CA1179982A - Boom extension for crane - Google Patents
Boom extension for craneInfo
- Publication number
- CA1179982A CA1179982A CA000402675A CA402675A CA1179982A CA 1179982 A CA1179982 A CA 1179982A CA 000402675 A CA000402675 A CA 000402675A CA 402675 A CA402675 A CA 402675A CA 1179982 A CA1179982 A CA 1179982A
- Authority
- CA
- Canada
- Prior art keywords
- boom extension
- boom
- chord
- chord members
- extension
- 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
- B66—HOISTING; LIFTING; HAULING
- B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
- B66C23/00—Cranes comprising essentially a beam, boom, or triangular structure acting as a cantilever and mounted for translatory of swinging movements in vertical or horizontal planes or a combination of such movements, e.g. jib-cranes, derricks, tower cranes
- B66C23/62—Constructional features or details
- B66C23/64—Jibs
- B66C23/70—Jibs constructed of sections adapted to be assembled to form jibs or various lengths
- B66C23/701—Jibs constructed of sections adapted to be assembled to form jibs or various lengths telescopic
- B66C23/702—Jibs constructed of sections adapted to be assembled to form jibs or various lengths telescopic with a jib extension boom
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Jib Cranes (AREA)
Abstract
BOOM EXTENSION FOR CRANE
Abstract of the Disclosure A lattice type boom extension for a crane boom comprises a pair of laterally spaced apart elongated tubular top chord members which are of lesser diameter, wall thick-ness and weight than similar bottom chord members so as to reduce weight and cost of the boom extension without reducing strength and load-handling ability.
Abstract of the Disclosure A lattice type boom extension for a crane boom comprises a pair of laterally spaced apart elongated tubular top chord members which are of lesser diameter, wall thick-ness and weight than similar bottom chord members so as to reduce weight and cost of the boom extension without reducing strength and load-handling ability.
Description
~79~
BOOM EXTENSION FOR CRANE
Background of the Invention Field of Use This invention relates generally to lattice type boom extensions for crane boorns~
Description of the Prior ALt Some cranes are constructed so that the length of the crane boom can be extended to suit particular job needs by temporary attachment of a boom extension to the point end of the crane boom. Typically, such boom exten-sions are lattice-type structures in order to keep weight to a minimum. Furthermore, in the current state of the art, the lattice boom extensions have often been designed as cable-supported jibs wherein the top and bottom tubular chord members had the same outside tube diameter and tube wall thickness.
The dominant load on such cable supported lattice structures is axial compression. Both chords bottom and top are in compression. The bending moments resulting from self-weight and eccentric tip support are usually small compared to the direct axial load. These cable supported jib structures act almost as a pure columns and the beam load effects are relatively unimportant. Based on this mode of loading the top and bottom chords are typically made to the same outside diameter. However, as crane ~ooms and extension booms are made longer and larger to suit current construction industry needs, the equal size chord jib design of the aforesaid character becomes inefficient and unnecessarily heavy for long and highly-loaded extensions, and improved boom extension are required.
Summary of the Invention Applicant has discovered through study, experimentation and tests that, unlike conventional cable-supported lattice type boom extensions, a lattice type boom extension, unsupported by cables and mounted on a crane boom which swings around (such as on a mobile crane) is subjected to a combination of axial compression and bending and, hence, is acting as a beam column and that load-ing of this type is significantly different from that in cable-supported structures.
The invention provides in a non-cable supported lattice type boom extension for releasable attachment to the point end of a crane boom, said boom extension comprising a base end, a point -end, top, bottom and lateral sides, and a centerline extending between said base end and said point end of said boom extension, said centerline and said top and bottom sides being disposed at an acute angle to vertical when said boom extension i5 supporting a load whereby said bottom boom chord members of said boom extension are subjected to greater axial compression than said top chord members and to bending forces, in combination: a pair of tubular top chord members and a pair of tubular bottom chord members on the top and bottom sides, respectively, of said boom extension, the chord members in each pair being laterally spaced apart from each other and converging toward each other in proceeding from said base end to said point end of said boom extension, the top chord member and the bottom chord member on the same lateral side of said boom extension converging toward each other in proceeding from said base end to said point end of said boom extension, the chord members in a respective pair being of the same size relative to each other as regards outside diameter and wall thickness, each of said bottom chord members being larger in outside diameter and having a greater wall thickness than each of said top chord members, the longitudi-nal centerlines of the top and bottom chord members on the same lateral side of said boom extension lying in a common vertical plane; cross braces interconnected between the two chord members in each pair and between each top chord member and its respective bottom chord member; means near the base end of said boom extension for releasably connecting the base end of each chord member to the point end of said crane boom; and a hoist line pulley rotatably mounted near said point end of said boom extension.
