US3831770A

US3831770A - Snubbing frame for rotary cranes

Info

Publication number: US3831770A
Application number: US00312575A
Authority: US
Inventors: C Gottlieb; E Lewis
Original assignee: Diamondhead Corp
Current assignee: Diamondhead Corp
Priority date: 1972-12-06
Filing date: 1972-12-06
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27

Abstract

A self transportable system and method for placing full size, interiorly finished factory constructed housing units the system having as basic components, a vehicular rotary crane, a snubbing frame mountable on the crane to swing with the boom thereof, a load spreader to be handled by the crane during house placement operations and a transporter to position a housing unit relative to the crane and adapted to receive the spreader for site-to-site travel.

Description

United States Patent [191 Gottlieh et a1.

[ 1 Aug. 27, 1974 SNUBBING FRAME FOR ROTARY CRANES Prima Examiner-Allen N. Knowles 75] Inventors: C. Robert Gottlleb Mob1le,Ala.; Eugene C. Lewis S cotch Plains NJ. Asslstam [hammer-Larry Attorney, Agent, or Firm-Lane, Aitken, Dunner & [73] Assignee: Diamonhead Corporation, Zi

Mountainside, NJ.

[21] Appl' 312575 A self transportable system and method for placing full size, interiorly finished factory constructed hous- [52] U5. Cl 212/425, 212/44, 212/59 A, ing nits he system having as basic components, a ve- 52/745, 52/749 hicular rotary crane, a snubbing frame mountable on [51] Int. Cl. B66c 3/00 the cran t s ng i e o thereof, a load [58] Field of Search 212/41, 42, 42.5, 43, 44, Sp eader to be handled by the crane during house 212/45, 58 A, 59 A; 52/79, 745, 749; placement operations and a transporter to position a 214/392 housing unit relative to the crane and adapted to receive the spreader for site-to-site travel. [56] References Cited UNITED STATES PATENTS 15 19 Drawmg F'gures 2,914,312 11/1959 Cheesnian 212/59 A X i ,i- 1 I 1*: H I 1 A0 I42 a 102 P H0 [1 no 5 no --4; e.. i 1 7 I 112 L:1-. J J 24 6 I76 I 1 I H2 I76 a4 n4 "L 1 26 Q 356 Lg 2 356 1111, I8 as 48 46 326 20 22 44 44 22 st 20 5e PATENTED M182 7 I974 I sum 01 or 15 PATENIEUAummM sum 02 or 15 N mi wnm

III a PAIENIL MIC 2 7 1014 sum as 0f15 PATENTEB W82 7 I974 sum on or 15 PArimmusznan s w 'csur15 PAlEmimuszmu sum as nr 15 PATENTEW 3. 831

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sum #11 or 15 PATENTEBAUBNIBH SHEH 130F15 www ' l SNUBBING FRAME FOR ROTARY CRANES BACKGROUND OF THE INVENTION This invention relates to systems for placing factory prefabricated housing units on individual lot site foundations and more particularly, it concerns a novel method and apparatus providing a capability for positive and precise handling of the relatively large, heavy and delicate load represented by such housing units as well as for self transportability of equipment components of the apparatus between a plurality of individual lot sites in a land project under development.

In a co-pending application SerJNo. 163,935, filed July 19, 1971 by Eugene C. Lewis, C. Robert Gottlieb and Robert M. Macy and assigned to the assignee of the present invention, there is disclosed a method and apparatus for transporting prefabricated housing units from a factory in which the units are constructed to a remotely located land development project on which the units are to be placed permanently. In essence, the disclosed system contemplates factory prefabrication of mechanically operable, interiorly finished housing units using traditional building materials and structures, followed by the transfer of the units to a marine vessel such as a barge for transportation by water to a project terminal at the land project under development. At the project terminal, the units are transferred to pairs of elevated storage rails from which they may be picked up by a land vehicle or "transporter having a load bed capable of being positioned under the units on the elevated storage rails and raised to lift each unit from the rails for subsequent land travel to the individual lot site on which the unit is to be placed. The housing units manufactured and transported in this way may vary considerably in both size and design but to facilitate handling and transporting operations, a common width or joist span is employed in all units. To optimize versatility in interior floor plan design, a common width of 30 feet has been selected and units as long as 68 feet have been built and transported using the system without damage even though the units have included completely finished and painted dry wall interiors as well as operating fixtures such as ranges, refrigerators, dishwashers, lamp fixtures and the like.

