Built-Up Hoists

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Weight Handling Equipment

Commercial Base/Deck Mounted Electric Hoists

MIL-HDBK-1038

Rotate bearing bolts, studs, and nuts must be left unpainted.

(These items require periodic inspections and checks of their tension.)

Non-structural fasteners, such as those retaining keeper bars, etc.,

should be painted without blast cleaning.

4.3

Mechanical. The vast majority of mechanical components are standard

commercial items, usually designed and built to existing industry standards. They

range from the complete hoist assemblies to load hooks. The standard commercial

items are described in catalogs and advertising literature; however, such

descriptions must be reviewed and understood to ensure that the desired ratings

and design factors are being provided.

4.3.1

Hoists. The hoists are the most critical assemblies of any

crane - they raise, lower, hold, and stop moving loads and warrant the most

attention to their design and quality of workmanship. Depending on the

application, the hoists may be built-up to the precise specification requirements

or they may be standard commercial units designed to a particular service or duty

class. The built-up hoists are always electric motor driven and with wire rope

reeving. The standard commercial hoists may be electrically, hydraulically, or

manually driven and may use either wire rope or chain reeving.

4.3.1.1

Built-Up Hoists. In the typical arrangement, the electric motor is

connected to the gear reducer input (high speed) shaft by a full-flexible coupling

with one shoe brake installed on the opposite end of the input shaft and another

brake installed either on the outboard (tail) end of the motor or on the coupling

hub on the gear reducer input shaft. There are several options for connecting the

gear reducer output shaft to the wire rope drum:

The output shaft may be connected directly to one stub shaft of the

wire rope drum by a full-flexible coupling, in which case the drum must be

supported independently on two stub shafts, each mounted in a bearing.

The output shaft may be pressed directly into the drum hub, in which

case the inboard drum stub shaft and support bearing may be omitted if the

adjacent gear reducer bearing has adequate capacity. Alternatively, a bearing of

adequate capacity may be installed to support the inboard drum stub shaft and the

adjacent gear reducer bearing removed. In both of these arrangements, the three

bearings must be mounted on solid foundations, aligned/shimmed very accurately to

preclude built-in stresses. It should be noted that although self-aligning

bearings are commonly used in these applications, they take up the angular, but

not the parallel, misalignments.

To avoid the stringent alignment requirements of (b) above, the

inboard stub shaft may be replaced by a barrel type coupling to provide the radial

support and to transmit the drive torque. Barrel couplings are designed for

angular misalignments of up to 2.0 degrees (similar to semi-flexible couplings)

and have much greater radial load capacity than the shaft-to-shaft couplings. The

barrel couplings are flange mounted by a ring of bolts to the drum end plate. The

adjacent gear reducer bearing must have adequate capacity for the imposed radial

loads.

The output shaft may terminate with a gear pinion, which engages a

ring gear on the drum. In this arrangement the drum is supported independently by