Rocket stove in a bus/RV

Hi,

I've scoured the Internet looking for someone who's done this before, but it appears that everyone else who's gotten this idea has gone another route (likely for obvious reasons).

Is it possible to construct the burn chamber and riser in a way that won't leave it susceptible to shock and road vibration? My original plan was to construct the entire stove out of steel, however this forum has enlightened me to the inevitable pitfalls of going the YouTube route. The bus doesn't move very often, but when it does, I don't want to be creeping down the road like I'm transporting fine China- I'd rather the stove be over-built if that alleviates the durability issue. If there really isn't a solution for the shock and vibrations on fire brick (or anything else that can handle the heat), can it be constructed in a way that keeps the temperatures down enough to build the burn chamber out of steel without inevitable damage? I realize this wouldn't be a true RMH at that point, but the benefits of a system like that over a traditional wood stove would still make the effort worthwhile.

It's a short bus, so the inside volume doesn't really necessitate much of a mass, I was planning on piping the exhaust down through the floor and out next to the engine exhaust tailpipe, and covering most of the outer barrel (40lb propane tank) with clay to retain some of the heat. Intake pipe would also draw outside air into the chamber to avoid using cabin oxygen. Picture attached below to give a better idea of what I'm roughly looking to do:



Any critique or suggestions are wildly appreciated.

Standard full firebricks are strong enough that I think if you rabbeted the corners so they lock together in a square, they could be durable enough for occasional transport.

They would not be the best insulation, but would probably work well enough with lightweight insulation around their container.

Running the exhaust down and out is not going to work well. You need a real chimney for most use cases; sending the exhaust up next to the barrel would probably be best. The chimney needs to extend above the top of the roof (by several feet ideally) to avoid frequent smokeback inside the vehicle.

Bobby Honays wrote:It's a short bus

Hey buddy im sorry but i got a chuckle out of that one. welcome and i have a design since i am helping my friend put one in his motor home and then another one in my moms camper.

my idea is draw air through the fire wall since the engine in the motor home sits back a bit but it should still be do-able to go through the front fire wall of a short bus and one of the reasons for that is so you dont siphon heat from the cabin and so it can draw tepid to warm air that is around the engine and may not slow the system down as much as pulling unwarmed air from under the bus or cold outside air.

to build the sytem in a movable vehicle disallows adobe, clay or brick. so the research i came up with is using a high temp metal that can handle higher temps like an alloy metal with tungsten, nickel or a high grade stainless steel is the only feasible solution for a build that can handle the road bumps. you can use Kaowool to insulate the riser and a propane tank for the bell and a semi-rig exhaust can be a source of nickel piping in 3-4'' sizes and could work for a half decent higher than carbon steel operating temperatures and if you get a couple of those nickel rig stacks from a truck junk yard for cheap and can use it as a chimney on the out side without drawing too much attention or degrade looks of the bus. you can also get them with heat shields that you can put insulation in to improve the chimneys performance.





since you have a bus, its made to be tough and can handle a small mass bench near the rocket stove without breaking apart. a good suggestion would be to use a oval oblong wash tube about 16'' high and bolt it to the bottom of the bus, run the exhaust through it and then fill it with gravel, sand, or other favorite mass material and then out to the chimney.

my name is F styles and i support this suggestion.

my best suggestion is to just build one and see how it works before you install it. test it and then finalize it.

viable?

Blendi Kraja wrote:viable?

only if you use screen door springs... must be screen door springs.

Glenn Herbert wrote:Standard full firebricks are strong enough that I think if you rabbeted the corners so they lock together in a square, they could be durable enough for occasional transport.

Glenn thats preting interesting using metal braces to keep the brick together... hmmm i would have to see that work to see how rugged it is.

my first love...

Glenn- That's very awesome, and likely the route I'll be pursuing. A bit concerned about it caving in, but hoping that scenario can be avoided/delayed/minimized with proper/generous mortar use. The only issue with a low chimney is a back draft, right? What about using a modified something like this Vent, ported out the side like a dryer? I figured the temperature difference in the bell would keep positive pressure out the exhaust and everything would be peachy... What am I missing?

