|I still want to add another detail – a davit of sorts hanging off of the post on the end of the platform. The following is from “The construction of cranes and other lifting machinery” by Edward Charles Robert Marks pub. 1904|
Chapter VI – Pillar Cranes – In factories, stores, or other buildings where central iron columns or pillars are employed for assisting in the support of the floors and roof of the structure, and where loads of from quarter to half a ton have to be dealt with, a convenient and useful crane can be formed by utilising one of the columns as a crane post and building the machine about it. Such a crane can be slewed or swung completely round the column, thus commanding a complete circle in which loads may be dealt with.|
It should here be explained that in cranes where the diagonal stay is distinct from the tie rod, and not rigidly connected to it, it is usual to speak of the stay itself as the “jib.”
The connecting clips are forged in two pieces and securely bolted together around the necks of the column. But when thus bolted together the clips must not bind or fit tight, the bore being of such diameter that they make an easy fit around their bearings, so that the crane may be freely turned or slewed. The jib consists of a wrought-iron tube, at the upper end of which a cast-iron head or cap is secured. The lower end of this cap enters the tube to the distance of about 6 in., and a hole is then drilled through both tube and cap to admit of a stud or rivet for rigidly connecting them together. The jib-head guide pulley is carried in the upper portion of the cap. A cast-iron foot, secured in the same manner to the lower end of the tube, enables a pin connection to be made between the jib and the bottom clip of the column.
The lifting mechanism itself, or the crab, is made up of single-purchase gearing, with barrel and ratchet, brake wheel,
Chapter VII – Whip Cranes – The whip crane is another form of central pillar crane. The term “whipping ” a load appears to have had its origin with the pulling or whipping up of coals or other cargo from the holds of sailing vessels, where no steam winches are available, a method that may still be daily seen in operation at all seaports. The coals are shovelled into baskets, which are drawn up by means of a rope passing over a single sheave pulley or gin block, attached to the end of a jib run out from the mast and rigging of the vessel. No purchase is, [of course, obtained by this arrangement, so that no greater load can be drawn up at a time than the men are able to raise by their own exertions, unaided by any mechanical power; but by long practice the men acquire a great degree of dexterity in suddenly pulling or snatching at the hauling rope, and thus throwing all their energy into one pull that shall be sufficient to bring up the coal-laden basket at a brisk speed. This suddenly applied force constitutes the “whipping.”
Each crane has two barrels, one at the top and the other at the lower portion of the crane post. The upper barrel is employed for winding the lifting chain, whilst the lower one winds the hand or hauling rope. The hauling rope is secured to the lower barrel, and passes up to and around the large rope wheel on the upper or chain barrel shaft. Sufficient rope is wound round this wheel to allow of the load being lifted to the required height before all the rope passes to the lower barrel. The length of rope required on the top wheel is therefore not less than the height of lift multiplied by the ratio between the diameter of the wheel and the diameter of the chain barrel.
In the one-ton crane illustrated, where the rope wheel is 3ft. diameter and the chain barrel 8in., if the load had to be lifted through a height of 5ft., the amount of rope required on the top wheel would be
It is always well to have half a lap of rope, at the least, beyond_ what is actually required, as this will relieve the strain in the attachment of the rope to the wheel. Such attachment is usually made by passing the rope through a hole formed in the rim of the wheel, and tying a secure knot at its end.
Light loads, up to about 3 or 4 cwt. (300-400 lbs), are lifted by simply pulling at the hauling rope, the mechanical advantage being represented by the ratio between the rope wheel and the chain pulley. This, as we have already seen in the case of the crane before us, is 4½ : 1. The heavier loads are lifted by turning the rope barrel shaft with the crab handles, thus giving the advantage of a compound system of leverage. Our one-ton crane will have a barrel of 12in. diameter, and crab handles of 15in. radius; the purchase will therefore be , 30 The diameter of the rope must be added to the diameter of the barrel.) For dealing with the maximum loads the crane is constructed to carry, the crab handles are fixed on the first motion shaft, on which is keyed a pinion gearing with a spur wheel on the barrel shaft. With a spur wheel 25 in. and a pinion 5 in. diameter, the total purchase of the crane will be
The crane, as illustrated, is constructed with a timber crane post and jib, and two wrought-iron tie rods.
|.. thoughts ..|
|I will be going with the Pillar Crane using styrene and brass as it is pretty simple. I had thought about possibly going with the Whip Crane. In any case I thought the information worth sharing … so .. there you go.|