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Electromechanical Transmission of Skid Steer Loader

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The article analyzes the power train components of skid steer loaders. The choice of the scheme and the design of the transmission units of the loader with a traction electric drive is substantiated. The results of calculating the traction characteristic of the straight-line movement of the loader taking into account different values of the coefficient of resistance to movement are presented.
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Electromechanical Transmission of Skid Steer
Loader
Alexey Khomichev1, * and Alexandr Volkov1
1Kurgan state university, Faculty of Transport Systems, Department of Tracked Vehicles and Applied
Mechanics, 640020, Kurgan, Russia
Abstract. The article analyzes the power train components of skid steer
loaders. The choice of the scheme and the design of the transmission units
of the loader with a traction electric drive is substantiated. The results of
calculating the traction characteristic of the straight-line movement of the
loader taking into account different values of the coefficient of resistance
to movement are presented.
1 Introduction
Currently, there is a trend towards the transition of vehicles to alternative environmentally
friendly energy sources, one of which is the electric motor. Many works have been devoted
to the creation and application of vehicles with a traction electric motor. [1-7] Machines
with an electric motor also exist in the field of municipal cleaning and road construction
equipment. [8-11]
Skid steer loaders are used in the construction and repair of roads, maintenance and
cleaning of urban areas, in warehouses. Under these operating conditions, the use of a
traction electric motor instead of an internal combustion engine is preferable due to its
advantages:
- Zero emissions, which has a positive effect on the ecology of cities and allows you to
work indoors.
- Almost silent operation, which also has a beneficial effect on the environment and
allows you to use the forklift at night and early morning hours.
Modern skid steer loaders are equipped with a diesel internal combustion engine and
hydrostatic transmission. [12] To create a loader with an electric traction drive, it is
necessary to replace the hydrostatic transmission with an electromechanical one.
2 Purpose and objectives of design
The purpose of the skid steer loader design is to create a machine that will match the
performance of an internal combustion engine loader. For the developed loader, it is
necessary to justify the choice of the following components:
* Corresponding author: khomichev.alexey@mail.ru
MATEC Web of Conferences 346, 03063 (2021)
ICMTMTE 2021
https://doi.org/10.1051/matecconf /202134603063
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative
Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).
- Traction electric motor - an electric motor designed to propel vehicles by converting
electrical energy stored in storage devices into mechanical energy.
- Mechanical gearbox designed to reduce the number of revolutions, convert torque and
transmit it to the drive wheels.
- Parking brake designed to hold the loader in place when the traction motor is powered
off.
3 Traction motor selection
For loaders equipped with a hydrostatic transmission, two hydraulic motors are installed -
one on each side. This solution allows for the best implementation of the side turning
scheme. It is also advisable to use two traction motors on the designed loader. Comparison
of the technical characteristics of the skid steer loaders power train components is presented
in table 1.
Table 1. Technical characteristics of the transmission components
Name
MKSM-800Н
Termit 1000
Developed loader
Motor type Axial piston Radial piston
Permanent magnet
synchronous
Motor model
MPA-33
MS 05
EMRAX 228
Rotation speed, rpm
1500
220
3000
Rated power, kW
19,2
29
28
Maximum power, kW
64,4
50
100
Rated torque, N*m
121,6
2285
120
Maximum torque, N*m
183,6
3200
230
Efficiency, %
86
89
92 … 97
Diameter/width, mm
190/340
232/206
228/86
Weight, kg
30
41
12,4
Based on the results of a comparative analysis of electric motor [5] and traction
calculation, the EMRAX 228 electric motor was selected. The selected electric motor, with
its small dimensions and weight, has high values of the developed power and torque. [13]
View and section of the EMRAX 228 electric motor is shown in Figure 1.
Fig. 1. The view and section of the electric motor EMRAX 228
MATEC Web of Conferences 346, 03063 (2021)
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4 Calculation of the traction characteristic and the choice of the
kinematic scheme of the transmission
The mechanical part of the transmission of loaders with a hydrostatic transmission includes
a gearbox designed to increase the torque and transfer it to the wheels of the machine. The
type and number of gear stages is determined by the value of the torque on the shaft of the
hydraulic motor.
To provide the required tractive effort on the wheels of the MKSM-800H loader, in
combination with axial piston hydraulic motors, four-stage gear reducers are used,
including one bevel gear and six spur gears. The hydrostatic transmission of the
Termit 1000 loader uses high-torque radial piston motors and chain drives. The maximum
travel speed of these loaders is 12 km/h. Loader transmission parameters are shown in the
table 2.
Table 2. Skid steer loader transmission parameters
Name
MKSM-800Н
Termit 1000
Developed loader
Number of gear
4
1
2
First stage transmission
type
Bevel gear Сhain drive Planetary gear
Second and subsequent
stage transmission type
Spur gear Сhain drive
Gear ratio
21,1
2,5
16,2
Based on the analysis carried out in the transmission of the developed loader, it was
decided to use a planetary gear as the first stage and a chain drive as the second stage. This
allows you to provide the required tractive effort on the wheels of the loader, as well as to
achieve the following advantages:
- Higher efficiency compared to multistage gearbox.
- Less noise generated by chain drive.
- The possibility of unification of chain drive units with a serially produced loader.
The kinematic diagram of the transmission of the developed loader is shown in
Figure 2.
Fig. 2. The kinematic diagram of the loader transmission
MATEC Web of Conferences 346, 03063 (2021)
ICMTMTE 2021
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The transmission ratio has been selected to provide the required traction force and the
maximum travel speed of the loader. In this case, the gear ratio of the planetary gear was
calculated based on the possibility of unification with the chain drive of the Termit 1000
loader. For the selected traction motor and transmission kinematic scheme, the traction
characteristic was calculated.
