Arboriculture Lowering Device – Design Project

Mick Anderson

Hi All

My name is Michael Anderson; I am a 4th year Industrial Design Student, from the University of Technology Sydney. I posted on here months ago regarding my Final year Major Project, where I am designing a new product to overcome current problems in the industry in relation to lowering devices. I am primarily looking at minimising the effects of Dynamic Loading on Rigging and Lowering Devices.

In the support of Safer Work Practices in Arboriculture I am writing to get some responses on the questions below.
I greatly appreciate your time and feed back.


Michael Anderson
0406 768 282
Michael.P.Anderson@student.uts.edu.au


Lowering Device Questions:

1) What methods do you use to lowering large wood in the tree removal process?



2) Have you ever used a Friction drum or Port-a-Wrap? Can you detail any problems you can see with these products?



3) Have you ever had an onsite accident or potential accident where a load was dropped; by not taking enough wraps on the lowering device for the estimated load to be lowered?



4) When blocking down (using a lowering device, sling and pulley; See attachment), generally what are the Biggest and smallest sections of the trunk you would carefully lower when working with a small drop zone? (Please indicate a range of approximate Length’s and diameters as well as an estimated weight range).

Attached Files

Blocking_Down_Images.doc (157.5 KB, 68 views)

JohN Dee

There is a few methods that we use and have used. Natural lowering where the friction from the rope running over the trees surface takes the weight.

Natural lowering where a pulley is in place at the top of your rigging point, but wraps of rope are placed around the trunk to get that friction again.

Portawrap + Pulley(s) combination is where we have a pulley tied at the top (sometimes we'll set a range of pulleys up the trunk to keep all that weight in the whole of the tree rather then just a small piece at the top) of the rigging point (Usually with a girth hitch) and a Portawrap tied (Timber Hitch) at the base of the trunk at about gut height. Putting all the friction into a man made system so it is consistent friction and you are able to work efficiently at optimal speeds.

Friction Drum/GRCS + Pulleys combination where there is a range of pulley set up the trunk to the highest rigging point so again we can keep all of the weight and loading distributed throughout the whole tree. The Friction Drum/GRCS comes with its own tie in on a crank. The Friction drum you are supposed and reccomended to cut into the trunk to minimise if not eliminate it from sliding up - The GRCS would make sense to aswell, but I'm unsure of the manufacturers reccomendations on it.

We have extensively used the Porta Wrap and found that it is pretty much fool proof. The only problem we ever run into rarely is we may snag a branch being lowered into a stub or crotch where it gets stuck and is a pain in the ass to lift and jiggle/pull out. One other problem that comes to mind, may be a newbie groundsmen to lowering-portawrap, they may grip the rope too tight and drag themselves under the drop zone.

The friction drum I have only used once and not for very long. Some problems with it would be having to go underneath the load being lowered to winch it up, but yet couldn't be fixed by making it motorized with a remote because by hand cranking it you can get the "feel" of how the tree/rope is handling the load, the remote would simply keep cranking to the point of failure if you were not very careful. If you could make it so that the crank knew how much your were lifiting and pressure applied on them, then the remote could be learned to be used.

Never had an accident. Only thing that comes close is when I was more green to climbing, my father locked up the last load I was topping out, being green and it was a conifer my gaffs kicked out and I probably slid half a foot down (caught by my cinched secondary line attachment) - that's called taking TOO many wraps (Sending the climber for a ride) and the groundy gets a stub or chainsaw thrown at him.


Well that is a VERY difficult one to answer... Drop zones vary in how small they can get. You may have a house right next to the tree (-3m) and the actual ground you've got a fair whack of it to use(+6m2) or it's in an open space(3m+) over a manicured garden. The first one means ya gotta keep them relatively small(its hard to put it into writing, ya know what you've gotta do but can't justify it with words) so you don't hit the house where the latter you can make them bigger, just keep them managable.

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kieren

We use friction drums a lot on big removals! its great but i would like to see one for big pruning work that wont hurt the cambium