Gerry, a slot might or might not be better, I simply don't know. As I said, nobody tried this on a bog standard batchrocket before plus there's always the possibility that it won't work at all. Assuming it could work though, it's a sliding scale antway between too sluggy and overfuelling. The difficult point here is to find the sweet spot where both effects are in a reasonable balance.
fraser stewart wrote:"caulk the seams" is that with heat proof stove silicone kit. The black stuff?
The heat proof silicone kit is not up to the job in my opinion. What you need is the black stuff, I have good experience with that. The best out of three was the one from Bison saying "Openhaarden Kit" and "Mastic Refractaire" on the tube. Resistent up to 1250 ºC, 530 grams in a tube.
Luke Perkins wrote:What is your experience using fire brick splits in a batch box lined with fiber board? Do the bricks tend to last for a long time or do they break and need to be replaced within a year or two?
I did only one experiment using split fire bricks inside a CFB box, pushed to its very limits as usual. The bricks seemed to hold well, don't forget those are able to get red hot again and again without any visable damage. My concern would be about the CFB.
Do I expect the splits need to be replaced within a year or two because of heat damage? The answer will be a firm no, not likely, think of counting in ten or more years.
Fraser, I know of one online shop in the Netherlands which sells the ceramic fibre board. https://kachelmaterialenshop.nl/53-keramisch-board- Before you order online, phone them up and ask if the material you want to buy is available. I'd suggest you line the firebox with firebrick splits, it is too easy to damage the walls just by shoving fuel in. The riser doesn't need to be protected. Over time, the riser's walls are starting to sinter and a rigid layer is formed.
More than one of my experiments were built out of 50 mm (2") material and were just screwed together. Use long stainless steel screws and caulk the seams.
It could either the shorter riser or the smaller diameter throat, or both. My guess would be start with the smaller throat, that's more or less how I did it.
Important: if and when it's too small the heater becomes very sluggish and no flame at all comes out of the riser. A little bit larger throat might make the difference. In my view, there's a trade-off between slugginess and overfuelling, a little bit held down is enough to prevent thermal runaway in 90% of cases.
Gerry, in my DSR setup the distance from the riser port to the end port seems to be crucial. I recalculated your numbers and those seem to be correct. You could leave it like it is now, place the second barrel on and see how it goes.
OR you could try other doughnut diameter holes to see if it would make any difference. The length of the riser ought to be a factor also, and last but not least: I honestly don't know whether this trick will work on a vertical riser, ever.
For conversion of imperial to metrics and vise versa I am using Cleave Books Specialist Calculators. About any conversion is in there, money excluded. Satamax is right, but you are gonna use imperial I'd think.
@Gerry, I'll try to explain. In my proposal, the riser port will stay where it has always been, behind the firebox. The top of the riser will aquire a lid with a hole in it, whether or not in the shape of a round hole or a slit, I don't know what would be best. This hole need to be a bit larger csa than the riser port, in my DSR experiments it's 5% or 6%.
The overall effect is that the second restriction limits the maximum air speed in the riser port. It looks counter-intuitive, the speed of the gases in a system is normally dictated by the smallest opening. However, it works a bit different here: in the riser the gases expand tremendously, twice over is easily imaginable. That larger volume need to pass the second port so it will be hold back.
The beauty of this is that while starting up the system, it doesn't experience a second restriction since it's larger as compared to the first. The expanded volume isn't there yet, so the fire is able to develop freely until a certain volume, dictated by the temperature, is reached. As such, it acts as an automatic valve, large when not needed and smaller when an overfuel situation is imminent.
Again, this isn't tried on a normal heatriser as yet and, almost certainly, it won't work the same on a J-tube just because that doesn't employ port restrictions.
