CA1083537A - Method of handling harvested trees - Google Patents
Method of handling harvested treesInfo
- Publication number
- CA1083537A CA1083537A CA313,381A CA313381A CA1083537A CA 1083537 A CA1083537 A CA 1083537A CA 313381 A CA313381 A CA 313381A CA 1083537 A CA1083537 A CA 1083537A
- Authority
- CA
- Canada
- Prior art keywords
- bunk
- tree trunks
- ground
- tree
- butt ends
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60P—VEHICLES ADAPTED FOR LOAD TRANSPORTATION OR TO TRANSPORT, TO CARRY, OR TO COMPRISE SPECIAL LOADS OR OBJECTS
- B60P3/00—Vehicles adapted to transport, to carry or to comprise special loads or objects
- B60P3/40—Vehicles adapted to transport, to carry or to comprise special loads or objects for carrying long loads, e.g. with separate wheeled load supporting elements
- B60P3/41—Vehicles adapted to transport, to carry or to comprise special loads or objects for carrying long loads, e.g. with separate wheeled load supporting elements for log transport
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- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Public Health (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Auxiliary Methods And Devices For Loading And Unloading (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of handling tree trunks is provided.
The tree trunks are loaded on a bunk pivoted on a transport vehicle with the tree butts in alignment and projecting to the rear. The tree butts extend far enough to the rear and the bunk is sufficiently close to the ground that, upon pivoting of the bunk to bring the butt ends of the trees to the ground, contact between the butt ends and the ground occurs before the trees begin to slip off the bunk. The pivoting of the bunk is then halted, and the vehicle moves forwardly to allow the trees to be dragged off the bunk by the fric-tion with the ground. In this manner, the trees are deposited on the ground with their ends in alignment.
A method of handling tree trunks is provided.
The tree trunks are loaded on a bunk pivoted on a transport vehicle with the tree butts in alignment and projecting to the rear. The tree butts extend far enough to the rear and the bunk is sufficiently close to the ground that, upon pivoting of the bunk to bring the butt ends of the trees to the ground, contact between the butt ends and the ground occurs before the trees begin to slip off the bunk. The pivoting of the bunk is then halted, and the vehicle moves forwardly to allow the trees to be dragged off the bunk by the fric-tion with the ground. In this manner, the trees are deposited on the ground with their ends in alignment.
Description
~08;~537 This invention relates generally to the tree-harvesting industry, and has to do particularly with a method for handling delimbed tree trunks in such a manner that the tree t~unks can be deposited at an unloading location with their butt ends substantially aligned.
BAC GROUND OF THIS INVENTION
Several of the large types of machines designed to fell, delimb and handle trees include storage locations on the vehicle in the form of ~ivoting box arrangements, known in the industry as bunks. Machines known as feller-forwarders and loader-forwarders are in this category.
One prior art device capable of felling trees and of trans-porting the trees in a box-like bunk is disclosed in United States Patent No. 3,797,541, Kurelek et al issued ~arch 19, 1974 and entitled "Machine for Harvesting and Accumulating Trees".
While the machine disclosed in United States Patent ~o. 3,797,541 utilizes a tilted bunk with a closed rear end, there are several machines conventionally utilized in which the bunk has side walls only, or includes side-retaining means in the form of upstanding braces or posts along the side edges. In the latter kind of bunk, there are no retain-ing means at the forward and rearward end, and the bunk is capable of assuming a level or substantially horizontal position for the transportation of the trees, thereby minimiz-ing longitudinal shifting during the travel of the vehicle.
When the vehicle reaches an unloading location, the bunk is tilted to the rear, in order to bring the rearward end of the tree trunks (normally the butt ends) down toward the ground. However, due to the fact that conventional bunks . - - . . -. : : :
~8~ 7 .
are normally located rather high up on the vehicle, the angle assumed by the tree trunks before contact with the ground takes place is such that the static friction between tree trunks or between the tree trunks and the bunk is over-come, and some or all of the tree trunks begin to slide relative to each other and relative to the bunk. When the vehicle pulls forward to leave the tree trunks behind, the tree trunks are left on the ground without any particular alignment of the butt ends. The irregular and somewhat confused pile of tree trunks which results presents certain difficulties in regard to subsequent forrestry operations, for example in tallying, assessing species, and so forth.
