# Punching holes in trees

1. Sep 3, 2009

### Woodman

I am a horticulturist not a physicist, hence the reason I am seeking your help.

I am currently drilling holes in a certain species of tree using a regular electric drill. (I do this to insert a special treatment - to explain why I do this would take many more words!).

The density of the green wood is around 720 kilograms per cubic meter. The size of the hole is 16mm diameter by 150mm deep.

I am thinking that it would be a lot quicker if someone could develop a pneumatic tool similar to the captive bolt tool that is used to stun cattle during slaughter, whereby the tool is placed against the animal's forehead, or tree in this case, and a trigger is pulled to fire a bolt of dimensions 16mm circumference into the tree to produce a hole of depth 60 - 150mm depth (depending on the size of the tree). Alternatively the bolt could be hollow with the leading edge sharpened to cut a core into the tree, which is then removed when the hollower corer is pulled out.

I mentioned this to a friend and he thought the tool would have to be very heavy (i.e. too heavy to work with in the tree) and/or the "kickback" would be a serious problem for the operator. So I wonder if any of you physicists can comment and suggest whether such a method would physically feasible?

If I wanted someone to build a prototype for testing, can anybody suggest whom I should contact?

Woodman.

2. Sep 3, 2009

### ManDay

Hey there, I think your friend is probably right. Consider the following: Shooting a cow in the head (just for the explanation) with a FMJ projectile will kill the cow (naturally) and leave a 1 cm large hole in the skull. That's about the same what happens when you use one these boltguns, apart from the bolt being withdrawn after the action.

Shooting a FMJ projectile into a fairly stronger tree however will not penetrate the tree with a clear hole and probably just stick the bullet an inch below the bark.

A stronger tree just is of different kind of consistence than a cow (I know this all sounds a little stupid). It wont budge when you shoot the bolt in it, neither is it going to "absorb" the bolt as easily as a mammal skull.

Just my guess.

3. Sep 3, 2009

### KnowPhysics

if you see basic difference between punching (what you are suggesting) and drilling (what you are using), you can easily identify why punching is hard then drilling. when you punch the wood, the wood must get compress or shrink to make room for your punch. but if your drill the wood, the drill bit keeps clearing the wood pieces outward so obviously you will be getting the space for your drill bit (wood is no need to shrink) so you will feel same force even if your drilling goes deeper but in case if punching if you punch deeper its goes harder because all the edges of your punch is already shrunk and its hard. when keep forcing it, its keep getting harder.

4. Sep 3, 2009

### daveg360

If you did solve the issues listed above I'd worry that whatever treatment you are using won't be absorbed properly be the now compressed wood. Are you currently just using a twist drill? perhaps some sort of core drill would be quicker?

5. Sep 3, 2009

### James Leighe

Yeah, get a good drill. It takes allot to punch a 6 inch hole in a tree, less to drill it out.

6. Sep 3, 2009

7. Sep 3, 2009

### pantaz

What type of drill bit are you using? A good quality auger style bit will easily eat through the toughest wood. Also, the drill motor will make a big difference -- A common, low RPM cordless drill is vastly inferior to a high-torque corded drill.

8. Sep 5, 2009

### bjacoby

Forget the naysaying and take the advice. Shoot a tree. I'll tell you what you'll find that a .308 Nato rifle will completely penetrate a three foot tree truck and kill the guy standing on the other side! Now a rifle bullet is pointed on the end and compresses the wood sideways to make the hole so the hole is not like a nice drilled one if that matters. The problem with a bullet is that it goes into the tree until it runs out of energy so controlling depth of penetration is difficult.

So we now have some salient points for your invention project.

1. The amount of energy needed is about that of a high powered rifle cartridge which we note is relatively inexpensive and light to carry in the woods (as opposed to a big tank of gas or other energy source). Think nail gun.

2. such a punched hole (like bullet hole) will be ratty compared to nice drilled hole.

3. Hole will likely return to a smaller size after bolt is withdrawn so you need to start with larger bolt and amount of shrinkage will depend on the species etc. of tree.

4. A captive bolt is better than a bullet because it has an automatic stop at a certain depth. However, given the high energies involved the bolt can be damaged easily or have a short life.

5. it is not certain if high velocity or high pressure is the primary parameter in punching holes in wood. Some experiments would seem in order.

6. Getting help from a gunsmith in the design of safe chambers and captive bolt design.

7. Note that once the bolt is IN the tree it's like a huge nail so you may need a second cartridge to get it out!

8. if a conical hole is acceptible, a water jet cutter might be an alternative.

Good Luck!

9. Sep 5, 2009

### Equate

:rofl: :rofl:

Love it!

10. Sep 5, 2009