[Stoves] Cutting wood down to size for batch-fueled stoves.

[Lanny Henson]

Maximum wood size for batch-fueled, top lit, household size cooking stoves.



This is about wood sizes for stoves that burn fire wood not wood chips, rice 
hulls, or pellets, for which many TLUD type stoves are designed to burn.

Most wood fired, batch-fueled stoves like the "TLUD" and "Top Lit 
 Combustors" are very efficient and  clean burning, but they need smaller 
pieces of wood.

Being able to burn larger pieces is a benefit, because end users do not like 
cutting wood down to shorter lengths necessary for the typical batch-fueled 
stove.

So when  considering  household size,  batch-fueled , top lit, cooking 
stoves,  should the maximum length of wood, that a stove will burn , be a 
factor in  rating,  designing or considering the purchase of a stove.

If a stove needs I kg of wood to perform a cooking a task, you can't just 
light a 1 kilogram chunk of wood it has to be cut into pieces.

Wood is cut in two directions, there is  "cross cutting"  across the grain, 
which is usually done with a saw, this can be a problem, especially if you 
have no saw!  and there is the splitting of wood , the long way,  or "with 
the grain", this is easy.

So when considering wood size it is the length that is of concern, because 
it is easy to  split the wood down to the right mass or size pieces, but it 
is more work to cross cut wood to get  a length short enough to fit in the 
burner.

The burner needs to be sized for the wood to lay horizontally because you 
can't count on wood burning well when standing on end.

One way to cross cut wood, at the household level,  is to split wood down to 
size, that can be cut or chopped in two, with a machete, or an ax, or with a 
small hand saw.

End users do not like cutting wood down to the shorter lengths necessary for 
batch-fueled stoves,  but batch burners take less time to tend,  and they 
use a lot less wood,  so it is worth some time and hassle to downsize the 
wood, the question is how much?

Some lengths of wood to consider.

·        5 cm or 2" long,  It can take a lot of work to cut wood this short 
,  but chunks this size, burns well in a small stove and chunks have good 
air flow up through the fuel bed for the TLUD.

·        10 cm or 4" long pieces would take less cutting and maybe the best 
size.

·        15 cm or 6" long would take even less work to cut , but using wood 
15 cm long pieces may be more difficult to burn in a small batch-fueled 
burner.



A stove that would  burn 6" long pieces would have an advantage over a stove 
that needs 2" pieces to burn.

So I think fuel size should be a factor when considering the design, rating, 
or purchase of a stove.
Lanny Henson


----- Original Message ----- 
From: <ajheggie at gmail.com>
To: "Discussion of biomass cooking stoves" <stoves at lists.bioenergylists.org>
Sent: Sunday, August 25, 2013 7:50 AM
Subject: Re: [Stoves] Cutting wood down to size for batch-fueled stoves.


> [Default] On Mon, 19 Aug 2013 16:47:34 -0400,"Lanny Henson"
> <lannych at bellsouth.net> wrote:
>
>>
>>I know there has been some complaints about cutting wood down to the small
>>size necessary for batch-fueled stoves,  so the longer the pieces a stove
>>will burn, the better. This is one area where stick burning stoves have an
>>advantage over batch-fueled stoves, that is with fuel length issues.
>>
>>
>>
>>So what would be a minimum length we can ask people to cut their wood?
>>
>>What is the maximum length that a batch-fueled household stove should 
>>burn?
>
> Interesting question, back before machine tools it was normal for
> large fires to burn cordwood, the length of 4 ft (1.2m) was a
> compromise for the wood to be handleable and to reduce the need to
> cross cut. I imagine saws weren't generally available for forest work
> and restricted to cutting wood for joinery, planking etc. doing things
> that add more value. These billets would be held on andirons and fed
> into a fire burning as they met in the middles to control power and
> rate of burn, muck like a 3 stone fire with sticks.
>
> Smaller fires probably used faggots, bundles of wood cut and gathered
> by billhook. Commoners sometimes had the right to gather wood "by hook
> or by crook" meaning small wood that could be snapped off (dead) or
> short rotation coppice.
>
> These smaller pieces could be subsequently cut with a hatchet.
>
> When I sold firewood locally most people accepted 12" (300mm) logs and
> split such that they could be picked up across the cross section with
> one hand. Cutting and bagging we had to reduce the length to 7"
> (175mm) and this was only easily done on a saw bench. Of course as you
> get shorter lengths the waste sawdust becomes a problem as well as a
> higher percentage of the wood, typically a chainsaw or circular saw
> kerf is 1/4" (6mm).
>
> Nowadays a lot of the smaller arisings go straight through the chipper
> and when screened and dried make an excellent TLUD fuel.
>
> I think Alex English managed to get woodchip dropping into his wedge
> shaped natural draught modification to a side opening door on a wood
> stove, using Dasifyer principles.
>
> AJH
>
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