Although the system disclosed in the aforementioned co-pending application has proven in practice to be highly effective in the handling and transporting such housing units from the factory to the particular lot on which a foundation has been erected to receive the housing unit, several problems were encountered in the transfer of a unit from a vehicular transporter to its final or ultimate position on the lot site foundation. For example, a mobile rotary crane was found to be the most versatile lifting and transfer mechanism to be used at individual lot sites, taking into account such factors as capability for operating in minimal areas of low overhead clearance due to trees, utility lines for example, lifting capacity, transportability, direct commerical availability and the like. Also it has been appreciated that because of the structural characteristics of the housing unit to be lifted and transferred, specifically its lack of inherent structural integrity and corresponding need for a continuous foundation-like support at all times in transit, a load lifting or handling spreader would be needed for the final transfer and placement operation. Although the spreader structures employed in transferring the housing units to the barge provided a solution to the achievement adequate strength to supply structural integrity to the housing unit, the combined weight of such a spreader and the housing unit could not be handled effectively by the rotary crane. Also and because of its required overall size, transportability of the spreader itself from lot site to lit site on the project under development had to be accounted for. Perhaps the most critical problem posed by the final transfer and placement operation was the handling of a load spreader both during movement into a load engaging position with respect to the house and during movement of the loaded spreader to a position by which the house would be set on the foundation. For example, it was found that although it was technically possible to position a housing unit. on a lot foundation using tag lines and the like, the lack of positive control over the crane suspended load made it exceedingly difficult to achieve placement of the house on the foundation with adequate precision.The slightest of breezes, for example, were found to have a critical adverse effect on achieving and retaining a proper horizontal orientation of the unit with respect tothe foundation for a long enough period of time so that it could be lowered gently onto the foundation.

The overall scheme of factory prefabrication of full size mechanically operable, interiorly finished housing units constructed with traditional building materials and transportation thereof largely by water from the location of the factory to the building project, all as disclosed in the aforementioned co-pending application Ser. No. 163,935, has therefore been found in practice to be a highly efficient and economically sound solution to the major problems of the housing industry. A need has been demonstrated, however, for improved techniques and equipment for the final positioning of such units on a foundation located :at the ultimate individual lot sites.

SUMMARY OF THE PRESENT INVENTION In accordance with the present invention, a system including novel procedures and apparatus is provided by which interiorly finished housing units having single floor areas as large as 30 by 68 feet and weighing as much as 67,000 pounds are effectively transferred from a vehicular transporter to a foundation or stacked on top of another such housing unit located at the individual lot sites of a land development project. The aforementioned problems encountered as a result of actual practice have been substantially overcome by an integrated system in which the position of the housing unit suspended from the hoist line of a conventional rotary crane is positively controlled with facility for adjustment so that the unit may be located within extremely close tolerances in a highly efficient manner. In a more specific sense, the system includes a novel load spreader capable not only of providing structural integrity to the housing unit during transfer but which is of minimal weight and capable of being readily transported both from lot site to lot site and also over land as a result of ease of disassembly. The positive control over the load represented by the housing units engaged by the spreader and suspended from a rotary crane boom is effected by an unique snubbing frame arrangement which adjustably anchors the load spreader and the housing unit in a horizontal reference plane with respect to the crane supported during transfer in conventional fashion on outrigger beams and jacks. In addition, the invention contemplates an unique method involving both the precise location of the component pieces of equipment to effect the ultimate transfer as well as the operation of those components during the transfer.