These subsequent operations would be very much facilitated if the pile of tree trunks in the bunk could be deposited on the ground with the butt ends remaining in alignment. The butt ends would then all be visible simultaneously from a single position, and the various forms of assessment could be readily made without having to move trees, uncover buried butt ends, and so forth. ~-GENERAL DESCRIPTION OF THIS INVENTION
. ..
In view of the foregoing, it is an aspect of this invention to provide a method for handling delimbed tree trunks, which makes it possible to unload a pile of tree trunks from a bunk with the trees in the same rerative position as they occupied while sitting on the bunk.
Accordingly, this invention provides a method of handling a plurality of delimbed tree trunks, which comprises the steps:
a) loading the tree trunks on a bunk pivotally mounted on a transport vehicle, , . . ~ . . ! ~ , .
with the butt ends of ~iQ~eSe3trunks in ~;ubstantial alignment and projecting to the rear of the bunk, the bunk being spaced above the ground and being pivotal about an axis transverse to the direction of motion of the vehicle, the butt ends being sufficiently far to the xear and the bunk being sufficiently close to the ground that, upon pivotal motion of the bunk to rock the butt ends of the tree trunks down to the ground, contact between the butt ends and the ground takes place before any of the tree trunks assumes an angle to the horizontal whose tangent is either the coefficient of static friction between tree trunks, or the coefficient of static friction between a tree trunk and the bunk, which èver is the lesser;
b) transporting the tree trunks to a desired unloading location, ` c) pivoting the bunk to rock the butt ends of the tree trunks down to contact the ground without any sliding of tree trunks with respect to each other or with respect to the bunk, d) halting the pivoting upon contact between the . .
butt ends and the ground, and e) moving the vehicle forwardly while maintaining ~ :
the ~unk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, whiIe the tree trunks remain in alignmen~.
GENERAL DESCRIPTION OF THE DRi~WINGS
.
One embodiment of an apparatus adapted to carry out the method of this invention is illustrated in the accompanying drawings, in which like numerals denote like .
.. . .. . .
1083S~7 parts throughout the several views, and in which:
Figure 1 is a perspective view of a simplified loader-forwarder ~dapted toicarry out the method of this invention;
Figures 2, 3 and 4 are sequential views showing sequential steps in the method of this invention; and Figures 5 and 6 are schematic diagrams showing the geometric considerations which enter into the method of this invention.
PARTICULAR DESCRIPTION OF THE DRAWINGS
In Figure 1 is shown a vehicle 10 which includes a front portion 12 and a rear portion 14 articulated together as is well known in large, all-terrain vehicles. The forward portion 12 contains the drive mechanism and controls, whereas the rearward portion 14 supports a bunk 16 which is pivotally mounted at an axis 18 with respect to the rearward portion 14 of the vehicle 10. The vehicle would normally also include either an articulated loading arm or an articu-lated felling and loading arm. These additional mechanisms do not relate in any way to this invention, and have been -omitted for the sake of simplifying the drawing.
As can be seen in Figure 2, a hydraulic cylinder 20 has its lower end 22 pivotally mounted to the rearward portion 14 of the vehicle 10, and has its upper end 23, which is secured to the hydraulic piston, pivoted to the bunk 16 at a location forwardly displaced from the location of the pivotal axis 18.
The bunk includes a substantially flat tree-supporting surface (not visible in Figure 1 as it is covered with tree trunks), from the side edges of which short .
:~t33537 side walls 25 are upstanding. Extending upwardly and out-wardly at an angle from each side wall 25 are three posts ~7. As is obvious, the function of the posts is to retain a substantial number of tree trunks on the bunk.
