"Vintage" Rocket / Bell by Peter

Greetings guys. Been a while since I've posted.

So was doing some research into masonry heaters and found this "vintage" reference to such a heater that was apparently designed by Peter?

https://www.mha-net.org/docs/temp/100206vandenberg.htm


Curious if it was ever built, and if so, how did it work?

<grin>Yes, it has been built, once or maybe twice.<grin off>
It'd work, burning quite clean, the bell system stayed warm for about 24 hours. Years of meddling with fire led to this design.
Far too complicated when viewed with today's level of knowledge in mind, the batch box rocket system a couple of years later did about the same in a far less complicated manner.

When I saw the date, I thought that might have been the case. Especially in light of some of the newer simple open bell designs I'm finding.

Reason for asking, about 6 years ago, we moved out of town to a house that was built with a pre-fab heatilator type fireplace. Nice to look at but only useful for disposing of massive quantities of firewood, while sending all heat up the chimney.

Looked into replacing it with a masonry heater and even went so far as to contract and trade correspondence with Alex Chernov. He gave me a lot of good ideas, except for the part about finding someone to build it.  But compared to some of the latest I'm seeing, even his designs were pretty complicated and expensive, as are most of the mha designs and builds I've seen.

The latest designs with batch boxes and single or double bells look to be both simpler to build and less expensive and maybe even as good or better when it comes to harvesting heat. If so, I may start warming to the idea of finding help with a design and build.

For educational purposes, lets play a little game called "fix this fireplace". What could have been, or perhaps what still could be.

Setup is this is what came with house I live in now. It pretty much is exactly what it appears to be. A UL approved heatilator type fireplace centered in a wall unit. That backs up to an exterior wall. It all sits on a cement slab floor, with back further supported by deep footing. Face of fireplace is 30 inches from back wall. the center unit is 6 feet wide and from floor to the transition above fireplace is 8 feet. Raised hearth is 1 foot off the floor, and about 16 inches from front edge to base of fireplace. Floor in front is wood flooring over cement slab, so can be removed in favor of tile or other floor covering if an extended hearth is needed.

Side benches solid brick. Appears cabinets with book cases sits on these elevated benches. Those need to remain intact if possible.

So I'm thinking a type of masonry heater. Batch box with single or double bell. Have not cracked the build open to see arrangement of flue pipe, but assume it is a double wall insulated flue pipe that runs thru the interior chase (outside wall flush), to an elevated chimney chase / flue top. The chimney now and in the future would run inside heated envelop of building.

What are the options???

Might be space enough for a 6" or 7" sidewinder batchrocket, perhaps even larger. For this, the whole of the hearth and probably part of the chase need to be taken down. The benches could stay, but during the build the book cases would be best removed to be replaced later.

My assumption was the cabinets and book cases on both sides would removed during build. All are prefab, and are just sitting there.  Everything in middle below "Home" wiped clean. Heater built in empty space in the middle, and connected back to chase behind "Home".

If cabinets and book cases replaced, how does that affect space to combustibles (the cabinets and book cases)? An air gap left? Or is the heat of the bells reduced enough they can touch as they do now? Same with clearance to back wall.

My understanding is a masonry heater wall should not physically touch any exterior wall. At min, it needs a small air gap, reflective insulation, or both. Not much radiant heat into room from back side, but at least not conducting heat to exterior wall, and air gap may offer a small bit of convection into the room. Ideally it ought to be built in an interior location, away from any exterior walls like a wood stove, as many sides exposed as possible so as to maximize radiant heat distribution. So bad location to start with, but is what it is. Goal is to make the best of it and minimize heat loss to exterior.

Has anyone ever stacked bells vertically? This could have two.........a lower hot one and an upper cooler one? Split line about where the top of existing fireplace mantle is?

BTW, failed to mention. Room is roughly 320 square feet, adjacent and open to an additional 300 square feet offset to one side.

This is the busiest room in the house, but it has it's share of flow problems. Was once told the top of that fireplace mantle was the only place in the room where you could put a TV, and it works OK there. Can that be retained while this functions as  a masonry heater? Perhaps on a wood or stone mantle shelf? Top bell smaller than the bottom so there is an offset shelf created?

Since most of the area for radiant heat is to the front, it occurs to me that one way to enhance the radiant surface is to alter the front face surface. Rather than brick, perhaps a face of thin shale type rocks, with thin edges projecting an inch or so away from mortar surface?

Have been doing some light sketches, and depending on design of sides and back required for distance to combustibles.......those cabinets, shelves and back walls, an 8" riser is going to be enough to match up to internal surface area (ISA). For now, looks to be a single bell.

Have been pouring over Peter's website summary on RMH, and have a few questions.

First, is there a known, proven material from which castings of the batch box and riser can be made? One that will hold up to the heat, long term, if not indefinitely? If not, what material has proved to hold up the best? Reason for asking, once this is built in and enclosed, it is built in and enclosed. No way to inspect so need to make it as permanent, durable and bomb proof as possible.

On castings, has anyone considered making and selling molds? Peter describes a case where builders would be making them as a "one of", with each finding his own way. Perhaps an option for some enterprising kind of person is to setup to make these molds to sell out of pourable expanding foam? A 2 pound or even 4 pound foam ought to be more than tough enough for this. This would works like any other casting, where a pattern of the finished part you want is made, then mold made around it. Remove the pattern, then fill cavity with pourable expanding foam. End result is an exact duplicate of your pattern. Unlimited supply of molds to ship to various destinations to duplicate the pattern from your casting material.

Has anyone looked into using vacuum bags instead of a vibrating table?

For a P channel, anyone considered using schedule 40 cast iron pipe? Use fittings and screw it together vs. welding?