Among the objects of the present invention are therefore: the provision of a highly effective, integrated and self transportable system for placing full size, interiorly finished, factory prefabricated housing units on individual lot site foundations; the provision of such a system by which precise positive control of housing unit positions can be maintained throughout the complete transfer operation; the provision of an unique load spreader possessing both adequate strength to supply needed structural integrity to the housing unit during transfer as well as minimal weight and operating capabilities for effective handling during operation; the provision of an unique snubbing frame arrangement by which movement of the load spreader is precisely and accurately controlled during all phases of the operation; the provision of such a snubbing frame arrangement capable of positive adjustability thereby enabling a precise positioning of the housing unit with respect to a foundation; the provision of such a system capable of both placement of such housing units directly on foundations and also for stacking such housing units to provide multistory building structures; the provision of such a system which is self transportable in a highly efficient manner; the provision of an unique method for precisely positioning the individual crane and transporter components of the system in relation to a lot site foundation; the provision of a novel method for operating the components of the system to maximize efficiency of the transfer operation as well as facilitate movement of the system component from lot site to lot site.

Other objects and further scope of applicability of the present invention will become apparent to those skilled in the art from the detailed description of a preferred embodiment to follow and taken in conjunction with the accompanying drawings in which like parts are designated by the same reference numeral.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic plan view illustrating the general arrangement of system components of the present invention on a lot site and relative to a foundation to which a housing unit is to be transferred;

FIG. 2 is an enlarged fragmentary cross-section of the lot site and components illustrated in FIG. 1;

FIG. 3 is a cross-section similar to FIG. 2 but illustrating in more detail the structural organization of the system components of the present invention;

FIG. 4 is a side elevation showing the crane and spreader components of the house transfer system of the invention;

FIG. 5 is an enlarged fragmentary end elevation in partial cross-section illustrating the connection of the spreader to a crane snubbing frame of the invention and also the relative position of these components to a housing unit on a foundation as seen generally from line 5-5 of FIG. 4;

FIG. 6 is an enlarged fragmentary cross-section taken on line 6-6 of FIG. 3;

FIG. 7 is a fragmentary cross-section taken on line 77 of FIG. 6;

FIG. 8 is an enlarged fragmentary front elevation of the lower portion of the snubbing frame as seen generally on line 8-8 of FIG. 5;

FIG. 9 is an enlarged fragmentary end elevation illustrating in more detail, crane mounting parts of the snubbing frame, the overall assembly of these parts being shown in FIG. 3;

FIG. 10 is a fragmentary plan view in partial crosssection on line I0-I0 of FIG. 9 and further illustrating the crane mounting parts of the snubbing frame;

FIG. II is an exploded perspective view illustrating the structural parts of the load spreader component of this invention as well the general mode for connecting such parts;

FIG. 12 is an enlarged fragmentary end elevation of the load spreader of the invention with phantom line, illustrations of alternate positions to which it may be adjusted for movement on the house transferring vehicle or transporter component of the invention;

FIG. 13 is an enlarged fragmentary cross-section taken on line I3I3 of FIG. 12;

FIG. 14 is an enlarged fragmentary cross-section taken on line I4l4 of FIG. 13;

FIG. 15 is an enlarged fragmentary cross-section taken on line l5-l5 of FIG. I3;

FIG. 16 is a plan view of the load carrying bed on the transporter component of the invention with a phantom line illustration of the load spreader in position to lift and transfer a house therefrom;

FIG. 17 is an enlarged fragmentary cross-section taken on line 1717 of FIG. 16;

FIG. 18 is an enlarged side elevation in partial crosssection illustrating one of four spreader positioning devices mounted on the transporter component of the invention; and

FIG. 19 is an enlarged fragmentary cross-section taken on line 19-19 of FIG. 18.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT To facilitate an initial overall understanding of the system of the present invention, the components of equipment used in the system, as well as the method of house placement effected by the system, reference is first made to FIG. 3 of the drawings wherein a rotary or swinging boom vehicular crane generally designated by the reference numeral 10, is situated in operative relation to a permanent lot foundation 12 on which a housing unit I4 carries by a semitrailer-like vehicle or transporter I6 is to be placed. The crane, in itself, is a conventional, commerically available, heavy duty, truck crane to the extent that it includes a vehicular chassis 18 provided with usual outrigger beams 20 and stabilizing jacks 22, a cab 24 adapted to swing or rotate about a vertical axis 26 on a turntable 28 and having a boom 30 and hoisting line 32, the weight of the boom and load carried by the line 32 being balanced with a counterweight 34'. In accordance with the present invention, however, the crane 10 is equipped with a novel snubbing frame 36 which is connected by way of a vertical slide and adjustable linkage assembly 38 to one side of a load spreader designated generally by the reference numeral 40, all to be described in more detail below.

