Development of a compact batchrocket core.

Gerry Parent wrote:Is this how you recommended refueling a batchbox Peter?
When I had mine, I would just lay the pieces of wood on top of the coals.

Both ways are possible. What I described was mimicking the original way to build a fire in a batchrocket: small fire in front of the port and building the entire load on top of that.

Thank you for the clarification Peter.
Appreciate all your research into further developing the Batchbox into yet another flavor of burning wood that any DIYer can build with confidence because of your efforts.

Peter van den Berg wrote:I'd think this is a good moment to call the development over and done, as far as I am concerned.

Making drawings is what I planned to do next anyway, in order to publish them here (and there).

This is fantastic news Peter. Bravo for your hard work and achievement with the new design. There are many of us who will be very appreciative to have access to your drawings once available and continued guidance.

Thanks for the compliments guys, good to know my efforts in the field are valued.

Peter, a question for you on the compact "shorty" core. Now that you have declared the development to be complete, do you plan to build a cast version or is your intention for this to be a simple construction using refractory brick and plates?

The reason for my question is my refractory brick supplier also has a full custom refractory casting facility. I'm wondering if there are others interested in building a batch rocket using this new core design if it might make sense to have molds built of the core elements and we all share in the production costs.

Glenn Littman wrote:Peter, a question for you on the compact "shorty" core. Now that you have declared the development to be complete, do you plan to build a cast version or is your intention for this to be a simple construction using refractory brick and plates?

No plans to do a cast version, so far. For one, I don't need one to have it inside the house and at the moment, nobody has been asking. The original goal was to end up with a compact core and a simpler layout as compared to the original batchrocket design. A tension frame around the core out of dry stacked bricks, like Thomas has been done, would be a good option in my view. Welding tension frames and selling these together with the bricks pattern might be an opportunity for a small business.
A cast core has the disadvantage that all cores built like that tend to develop cracks over time, sooner or later.

Glenn Littman wrote:The reason for my question is my refractory brick supplier also has a full custom refractory casting facility. I'm wondering if there are others interested in building a batch rocket using this new core design if it might make sense to have molds built of the core elements and we all share in the production costs.

Having molds built is a very costly affair, I can tell you that. But who's paying for the molds and who's selling these cores then?

Thank you for your very valued input Peter. It certainly is pretty simple to construct with brick and add a welded frame for tensioning.

I am already pondering the design for my next build which will utilize the compact core in a 6" system. This one will focus on fast heating and I've already sourced 2 stainless steel 55 gallon barrels. Since the core height is very compact, would it be practical to enclose the core in a brick structure and just use a single barrel + a bench?

Glenn Littman wrote:
I am already pondering the design for my next build which will utilize the compact core in a 6" system. This one will focus on fast heating and I've already sourced 2 stainless steel 55 gallon barrels. Since the core height is very compact, would it be practical to enclose the core in a brick structure and just use a single barrel + a bench?

Hello Glen and others, if you were to do the double barrel, were you meaning one on top of the other? or if not enough head room, can a person do two barrels side by side?  I suspect that this would might not work well. If someone has done, I have not seen.  

So that goes back to  if room for only one barrel- would that mean that it could not extract enough heat from a 6" size, to be practical? (thus bench to add.

And lastly, it has been stated that this new shorty core, is scalable... but have not yet seen "back to what dimensions" these are scaled?  

     1) if the scale is based on what we use for a batch box volume, and the port. GREAT.
      2) the short riser. size is base on?
      3) the exit for this short riser?

Inquiring minds want to know.  Perhaps I have missed all this in a thread,  Just point me in the right direction and I will be good.

Hi all,
Here at Dragon Technology Headquarters, I intend to build this Shorty core outdoors in the coming month and ultimately move it indoors to our home.  
I will be fabricating a tension frame to hold it, and laying out the firebrick cutting pattern to build this style core.

Complete frames and plans for the brick layout will be offered for sale as soon as I have built one for myself.

This core uses a specialized door and air intake system different from the original design Batchbox.
I have the plans but have not built one yet, but I hope to be able to offer these for sale in the future as well.
Watch for a new thread here at Permies and check https://dragontechrmh.com/  for updates.

Glenn Littman wrote:I am already pondering the design for my next build which will utilize the compact core in a 6" system. This one will focus on fast heating and I've already sourced 2 stainless steel 55 gallon barrels. Since the core height is very compact, would it be practical to enclose the core in a brick structure and just use a single barrel + a bench?

Building such a core with one barrel and a bench could be done, yes. There's one proviso, though. The transition from the barrel to the bench shouldn't be done with a chimney pipe and two elbows, better to have the transition area at the same level as the bench.