Finally, the vehicle 10 includes an operator's cab 30, and the usual deep-tread tires 32.
As can be seen in Figure 2, a plurality of tree trunks 34 are contained upon the bunk 16 with the butt ends 36 in substantial vertical alignment and project-ing to the rear of the bunk 16. It is also clear that the bunk is spaced above the ground level 38 and it will be understood that in the operation of pivoting the bunk in the clockwise direction as seen in Figure 2 by extending the hydraulic cylinder 20, the butt ends of the lowexmost tree trunks will follow the tra~ectory shown by the broken-line arrow identified by the numeral 40 in Figure 2.
The essence of the method of this invention is to ensure that the butt ends 36 of the trees 34 are sufficiently far to the rear with respect to the pivotal axis 18, having .
regard to the closeness of the bunk to the ground, that, :
upon pivotal motion of the bunk 16 to rock the butt ends of the tree trunks down to the ground, the butt ends will contact the ground before any of the tree trunks begin to slide, either with respect to each other, or with respect to the bunk.
In more technical language, these conditions are met by ensuring that the butt ends of the trees are sufficiently far to the rear with respect to the pivotal axis 18 that, as the bun~ rocks clockwise (as seen in Figure
BAC GROUND OF THIS INVENTION
Several of the large types of machines designed to fell, delimb and handle trees include storage locations on the vehicle in the form of ~ivoting box arrangements, known in the industry as bunks. Machines known as feller-forwarders and loader-forwarders are in this category.
One prior art device capable of felling trees and of trans-porting the trees in a box-like bunk is disclosed in United States Patent No. 3,797,541, Kurelek et al issued ~arch 19, 1974 and entitled "Machine for Harvesting and Accumulating Trees".
While the machine disclosed in United States Patent ~o. 3,797,541 utilizes a tilted bunk with a closed rear end, there are several machines conventionally utilized in which the bunk has side walls only, or includes side-retaining means in the form of upstanding braces or posts along the side edges. In the latter kind of bunk, there are no retain-ing means at the forward and rearward end, and the bunk is capable of assuming a level or substantially horizontal position for the transportation of the trees, thereby minimiz-ing longitudinal shifting during the travel of the vehicle.
When the vehicle reaches an unloading location, the bunk is tilted to the rear, in order to bring the rearward end of the tree trunks (normally the butt ends) down toward the ground. However, due to the fact that conventional bunks . - - . . -. : : :
~8~ 7 .
are normally located rather high up on the vehicle, the angle assumed by the tree trunks before contact with the ground takes place is such that the static friction between tree trunks or between the tree trunks and the bunk is over-come, and some or all of the tree trunks begin to slide relative to each other and relative to the bunk. When the vehicle pulls forward to leave the tree trunks behind, the tree trunks are left on the ground without any particular alignment of the butt ends. The irregular and somewhat confused pile of tree trunks which results presents certain difficulties in regard to subsequent forrestry operations, for example in tallying, assessing species, and so forth.
These subsequent operations would be very much facilitated if the pile of tree trunks in the bunk could be deposited on the ground with the butt ends remaining in alignment. The butt ends would then all be visible simultaneously from a single position, and the various forms of assessment could be readily made without having to move trees, uncover buried butt ends, and so forth. ~-GENERAL DESCRIPTION OF THIS INVENTION
. ..
In view of the foregoing, it is an aspect of this invention to provide a method for handling delimbed tree trunks, which makes it possible to unload a pile of tree trunks from a bunk with the trees in the same rerative position as they occupied while sitting on the bunk.
