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Author Topic: A science question, any physicists, chemists in the house? The Rudiger roll!  (Read 1665 times)
dickster
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« on: July 20, 2020, 10:26:44 AM »

So I have a long term project, make an iron knife using only local materials and no modern stuff (apart from gloves, health and safety!)

I've learnt to light fires by twiddling sticks, hard work but it takes about 4 weeks to harden the skin on your hands.

You tube has been the teacher, but came across the Rudiger roll, a way to start a fire using 2 flat surfaces, half a cotton ball and a bit of ash from your previous fire.
It's very quick and much less hard work, I haven't yet succeeded with all natural materials (nettle fibres and wood ash, my ash got washed by our stream in spate, so I suspect has lost "something"), but I've come pretty close.

Can anyone explain just what is happening and how it works?



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A.L.
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« Reply #1 on: July 20, 2020, 11:14:54 AM »

hello,

Cellulose (Cotton ball) self ignites around 260°C so presumably rolling the ash around generates by friction this temperature and hey presto!
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azps
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« Reply #2 on: July 20, 2020, 11:52:07 AM »

So I have a long term project, make an iron knife using only local materials and no modern stuff (apart from gloves, health and safety!)

There's a bloke (Clickspring) making a replica of the antikythera mechanism, and he's been working on suitable tools for that sort of precision engineering that could have been made around 200 BC, including hand-sized cogs with 223 teeth: you might find his tool-making interesting:

https://www.youtube.com/playlist?list=PLZioPDnFPNsGnUXuZScwn6Ackf6LGILCa
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biff
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« Reply #3 on: July 20, 2020, 09:02:35 PM »

65 years ago,
  We watched Tonto light a fire. He split a 25mm x  300mm dried branch. In the centre of one he carved a small 4mm hollow.  20mm back from the end of the other  half he did the same. He got another  300mm length of Dried branch and put points on both ends that could fit down into the 4mm hollows.
 So he could lay one split half flat , place the point of the pointed 300, sitting upright in the 4mm hollow and help it upright by placing the 4mm hollow in the other split 300 split half and could hold the upright piece steady  by holding the split piece at the opposite end of the ⁶4mm hollow which was holding the upright piece in place.
    The Tonto made a small slack string bow and now he was ready to make a fire.
   Somebody let of a stink bomb and 50 of all rushed out into the warm Saturday sunshine. By the time we got back in, Tonto had moved to the railway track and with his forehead pressed
against one of the rails, he was  saying the train was 3 mile away and travelling at heap big speed which works out at 32mph.
   A dozen of us moved into the wood after the matinee,
Someone braved the stinker ( The smell of rotten eggs) and we knew to wrap the bow string around the upright stick and pass it back and forth  which spun the upright stick at speed and ignited bits of fine dead grass , dried branches. We got a lecture from  Garda Winters, An absolute double for Winsor Davies but we all blamed Tonto. We were safe enough on the railway tracks. The train had stopped running some years previously.
    The Lone Ranger was OK but Tonto was cool.
      Biff
« Last Edit: July 20, 2020, 09:12:28 PM by biff » Logged

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dickster
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« Reply #4 on: July 21, 2020, 11:13:39 AM »

AL...Yeah but, how does the addition of ashes (or rust or even baking powder) help this process. Friction between ashes and cotton? Surely both spinning like a solid axle with no differential in adjoining speed, if you see what I mean. It might be the fine particle size used is the secret? Perhaps the dust firms up the centre of the roll, enabling high pressure and speed to be applied or does it somehow act as a heat concentrator like a thermal mass ? Or is it a chemical or catalytic process that lowers the combustion temperature?

azps watched clickspring like a hawk, fantastic.

biff: appreciated, I'm half way towards a fire bowstring with a piece of rawhide off a local (dead) calf! Neighbours getting wary of strange man.

Thanks for all your comments
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A.L.
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« Reply #5 on: July 21, 2020, 11:40:19 AM »

hello again,

AL...Yeah but, how does the addition of ashes (or rust or even baking powder) help this process. Friction between ashes and cotton?

I would go for friction between ash & ash generating heat which then would transfer to the cotton. There will inevitably be movement between ash particles.
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dickster
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« Reply #6 on: July 21, 2020, 02:07:56 PM »

Thanks, A.L.

I think I'm going to put a short length of wire maybe 2-3mm in place of ash and see what happens! Smiley
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Iain
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« Reply #7 on: July 21, 2020, 03:08:32 PM »

Hi
I have a faint recollection from my childhood about ash.
If I have remembered correctly, if you try to light a sugar lump it won't burn however if you rub it in ash first it is able to be lit. I was told the ash acted as a catalyst.
Wonder if it is similar with the cotton?
Not sure how my memory is ??

Iain
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A.L.
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« Reply #8 on: July 21, 2020, 03:51:38 PM »

If I have remembered correctly, if you try to light a sugar lump it won't burn however if you rub it in ash first it is able to be lit. I was told the ash acted as a catalyst.
Wonder if it is similar with the cotton?
Not sure how my memory is ??

Iain

If the ash contained an oxidiser the sugar (fuel) would burn/explode. Cotton would act similarly to sugar. Heat could accelerate the process.......Hmmmm? Roll Eyes
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oliver90owner
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« Reply #9 on: July 21, 2020, 07:26:17 PM »

‘Primitive Technology’ - a utube video maker likely has videos for making fires.  I particularly liked his forge development video.
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dickster
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« Reply #10 on: July 23, 2020, 10:29:28 AM »

Primitive Technology a must watch and a catalyst for me getting on with my little project.

Tried the iron wire, didn't work. Heading towards readily available very fine sedimentary iron ore coating (already worked with cotton wool) and nettle fibre.
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dickster
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« Reply #11 on: August 03, 2020, 10:25:23 AM »

Et voila!

Using the cellulose fibre from nettle and a dash of old wood ash, I managed to get a tiny ember going on Sunday morning and got a fire of local hardwood (crab apple, oak and blackthorn) going. I now have a store of fresh ash, so making fire in the future should be a walk in the park compared to stick twiddling.

A mate of mine suggested that as pressure is applied to the roll, it deforms from circular to ovoid section and continued rolling and deformation would create enough friction to heat the roll up. Rather like tidal forces heating up the interiors of planetary moons. Makes a lot of sense, so I guess your friction answers were correct. I'm guessing my "fresh" ash will help a lot, with perhaps a dash of chemistry taking place as well.

Thanks for the input, i am a happy bunny now.  Smiley
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