: South West France
    
  16
The Aga is a thermal mass stove which you can cook on and in, (The oven is fantastic !) which heats your home and will also heat hot water. If you used the rocket stove principle you would lose the mass properties because the fire bricks wouldn't get hot enough.

I've been thinking of ways to use a tiny pocket rocket inside the wood chamber to heat only the cooking plate because in the summer I miss cooking on our French version of the Aga (A Godin) so much. 

So far I haven't found a ready-made elbow small enough, so I might convert a bigger one to make a rocket that can simply be moved in for the summer months when we don't light the Godin.

When I've done that, I'll post pictures and in the meantime I'd be interested in comments from anyone else who has done the same thing.


La Ferme de Sourrou : Nos projets avec PHOTOS
                        


Joined: Jul 24, 2011
Posts: 13
Thank you again for feedback.. Our aga is running on coke (hence the contemplation)
They were designed to run 365 days a year.. Lots of insulation.. The heat given off is minimal, around 1000 watts.. Over the year it consumes 1.5 tons of coke.. It weighs about 3/4 ton.. Very solid castings throughout including both ovens..
Modern aga's only run on oil gas or electricity.
The firebox lends itself to an adaption of a small rocket burner and could possibly be overheated once a day and run on stored heat.. The feed would be thru the ash droor..
What do you think?
(still looking for a drawing of the solid fuel aga to post)
                        


Joined: Jul 24, 2011
Posts: 13
Hi Irene.. I thought I could lift the fire box cylinder out, insert the riser onto a square tube inserted through the ash pan.. Maybe threaded? A single burner would heat both hotplates and ovens because of how the flue gas flow through the aga.. Not sure about the godin? I think the godin heater works on a similar principle to the aga.. P
                        


Joined: Jul 24, 2011
Posts: 13
no fire bricks in an aga.. all cast iron..
when the the top of oven temperature is 420 degrees f i can still put my bare hands on the flue box right where it exits the stove.. excellent heat retention..
if you want to use the stored heat for heating you have to open the oven door or lift the insulated lid on the hottest hot plate.. otherwise the heat given off is no more than 12 people standing in a room..
Irene Kightley
pollinator

Joined: Apr 13, 2009
Posts: 347
Location: South West France
    
  16
In the gas and oil Agas there's loads of vermiculite and rockwool insulation to keep the heat in the stove.

when the the top of oven temperature is 420 degrees f i can still put my bare hands on the flue box right where it exits the stove..


That sounds like a good plan.

There's a photo of the inside of the Aga here : http://www.google.com/imgres?q=inside+an+aga+stove&um=1&hl=en&client=firefox-a&rls=org.mozilla:frfficial&biw=998&bih=524&tbm=isch&tbnid=_D90q20kSMOscM:&imgrefurl=http://www.classic-cookers.com/traditional_aga_internals.html&docid=Z3ICy8IJwIlmOM&w=400&h=350&ei=QX8yTuWJBsXIsgbS2bHpBg&zoom=1&iact=hc&vpx=719&vpy=216&dur=297&hovh=210&hovw=240&tx=136&ty=233&page=1&tbnh=126&tbnw=142&start=0&ndsp=16&ved=1t:429,r:15,s:0
Len Ovens
pollinator

Joined: Aug 26, 2010
Posts: 1306
Location: Vancouver Island
    
  16
ptrfid wrote:
Thank you again for feedback.. Our aga is running on coke (hence the contemplation)

Coke used to be pretty standard in the UK... at least it was 50-60 years ago when my mother lived there.

They were designed to run 365 days a year.. Lots of insulation.. The heat given off is minimal, around 1000 watts.. Over the year it consumes 1.5 tons of coke.. It weighs about 3/4 ton..

1000 watts? Minimal? 24/7? Even the rooms I heat with 400watt heaters don't run continuous... 50% on the coldest days. That's a lot of fuel.

ptrfid wrote:
no fire bricks in an aga.. all cast iron..

yes, that makes sense. The iron would store more heat in the same space... also has more mass in the same space.


when the the top of oven temperature is 420 degrees f i can still put my bare hands on the flue box right where it exits the stove.. excellent heat retention..
if you want to use the stored heat for heating you have to open the oven door or lift the insulated lid on the hottest hot plate.. otherwise the heat given off is no more than 12 people standing in a room..

Maybe you were thinking 100watts above then?

Very solid castings throughout including both ovens..
Modern aga's only run on oil gas or electricity.
The firebox lends itself to an adaption of a small rocket burner and could possibly be overheated once a day and run on stored heat.. The feed would be thru the ash droor..
What do you think?
(still looking for a drawing of the solid fuel aga to post)


The current firebox is quite massive but a rocket stove burner is not. The rocket stove (for cooking) is designed to store no heat (but it does store some) and put all the heat into the food. So you would want to replace the food with storage mass. A big piece of iron for example or better yet something that will phase change in the cooking range, like tin, that melts at around 430F. You would find the small rocket a chore to feed as it would require constant attention and feeding to keep it going, because it uses so little fuel at a time. There are lots of plans for small, cheap, easy cooking rockets out there. They won't last very long (they burn out in about a year), but it would show you how it works before you put more energy into building something more permanent.
                                            


Joined: Aug 11, 2011
Posts: 7
It is possible to convert an AGA to wood burning....  though as yet I cannot vouch for the results.  Years ago, I bought an old AGA from a friend http://damnthematrix.wordpress.com/2011/07/19/the-aga-saga/ and, knowing nothing about AGAs, I promptly bought a wood burning conversion kit, which I fitted.  But I have yet to use the cooker, after moving it to its final position where I am now trying to get it all going some fifteen years later!