Accordingly, this invention provides a method of handling a plurality of delimbed tree trunks, which comprises the steps:
a) loading the tree trunks on a bunk pivotally mounted on a transport vehicle, , . . ~ . . ! ~ , .
with the butt ends of ~iQ~eSe3trunks in ~;ubstantial alignment and projecting to the rear of the bunk, the bunk being spaced above the ground and being pivotal about an axis transverse to the direction of motion of the vehicle, the butt ends being sufficiently far to the xear and the bunk being sufficiently close to the ground that, upon pivotal motion of the bunk to rock the butt ends of the tree trunks down to the ground, contact between the butt ends and the ground takes place before any of the tree trunks assumes an angle to the horizontal whose tangent is either the coefficient of static friction between tree trunks, or the coefficient of static friction between a tree trunk and the bunk, which èver is the lesser;
b) transporting the tree trunks to a desired unloading location, ` c) pivoting the bunk to rock the butt ends of the tree trunks down to contact the ground without any sliding of tree trunks with respect to each other or with respect to the bunk, d) halting the pivoting upon contact between the . .
butt ends and the ground, and e) moving the vehicle forwardly while maintaining ~ :
the ~unk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, whiIe the tree trunks remain in alignmen~.
GENERAL DESCRIPTION OF THE DRi~WINGS
.
One embodiment of an apparatus adapted to carry out the method of this invention is illustrated in the accompanying drawings, in which like numerals denote like .
.. . .. . .
1083S~7 parts throughout the several views, and in which:
Figure 1 is a perspective view of a simplified loader-forwarder ~dapted toicarry out the method of this invention;
Figures 2, 3 and 4 are sequential views showing sequential steps in the method of this invention; and Figures 5 and 6 are schematic diagrams showing the geometric considerations which enter into the method of this invention.
PARTICULAR DESCRIPTION OF THE DRAWINGS
In Figure 1 is shown a vehicle 10 which includes a front portion 12 and a rear portion 14 articulated together as is well known in large, all-terrain vehicles. The forward portion 12 contains the drive mechanism and controls, whereas the rearward portion 14 supports a bunk 16 which is pivotally mounted at an axis 18 with respect to the rearward portion 14 of the vehicle 10. The vehicle would normally also include either an articulated loading arm or an articu-lated felling and loading arm. These additional mechanisms do not relate in any way to this invention, and have been -omitted for the sake of simplifying the drawing.
As can be seen in Figure 2, a hydraulic cylinder 20 has its lower end 22 pivotally mounted to the rearward portion 14 of the vehicle 10, and has its upper end 23, which is secured to the hydraulic piston, pivoted to the bunk 16 at a location forwardly displaced from the location of the pivotal axis 18.
The bunk includes a substantially flat tree-supporting surface (not visible in Figure 1 as it is covered with tree trunks), from the side edges of which short .
:~t33537 side walls 25 are upstanding. Extending upwardly and out-wardly at an angle from each side wall 25 are three posts ~7. As is obvious, the function of the posts is to retain a substantial number of tree trunks on the bunk.
Finally, the vehicle 10 includes an operator's cab 30, and the usual deep-tread tires 32.
As can be seen in Figure 2, a plurality of tree trunks 34 are contained upon the bunk 16 with the butt ends 36 in substantial vertical alignment and project-ing to the rear of the bunk 16. It is also clear that the bunk is spaced above the ground level 38 and it will be understood that in the operation of pivoting the bunk in the clockwise direction as seen in Figure 2 by extending the hydraulic cylinder 20, the butt ends of the lowexmost tree trunks will follow the tra~ectory shown by the broken-line arrow identified by the numeral 40 in Figure 2.
The essence of the method of this invention is to ensure that the butt ends 36 of the trees 34 are sufficiently far to the rear with respect to the pivotal axis 18, having .
regard to the closeness of the bunk to the ground, that, :
upon pivotal motion of the bunk 16 to rock the butt ends of the tree trunks down to the ground, the butt ends will contact the ground before any of the tree trunks begin to slide, either with respect to each other, or with respect to the bunk.
In more technical language, these conditions are met by ensuring that the butt ends of the trees are sufficiently far to the rear with respect to the pivotal axis 18 that, as the bun~ rocks clockwise (as seen in Figure
2) to bring the tree trunks down to the yround, contact , .- , ~ ,. . .. .
