Chapter IV

In the fourth chapter the procedure of definition of lift-load truck’s operating efficiency in service mode has been carried out.
Service mode of work was divided into operations, which consist of elements.
That fact made it possible to build optional operating cycles from the elements and to investigate the influence of various factors on the operating efficiency of lift-load truck taking into account the mathematical model of operation and movement.
Thus the increase of load mass on forks causes the increase of fuel waste. However the increase of fuel waste is less than the increase of transport load mass (Fig.1). Thus, the increase in the amount of transport load courses the saving of specific usage of fuel.

Fig.1. Change in fuel waste according to transport load weight
1 – movement without load
2 – mass of load 1000 kg
3 – mass of load 1500 kg
4 – mass of load 2000 kg

The change of load center mass position, i.e. its shift along the longitudinal cross-sectional surface with respect to the back wall of the carriage courses a change in the value and frequency of vibration acceleration at the points of the lift-load truck. It tends to appear in the back part of the vehicle body.
It is observed that change in waste fuel is not enormous.
Fuel waste increases at the extension of the transportation shoulder; the increase of load mass is greater than the increase in fuel waste, i.e. it is more convenient to use lift-load trucks at maximum weight coefficient usage.
At intensive acceleration, the fuel waste is greater and the fork lifter usage of kinetic energy increases. It is possible to reduce the fuel waste and to increase the vehicle’s fuel savings at further free-wheel coast. At application of the lift-load truck’s brakes with varying intensity, it was observed that braking with greater intensity is more economical.
The change in fuel waste depending on the various lift-load truck’s acceleration and speed at which resonance condition appear have been investigated by means of a mathematical model of operation and movement.
The dependence of fuel waste at different speeds and at different coefficients of resistance to rolling has been determined by the investigation of road conditions.
The examination of load processing dynamics has shown the dependence of fuel waste on vertical transportation speed.
The influence of load weight and its position on the operating efficiency of the lift-load truck and its influence in the cross-section of the vehicle have been further investigated in the fifth chapter.
Several ways of improving of operating efficiency at the design level (see publications on the subject of the dissertation) have been suggested on the basis of the analysis of the negative influence of the load on the operating efficiency of lift-load trucks.
One of the patents has been realized at the stage of creation of lift-load truck with the experimental carriage.
The peculiarity of full-scale experiment was that weight center of the load can be shifted in the horizontal cross-section direction.
Thus, a special procedure and investigation program has been worked out for the definition of the operating efficiency of a lift-load truck with an experimental lifter. A new technological cycle of lift-load truck operation has been created for realization of possibilities of a new fork lifter. The positioning of the fork with reference to loads and load with respect to recess as well as load alignment have been suggested as the main peculiarity of worked out cycle.
One of the main parameters that specify the vehicle’s efficiency is the productivity of its work (Fig.2), and the fuel waste (Fig.3).

Fig.2. Lift load truck productivity according to mounted equipment:
I – fork carriage
II – side shift carriage
III – experimental carriage with side shift of fork
1 – medium condition of work
2 – speed up condition of work

Fig.3. Fuel waste according to mounted equipment:
I – fork carriage
II – side shift carriage
III – experimental carriage with side shift of fork
1 – medium condition of work
2 – speed up condition of work

The results of the experimental analysis showed that productivity increased due to:
• reduced duration of load holding
• possibility of manipulation of load (not lift-load truck at stocking)
• usage of load alignment at lift-load truck’s movement .
The worked out hydraulic diagram of fork lifter allowed the shift of every fork and also usage of their parallel shifting that made the reduction of time of load holding possible by two times at experimental lifter usage, and the load alignment usage has increased the stability of lift-load movement (Fig.4).

Fig.4. Relative shift of lift load truck in rectilinear movement according to load location:
1 – movement without load
2 – movement with centripetal load
3 – weight center shift for 100 mm
4 – weight center shift for 200 mm