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Peter van den Berg 4 inch Minnie Mouse rocket mass heater  RSS feed

 
Anne Christgau
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Good Morning from across the pond. My first post on Rocket Stoves, Hello to all.
I have a small hut 7' 6" x 18'. No insulation to date. Old wood stove has finally collapsed.
Am very interested in the Minnie Mouse heater / stove, 4" J style in bell, built by Peter Van de Berg at a get together in Montana, have searched the net For more information without success, only one or two photos and a brief description of build by Peter on this forum. Ianto Evans book does not show such a build. It seems to be a relatively easy build for me bearing in mind age and physical ability. Most important it has a small footprint.
Three questions.

1) For the 'Minnie Mouse' Can I use a barrel smaller than the 55 gallon mentioned and still line it with brick for internal mass?
2) I have read that the heat riser is cut down, how far should it come towards the top of the barrel?
3) Alternatively if I cast a 4' batch box for the 'Fat Rabbit' how far could I reduce the size of barrel?

Be most grateful for any advice am not up to speed with the maths or science.
Thankyou
Anne
 
paul wheaton
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I just found this thread.   If you are still watching this thread, I'll see if I can get Peter's attention to answer questions.

There is some video of this as peter and I discuss some design issues in DVD 3 of the new 4-DVD set Better Wood Heat:  DIY Rocket Mass Heaters.


Here is a picture of Minnie Mouse in her new home, the love shack:




I'm not finding pictures of her construction. 

So I fired up DVD 3 of "better wood heat" and grabbed a couple of frames and am attaching them here:


peter-van-den-berg-minnie-mouse.png
[Thumbnail for peter-van-den-berg-minnie-mouse.png]
peter van den berg opens up minnie mouse
minnie-mouse-rocket-mass-heater-innards.png
[Thumbnail for minnie-mouse-rocket-mass-heater-innards.png]
peter explains how the minnie mouse rocket mass heater works
 
paul wheaton
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Here is minnie mouse when she was first introduced to the red cabin:



Ernie and Erica came by to test her out and decided that even though the inner bricks would probably keep any paint from burning off the barrel, they wanted to be absolutely sure.   So they removed all the paint and put her back in:



You can see it in this video:




You need to keep in mind that while this structure is "insulated", it is not insulated particularly well.  In fact, the floor is not insulated.  If you look at the floor, you can see the ground outside through the floor boards.   And if the sun is out, you can even see the ground under the floor boards is illuminated!

But rocket mass heaters tend to still do pretty good in uninsulated stuff!   But minnie mouse does not have a lot of mass compared to other rocket mass heaters.  So people would come, and fire her up and she would warm the space quickly, but people were typically cold in the morning.

Kirk Mobert, one of our rocket mass heater innovators, came and stayed in the red cabin.   He was about to build a new tiny house rocket mass heater in the love shack, and then decided that the best path would be to move minnie mouse to the love shack.   The love shack is smaller and better insulated.  

When Peter van den Berg arrived for the 2017 rocket mass heater workshop jamboree, minnie mouse had not yet been fully installed into the love shack.   He looked inside and said "somebody moved the bricks!"   He also had some ideas for improvements.   So he went to work and now minnie mouse has much more mass inside.  Plus, the improvements made it so minnie mouse has an internal heat shield, so the wood aesthetic doesn't need to be covered up.

Here she is working hard in her new home:



Kirk is staying in the love shack now and reports that the Minnie Mouse is now performing really well.






 
Anne Christgau
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Many thanks for remembering Paul. In Fact when there were no replies I emailed Peter in Holland and he came up with some answers.
It's installed in my hut. J tube at present with no brick lining as yet. Working like a little wonder. Am thinking of making a Batch Box. With casserole door. I hope I can get away with using the same barrel. 45 Gallons English measurement.
, what do you all think.
I hope your Jamboree went well.
All the Best
Anne
 
paul wheaton
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Anne Christgau wrote:It's installed in my hut. J tube at present with no brick lining as yet.


Pictures?

 
bob day
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These are some comments from http://batchrocket.eu/en/building#bellsizing     ; as you know, a batch monster is different from a j channel, so you may need to rethink any changes



The correct sizing of the bell was hard won by experimentation, and like all open source projects contributions came from many different people. Klemen Urbanija from Radomlje, Slovenia found out after a lot of tinkering that a 15 cm (6") system with a single bell with an internal surface area of 6 m² (64.6 sq ft), excluding the floor, gave an exhaust temperature 60 ºCelsius (140 ºFahrenheit). He built his experiment outside the house and changed it several times until the results were satisfying, then he tore it down and moved it inside the house. A new round of problems emerged due to the chimney stack being made of bricks, which extracted heat from the exhaust thereby killing the draw. This needed more tinkering and rebuilding of the bell in order to raise the exhaust temperature and restore the draw. The final result was a figure of 5.3 m² (57 sq ft) of 'heat absorption area'. This is important to grasp, and once grasped it can be seen that the floor area of the bell will not be part of the 'heat absorption area' as the flue exits above it. Equally, if the firebox is built into the bell then the surface area of the firebox within the bell won't play a role in calculating this area as no heat is absorbed there.

The term we use for the total area available for heat absorption within the bell is ISA, short for Internal Surface Area. As noted, this does not include the floor area as that floor does not (directly) absorb heat. The difference between a steel bell which is shedding its heat immediately and one that is storing heat in a mass of stone or brick is marginal in terms of ISA. My workshop heater (see article Three barrel batch rocket) is built out of three oil barrels which together are very close to the same ISA as Klemen's masonry bell and bench. Both systems have a comparable exhaust temperature.

