Portale di Ateneo - En.Unibs.it

The course is divided into two main blocks:
1) Theory of special vehicles (theoretical basis for vehicle layout).
2) Characteristics of the driveline of special vehicles and their design (Layout).

Which are detailed below

1) Theory of special vehicles (theoretical basis for vehicle layout).

1.1) Land-vehicle interaction
• First approach: Bussinesq
• Pressure bulbs, correction factor

1.2) Maximum load supported by the ground
• Criterion of Mohr Coulomb, land subsidence modality.
• Bulldozing, vertical load

1.3) Terrain characterization
• Method of determining characteristics and testing machines.
• Bekker, Reece and repetitive load approach.
• Shear stress / shear displacement.
• Tracked vehicle, estimated traction performance, constant and non constant ground pressure model.
• Vehicle on wheels, stiff and non stiff wheel performance estimation model.

1.4) off-road vehicles performances
• Forces
• Drawbar power, related charts.
• Efficiencies, slip efficiency 2 and 4WD, related charts.
• Power to weight ratio
• Schematization of the design process for defining the layout of off-road vehicles as a function of the mission

1.5) Skid steer and articulated vehicle steering
• Forces, observations
• Steerability, the vehicle steers?
• Kinematic approach.
• Combination of the two approaches.
• Centrifugal force insertion and results, with and without load transfer.
• Power expenditure to steer, brake-declutching scheme
• Articulated vehicle steering diagram
• Types of articulated vehicle
• Comparison with skid steer, advantages and disadvantages.

1.6) Model - steady state handling vehicle with trailer
• Model of the tractor vehicle only
• Kus, steering angle, slip angle, trim angle (quick refresher ½ hour)
• Model introduction with semi-trailer as a basic model
• Subdivision , couple of equivalent semi-vehicles
• Model characterization
• Articulation angle
• Gain of the articulation angle as a parameter
• Examination of possible cases of steady state behavior
• How to extend the model to other types of vehicle-trailer combination.

1.7) Industrial vehicle " air" suspensions
• Load problem
• Suspensions: Real and equivalent deflection
• Related problems
• Real gaslaws and pneumatic cylinder, curves, preload.
• Constant volume constant mass approach
• Air springs: Effective area and its variation, spring curves
• Historical and current types of air springs and installations

2) Characteristics of the driveline of special vehicles and their design (Layout).

2.1) SHORT introduction to industrial vehicles
• Industrial vs commodity
• The vehicle's mission
• Global yield / price / cost
• Segmentation of the pivot market-vehicle
• Turnover analysis / example (because the project often can not be the technical optimum)
2.2) The performance of an industrial vehicle and the concept of mission
• Comparison with the car
• Short presentation of families for industrial and special vehicles depending on the mission
2.3) The missions of industrial and special vehicles (and list of key and specific components)
• Transport vehicles
o Trucks: distribution, medium and long haul
o Buses: urban and suburban
o Dumper
o Forklift
o Telescopics
o Military transport vehicles
• Tractors
or generic tractor
o Tractor "trac" for transport
o Vineyard / orchard tractor
• Other agricultural machines
or Combine
o European forestry machine (harvetser and forwarder)
o American forest machine (skidder)

• Construction Machines
o Wheel loader and track loader
o Compact loader (skid steer loader)
o Wheeled and tracked excavator
o Terna (Backhoe loader)
o Apripista (Dozer)
o Compactor roller
o Truck mixer
o Paver
o Grader
2.3) NOTES on the diesel engine for SV and IV
• Cycle / yields / specific consumption and maps
• Dual-fuel diesel (advantages and disadvantages)
• The concept of positioning at operating point, how diesel is used in operating machines.
• Possible future developments in operating and special machine applications
2.4) The individual components of the driveline (morphology, behavior, technique)
• Torsional vibration dampers
• The joints
• Hydraulic coupling and torque converter coupling with and without freewheel on the stator (introduction)
• The hydraulic and electric retarder
• Clutches
• Types of gears and cutting types (Gleason, Klingelnberg ...)
• Epicycloidal rotation, single, double, Ravigneaux
• Synchronizers
• Bearings for gearboxes and axles and sealing rings
• Lubrication schemes of gears and bridges, types of oil
• BRIEF Recovery of the concept of fatigue
2.5) hydraulic transmissions: hydrokinetic and hydrostatic
• hydrokinetic
o Hydrokinetic (torque converter)
o Disadvantages and advantages, coupling with power-shift gearbox
o Sizes, transmission ratio, conversion ratio, yield
o Hydraulic coupling: Structure, functional analysis, point of operation
o Torque converter: Structure, functional analysis, operating points, The "trilock"
o From the stall to lock-up
o Absolute functions in the VI / VS from the torque converter
o The coupling to the endothermic engine ("free", "bound", "stifled"), how to choose it?
o Torque converter and gearbox
• hydrostatic
o Components of a system, fixed and variable displacement pumps
o Open and closed circuit, differences and effect on the vehicle, schemes and pressures, advantages and disadvantages.
o Types of pump and motor regulation (DA and HA)
o" Conversion"
o Basic driveline schemes with hydrostatic transmission
o Special schemes for some vehicles
o Solutions with double hydraulic motor
• Comparison between the 2 transmissions.
2.6) The concept of "equivalent engine"
2.7) The change as eta = mu per tau
2.8) CLASSIFICATION OF THE CHANGES
(with analysis and reading of drawings and overall design)
• By type of power transmission
• By type of drive
• Simple plug-in / A synchronizer / multi-clutch clutch (industrial powershift type) / Dual clutch
• Cascade / countershaft / a more countershafts
• Automotive gearboxes, schemes and typical designs
• Manual transmissions for IV
• Basic gearbox / splitter / range
• Double countershaft, Fuller design
• Medium and heavy trucks
• Cam sequential gearboxes
• Automatic or semi-automatic changes
• By law of gear change
• Typical drawing scheme for:
o Trucks and buses
o Agricultural tractors
o Offroad and earth movement transport
or CVT for light and medium vehicles
2.9) Power split transmissions
• Traditional and innovative power splits (double epicycloidal etc ..),
• Drawings reading, diagrams and operating diagrams
2.10) The axle (with views and sections)
• Mission
• axle construction
• Supporting or just twisting shafts
• CHARACTERISTIC TYPES OF THE AXLE
• Single or double reduction AXLE
• Possible reduction before the differential
• Portal AXLE and inverted portal
• Double hollow-construction bridge
• Bogie
• Conical torque sizing
• Common aspects and reusability
• axle concept (N = F x V)
2.11) Examples of bridges for IV and SV drawings with reading