A boom extension constructed and used in accordance with the present invention offers several advantages over the prior art.
For example, in an actual embodiment of an extension on the order of 42 feet long, tests showed that the weight saving was approxi-mately 200 pounds. Considering that the material for the cord tubing is quite expensive, the smaller weight more than adequately off-sets the higher manufacturing cost resulting from fabricating different lengths for top and bottom laces or cross-members.
Drawings Figure 1 is a side elevational view of a mobile crane showing its telescopic boom fully extended and provided with a boom extension in accordance with the invention at its upper or point end;
Figure 2 is a greatly enlarged side elevational view of the extension shown in Figure 1 and also shows force-diagrams associated therewith;
-4a-_5_ li Figure 3 is an enlarged top plan view (with Portions broken awaY) of the boom extension of Fiqures 1 and 2;
Figure 4 is a side elevational view of the boom extension of Fiqure 3;
Fiqure 5 is a cross-sectional view of the boom extension taken on line 5-5 of Figure 4 on an enlarged scale;
Figure 6 is a cross-sectional view of the boom extension taken on line 6-6 of Figure 4 on ar.enlarged scale; and Figure 7 is a cross-sectional view of the boom extension taken on line 7-7 of Figure 4 on an enlarged scale.
Description of a Preferred Embodiment Figure 1 is a side elevational view of a mobile crane 10 having a lower section, including a chassis 11 on which ground engaging wheels 12, outriggers 13 and an oper-ator's cab 14 are mounted, and having a rotatable upper section including a machinery housing 16 on which an oper-ator's cab 17, a multisection telescopic boom 18, boom hoist cylinder 19, and a cable winch 20 are mounted.
Figure 1 shows the outriggers 13 extended so as to raise mobile crane 10 off its wheels and also shows boom hoist cylinder 19 extended to raise boom 18. Telescopic boom 18 is also shown as fully extended.
Figures 1 and 2 show that boom 18 is provided at its uppermost or point ena with a boom head 22 of conven-tional construction which is understood to comprise two laterally spaced apart side plates, such as plate 23, between which a pair of rotatable or hoist line cable pulleys 24 I -6- ~1 and 25 aré rotatably mounted. Each plate 23 is understood to be provided with two support members or pins, not shown, which are releasably engageable with clevises, hereinafter identified, on the base end of a boom extension 26 in accord-ance with the invention, which is shown in Figs. 1 and 2 asmounted on the point end of boom 18. Boom extension 26 is provided at its point end with an extension head 27 having a rotatable cable or hoist line pulley 28 around which a cable 30 from winch 20 is reeved, such cable being provided with a load-handling hook 31.
As Figures 1-7 show, extension 26 is of the lattice type which comprises four sides ~namely, a top side 31, a bottom side 32, a right side 33 and a left side 34) and which tapers to reduced dimensions, proceeding from its base end to its point end. Extension 26 comprises four elongated tubular chord members designated 35, 36, 37 and 38 which are interconnected by lacing or cross braces hereinafter described. The cord members 35 and 36, herein designated as top chord members are arranged in laterally spaced apart side-by-side converging relationship. The chord members 37 and 38, herein designated as bottom chord members, are also arranged in laterally spaced apart side-by-side converging relationship. The center lines of the bottomchord m ~ ers 37 and 38 lie in a vertical plane directly below the center lines of the top chord members 35 and 36, respectively.
The top chord members 35 and 36 are interconnected with each other by cross braces which are welded therebetween and arranged in a conventional manner i.e., some cross braces ~7- 1l being arranged at right angle~ to the chord members and others at acute angles, such as the braces 40 and 40A
respectively. The bottom chord members 37 and 38 are inter-connected with each other by welded cross braces (see Figs. 3, 5, 6, 7) such as 41 and 41A, respectively. Each top chord member 35, 36 is interconnected with a corresponding bottom chord member 37, 38, respectively, by welded cross braces (see Figs. 4, 5, 6, 7) such as 42 and 42A. As Figures 5, 6, 7 best show, each top chord member 35, 36 is also inter-connected at intervals therealong by internal braces such as 43, 44, respectively, with an opposite side bottom chord memJ~er 38, 37, respectively. Gusset plates 50 and 51 are provided at the base and of appropriate configuration and size point ends, respectively, of boom extension 26 to afford necessary strength and rigidity. As hereinbefore mentioned, four clevises 55, 56, 57 (not visible) and 58 are provided at the base end of 3~oom extension 26, being connection as by welding at the base ends of the chord members 35, 36, 37, 38, respectively.
