Giant Gantry Crane

There have now been three incarnations of this, based on the Chinese-manufactured original. The latest version was rebuilt for the event at Norwich Library, which was subsequently called off. Rather than dismantle the thing as soon as it was finished, I thought it might be a neat idea to provide instructions, which you are free to adapt or ignore as you see fit. Although this is a large structure, there is a lot of symmetry in it and so the instructions for building it are quite short.

The Bogies
Each of the bogies are exactly the same in construction. The sides of the bogies are formed by two 5½" x 1½" flexible plates (1) overlapped 5 holes to form a 8½" long plate which is situated centrally, and a 2½" x 1½" triangular plate is fixed to either end of this. On their bottom edges the 5½" plates are strengthened by two 5½" strips overlapped 5 holes. The bolts (2) that attach each 5½" plate to the triangular plates also secure 1½" double angle strips (3) that join the sides together, and a third one of these is bolted centrally.
The top of each bogie is a 12½" strip plate which carries a 2½" x ½" double angle strip (4) at either end, flanges upturned, and to the undersides are attached 12½" girders that form the upper edges of the sides of the bogies.
The running wheels are carried on 2" rods which are located 4 holes in from each end.

The Legs
Again, these are alike in construction. The outer side of each leg is an 18½" girder (5) while the inner side is a 12½" girder (6). These are joined by a 12½" strip plate (7) which is strengthened at the bottom by a 2½" strip. The girders are attached to the double angle strips (3) of the bogies. To the top of strip plate 7 are bolted a 2½" x 2½" flexible plate, a 2" x 2½" triangular plate and a 5½" strip. Above these plates are bolted a 3½" x 2½" flexible plate and another 2" x 2½" triangular plate, which are butted together. The tops of these plates are fixed to a 5½" flat girder (11).
The tops of the 18½" angle girders are attached to a 7½" flat girder (12), the central lower hole of which carries two 7½" strips which are used to brace the sides of the legs.

The Running Track
Each rail is two 24½" girders (13) with a 12½" girder (14) in between them. Note that these girders are all butted together so that their slotted holes, which point inward and form the actual track, are continuous and completely free from fixings. The central 12½" girder carries a 4½" flat girder (15) at either end which is used to connect the 24½" girders to it on each side. The sides of the track are formed by a double depth of 12½" strip plates which are butted together in the same way where they meet the centre. The bottom edge of the strip plates are also edged on the inside by a similar length of 24½" and 12½" girders. These are butted together additionally by 2" girders (16) at either end of the lower 12½" angle girders.
Note also that the bolts along the rail edge that secure the top layer of strip plates to the girders should be ideally of the dome-headed type and face outwards. This is to make sure the carriage does not snag when it encouters them.
At the far ends the rails (both top and bottom) are connected together by two 7½" girders. The far end girders are braced to the sides by 5½" girders, each of which is located in the seventh hole in from the side. A further 7½" girder is bolted across the top rail in the 13th hole from the end. This heavy bracing is necessarybecause there is of necessity none between the rails at any other point. Feel free to add more bracing if necessary!
Each side is now strengthened at their ends by a 5½" or 4½" girder (18) and a 4½" strip edges each side. The feet of these girders are attached to the 7½" flat girder 12 of the leg and are braced to it by 5½" strips directly above the 7½" strips which brace the legs apart. The sides are extended downward at each end by a 5½" x 2½" flexible plate and a 2" x 2½" triangular plate which are attached to 5½" flat girder 11. All the 2" x 2½" flexible plates are then strengthened by 3" strips (19), the top one of which is of course secured to the lower rail girders.

Other Structural Components
The inspection cabin's floor is a 5½" x 2½" flanged plate (flanges upwards) with an obtuse angle bracket and a vertical 4½" strip (20) attached to the front. Halfway up each strip on each side is attached a horizontal 5½" strip, with a similar part secured in the top holes. At the rear of the cabin is a 4½" angle girder, with a 4½" x 2½" flexible plate attached. Each pair of obtuse angle brackets is joined at the front by a pair of 4½" strips, the securing bolts also carrying a formed slotted strip which serves as the front. A similar part is bolted halfway up and another at the top, and the three are connected by a 4½" narrow strip (21). On each side a centrally-positioned 4½" x 2½" flexible plate fills in the sides. The cabin is attached to the main frame on the outside edge by angle brackets bolted to the bottom 24½" girder, and on the inside by a similar part attached to one of the transverse 7½" girders. A corner gusset braces the cabin. A 1½" x 3½" flat plate (22), with a 1½" girder (flange up) bolted to its outer end is secured to the underside of the floor such that it extends 2" outwards from the cabin. This forms the entrance to the cabin and is also the link between the two ladders.
The bottom ladder is a pair of 12½" strips joined at either end by a double bracket. The inside lug of the bottom double bracket is attached to the outside of a supporting leg at a point 8 holes up, and the topmost double bracket is attached to the underside of the flat plate. The ladder leading to the trolley track is a pair of 19½" strips. The outer strip is attached to the 1½" angle girder and the inner one to an angle bracket. At the top the two are joined (suitably spaced apart) by a long bolt (23) which is then attached to one of the 24½" rail girders.
The alighting platform is formed from a 1½" x 1½" flat plate and a 1½" x 3" flat plate, separated by a 3" strip (24) on the outside. Each far end of the flat plates carries a threaded coupling, and a 6½" rod links them together to form the outer safety rail. A further threaded coupling (25) is secured to the inside of the smaller flat plate at such a height that a 1" rod in its centre tapped bore aligns with the top hole in the other coupling. The platform is attached to the top rail by angle brackets.
The main safety rail is formed from three 11½" rods and an 8" rod, all suitably connected with rod connectors or couplings. At suitable points along the top rail are located rod and strip connectors carrying 1" rods which enter the central tapped bores of couplings. Thr rail rods are then inserted into the longitudinal bores of these couplings, with the cabin-end rod being secured in the top tapped bore of threaded coupling 25.