During summer 2015 I attended a workshop in Warsaw. Among other things, we built a bare batch box rocket core for demonstration purposes. During the week this was fired repeatedly and one evening, while the flames were peeping out the riser someone asked whether this could be resolved by adding a longer riser. So we placed one meter (3.28') on top of the riser and refilled the thing. Within minutes the flames peeped out again. So we prepared two other lengths of pipe and kicked off the first. And placed the double length on the riser, only to see the flames coming out again. Long story short: even three lengths of pipe couldn't stop the flames to come out.
A barrel or two over the riser do produce resistance, no doubt about but I don't know how much. Based on the DSR2 and now the DSR1/Vortex experiments, I'd think an end port could be a solution. This is a lid on the top of the riser, with a hole in the middle that is 5% or 10% larger than the riser port. The overall effect is that the end port limits the maximum gas velocity in the riser port, or so it seems. Too small end port means the system is getting very sluggish and too wide it is prone to overfuel again.
Disclamer: I didn't try this myself on a bog standard batchrocket nor I know about anyone else who did. The idea came along just here and now.
fraser stewart wrote:My system is a 15cm diameter heat riser. based on the sketch up model dimensions you so generously made available.
according to you message, I would need 200% 15cm, i.e 30cm about the heat riser to the top of the tank (pictured in red)
Is that correct?
Yes, it is but very roughly, it's better done with a simple formula. To start with, imagine the top gap as a ring above the riser, diameter equal to the riser. The surface area of that ring should be at least 200% of the riser's cross section area. For a 15 cm system this is 177 cm², multiplied by two is 354 cm². This last number divided by the riser's diameter will give you the height of the ring, in this case 23.6 cm. So 30 cm is plenty of space for the gases to change 180º course.
fraser stewart wrote:"The T behind the 1st barrel is a double friction point, in the sense it's a 90º bend but also the closed end of the T. In that end is a weak vacuum, slowing down the stream.
And last but certainly not the least: it would be much, much better to have that 2nd barrel coupled to the 1st without an intermediate stove pipe in between. OR, just assuming this might be impossible for whatever reason, just a straight pipe of a much larger diameter. When completely open to each other, those barrels will act like one larger bell of a funny shape. "
so dont use a pipe of 15cm, but something much larger and connect my bench directly to the tank (pictured in red)
Yes, that's correct. The result being a much smoother running heater. By the way, your second picture indicates a 5 cm top gap which is clearly much too cramped.
Fraser, I suspect there's a flaw in the prototype you've built so far. In order to maintain a good gas flow one need to provide lots of space for every change in direction. 150% of system size for a 90º bend, 200% for a 180º bend. The reasoning is this: friction is killing the gas flow which is absolute necessary for the correct functioning of the afterburner.
It's unclear what system size you have there, but to name a few pinched spots: the space above the riser, known as the top gap.
You don't show any picture of the front, but I think the core is placed reasonably low. In case the core is too close (just a couple of inches) to the back wall of the barrel this will be in combination with the 80º direction change another pinch point.
The T behind the 1st barrel is a double friction point, in the sense it's a 90º bend but also the closed end of the T. In that end is a weak vacuum, slowing down the stream.
And last but certainly not the least: it would be much, much better to have that 2nd barrel coupled to the 1st without an intermediate stove pipe in between. OR, just assuming this might be impossible for whatever reason, just a straight pipe of a much larger diameter. When completely open to each other, those barrels will act like one larger bell of a funny shape.
This is what I built in a couple of instances and it worked beautifully. There's are examples on the batchrocket site, the bell with two-sided blind ended bench and the Mallorca build.
T Giles wrote:how tall is the top box compared to the firebox,
The front of the top box is square, i.e. width and height are equal to the width of the firebox.
T Giles wrote:should the riser stub be flush with the top box back wall or should there be space,
The best results were obtained with a firebrick liner of 30 mm on three sides of the riser stub, left, right and rear. A couple of months ago I tried the development model (a 125 mm or 5" version) without this liner. Don't leave it out, results were dramatically worse.
