Off-the-Shelf Components

Along with the bespoke components the rig has a number of outsourced parts, such as the motor, dynamometer, couplings, bearings and the gears, where the motor is an 11 kW, 4 pole high efficiency unit sourced from Brook CromptonR (Frame reference: W-DA160MJ), which at full load runs at a speed of 1470 rpm and a load of 71.5 Nm. The most important parameter of the motor, with respect

Figure 5.4: Lubrication Box

to the dynamic model is its rotor inertia, which is 0.068 kgm2 as this contributes to the mass of the system.

The dynamometer is a Borghi & SaveriR _{FA-50/30 SLV water cooled eddy} current unit with maximum power, speed and torque of 44 kW, 12,000 rpm and 102.5 Nm respectively, which is sufficient to match the output of the motor. As with the motor the dynamometer is considered to be fixed to the ground, such that its only mass of interest is its rotary inertia, which is found to be 0.0035 kgm2. The dynamometer is controlled by a Schenck Test Automation Series 3000 controller, which is able to set the required loading of the gears to an accuracy of 0.05% of the full scale deflection, giving accurate control over the test load.

The motor is connected to the shaft via a Type GR curved jaw coupling sourced from LenzeTM(model 38/45), as shown in Figure 5.5, with dimensions given in Table 5.2. In this coupling Hub A, with bore hole size of 25 mm, is connected to the shaft, while Hub B is connected to the motor output shaft.

Type Fa Fb Fg E A B H L I M S N G

A B

38/45 25 42 10 12 80 66 80 45 114 37 24 3 18 38

Table 5.2: Coupling dimensions with reference to Figure 5.5 (All dimensions in mm)

Figure 5.5: Curved jaw coupling

This consists of two cast iron hubs connected through a polyurethane resin spider with a dynamic torsional rigidity of around 23.63 kNm/rad about the shaft rotational axis. The coupling allows free rotation about the other axes up to an angle of 0.9◦, which means that its rotational stiffness about these axes can be ignored; this assumption is also made for the axial stiffness, where the coupling allows axial misalignment of 1.8 mm. Vertical and horizontal stiffness are not documented and therefore suitable values must be determined. Mass values have been calculated through CAD drawings of the two hubs, where it is assumed that both are made from cast iron with a density of 7000 kg/m3_{, which results in the mass properties}

given in Table 5.3 with moments of inertia taken about the hubs centre of mass. Mass (kg) Moments of Inertia (kgm

2₎

Ixx Iyy Izz

Hub A 1.13 0.000844 0.000716 0.000716

Hub B 1.25 0.0013 0.000965 0.000965

Table 5.3: Coupling mass properties

The bearings have been sourced from SKFR _{and specified to avoid failure} of the bearings under the subjected loading conditions; the resultant bearings are cast plummer block units (Housing: SYJ 507) with Y-bearingsR _{(YSA 207-2FK) on} an adapter sleeve (H 2307), as shown in Figure 5.6. These are 03 dimension series sealed single row deep groove ball bearings with a bore diameter of 30 mm, outside diameter of 72 mm and a width of 19 mm, where Table 5.4 shows the important bearing data required for modelling.

Figure 5.6: Plummer block bearing schematic taken from www.skf.com

Ne α0 de PCDb rρ,i rρ,o rL Eb νb

9 0 11.112 53.5 27.41672 26.08328 0.05 208 0.3

Table 5.4: Bearing data table: Ne = number of bearing elements, α0 = unloaded

contact angle (◦), de = bearing element diameter (mm), PCDb = bearing pitch

circle diameter (mm), rρ,i and rρ,o = radii of inner and outer raceway centres of curvature (mm), rL = radial clearance (µm) and Eb andνb = bearing material

Young’s modulus (GPa) and Poisson’s ratio

This information will be shown to be useful in determining the stiffness char- acteristic of the bearings in the next chapter, while the mass can be obtained from finite element analysis of the bearing CAD drawing. The bearing mass is split into two sections, the first includes all the internal components, as shown in Figure 5.7(a), while the second includes only the bearing block casing and the outer raceway, as shown in Figure 5.7(b).

(a) Internal components (b) External components

Figure 5.7: Bearing CAD models for mass calculation

In Figure 5.7(a) the majority of the components are assumed to be con- structed from bearing steel with a density of 7850 kg/m3_{, while the seals either side}

of the ball bearings are assumed to be constructed from rubber with a density of 500 kg/m3. In Figure 5.7(b) the casing is modelled as cast iron with a density of 7000 kg/m3 and the outer raceway is modelled as bearing steel, which result in the

mass properties given in Table 5.5 where the moments of inertia are taken about the components centre of mass.

Mass (kg) Moments of Inertia (kgm

2₎

Ixx Iyy Izz

Bearing Internals 0.373 0.000163 0.000133 0.000133 Bearing Externals 1.33 0.00328 0.00251 0.00116

Table 5.5: Bearing mass properties

The final outsourced components are the gears; however their physical di- mensions have been discussed at length in Chapter 4 and will not be reiterated here. The only physical quantity required for the gears, which has not been discussed is their weight; this has been determined through the finite element model of the gears assuming that they are constructed from steel with a density of 7850 kg/m3, where the resultant mass properties of the two gears are given in Table 5.6

Mass (kg) Moments of Inertia (kgm

2₎

Ixx Iyy Izz

Gear 1.09 0.00244 0.00124 0.00124 Pinion 0.975 0.00202 0.00102 0.00102

Table 5.6: Gear mass properties