New Rotating FS-Tower with thoughts...
Thoughts...
After removing all the debris from the collapsed 150ft rotating tower, it's time to rebuild and renew the design. NCRT means No Compromize Rotating Tower. The idea is to rotate the new FS (Free Standing) at the base and add some new features:
-Slewing gear at base
-Tower lift for antenna's
Using a tower crane slewing ring as rotor
A bearing serves as a connection between two adjacent structures, allowing rotation and transmission of load between them. In addition to satisfying my requirement, a turntable bearing typically includes features for simple and quick attachment to those adjacent structures, and commonly a feature to facilitate the mechanical rotation of one ring and its adjoining structure relative to the other.
Axial Load:
Load parallel to the axis of slewing ring.
Radial Load:
Load vertical to the axis of slewing ring.
SLEWING TORQUE Calcultation of the necessary torque to enable a rotation of the whole assembly takes into account :
• loads on the tower,
• rotating masses,
• distance to the rotation axis,
• speeds and accelerations,
• resisting torques.
The friction torque for a turntable bearing due to external loads can be estimated using the following equation.
Mw = bearing torque under load, (ft-lbs)
µ = friction coefficient
Mk = moment load, (ft-lbs)
Fa = axial load, (lbs)
Fr = radial load, (lbs)
Dp = bearing pitch diameter, (ft)
Tilting Moment Torque: Torque is the load multiplied by the distance between the position of load and the center of sleewing ring. If the torque generated by load and distance is greater than the rated Tilting Moment Torque, slewing drive will be overturned
Bearings
The bearing consists of an inner and outer ring made of medium carbon steel. Each includes at least one precision raceway arranged to transfer loads and relative motion from one structure of the equipment to the other.
The majority of turntable bearing applications require the bearing to transmit static load or high loads at slow rotation with operation being intermittent.
Turntable bearings can be supplied with gear teeth as an integral part of either the inner or outer ring. They are typically a standard full depth or stub involute spur gear having a 20° pressure angle
Pinion teeth
The backlash should be measured just inside each end of the pinion and gear mesh to verify that proper alignment is obtained. Poor alignment can result in premature tooth wear and breakage. Consider any crowning of the pinion teeth when evaluating the alignment.
Backlash is required for most geared turntable bearing applications. This is to accommodate manufacturing tolerances of the gears, mounting structures, lubrication, thermal expansion, and deflection of the components under dynamic loading.
If a bearing with an integral gear has been selected, the machine designer should work with a pinion manufacturer to select the appropriate mating pinion. It is important to be aware and consider all potential operating circumstances which could be detrimental to pinion and gear life.
Planetary gear
A planetary gear set is gear assembly that consists of 3 primary components. A Ring Gear (the outer most gear), 3 planetary gears that are housed by a Planetary Carrier assembly (the middle gears), and a Sun Gear (the gear in the center of the gear set. All three gear sets are splined in order to connect or mate to a band, clutch, and/or splined to the main shaft. Through an intricate collage of these various types of connections and brakes, various components of the planetary gear set can be allowed to spin free, be held, or transmit applied power or torque to an output member – commonly referred to as the transmission assembly or power plant. The bands or brakes can be applied in several ways such as Hydraulics, centrifugal clutches, electronics, servos, etc., and can be done automatically or manually.
Slewing mechanism for tower crane
Considering hydraulic or electrical drive (Planetary Drive) Gearboxes for slew drive of excavators, all kinds of mobile cranes, tower cranes of construction sites, harbour and deck cranes. A large selection of reduction ratios are available for all sizes, along with built-in negative brakes and adaptors for all the most common hydraulic and electric motors.
Tower crane slewing unit
The past months I have been looking for the right gear, below some pictures of potential gear...
All tower cranes consist of the same basic parts:
•The base is bolted to a large concrete pad that supports the crane.
•The base connects to the mast (or tower), which gives the tower crane its height. •Attached to the top of the mast is the slewing unit -- the gear and motor -- that allows the crane to rotate:
Tower crane slewing unit
All tower cranes consist of the same basic parts:
•The base is bolted to a large concrete pad that supports the crane.
•The base connects to the mast (or tower), which gives the tower crane its height. •Attached to the top of the mast is the slewing unit -- the gear and motor -- that allows the crane to rotate:
Tower crane slewing unit
The past months I have been looking for the right gear, below some pictures of potential gear...
Finally
The shorter horizontal machinery arm, which contains the crane's motors and electronics as well as the large concrete counter weights:
...Bought a Tower crane slewing unit.
More to come within a few weeks (transport)