Although the transporter l6 incorporates structure having a direct correlation to and thus forming part of the system of the present invention, it will suffice for the present to note that the transporter generally includes a load carrying bed 42 supported at its rear end by a pair of multi-wheel trucks 44 each carryinga fifthwheel baring plate 46 adapted for vertical adjustability with respect to the track chassis 48 by virtue of a hydraulic jacking system (not shown). The forward end of the bed 42 is carried by a fifth-wheel tractor (not shown) also having a provision for vertical adjustability thereby completing a vertically adjustable three-point suspension by which the bed 42 may be raised, lowered or leveled. The latter of these operations is possible because each of the three points of suspension is vertically adjustable independent of the others.

At this point it will be apparent that with the house 14 located in the position illustrated in FIG. 3, and the crane l0 and spreader 40 in the positions illustrated in this figure, the house 14 may be transferred to the foundation 14 by first lifting the spreader 40 and house 14 upwardly off of the bed 42 of the transporter l6, swinging the boom 30 and spreader 40 from the solid-line position shown to a position over 'the foundation 12 as shown in phantom lines in FIG. 3, and the housing unit 14 lowered onto the foundation 14. While this operation would appear reasonably basic in terms of rotary crane operation, several very important factors must be accounted for to complete the operation in practice. In the first place, it will be borne in mind that the housing unit 14 to be handled may be a mechanically operable single story housing unit weighing as much as 67,000 lbs. and having dimensions as large as 30 feet in width and 68 feet in length. Moreover, the unit 14 preferably is completed finished interiorly with plaster or plasterboard walls and may incorporate a full complement of delicate equipment including lighting fixtures, thereby establishing a load not only of substantial weight and size, but also one which is extremely delicate. Moreover, to meet building code requirements applicable to conventional houses, the unit 14 must be placed on the foundation l2 within'extremely close tolerances; e.g., within one-fourth inch or less. It will be noted also that the slide and linkage assembly 38 effects a connection of the spreader 40 and the crane so that the housing 14 is at all times during its swinging movement from the transporter 16 to the foundation l4 positively or rigidly held in a generally prestablized horizontal orientation with respect to the crane 10. This positive or rigid connection between the load represented by the house 14 and the crane I0 is essential to avoid any possibility of the house swinging freely and erratically as a result of even the lightest winds or breezes, for example. While the linkage assembly 38 facilitates a measure of adjustability as will be apparent from the description to follow below, the connection thereof with the crane by the snubbing frame 36 establishes a relatively fixed swinging radius of the crane, thus requiring the crane I0 and also the transporter 16 to be accurately positioned with respect to the foundation I2.

The manner in which the crane l0 and transporter 16 are positioned accurately with respect to the founda tion 12 in accordance with the present invention may be understood by reference to FIGS. 1 and 2 of the drawings. In this respect, it will be appreciated that the foundation l2 will be permanently constructed on a lot most likely to form a part of a land subdivision to be developed by using the system of the present invention as well as that of the aforementioned copending application Ser. No. 163,935. In accordance with customary practice, the lot on which the foundation is constructed is laid out using conventional surveying techniques both to establish the boundary lines of the lot and the precise location on each lot of the foundation 12. In addition, earth grading operations are carried out in conjunction with the construction of the foundation. In accordance with the present invention, however, and because of the system thereof contemplates the transport of a substantially complete housing unit to each lot site with the aforementioned transfer of the housing unit to the constructed foundation, provision is made in the planning and construction of the foundation for the specific operative location of both the crane l0 and the transporter I6 as well as the route of access to that location in each instance. Hence, when the lot is graded to receive the foundation 12, it is graded also as neces sary to provide a transporter approach roadway and a crane approach roadway 52. Although these roadways are of a temporary nature, it has been found in practice that they should meet certain basic requirements to accommodate the components of the system. For example,the roadway 50 should provide a firm surface for the transporter tires using temporary steel mats as necessary to insure support of the loaded transporter. Also, the transverse slope 53 of the roadway should not exceed the limits of transport bed adjustability with respectto the wheels thereof in order that the bed 42 of the transporter can be adjusted to a truly level position.

