Modified Nimbewill Wood Stove - Part 2

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scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
They say never work with animals and children. Well add stainless steel to that list, blimey it's hard stuff but I finished the stove...see here . Afraid I couldn't resist lighting it before photographing it, so it's not the shiny masterpiece it once was.

finished1.JPG


Aside from the problems of working with stainless steel (i.e. going through a lot of blades and cutting disks and wearing out a file!!) it wasn't too tricky to build. If you fancy a go you can download templates from here . Just print off the PDF choosing the no scaling option in the print options dialog.

First off I laid out the templates on my piece of stainless steel, before sticking them in place with a spray adhesive.

layout.JPG


Then I did a final quick measure before doing any cutting. Last chance saloon, once you've started cutting it's too late to go back!

measure.JPG


Next to make handling easier I rough cut out the parts with a jigsaw. WEAR SAFETY GLASSES - Eyes and flying metal bits don't mix.

I found that a normal HSS metal blade worked best, although they wore our fairly quickly. Things like progressor blades were too aggressive for the sheet material and caused the piece to bend horribly on some of the finer cuts later on.

roughcut.JPG


After the rough cuts, I trimmed as close to the line as I could with the jigsaw. I then did the tricky bits like the slots before finishing the piece by filing down to the line. Best to get the slots right rather than crying into your beer if you've messed up a slot and wasted all that filing effort. Stainless steel is HARD!!

The best method I found for the slots is to use a heavy duty cutting wheel on a dremel at about 3/4 full speed and cut into the center of the slot just enough to fit the jigsaw in. Then used the jigsaw to cut the slot out *exactly* as marked. Note my nifty homemade "vice" to make working on the sheet easier! I basically drilled a big hole and put a clamp through my bench! For the larger air slots I first drilled the ends (see tips below) and then use the slot cutting technique before finishing with a half round needle file.

dremel.JPG


After a bit of research I decided to drill the holes so I could control the volume of airflow and it's position through the grate, rather than my original BBQ mesh idea. For drilling the holes I found a normal 10mm HSS bit and running the drill slowly worked best. Centre punch the holes first. Don't get the bit hot or the stainless will eat it. I always kept the bit cool enough to touch. Keep some water handy to quench it in if it gets too hot. I'm sure oil is better but the stainless is probably going to kill the bit anyway before you have to worry about rust! (BTW I used a proper punch not the nail in the background for marking the centres. Nails don't touch the stainless, I tried it!) I have used nails to help stop the piece sliding aound under the force of the drill.

drill.JPG


For the bends I used a ball pein hammer and one of those mini vices, worked a treat but you need the hammer to get the bend nice and tight.

bend.JPG


When filing the sides, leave cutting the tab slots till last. Without the extra bit of material they are too flexible to file easily. When your ready to cut the slots use the jigsaw and tidy them up with a needle file.

tabs.JPG


Once finished put the bit's together and tada! :D

lit.JPG


Scoops
 
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scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
Cheers Leon,

Just been reading about your day with Fenlander, you're a lucky guy! Keep up the great work and I'll look forward to attending one of your courses in a few years time!

Scoops
 

Ogri the trog

Mod
Mod
Apr 29, 2005
7,182
71
60
Mid Wales UK
Scoops - nice one buddy,
I read about your modified top plate on another thread, how does it work in practice? ie without getting air to flow up around the sides of your Crusader cup.

You've done a good job there, I left the pieces of my attempt quite rough, just cleaned up the edges that I'll either catch my fingers on, or might damage a mesh bag in which the whole thing is carried.

ATB

Ogri the trog
 

scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
The results are a bit mixed, the top plate works but I've tended to remove it for cooking and add it to slow things down.

Adding a chimney has a dramatic effect (see below), and I'm thinking about redesigning the top plate swapping the hole for a rectangular chimney across the the back of the top plate. This will also provide a larger area on the rest of the top plate to be used as a hotplate for cooking bannock, simmering or drying tinder etc...

I made my first chimney in a hurry, can you tell :D

chimney.JPG


A problem though is it getting too hot for the stainless with the chimney on and the stove enclosed. The grate glows bright red and sags and the sides get pretty soft too! An aluminium version would probably be a puddle!

Scoops
 

Stew

Bushcrafter through and through
Nov 29, 2003
6,456
1,294
Aylesbury
stewartjlight-knives.com
I guess it's too early to tell, but I'm curious how you'll find the height adjusters.