As Figures 2 and 4 s~w, the largest unsupp~rte chord length along any bottom ch~rd rn~er 37, 38 may be on the order of about 1096 of the total length of the boom extension 26, depending on the si e of the bottam chord. UnsuP~orted chord len~th is that distance alon~ a member 3? or 38 between the connection ~oints of ~ cross braces (such as 42 and 42A, for exam~le~. The actual formula for the unsupported chord length is KL ~ 50.
In accordance with the invention, the top chord members 35, 36 have the same outside diameter and wall thickness as each other. Sin~larly, the ~ttom chord members 37, 38 have the same outside diameter and wall thickness as each other.
However, the wall thickness of a bottom chord member is greater th~n that of a top chord me~ber7 as is the outside tube diameter. The purpose of this disfference is to reduce weight and cost of the jib 26 ~ithout reducing strength and load handling ability. More specifically, in an actual symetrical em~xbnent of the invention which was built and tested, the b~om e~tension 26, fab~icated of c~ drawn, heat treated alloy 100,000 P.S.I. yield type steel chord members, and cross m~s of low carbon high yie]d electric resistance welded, 55,000 P.S.I. yield, had the followqng dim~ns~ns:
length. . ~ . . . . . . . . . . . . 42 feet base width. . . . . . . . . . . . . 3 feet base height . . . . . . . . . . . . 4 feet, 9 inches point width . . . . . . . . . . . . 1 foot, 4 inches point height. . . . . . . . . . . . 0 foot, 10.56 inches bottom chord O~D. . . . . . . . . 3.25 inches bottom chord wall thickness . . . . .188 inches top chord O.D. . . . . . . . . . . 2.5 inches top chord wall thickness. . . . . . .156 inches maximum unsupported chord length been ~race attachment poi~ts. . . 46 inches As the elementary two-plane force diagram F in Figure 2 shows, with its longitudinal center line the boom extension 26 was disposed at an angle oC of 15 from the vertical. A load of 30,000 pounds was disposed on hook 31, which imposed a load of 15,000 pounds on load line 30 between winch 20 and pulley 28. Boom deflection, extension jib deflection and bending in lace or brace ioints is neglected in diagram F; nevertheless, the diagram illustrates the basic force and stress relationships between the top chords 35, 36 and the bottom chords 37, 38, respectively.
1~7~C3~2 The following simplified e~lculations, and a m~re sophisticated study made by finite element analysis in addition to testing confirmed the advantages of using diff~rent size top and ~ottcm chords in accordance with applicant's invention or discovery.
Calculations for Boom ~xtension Force on Top Chords:
1) Force Due to Vertical Load MR2 = = 57.18 x 15,000 +48.12 x Rl + 24.06 x OOS 15 (30,000) - 504 x Sin 15 (30,000) ~ = 2'43858i238-= 49,012~
BOOM EXTENSION FOR CRANE
Background of the Invention Field of Use This invention relates generally to lattice type boom extensions for crane boorns~
Description of the Prior ALt Some cranes are constructed so that the length of the crane boom can be extended to suit particular job needs by temporary attachment of a boom extension to the point end of the crane boom. Typically, such boom exten-sions are lattice-type structures in order to keep weight to a minimum. Furthermore, in the current state of the art, the lattice boom extensions have often been designed as cable-supported jibs wherein the top and bottom tubular chord members had the same outside tube diameter and tube wall thickness.
The dominant load on such cable supported lattice structures is axial compression. Both chords bottom and top are in compression. The bending moments resulting from self-weight and eccentric tip support are usually small compared to the direct axial load. These cable supported jib structures act almost as a pure columns and the beam load effects are relatively unimportant. Based on this mode of loading the top and bottom chords are typically made to the same outside diameter. However, as crane ~ooms and extension booms are made longer and larger to suit current construction industry needs, the equal size chord jib design of the aforesaid character becomes inefficient and unnecessarily heavy for long and highly-loaded extensions, and improved boom extension are required.