Scaling up of these numbers posed a long-standing problem which was finally solved in 2015. It turned out that the same critical dimension used to scale the size of fireboxes up or down, the cross sectional area of the heat riser, can also be used to scale the bell ISA up and down from the base result determined by Klemen. 2015 was the year that the bell with two cul-de-sac benches was built during the MHA meeting (see article Bell with dead-end benches). The maximum ISA of that 20 cm (8") system and a masonry bell without chimney bypass turned out to be 9.4 m² (101 sq ft). The ratio of Klemen's heat riser CSA to the MHA riser CSA was 1 : 1.77, and the same ratio of 1 : 1.77 appeared in both ISAs. We had found it!

As a consequence we can use the following 'table', and simply extrapolate or interpolate as required. As far as we know, this method works within reasonable limits in both directions.

Riser diameter   /   Internal Surface area

    12.5 cm  (5")   ISA 3.7 m²    (39.8 sq ft)
    15.0 cm  (6")   ISA 5.3 m²    (57 sq ft)
    17.5 cm  (7")   ISA 7.2 m²    (77.5 sq ft)
    20.0 cm  (8")   ISA 9.4 m²    (101 sq ft)
    22.5 cm  (9")   ISA 11.4 m²  (123 sq ft)
    25.0 cm  (10") ISA 14.7 m²  (158 sq ft)
 
paul wheaton
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I just now saw another pic of the minnie mouse when it was first being built:





(source)
 
Anne Christgau
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Morning Paul Thanks for the photos of Minnie Mouse. Sorry we have none of our hut stove, My build was very messy and it worked well. But the fitting of the firebox and riser into the barrel was a bit makeshift even I have to admit, so Peter has removed the firebox and riser ( he has just told me) refining them as only you men can do!!!. And then putting in the bricks for mass. Should Bricks be all fire bricks, or firebricks lower down and ordinary ones above. I think we will be giving the batch box a miss for the time being, but it's not out of our mind. I will take photos and post them to you when all is done.

Thanks
Anne
 
Anne Christgau
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bob day wrote:These are some comments from http://batchrocket.eu/en/building#bellsizing     ; as you know, a batch monster is different from a j channel, so you may need to rethink any changes



The correct sizing of the bell was hard won by experimentation, and like all open source projects contributions came from many different people. Klemen Urbanija from Radomlje, Slovenia found out after a lot of tinkering that a 15 cm (6") system with a single bell with an internal surface area of 6 m² (64.6 sq ft), excluding the floor, gave an exhaust temperature 60 ºCelsius (140 ºFahrenheit). He built his experiment outside the house and changed it several times until the results were satisfying, then he tore it down and moved it inside the house. A new round of problems emerged due to the chimney stack being made of bricks, which extracted heat from the exhaust thereby killing the draw. This needed more tinkering and rebuilding of the bell in order to raise the exhaust temperature and restore the draw. The final result was a figure of 5.3 m² (57 sq ft) of 'heat absorption area'. This is important to grasp, and once grasped it can be seen that the floor area of the bell will not be part of the 'heat absorption area' as the flue exits above it. Equally, if the firebox is built into the bell then the surface area of the firebox within the bell won't play a role in calculating this area as no heat is absorbed there.

The term we use for the total area available for heat absorption within the bell is ISA, short for Internal Surface Area. As noted, this does not include the floor area as that floor does not (directly) absorb heat. The difference between a steel bell which is shedding its heat immediately and one that is storing heat in a mass of stone or brick is marginal in terms of ISA. My workshop heater (see article Three barrel batch rocket) is built out of three oil barrels which together are very close to the same ISA as Klemen's masonry bell and bench. Both systems have a comparable exhaust temperature.

Scaling up of these numbers posed a long-standing problem which was finally solved in 2015. It turned out that the same critical dimension used to scale the size of fireboxes up or down, the cross sectional area of the heat riser, can also be used to scale the bell ISA up and down from the base result determined by Klemen. 2015 was the year that the bell with two cul-de-sac benches was built during the MHA meeting (see article Bell with dead-end benches). The maximum ISA of that 20 cm (8") system and a masonry bell without chimney bypass turned out to be 9.4 m² (101 sq ft). The ratio of Klemen's heat riser CSA to the MHA riser CSA was 1 : 1.77, and the same ratio of 1 : 1.77 appeared in both ISAs. We had found it!

As a consequence we can use the following 'table', and simply extrapolate or interpolate as required. As far as we know, this method works within reasonable limits in both directions.

Riser diameter   /   Internal Surface area

    12.5 cm  (5")   ISA 3.7 m²    (39.8 sq ft)
    15.0 cm  (6")   ISA 5.3 m²    (57 sq ft)
    17.5 cm  (7")   ISA 7.2 m²    (77.5 sq ft)
    20.0 cm  (8")   ISA 9.4 m²    (101 sq ft)
    22.5 cm  (9")   ISA 11.4 m²  (123 sq ft)
    25.0 cm  (10") ISA 14.7 m²  (158 sq ft)


Thankyou Bob for the brief history, re Batch Box and sizing. I copied Peter V D B Minnie Mouse Stove as far as I could from photos and sizes he gave. All was good. I take on board what you say re batch box and will leave that to the not too distant future ( tongue in cheek). Thanks again
Anne
 
paul wheaton
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Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
 
paul wheaton
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Location: missoula, montana (zone 4)
bee chicken hugelkultur trees wofati woodworking
 
Sander Krijnen
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How about creating some kind of a spiral with the exaust pipe and adding more mass on top of the barrel for more heat efficiency?
 
paul wheaton
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Sander Krijnen wrote:How about creating some kind of a spiral with the exaust pipe and adding more mass on top of the barrel for more heat efficiency?


Adding mass to the top seems like a really good idea to me. 
 
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