F- I chuckle every time it comes to mind. Firewall draw is a good idea. The plan is to have this thing mounted in a rear corner, so that run down the length of the bus would likely negate the benefit of warm air from the engine bay in regards to starting to fire... But now you've got me re-thinking my layout. Just ripped up the interior behind the driver seat 2 weeks ago to re-do everything, and the possibilities are endless again. The bus in that pic is by far the nicest side exhaust stack I've ever seen on a bus.. Haven't found any old rig stacks yet, but been on the lookout- if nothing else, that's primo scrap metal. Your gravel bench idea is fantastic, although I'm not sure the added mass heat for occasional seasonal use can beat the year-round storage the bench would alternatively provide. Getting me contemplating thermal masses in between the frame rails down the center now though-- it's a shame to lose so much heat up and out any chimney.

Blendi- I was initially thinking something along those lines, except dampers on the floor instead of the ceiling... I suppose it's possible, and would fix the brick deterioration problem, but the feat of mechanical engineering to pull that off would be way beyond what I'd be will to deal with (i drive like an animal). It'd make sweet research though, for sure. Is that your frame? have you subjected it to much/any shock abuse? I'm really digging the threaded rods to adjust the tension.

If you combined the Bigelow Brook riser construction with Blendi's threaded rods to keep things snug, I think the bricks would last a long time.Wrap the whole combustion zone in Kaowool inside wire mesh and you would have a durable unit that would be as light as practical.

If you have significant space under the bus floor and there are no vulnerable parts too close (plastic, rubber, wires, cables, fuel lines :O ), I could see sinking the core into the floor so the feed is about floor level or a few inches above, and running a duct with mass down the center underfloor. The one difficulty might be that the core would have to be near the centerline. If you can offset it even a foot, you can probably come up with a layout that gives circulation space to one side with seating along the wall, and the barrel not too close to the opposite wall for safety.

I forgot to give John McDoodle the credit for the nickel rig stack idea.

As a former full-time RVer I should point out that those tires on your bus can and will blow out over time, even when parked, and the increased weight of any mass inside will make this more likely to happen with even newer/less worn tires on your rig.

Blowouts like this usually happen in the middle of the night, when you're parked in the darkest corner of the RV park or in the one open slot way off in the back of the truck stop, just as you're drifting off to sleep, and sounds nearly identical to a shotgun blast

Tristan Vitali wrote:I should point out that those tires on your bus can and will blow out

why?

F Styles wrote:

Tristan Vitali wrote:I should point out that those tires on your bus can and will blow out

why?

Age, stress and wear&tear. It happens even if you're stationary due to dry rot and UV damage. If there's air pressure in a tire, it will eventually equalize...sort of a "what goes up must come down" thing. Adding more weight stress due to a temporary mass bench will increase the pressure, making the failure more likely.

At the camp, I have a 5th wheel wrapped with a roundwood timberframe / cordwood infill "shed" and hoop-house style sunroom and installed an 8" RMH in the sunroom, with a huge amount of mass, plus a 4" in the back shed section with a 15 foot long bench. It's definitely not the same as having these babies indoors where you can thoroughly enjoy the benefits, but it keeps the air temps around the rig in the 40s, even on subzero nights here in Maine, saving hugely on the propane necessary to keep the interior around 70. It's also nice to not have to step out into the great white, frigid north in one step. Compromise

This is where I posted some other pictures of the stove https://permies.com/t/51832/rocket-stoves/RMH-Minimum-Footprint#420686. Well, I have transported it a lot back and forth, of course taking care, and no problems. I think, regarding how I did it, you can throw it off a rock and the core inside the frame will survive. But I won't do this to that little nice beast .

Well, about hanging it or fixing it on the floor, IMHO it is better to hang it from the ceiling than fixing it on the floor. Choosing the lesser evil, the shock from the ceiling is lesser than that from the floor, I guess.

Better yet, springs both in the ceiling and in the floor. Employing my internationally-renown no-peer exceptional and beautiful drawing skills, this would result in this:

Tristan Vitali wrote:As a former full-time RVer I should point out that those tires on your bus can and will blow out over time, even when parked, and the increased weight of any mass inside will make this more likely to happen with even newer/less worn tires on your rig.