T Giles wrote:and how large should the stumbler block be
For the 150 m (6") version that would be approx. 40x40 mm (1.57" x 1.57").
T Giles wrote:Using the ratios on batchrocket.eu I have calculated the size that a box with a 2" riser would be. I havent heard of a box that small being attempted before, and Im curious if the drastic change in size will adversely affect efficiency.
Hi T, I understand you are aiming for a 4" version of the DSR1. First, a 4" batchrocket of any version is not a practical thing to use although it can be very powerful. The problem lies in the fact you have to feed it quite often with small sticks in order to keep it going. Second, the DSR1 didn't cut the cake in a real life situation inside two barrels and coupled to a decent chimney. In fact it went in thermal overdrive 50% of the times I fired it, consuming fuel faster and faster at an alarming rate until it was too much for the afterburner function to cope with. Resulting in lots of unsightly black smoke until all the fuel was gone.
No gains to harvest, rather the opposite.
T Giles wrote:the first and foremost tweak would be moving the port to the top of the firebox, rather than the rear, similar to the double shoebox design seen on peter van den berg's more recent videos. However, unlike the more square shape seen in his videos, I would like to retain the long(tall) narrow port that the original batch box design has.
Please have a look at even more recent videos, starting with Batch Box Rocket Stove 20 up to and including 24. That's about another implementation of the Double Shoebox, Mark2 in this case. This one has led to a complete and thoroughly tested version which works surprisingly well. Mind you, development of this one took a full year.
T Giles wrote:can a vertical riser be used with a port that rests on the top of the firebox?
No. Tried that one a long time ago, been there, done that.
T Giles wrote:another design change I wish to implement would be moving the 45° angles from the bottom corners to the top corners of the box. I am unsure about whether those would extend all the way back in the firebox or stop just shy of where the port would begin.
Those 45º angles are there to concentrate the charcoal in the middle of the firebox, they won't have a function on the ceiling at all.
In case you are looking for a simpler and more compact batchrocket design, have a look at https://donkey32.proboards.com/thread/3503/double-shoebox-rocket-mark-ii It's quite a long thread but worth to read it all, if you are interested of course. Some remarkable features are incorporated in this particular design, I got it to the point where it was unable to go into thermal overdrive. No matter what I did to it, it simply refused to belch smoke.
This design isn't published on batchrocket.eu yet, mainly due to health issues. But drawings in SketchUp format are available.
Thanks for the offer Lukas, I'll think about it, seriously!
Your calculation of a bell is not correct, you are ignoring the ceiling here...
Assume the ceiling is internally 85x85 cm, that's 0.72 m². Now 7.2 m² minus 0.72 m² is 6.48 m², divided by 4 is 1.62 m². This last one divided by the assumed 0.85 m means the walls are 1.9 m high internally. Externally the bell would be much wider, deeper and higher, of course. Lift the firebox 40 cm from the floor for convenience and bob's your uncle.
In case you dont want the bell to be higher than 1.8m internally then the ceiling should be 0.89x0.89 m. Walls are then 1.8x0.89 m.
Peter van den Berg wrote:...the chimney diameter..
Talking about chimney diameter, those chimney metal pipes I've seen selling online in my country are anywhere from 120mm to 200mm. So does the pipe's diameter has to be 180mm if the heat raiser's diameter is also 180mm or there's no connections whatsoever between any of heater's dimensions and the pipe diameter?
Chimney (pipe) diameter need to be the same or at least very close to the riser diameter. All the other dimensions are derived from the riser diameter, that's how the spreadsheet works and consequently the table as well. In case you want to use an intermediate figure and are wary about using the spreadsheet I can do the calculations for you.
Lukas Muller wrote:One more question. Peter says regarding the relation of batchbox and bell size;
17.5 cm (7") ISA 7.2 m² (77.5 sq ft)
That would be, probably, one that would suite my needs. So ISA of 7.2m2 - that should be divided by 4(sides of the bell)? Or by 5 where the fifth surface would be the cover/"roof" of the bell?
