Volume of a truncated cone, or...

Dave Shepard · October 17, 2009, 03:43:21 PM

How big is this log? 33" small end, 36" large end 9' 6" long. Red oak. Trying to figure out, with good accuracy, how much that sucker weighs. More at 11:00 :D

beenthere · October 17, 2009, 04:04:59 PM

Just calculate a cylinder with the diameter as half between each end.

Like 34½" diam and 9'5" long cylinder

pie x (34.5 ÷ 12 ÷ 2) x 9.5 = 62 cuft

@ 62.4 # per cuft for red oak, maybe around 3870 #

(takes me a bit to get all those numbers. you others are too quick ;D but right on.

)

Reddog · October 17, 2009, 04:05:48 PM

Just under 4000#'s by the weight calculator.

Dan_Shade · October 17, 2009, 04:11:28 PM

how much accuracy do you need?

you can figure out the volume using calculus. just estimating the cylinder part of it, you have 56 cubic feet, which would be 3553 lbs.

using the toolbox helper, estimating a 34.5" diameter mid length, it comes out to 3946lbs

I'd guess between 3500 and 4000 lbs.

red oaks lumber · October 17, 2009, 06:57:48 PM

closer to 4350lbs. i don't have my log scale handy. take b.f. x5.7lbs.

Dave Shepard · October 17, 2009, 07:37:49 PM

I was playing around, ok, cleaning up, at my friends mill. There was this big oak log sitting there, and I was wondering if I could pick it up. We have a CAT 307C at work with the worst thumb I've ever used, can't pick up anything with it. Well, maybe a 10" log. Anything bigger or smaller gets shot out like a watermelon seed. The Kubota picked it right up. Had to keep it in close, but it had a good grip on it. ;D I love Kubota thumbs. Best available, in my opinion.

beenthere · October 17, 2009, 08:49:01 PM

Quote from: red oaks lumber on October 17, 2009, 06:57:48 PM
closer to 4350lbs. i don't have my log scale handy. take b.f. x5.7lbs.

red oaks
Are you saying there are 763 bdft in the log?

4350 ÷ 5.7 = 763

Chuck White · October 18, 2009, 08:07:24 AM

The log weighs 3946.88 pounds according to the Forum Log Weight calculator in the Tool Box!

I just figured the average of the two end diameters and went with that!

red oaks lumber · October 18, 2009, 10:57:59 AM

thats not what im saying. scale the log first to determine how many b.f. then estimate the weight of the slabs.. i can't do all that fancy math like you guys do.lol

mrcaptainbob · October 19, 2009, 11:45:23 PM

7,459.64#'s air dried, 10,850.39 #'s green.

beenthere · October 20, 2009, 12:23:10 AM

mrcaptainbob
Would you elaborate on your numbers, pls.

SwampDonkey · October 20, 2009, 04:29:05 AM

What is your conversion from bf to solid volume? If you don't know where the conversion factor comes from than you could be way off. Does the conversion factor convert the volume in lumber or does it account for loss of slabs and sawdust?

Here is what I get from converting log to lumber with Doyle scale in the forum toolbox: 499 bf

I have two conversion factors for solid m³

499 x 0.00236 = 1.177 m³

499 x 0.00561 = 2.8 m³

This isn't weight, but which is relevant? ;D

Another thing my friends, is conversion factors are based on a fixed length and softwood vs hardwood, not random length. Here is an example:

Going from cords to m³ for softwood: 4 ft is 2.406 m³
8 ft is 2.265 m³

So converting to board footage instead of just calculating the solid log volume and multiplying by the empirical weight of green wood by species from the Wood Handbook or Wood Technology text is going to yield numbers all over the map.

The forum toolbox will find weight using empirical data published by forest products labs.

red oaks lumber · October 20, 2009, 01:04:52 PM

swampdonkey.. that makes my head hurt to much. lol

Reddog · October 20, 2009, 01:52:51 PM

Quote from: SwampDonkey on October 20, 2009, 04:29:05 AM
The forum toolbox will find weight using empirical data published by forest products labs.

In other words way less headaches. 8)

isawlogs · October 20, 2009, 07:40:16 PM

Swamdonkey , I read and re-read that a half a dosen times and still got no idea what da ----- you where saying . :

:D :

red oaks lumber · October 20, 2009, 08:40:38 PM

good, i thought i was losing the last bit of sawdust in my head! i'm not alone, yipee lol

Jeff · October 20, 2009, 08:52:54 PM

Donk, let us know when they finally figure out where their goona put you so we can all send a card.

Tom · October 20, 2009, 08:58:10 PM

I understood it :-\ :-\

Basically, everyone is estimating too many things, the weight of the wood, the length of the log, the diameter of the log, the scales for board footage, etc.

I like the idea of just using the tool box. Ron's pretty good with numbers. ;D

Dave Shepard · October 20, 2009, 09:51:34 PM

By using the toolbox, the only things left to chance is my estimate of how cylindrical the log is. It wasn't too bad, but did have a big crotch on one side that had been sawn off. :D

mrcaptainbob · October 20, 2009, 11:42:56 PM

Well, beenthere....I went to sleep last night realizing I goofed. Should've just kept out of it.

Now I'm getting 3,750.6 green/2,716.0 dry.
Machinery handbook has a formula for this:
V=1.0472 h (R sqd+Rr+r sqd)
V=1.0472 x 114" (324+(18x16.5)+272.5)
V=1.0472 x 114" (324+(297)+272.5)
V=119.3808 (893.5)
V=106666.74 "cu.
V=61.728 'cu. (10666.74/1728)
Red oak dry is listed at 64 #'s per cubic foot while dry is 44#'s.
Should'a just kept out of it....

SwampDonkey · October 21, 2009, 03:23:15 AM

Quote from: Jeff on October 20, 2009, 08:52:54 PM
Donk, let us know when they finally figure out where their goona put you so we can all send a card.

What Tom said. I wasn't trying to compute it by conversion factors, just pointing out it's follies. I was trying to point to the forum toolbox. :

I like the use of a standard volume equation like Captain Bob is using as long as it's understood they are site specific. Sometimes they develop one called an average as well. I'm sure the toolbox uses a similar volume equation, probably Smalian's. ???