Bwo Drill Spindle Question

[jojocupcakes]

I've been reading a lot of articles lately about the bow drill method and how to apply enough pressure on the hand hold and bow to stop the cord slipping...

I'm curious to know as to why no articles mention cutting a ridge around the spindle so the cord can sit in accordingly and not slip outside this area (a tad cheating I know but in theory it'll stop the cord ride too high or too low thus making the method more effective and easier for novices like myself to learn the technique or easier in difficult situations where time is an issue)

I know the aim is for the firewood to produce a coal and there MIGHT be a high possibility of the cord creating friction with the spindle and setting alight if the spindle is not abrased enough (ie too smooth, ie innner softer wood exposed), thus cutting into the ridge to add abrasion.

I couldn't find a picture to demostrate my example so I put my ASCII art skills to the test

edited: I'll have to link a print screen of the picture instead, the formating on this site made the ASCII picture look awful

link: http://a295.ac-images.myspacecdn.com/images01/54/l_5518acff0cc599a75fa6b8ee0c4d9236.jpg (lettme know if you cant see the picture)


I'm just curious to know. What are you thoughts on this?

 

[Silverback]

I dont think the cord travelling up and down the drill is what is being referred to as slipping - it is where the cord loses its tension and the drill starts to bind in the hearth allowing the cord to slip around the circumference of the drill. Clasping the bowstring in the hand a little further up the bow can reintroduce tension and encourage a slipping drill to turn again however the first opportunity should be taken to re-tension the bowstring properly. The problem with cutting a dedicated notch is that your drill will only be useable until it starts to wear down and you need to change the position of the bowstring on the drill. In a dedicated notch the drill will either need to be reduced to the same diameter along its entire length to continue using it or it will need to be discarded. Does that make sense?

 

[Longstrider]

I tried putting a small notch in the drill before I had any real success with the bowdrill. I found that it did not help at all. There are a few reasons why I think it's not such a good idea as it might seem. The notch effectively reduces the diameter of the drill and this allows less leverage, or torque, to be applied to the drill by the cord. If you look at the way the cord is wrapped around the drill you can see that it has a natural tendency to work around the drill in a spiral as you move the bow.A notched drill makes the cord rub against itself far more than a notchless drill does because of this. Cord rubbing hard on cord soon results in two shorter lengths of cord
I have also over-done the notching and ended up with the drill being so weak at that point that I simply snapped the thing in half as soon as I started bowing it.

If a drill becomes polished and the cord slips too easily on it I tend to tap the drill with the edge of my knife at a diagonal, all around it, then again on the opposite diagonal. This crude checkering of the wood gives plenty of grip for the cord without thinning the drill.

 

[Glen]

I'll use that narrowed drill bit if I've only got a very short bow ( or attempting one of Rich59's minimum bowstroke challenges ) as it gives an gearing ratio advantage between bowstring and the business end of the drill.
The otherside of that is that, if it's got a gearing advantage it'll have a traction disadvantage and the bowstrings more likely to slip round the drill without spinning it.

Longstriders method of slightly nurling the drill sounds a good idea, that's one that I'll file away in memory , thanks.

 

[Biddlesby]

Instead of a notch which reduces the diameter, how about slipping some rubber rings - like some big gromets - above and below? Not sure if this would work.

Or start with an extra thick drill, reduce diameter for correct size with a 'band' in the middle, then cut a notch into that. Seems like a lot of work for something that you can achieve just by altering your technique, though!

 

[Ogri the trog]

Seems like a lot of work for something that you can achieve just by altering your technique, though!

Thats it in a nutshell,
Other than the correct wood combination and the right shape, why waste your precious survival energy on it. It is a skill better shown person to person than learned from a text, you just have to learn an acceptable technique.

Good luck

Ogri the trog