In case you want to implement the heater as a true cube, the ISA should be divided by 5. For determinating ISA all the surfaces count except the floor. In practise, the heater would be higher than wide and deep because of the required minimum riser length. Don't worry about the walls of the firebox and riser, those should be insulated with superwool anyway. Don't forget the distance between riser top and bell ceiling (known as the top gap) should be equal to the riser's diameter at the very least
Thomas answered your questions already, bar the one about the calculated base number. That base number is used for to scale the combustion core and its parts without steps as in the provided table. To determine it, multiply the chimney diameter by 72.34%, the resulting figure is the calculated base number. All the other dimensions of the core are derived from it, that's why it is called the base number to begin with.
I have chosen this method so it would work all over the planet, irrespective of whatever measurement system one is using.
Having said that, all the above information and more is already on the website, namely above and below the dimension table you've already seen. I'd recommend you read that thoroughly.
Please see http://batchrocket.eu/en/building#dimension
Just a suggestion: try to position the throat in the middle and a bit lower than the firebox. And the cross section area of that throat about 70% of the riser behind it. Then you would end at the batchrocket specification which is tried and tested by now about 500 times using a gas analizer.
Mind you, it can also be done employing a single vortex, i.e. the venturi opening at the side. In that case the csa should be a bit smaller, say 60%, and the opening should be lower than the firebox again. The bottom of this throat, gate, port or whatever one would call it always at the level of the firebox floor. During a lot of experiments the single vortex results always weren't as excellent as its double counterpart.
Back in 2012, during the 9 months' development of what was later dubbed as batchrocket I did some measurements on vortexes and their relative performance characteristics. In short, a single vortex works although clean burning was induced somewhat later in the combustion process and the riser should be at operating temperature. A double vortex device isn't any more complicated to build but can be run clean much earlier in the process.
In fact, the moment the roaring sound starts, the CO level drops down, even in a stone cold core. This wasn't the case with a single vortex so I concentrated on its double counterpart which looked like to have the best papers to a succesful and simple to build core. A single vortex device might be persuaded into comparable behaviour but in order to do that one need lots of time and a calibrated gas analiser. The chance to hit the right proportions and shapes by sheer accident and first time is actually equal to zero.
Most of the time the digital thermometer can withstand and measure 2370 ºF or 1300 ºC, but the K-type thermo coupler can be used up to 1000 ºC or 1830 ºF. Above that temperature they'll die silently, I've seen that happen multiple times, much to my dismay. There's another thermo coupler that will survive 1300 ºC, unfortunally I forgot which one. And I might add: the thermometer need to be ready to accept those higher specc'd couplers.
Mine is a simple two-channel type only useful for K-types from Conrad Electronics. At some point I could borrow a higher specc'd instrument with couplers, highest recorded temperature using that one was 1172 ºC or 2140 ºF, close to the theoretical maximum of 1200 ºC or 2190 ºF for an atmospherical aspirated wood fire as I was led to believe.
Peter van den Berg wrote:The primary air is large enough, on average it's about 25% of a round riser, in your case 4.9" sq. That said, in my own 6" system the combined air inlet is 24.5% at most. My heater is presumably running with lower air excess and efficiency should be higher as a consequence. Yours will run fine as it is, given the low exhaust temperatures. Keep the thing running day by day until it's getting too warm outside, sensible conclusions about this setup can be drawn when running in period is done.
