Design of wheel hub assembly of a single wheel application for a light commercial vehicle

Madhusudhan Reddy V J 1RV08ME046Manjunath M M 1RV08ME050Shridhar Patil 1RV08ME099

Internal Guide Associate Professor P R Venkatesh

External GuideDeepak Sheelvanth

Project manager, Meritor Commercial Vehicle Systems Pvt. Ltd.

Classification

• Based on GVWR commercial vehicles are classified as follows

1. Light commercial vehicles (0-6.5 tonnes)2. Medium commercial vehicle (6.5-11.8

tonnes)3. Heavy commercial vehicle (11.8 tonnes

onwards)

Light commercial vehicle• Light commercial vehicles (LCVs) are usually

referred to goods and carriage vehicles with a light capacity that varies from one region to another. Ex: - Tata 407, Tata 709

Wheel Hub

• Wheel hub is a rotary component which provides support to the wheel and assists in easy movement.

• It is the component upon which the wheel and brake mounts, it is fitted over the wheel bearings.

• A hub assembly contains the wheel bearing, fasteners, seal and the hub to mount the wheel.

• It may also contain the anti lock brake system, wheel speed sensor which makes them very expensive in some cases.

• The bearings over which the wheel hub is mounted is again over the axle.

• Single wheel application means the rear axle contains only a single wheel on its either side.

Problem definition

• The GAWR for our application is 3.5 tonnes, with the GVWR being 5.7 tonnes.

• So, the load that single wheel on the rear side should bear is 1.75 tonnes.

• And the mass of the hub being 10.25 kg (cast hub)

Hubs can be classified into two types1. Outboard mounted hub2. Inboard mounted hub

• Hub for a single wheel application

• Hub for dual wheel application

• The loads acting on a vehicle are1. Torsion stress due to driving and braking

torque.2. Shear stress due to the weight of the vehicle3. Bending stress due to the weight of the

vehicle4. Tensile and compressive stress due to

cornering forces.These above forces can be divided into vertical

and horizontal forces.

Test fixtures

1. With the axle fixed

2. Fixture with wheel fixed

Bearings

• As the hub is a rotatory component, we use rolling contact bearings.

• In rolling contact bearings, the contact between bearing surfaces is rolling instead of sliding as in case sliding contact bearings.

• Te advantage of a rolling contact bearings over a sliding contact bearing is that of a low starting friction.

• Due to this low friction offered by rolling contact bearings, these are also known as the anti-friction bearings.

• Friction in bearings leads to heat, higher torque needed to overcome the friction, wear all of which ultimately leads to the deterioration in performance of the bearings.

• Anti-friction bearings overcome these effects.• Nomenclature

• Anti-friction bearing types

Tapered roller bearings• Tapered roller bearings are uniquely designed to

manage both thrust and radial loads on rotating shafts and in housings.

• The taper angles allow the bearing to handle a combination of radial and thrust loads.

• The steeper the cup angle, the greater the ability of the tapered roller bearing to handle thrust loads.

• These are extensively used in automobiles (to support the wheels); here they are used in pairs to accommodate the axial thrust from both directions, as well as radial loads.

Tapered roller bearings nomenclature

• Tapered roller bearings are further classfied into

1. Single row tapered bearings.2. Dual row tapered bearings.3. Multi row tapered bearings• For our design we are considering single row

tapered bearings, as they are enough to bear the load in our application.

• The point where the force line meets the axis is known as the bearing effective centre.

Free body diagram, shear force diagrams and bending moment diagrams.

Calculations

• Reaction forces acting on the bearings RA = F (z/y -1)RB = F (z/y)• Pressure acting on the bearingsPA = RA / APB = RB / A• Moment arm = [ 0.7 (slr) + d ]• Test load = moment/moment arm• Moment = [ 0.7 (slr) + d ](S)(L)

• Slr = static loaded radius• S = load acceleration factor• L = load rating of the hub ( In this application the load rating being

1.75 tonnes ).• d = load offset value.

DESIGN OF HUB

• We already know how important the bearings are, so the bearings have to carefully selected.

• The outboard bearing is X32211-Y32211• The inboard bearing is X3982-Y3920 ( bearing info from Timken)

Outboard and inboard bearing infoDimensions Outboard Inboard

D - Cup Outer Diameter 100.000 mm 112.713 mm

d - Cone Bore 55.000 mm 63.500 mm

B - Cone Width 25.000 mm 30.048 mm

C - Cup Width 21.000 mm 23.813 mm

T - Bearing Width 26.750 mm 30.163 mm

a - Effective Center Location

4.10 mm 4.60 mm

Hub specifications

• Hub with a inboard mounted drum.• Mounting bolt circle dia = 203.2 mm• Hole size = 18.9 mm• Drum pilot dia = 162.85 mm• Wheel pilot dia = 160.7 mm• Oil seal dia = 114.3 mm• Flange thickness = 16 mm• Load line to inboard bearings effective centre

= 30 mm

• Outboard bearing shoulder to drive shaft flange = 60.73 mm

• Density of the material= 7.1 E -6 kg/mm³• Poisson’s ratio = 0.25 • Oil seal width = 24 mm• Wheel offset = 107.5 mm• Machining stock = 3.5 mm• Bearing span = 92 mm

• Designed hub within the set weight limit1. The basic cross section

2. The model cut section

• The volume of the designed model is 1388886.0830 mm³

• The mass of the model is given by, Mass = Density * volume = ( 7.1 E-6 ) * (1388886.0830) = 10.13 Kg.

Further work

• Analysis using PRO/ENGINEER MECHANICA