Summary of the Invention Applicant has discovered through study, experimentation and tests that, unlike conventional cable-supported lattice type boom extensions, a lattice type boom extension, unsupported by cables and mounted on a crane boom which swings around (such as on a mobile crane) is subjected to a combination of axial compression and bending and, hence, is acting as a beam column and that load-ing of this type is significantly different from that in cable-supported structures.
The invention provides in a non-cable supported lattice type boom extension for releasable attachment to the point end of a crane boom, said boom extension comprising a base end, a point -end, top, bottom and lateral sides, and a centerline extending between said base end and said point end of said boom extension, said centerline and said top and bottom sides being disposed at an acute angle to vertical when said boom extension i5 supporting a load whereby said bottom boom chord members of said boom extension are subjected to greater axial compression than said top chord members and to bending forces, in combination: a pair of tubular top chord members and a pair of tubular bottom chord members on the top and bottom sides, respectively, of said boom extension, the chord members in each pair being laterally spaced apart from each other and converging toward each other in proceeding from said base end to said point end of said boom extension, the top chord member and the bottom chord member on the same lateral side of said boom extension converging toward each other in proceeding from said base end to said point end of said boom extension, the chord members in a respective pair being of the same size relative to each other as regards outside diameter and wall thickness, each of said bottom chord members being larger in outside diameter and having a greater wall thickness than each of said top chord members, the longitudi-nal centerlines of the top and bottom chord members on the same lateral side of said boom extension lying in a common vertical plane; cross braces interconnected between the two chord members in each pair and between each top chord member and its respective bottom chord member; means near the base end of said boom extension for releasably connecting the base end of each chord member to the point end of said crane boom; and a hoist line pulley rotatably mounted near said point end of said boom extension.
A boom extension constructed and used in accordance with the present invention offers several advantages over the prior art.
For example, in an actual embodiment of an extension on the order of 42 feet long, tests showed that the weight saving was approxi-mately 200 pounds. Considering that the material for the cord tubing is quite expensive, the smaller weight more than adequately off-sets the higher manufacturing cost resulting from fabricating different lengths for top and bottom laces or cross-members.
Drawings Figure 1 is a side elevational view of a mobile crane showing its telescopic boom fully extended and provided with a boom extension in accordance with the invention at its upper or point end;
Figure 2 is a greatly enlarged side elevational view of the extension shown in Figure 1 and also shows force-diagrams associated therewith;
-4a-_5_ li Figure 3 is an enlarged top plan view (with Portions broken awaY) of the boom extension of Fiqures 1 and 2;
Figure 4 is a side elevational view of the boom extension of Fiqure 3;
Fiqure 5 is a cross-sectional view of the boom extension taken on line 5-5 of Figure 4 on an enlarged scale;
Figure 6 is a cross-sectional view of the boom extension taken on line 6-6 of Figure 4 on ar.enlarged scale; and Figure 7 is a cross-sectional view of the boom extension taken on line 7-7 of Figure 4 on an enlarged scale.
Description of a Preferred Embodiment Figure 1 is a side elevational view of a mobile crane 10 having a lower section, including a chassis 11 on which ground engaging wheels 12, outriggers 13 and an oper-ator's cab 14 are mounted, and having a rotatable upper section including a machinery housing 16 on which an oper-ator's cab 17, a multisection telescopic boom 18, boom hoist cylinder 19, and a cable winch 20 are mounted.
Figure 1 shows the outriggers 13 extended so as to raise mobile crane 10 off its wheels and also shows boom hoist cylinder 19 extended to raise boom 18. Telescopic boom 18 is also shown as fully extended.
Figures 1 and 2 show that boom 18 is provided at its uppermost or point ena with a boom head 22 of conven-tional construction which is understood to comprise two laterally spaced apart side plates, such as plate 23, between which a pair of rotatable or hoist line cable pulleys 24 I -6- ~1 and 25 aré rotatably mounted. Each plate 23 is understood to be provided with two support members or pins, not shown, which are releasably engageable with clevises, hereinafter identified, on the base end of a boom extension 26 in accord-ance with the invention, which is shown in Figs. 1 and 2 asmounted on the point end of boom 18. Boom extension 26 is provided at its point end with an extension head 27 having a rotatable cable or hoist line pulley 28 around which a cable 30 from winch 20 is reeved, such cable being provided with a load-handling hook 31.
