Rocket Stove Questions Answered

I wanted to make a number of upgrades to my rocket stove. Also I got a bunch of questions and comments how I was going to make it better. In this video I go over all these things.
Timestamps:
00:00 Answering Rocket Stove Questions
00:24 Rocket Stove Grate and Secondary Air
02:12 Rocket Stove Metal Frame
03:46 How To Work With Vermiculite Board
04:34 Test Burn With Rocket Stove Enhancements
05:51 Which Enhancements Work Best

[@joeyork9891]

Secondary is necessary you need oxygen during second burn in the riser. Very nice build.

[@BitsOfInterest]

It's true you need oxygen in the heat riser, it's just that I didn't see much difference before and after adding those pipes. Maybe because the front is currently wide open it has enough oxygen. I do plan to make a door so I have more control over the primary and secondary air.

[@250tegra]

@@BitsOfInterest Think you are right about that - if there is enough air (or more than enough) to combust the available 'wood gas' then more air (primary or secondary) will only cool the flame. But . . . which burns more efficiently? My guess would be that the secondary air entering in a properly turbulent fashion at the throat might be more efficient? Better mixing==better burning? Thanks for the excellent Rocket info!😃

[@PeterFletcherDNADeliverer]

Like improvements, great work.

[@adamotoole]

Good work, you can paint the inside of your burn chamber with a slurry mixture of refractory cement and sodium silicate. After the coating is cured and fired it will give a glazed and mechanically tough surface which will protect your vermiculte from abrasive wearing from the sticks

[@BitsOfInterest]

Thanks for the tip! Would you just use a regular 2 inch brush or something for that? Also, do you need multiple coats for it to work, drying times etc? I have never heard of this slurry before :)

[@adamotoole]

@@BitsOfInterest yes a normal paint brush is fine. I can upload a video on my youtube channel so you can see what a difference it makes. One coat is fine

[@adamotoole]

After the first slurry coat cures you can paint on a final coat of sodium silicate and after firing it gets the glassy tough effect

[@BitsOfInterest]

@@adamotoole when searching for sodium silicate I keep seeing "water glass". Am I understanding correctly that the first layer is a mix of refractory cement and "water glass" and the second is just "water glass"? Looks quite adventurous making it though. I don't have a lab at my house, so I'll be mixing caustic substances on an Ikea patio table, lol.

[@adamotoole]

@@BitsOfInterest Yes water glass is the product, but you can also buy it as a product, you don't need to do everything diy style. Not sure what country you are in but you should be able to find it online.

[@tradeamgp]

Espectacular!

[@BitsOfInterest]

Muchas gracias 😀👍

[@lasaramicael3009]

Helow! No se mucho de esto. También hice una, 3 veces, ya. Bvoy a copiar tu modelo. Que es una L abierta. Tu turbulencia es excelente! Aun sin aire secundario ya lograste un fuego de 900° por el color. Y con el aire secundario es casi blanco, así que estarás cerca de los 1.200°! La altura de tu chimenea está bien. Felicitaciones! Has logrado una combustión de 85,90% de la madera! 👏👏👏👏👏👏

[@BitsOfInterest]

Muchas gracias. No hablo español pero tengo Google Translate :) Buena suerte con tu construcción. Tenga cuidado con el tablero de vermiculita, es fácil de dañar.

[@lasaramicael3009]

@@BitsOfInterest gracias. Yo uso barro y ladrillos cocidos rojos.

[@KazeNoTaniFarmHakuba]

Thanks for the update! Watching Little Aussie Rockets it seems like secondary air doesn’t really affect the burn much if you’ve got plenty of primary air. I’d be interested to hear about your experience with secondary air when the primary air entry is restricted by a door

[@BitsOfInterest]

Thanks! I need some more time to think how to make that door. Everything I come up with will be easier to build once I buy a welder, LOL :p I'm probably overcomplicating things (as usual), but I also want to incorporate some glass so I can see what's happening inside and insulate it with some pieces of vermiculite... Edit: maybe things will be easier if I drop the insulation or glue it in after the fact instead of trying to sandwich it in a frame.

[@KazeNoTaniFarmHakuba]

I’m with you. K. I.S.S. Could inexpensive bricks be the exterior support for your burn chamber? You’ve mitred the corners of the boards so any stable exterior support that you like the look of should work just fine.. and I’m beginning to get the feeling that secondary air might be a red herring.. Maybe just ensure that your primary is slightly larger than the choke point into the riser and try to make sure that you have some airflow below your expanded metal bed throughout the burn would be adequate? A glass door would be optimal as the front won’t get ridiculously hot, double pane if you really want to insulate it, but unfortunately I’m not smart enough to work out how to create something like that without welding.. I’ll be looking forward to seeing what you come up with. Remember to enjoy the journey.

[@andrewsolano9172]

@@KazeNoTaniFarmHakuba or expandable metal fit and capped with the angle iron.....just as a protective skin for stove

[@jimfitzgibbon5492]

Hey I would gladly weld anything you need it. You have helped me so much. Have you thought about brushing sodium silicate on the board to stiffen it up.

