Firewood # 6 - The Wobble!

We have quite a few trees growing uncomfortably close to the house, and as we slowly tidy up we are trying to get rid of them, with the plan of replacing them hopefully with better trees planted in more appropriate locations.  Around the smallholding there are tons of Silver Birches, and one in particular is too close to the house.  I've been hesitating about cutting it down as it is very tall, and, in one direction it is about 6 metres from a telephone line serving our neighbours house and 4 metres from the lane, and in another direction it is about 8 metres from the house.  In other words if I got the felling wrong I would either be in trouble with our neighbours or Jo!

After many months of hesitation and procrastination, yesterday I thought I would sieze the day and sieze the chainsaw and go for it!  I've been eyeing it for several days, circling it to see which direction it naturally leans in the hope that it is away from the telephone line and away from the house!  Ideally I wanted it to fall directly away from the road, and luckily it does have a very slight lean that way.

There are plenty of step by step guides on the Internet and in books so I won't go into too much detail, the drawing below shows what I did to fell the tree:


How I Felled The Silver Birch

This is the biggest tree I have ever felled, and I must admit it was a massive relief when it all went according to plan and fell just where I wanted it to!  Jo had helpfully been telling me horror stories about someone who accidentally cut off his wife's head with a chainsaw which had increased the pressure to get it right and fell it safely quite a lot!   The first 2 cuts determine the direction of fall, and the 3rd cut creates a 'hinge', which allows the tree to fall in a controlled way.

The Hinge

Like everything, practice makes perfect - I'm sure the next one will be neater, but I'm still fairly happy with this.

The Result!

I measured the 'vital statistics' of the tree with results as follows:

	Circum.	Diameter	Area
Units	m	m	m^2
Top	0.4500	0.1432	0.0161
Bottom	1.1500	0.3661	0.1052
Length	12

'Bottom' means around 20cm above the ground, and 'Top' means the point where a single trunk stops and starts to become several smaller, but still vertical, branches.  It's a little bit difficult to see quite how much additional height above the 12m there is as most of it is stuck through a hedge at the moment(!) but from what I can see I would guess maybe 5m or more.

I wanted to calculate the volume, density and then derive the total weight of the firewood the tree yielded.  It would be really useful to have a rule of thumb by tree type to use in the future when, hopefully, we're using wood to cover all of our heating needs.  Anyway, the starting point for the calculation that I used was to assume that the main trunk of the tree is a truncated cone.  This would allow me to calculate the volume of the 'theoretical' cone (i.e. if the tree actually ended in a sharp point), and then subtract the volume of the part from diameter 0.1432m to the sharp point.  Cutting a simple cube, measuring it and weighing it gives the density and then we're in business!

 Beautiful Section - Future Cheeseboard I hope!

I cut a block, measured and weighed it and found that the density is approximately 1000kg/m^3, so our firewood pile is approximately 0.65m^2 x 1000 = 650kg


Propping prior to first sectioning cut

It was a bit nerve wracking but overall really pleased with the result - had a momentary 'wobble' just before the tree fell when I thought for a second it might be going the wrong way, but it all worked according to plan with no roads blocked, telephones disconnected, buildings or vehicles crushed!  Result!  I will be more confident on the next one!

Finally - apologies for the awful formatting of this post - hope any mathematicians have their microscopes on standby!

Ben explaining about sawdust to Mummy & Kate

 

 

Daddy's Little Helper!