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Vehicle/machine design and evaluation

Forest Road Network and Transportation Engineering – State and Perspectives

volume: 38, issue: 2

Trailer Overturning during Wood Transportation: an Experimental Investigation of Effects of Trailer Joint Point and Frame Structure

volume: 39, issue: 1

Trailers may increase the risk of tractor overturn during wood transportation in dangerous
conditions. In this work, tests were carried to simulate a trailer rollover using three two wheel
tractors and a crawler tractor and three trailers (two single-axle and one two-axle), all of their
combinations moving downhill along the path on a short dirt road. The trailers were always
loaded with the same load of logs cut at a length of about 1.5 m and put transversely to the
longitudinal axis of the trailer. During each test, the following parameters were measured: the
lateral dragging of the rear wheels/crawler of the tractor, the ground detachment of the rear
upstream wheel/crawler and both the longitudinal and transversal strains (released over the
tractor hooking system) produced by the trailer overturn. The study highlighted that the biaxle
trailer structure with a turntable steering had the best performances compared to the
single-axle in terms of safety during trailer overturning. Independently of the trailer type
considered in this work, a tied load is more dangerous than a load restrained only by steel
struts, because during the overturn the load forms a single unit with the trailer mass, which
increases the transversal and longitudinal strain.

Determination of Service Life of Sintered Powder Metallurgy Gears in Regard to Tooth Bending Fatigue

volume: 39, issue: 1

The aim of this study is to check the possibility of replacing the pinion gear made of structural
steel with the one made of sintered material. The pinion is part of the gear pair mounted
in front of the gearbox of the skidder Ecotrac 55V to increase the speed and lower torque. In
larger series, powder metallurgy (PM) gears are used as a cost-effective alternative for wrought
metal gears in a number of industries including the one producing forest products. The present
paper discusses the computational and experimental approach for determining the service
life of sintered PM gears in regard to tooth bending fatigue. The proposed computational
model is based on the stress-life approach, where the stress field in a gear tooth root is determined
numerically using finite element method. The needed material data have been taken
from the authors’ previous work. Due to the scattering nature of fatigue, the statistic approach
has also been considered by presentation of computational results. The experimental procedure
was done on a custom made back-to-back gear testing rig. The comparison between computational
and experimental results has shown that the proposed computational approach is an
appropriate calculation method for estimating the service life of sintered gears regarding tooth
root strength. Namely, it has been shown that, in case of proper heat treatment of tested gears,
tooth breakage occurred in the interval with 95% probability of failure, which has been determined
using the proposed computational model.

A Mobile Hydraulic Winch for Use in Small-Scale Forestry

volume: 39, issue: 2

Winches have recently been used to extract timber from forests. Winches are often components
of tractors, but tractors cannot be used on difficult terrain and are generally too expensive for
small forest owners. The current study considers the use of an experimental winch for the
extraction of timber from small plots with difficult terrain. The mobile hydraulic winch used
in this study weighs 50 kg and has a pulling force of up to 53 kN, a 12 V motor, and a 64x224 mm
drum. The associated power unit is a gasoline, single-cylinder, four-stroke, air-cooled KIPOR
KG 390D (400D), 389 cm3 engine, with 7.7 kW of power, and a torque of 22.6 Nm at 2500 rpm.
The engine powers a high-pressure oil pump with an output pressure of 3 MPa and a flow rate
of 60 litres per minute. The input torque of the pump shaft is 25 Nm at 3000 rpm. The hydraulic
winch can be fixed to tree trunks, stumps, or wooden pegs by lashings. The winch was
tested at three locations with different assortments of wood. The results showed that the experimental
winch was practical for timber extraction and that <250 kN of force was needed
for successful extraction. At the test sites, the expense of lumber removal was on average 140%
greater with the winch than with a horse but the advantage of the hydraulic winch is high
pulling force. Because of its small size and low weight, the unit can be easily handled by two
workers, easily moved at short distances in small plots with rough terrain, and easily transported
among plots. With a one-man crew, the percentage of direct costs represented by wages
dropped to 56%, and the percentage represented by fuel increased to 40%.

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Web of Science Impact factor (2017): 1.714
Five-years impact factor: 1.775
Next issue: January 2019

Subject area

Agricultural and Biological Sciences

Category/Quartile

Forestry/Q1