Odd problem with fire bow

[Lordyosch]

Hi made myself a new fire bow set the other day. Pine drill and the hearth was some B+Q planed softwood I had lying around. The bearing block is umm... Willow I think -it was left over from my original set.

I was sat there getting it started and I noticed smoke. Goodo I thought until I realised it was coming from the bearing block!

There was spit and waxy leaves to lubricate the bearing block and I checked the drill was pointy end up -it was. The hearth was just getting 'polished' by the drill with no sign of charring or burning in.
I was wondering if there is something in the shop-bought planed wood's treatment which is 'protecting' it.

Any thoughts?


Jay

(ps my new tarp arrived today -yippee!! Unspecified forest here I come...)

 

[Toddy]

I won't swear to this but........I use willow for a hearth board and it's awfully good.........might it just be that it's softer/ more fibrous than the pine ? Softwood is a misnomer really, it's rarely much to do with the actual timber strength.

Interesting to hear what folks think though.

atb
Toddy

 

[Ogri the trog]

Jay,
pine will do wierd stuff when used as a bowdrill spindle - being quite soft, it is likely the top point wore or split apart and got mushed, similarly the bottom point, once heated boiled off any organic solvent in the resin which then polished to a shine - allowing all the friction to be experienced on the top, causing your smoke.
Try switching the woods for something like willow all round, or hazel, cedar, ivy, or any other combination that excludes pine

Give it another go and let us know how you get on.

ATB

Ogri the trog

 

[andywinkk]

Willow on willow every time for me ?

 

[Lush]

To rule out any problems you might find it easyer to use the same wood for fire board and spindle. A good tip that helped me to get started.

 

[Matt_M]

The set i made consisted wholey of pine. I did get the polished effect from the end rubbing in the hearth, all i did then was add a little grit from the ground, to the depression in the hearth, this not only speeds up the whole process of getting char dust but also stops the polished effect. As for the bearing block i did get smoke from time to time but only towards the end just before id stop drilling.

 

[IntrepidStu]

MANY people have this problem. I don't see it as a function (wholly) of the wood used. It seems to me that with the "sharp" end of the drill, because of the small surface area, then the amount of pressure applied to the tip is greater than the "blunt" end. The answer is often MORE lubrication. Once the blunt end gets past the initial "polishing" stage and starts to build up friction from the warm surfaces, then the equation switches to one of "surface area" and because the blunt end has more if this, the most heat starts coming from this end.

Personally, I use a a thick limpet shell and it works amazingly well.

Stu.

 

[MikeE]

Bit late this but I was at a woodfest recently and they had deer knuckle bones which I was informed are used by some as a bearing block! Should have bought a couple but SWMBO was just behind me! Makes me sound right under't thumb don't it!

 

[g4ghb]

Bit late this but I was at a woodfest recently and they had deer knuckle bones which I was informed are used by some as a bearing block! Should have bought a couple but SWMBO was just behind me! Makes me sound right under't thumb don't it!

Don't worry about It - I know exactly what you mean mate! sometimes life is easier that way.

Anyway sounds like you have learnt the 2 golden words for a happy marrage / relationship .........

"yes dear!" - hasn't failed me yet!