MEAN RATING

%
SELECTED OPERATING PARAMETER

KEY

EBB Experienced operator
T inexperienced operator

Figure 17.—Mean ratings of experienced versus inexperienced operators for selected operating param-
eters of full-floating, end-cab SC (excellent = 5, very good = 4, good = 3, fair = 2, poor = 1).

2.83 to 2.33, respectively. The experienced operators also
gave a higher rating for the hand controls, maneuvering to
dump, and the effectiveness of the video system. The low-
est rating is shown for tramming inby, where the experi-
enced operators gave a 1.83 rating compared with 2,17 for
the other operators.

Discussion
Difficulties .
The difficulties test subjects experienced at the outset
of a test session concerned the following: visibility tram-

ming inby, adjusting to the steering (mancuvering or han-
dling) of the SC, becoming accustomed to the speed of

travel, judging to make turns, the plowing and dragging
action of the cab, judging the location and orientation of
the SC with respect to the mine entry and crosscut, and
the fore-and-aft adjustment of the seat. In the majority of
cases, however, these diminished, at least somewhat, by the
end of the test session. Thus, it is reasonable to conclude
that these difficulties would continue to diminish over time
with increased experience and familiarity of operating the
end-cab SC,

Strengths and Weaknesses

The strengths and weaknesses of the full-floating, end-
cab SC as perceived by the test subject operators are as
follows:


"woyshs ounesphy OS PeUIPOW—"6 e:nBi4

a 6

AT@WaSSY YOsszuaHOD UV



175

150

125

100

75

CUMULATIVE RATING SCORE

50

25

KEY

@ Ful floating

(CI Portiat floating 4

Figure 21.—Total rating scores of experienced operators comparing
full-floating and partial-floating, end-cab SC. (Test subject 1 Is an
Inexperlenced operator. Test subject 2 is the operator with low-coal

experience.)

REFERENCES

1. Lindahl, P, D., and K. L, Whitehead. Cost Benefit Analysis of
Low-Coal Cabs and Canopies (contract J0199005, Bitum. Coal Resch.,
Inc). BuMines OFR 124-85, 1983, 144 pp; NTIS PB 86-138930.

2. Aljoe, W. W., and K. L. Whitehead. Analysis of Low-Coal Cabs
and Canopies (contract 30199005, Bitum. Coal Resch., Inc.). BuMines
OFR 109-85, 1981, 306 pp.; NTIS PB 86-153574,

3. Hartley, C. A Study to Determine the Feasibility of Providing
Adequate Human Engineered Operator's Cabs in Thin Seams Through
the Use of a Remotely Positioned Operator, v. 1 (contract 50308038,
Bendix Corp.), 1981, 131 pp; available upon request from A. G. Mayton,
BuMines, Pittsburgh, PA.

4, Mantel, J. Development and Assessment of New and Existing
Canopy Technology to Lower Coal Seams (contract H0387026, ESD
Corp.). BuMines OFR 7-86, 1985, 99 pp.

5. Mayton, A. G., J. R. Bartels, and W. D. Mayercheck. Novel
Design for a Thin-Seam Shuttle Car Featuring an Ergonomic Oper-
ator Compartment. Min. Eng. (Littleton, CO), v. 41, No. 11, 1989,
pp. 1132-1134,

6. Bartels, J. R, A. J. Kwitowski, and W. D. Mayercheck. Integrated
Compartment-Machine Design for Low-Coal Shuttle Cars. BuMines
1C 9200, 1588, 18 pp.

. Protective Structures for Low-Coal Shuttle Car Operator.
puting Ri RI 9143, 1987, 22 pp.

8, Kwitowski, A. J., and R. J. Gunderman. Development of a Pro-
tective Operator Compartment for a Thin-Seam Mobile Bridge Carrier.
BuMines IC 9093, 1986, 27 pp.

9. King, R. H., and S. C. Suboleski. Opportunities for Continuous
Mining Productivity Improvements. Min. Eng. (Littleton, CO), v. 43,
No. 10, 1991, pp. 1226-1231.


