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Could a bell be in the shape of steps?

 
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My brother-in-law had an idea for making a rocket mass heater with a set of brick steps as the bell, to help melt snow and ice on the entryway.

My first thought was... that is a great idea!

My second thought was... is it possible to build a working bell in the shape of steps?

This could be a game changer in my climate if it worked. Being able to light a fire to melt off the ice, or even prevent it from building up during a storm would be awesome.

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thomas rubino
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Short answer, Yes, they can be a stair-shape.
For the life of me...
I can not figure out how you would implement such a thing for snow melting.

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Well... in my very limited experience... I would construct either a J-Tube or Batch box attached to a hollow set of brick steps to use as the bell? Then have a chimney coming out the bottom step? And set the whole thing in front of my door?

Ok fine... maybe build it in place, as it WOULD be heavy to move :)

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thomas rubino
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Well, you guys certainly get an A for thinking outside the box!
I guess with a tall first-floor entry or a low second-story entry you could accomplish this...
I'll leave the details up to you.

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I see Matt Walker's bell bench, which only looks a couple feet high. So I don't think height would be a problem?

"The future is something which everyone reaches at the rate of sixty minutes an hour, whatever he does, whoever he is." C.S. Lewis
"When the whole world is running towards a cliff, he who is running in the opposite direction appears to have lost his mind." C.S. Lewis

 
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For building a set of hollow stairs, you might check out Guastavino or Catalan vaulting.  The load bearing material is the structural tile.  For your purposes, you might need higher temperature rated mortar than what is customarily used for tile vaulting.  But, it might allow for additional design freedom.  I have a bunch of printed resources, and some digital regarding the method.  Some are in English, and some in Spanish.  I don't really read Spanish, but the vocabulary is fairly restricted, and there are good photos and/or sketches, so that all helps.  This technique was once widely used in areas with a Spanish cultural heritage, and for many prominent public buildings in the US, including several very large domes.  The Guastavino Company couldn't compete with cheaper, lower labor construction methods, and eventually closed some time in the 1960s, if I recall correctly.  There is nothing inherently wrong with the method, it is just high labor,and skilled labor at that, which ended up being too costly to compete with formed reinforced concrete.

Catalan tile could be used to make flat roofs with enough strength to support rooftop gardens, or to create a vaulted courtyard over a rain cistern, or to create permanent form work for bridges or tunnels.  Or, a giant economy wine cellar.  Or, an Oehler structure in a location where timber is in short supply.

Most of the modern revival in Guastavino vaulting has gone through John Ochsendorf's group at MIT.  An exception to this may be Anne Fitchett at University of Witwatersrand in South Africa, who designed the tiles for the vaults at the Mapungubwe National Park visitor's center.  I briefly corresponded with her regarding the presses they used to site manufacture the tiles - basically, a version of the venerable Cinva ram, but with hardboard separator plates, so that they could press three tiles in one go.  I don't remember if she has connections with Ochsendorf.

I'm not sure that structural tie is what you need, but I do think it's worth considering.

There are videos on YouTube showing Spanish masons building stairs in structural tile.  It's amazing to watch someone who knows what they are doing construct a stairway free hand without form work, just some guide lines or steel ribbons to form the plaster springing along a wall.
 
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Hey guys,
niche but very cool idea.
Would it actually have to be stair shaped though? Triangular or maybe even just rectangular would also work probably and then put steps on top and let heat transfer take care of the more complicated shapes? It wouldn't need to get very hot either.

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Benjamin Dinkel wrote:Hey guys,
niche but very cool idea.
Would it actually have to be stair shaped though? Triangular or maybe even just rectangular would also work probably and then put steps on top and let heat transfer take care of the more complicated shapes? It wouldn't need to get very hot either.



Well actually the hope was it would be a pretty hot idea.., :)

But I like the idea of having the inside be a more easily built shape, and letting heat transfer take it the rest of the way. I hear of people's benches getting to 90f-150f on the outside (both kind, mass and bell), but with this being outside, I don't expect those temps... or at least not for long. Still... it only takes 33f to melt stuff.

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So here is a question then... can I use metal supports in the bell area? Some steel or angle iron or something simple to hold the structure of bricks? I know you could not use that in the burn chamber for long... but would the bell be cool enough to handle metal supports?

Otherwise, I'm assuming I would need to build some sort of pillars out of brick, inside the structure to support the weight.

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My first thought is that wouldn't the heat just go up to the top step and leave the lower ones cooler?

And if so, would that matter?

Or is there a way to design the air flow inside so that it would heat more evenly?

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Please keep in mind that I have read a lot of posts and watched a lot of videos on Rocket Mass Heaters... but never with the intention of building one. And that is simply because I have nowhere to put one right now. I plan to build one eventually. So I have large gaps in my knowledge.

