Andrew Smart

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since Sep 02, 2018
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Recent posts by Andrew Smart

I keep thinking of when I disassembled a chimney and moved the clay fire bricks around in a metal wheelbarrow, stacked 2-3 high mostly organized/level. Maybe 5-6 of the bricks had fractured in transit over 8 or so loads. I guess clay slip between the bricks and having the bricks laying a bed of vermiculite instead of metal would help a lot. So maybe a metal frame not necessary... I guess experiments needed to see failure points (like this video claiming weight of stuff on bricks caused some bricks to break).

thomas rubino wrote:The gravel filled bench has been used successfully but it is not the best of choice's.

Page 214-218 I agree that the box and fill system seems best to allow nomadic folks to more easily transport the heater. New fill being added at each location to avoid the cost of transporting the heavy mass.

Can be filled on site with a sifter and shovel (a few hours and you'll have a lot of gravel... frozen ground may make things really tough without pickaxe):

And I agree, gravel seems worse absorbing the heat (page 86). I wonder if you could make a hybrid gravel/water bench, use liner like you'd see in a aquaponic/hydroponic bed, which they also coincidentally fill with gravel:

Water seems to have the best heat storage... best to have backup system to mitigate freeze problem though or some passive drain inspired by bell siphon as hydroponics folks use but driven by a phase-transition spring valve.

pH adjustment to minimize aluminum corrosion (7.0-8.5 seems fine). Seal the ducts with silicone, have them enter/exit above the bed to not deal with perforating the box sides.

I am concerned both at cost and the longevity of liners in years especially at higher temperature (near 100C), so I am interested in investigating this Pond Coat: Seamless Brush Grade product. Seems promising though I hesitate after seeing in forums skepticism of similar black rubber products not lasting more than a few years in their outdoor ponds (could be sunlight deterioration in those cases, not sure).

thomas rubino wrote:Have you considered a half barrel system? They work very well and weight might be less than a gravel bench.

I didn't see anything to convince me that a half barrel bench (stratification chamber) would be optimal. I see how that is intuitive though, a stratification chamber bench may help with sending the coldest exhaust out the floor through internal turbulence/convection somehow perhaps having more heat transferred to the mass than ducts (more metal surface/mass would release heat into the pebbles over time? like a copper bottomed pot?). But the problem remains that there is less bench mass/volume, and space is at a premium in van/rv (trading space to have more efficient heat transfer to pebbles, but you have less pebbles/mass). Plus I'd have to cut barrels in half and haul them around instead of just dumping gravel. But could be optimal for someone who chose to routinely drive around with this mass during winter instead of mostly staying put adjacent to their gathered firewood as I'd expect.

thomas rubino wrote:Any wood under a core unit is in danger of pyrolysis. The safest way to have a wood floor under a rmh is to raise the whole core unit up with flat bricks and cement board, then clay / perlite on that.

I see some more details page 216 of RMH book. Duraboard looks promising.

thomas rubino wrote:Your idea of the under floor vent sounds like it might be problomatical. Could work great , might work most of the time ... or might be a big pita to get drawing....  

Reading this thread on cooling the feed tube makes me think it will work out. I quote:

Konstantin Kirsch wrote:A RMH has minimum 2 pumps: First the heat riser pumpes the hot air up. Second the barrel pumpes the air down on heat exchange over the surface.

If you do have a vertical chimney than you have a third pump.

At my RMH I got the problem that the feed tube got very hot in time. After some hours of use the temperature rises up to 900 °F. A new wooden stick starts to burn on all sides and on the total length immediately after putting it into the feed tube. Than smoke comes into the room...

Now I added a fourth pump at my RMH: On cooling the feed tube the wood is only burning sideways at the bottom. There is no draft upways in the feed tube any more. There is no more smoke coming into the room. There is no probem anymore on closing the door quickly and there we got hot water!

I took the feed tube out of steel and added a thick plate out of steel to it

Than I put a put with cold water on top. he feed tube getts now cooled by the water and the water gets hotter.

I see no problem in my design as long as the heat riser is primed, firebox is cooled, and bench not too long/resistive. As there is no vertical chimney there will be no third pump to fall back on as redundancy, it would be critical to have the first two and fourth pumps optimally designed and within operating conditions (riser primed, firebox cool).