~8~537 between the butt ends and the ground takes place before any of the tree trunks assumes an angle to the horizontal whose tangent is either the coef~icient of static Exiction between tree trunks, or the coefficient of static friction between a tree trunk and the bunk, which ever is the lesser.
This will ensure that the tree trunks will contact the ground at their butt ends in the configuration shown in Figure 3, with none of the tree trunks sliding either with respect to each other or with respect to the bunk 16. Upon achieving the position of Figure 3, the operator then slowly drives the vehicle forwardly, so that the contact between the butt ends of the trees and the ground will exert a drag or restraint on the trees, whereby the bunk can, in effect, be withdrawn out from under the trees. Figure 4 shows the vehicle 10 after a certain . ..
degree of travel, almost to the point where the top ends :
` of the tree trunks will clear the bunk 16.
Thus, the method of this invention involves firstly ~.
loading the tree trunks onto the bunk in accordance with the criteria set out earlier and described with reerence to Figure 2, then transporting the tree trunks to a desired unloading location, then pivoting the bunk to rock the : butt ends of the tree trunks.down to contact the ground with-out any sliding of the tree trunks with respect to each : other or with respect to the bunk, then halting the pivoting upon contact between the butt ends and the ground, and . ~inally moving the vehicle forwardly while maintaining the bunk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, while thc tree tranks remain in ' ~Lo~335~7 alignment.
The geometry of the criter a which technically define the method herein described is iliustrated in Figures 5 and 6, to which attention is now directed.
In Figure 5, a rear wheel 32 is illustrated and the line 38 is again the ground level. The point P in Figure 5 represents the pivotal axis which is shown at 18 in Figure 2. The distance x between the points P
and M represents the height of the pivotal point P above the ground. The height x is also illustrated in Figure 2.
The distance z between the points P and N represents the perpendicular distance from the pivot point P to the sur-face of the bunk which contacts the lowermost tree trunks.
The surface is identified in Figure 5 by the numeral 42.
A portion o~ one of the lowermost tree trunks is sho,wn in Figure 5 at the numeral 43, this being the rearward or butt-end portion. The line y extending between the points P
and O is the distance between the pivot axis and the reaxmost end point of the lower tree trunks. The broken line 40 in Figure S again represents the trajectory of the butt ends of the lowermost tree trunks as the bunk pivots about the axis 18 (point P in Figure 5). Thus, the line 40 is merely a circular arc whose centre is at the point P.
The point T is the intersection of the arc 40 with the ground level 38, and it thus follows that the di~tance between P and T must be the same as the distance between P and O. Thus, both PO and PT represent the distance ~.
The angle c~ represents ~ PTM, while the ~ngle represents G PON.
When ehe bunk has p~voted to as.sume the position ~
.'".
' . . . .. .. . .. . . . .
~8~5~7 shown in Figure 3, with the butt ends of the lowermost tree trunks resting against the ground level 38, the angles o~
and ~ have come together to define theirsum, which is identified in Figure 6 as the angle ~r In effect, the points O and T are now superimposed in Figure 6.
Having defined the various lengths involved with the method herein described, the condition under which the sliding of the trees is avoided will be satified if the following condition i5 met:
sin~l z + sin~l x Y Y
, where ~ i5 the lesser of:
1) the angle whose tangent is the coefficient of static friction between tree trunks, ~`
2) the angle whose tangent is the coefficient of static friction between a tree trunk and the trunk-contacting surface of the bunk.
(The above formula utilizes the standard trigono-metric designation of sin 1 to indicate "the angle whose sine is").
As an example of typical coefficients of static friction which are encountered in the field to which this invention relates, reference may be had to Marks' Mechanical Engineer's Handbook, 6th edition, 1958, McGraw-Hill Book Company Inc., page 3-40, where coefficients of static and sliding friction are given for various materials.
- The coefficient of static friction for oak on oak is given -as .62 where the force promoting slidiny is parallel to the grain, and .54 where the force promoting sliding is perpendicu-lar to the grain.