The good news is that all the parts I need to fix it are now on their way from the UK (I'm in Australia) and should arrive next week I am told.

As soon as I fire it up, I will report on my blog (as above, and here if I can remember to)

Wish me luck!

Mike
                        


Joined: Jul 24, 2011
Posts: 13
hi mike.. the wood conversion is/was available here in australia from scandia stoves, a foundery in victoria.. have heard the agas dont like wood too much.. looking forward to hearing how yours goes..
peter
                        


Joined: Jul 24, 2011
Posts: 13
hello len.. i understand the the aga firebox is a little large.. was thinking of inserting another firebox/riser inside.. the hotplate would become similar to the top of the drum shown in rmh design.. gases would then go down inside the existing cast firebox/hopper then follow the existing path thru the aga..
peter
                                            


Joined: Aug 11, 2011
Posts: 7
Hi ptrfid....  are you in Australia too?  I bought this kit from Scandia... are you familiar with them?

One thing I have recently discovered is that the gases/smoke from the firebox (which is large when you remove the original AGA tube attached to the stovetop ring) go through a slot where the firebox joins the top oven, and over the top of the top oven, through the manifold, and then up the flue.  However, on the top of the oven, and cast as part of the oven, is a restrictor shaped like a half circle which apparently has an are of less than a square inch.  The simmering top plate forms the top half of this half circle as it sits on it.  I am now wondering if I will need to grind this half circle into a bigger one to increase the gas/smoke flow rate....

The whole idea of an AGA is to keep the heat INSIDE the stove and they have interesting strategies to do this (apart from the insulation).  I don't understand how the calorific content difference between the original fuel the stove was designed for (coke) and wood affects the way the stove might or might not work...  I am very much aware that burning anything less than well dried wood is a complete waste of time. No matter what kind of heater/cooker you are using.

Mike
Len Ovens
pollinator

Joined: Aug 26, 2010
Posts: 1306
Location: Vancouver Island
    
  16
ptrfid wrote:
hello len.. i understand the the aga firebox is a little large.. was thinking of inserting another firebox/riser inside.. the hotplate would become similar to the top of the drum shown in rmh design.. gases would then go down inside the existing cast firebox/hopper then follow the existing path thru the aga..
peter


Should be easy to try. I don't think you would hurt anything. I would make it simple and cheap like some of the cooking rocket stoves out there. Just tin cans and ashes for insulating. It would maybe last a year before the tin wore out, but then you would know.
                                            


Joined: Aug 11, 2011
Posts: 7
I have sorted it.....  I rang Scandia (whose website is currently under attack and should be kept away from!) and I spoke to the guy who used to make the kits and "converted dozens very successfully".  He told me that the bar that runs across the top of the top oven and has the half circle cutout in it has to go.  You cut slots in it with an angle grinder, and use a hamme?r to knock out the small pieces thus created.  It wasn't hard, but it was time consuming.  What isn't?

My AGA parts from the UK are arriving tomorrow.....  EXCITING STUFF!
                        


Joined: Jul 24, 2011
Posts: 13
Hello Len.. yes I am going to give it a try.. should be able to insert the rocket component without cutting anything..
just take off the ash pan door.. might even try to include a self feeding hopper.. thank you for feedback and encouragement..
peter
                        


Joined: Jul 24, 2011
Posts: 13
Hello Damnthematrix.. Yes I have seen the conversion and almost ordered one..
Keeping your wood very dry will be critical as to minimise the soot build up under the slow burner..
AGAs arent designed to run on smoky fuels.. We have been burning coke now for 4 years and have
never seen a puff of smoke from the flue..
If you are buying wood the expense could be as high as coke, now $620 per tonne and rising because
of china.. Wood too is on the rise because everything else is, in our area (Southern Highlands NSW) a cubic metre
is as hight as $150.. There is a lot more BTUs in coke, we use around 1.2 tonnes per year running all year round..
You may also have to clean the AGA out more often with the wood conversion, not a job taken lightly as you
have to remove the firebox to do it properly..
So.. it wont cost me much to try a rocket burner (cleaner burning, no smoke) Im thinking to overheat the stove
twice per day and rely on stored heat.. Will let you know how it goes.. Failing that, agas conversion and run it on wood gas..
regards Peter.. PS Let me know how it runs on wood.. I also have a thought on not cutting the damper if you are interested..
                                            


Joined: Aug 11, 2011
Posts: 7
I can buy a whole ute load of hardwood offcuts from the local sawmill for $15... and I am growing trees at the bottom of the block just to have sustainable firewood, but it might take another three years before I can start coppicing those trees.
 
 
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