Spotted a mistake, yours is a 7", not a 5", my bad. So a combined air intake like mine for a 7" should be on average 9.6" sq. It might be that your primary inlet could be somewhat larger, hard to say since the inlets are separated. When the heater is all dry, using a larger inlet means chimney temp will be higher. As I mentioned, I start the thing with the door open a crack. When I forget to close it further down the burn the chimney temp tend to rise up to 120 ºC or more. Ermmm... that's equivalent to 248 ºF, I regard this as higher than necessary. The 140 ºF you mention is quite low, just above condensation temperature. But then, as long there's no puddle of condensation fluid to be seen anywhere at the base of your heater you're good.
thomas rubino wrote:By using a piece of angle , held in place by the last two angled bricks. This would deflect possible sparks but not impede the airflow!
Is this correct ?
Yes, it is. It also helps against pieces of coal that could roll down in front of the air inlet. And as I said, to keep the ashes in. What you are experience now is the original setup what it was like with an overhead p-channel. Air is blown straight into the fire and by doing that fuel overload point is reached earlier. The floor channel and threshold combination slows startup down somewhat but fuel overload chance is deminished. And last but not least: in Matt's layout the primary air is higher up as well.
thomas rubino wrote:I am wondering if my primary air hole is large enough? I went with 5" wide by 1.25 tall = 6.25 " The secondary air is 1.75 x 3.5 = 6.12"
I am getting a complete burn with very little ash left at the end, so maybe those are the correct sizes? I believe I followed your parameters.
It just feels like it would burn even better with a larger primary air. Or would adding extra primary air change the burn to be less than optimal?
The primary air is large enough, on average it's about 25% of a round riser, in your case 4.9" sq. That said, in my own 6" system the combined air inlet is 24.5% at most. My heater is presumably running with lower air excess and efficiency should be higher as a consequence. Yours will run fine as it is, given the low exhaust temperatures. Keep the thing running day by day until it's getting too warm outside, sensible conclusions about this setup can be drawn when running in period is done.
Correct me if I am wrong, but I think you rebuilt the core area only. Which would mean moist that need to be driven out isn't that much. The Skamol bricks however, are reluctant to release their moist, I experienced during the 2017 Innovators Gathering. So in future the end temp might rise a bit. Which is good as it's markedly low now, is that thermometer a surface one or one with a probe?
I'd recommend to install a threshold in the shape of an angle iron at right angles over the floor channel's feed. It would conveniently hold ashes out of the way. In your case that's easy, two angled bricks could hold the horizontal flange in place. No need for welding it to the floor channel then.
I'd second Mark, a reflector screen works wonders. The effect of heat that's slowly charring the wall's structure means it could become a serious fire hazard. Reason for this: the self ignition temperature of charcoal is much lower as compared to wood itself.
My own mass heater is about 3" away from a plasterboard on wood frame wall which is filled with mineral wool also. In practise, during depth of our mild winters, the heater rear wall became far too hot to touch. The plasterboard wall became worrying hot and I decided to do something about it, preferably wihtout breaking down the heater beforehand. My first idea was to use a sheet of aluminum but that wasn't rigid enough. Than a piece of corrugated iron which was too much volume. Until I found a Lewis plate, common in Europe used for reinforcing a concrete floor on wooden floor beams. I mounted the plates on three aluminum strips, a little bit longer than the heater's width so I could manage to mount the assembly in place.
Net result: the steel is away from the wall, lots of air is able to stream behind it because it is about one foot from the floor. Thickness is just half an inch. During last winter the plate never reached a temperature more than hand warm although the heater rear wall was far too hot to touch.
Here's a picture of a left-over piece and how it is mounted behind the heater.
Gerry Parent wrote:Lighting up the batch though, there was just a little bit of smoke that came into the room while I lit the fire and as soon as I put the casserole door on (wedged slightly open), it ran in the right direction and all was good till the end of the burn. I put some extra wood in it about 15 minutes into the burn and no smoke came out the door at all. It behaved with great draft like it was in the middle of winter.
Now, the rest of the system hasn't changed except the core, so all things being equal, the batch is the sure winner in my books for being a non-babysit type of stove during the shoulder season in particular.
Good to hear it runs as hoped for. The following is mostly speculation, although there are strong signals it could be true.