The Trolley
The base of the trolley is made up of two 5½" x 2½" flanged plates joined at each side by a 7½" girder such that there is a 2" gap between the plates. The front plate is extended forward 2" by a 4½" strip (26). These strips are joined together by a 5½" double angle strip, at the same time attaching a 1" angle bracket to the lugs. A 1" angle bracket is also fixed, lugs outwards, to the rear of each angle girder. These four 1" angle brackets form attachment points for the body casing.
An E15R Motor is attached to the rear flanged plate, and a 7/16" pinion on the armature meshes with a 60-tooth gear on a 2½" rod journalled in the motor side plates, whose rear holes are strengthened by a 2½" strip on either side. The other end of this rod carries a worm (27). The inner sideplate is extended by a 2½" flat girder, to which a 3½" x 2½" flanged plate is fixed. A 3" girder spans the flanged plates, and it carries a 2½" x 2½" flat plate (28), which is further attached to the motor sideplate by a ½" x 1" angle bracket. Additional bracing is supplied by a 3½" double angle strip that joins flanged plate to flat plate 28. 1½" from each side is fixed, mirror-fashion, a corner angle bracket (29), both with their slotted holes pointing downward.

Drive System
Worm 27 meshes with a 19-tooth pinion on a 4" rod which carries a 25-tooth pinion (30) at the other end. Power to the driving wheels is taken from pinion 30 by a 50-tooth gear (31), boss outward, on a 4½" rod which bears, inside the drive sideplates, a ½" diameter, ¾" face pinion (32) and a collar. The space between pinion and collar should be just greater than a bolt-head. Another 50-tooth gear is fixed on a 6½" rod, and is in permanent mesh with pinion 32. It carries at either end a ¾" sprocket. Each sprocket is connected to a 1" sprocket on 8" axles. One 1" sprocket is on the front axle and the other on the rear axle. The running wheels are 1" pulleys with tyres, but only one pulley is fixed on each axle. The other driving wheels are free to turn and given a small amount of lateral travel, being restrained by collars. This is to allow for inequalities in track level and lateral motion. The non-driven wheels are made to align with the driven wheels by being spaced with collars and/or washers. Drive to the wheels is engaged by a lever formed by a bell crank, boss upwards, held in a crank beneath the base bolted to the 3" angle girder that bridges the two flanged plates of the base. The rear arm of the bell crank carries a ½" bolt, whose head engages between the collar and pinion 32 on the 4½" rod. The other arm carries a ¾" bolt in an end bearing on a 3" rod, the other end of which is held in a swivel bearing in whose spider is fixed a rod forming the actual lever. It is held in a rod and strip connector bolted to one of the corner angle brackets. Gear 31 is normally held out of mesh with pinion 30 by a tension spring attached to the middle hole of the bell crank and whose other end is held by a long bolt fixed to the central hole of the forward flanged plate of the base.
Drive to the hoisting cords is via a 50-tooth gear (33) also mounted on a 4½" rod. This gear's boss also faces outward so that it is normally out of mesh with the pinion 30. Inside the sideplates, the rod carries a loose collar, a compression spring, fixed collar and another ½" diameter, ¾" face pinion (34). The fixed collar should compress the spring very slightly, and the gap between this collar and the boss of pinion 34 should be just greater than the head of a pivot bolt. Movement of this rod is controlled by a bell crank on a 1½" rod which is secured in the boss of a crank beneath the flanged plate. The long bolt that formed the fixed end of the tension spring also attaches the crank to the flanged plate. Above the flanged plate the rod passes through a reversed angle bracket and the bell crank is spaced from it by 4 washers. The rear arm of the bell crank carries a pivot bolt which engages between the fixed collar and pinion 34 on the 4½" rod. The other arm is pivotally attached to a strip coupling which carries a 1½" rod whose other end is fixed to a swivel bearing as previously. A 50-tooth gear (35), 1" bush wheel and a 1" pulley are fixed on a 4" rod such that the gear is in permanent mesh with pinion 34. A length of cord attached to an elastic band provides a brake by being located in the groove of the 1" pulley.
The third lever controls the motor. The vertical arm of the motor switch carries a threaded pin with a loose collar attached, held in place by another collar. A 4½" threaded rod is screwed into the collar (making sure that the collar is still free on the threaded pin) and its other end located in a threaded coupling. The other end of this coupling carries a 1½" rod fixed in a swivel bearing as with the previous levers.
A double bracket (lugs to the rear) carrying a 1½" rod is fixed to the rear of the forward flanged plate, and to the front of the rear flanged plate is attached a flat trunnion and a channel bearing (lugs forward), which forms the block for a single 1" pulley and also a securing point for the end of the hoisting cord. This runs from the 1" bush wheel-winding drum, over the 1½" rod, over one 1" pulley in the pulley block, back to the pulley in the channel bearing, round a second 1" pulley in the block and then to the flat trunnion. The trunnion is optional but it serves to align the channel bearing as well as provide a final anchoring point for the hoisting cord.

Trolley body casing
This is left to the builder, but I like to provide a door at the rear for motor lubrication and gear adjustments using a hinged flat plate. The 1" angle brackets of the base provide attachment points for the casing.