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Post by peterberg on Nov 1, 2012 3:54:19 GMT -8
I have about 8cm between side insulation, and the 150mm hole. Heat riser is 160mm. Pipe is 153mm diameter Max, Forget about all the square cm's, the exhaust pipe itself isn't the important item. There should be more than 8 cm on average between the opening and the opposite wall. When it's less, this stream opening will be smaller than the riser c.s.a. I'll try to explain. The segment isn't the restricting factor, but an imaginary ring around the opening in the steel bell. There has been written about this topic earlier in the Helpful hint thread, this ring is called the stream profile. In your case, the 8 cm is probably the largest distance from the middle of the opening to the opposite wall. Which will imply a smaller distance at the left and right edge. That could be as small as 5 or 6 cm. On average, the ring height would be 7 cm at the most. The gases are coming down this segment and can't stream through the opening all at the same time, there's the restriction from the height of the ring. Moreover, this ring isn't useful over its entirely circumference because there's nothing coming from below, and the sides probably just a little bit. So my guess is: only the top half is contributing to the available exhaust space. This half profile can be calculated as follows: diameter of the exhaust multiplied by Pi, multiplied by average height of ring, divided by 2. So, this will come down to 15*3,14*7/2= 164.85 cm2. That's significantly less as compared to the 201 cm2 of the riser c.s.a., in fact it should be slightly larger to be on the safe side. I can identify two solutions: 1) make another hole higher up, where there's no wall at the opposite of the exhaust opening. Or further away, for that matter. 2) enlarge the original hole to 180 mm and use a restriction pipe going from 180 to 150 mm, this will solve the problem as well. As a side note, look closely at the construction you are using now. Does the elbow piece stick inside the bell, however small? This will restrict the opening further, so it's best to have this solved first before trying anything else. Long story, hope this is clear. |
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Post by satamax on Nov 1, 2012 10:10:09 GMT -8
Hi Peter. I doubt this is the case. I mean, widest size of the batch box, outside, 36cm, One 5cm layer of rockwool each side, that's 46cm. The inside of the water heater is about 65cm. So i have 19 left. That's 9.5 each side. i said 8 accounting for the pipe overhang inside the curve. If it is that. Anyway, once brazed, i'll grind it as well. Look at the other side, i don't have a pic of the side where i've cut the hole.  I understand the ring theoretical surface, it's something we have to know for voicing when building guitars. Peter, why divided by 2? Circumference is Π x D Or am i going astray? So 15xΠ= 47.1238 this even times 5 is 235 aproximately. And i'm prety sure i have more than five! |
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Post by peterberg on Nov 1, 2012 12:57:02 GMT -8
I understand the ring theoretical surface, it's something we have to know for voicing when building guitars. Peter, why divided by 2? I've explained that in my last post, the gases do come from above almost exclusively. The only active part of the imaginary ring is the top half, so that's why I divided the ring by two. In order to get to 235 cm2 you mentioned, you have to have 10 cm of space as an average. You'll be alright when the elbow is trimmed back, I'd think. |
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Post by peterberg on Nov 9, 2012 7:06:39 GMT -8
Some development has been done by Joris Pouls in Belgium. His last build is a cook stove, he used slightly different dimensions in the firebox and turned the core 90 degrees. The gas stream is now from right to left instead of from front to back. He filmed different stages of the hottest burn to date, see the moment the stove's picking uphalfway the burn andthe very top of the burn.I presume he wouldn't like to open the door at the third stage, this thing is really intimidating. Even during the second stage it's growling like a hungry bear. Let alone the last stage, pulsating and sounding like a steam engine at full speed. Some photos do picture the chimney pipe, showing an alarming bluish color. This pipe has been recuperated from a hearth inset, hence the coloring. |
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Post by satamax on Nov 13, 2012 10:20:29 GMT -8
Peter, if you pop around.
I think it would be à good idea to narow the firebox à smidge. What do you reckon, i do it with the same firebrick i've done the V at the bottom? Or should i source few insulating firebricks?
Thanks a lot.
Max.