The port seems to act as an amplifier of existing draft. Which means there should be some draft, however small. Even a whisp of wind over the chimney end is often enough to get it going. It's imaginable there are some circumstances that draft is completely absent so nothing is there to be amplified.
A simple check: when the heater is completely cold and unfavourable circumstances as you described are present, stick your hand into the port and feel if there's any draft at all. When there is, start a small fire right in front of the port and it will go whithout as much as a hiccup.
Jason Wingerson wrote:Would i be able to install a pebble style RMH in the basement and expect it to warm the entire house radiating through out? The basement currently is only used for utilities and time isnt spent down there. (may change in future but for now)
No way, one need to be in the vicinity of the RMH, even sitting on the bench, before it's comfortably warm.
Please, build that heater in the living space. It might take a hefty footing in the basement but at the end it's worth its weight in gold half of the year.
Maybe you need to change your view from a central heating boiler in the basement to a hearth in the living room where all inhabitants flock together when northeastern wind is howling outside.
Gerry Parent wrote:Peter, I think I remember reading something about you saying something over at Proboards.com (which I can't find right now) that flames that come out of the riser are not the most ideal situation. If this was you that said this and is a correct statement, could you elaborate on it a bit and what could be done to make it more 'ideal'.
We are entering fundamentals here, largely untrodden territory I might add. In an ideal situation combustion is all over and done within the confinement of the riser. Flames out of the riser isn't a good thing: compare it to a candle flame. What happens there is that the oxydizing of the combustible material only takes place at the outside of the flame. Inside there's no oxygen so therefore no burning.
Flames out of the riser usually are oscillating, in a split second it comes up, goes down and up again. Looks like it's doing right, after all it isn't like a steady candle flame is it? But outside the riser the temperature is much, much lower and therefore one of the conditions in order to achieve complete combustion isn't met anymore. I didn't come up with that by myself, the Testo teached me that flames out of the riser aren't as good as one might think. Lots of carbon monoxide and some smoke as well are released into the outside air. Apart from the fact that smoke is wasted fuel it also becomes a pollutant, we shouldn't allow that to happen.
And no, the flames won't be that high when the barrel is in place, since coaching the gases into a 180 degree change of direction means friction. The larger the top gap, the less friction seems to be a good rule of thumb.
Now how to counteract this effect, adding friction isn't something I am particularly fond of, quite the opposite. But during development of the DSR2 I learned another thing: the end of the riser, expansion room or whatever you like to call it can be made smaller than system size. Just a bit more csa as the riser port seems to do the trick, any smaller than that and the whole thing became very sluggish. The maximum gas velocity in the riser port seems to be limited by the end port, combustion goes on in a less violent way and CO production is very low.
This effect of the above is largely not understood yet, it has something to do with expansion of gases between riser port and end port. While fiddling with the DSR2 I tried restricting the top of the extremely short riser and the whole of the thing stopped working the correct way entirely. It looks like there need to be some sort of expansion room between those two ports. The overall effect is an afterburner flame that stays largely inside the riser stub. Running full tilt the flames are entering the expansion space but tend to stay at the rear half due to the stumbling block halfway the expansion room's ceiling.
In case this end port thing is one of those effects dictated by laws of physics it might work on a straight riser as well.
I need to stress this is pure speculation, I didn't try this with a straight riser as yet so the waiting is for somebody to try it out.
Gerry Parent wrote:How close can the wood be placed to the stub? Right up to it or best to leave a gap for air flow?
Right up to the stub is OK no problem, air flow is going around it anyway. Left and right of the stub the fuel could be shoved in right up to the rear wall although a small gap would work slightly better so the fire is able to work itself down close to the port first.
What I do as a habit: I shove logs in until it touches the rear wall and pull it back about an inch. Please don't be too religiously regarding this, it's just a way to make sure there's some space there. Sometimes a piece is too long for this method so I let it touch the rear wall anyway.