The same table gives the coefficient of .sliding _9_ .
1~835~7 friction for cast iron on oak is . 49, and since the coef~ic-ient of sliding friction is always less than the coefficient of static friction, it is reasonable to assume a coefficient of static friction for cast iron on oak in the region of about .6.
In order to initiate the sliding of a given item over a surface under its own weight as the surface gradually tilts away from the horizontal, the angle made by the surface with the horizontal must reach a point where its tangent is the same as the coefficient of static friction between the materials of the surface and of the article.
Taking an approximate coefficient of static friction for the tree trunks with respect to each other and with respect to the bunk in the area of .6, it is a simple matter to deter-mine that sliding of some form is likely to be initiated at around an angle of 30 to the horizontal.
The angle shown in Figure 3, at which contact takes place between the butt ends of the trees and the ground, is in the area of 25, this being considered a "safe" maximum angle with respect to the horizontal. It will be understood, however, that it is not feasible to establish a definite maximum angle to the horizontal, for the simple reason that t~e coefficients of friction between different tree materials and tree conditlons will vary to some extent.
: .
7,' - .: . . - - , . ~ : .
~8~537 between the butt ends and the ground takes place before any of the tree trunks assumes an angle to the horizontal whose tangent is either the coef~icient of static Exiction between tree trunks, or the coefficient of static friction between a tree trunk and the bunk, which ever is the lesser.
This will ensure that the tree trunks will contact the ground at their butt ends in the configuration shown in Figure 3, with none of the tree trunks sliding either with respect to each other or with respect to the bunk 16. Upon achieving the position of Figure 3, the operator then slowly drives the vehicle forwardly, so that the contact between the butt ends of the trees and the ground will exert a drag or restraint on the trees, whereby the bunk can, in effect, be withdrawn out from under the trees. Figure 4 shows the vehicle 10 after a certain . ..
degree of travel, almost to the point where the top ends :
` of the tree trunks will clear the bunk 16.
Thus, the method of this invention involves firstly ~.
loading the tree trunks onto the bunk in accordance with the criteria set out earlier and described with reerence to Figure 2, then transporting the tree trunks to a desired unloading location, then pivoting the bunk to rock the : butt ends of the tree trunks.down to contact the ground with-out any sliding of the tree trunks with respect to each : other or with respect to the bunk, then halting the pivoting upon contact between the butt ends and the ground, and . ~inally moving the vehicle forwardly while maintaining the bunk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, while thc tree tranks remain in ' ~Lo~335~7 alignment.
The geometry of the criter a which technically define the method herein described is iliustrated in Figures 5 and 6, to which attention is now directed.
In Figure 5, a rear wheel 32 is illustrated and the line 38 is again the ground level. The point P in Figure 5 represents the pivotal axis which is shown at 18 in Figure 2. The distance x between the points P
and M represents the height of the pivotal point P above the ground. The height x is also illustrated in Figure 2.
The distance z between the points P and N represents the perpendicular distance from the pivot point P to the sur-face of the bunk which contacts the lowermost tree trunks.
The surface is identified in Figure 5 by the numeral 42.
A portion o~ one of the lowermost tree trunks is sho,wn in Figure 5 at the numeral 43, this being the rearward or butt-end portion. The line y extending between the points P
and O is the distance between the pivot axis and the reaxmost end point of the lower tree trunks. The broken line 40 in Figure S again represents the trajectory of the butt ends of the lowermost tree trunks as the bunk pivots about the axis 18 (point P in Figure 5). Thus, the line 40 is merely a circular arc whose centre is at the point P.
The point T is the intersection of the arc 40 with the ground level 38, and it thus follows that the di~tance between P and T must be the same as the distance between P and O. Thus, both PO and PT represent the distance ~.
The angle c~ represents ~ PTM, while the ~ngle represents G PON.
When ehe bunk has p~voted to as.sume the position ~
.'".