Filling the pebble bed would be done with snow melt in this pot, melted in the process of cooling the feed tube to maximize the draft of first j-tube thermosiphon. Note he says his pot of water isn't enough mass and he said he wanted to look into an active heat pump to keep it cool; I think an overhead water tank best solution as a passive thermosiphon, easy hot shower for example, recharged by snow/rain? I quote:

Konstantin Kirsch wrote: but the waterpot has not enough water in it. I produce much more boiling water than needed. In the time the feed tube gets too hot even I cool it with this system. So I found that the cooling of the feed tube is very importand. I'm realy thinking of making an aktive water cooling system direct around the feed tube.

As Paul Wheaton says in this podcast if there isn't much mass in the riser (just ceramic wool instead of brick), it might not retain enough warmth from the last firing and may need to be primed anyway.

Page 247 'Thermosiphons and Chimneys':

A J-shaped thermosiphon (such as our firebox) operates in a similar way as the reverse-J water siphon. The short leg is near the source of fuel and air. The flames follow the longer leg upward, creating a strong draft. [...] In addition to a difference in height and the absence of leaks, a thermosiphon also requires a consistent temperature or difference in temperatures. If the short leg became much hotter than the long one, the thermosiphon could stop working or even flow backwards.

Page 248 has some chimney draft math as well.

Advantage of this system, not having that third thermosiphon (vertical chimney) is not having that heat loss from the mass through the day that Paul Wheaton talks about often where he advocates the horizontal outlet instead of vertical chimney (not sure what present status of that debate is...).

In the podcast it seems of the 3 shippable core designs: Erica's design using "goo" is a clear winner for portability, low weight, and low cost, and Paul Wheaton says they may release that design in the future. Ok, I see it didn't last and had crumbled and they settled on Paul's wood box design.
1 year ago

Joshua Hozjan wrote:p.s. My living space (contains all the things) is 6ft high, 6ft wide, 12ft long.  So I am pretty sure a RMH/S would be plenty and multipurpose-able.. I think?

I'd been looking at this possibility as well. I wouldn't move the van much though from it's winter residence, and use different transport. I guess I'm not into the stealth aspect so much.

Joshua Hozjan wrote:3. [...] Is the RMHS something I can contain in just a metal frame with say - the a ceramic fiber isolation method for the raiser to keep the weight down.  

As others wrote the ceramic blanket riser would work well. Tim Robertson used a thin cloth dipped in refractory or furnace cement instead of metal to hold the riser shape.

Joshua Hozjan wrote:4. Driving/bumps/vibrations.  My suspension is pretty rad, but I fear for something like the RMH because most builds are brick/mortor/cod and with enough vibrations they will definitely shift and crack apart..  Is there a way I could avoid brick/mortor/cod entirely and use almost entirely ceramic fiber isolation and I guess steel/SS to keep it in place?  I can weld and have a welder available.  So something like a steel/SS box frame to weld all the pieces together and onto the frame.  J firebox tube + raiser + manifold + chimney secured with welding or whatever works.

One the firebox yes this is my concern too, especially if driving on a rough dirt road, that the bricks may crack if they're allowed to bounce at all. I also guess a steel/aluminum frame would help (video).

For insulating below the firebox I'm not sure. I guess with enough distance any wood won't char, if you decide to use wood floor beneath or near.

For the bench I was planning on a wood box filled with gravel, page 58 of the RMH builder's guide has a bit of spacing between the firebox and the wood box I plan to do, so they can be more easily disconnected and removed during summer.

I'm also thinking of trying a horizontal chimney (page 205), but with the outlet pointing down drilled through the van floor, behind the rear axle. Behind the rear axle so that a skirt can be put around everywhere else, and air flow beneath vehicle will pull. Problem is if it gets snowed in I suppose.
1 year ago
Black coffee reduces the incidence of tooth caries [1].

The results showed that coffee most consumed was roasted coffee, and the frequency on an average was about three cups per day, for an average period of 35 years. The Decayed/Missing/Filled Surface (DMFS) scores varied from 2.9, in subjects who drank black coffee, to 5.5 in subjects who consumed coffee together with sweeteners and creaming agents. The DMFS score was 3.4 in subjects who consumed coffee together with milk but no sugar. The DMFS score of the control subjects was 4, indicating that coffee if consumed alone had anticaries action, but in the presence of additives the antibacterial and anticaries action was totally minimized.

As it says above, adding sugar makes drinking coffee increase the incidence of caries. Even though coffee is acidic, reasons it reduces tooth caries incidence include antioxidant content:

Maximum antioxidant activity was observed for the medium-roasted coffee; the dark coffee had a lower antioxidant activity...