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Post by peterberg on Nov 13, 2012 11:38:56 GMT -8
I think it would be à good idea to narow the firebox à smidge. What do you reckon, i do it with the same firebrick i've done the V at the bottom? Or should i source few insulating firebricks? Narrowing the firebox would help to keep the smoke inside, yes. It doesn't matter what sort of bricks you'll use, the difficult part is to keep these in place. |
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Post by matthewwalker on Nov 13, 2012 11:41:16 GMT -8
Peter, I just wanted to say thank you. I cast a quick and dirty version of your firebox over the weekend and I am amazed at the power of that thing. Mine is highly insulated and ROARS right from start up. It exhibits the "ram's horn" pattern, but don't try to look in there and see it. You'll burn your eyelashes and bangs right off. DAMHIKT.
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Post by peterberg on Nov 14, 2012 1:26:48 GMT -8
Peter, I just wanted to say thank you. I cast a quick and dirty version of your firebox over the weekend and I am amazed at the power of that thing. Mine is highly insulated and ROARS right from start up. You're welcome, Matthew. I'm really pleased when someone's using my ideas and build their own stove. It's a true rocket stove, judged by the sound of it. It exhibits the "ram's horn" pattern, but don't try to look in there and see it. You'll burn your eyelashes and bangs right off. DAMHIKT. Yes, I've been there, done that. You can't say I didn't warn you! ROTFL ;D |
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Post by satamax on Nov 17, 2012 12:07:48 GMT -8
Hi everybody.
Well, i did a arther lenghty burn today outside. It smoked back as usual for this one. I did two modifiucations, brazed the exhaust tube connecter, so i don't have anything sticking inside. That didn't help. Then made a door, with a grid in it, with the CSA opening size. And that cured the smokeback. I mean each litle sqare of the Grid is 16²mm, and i did a grid of 27cm², which equals aproximately the 16²cm of the heat riser, in open surface. No smokeback whatsoever. I need to bend it well tomorow so it's flush with the moutrh of the batch box. And i think i'll be sorted. We'll see how it goes tomorow. If right, in the flat it goes. I mihgt add some mass on the un used side, and on top of the firebox. See what that does.
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Post by satamax on Nov 18, 2012 11:20:42 GMT -8
Burning nicely. www.youtube.com/watch?v=eqlrXTvsa2o&feature=youtu.be Well, ready to be burnt, i need the paint off for sure. Few questions, can i have the horizontal tube in the mass lower than the batch box? Is it absolutely necessary to have theses the same diameter, or could i use bigger. I have one metre of 10 inch, two of 8", two of 18cm and two of 153mm My heat riser diameter is 16cm. |
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Post by peterberg on Nov 18, 2012 12:24:25 GMT -8
Few questions, can i have the horizontal tube in the mass lower than the batch box? Is it absolutely necessary to have theses the same diameter, or could i use bigger. I have one metre of 10 inch, two of 8", two of 18cm and two of 153mm My heat riser diameter is 16cm. The mass flue duct can be at a lower level, yes. Within limits of course, don't get lower than half the length of the riser, even assisted by a good chimney you can't. I presume you would like to have the duct at floor level, that would be alright. It's perfectly possible to use a wider duct in the mass bench. The gases will move slower and give off more heat per length unit. Best to exit out of the metal stove casing using system size first and entering into the bench have it expanded to a larger size. Beware, you have to have a clean-out door somewhere in that region. Have you thought about making the bench entirely hollow, out of brick or concrete blocks and have it act as a shallow bell? |
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Post by satamax on Nov 18, 2012 13:33:25 GMT -8
Hi Peter.
Yep i'm thinking bout this. With the usual chimney blocks, this would be possible. Only prob imho, is getting it airtight. And thoses blocks are a smidge high. I also thought about making a metal box, the size of the sofa, about 10cm high, one tube entering it at one end, the other one exiting at the other end and à layer of thoses concrete footpath edges above it, or two.
Well, i might just ditch the sofa, as it's an old wreck! Or may be cut it. As it's leather. If i was sure about the air tightness of the half barrel system, i could go for it too. Off to ask a question over at the other thread. Has anybody tried only gravel without any binder in between?
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Post by grizbach on Nov 18, 2012 14:06:01 GMT -8
Peter, Great work on the batch/bell creation!
I need to decide if I want to build a thick stone/concrete bell to replace my rocket. I'm sure I would need the battery as to not over heat my living space.
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Post by grizbach on Nov 18, 2012 14:11:18 GMT -8
satamax, I think you should start your own thread on this.
With gravel, I believe you will only be able to heat what is directly touching the duct.
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Post by satamax on Nov 19, 2012 8:28:02 GMT -8
Any intrest in putting mass below the half barrels?
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