' . . . .. .. . .. . . . .
~8~5~7 shown in Figure 3, with the butt ends of the lowermost tree trunks resting against the ground level 38, the angles o~
and ~ have come together to define theirsum, which is identified in Figure 6 as the angle ~r In effect, the points O and T are now superimposed in Figure 6.
Having defined the various lengths involved with the method herein described, the condition under which the sliding of the trees is avoided will be satified if the following condition i5 met:
sin~l z + sin~l x Y Y
, where ~ i5 the lesser of:
1) the angle whose tangent is the coefficient of static friction between tree trunks, ~`
2) the angle whose tangent is the coefficient of static friction between a tree trunk and the trunk-contacting surface of the bunk.
(The above formula utilizes the standard trigono-metric designation of sin 1 to indicate "the angle whose sine is").
As an example of typical coefficients of static friction which are encountered in the field to which this invention relates, reference may be had to Marks' Mechanical Engineer's Handbook, 6th edition, 1958, McGraw-Hill Book Company Inc., page 3-40, where coefficients of static and sliding friction are given for various materials.
- The coefficient of static friction for oak on oak is given -as .62 where the force promoting slidiny is parallel to the grain, and .54 where the force promoting sliding is perpendicu-lar to the grain.
The same table gives the coefficient of .sliding _9_ .
1~835~7 friction for cast iron on oak is . 49, and since the coef~ic-ient of sliding friction is always less than the coefficient of static friction, it is reasonable to assume a coefficient of static friction for cast iron on oak in the region of about .6.
In order to initiate the sliding of a given item over a surface under its own weight as the surface gradually tilts away from the horizontal, the angle made by the surface with the horizontal must reach a point where its tangent is the same as the coefficient of static friction between the materials of the surface and of the article.
Taking an approximate coefficient of static friction for the tree trunks with respect to each other and with respect to the bunk in the area of .6, it is a simple matter to deter-mine that sliding of some form is likely to be initiated at around an angle of 30 to the horizontal.
The angle shown in Figure 3, at which contact takes place between the butt ends of the trees and the ground, is in the area of 25, this being considered a "safe" maximum angle with respect to the horizontal. It will be understood, however, that it is not feasible to establish a definite maximum angle to the horizontal, for the simple reason that t~e coefficients of friction between different tree materials and tree conditlons will vary to some extent.
: .
7,' - .: . . - - , . ~ : .
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of handling a plurality of delimbed tree trunks, which comprises the steps:
a) loading the tree trunks on a bunk pivotally mounted on a transport vehicle with the butt ends of the tree trunks in substantial alignment and projecting to the rear of the bunk, the bunk being spaced above the ground and being pivotal about an axis transverse to the direction of motion of the vehicle, the butt ends being sufficiently far to the rear and the bunk being sufficiently close to the ground that, upon pivotal motion of the bunk to rock the butt ends of the tree trunks down to the ground, contact between the butt ends and the ground takes place before any of the tree trunks assumes an angle to the horizontal whose tangent is either the coefficient of static friction between tree trunks, or the coefficient of static friction between a tree trunk and the bunk, which ever is the lesser;
b) transporting the tree trunks to a desired unloading location, c) pivoting the bunk to rock the butt ends of the tree trunks down to contact the ground without any sliding of tree trunks with respect to each other or with respect to the bunk, d) halting the pivoting upon contact between the butt ends and the ground, and e) moving the vehicle forwardly while maintaining the bunk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, while the tree trunks remain in alignment.
a) loading the tree trunks on a bunk pivotally mounted on a transport vehicle with the butt ends of the tree trunks in substantial alignment and projecting to the rear of the bunk, the bunk being spaced above the ground and being pivotal about an axis transverse to the direction of motion of the vehicle, the butt ends being sufficiently far to the rear and the bunk being sufficiently close to the ground that, upon pivotal motion of the bunk to rock the butt ends of the tree trunks down to the ground, contact between the butt ends and the ground takes place before any of the tree trunks assumes an angle to the horizontal whose tangent is either the coefficient of static friction between tree trunks, or the coefficient of static friction between a tree trunk and the bunk, which ever is the lesser;
b) transporting the tree trunks to a desired unloading location, c) pivoting the bunk to rock the butt ends of the tree trunks down to contact the ground without any sliding of tree trunks with respect to each other or with respect to the bunk, d) halting the pivoting upon contact between the butt ends and the ground, and e) moving the vehicle forwardly while maintaining the bunk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, while the tree trunks remain in alignment.