It is true that more weight adds stress to the tires, however a school bus is built to be loaded full of people... Stripping out the seats and adding back some wood weight for furniture/storage and even a water tank & furnace doesn't add back nearly as much weight as what the bus was originally designed to carry. It's a bit harder to drive now just because the suspension likes to float around from lack of loading. That said, a 3-person bench full of rocks might be more weight than I'm willing to add for the given purpose, although it being across from the fuel tank would get the loading a bit more even than it currently stands.

Avoid retreads, cover the tires when parked, and jack the frame when possible. No tires last forever... But that is definitely something I wasn't considering when thinking about RMHs... was more concerned with fuel economy- but can't get very far with only 5 tires. Good thinking.

Tristan Vitali wrote:

Age, stress and wear&tear. It happens even if you're stationary due to dry rot and UV damage. If there's air pressure in a tire, it will eventually equalize...sort of a "what goes up must come down" thing. Adding more weight stress due to a temporary mass bench will increase the pressure, making the failure more likely.

Tristan maybe you did not know this but there is a better solution than putting air in your tires and for extended use and sitting i would suggest using Nitrogen.

While regular air is bad for tires, compressed air is even worse. Running air through a compressor typically adds trace amounts of oil and particulate, as well as water vapor … all combining to further rust, rot, corrode and otherwise compromise your tire and wheel assemblies.
As troublesome as oxidation, moisture and the resulting damage they cause are, there is a much greater benefit to eliminating oxygen: better pressure retention. The most detrimental property of oxygen is actually its small molecular structure. A molecule of oxygen, which again comprises about 20% of regular air, is roughly 1/4 of the size of a molecule of nitrogen. Oxygen molecules are so small that it is completely normal for air filled tires to lose 1-3 PSI each month from "permeation." Permeation is the normal process by which the oxygen molecules in compressed air seep through a tire's carcass. It is the reason that your, and everyone else's, air filled tires constantly lose 1-3 PSI of air every month. Nitrogen filled tires, on the other hand, typically lose no pressure from permeation… even over many months of use. So, by inflating your tires with high purity nitrogen, they will remain at their proper operating pressure much longer.
source: http://www.nitrofill.com/nitrogen-in-tires.aspx



The second problem of weight must be understood that these buses are rated for very heavy loads and they do it safely. you may not know this but a School bus is one of the safest vehicles on the road or off and has alot to do with its strength and rigidity. The short bus (chuckle) can hold up to 30 people and that does not include seats gas and cargo. its safe to say that a person can easily weigh at least 150lbs x 30 and you have 4500lbs. a small rocket stove with a little tub or bench filled with mass can most certainly be built under 4500 lbs which is far below the rated carrying capacity of a school bus.

I'm aware of using nitrogen gas but, being a frugal kind of guy, by necessity, and never finding the option for free at gas station during my travels, it's never been a viable option Too often, you get what you pay for, and when seeking out ways to not have to pay for much, the "beggars can't be choosers" thing comes into play. Hand-in-hand with this would be my propensity to not buy new or top-of-the-line tires, leaving me and others like me more prone to defects in manufacturing, sidewall damage from previous abuse on used tires, etc.

By all means, as noted by a few, a bus is a very different beast than, say, a 1980s 5th wheel camper bought off an out of work repo guy for a grand. The tires are even of a different caliber, made and rated for such higher capacity (my rig takes the same tire we put on the little honda junker). On the other hand, physics are physics and that's what I was pointing to with my comment about tire blow-outs and upping the potential for such to occur. I know I couldn't get away with putting a heavy mass in my rig - not only the potential (probable) issues with blow-outs but I'm situated on a fairly soft clay soil with a high water table...can only imagine how deep this baby would sink with just one ton of mass added, never mind 4 or 5 tons! This situation (floating a rig on a marginally stable surface like a fool) is likely not a situation that Bobby would be looking at dealing with - hope he's not as foolish as I am! And as stated, a bus is built for higher loading capacity than a lightweight camper-trailer, but the added weight and its affect on tire life (along with the potential for blowouts due to the added weight) is definitely something he should keep in mind...it'd be a good reason to keep an additional spare on hand, just in case.

inflation adjusted 2 cents is all