Modified Nimbewill Wood Stove

[scoops_uk]

Hi All,

Having never attended the school of “if it ain’t broke don’t fix it” I would be interested in comments on my modified version of Nimblewill Nomad’s wood burning stove.

Having already made an normal version out of stainless steel I’ve been impressed with the compact size (fits inside a mess tin) and heat output from the stove but fancied a version that didn’t need feeding so often.

My modifications are as follows:

1. Arching the back and side plates to make the stove more stable on uneven ground and lose a bit of weight.
2. Addition of an optional grate to allow air in under the fire (I intend to make this out of disposable BBQ mesh, but that was a pain in the bum to try and draw!)
3. Addition of more slots to allow adjustment of the floor/grill in relation to the ventilation holes to reduce/increase air flow into the stove. As pictured you can see the fire will receive air from only half the side vent.
4. Addition of an optional roof that has been holed for a flue or as a hot spot for a crusader mug/pot
5. Adding a turn up to the lip of the grate and floor. To stop coals falling out of the front stove when there is no face plate in place (a problem with the original). These are also sized to fill the air gap so depending which way up they are they can also reduce airflow.
6. The addition of a second (lower) piece to the front plate to allow the stove to be enclosed.

With a bit of imagination and using the various bits hopefully you can see that this allows variations from either an almost normal standard nimbewill to an almost fully enclosed fire box. (Which I hope will keep burning for much longer).

As a final point I deliberately chose not to have movable covers on the air vents for simplicity. You would need to choose your configuration in advance and then set up the stove that way.

Off to the garage to build one now!!

Comments and ideas appreciated,

Scoops

 

[scanker]

Well the drawings look excellent. I've no experience of this type of stove but my initial thought was that the roof part can't easily be removed with the stove going.

I presume the top of the front easily comes off for adding more fuel. Could the roof slot over vertical tabs so that it could easily be lifted on and off?

Great design though - I'll be interested to see the results. Do you plan to do it with hand (power) tools or do you have access to a CNC?

 

[scoops_uk]

I presume the top of the front easily comes off for adding more fuel. Could the roof slot over vertical tabs so that it could easily be lifted on and off?

Great design though - I'll be interested to see the results. Do you plan to do it with hand (power) tools or do you have access to a CNC?

My thinking was if you had the roof on you could either drop fuel in through the top hole or not use the top front piece and add fuel through that opening (or remove and replace the front with gloves). I decided against a loose roof as I was worried about it tipping if you sat a crusader full of water on it.

Wish I did have access to CNC, afraid it's a jigsaw file and dremel job

EDIT: I've just realised you can only just make out the tophole in the drawings I've posted. There a 50mm diam circular hole towards the back of the top plate intended for a possible flu or as a place to sit a crusader mug/pot.

Scoops

 

[Ogri the trog]

Scoops,
Your mod look as though it'll be a winner. I'd go slowly with the hot-spot hole though - it's the through flow of air that keeps the fuel burning - if you block the top with a crusader mug, it might upset the airflow inside the stove and extinguish the fire.
I made one a while ago and cured the mug problem by laying tent pegs (the original plans show holes in the bottom plate for it to be secured to soft ground with pegs) across the top castelations.
The idea of reducing airflow with the rise/fall bottom plate are good but might be negated an accumilation of ash near the holes - another use for the tent peg as a poker/scraper!
I like your idea of the two piece front plate though - I'll be making the other half to go with mine soonest.

Have you thought about submitting your mods to the Zenstoves site as a modified or refined version?

Let us know how it performs.

ATB

Ogri the trog

 

[Glen]

My thinking was if you had the roof on you could either drop fuel in through the top hole or not use the top front piece and add fuel through that opening (or remove and replace the front with gloves). I decided against a loose roof as I was worried about it tipping if you sat a crusader full of water on it.

Wish I did have access to CNC, afraid it's a jigsaw file and dremel job

Scoops

How about flattening out the bottom of the triangular castellations by a few mm on the back and two sides then having the top drop down into them with 3 matching points ( on the 3 sides) sticking out and having a couple of mm lip turned down to lock it in place, That way the top could be taken on or off easily but still keep it solid enough for the crusader when on.

