thomas rubino wrote:Gerry is that the same riser you were using before?
And is that an 8" system?
How long is your bench?
Peter van den Berg wrote:Hi Gerry,
The batch box rocket system need secondary air, it won't run clean without. There's one exeption though: when it is run open secondary air will come over the fuel to the port anyway. But overall efficiency is quite a bit lower then.
Pulsing is indeed a signal of a restriction down the line. It might be that your J-tube never pulsed but due to the higher heat and velocity of a batch box there might be a spot that is retrictive now. You have a bench with a stove pipe in it that doubles back? In that case the 180º bend might be acting as a restriction, depending on the temperature of the gas stream at the spot.
The above is something that often plays up when the conversion is from 6" J to 6" batch. Never happened when conversion was from 8" J to 6" batch. Better to check every change of flow direction and solve any pinched spot first before hacking into your bench and widening the 180º bend. Provided there's lots of room everywhere, a batch box rocket shouldn't pulse. Even the 8" thingy at Paul Wheaton's never did despite the 5 times change of direction including one of 180º.
Gerry Parent wrote:Question: Do you ever see any flame coming from the top of the pipe where the hot oxygen it being delivered to the top of the port?
Gerry Parent wrote:My top gap is 9" and you can see the manifold transition is fairly large and open (but maybe not for a batch box?).
Peter van den Berg wrote:As you may know, my floor channel arrangement reaches up to about half of the port's height. It is done this way because from my own and some experiments from others the most effective part to add fresh heated air is in the top half of the port. During each and every run flames that seems to come out of the channel can be seen in my heater, continiously for about half of the burn.
Peter van den Berg wrote:It might be that the plunger tube is too close to the exit into the bench.
Peter van den Berg wrote:As I see it, the horizontal feed part of Matt's channel is open at the riser end. It should be closed off and maybe it is, but in case it isn't it would be advisable to mount it in such a way that air can't stream out of that end.
thomas rubino wrote:Could you please tell me the dimensions on your 6" B.B. floor port ? That would be much easier for me.
thomas rubino wrote:The closest sizes readily available here are, 1.5 inch square X 1/8" thick for the stub.
And for the channel I can get 2.5" x 1.5" X 1/8" thick.
Are these acceptable size substitutes ?
thomas rubino wrote:From your photo's) I see what looks to be maybe a 4" - 5" cut out on the thin sides apx a 1/4" - 1/2 " from the end of the channel , with the diamond shape for the stub cut into both pieces.
Are those measurements suitable ? Or are there more precise measurements?
thomas rubino wrote:On the stub) It appears that it starts out as a square cut and then a 45 degree triangle is removed on the angle facing the port and another on the feed side.
Then a deflector is cut to direct the air? The deflector looks to be a diagonal cut flat piece, that stops mid point of the stub?
Gerry Parent wrote:The space where the gasses come out of the manifold and into the bench between the plunger tube and wall of the bench/bell is about 6 1/2" (165mm) X 16 1/2" tall (419mm).
This works out to a csa of about 107 sq inches. The plunger tube is off the floor of the bench/bell by about 4 1/2" (114mm). Any of these areas too tight that may be causing the pulsing?
Peter van den Berg wrote:According to my calculation the plunger tube could do with a minimum of 75 mm (3") so 114 mm is plenty of space, provided it's free all around for the gasses to stream up.
Most of the time, a slow pulse can be deminished by opening the primary air further. What's the reaction when the door is opened while pulsing is going on?
And the opening between barrel and manifold, how's that sized and arranged?
Gerry Parent wrote:Peter, Here is a picture of the chimney cap. I had cleaned all the chimney pipe in the late summer so I know their good. The gap is 2 1/2" (63.5mm) with no screening .
Gerry Parent wrote:Is this something like what your talking about the metal plate or "threshold"? how close to the "upstream end of the feed"? see picture below
Gerry Parent wrote:On his webpage, Matt Walker says he puts his primary air port about 1/3 of the way up from the floor. The bottom of mine is about 1.5" (38mm). Wondering if raising it up this much would have the same effect as your threshold?
Gerry Parent wrote:In the thread bb pulsing Byron Campbell talks about solving his pulsing by creating a velocity stack. Any comments?
Gerry Parent wrote:In regards to the pulsing. I take it as a sign that something isn't perfect with the system. Does it mean though that it causes a dirtier burn, or just more of an annoyance of having to listen to a locomotive making laps inside the house? From some other videos I've seen where pulsing is really prominent, in comparison it doesn't seem like mine is really bad but still would be nice to find the source. I'm sure it'll be found as I continue to tinker. I'll be sure to let you know.
Gerry Parent wrote:It felt like air flow was being restricted too much with it there. Perhaps lowering it a bit, reducing its thickness or a steel plate would be better? I also noticed a bit more smoke in the firebox particularly near the roof area. Opening the door got rid of the smoke.
Gerry Parent wrote:Not sure about what you meant about the cold air being "served at all times".
You said "Threshold and floorchannel should be both at least 2 1/2" away from the air inlet for this to work properly." The floorchannel is buried under the primary air and both of their intakes are seen at the front of the stove so I'm not sure how distance for the floorchannel plays any part in how I have it configured.
So the primary and secondary air are self regulating due to the influence of the threshold? If this is true, why isn't it used on all batch boxes?
Peter van den Berg wrote:"That last one isn't a disadvantage per se, normally I close the air inlet before glowing phase is over. The next run will burn easier through under the lowest logs of the stack due to the fact that self-ignition temperature of charcoal is quite a bit lower than that of the wood itself."
Gerry Parent wrote:So from my understanding, one of the functions of the floor channel is to heat the incoming air so that when it exits the top of the stub it doesn't cool the fire and keeps combustion more clean. With that said, each time I start the stove, I've been cleaning out the ash and any charcoal so that the top of the floor channel is exposed directly to the heat of the fire. With what you said though, leaving the charcoal behind is actually a good thing which makes total sense. I can see the ash being an insulator if too much is left behind so I guess its a moderation thing.
Gerry Parent wrote:In regards to an earlier comment you made about the secondary air shooting flames out of it for half the burn, I still have only noticed this phenomena sporadically. So far the only way I can get this to happen (temporarily) is to dampen down the main air entrance a lot perhaps so there is less of the gasses being disturbed by the fast incoming air and can ignite showing themselves? Maybe an analogy something like a candle not being able to stay lit when there is a breeze. Is this a sign that my floor channel is not operating correctly?
Peter van den Berg wrote:You are getting closer, although the inlet opening is a bit too tight for a combined inlet. Mine is 150x30 mm (5.91"x1.18"), adequate for the majority of circumstances
Peter van den Berg wrote:This not seeing any flame shooting out of the floor channel isn't a sign of malfunction per se. Remember your floor channel is like Matt's pre-port tube, in my configuration the stub is smaller and square, reaching to about half of the port height and, important, the feed is double the size of the stub. Floor channel distance to air inlet is OK.
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.
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?
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.
I've noticed with the square shape that the air is quite turbulent in this 'pool' or depression area by observing the smoke and little bits of ash whipping around. I have no attachment to the square shape, so low and rectangular it will be then with a slider (as I am the only one running the stove and can't really tinker with it to see what happens)
Peter van den Berg wrote: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.