2. In a method of handling a plurality of delimbed tree trunks, the steps of:
a) providing a transport vehicle having a loading bunk with a substantially flat tree trunk supporting surface, the bunk being pivotally mounted to the vehicle about a horizontal axis transverse to the direction of travel of the vehicle, the axis being at a distance x from the ground, the flat tree trunk supporting surface being a distance z from the axis as measured along a line perpendicular to the surface, loading the tree trunks on the bunk with their butt ends substantially in alignment and projecting to the rear of the bunk sufficiently far that the distance y from the said axis to the butt ends of the bottom tree trunks satis-fies the equation:
where .delta. is the lesser of:
1) the angle whose tangent is the coefficient of static friction between tree trunks, 2) the angle whose tangent is the coefficient of static friction between a tree trunk and said tree trunk supporting surface;
b) transporting the tree trunks to a desired unloading location, c) pivoting the bunk to rock the butt ends of the tree trunks down to contact the ground without any sliding of tree trunks with respect to each other or with respect to the bunk, d) halting the pivoting upon contact between the butt ends and the ground, and e) moving the vehicle forwardly while maintaining the bunk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, while the tree trunks remain in alignment.
a) providing a transport vehicle having a loading bunk with a substantially flat tree trunk supporting surface, the bunk being pivotally mounted to the vehicle about a horizontal axis transverse to the direction of travel of the vehicle, the axis being at a distance x from the ground, the flat tree trunk supporting surface being a distance z from the axis as measured along a line perpendicular to the surface, loading the tree trunks on the bunk with their butt ends substantially in alignment and projecting to the rear of the bunk sufficiently far that the distance y from the said axis to the butt ends of the bottom tree trunks satis-fies the equation:
where .delta. is the lesser of:
1) the angle whose tangent is the coefficient of static friction between tree trunks, 2) the angle whose tangent is the coefficient of static friction between a tree trunk and said tree trunk supporting surface;
b) transporting the tree trunks to a desired unloading location, c) pivoting the bunk to rock the butt ends of the tree trunks down to contact the ground without any sliding of tree trunks with respect to each other or with respect to the bunk, d) halting the pivoting upon contact between the butt ends and the ground, and e) moving the vehicle forwardly while maintaining the bunk in the position at which it stopped pivoting, to allow the tree trunks to be dragged fully off the bunk due to the contact with the ground, while the tree trunks remain in alignment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA313,381A CA1083537A (en) | 1978-10-13 | 1978-10-13 | Method of handling harvested trees |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA313,381A CA1083537A (en) | 1978-10-13 | 1978-10-13 | Method of handling harvested trees |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1083537A true CA1083537A (en) | 1980-08-12 |
Family
ID=4112603
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA313,381A Expired CA1083537A (en) | 1978-10-13 | 1978-10-13 | Method of handling harvested trees |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1083537A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1659026A1 (en) * | 2004-11-18 | 2006-05-24 | General Electric Company | Transport device for an elongate object such as a rotor blade for a wind turbine or the like |
-
1978
- 1978-10-13 CA CA313,381A patent/CA1083537A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1659026A1 (en) * | 2004-11-18 | 2006-05-24 | General Electric Company | Transport device for an elongate object such as a rotor blade for a wind turbine or the like |
| US8226342B2 (en) | 2004-11-18 | 2012-07-24 | General Electric Company | Transport device for an elongate object such as a rotor blade for a wind turbine or the like |
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