My understanding of the bells is that the hot exhaust is put into the top of the bell bench, and the top would certainly get the hottest. Then the cooler exhaust is taken out at a lower point. So the lower points would get some heat from the exiting air, and also through thermal transfer from the top bricks/mass.

Having said that... perhaps we only need part of the steps hollow to absorb the heat? Please forgive my terrible artistic skills, but hopefully you understand what I'm talking about. I was originally thinking the whole thing empty... but your comment made me wonder if I keep the top two steps solid to absorb more heat.
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In principle, I think that idea would work. I think it would be a hybrid, with the bell cavity a bit higher under the top steps, and a thicker ceiling over it there, to even out the heat transfer. Experimentation would be needed to get the right balance there.
 
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Playing devil's advocate.

You run the fire to melt a bunch of snow. Evening comes, snow falls, it's just warm enough to melt it as it settles but then refreezes.

Haven't you just made a lethal set of ice steps, with ice frozen to the surface that is going to be difficult to remove?

With cold steps, don't you just shovel the loose freshly fallen snow off?

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Glenn Herbert wrote:In principle, I think that idea would work. I think it would be a hybrid, with the bell cavity a bit higher under the top steps, and a thicker ceiling over it there, to even out the heat transfer. Experimentation would be needed to get the right balance there.



I was attempting to portray two solid steps at the top, with a hollow bell in the bottom two steps.

You are suggesting that I might want to put the bell closer to the top? Perhaps have the bottom three make up the bell and only the top step be solid?

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Michael Cox wrote:Playing devil's advocate.

You run the fire to melt a bunch of snow. Evening comes, snow falls, it's just warm enough to melt it as it settles but then refreezes.

Haven't you just made a lethal set of ice steps, with ice frozen to the surface that is going to be difficult to remove?

With cold steps, don't you just shovel the loose freshly fallen snow off?



I think you could time the heat based on the storm. I would like to think 1 firing would melt one storm's worth of snow. And we do not oftenget two storms back to back. Generally we get snow/ice dumped on us and then a break. If we did get two storms, we could just fire it again. I am imagining firing it up just before the storm starts... to avoid snow build up. Or just after, as a fun way to melt the snow instead of shoveling.

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"When the whole world is running towards a cliff, he who is running in the opposite direction appears to have lost his mind." C.S. Lewis

 
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The "Icy Death Trap of Death" (from the Department of Redundancy Department!) could eventuate, but proper use of the system should actually improve safety.

I live in a pretty snow climate, and a few profligates (including a friend of mine - he and his wife are in their 80s, so I am willing to give them some grace on this) have heated driveways or sidewalks.  It's quite common for municipal buildings, senior citizen housing, houses of worship and the like to have heated sidewalks and driveways in these parts.  This is done in the interest of safety - less chance of slip and fall accidents (and ensuing lawsuits in our litigious society here in the good old US of A).

Usually, there are PEX lines buried under the heated sidewalks and driveways.  A thermocouple measures the temperature of the surface (well, the thermocouples are actually installed sub-surface) and cycles the heat on when it falls to freezing.  There is usually a manual control switch also, with the system only enabled "as needed".  There can be multiple heating loops, depending on the installation.  The fluid circulated through the tubing is some sort of water/glycol mix, so inadvertent freezing temperatures (i.e. didn't turn on the heater) won't burst the lines.  Don't forget that there can be significant evaporation and sublimation when atmospheric humidity is low, even if temperatures are quite cold.  In very humid climates, these effects will be less pronounced.

If snow (or freezing rain) is episodic in your neck of the woods, then the heated steps you've proposed is probably fairly easy to manage manually - fire the rocket heater when snow or freezing rain is predicted, and let it go cold when the weather is dry or will stay above freezing.  Where I live, we can have significant accumulation every day for a month or more running, and anything less than 300" total accumulation is an "easy" winter.  Manual control would be very "hands on" under such circumstances.

 
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While this is not exactly the application you are thinking of, I thought that you all would enjoy this staircase application of a rocket mass heater by the late, great Danish architect/builder Flemming Abrahammson of Fornyet Energi:



For a full design review of staircases integrated with masonry heaters, check out:
https://www.firespeaking.com/masonry-heaters/masonry-heater-staircases/

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So back to a previous question of mine.

Can I use steel or angle iron or similar for structural support in the bell area?

I'm imagining a frame to put the bricks on... so I don't have to build mini brick pillars to hold up the inside.

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Yes, you can.
If it is in the upper portion above the riser, it would need to be wrapped with a ceramic blanket or equivalent.
Otherwise, metal is fine inside a bell.