ILLUSTRATIONS—Continued

20. Mean ratings of four experienced operators comparing standard side-cab SC with full- Aoatng and
partial-floating, end-cab SC ..... 0. ces ecseeceetseeeeeeuseuees a
21. Total rating scores of experienced operators comparing full-floating and partial

TABLE

1. Specifications for retrofitted 21SC JOY SC and end-mounted operator cab .......... beeeee

UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT
cfm cubic foot per minute in inch
°F degree Fahrenheit Ib pound
fpm foot per minute mph mile per hour
ft foot psi pound per square inch
ft? square foot psia pound per square inch, absolute
fe cubic foot psig pound per square inch, gauge
h hour Vac volt, alternating current
hp horsepower Vdc volt, direct current



Strengths Weaknesses
1. Visibility outby. 1. Visibility inby.
2. Space in the cab, 2. Use of the video system.
3. Seat and ride comfort. 3. Plowing-dragging of cab.
4, Control layout and 4, Full-floating bracket ob-
operation. structs view inby when
cab "floats" downward.
5. Operator more out of dust 5. Exposure to end collision.

Produced from CM.

6. Operator protection (from 6.
ribbing hazards partic-
ularly).

7. Increased production from 7.
extended cut mining (per-
ceived by one test sub-
ject).

Cramped space for large
operators.

Extra maneuvering to dump.

The strengths noted were unrestricted visibility tram-
ming outby, space in the cab, a relatively unjarring ride,
position and relative ease of using the hand and foot con-
trols, and operator protection. The low-coal SC operator
expressed the latter two strengths as “it’s got a really
compact kitchen" and the end-mounted design "... is really
a benefit, because it keeps you out of a lot of danger."
From his viewpoint, the end-cab SC took less effort to
operate because of the control movement and layout and
no change in seating position. He added that with a side
cab, an operator is often out from under the canopy in
order to see, and thus is exposed to pinching-squeezing
hazards from the rib, posts, cribs, etc.

In contrast, the major weaknesses indicated were visibil-
ity tramming inby empty and loaded, depth perception in
using the video system, steering, and plowing-dragging of
the cab and its effects. Other weaknesses noted were the
cab “floating” below ground level, resulting in an obstruct-
ed inby field of view for the operator; more exposure of
the operator on the outby side to a collision with another
vehicle, rib, etc.; cramped space for larger operators; and
the extra maneuvering necessary to discharge the load.

Furthermore, test subjects were asked about whether
they felt the end-cab SC would hinder or enhance produc-
tion, All but one felt it would hinder production in view
of the weaknesses noted above. In summary, the general
feeling of the test operators, particularly the experienced
ones, was that the full-floating end cab needed some defi-
nite improvements before it was fit for production use.

Recommended Improvements

The test operators were asked to suggest how the end-
cab SC could be improved. The suggested improvements
for the full-floating, end cab are

1, Improve visibility for direct and video camera
viewing.

2. Move camera panning control lever on underside
of canopy several inches inby to eliminate head bumping
hazard.

3, Restrict downward travel of cab “floating” to elim-
inate visual obstruction and plowing-dragging action, and
for better maneuvering.

4. Provide more space in cab for larger operators.

5. Modify control locations and use smaller central
panel for all controls to better optimize cab space, reach,
and ease of operation.

6. Relocate conveyor clutch control more toward foot
of cab, and weld extension arm on it or make control hand
operated.

7. Drill holes into bottom of compartment for drain-
age of water.

8. Repair steering and change to more conventional
style such as an orbital unit.

9. Employ color cameras and monitor to enhance vis-
ual perception with video system.

10. Modify location for movable video camera and pro-
vide movement capability for stationary camera.

11. Offset cab toward cable side of SC relative to con-
veyor to improve visibility.

12. Improve seat to allow for finer incremental
adjustment.

13. Provide a panic bar instead of a button for easier
reach and operation.

14. Raise cab higher to improve visibility.

Partial-Floating End-Cab Trials

With results of the full-floating trials in mind, a second
set of trials was conducted with five test subjects from the
first trials: four experienced operators and an inexperi-
enced operator. Considering the suggested improvements
above, the float mechanism of the end cab was altered to
limit downward travel (fig. 18). This was done easily and

Figure 18.—Stops welded to inner section of sliding brackets
for partial-floating end cab to prevent downward movement.