 

[scoops_uk]

How about flattening out the bottom of the triangular castellations by a few mm on the back and two sides then having the top drop down into them with 3 matching points ( on the 3 sides) sticking out and having a couple of mm lip turned down to lock it in place, That way the top could be taken on or off easily but still keep it solid enough for the crusader when on.

That's a great idea. :You_Rock_

 

[mojofilter]

Looks good, and I love your CAD work! :notworthy

 

[scoops_uk]

It's Google Sketchup, makes anyone into a CAD God!

 

[mojofilter]

I'm DLing it the noo thanks mate!

 

[scoops_uk]

Glen, I've made the mods you suggested. Is this what you meant? Looks a lot better as you can drop the top plate in place once the fire is going.

Scoops

 

[redcollective]

Scoops is your skp file available?

No worries.

Stu

 

[scoops_uk]

Hopefully this link will get it...

download it here .

Have fun and don't forget to share any bright ideas!

Scoops

 

[Glen]

Glen, I've made the mods you suggested. Is this what you meant? Looks a lot better as you can drop the top plate in place once the fire is going.

QUOTE]

Essentiallly yes, I was originally thinking 3 lips per side but that was because I was under the mistaken impression you were making it from aluminium ( which might get a bit soft at high temperature ) Stainless steel i see no problem with.

I've thought of another easy mod you might consider ( well 2 one seems a good idea outright the other a possible )

Small mod to the front top section, how about 2 slots on the outer edges L shaped on right hand side reverse L on left hand side. The purpose being to be able to lift it off while hot with a couple of twigs.

The second mod was along the same thinking, 2 slots for removal but would involve staggering the top and bottom fronts by the thickness of the stainless steel so that the 2 front pieces could be removed and replaced independently. The possible downside of that is it might create a big enough gap for flame to come out.

Can't currently see any real drawbacks to the first mod though

 

[scanker]

That certainly addresses my point about taking the roof off with the stove going, scoops.

 

[scoops_uk]

Glen,

Not sure how well the L slots would work in practice, as the nature of the sheet material in the field probably means things will not lift off that easily. I could make the joining slots larger to make the fit looser and add a couple of holes for wire loops to be used for lifting the top front off.

Your second suggestion probably isn't needed as the tabs allow sufficient movement to take the bottom front off past the top part.

I suspect I'd best get on making this fella for some field testing.

Thanks for your comments scanker and glen.

Scoops

 

[scoops_uk]

Just when I was warming up the dremel...

I've been reading some interesting articles on wood combustion and ventilation ratios and grate design and primary and secondary air flow and ... you get the idea.

Basically I reckon the air slots are the wrong size and in the wrong places etc.

Gotta do some head scratching first though :thinkerg:

Scoops

 

[scoops_uk]

http://ecoharmony.com/thesis/AppdxE.htm

 

[Glen]

Would it help you not worry so much about the exact calculations if I suggest that they''ll vary with which type of wood you use ( and how dry it is )


In case not ( traslating these symbols into the nearest English I can

Cp : is a fixed constant
M : how much water your going to boil 1litre = 1 Kg
AT: temperature rise ( presuming you want to boil that's 100 - starting water temp )
Hfg : latent heat of evaporation a fixed constant
Mfg : amount boiled of ( In practise keep this down by keeping the lid on the pot
Mf : weight of wood used
Hf : the heating value of the type of wood ( which as stated above will vary considerably
Mc : the unburnt bits
Hc : the heating value of the unburnt bit ( if any could have been burnt as it may just be ash left )

So you could get the efficency of the stove from this formular but I suspect the "Hf" will be your hardest factor to determine.

 

[grumit]

maybe you could use a trangia pot lifter to remove the front plate while it is hot save you being burned ?
ps you could always send it to me for field trials

 

[scoops_uk]

Hi,

Thanks for the help Glen, but I was more amused at how complicated I could start making things than seriously stuck with the formula.

Grumit - I generally take a pair of UK issue leather gloves camping with me, so handling hot things isn't really an issue for me. It would be simple to add a couple of thin wire loops for lifting or as you suggest take a pot lifter with you although I'll take my MSR titanium one rather than a trangia one

Once I've got the design sorted I'm intending to post a pdf with plans and a set of instructions so you will get the chance to field trial one if you like!

Cheers guys,

Scoops