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You would want some insulation directly over the riser anyway, so there is not a hot spot in that area leaving other parts of the surface colder.
 
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Glenn Herbert wrote:You would want some insulation directly over the riser anyway, so there is not a hot spot in that area leaving other parts of the surface colder.



I'm not totally following this need? I'm only part way through the DVD's on rocket mass heaters, and I know there has been innovation since they were made. I was imagining the riser being separate from the mass... similar to the style in those DVD's. But this means a lot of heat would just be released outside... good for the person starting the fire, but not the best use of the heat either. Would you recommend building it sort of all inclosed where the riser is inside the mass so to speak?

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If the primary purpose is snow melting, you would absolutely want the riser under the steps/inside the mass. Otherwise you would be wasting a large part of the heat generated, and the quickest snow melting part.
 
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Glenn Herbert wrote:If the primary purpose is snow melting, you would absolutely want the riser under the steps/inside the mass. Otherwise you would be wasting a large part of the heat generated, and the quickest snow melting part.



I don't disagree... but I'm not sure the steps are going to be tall enough. to put the riser inside.

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Depending on the landscape, you could dig down so that the J-tube feed was at ground level, allowing more scope for the riser.If drainage is good, you could even make a "window well" hollow to get the feed area low enough for the riser to fit. You would surely want to partially enclose the feed area to protect it and the wood supply from snowdrifts.
 
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Ahhh, that is a good idea. And I think it might work for this particular place we are thinking. If I drop it down to where the burn tunnel is below ground level (and probably have the feed being at ground level). Then add some insulation and some extra mass on top to help even out the heat. This would let me put the riser inside the steps and keep more heat where I want it. The burn tunnel would actually be coming straight out the side, but I drew it going the other direction.
20241126_090134.jpg
rmh steps
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Up thread, I had mentioned Guastavino or structural tile vaulting as a possible construction method (also known as Catalan vaulting or boveda tabicada).

Here's a video from a Spanish mason, showing how the vault curve is defined and the vault built up.  Note the plaster of paris mortar for the initial inner layer, followed by a Portland-based mortar for subsequent tile layers.  The plaster of paris is what seems to me unlikely to withstand high heat.  Whether the Portland bond to subsequent layer of the layup schedule would suffice to maintain the inner tile layer intact and integral with the rest of the vault, I don't know.  A refractory stove cement might be necessary.

https://youtu.be/iVPH8XAFkzg?t=146

This same mason has lots more instructional videos on Catalan vaulting on his YT channel.  Videos showing how to build spiral vaulted staors are even more impressive, but not germane to the OP's project.

Guastavino Sr. did tests with loads of pig iron or other ballast on top of and built fires beneath sample vaults to demonstrate that the construction method was "fireproof".  The vaults did not collapse, satisfying architects and insurance companies (and providing excellent publicity photos for his burgeoning construction business).  However, spalling of the inner layer of glazed decorative (i.e. "subway" - Guastavino is the reason they are so called) tiles is not unheard of over the long haul, even under very benign environmental conditions.  The attached photo is a static load test (without fire) of a vault, but I am pretty sure there is a photo of a test with fire in John Ochsendorf's book "Guastavino Vaulting: The Art of Structural Tile". Though I may have seen it elsewhere (perhaps in one of Santiago Huerta's papers).  I'll dig out my copy of Ochsendorf and have a look.
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Thanks for everyone's replies. I think we have some good ideas, but unfortunately it has gotten too cold here to work with any kind of mortar outisde (at least according to google, if anyone knows different, please let me know), so we have had to put the project on hold till the spring.

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The attached are scans of a couple of pages from John Ochsendorf's book "Guastavino Vaulting: The Art of Structural Tile", the first discussing the empirical testing which Raphael Guastavino Sr. undertook in 1897 to demonstrate the ability of his vault construction method to withstand fire while bearing loads on the vaults.  As the text explains, these tests were used as justification of the continued structural capabilities of the vaults of the Oyster Bar in New York City's Grand Central Station following the 1997 fire.

Also attached is an illustration of a layup schedule developed under Raphael Guastavino Jr. which encapsulated the plaster of Paris bonded initial layer between subsequent inner and outer layers bonded with Portland cement based mortars.  I'd forgotten about this innovation, but it seems like this might be particularly helpful in situations where the vault is intentionally subjected to repeated thermal cycling, as it would be in a heated stair.

Hopefully this provides some grist for the OP's mill.
Filename: Guastavino_tile_lamination__Ochsendorf.pdf
File size: 1 megabytes
Filename: Guastavino_fire_testing__Ochsendorf.pdf
File size: 1 megabytes
 
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