Inasmuch as the crane roadway 52 need only accommodate the unloaded crane 10, the roadway 52 itself need not be made to meet any particular specifications other than those needed to enable movement of the unloaded crane. In this instance, however, inside and

outside mats

54 and 56 are placed in a proper relation with respect to the foundation in advance of the time the crane 10 is brought into position. The

mats

54 and 56 are positioned to underlie the pedestal jacks 22 on the crane thereby to provide a firm foundation for the crane It) on the outrigger beams 20 during the transfer operation.

An illustrative example of the relative horizontal location of the crane l0 and transporter 16 with respect to the foundation 12 is shown in FIGS. 1 and 2 of the drawings. The procedure used to achieve the relative locations of the crane and transporter with respect to the foundation is important to efficient use of the system of the invention and is correlated directly with the location and placement of the foundation 12 within preestablished dimensional tolerances to receive a particular housing unit 114 and meet existing building code requirements. Specifically the personnel who locate and place the foundation within such tolerances also place three aligned

crane location hubs

57, 58 and 59 taking care to meet the same relatively close tolerances as those applicable to the foundation. The line on which the hubs are located is parallel with the longitudinal center line 60 of the foundation 12 and is spaced from the center line 60 by a distance the same as the radial distance R between the hoist line or cable 32 and the swing axis 26. The radial distance R is selected by proper adjustment of the boom 30 in a vertical plane 61 including the swing axis 26 to be optimum for the crane 10 to lift the unit 14. In a more direct sense, the optimum radial distance R is predetermined by the geometry of the snubbing frame 36 and load spreader 40 though some measure of boom adjustment is contemplated to locate the cable 32 in line with the center of gravity of the unit 14 while the spreader is centered on the geometric center of the unit. It will be noted that the geometric center 62 of the foundation I2 and correspondingly the geometric center of the housing unit 14 are likely to be offset horizontally from the center of gravity of the unit. Inasmuch as the housing units are factory prefabricated according to plan specifications, the center of gravity may be calculated for each particular housing unit 14 to establish, for example, a dis tance 6 equal to the longitudinal distance between the longitudinal center of the unit and the center of gravity thereof. To correlate the location of unit center of gravity and the lifting plane of the boom 30, the central hub 58 is located at a point offset from the transverse axis 63 of the foundation by the distance e. Prior to moving the crane into position, the approach line of the crane is established by tying a string between the hubs 57-59 to a fourth hub 64. A plum chain 65 (FIG. 2) suspended on the swing axis of the crane will enable crane operating personnel to position the crane with reasonable accuracy over the hub 58. Having located the crane in this manner, the crane personnel may then locate additional hubs, 68 66 and to establish the transporter approach center line 50 as well as the ultimate position thereof which is optimum for the transfer operation. The location of the hub 68 may be determined simply by measuring the distance R from the hub 58 and selecting an optimum point on the are defined by the radius. The

hubs

66 and 70 are then set at a right angle to the plane 61. The transporter l6 and housing unit may then driven along the line 50 using plum chain 74 until the appropriate location is reached.

It might be noted that in the preceeding discussion, the offset distance e applies only to the longitudinal distance between the center of gravity and the geometric center of the housing unit 14. Obviously the center of gravity may also be displaced transversely of the geo metric center of the unit. Since this latter offset involves merely an adjustment of the angle of the boom 30 to change the radial distance R, it is not a factor in locating the crane along the line 52.