As Figures 1-7 show, extension 26 is of the lattice type which comprises four sides ~namely, a top side 31, a bottom side 32, a right side 33 and a left side 34) and which tapers to reduced dimensions, proceeding from its base end to its point end. Extension 26 comprises four elongated tubular chord members designated 35, 36, 37 and 38 which are interconnected by lacing or cross braces hereinafter described. The cord members 35 and 36, herein designated as top chord members are arranged in laterally spaced apart side-by-side converging relationship. The chord members 37 and 38, herein designated as bottom chord members, are also arranged in laterally spaced apart side-by-side converging relationship. The center lines of the bottomchord m ~ ers 37 and 38 lie in a vertical plane directly below the center lines of the top chord members 35 and 36, respectively.
The top chord members 35 and 36 are interconnected with each other by cross braces which are welded therebetween and arranged in a conventional manner i.e., some cross braces ~7- 1l being arranged at right angle~ to the chord members and others at acute angles, such as the braces 40 and 40A
respectively. The bottom chord members 37 and 38 are inter-connected with each other by welded cross braces (see Figs. 3, 5, 6, 7) such as 41 and 41A, respectively. Each top chord member 35, 36 is interconnected with a corresponding bottom chord member 37, 38, respectively, by welded cross braces (see Figs. 4, 5, 6, 7) such as 42 and 42A. As Figures 5, 6, 7 best show, each top chord member 35, 36 is also inter-connected at intervals therealong by internal braces such as 43, 44, respectively, with an opposite side bottom chord memJ~er 38, 37, respectively. Gusset plates 50 and 51 are provided at the base and of appropriate configuration and size point ends, respectively, of boom extension 26 to afford necessary strength and rigidity. As hereinbefore mentioned, four clevises 55, 56, 57 (not visible) and 58 are provided at the base end of 3~oom extension 26, being connection as by welding at the base ends of the chord members 35, 36, 37, 38, respectively.
As Figures 2 and 4 s~w, the largest unsupp~rte chord length along any bottom ch~rd rn~er 37, 38 may be on the order of about 1096 of the total length of the boom extension 26, depending on the si e of the bottam chord. UnsuP~orted chord len~th is that distance alon~ a member 3? or 38 between the connection ~oints of ~ cross braces (such as 42 and 42A, for exam~le~. The actual formula for the unsupported chord length is KL ~ 50.
In accordance with the invention, the top chord members 35, 36 have the same outside diameter and wall thickness as each other. Sin~larly, the ~ttom chord members 37, 38 have the same outside diameter and wall thickness as each other.
However, the wall thickness of a bottom chord member is greater th~n that of a top chord me~ber7 as is the outside tube diameter. The purpose of this disfference is to reduce weight and cost of the jib 26 ~ithout reducing strength and load handling ability. More specifically, in an actual symetrical em~xbnent of the invention which was built and tested, the b~om e~tension 26, fab~icated of c~ drawn, heat treated alloy 100,000 P.S.I. yield type steel chord members, and cross m~s of low carbon high yie]d electric resistance welded, 55,000 P.S.I. yield, had the followqng dim~ns~ns:
length. . ~ . . . . . . . . . . . . 42 feet base width. . . . . . . . . . . . . 3 feet base height . . . . . . . . . . . . 4 feet, 9 inches point width . . . . . . . . . . . . 1 foot, 4 inches point height. . . . . . . . . . . . 0 foot, 10.56 inches bottom chord O~D. . . . . . . . . 3.25 inches bottom chord wall thickness . . . . .188 inches top chord O.D. . . . . . . . . . . 2.5 inches top chord wall thickness. . . . . . .156 inches maximum unsupported chord length been ~race attachment poi~ts. . . 46 inches As the elementary two-plane force diagram F in Figure 2 shows, with its longitudinal center line the boom extension 26 was disposed at an angle oC of 15 from the vertical. A load of 30,000 pounds was disposed on hook 31, which imposed a load of 15,000 pounds on load line 30 between winch 20 and pulley 28. Boom deflection, extension jib deflection and bending in lace or brace ioints is neglected in diagram F; nevertheless, the diagram illustrates the basic force and stress relationships between the top chords 35, 36 and the bottom chords 37, 38, respectively.
1~7~C3~2 The following simplified e~lculations, and a m~re sophisticated study made by finite element analysis in addition to testing confirmed the advantages of using diff~rent size top and ~ottcm chords in accordance with applicant's invention or discovery.
