Friday, July 3, 2009

How much do trees weigh?

We are going to be planting lots of trees at Las Olas and are looking at getting a skid steer loader and a tree spade. We want to make sure we get the proper equipment, so we are calculating how heavy the loads (trees) will be. Below is an interesting article i found on this subject.

Analyzing tree weight formulas

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Analyzing tree weight formulasschrader@beaches.netSun, 9 Mar 1997 05:07:15 -0600
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Analyzing the weight of large tree for safety and cost effective handling.
In having to remove and relocate large trees I found it reassuring to have used a accurate method for establishing the weight.
I have a chart I use for figuring crane loads. The chart is from the U S Dept. of Interior "National Park Service " sheet "Rope Knots and Climbing". I found the chart in one of Sherrills tool magazines about a year ago or so. It shows weight by species and provides 1 column with weight by cubic feet and others by increasing diameters in inches from 10"dia. To 36" dia. Its kind of convenient so you dont have to make the math calculation.On the chart.Live Oak 76 lbs per cu ft is by far the heaviest of those listed Shagbark Hickory is the next closest at 64 lbs per cu ftPines and spruce at 34 lbs cu ft The others all run around 40 to 50 to 60 lbs per. cu ft
AS I am 46 now and my bones tell me its time to be an Oak Man. I use cranes when ever I can as I have found their use to speed the work so effectively as to make them a economic advantage not to mention the ease and greater safety when dealing with extreme weights. Of large removals and the occasional large transplants. I have transplanted a 48" Live Oak but thats another story. A 26 rootball weighed a lot more than the tree.
When I worked as a Carpenter I had some experience figuring the volume of concrete for filling round columns. I have even figured volumes on a shape called the frustums of cones. Which by the way is relative to a tapering tree trunk. Cones are like the (ice cream cone in having a pointed end. A frustum is the name used for describing what is left of the cone shape after the pointed end is removed. Logs and frustums are relatively the same shape. Circular objects that possess two ends of different diameters. Providing the log possesses an even taper from one end to the other than they are the same as frustums. Some caution is advised as if the log possesses a sudden change in its diameter at some point along its length then an under estimating of its volume will occur. To be on the safe side it would be better to use a slightly larger size on the small end or more accurately figure it in separate pieces, starting and stopping at the changing places.
No doubt a log 4' in diameter and 8' long weighs a bunch. A log 12 in diameter would be a whole bunch more than that. I have always lifted them with one finger. That is one finger circling in the air signaling the operator of a crane.
However in the interest of establishing some accuracy so one doesnt find oneself hiring a larger crane than you need. Or cutting a log up more than you need to. Or on the other side having too small of a crane and having to cut it up a lot more than you thought. I thought I would take you through what I believe is an accurate way to establish the weight of logs.
Formula for figuring the volume of a cylinder. Volume = .7854 times the (diameter to 2nd power) times the Height.V = .7854 times diameter times diameter times the height.The Volume of a 4 foot diameter log that is eight feet long is v = (.7854 times 4 times 4 times 8 ) = 100.5312 cu. ft.
A four foot diameter log, eight feet long is 100.5312 cu. ft. a cord is 128 cu ft. You might think a cord is a cord. I have found in the past that a cord can be loosely confusing. The Microsoft Bookshelf dictionary says " cord 8. Abbr. CD. A unit of quantity for cut fuel wood, equal to a stack measuring 4 W 4 W 8 feet or 128 cubic feet (3.62 cubic meters).
I sell pine pulpwood to the local paper mill. They pay me by the cord. I get $54 for every cord I bring. They weigh the truck in and out and give me credit for 1 cord for every 5,800 lbs for Pine and $48 for Hardwoods (Oak). For some reason I have found that sometimes people mistakenly will think that a cord weighs a ton. It doesnt so dont. A ton is a measure of weight thats all and has no association with cords or their weight.
Microsoft Bookshelf dictionary says "ton (tyn) nounAbbr. t., tn.1. A unit of weight equal to 2,000 pounds (0.907 metric ton or 907.18 kilograms). Also called net ton, short ton.2. A unit of weight equal to 2,240 pounds (1.016 metric tons or 1,016.05 kilograms). Also called long ton.

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