In a more practical way: the brick structure around the core should have room enough to lead the gases behind and/or at the side of the core down and the opening to the bench should be as wide as the bench' internals. This way, the bench will act as part of an oddly shaped bell.

Another way to employ a second barrel since fast heating is what you are after: having a short piece of one size larger stove pipe from low in the first barrel to high in the second which is just standing beside the core/brickwork/1st barrel.

Scott Weinberg wrote:Hello Glen and others, if you were to do the double barrel, were you meaning one on top of the other? or if not enough head room, can a person do two barrels side by side?  I suspect that this would might not work well. If someone has done, I have not seen.

Both ways has been done before multiple times, also in Wheaton labs as it happens. https://permies.com/t/193821/inch-batch-box-rocket-mass

Scott Weinberg wrote:So that goes back to  if room for only one barrel- would that mean that it could not extract enough heat from a 6" size, to be practical? (thus bench to add.

One barrel is definitely not enough to extract enough heat from a 6" system. See the heater in my former workshop, 2 1/2 would be about right. https://batchrocket.eu/en/applications#threebarrel

Scott Weinberg wrote:And lastly, it has been stated that this new shorty core, is scalable... but have not yet seen "back to what dimensions" these are scaled?  

     1) if the scale is based on what we use for a batch box volume, and the port. GREAT.
      2) the short riser. size is base on?
      3) the exit for this short riser?

The Shorty core can be scaled the same way as the normal batchrocket. How it is done is all in this same thread, although scattered around a bit. So I'll explain in short the differences below.

All dimensions are derived from either the chimney diameter or the chimney csa. The so-called Base value or B is 72.34% of the chimney diameter.
Firebox width, height and depth are the same as published on the site, port size is slightly different as the height is 2.1B, depth 1B. Main difference is the riser, height is 5B instead of the recommended 10B. Riser is square, sides are 2Base. The lower half of the riser is square as well, sides equal to the chimney diameter this time. The top of the riser is closed, exit opening is situated in the front. This opening is equal to the csa of the chimney and placed lower, about the same distance as the height of the opening, not critical. All given dimensions are internal.

The upshot of placing the exit lower: temperature goes up quite a bit faster in the riser this way.

Excellent Peter, it is nice to have all the numbers (formula's) in one posting.  

And your breakdown of the questions/answers is great too.

Fantastic that you have done this work with now proven results.   Using your past numbers  for a batch rocket on my 7" RMH with a single bell, I couldn't ask for anything better.

Thanks again.
Scott

Peter van den Berg wrote:Building such a core with one barrel and a bench could be done, yes. There's one proviso, though. The transition from the barrel to the bench shouldn't be done with a chimney pipe and two elbows, better to have the transition area at the same level as the bench.

In a more practical way: the brick structure around the core should have room enough to lead the gases behind and/or at the side of the core down and the opening to the bench should be as wide as the bench' internals. This way, the bench will act as part of an oddly shaped bell.

This is excellent Peter and right inline with my initial thoughts. My developing concept was actually an inspiration and adaption of your Mallorca build with the bench being a bell chamber off of the primary bell. However in my thinking I would build a lower main bell in brick, extend the bench to one side and have the barrel over the shorty core. I have headroom for a stacked barrel arrangement, so this is possible too.

You mention in your reply to Scott Weinberg that 2 1/2 barrels would be about right from a heat extraction standpoint but does that assume a bell that is 100% barrels? If I substitute a brick lower section + bench, reducing some of the 2 1/2 stacked barrel surface area (perhaps 1 1/2 barrels) to get a little more balance between instant heating and thermal storage I assume this would achieve good heat extraction and acceptable chimney exit temperatures. Would the normal ISA target for a 6" system of 57 sq ft still apply in this type of design?

Full disclosure folks... Thomas, Scott and I are conspiring behind the scenes to build our own versions of Peter's new "shorty core" design. Thank you Peter for your work to spawn a rocket evolution.

Glenn Littman wrote:You mention in your reply to Scott Weinberg that 2 1/2 barrels would be about right from a heat extraction standpoint but does that assume a bell that is 100% barrels?

What I meant was the three barrel tower arrangement of my former workshop, the exit somewhat above the floor. However, that is when steel barrels are used. I honestly don't know about stainless steel, emissivity of this material is quite a bit less as compared to steel.

Glenn Littman wrote:If I substitute a brick lower section + bench, reducing some of the 2 1/2 stacked barrel surface area (perhaps 1 1/2 barrels) to get a little more balance between instant heating and thermal storage I assume this would achieve good heat extraction and acceptable chimney exit temperatures. Would the normal ISA target for a 6" system of 57 sq ft still apply in this type of design?

I'm inclined to say this should be more because of the stainless steel. How much more is anybody's guess at this point, I can't help you with that.