A more complete understanding of the snubbing frame 36 and slide and linkage assemly 38 may be had by reference to FIGS. 39 of the drawings. As shown most clearly in FIGS. 4, 7, 8 and 10, the snubbing frame 36 includes a pair of vertical guide posts 76 and 78 each having in addition to a main intermediate section 79, upper and lower

guide post extensions

80 and 82, respectively. The structure of both guide

posts

76 and 78 as well as the upper and

lower extensions

80 and 82 is the same throughout the total length of the posts and is illustrated in FIGS. 7 to include a tubular column 84 of rectangular cross-section and a laterally projecting guide flange or plate 86 welded or otherwise suitably secured to the front face of each column 84.

The guide posts 76 and 78 are securedly rigidly to each other near the lower end of the intermediate or main section 79 by a beam 88 illustrated most clearly in FIGS. 4, 8 and 10 of the drawings to include a pair of end sections 90 welded in cantilever fashion to the tubular column of each guide post and connected rigidly by bolted flange joints 92 to an intermediate beam section 94. To enable the boom 30 of the crane 10 to be lowered into a horizontal travelling position without interference by the snubbing frame 36, the beam 88 near the lower end of the guide posts 76 and 78 constitutes the sole direct interconnection of the guide posts thereby to define with the guide posts a generally U- shaped subassembly as may be seen in FIG. 4, for example. To provide necessary strength against bending or deflection of the relatively long vertical lever arm represented by the guide posts 76 and 78 about the ends of the beam 88, a pair of diagonal column struts 96 extend from bolted flange connections 98 on the top of the beam section 94 upwardly and outwardly to pin and weld connections (not shown) with the

posts

76 and 78 near the upper portion of the intermediate or main sections 79. Additionally tube structs 100 may extend between the column struts 96 to the guide posts 76 and 78, as shown in FIG. 8 of the drawings to lend structural integrity to the

posts

76, 78 and the struts 96 as units such as when the snubbing frame is disassembled.

The guide post subassembly thus defined by the guide posts 76 and 78, the beam 88 and struts 96 is supported from the rotatable cab 24 of the crane 10 by a system of struts illustrated most clearly in FIGS. 3, 9 and 10 of the drawings. Thus, a pair of struts 102 extend from clevis pin connections 104 with gusset plates 106 welded or otherwise secured to the rear of the guide posts 76, 78 near the upper end of the intermediate or main sections 79, rearwardly to clevis-pins 108 for connection to opposite ends of a beam 110 secured by brackets 11] to the top of the counterweight 34 on the crane cab 24. Compression struts I12 extend in similar fashion between the gusset plates 106 and a bracket 114 bolted or otherwise suitably fixed to the front end of the cab 24 near the base of the boom 30. To restrain pivotal movement of the

posts

76 and 78 about a point represented by the gusset plates 106, a pair of compression-tension struts ll6 extend from the bracket 114 to gusset plates 117 located near the lower end of the intermediate section of the guide posts 76. As shown in FIGS. 8 and 10, a pair of diagonal struts I18 extend from a plate I119 at the center and front of the bracket M4 to pins 120 on the top of the beam and section 90 to insure lateral rigidity in the connection of the guide posts 76 and 78 to the crane cab 24.

Although the function of the upper and lower extensions 8t) and 82 of the guides posts 76 and 78 is obviously to extend the range of vertical distance through which the guide posts are operative, it is important to the overall efficiency of the system of this invention that these extensions be easily retractable to an out-ofthe-way position. For example, the upper guide post extenions 80 would, if not retractable in this manner, inhibit translating movement of the crane 10 from lot to lot in the project being developed particularly where overhead obstructions such as trees, utility wires and the like are present. Thus, as shown in FIG. 9, each of the upper extensions 80 has secured to its lower end a pair of plates 12] pivotally connected by pin 122 to a rearwardly projecting lug 124 secured at the upper end of the main section 79 of each of the guide posts 76 and 78. The plates 120 are provided with an additional hole 126 such that when the extension 80 and plate 120 are pivoted through 90 to an upright position illustrated in phantom lines in FIG. 9, the hole 126 registers with a hole I28 in the guide post to facilitate the insertion of a pin to secure the connection. Inasmuch as the extensions 80 represent a substantial weight to be moved in this fashion, mechanical means are provided for erecting them. As shown in FIG. 9, a light cable winch I30

Claims

1. A system for placing interiorly finished, factory prefabricated housing units on lot site foundations, said system comprising: a crane having a rotary structure including boom and hoist line swingable about a vertical axis; a load spreader suspendable from said hoist line and including means to establish retractable, rigidly linear foundation-like supports under opposite sides of the housing unit along the full length thereof; a snubbing frame mountable on said crane to move with said boom in its swinging movement about said vertical axis; and means to connect said load spreader adjustably to said snubbing frame to insure movement of said load spreader directly with movement of said snubbing frame about said vertical axis irrespective of vertical movement of said load spreader by said lifting cable.

