[Stoves] Natural draft TLUD turn-down

[Lanny Henson]

Crispin,
Are you trying to attach a larger cylinder around a smaller cylinder, and you need for the ends of the outer shell to be closed off to the to the inner shell?
The main issue is you need a method to cap off a round cylinder?
And you need to do this with minimum resources?
Do you also need a method to roll and seam a round cylinder/ duct?
The gap is 10 to 12mm between the shells?
Is the inner cylinder metal?
Lanny


> On May 19, 2014, at 8:35 PM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Lanny 
> 
> I have a suggestion you can help with. We TLUD and sheet metal builders need an instructional video from you on how to take a rectangular sheet and turn it into a ‎down-drafting preheater. 
> 
> I made an up-drafting ‎cone and it worked well - that was on the Grasifier. But it is not as good as a correctly designed down-drafting cylinder. In general an open-topped cylinder will draft air in and out (like a stove without a pot on). It should be a 'chamber' with wind-proof entry holes adequate to supply the air, then a descending cavity not more than, perhaps, 10 to 12mm of space, then entries into the combustion area. 
> 
> I have already‎ described how to make blurted holes for that injection to ensure that the secondary air reaches the centre of the gas stream. The same can be applied to the air entries of the preheating chamber in that the smaller and more efficient the holes are, the less affected by wind the system is. 
> 
> So, how to attach the preheater to the middle of the stove?   How best to close the top and bottom to the (usually) cylindrical body?
> 
> How about if we have production tools at the level of a two-roller jenny? Press tools?
> 
> The general shape and method of functioning of a multi-fuel burner is understood. Making it by hand can be a challenge. 
> 
> Some of the guesswork can be removed. 
> 
> Regards 
> Crispin
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