Calculations for Boom ~xtension Force on Top Chords:
1) Force Due to Vertical Load MR2 = = 57.18 x 15,000 +48.12 x Rl + 24.06 x OOS 15 (30,000) - 504 x Sin 15 (30,000) ~ = 2'43858i238-= 49,012~
2) Force Due to Side Load MR4 = 0 = .03 x 30,000 x 504 - 36 R3 R3 = R4 = 12,600 (Compr. R.H; Tension L.H) Force on I~p R.H. Chord Force on Top L.H. Chord 49,012 12,600 = 18,206# 49,012 + 12,600 = 30,806# (Tensin) (Tension) HIG~EST
Force on Bottom Chords:
.... . .
MR1 = 9.06 x 15,000 - 24.06 x Cos 15 (30,000) - 504 x Sin 15 (30,000) = 48.12 R2 R2 = 4474649 = 92 989~
Force on Bottom L.H. Chord ~orce on Bottom R.H. Chord 92,989 _ 12,200 = 40,195 92,989 + ___~ _ = 52,795#
(oompression) (aompression) HIG~ES~
Allowable compressive stress for bottom chord based on unsup~orted ch~rd length and yield strength of material (Yield = ~00 K.S.I.) L = 46 in K = 1.0 h = 1. 0847 1,~.7g~2 I`
= liOo8x446 = 42.4 Allowable Stress Fa = 45 350 K.S.I.
Allowable Tensile S1,^ess :EOL Top Chords Fa = .6 x 100 - 60.00 K.S.I.
S Assumed Chord Material and Mechanical Properties:
Bottom Chord: 3.25 in O.D. x .188 Wall A = 1.8930 in2 I = 2.1228 in4 S = 1.3063 in3 ~ = 1.0847 Top Chord: 2.50.D x .156 Wall A - 1.1505 in2 I = .7934 in4 S = .6437 in3 ~ = .8304 Nomenclature Rl; R2 ~ Vertical Reactions.
R3; R4 - Side Reactions.
MR2 ~ Moment About Reaction Point R2 MR4 - Moment About Reaction Point R4 L - Unsupporteci Chord Length K - Effective Length Factor - Radius of Gyration KL Slenderness Ratio Determining~the Allowable Compressive ~ Stress Usually Restricted to = 50 for Boom Extension Design Fa ~ Allowable Stress (Either Tension or Compression) A - Area of Chord Section I - Moment of Inertia of Chord Section 25 S - Section Modulus of Chord Section
Force on Bottom Chords:
.... . .
MR1 = 9.06 x 15,000 - 24.06 x Cos 15 (30,000) - 504 x Sin 15 (30,000) = 48.12 R2 R2 = 4474649 = 92 989~
Force on Bottom L.H. Chord ~orce on Bottom R.H. Chord 92,989 _ 12,200 = 40,195 92,989 + ___~ _ = 52,795#
(oompression) (aompression) HIG~ES~
Allowable compressive stress for bottom chord based on unsup~orted ch~rd length and yield strength of material (Yield = ~00 K.S.I.) L = 46 in K = 1.0 h = 1. 0847 1,~.7g~2 I`
= liOo8x446 = 42.4 Allowable Stress Fa = 45 350 K.S.I.
Allowable Tensile S1,^ess :EOL Top Chords Fa = .6 x 100 - 60.00 K.S.I.
S Assumed Chord Material and Mechanical Properties:
Bottom Chord: 3.25 in O.D. x .188 Wall A = 1.8930 in2 I = 2.1228 in4 S = 1.3063 in3 ~ = 1.0847 Top Chord: 2.50.D x .156 Wall A - 1.1505 in2 I = .7934 in4 S = .6437 in3 ~ = .8304 Nomenclature Rl; R2 ~ Vertical Reactions.
R3; R4 - Side Reactions.