Shoving a piece, however small, into the port will disrupt proper gas flow in port and riser which will inevitably lead to smoke out of the chimney stack. Visable smoke inside the firebox isn't uncommon, as long as the afterburner flame is raging it will be taken care of by that.
Gerry Parent wrote:1) Do you load your entire batch of wood in (to within about 2" to the ceiling) then reach way to the back to light it with a long match? What I found is that its takes a while before the fire catches the wood below it when lit from the top vs starting it at the base of the stub.
What I do is loading the entire batch for that moment. Biggest pieces first, somewhat smaller on top of that and kindling on top of that. I tend to leave a lower level in the middle, where I place a handful of small tinder and light that with a single barbecue lighter. Most of the time 2" from the ceiling isn't enough to reach the back so in practice I light the fire halfway. This method allows for stacking the entire load, as opposed to starting low in front of the port and adding more fuel while the fire grows.
Gerry Parent wrote:2) If the door is put on prematurely after lighting from the top back (before lets say 10 minutes) does the fire die down almost to the point of going out?
The upside down firing method requires an emphasis on primary air for the first 10 or so minutes of the burn. That's why I leave the firebox door open about half an inch (one finger thick). When the door is closed too early, in some instances I've seen the fire goes down to the point that the afterburner flame pops off, literally. Results in this sense means what the Testo is making of it, on average significantly better than the other method over the course of ten burns each.
Just weld the threshold to the floor channel's feed and don't try to empty all the ashes out when you are at it. I almost never do unless I want to take the floor channel out to have a look at the bottom of the riser.
Thomas, I didn't realize you meant the pink type, those are quite good. I've used those in the past at Paul Wheaton's and those are soft but relatively firm. Given the fact you being the only user would be a workable situation. When you are aware of the limitations of the material, please use it and stay careful. As a material for a firebox from a pyro point of view, those Skamol bricks couldn't be any better.
The kind of glass that says "Schott" and "Ceran" in one of the upper corners is glass ceramic, certainly not tempered glass. I have cut one at Paul Wheaton's in 2017, in fact it is the one of the rocket cook top in Allerton Abbey. And I did some small clear pieces at home, also using a tile wet saw. Very important: support the glass with a piece of plywood or the like and cut it in two or three passes. I never tried to cut it with an ordinairy glass cutter, by the way.
Yes, I am listening.
And no, you'll need a larger size in order to have it in proportion. Let's see... that would be 1.85" square by 1/8" thickness. One of 1.75" square by 14 ga or 0.083" thickness being the closest according to MetalsDepot. Don't be scared because of the lesser thickness, heavier steel doesn't necessarily last longer.
Last night the total of unique visitors of the site exceeded 150,000. At the same time the total views counted 409,777. It took 14 months to go from 100,000 to 150,000.
At the moment translations aren't doing well. Russian has grind to a halt, Chinese, German and Portuguese didn't come to light at all and the Italian translator can't be reached anymore. I am lagging behind myself with the publishing of the Double Shoebox Rocket developments, it's high time to start writing a longish article. Both in Dutch and English, the latter one being the base for all the other translations.
One good thing to mention: I am going to conduct a workshop in Belgium, from 1st through 7th of May. A DSR2 design, bell and bench construction similar but not quite the same as the Mallorca build in 2017. It's announced on Facebook in Dutch, but Google knows what it'll look like in English, more or less.
Miles Flansburg wrote:If I build a large underground wofati, with up to 10 rooms under the larger roof, each room having it's own mass heater. Is it OK to tie the chimneys together at some point so that there is only one exit hole out of the large common roof?
Miles, it won't work unless there's only one heater running at any given time. All the others should be closed very tight. If not, the heater that's running will be hampered by other heaters feeding air (or worse, exhaust gases) into the main outlet. Two fires burning at the same time will influence each other. There's also a large risk of one that runs well and the other feed small amounts of smoke (and carbon monoxide!) into the living space. It's not allowed in building code, and there's some reason to it.
