Choosing the Right Machinery for Effective Mechanised Arboriculture

I often get asked to recommend different types of machine, it’s horses for courses as I’m sure you can imagine.

The two most important factors are machine size and access availability. Generally speaking the machine can’t be too big for the tree but you need to be able to get it in and set up.

Physics

You cannot beat the laws of physics. When lifting a load you either need outrigger spread or weight in the base. The wider your outrigger spread or the heavier the base the more you can lift at given radius. It is as simple as that.

We wouldn’t consider anything smaller than a 25t excavator or 6t – 30m rotohandler for the majority of work. There are quite a lot of 14t machine out there fitted with Vosch grapple saws and they have their place, we run one ourselves, but I would consider these an aid to manual handling rather than mechanised arb. Often the reach is not high enough to enable the operator to be able to select a small enough section of tree to prevent the machine overloading.

Tracked or wheeled ?

I’m a fan of tracked excavators for mechanised arb. You know where you are with a tracked machine. Wheeled excavators such as Sennebogen 718 are ok for some highway work but will get stuck on a wet verge when trying to park up overnight etc. I went to a demonstration years ago arranged by a large forestry organisation and a machinery supplier. It was a perfect demonstration on how not to do it. They had two wheeled machines on site, a Sennebogen and Merlo rotohandler. The drawbacks of both these machines is that they both require outriggers to work properly. With both machines the operators simply drove up and deployed the outriggers without looking where they were positioned. In this case on the grass verge, no out riggers mats, just the plate on the foot. The operator of the Merlo even extended the boom out over the onlookers to demonstrate how far it would go!  We left shortly after.

My point is, many people would have left that day thinking “that was great” rather than questioning “was that safe”?

Slope angle.

Rotohandlers and wheeled excavators require relatively flat ground to work on. Even an incline on a road can be too much. Below is a picture of our roto set up on an 8 deg slope which is about as far as we would go. It doesn’t look great.

This is a job that was subbed out to us so I had surveyed the site. I’ll be honest, I hadn’t even registered that the slope could be a problem, it was that slight.

So, in a nutshell. There are many different options out there. If you are in any doubt, ask for a site survey before hiring a machine in. Make sure it’s the right one for the job.