MR2 ~ Moment About Reaction Point R2 MR4 - Moment About Reaction Point R4 L - Unsupporteci Chord Length K - Effective Length Factor - Radius of Gyration KL Slenderness Ratio Determining~the Allowable Compressive ~ Stress Usually Restricted to = 50 for Boom Extension Design Fa ~ Allowable Stress (Either Tension or Compression) A - Area of Chord Section I - Moment of Inertia of Chord Section 25 S - Section Modulus of Chord Section
Claims (2)
1. In a non-cable supported lattice type boom extension for releasable attachment to the point end of a crane boom, said boom extension comprising a base end, a point end, top, bottom and lateral sides, and a centerline extending between said base end and said point end of said boom extension, said centerline and said top and bottom sides being disposed at an acute angle to vertical when said boom extension is supporting a load whereby said bottom boom chord members of said boom extension are subjected to greater axial compression than said top chord members and to bending for-ces, in combination: a pair of tubular top chord members and a pair of tubular bottom chord members on the top and bottom sides, respectively, of said boom extension, the chord mem-bers in each pair being laterally spaced apart from each other and converging toward each other in proceeding from said base end to said point end of said boom extension, the top chord member and the bottom chord member on the same lateral side of said boom extension converging toward each other in proceeding from said base end to said point end of said boom extension, the chord members in a respective pair being of the same size relative to each other as regards out-side diameter and wall thickness r each of said bottom chord members being larger in outside diameter and having a greater wall thickness than each of said top chord members, the longitudinal centerlines of the top and bottom chord members on the same lateral side of said boom extension lying in a common vertical plane; cross braces interconnected between the two chord members in each pair and between each top chord member and its respective bottom chord member; means near the base end of said boom extension for releasably connecting the base end of each chord member to the point end of said crane boom; and a hoist line pulley rotatably mounted near said point end of said boom extension.
2. A lattice type boom extension according to claim 1 wherein said bottom chord members also have larger wall thickness than said top chord members.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US27705581A | 1981-06-24 | 1981-06-24 | |
| US277,055 | 1981-06-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1179982A true CA1179982A (en) | 1984-12-27 |
Family
ID=23059212
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000402675A Expired CA1179982A (en) | 1981-06-24 | 1982-05-11 | Boom extension for crane |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS582190A (en) |
| BR (1) | BR8203293A (en) |
| CA (1) | CA1179982A (en) |
| DE (1) | DE3223620A1 (en) |
| FR (1) | FR2508427A1 (en) |
| GB (1) | GB2100701B (en) |
| MX (1) | MX157503A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19721298C2 (en) | 1997-05-21 | 2001-09-06 | Mannesmann Sachs Ag | Hybrid travel drive for a motor vehicle |
| CN102398863A (en) * | 2011-07-05 | 2012-04-04 | 上海三一科技有限公司 | Support structure capable of improving jib bearing capacity and crane with the support structure |
| DE202022103551U1 (en) | 2022-06-27 | 2022-07-18 | Tadano Demag Gmbh | Boom section, boom and mobile crane herewith |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3109523A (en) * | 1960-09-01 | 1963-11-05 | Skytop Rig Co | Folding derrick |
| DE6804349U (en) * | 1968-10-28 | 1969-10-23 | Karl Kaesebahrer Gmbh Fa | JIB CRANE, IN PARTICULAR TRUCK CRANE |
| SE337089B (en) * | 1970-01-27 | 1971-07-26 | Linden Alimak Ab | |
| JPS5115859U (en) * | 1974-07-22 | 1976-02-05 | ||
| US3945333A (en) * | 1974-12-20 | 1976-03-23 | Harnischfeger Corporation | Means for storing and connecting jib for telescopic boom of mobile crane |
| US4141455A (en) * | 1977-07-14 | 1979-02-27 | Harnischfeger Corporation | Means for storing and connecting jib on telescopic crane boom |
| JPS6142304Y2 (en) * | 1979-09-27 | 1986-12-01 |
-
1982
- 1982-05-11 CA CA000402675A patent/CA1179982A/en not_active Expired
- 1982-05-12 GB GB08213740A patent/GB2100701B/en not_active Expired
- 1982-05-21 MX MX19281782A patent/MX157503A/en unknown
- 1982-06-04 BR BR8203293A patent/BR8203293A/en unknown
- 1982-06-23 JP JP10698782A patent/JPS582190A/en active Pending
- 1982-06-23 FR FR8210975A patent/FR2508427A1/en not_active Withdrawn
- 1982-06-24 DE DE19823223620 patent/DE3223620A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE3223620A1 (en) | 1983-01-13 |
| GB2100701B (en) | 1985-04-24 |
| FR2508427A1 (en) | 1982-12-31 |
| GB2100701A (en) | 1983-01-06 |
| JPS582190A (en) | 1983-01-07 |
| MX157503A (en) | 1988-11-28 |
| BR8203293A (en) | 1983-05-24 |
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Legal Events
| Date | Code | Title | Description |
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| MKEC | Expiry (correction) | ||
| MKEX | Expiry |