Imagine one great house in rural England, all rooms having a fireplace and separate chimneys.
Those 18th and 19th century people weren't stupid, they knew combined chimneys are dangerous, asking for trouble. Please don't go that route.
Rune Dahlgreen wrote:Now regarding the newest version (since Peter mentions that the the feed/horisontal part is now larger and "The feed is close to twice as large as the stub, csa-wise") is it safe for me to conclude that the horizontal part should be close to 10 % riser CSA and the vertical part of the newest floor channel should stay in the same range, close to 5 % of the riser CSA?
Also back in the days of the P-channel coming down from the 'ceiling' of the fire box Peter emphasized that the width of the P-channel should be as wide or slightly wider than the width of the port. Can we now totally disregard this rule for both the horisontal and vertical part of the newer floor channel?
It would also be convenient to use two 1.5" square ducts side by side as Thomas already mentioned.
The newer floor channel is indeed another animal, other rules apply so the stub is narrower and the feed could be much wider than the port.
Thanks for replying Thomas.
I think there's a way to view Sketchup files irrespective of the operating system, though. It's called SketchUp Free and runs inside a browser. Apart from that, there seems to be a SketchUp viewer app as well for mobile devices.
Edit: Now I see Gerry already provided the same link.
Gerry Parent wrote:In regards to your comments to Thomas, all I can say is that I would never want to have my open minded tinkering nature stifled by others opinions.
I would like to say a lot more but probably would end up being a 'cider press' conversation at that point so.... long story short, you have been nothing but an inspiration to myself and I'm sure many others out there and would dread the idea that you were holding yourself back because of some limiting ideas..... therefore, you have my vote on helping you to keep your imagination tickled for as long as possible! GO Peter GO!
Thanks Gerry, you are surely know how to drive away a person's gloomy worries.
There might emerge some (hopefully simple) addition to the old and trusted J-tube in future. But don't hold your breath, I am working on several projects at the moment. All about building and workshops and so on, no firm plans for experiments as yet.
Gerry Parent wrote:OK, so if I make the (smaller) lower opening the same size as the upper opening (which would then get plugged) which has approximately the same csa as yours, then I'll be good to go. Any benefit of its shape (yours being rectangular) or is square OK?
Square would be OK, rectanglular has the advantage of being low and spread out so the air streams up over the threshold more easily without an extra change of direction.
Gerry Parent wrote:While we're on the subject, what kind of air restricting device do you recommend? I've been using a piece of rock wool stuffed into the air inlet which works but is rather crude! I was thinking more in the line of a typical stove damper or sliding plate.
A sliding plate is probably best, although builders in France find it better to have a valve that could only be open or closed and nothing in between. They have a point there, people tend to fiddle with it and try to slow combustion down which is not what we want.
thomas rubino wrote:Peter, I understand better now, why you are fascinated with batch box's and rather bored with the simple J tube design's.
Actually, I became fascinated by the J-tube design during spring of 2008. Doing all sorts of experiments to find out what the underlying principles were and how they could be optimized. In 2009 I worked a couple of months on optimizing the J-tube itself, the results of that were among others published in the Rocket Mass Heaters book, third edition. There happened to be a strong conservative opposition not to amend the J-tube design so I refrained from doing further development.
When Lasse Holmes came along with his idea of what later became the batch box rocket I jumped on it because it was a new concept so I wasn't disrupting anything. I've always said the J-tube rocket is serving another niche as the batch box rocket. There's no need for deviding into two camps in my honest opinion but it feels like that, there have been rumours in rocket heater community and on permies in particular.
It would be very interesting what would come out of a merger between J-tube and batchrocket technologies, given what is known about those two at this point of time. It could lead to a whole new breed of rocket heaters but although it's tickling my imagination, it won't be me to pick up development.