KEY

Full floating
Partial floating

MEAN RATING

END-CAB SC OPERATING PARAMETER

Figure 19.—Mean ratings of five test subjects comparing full-floating and partial-floating,
end-cab SC (excellent = 5, very good = 4, good = 3, falr = 2, poor = 1).

KEY

B Full floating
TG Partia! floating

MEAN RATING

END-CAB SC OPERATING PARAMETER

Figure 20.—Mean ratings of four experienced operators comparing standard
side-cab SC with full-floating and partial-floating, end-cab SC (much better = 5,
better = 4, same = 3, worse = 2, much worse = 1).


load of run-of-mine (ROM) coal, trammed outby with the
load along the main entry, made turns into the right hand
and left hand portions of the crosscut, and completed the
simulated duty cycle by dumping the load onto the ROM
coal pile. After operators had completed their test
sessions, they were interviewed using the questionnaire.

Loading

Initially, plans were to load the shuttle car with a used
low-coal CM, a Jeffrey 101 MC. However, the stub tail
boom of the CM (designed for use with continuous haul-
age) did not provide the reach or the clearance for ef-
fective straight and side loading. Loading, therefore, was
accomplished with a John Deere 544B FEL. Attempts
were made to ensure the manner in which the SC was
loaded approximated that of an actual underground mining
situation, This was done with the FEL loading the shuttle
car from the side and piling coal into the modified boom
end of the machine. When the coal pile on the conveyor
reached a certain level, the SC operator would jog the
conveyor in reverse to move the coal pile into the empty
end of the SC. This process was repeated until the coal in
the SC reached the cab end of the conveyor. The operator
would then tram outby and eventually end up at the dump
point to discharge the load.

Haulage Capacity

Before trials began with the test operators, an attempt
to evaluate the capacity of the SC was made using specifi-
cations from the manufacturer and a pair of portable truck
scales (fig. 13). The SC was weighed empty using the
scales under one set of wheels at a time. The weight of

ete

Figure 13.—Portable scales to weigh loaded, end-cab SC.

the empty SC was 29,800 Ib. Weighing the SC with three
separate loads produced ROM coal weights of 12,850 Ib,
8,700 Ib, and 11,050 Ib. JOY’s specification for load ca-
pacity of the model 21SC having 56-in-wide conveyor with
6-in side boards was 8,750 Ib. Thus, the capacity of the SC
was not diminished by modifications and the "unorthodox"
style of loading and met or exceeded the manufacturer's
specification,

Trials With Full-Floating End Cab

The SC was first tested with the compartment function-
ing in the full-floating condition; ie., the cab could "float"
upward and downward relative to the frame of the SC.
Observing the trials and responses from the test operators
led to the conclusion that this arrangement had some
serious shortcomings. The cab tended to plow the coarse
and fine gravel overlying the red dog and clay bottom of
the test course. This affected maneuvering the SC signif-
icantly. Moreover, the outer member of the sliding brack-
ets welded to the SC became a visual obstruction for the
operator when the cab moved to a level lower than the SC
frame (fig. 14). Furthermore, the plowing action of the
cab, the accompanying noise, and the less than desirable
steering adversely affected the concentration, confidence,
and subsequent performance of each operator to one
extent or another.

Results From Testing Full-Floating End Cab

Figure 15 shows the total ratings for the 12 test subjects
for 33 selected parameters of the full-floating, end-cab SC.
The histogram shows that the experienced operator in low
coal had the highest cumulative rating of all test subjects

Figure 14.Full-floating end cab plows bottom and causes
visual obstruction.


Figure 4.—Sliding brackets that connect end-mounted cab to SC (top and bottom).


INTRODUCTION

Historically, performance criteria such as hauling capac-
ity and tramming clearance have been emphasized in shut-
tle car (SC) design. The operator cab (platform or com-
partment) and the ergonomic needs of the operator have
been assigned a lesser priority. Experience shows this
design approach results in a cab that imposes unfa
conditions on the operator: less than adequate vi ty
causing the operator, at times, to lean out of the cab
(fig. 1); often confining and cramped conditions causing
awkward operating postures; and exposure to shocks as
the vehicle moves over rough bottom.