And more reasons it reduces caries incidence [2]:

Furthermore, in the present review coffee was found to be another effective biofilm “killer.” This can be attributed to its enhanced anti-adhesive and anti-biofilm properties

Also, do not use isomalt or sorbitol artificial sweeteners as they promote caries just like sugar does (I'd encourage caution with other "sugar-free" sweeteners as well) [3].

Plenty of other diet/procedure advice elsewhere for improving tooth health. But I thought it very important to point this out about black coffee!

“Black coffee must be strong and very hot; if strong coffee does not agree with you, do not drink black coffee. And if you do not drink black coffee, do not drink any coffee at all.” ~ André Simon


Make sure you're consuming enough calcium daily. Calcium is excreted in your saliva by your salivary glands. If your body is low on calcium... it is allocated instead to essential things like your heart beating, and your teeth when demineralized by acids aren't being mineralized again by saliva!

I don't know if I have a reference for the above calcium claims... in my bookmarks somewhere.


A brief writeup on the chemistry of teeth I highly recommend [4]. A brief synopsis of [4]:

There is a concept known as critical pH, and when pH levels in the mouth become too acid and go below this critical pH, then the tooth enamel starts to demineralize (ie, dissolve away). But when the pH is above the critical pH (more alkaline), then the then the tooth enamel starts to remineralize (ie, the enamel surface rebuilds and thickens itself from the minerals found in the saliva).

Hydroxylapetite has a critical pH of 5.5 - Your natural enamel, dentin, cementum (tooth root).
Chlorapatite has a critical pH of ~5.0? - Chloride treated enamel.
Fluorapatite has a critical pH of 4.5 - Fluoride treated enamel.
Saliva pH in a healthy person is between 7.1 and 7.5. It acts as a buffer helping neutralizing acidic things.
Bacteria consume carbohydrates and produce lactic acid (pH 2.4) as a byproduct, this is the principal cause of cavities, not the bacteria per se, but the lactic acid demineralizing your teeth.
Orange juice is above lactic acid with pH ~3.3.
Lemon juice is below that at a pH of 2.
Coffee brews vary between pH 4.3 - 4.6.
Tomato puree varies between 4.3 - 4.5.
Water dilutes things, bringing them closer to a pH of 7.

As you age your saliva production goes down (xerostomia). With insufficient saliva, your risk of caries increases quite a bit.

Make sure to lightly brush your teeth with soft (not hard/medium!) bristles before consuming breakfast, and before bed so that fluoride is available to replace the OH- ion lost if acid attacks the tooth (forming fluorapatite). You see, brushing your teeth by itself doesn't necessarily form fluorapatite, there must be an acid to remove the OH- ion from the tooth (e.g. overnight as bacteria produce lactic acid). So never rinse your mouth with water after brushing your teeth, just spit it out, and consider leaving it in your mouth for a few minutes, especially if you're currently experiencing decay!

The idea behind fluoride acidic mouthwashes is that they remove the OH- ion themselves and add the fluoride to make fluorapatite within those 30 seconds you swish. Never use said mouthwash longer than the directions say, they are very acidic and would make your teeth soft/demineralized (less healthy) overall. I don't recommend any of the off-the-shelf mouthwashes by the way [5], fluoride toothpaste is all you need, and a DIY rinse [6], rinse with this immediately following acidic or highly sugary meals/snacks.

Also... if you're against using fluoride products, consider using the fluoride toothpaste in the morning and the non-fluoride toothpaste at night? Never drink any soda if you refuse fluoride toothpaste. This video may help set your mind at ease on fluoride in toothpaste, though I do concede that even without swallowing it, some fluoride may permeate the gums and perhaps be unkind to organs. But I think the benefit exceeds the risk in this context (certainly in fluoridation of municipal water the risks outweigh any benefit). Fluoride in this context refers to either potassium fluoride or sodium fluoride, and fluorine refers to the element.