[@BitsOfInterest]

That's very kind of you. So far I made it work by screwing and glueing things together. I'll get a welder when I come up with a project that really needs it 😜 I did cover the inside of the burn chamber in sodium silicate, seems to work pretty well. I wish I had done that before there was damage because it really soaks into the boards in those spots. Also I wish I paid more attention to the size of the container because when I got the cheapest one on Amazon it turns out it's a tiny 4 oz bottle, just enough for inside the burn chamber 😂

[@annemariekonijn2113]

Carlin is also interested. ☺ He got a warm nose.

[@justtinkering6713]

I have a tip. Put some holes in the riser for secondary air.

[@BitsOfInterest]

You're trying to reach very high temperatures in the bottom of the riser, so pouring in cold air seems to defeat the purpose IMO. You always want to preheat the secondary air one way or another if you are even doing it. If you're not using high temperature insulating materials you probably don't need secondary air because your rocket stove doesn't get hot enough to begin with. Just let enough primary air in in that case.

[@andrewsolano9172]

do you think making a j-tube design would increase efficiency or would it not matter in this build?

[@BitsOfInterest]

For what I know a J-tube is never more efficient, just more convenient to load from the top. A lot of people I see using those designs let long pieces stick out the top and don't have a door. This way you're losing heat and you can't control the air, so I can't imagine it being more efficient in any way. Also it's harder to start because the fire/smoke just wants to come out the fill port.

[@mmikapn]

Youll have to make a serious bottom grid, this one won't last more than 5 or 6 fires. Also my experience is that vermiculite is too soft to handle wood manipulation so i would put eg. Shamote plates inside fire box and vermiculite around for insulation.

[@BitsOfInterest]

It's still holding up, but as I mentioned in the video I'll double the thickness of the expanded metal when it eventually burns out. Indeed the vermiculite can't handle any poking around of sticks, so I bent the sides up to protect it. Some people recommended to apply water glass (sodium silicate) on the vermiculite to toughen it up, so I just ordered some and will give that a try in the near future.

[@250tegra]

@mmikapn - the 'Shamote' plates sound interesting, but cannot find them . . . ? Do you have a link for them please?

[@hansscholte5472]

@@250tegraits spelled ‘chamotte’ and maybe only available in Europe? Firestones used to build ovens like pizzaovens etc

[@david-breitenfeld]

an idea to adding secondary air, is to redesign the box and riser tube so you can fit your metal tube along the right side near the riser tube entry. I think the vortex pressure will draw in the air as the fire swirls around the bottom. The idea is to create a single "smooth" flowing vortex fire. I gave a link to another guys vortex riser tube made out of refractory board, kzbin.info/www/bejne/oZKlfnWoebymg68 When looking at his design you will see the circular area opening, and in that area is where you can place the secondary air tube. His video he shows you how the fire vortex flame behaves and looks like, and it looks like the fire stays more at the bottom. For advanced ideas on fire vortexes, this guy has lots of types and styles kzbin.info/www/bejne/rZC6omeGrL-cbrs

[@BitsOfInterest]

It's explained on batchrocket.eu that a single vortex is not as efficient as a double vortex, so I tried to stay as close as possible to their designs. I'm familiar with the videos you linked. The reason I ended up with this design is because I wanted to use refractory board while keeping it as cheap and easy as possible without welding. I agree that Loz Harrop has an awesome rocket stove and he inspired me to use vermiculite board in the first place :)

[@duhhhh1723]

Thank you for the links and advice 👍

[@bengranchukoff7408]

What about using fire brick? Tougher? Too hard to work?

[@BitsOfInterest]

When I started this project I had no idea if it would work, so I didn't want to spend too much money on it. Fire brick looked like 4-5x the cost at the time, so I went for the cheapest material that would do the job. Coating it in water glass (sodium silicate) helps prevent damage from putting wood in the burn chamber, the metal grate does as well. You can certainly use fire brick but then you're building something more permanent and stationary because you're probably going to make it bigger and use (fire) cement. I can move mine around super easy and don't leave it outside when I'm not using it.

[@peterbeyer5755]

Ceramic fibre board like in Walker Stoves

[@BitsOfInterest]

I decided on vermiculite board after I saw Loz Harrop use it for his new rocket stove core a few years ago. It's easy to work with and for what I saw it looked cheaper than ceramic fiber board.

[@andrewsolano9172]

@@BitsOfInterest i think if i wanted to make this a bit permanent i would use ceramic fiber tiles inside firebox......then again the riser is what gets the hottest not the box so maybe coating inside both box and riser with high heat mortar?

[@BitsOfInterest]

@@andrewsolano9172 ceramic fiber board is probably tougher than vermiculite board so you could use that. Because I already built it out of vermiculite I coated the inside of the firebox in water glass to stop the damage.