Yes there had been cast J tube fireboxes for sale in the past, I dont know if they still operate.
(Dragon Heaters I thing)
There are issues with molding refractory components, ideally they would need to be made from several interlocking components that allow for uneven expansion.
This type of mold is both difficult to design and difficult to cast accuracy without any flaws.
However, nowadays with 3D printing it could be done but, it would  still require considerable investment in a tiny niche market that is unlike to ever sell many.
Good quality bricks are the best readily available material to build with, they might not offer the best start up speed and will take some time to get up to temperature, but they are the tried and tested to last a very long time.
A stove built from insulating material like ceramic fibre board, will jump into life very quickly and draw well from the start. The same stove built from fire brick and insulated from the back, with first have to first heat through the brick before it starts to work at full performance.
So people often compromise by building a strong, abrasion resident fire box and an insulated riser but nothing last forever and you will definitely need access to bell for cleaning out fly ash.

To be clear, I wasn't talking about shipping cast cores. Only foam molds from which the end user could cast his own. But at this point in time, I would remain skeptical as to longevity of cast boxes or risers....at least till we find otherwise.

So if a large single bell was to be built into that wall, and fly ash is going to build up on floor of the bell over time, it seems like it would need one or more clean out access doors at base along the front. Perhaps even one on either side of the batch box?

What would work / be available for these clean outs, since what lies behind them would be still warm and active flue gases? Not when cleaning out, but when heater is in operation. Doors would have to be able to seal up 100%. Is there an off the shelf commercial option?  Perhaps a round, cast iron pipe or drain fitting, with cast iron screw in plug? Those might go as large as 6 to 8 inches?

Also, to maximize front face radiant area, my first thought was to allow an offset in a back corner of the bell for a stove pipe riser. So giving that some more thought, also seems a clean out of some sort would be needed at the base of the stove pipe? But how to do that with it buried in the wall behind the bell?

Perhaps that can be accessed from one of the other front clean out doors?

Eugene Howard wrote:To be clear, I wasn't talking about shipping cast cores. Only foam molds from which the end user could cast his own. But at this point in time, I would remain skeptical as to longevity of cast boxes or risers....at least till we find otherwise.

So if a large single bell was to be built into that wall, and fly ash is going to build up on floor of the bell over time, it seems like it would need one or more clean out access doors at base along the front. Perhaps even one on either side of the batch box?

What would work / be available for these clean outs, since what lies behind them would be still warm and active flue gases? Not when cleaning out, but when heater is in operation. Doors would have to be able to seal up 100%. Is there an off the shelf commercial option?  Perhaps a round, cast iron pipe or drain fitting, with cast iron screw in plug? Those might go as large as 6 to 8 inches?

Also, to maximize front face radiant area, my first thought was to allow an offset in a back corner of the bell for a stove pipe riser. So giving that some more thought, also seems a clean out of some sort would be needed at the base of the stove pipe? But how to do that with it buried in the wall behind the bell?

Perhaps that can be accessed from one of the other front clean out doors?

1) Doing a mold for the casting is not so hard, as you would created exactly what the inner "batch box" would look like, with Foam,  and of course the exterior shape you desire, with the casting between the two.  The problem, is just where you want "to guess" the crack from expansion would take place. As more and more get done, if this is shared, then it could be developed into a fairly good estimated  way to do it"  This generally takes good communication, and a common denominator of design. Both are a tough go, with so few attempting.

2)With a large bell, locating a clean out door, that can have a insulated board, can work well. Please note: at the bottom of the bell, the temps are no where near as just above the riser. This clean out door should have NO issues with spalling from heat.

3) I think your making the clean out door harder than it needs to be, There are lots of ceramic gasket strips, Just to name one. If this area is going to be under 500 degrees (and it will/should) be. A once a year silicon gasket should work, the good stuff can really handle up to pretty warm temps.

4) are you thinking the bell would be built into the wall or like Peter's?  With Peters in mind, so many things are solved.  A rectangle bell, with radiation to the room heat dynamic.

Best of success.

The original idea  / concept was to take the central part of the existing build, with wood burning, wood wasting heatilator type fireplace and wipe the central part clean. Everything in the photo below "Home". My original though was to replace it with a masonry heater. As I'm learning about the simplicity and effectiveness of a RMH combined with a single bell, that looks like the way to go.

Dimensions are 30 inches deep......could be 36 inches..........and the front is 6 feet wide and from raised hearth to top of that segment, 7 feet. So opening to work with is 36"D x 72"W x 84"H.

The existing flue is contained in existing chase behind "Home". From there to chimney cap on roof is maybe 12 feet and all of existing flue is retained inside building envelop until it emerges at chimney top / cap.

Eugene Howard wrote:The original idea  / concept was to take the central part of the existing build, with wood burning, wood wasting heatilator type fireplace and wipe the central part clean. Everything in the photo below "Home". My original though was to replace it with a masonry heater. As I'm learning about the simplicity and effectiveness of a RMH combined with a single bell, that looks like the way to go.

Dimensions are 30 inches deep......could be 36 inches..........and the front is 6 feet wide and from raised hearth to top of that segment, 7 feet. So opening to work with is 36"D x 72"W x 84"H.

The existing flue is contained in existing chase behind "Home". From there to chimney cap on roof is maybe 12 feet and all of existing flue is retained inside building envelop until it emerges at chimney top / cap.

I took your dimensions given above and then laid out as 4.5" wide bricks to calculate just what  you would have for internal square feet of the 4 sides and top. this came to 111 sq feet so far larger than anything you would need.  There are far smarter folks than I that might be able to suggest on how to ultilize your mass, where the rear wall of the mass would not be in the room per say.  I have not read any case where it would not be free standing, I suspect there has been some.

There is so much to gain, so work out your plan,   but the best thing you know so far, is that it would appear that you do not have an area constraint.