The results of calculating the dynamic factor are shown in Figure 3.
Fig. 3. The dynamic factor of the skid steer loader
Analyzing the results obtained, the following conclusions can be drawn:
1) the maximum travel speed of the loader on the asphalt concrete road (rolling
resistance coefficient f = 0.018) 24.8 km/h;
2) the maximum speed of the loader with a load on a dry dirt road (rolling resistance
coefficient f = 0.15) 8.9 km/h;
3) the maximum speed of a loader with a load on wet sand or virgin snow (rolling
resistance coefficient f = 0.3) 4.5 km/h;
4) the maximum traction force on the loader wheels 19693 N (when the electric motor
is operating at a short-term characteristic).
5 Justification and selection of the design of transmission
components
5.1 Planetary gearbox
To ensure the required gear ratio, a planetary gearbox scheme with a fixed epicycle and a
carrier as an output link was chosen. The module and the number of teeth of the gears were
selected in such a way that the overall dimensions of the gearbox housing did not exceed
the height of the chain drive housing and provide the possibility of assembling the gearbox
in the loader frame. At the same time, the necessary safety factors were also provided.
View and section of the planetary gearbox is shown in Figure 4.
MATEC Web of Conferences 346, 03063 (2021)
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5.2 Parking brake
In the hydrostatic transmission of skid steer loaders, the parking brake is mounted on the
motor shaft. Typically, this is a normally closed, hydraulically controlled multi-disc friction
unit. The Belleville spring acts through the piston on the friction plate pack, thereby
creating the necessary braking torque to hold the truck in place. After starting the engine
and supplying the working fluid with the required pressure to the brake booster, the piston
moves and stops compressing the friction discs. In this case, the shaft of the hydraulic
motor can rotate, and the loader can start moving.
The designed loader also uses a normally closed multi-disc parking brake. It is located
inside the body of the planetary gearbox and, when the power supply of the loader's
electrical system is turned off, it holds the planetary carrier stationary (Figure 4).
Fig. 4. The view and section of the planetary gearbox
To disengage the parking brake, the working fluid of the hydraulic system of the
working equipment of the loader is used. The fluid supply to the brake booster is carried out
by a pump driven by an electric motor operating from a voltage of 12V.
When the power of the on-board network of the loader is turned on, self-diagnosis of the
machine systems takes place, the electric motor 6 turns on and the pump 7 starts to supply
the working fluid through the blocking valve 8 to the tank 9 (Figure 2). After disabling the
loader movement blocking valve 8 goes to the "work" position, the working fluid is
supplied under the required pressure to the boosters 3 of the brakes of the left and right
planetary gearboxes 2. Electric motors 1 can transmit torque through planetary gearboxes 2
and chain drives 4 to wheels 5 of the loader.
6 Conclusions
As a result of the analysis, calculations and design studies for the developed loader,
EMRAX 228 traction motors and the mechanical transmission, which includes a planetary
gearbox and a chain drive, were selected. The design of a parking brake with an electro-
hydraulic cut-off drive is proposed.
The power plant and transmission allow the loader to develop a maximum tractive effort
of 19693 N, a maximum speed of 24.8 km/h on an asphalt road, and a maximum speed of
8.9 km/h with a load on a dirt road.
The obtained characteristics are superior to most of the implemented designs of skid
steer loaders with an internal combustion engine and hydrostatic transmission. Maximum
MATEC Web of Conferences 346, 03063 (2021)
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travel speed over 15 km/h for a loader with a hydrostatic transmission is only possible when
using two-volume hydraulic motors. The developed loader achieves an optimal
combination of traction and speed characteristics, which results in a more versatile and
efficient machine.
References
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house of MSTU im. N.E. Bauman, 2017, - 240 p.
3. Fundamentals of electric drive: textbook / А.B. Krasovsky. - Moscow: Publishing
house of MSTU im. N.E. Bauman, 2015. 405 p.
4. K. Evseev, A. Dyakov, V. Pushtakov, Analysis and design solutions for a 4x4 ATV
with an electromechanical transmission. MATEC Web of Conferences 329, 01022
(2020). DOI: 10.1051/matecconf/202032901022.
5. K. Evseev, A. Dyakov, K. Popova, Analysis of the electric motor and transmission
for a 4x4 ATV. MATEC Web of Conferences 329, 01019 (2020). DOI:
10.1051/matecconf/202032901019.
6. Y. Sun, M. Li, C. Liao, Analysis of wheel hub motor drive application in electric
vehicles. MATEC Web of Conferences 100, 01004 (2017). DOI:
10.1051/matecconf/201710001004.
7. J. Caban, J. Vrabel, B. Šarkan, J. Zarajczyk, A. Marczuk. Analysis of the market of
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8. https://www.kovacoelectric.com/en/elise-900
9. https://www.buchermunicipal.com/int/products/sweepers/compact-sweepers/citycat-
v20e
10. https://www.tenaxinternational.com/en/prodotto/electra-2-0-evos/
11. https://dzero2.dulevo.com
12. A. Khomichev, A. Volkov Chassis design of skid steer loaders. IOP Conf. Series:
Materials Science and Engineering 709, 033012 (2020).
13. https://emrax.com/e-motors/emrax-228/
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Publishing house of MSTU im
  • G M O Kotiev
Design of car transmissions: Handbook / Under total
Design of car transmissions: Handbook / Under total. ed. A.I. Grishkevich. -M.: Mechanical Engineering, 1984, -272 p.