Lots of interesting information in this forum (e.g. clarity on arresting decay). One more thing I will say is, if you do go to a dentist, don't go to a "drill and fill" dentist who will drill out every sign of demineralization he sees (millionaire who characteristically blames you for a big $$$ bill for not flossing, not coming in only every 6 months or whatever). Find a drill-free dentist which practices minimally invasive dentistry, who adopts a "wait-and-see" approach if minor decay can be resolved with better oral care after instruction. There are compounds which have been out many decades which dissolve only the demineralized tooth matter unlike drills which take out surrounding healthy tissue; drills are a thing of the past (unless you're looking forward to being 1-2mm closer to a $1k+ root canal like Mr. Drill-and-fill is). Also never get dental implants (titanium screw) it seems every dentist and their dog is trying to sell for $$$ after seeing all those dollar signs... bring up bad examples that happened in the past and characteristically they'll say "oh it's so much better now!"... it's not, they're bad for your long term health, and harm outweighs benefit. God forbid they also try to sell you sinus lift procedures with crap pseudo bone they think is just fine for you! If you doubt my claims on dental implants, read through negligence/malpractice cases for a reality check.

I have more research to do and share about off the grid tooth care, but don't have the time to write it up for the next few months. I'm putting together a DIY procedure for making bio-mimetic enamel (literally fill in holes). It's not that hard, you'd just need a mg scale, a thermoplastic vacuum frame (can DIY one), alginate (seaweed extract), plaster of paris, PETG thermoplastic sheet, beeswax, four simple chemicals (KH2PO4, CaCl2, NaF, and EDTA), the ability to measure ingredients (can you bake a cake from scratch?), the skill of a grade school artist, and ability to routinely use the tray every night. I'd be building off of a great paper by Chinese authors. They've been trying to accelerate their process with lasers to speed up the crystal growth (with inferior results compared to their laser-free results IMO). I believe their initial work can be done with DIY trays over the course of a ~2-3 months per mm (1 mm is a LOT when you consider enamel is at thickest 2.5mm on the cusp). I have all the equipment and chemicals except the thermoplastic sheet... after I get that I'll do the procedure ex-vivo, and in-vivo, and get some scanning electron microscope imagery of the ex-vivo result, and regular photos of the in-vivo results.
2 years ago
The dental biofilm thesis on this thread is interesting.

A wealth of information in this literature review published in 2015: Natural Antimicrobials and Oral Microorganisms: A Systematic Review on Herbal Interventions for the Eradication of Multispecies Oral Biofilms.

An excerpt:

The data of 14 reports disclosed enhanced antiadhesive and antibiofilm activity by the plant extracts obtained from Vitis vinifera [common grape], Pinus spp. [pine oil, unspecific], Coffea canephora [coffee species], Camellia sinensis [tea species], Vaccinium macrocarpon [cranberry species], Galla chinensis [Chinese sumac], Caesalpinia ferrea Martius [Brazilian ironwood], Psidium cattleianum [Strawberry Guava], representative Brazilian plants and manuka honey. Overall, a positive correlation was revealed between herb-based therapies and elimination rates of all types of multispecies oral biofilms. In that context, integrating or even replacing conventional dental therapy protocols with herbal-inspired treatments can allow effective antimicrobial control of oral biofilms and thus, dental diseases."

I'm not fond of the honey idea... as it would dilute with saliva, with antibiotic effect reduced sufficiently for pathogen to feed off of the sugar. Rinsing with pine oil (turpentine) would work (but specific oil is important, e.g. hardware store stuff probably sulfate turpentine). I wouldn't recommend rinsing with pine oil routinely due to possible undesirable constituents... just for extreme cases (worked for me). Essential oils would diffuse through tissue... hopefully inhibit/clear any abscesses. I'd read in an old book that both urea (e.g. from urine) and potassium iodide had moderate effect on caries as well (it was an old book like this but I can't find exact reference/page again). Potassium iodide is $$$ though... and urea is free and abundant...

I don't have time to read everything, but I'd love to see more research done here.
2 years ago
Hi Jackie,

Jackie Frobese wrote:
1) Does it matter if I get a 55gal or a 30gal barrel? The 30Gal is $150 cheaper not including shipping

On my local classifieds of a rural area of population ~100,000, there are two sellers each selling 1000+ used 55 gallon food grade steel barrels, for $10-13 each ($13 for lid w/ handle). Try local metal scrapyards.

If you're going to spend $100+ on a barrel you may as well buy a cost-effective merchantable good and sell the contents locally.

And as to your question, yes it matters... that should follow from all the other information available to you. But I'm guessing the intent of your question was about cost.

Jackie Frobese wrote:
2) The steel drum is rated for 250F whereas the stainless steel is rated for 600F

Steel can handle far more than 250F and 600F. Look up their melting points, which differ depending on the alloy. I expect they're talking about the paint/lining and not the alloys themselves. I'd seen elsewhere on this forum they burn off the paint then season the exterior drum with an oil, much like seasoning cast iron.
2 years ago