Personally I suspect that you won't see a big difference in performance but I'll be interested to see how you get on (ready for me to make my version! :D )
 

scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
I actually tried to move the air flow forwards by drilling the grate to create a particular area where the primary air comes in rather than using the indescriminate BBQ mesh. The holes are in the front 2/3 of the grate and are sized to open up about 30% of the area. (If you look at the bending picture you'll see what I mean).

I opted for that solution as it still allows the stove to be set up as a normal nimblewill with the vents at the back.

In that sense the height slots do make a difference as they allow the different configurations. The problem I have encountered is that without a chimney and the stove enclosed you get a lot of smoke which pops and flares(wood gas generation). Put a chimney on top and this all vanishes to be replaced with a continuous roaring flame from the wood gas.

Need to do some more experimentation before I decide how to progress.

Scoops
 

Glen

Life Member
Oct 16, 2005
618
1
61
London
Nice one.

scoops_uk said:
The results are a bit mixed, the top plate works but I've tended to remove it for cooking and add it to slow things down.

Adding a chimney has a dramatic effect (see below), and I'm thinking about redesigning the top plate swapping the hole for a rectangular chimney across the the back of the top plate. This will also provide a larger area on the rest of the top plate to be used as a hotplate for cooking bannock, simmering or drying tinder etc...

I made my first chimney in a hurry, can you tell :D


A problem though is it getting too hot for the stainless with the chimney on and the stove enclosed. The grate glows bright red and sags and the sides get pretty soft too! An aluminium version would probably be a puddle!

Scoops

With the micro chimney it's begining to look like a miniture kifaru stove.
http://www.kifaru.net/stovspex.htm
Click on the link for single tube pipe for chimney idea.
They make their stoves out of stainless steel, though I've not found out how thick, so would have thought you'd be OK, they do give a lifetime guarentee on them.

Image intensive link to one used with a tarp http://forums.kifaru.net/cgi-local/ultimatebb.cgi?ubb=get_topic;f=4;t=000972;p=0
Half way down shows surprising pack size which amazingly includes the chimney.
 

fred gordon

Bushcrafter (boy, I've got a lot to say!)
Mar 8, 2006
2,099
19
78
Aberdeenshire
Fantastic work. I made an environmental fireplace, based on the Bill Mason model, some years ago and it has worked very well over the years. However, it has had its day and needs replacing. Are there any plans to make the drawings available for sale or on the site for downloading? :)
 

scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
Thanks Glen the kifaru is exactly the type of thing I was aiming to build. That was a very interesting link! Can't afford one and I have reservations about things like wing nuts which are easily lost on a woodland floor, but it's getting the juices flowing for my MkII version!! :D The roll up chimney is a great idea.

Fred - I would suggest if you want to build something now, knock up a quick basic nimblewill, they are great little stoves I found having a rough version to mess around with made me more patient making my modified version MkI. There's gonna be a MkII along soonish (off to Scotland for a couple of weeks first).

The MKII is going to be larger, that means heavier. What would people regard as a maximum weight? Bear in mind there's always the option to configure it as a basic nimblewill and leave the other parts at home. An Optimus Nova weighs 420g plus say 600g for a full half litre fuel bottle. We don't need to carry fuel so would a top weight of 1kg be OK or could we go higher for the full stove say 1.5kg? The stove is 650g at the mo, doubling that weight will provide a much bigger stove with a larger firebox and if I can find a source for 0.004 tempered stainless foil a chimney too!

Scoops
 

jdlenton

Full Member
Dec 14, 2004
3,002
7
50
Northampton
scoops that's a great piece of work even more so because you made it by hand out of stainless I've always contemplated making one of these but i would only have used mild steel for the prototypes as it a fire place who cars if it rust a little. let us know who you get on with the next ones a bigger stove wold be great i recon. If your going to make some more in stainless i recon you need to find a friendly engineer with a laser cutter that accepts beer as currency.:)
 

scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
Thanks for all the positive comments, much appreciated. :D

JD - got a mate who might know someone with a laser cutter, so I might have to explore that avenue. If anyone knows of anywhere that can laser cut stainless please let me know!

Scoops
 

scoops_uk

Nomad
Feb 6, 2005
497
19
54
Jurassic Coast
Hi Wildrover,

Sorry for the delay in replying I've been away in Scotland for the last two weeks.

I used ~1mm stainless offcuts that I got cheap from a local sheet metal workers. I think the actual thickness is 0.9mm but I've not actually measured it, I just asked if they had any sheet stainless offcuts around 1mm thick and used what I got :D

Scoops
 

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