Our House

The day before yesterday Wadly and I test fired the sawdust stove out in the yard.  It really does work exactly as acclaimed.  We used fairly damp cedar sawdust (it’s what we had).  I had a little trouble getting it lighted (learning curve) but it burned just fine once it was lit.

Wadly’s planning to burn the paint off so it’s safe to light indoors.

You might want to check this out.  A person commenting on a previous post turned me onto a forum thread about a sawdust stove being used in a wood shop.  Thanks Nancy.

In future I hope to have dry hardwood sawdust to burn.  Keeping us supplied is going to be Wadly’s job.  Right now we have two stove loads of cedar sawdust.  That will do to get us started, but it won’t last beyond a day or two.

Note to self; learn how to braze and find your your anvil.

Raw sheet metal parts.

I took my concept for the bottom workings of the sawdust stove to our local sheet metal shop and they did a brilliant job of turning my concept into solid objects.  All this perfection (not the vent adapter which I got at Goodwill for $5) cost $89.  That’s a heck of a deal, in my mind.  I just don’t have the tools to easily cut and bend metal.

Yesterday I cut the hole for the sleeve/drawer in the 55 gallon drum.  The hole looks great.  It’s a tiny bit smaller than the final, but I’ll leave it as is until I talk to Lorr.  I’m dealing with a barrel that has a fairly good arch in the bottom, so want to have flexibility for which way I jump when putting this all together.

The hole in the sleeve (piece standing on end) has had its edges bent upward to facilitate centering and supporting the burn chamber.

All these bits (not the vent adapter) are to be tack welded Saturday at Lorr’s.  I’ll try and get good pics of the assembly process.

I haven’t cut the exhaust hole yet.  I don’t want to do that until I talk to Lorr.  He may not be okay with using the vent adapter.  Cutting the hole to match the vent adapter reduces my ability to step back and punt.

Wadly brought home a lovely 55 gallon barrel from a vendor on Craigslist.  We haven’t been as successful in finding a 30 gallon drum to use as the inner barrel.  Desiring to forge ahead, I’ve decided to try and use a water heater tank instead.  I’ve got two water heater tanks, one gas which I’ve promised to Ernie Wisner, and one electric which will suit my needs admirably.

I see two benefits and one drawback to using a water heater tank.  Benefit: it’s a smaller diameter which will allow me to consider an insulating sleeve around the outside of the burn tank.  Benefit: the top of the water tank is domed.  Used top down as the burn tank, it will facilitate the removal of ash.  Drawback: the tank is smaller in diameter so will burn for a shorter period of time.

I’ve been pondering the sawdust stove and how/why it works.  When first lit, the sawdust stove emulates a rocket stove.  The burn tank circumference is insulated by the compacted sawdust.  As the sawdust is consumed the stack reduces in height and the room at the top of the burn chamber becomes as a secondary burn area for flue gasses.  I’m dying to know if insulating the burn chamber sides will improve performance.  It is probably totally unnecessary as the sawdust stove is noted for its complete burn of the fuel.

I can’t wait to start experimenting.

It’s going to be a while before I get the sun porch done and we can get our rocket mass heater built.  In the interim, I must have a less expensive (and quieter) way to stay warm.  Toward that end, I’ve been researching sawdust burners.  We can get sawdust free if we shovel it.

The premise of the sawdust burner is to use a low/no cost waste material to supply heat in a stove that can be hand built quickly, easily and inexpensively.  The plus for me is I can disassemble the stove and cart it outside for the summer months.  A 30 gallon barrel of sawdust should burn for about 8 hours.  With extra 30 gallon barrels pre-filled with sawdust I can quickly replace a spent barrel with a fully stocked one as needed and filling the barrels outside would keep a good part of the mess out of the house.

In one of my forays on the web I ran across a video of a sawdust burning heater built in England.  You can watch the video here.  The model in the video is available from British Hardwoods Online for about $500 US.  Shipping inside England is about $75 US.  In an attempt to get a real clear idea how the stove was built, I did some searching and, through chance, ran across an old open source plan for a “double-drum sawdust stove“.  The plans are available (free) online at VITA.  Do a search for double-drum sawdust stove and you should find the link.

The design shown in the video is a takeoff (improvement) of the original double-drum sawdust stove design. When comparing the plans to the video, take special note of the difference in location of the single exhaust exit from the outside barrel near the bottom, the lack of damper on the chimney (not needed or advised) and legs instead of a “false floor” in the outside barrel. The inside barrel’s three legs hold it above the ash drawer and allows air to circulate around inside the bottom of the outside barrel facilitating the exhaust up the chimney.

These relatively simple changes improve the performance of the design over the original.  With parts and self-labor, this stove, with the aforementioned design changes, can be built for about $100 US.  As we build I’ll keep close account of what we spend as opposed to what we can salvage so I can share the result at the end.

Wadly is embracing the task of accumulating the necessary 55 gallon and 30 gallon drums.  I will acquire the stove pipe, sheet metal, metal drawer pulls, adhesive and gasket material.  In addition I’ll need to buy a 45° and two 90° elbows.

Rather than weld legs on the barrels, I’m going to use three fire bricks to hold the inside barrel off the bottom of the outside drum.  I’ll buy (hopefully used) stainless drawer pulls for the handles on the lid and drawer.  If I can’t find the pulls I want I’ll build some out of 3/8 mild steel rod.  I’ll fold, spindle and mutilate a piece of sheet metal for the drawer and I’ll use the cut-out piece as part of the vent control on the drawer face. I’m a bit fuzzy on this part, but I’ll get there.

I want to be able to install temporary fire proof wall covers for the corner where the burner will rest.  I’ve got plenty of fire brick to make a base on which to set the burner.  I can mortar them in with a clay/sand mortar which will make them easy to take apart and clean for reuse or I can build a 2×4 fence and set them in place therein.

I’ll supply pics as we build/test/build/test so you can see what works and what doesn’t.