2. The apparatus recited in claim 1 wherein said snubbing frame includes a pair of upright guide posts and means to support said guide posts from said rotary crane structure in horizontal spaced relation on opposite sides of said boom.

3. The apparatus recited in claim 2 wherein said crane includes a chassis supporting said rotary structure, said chassis having outrigger beams extending radially beyond the radial distance between said guide posts and said vertical swing axis, said guide posts having retractable lower extensions to extend the vertical range thereof while enabling swinging movement of said guide posts over said outrigger beams.

4. Apparatus for use with a rotary crane having a boom and hoist line swingable about a vertical axis for the handling of large, delicate loads such as interiorly finished, factory prefabricated housing units, said apparatus comprising: a snubbing fame adapted to be mounted on the crane to move with the boom thereof in its swinging movement about the vertical axis of the crane; a load spreader suspendable from the crane hoist line and including means to establish a retractable, rigidly linear, foundation-like support under opposite sides of the load along the full length thereof; and means to connect said load spreader adjustably to said snubbing frame to insure movement of said load spreader directly with movement of said snubbing frame about the vertical crane axis irrespective of vertical movement of said spreader by the hoist line.

5. The apparatus recited in claim 4 wherein said last mentioned means comprises a horizontal header connected to said snubbing frame for vertical movement only and two sets of triaxially oriented, extensible links connected between said header and said foundation-like support establishing means on one side of said spreader.

6. The apparatus recited in claim 5 wherein the axes of said links intersect the longitudinal axis of said header, thereby to permit pivotal movement of said spreader about said longitudinal header axis.

7. The apparatus recited in claim 6 including means to adjust the longitudinal position of said header on said frame.

8. The apparatus recited in claim 4 wherein said snubbing frame includes a pair of vertical guide posts and a slide member movable freely on said guide posts solely in a vertical direction, said last mentioned means comprising a horizontal header detachably mountable on said slide member and a pair of triaxial sets of extensible links connecting said support establishing means on one side of said spreader to said header.

9. The apparatus recited in claim 8 wherein one of said sets of links is operable at each end of said header.

10. The apparatus recited in claim 8 including mounting plate means to mount said header on said slide member in a plurality of different selected longitudinal positions on said slide member.

11. The apparatus recited in claim 8 wherein said links are adjustable screw jacks having actuating handle means, the handle means for each set being in proximity to each other to enable concurrent operatiOn of all jacks in one set by one person.

12. A snubbing frame for a rotary crane having a boom and hoist line supported on a cab structure swingable about a vertical axis, said snubbing frame comprising: a pair of vertical guide posts; means to support said guide posts rigidly from the cab structure in an upright parallel relation, one on each side of the boom; slide means movable vertically on said guide posts but constrained against lateral movement with respect to said guide posts; and linkage means to connect said slide means positively with a load suspended by the hoist line of the crane.

13. The apparatus recited in claim 12 including a horizontal beam rigidly interconnecting said guide posts near the lower end thereof to establish with said posts a generally U-shaped subassembly and wherein said guide posts supporting means comprises an assembly of compression-tension struts connected to said subassembly and adapted to be connected to the cab structure.

14. The apparatus recited in claim 13 wherein said guide posts each include a laterally projecting continuous guide flange extending the full length thereof and wherein said slide means comprises a pair of guide shoes each having mutually facing pairs of bearing pads to engage said guide flanges on said guide posts respectively.

15. The apparatus recited in claim 12 including upper and lower guide post extensions and means connecting said extensions to said guide posts for movement between a retracted position and an operative position in which the extensions are aligned with said guide posts.