The U.S. Bureau of Mines has done contract and in-
house research to improve operator cab and canopy design
as part of the Bureau’s mission to enhance the safety and
efficiency of mining methods (1-8).? As a result of recent
research, the Bureau now offers an alternative for SC op-
erators in low-coal mines. A goal of the research de-
scribed in this report is to ensure full canopy protection
from roof falls and to minimize the likelihood of pinching-
squeczing accidents involving the roof or rib. Another

{talic numbers in parentheses refer to items in the list of references
at the end of this report.

goal is to develop a cab design that meets the ergonomic
needs of the operator. Consequently, this research has
resulted in a new SC configuration featuring the Burcau-
prototype transverse-mounted operator cab that is usable
in coal mines with 40-in working heights. The operator
cab, with its novel position and orientation, offers the
following improvements over a traditional operator cab
and cab location: improved operator visibility, protection
from roof falls and pinching-squeezing accidents, effective
reclining seat for comfort and protection from shock and
vibration, and sufficient working space to avoid awkward
and cramped operating postures.

In May 1990, the Bureau entered into a cooperative
agreement with Peabody Coal Co.’s Sunnyhill Mine near
Lexington, OH. Under the agreement, the mine provided
a used 440-V-ac 21SC JOY SC? (fig. 2) for retrofitting the
Bureau operator cab.

3Reference to specific products does not imply endorsement by the
US. Bureau of Mines.

Figure 1.—Operator must lean out of cab because field of view is blocked.


TRANSVERSE-MOUNTED END-CAB DESIGN
FOR LOW-COAL SHUTTLE CARS

By Alan G. Mayton'

ABSTRACT

A prototype end-cab shuttle car (SC) design has been developed to improve protection and address
ergonomic concerns of the SC operator in low coal mines. The new design features an end cab
transversely mounted to the SC and equipped with a closed-circuit video system. The end cab was
retrofitted to a low-coal SC and evaluated in surface trials at the U.S. Bureau of Mines. During surface
trials, test operators evaluated the end-cab SC relative to visibility; cab features—space, seating, controls,
and operator position; tramming—inby, outby, and turning corners; and dumping, Trials were conducted
using 12 test subjects; 6 were experienced SC operators. Results of the trials were promising. Of the
experienced operators, the only operator with low-coal experience gave the new design the highest
rating. Four experienced operators rated the end-cab design "better" to "much better" than a standard
center-driven, side-cab SC for visibility when tramming, protection from roof and rib hazards, and no
change in seat position with direction of travel. This report discusses research to modify a used 21SC
JOY SC, retrofit the SC with the Bureau-developed end-cab, and evaluate the retrofitted end-cab SC
in surface trials.

1Mining engineer, Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA.


150
KEY
(I Experienced operator
125 [1 inexperienced operator

100

75

RATING SCORE

50

25

123 45 6789 10N 1
TEST SUBJECT
Figure 15.—Total rating scores of 12 test subjects for 33 oper-
ating parameters of full-floating, end-cab SC. (Rating score of
test subject 8 Is based on 32 parameters. Test subject 3 is the
operator with low-coal experience.)

4

with 138 of a possible 165 total points. The second and
third highest cumulative ratings, 111 and 109, were given
by experienced and inexperienced SC operators, respec-
tively. The lowest rating of 79 was given by an experi-
enced operator.

The mean ratings of the 12 test subjects (using a scale
of 1 to 5) for individually selected operating parameters of
the full-floating, end-cab SC are shown in figure 16. The
highest ratings of 3.92 were given for tramming outby in
terms of visibility and the location of the video monitor in
the cab. The third highest rating of 3.83 was recorded for
the foot controls in terms of ease of recognition, reach,
and operation. The hand controls, cab space, and comfort
of the ride were "good" to "very good" with ratings of 3.42,
3.33, and 3.25, respectively. The remaining items in the
figure were rated "fair" to "good" with ratings of 2.00 to
2.83. The lowest rating of 2.00 was recorded for tramming
inby.

A comparison of ratings between experienced operators
and the other test subjects for the same operating
parameters is shown in figure 17. Ratings for the two
groups were similar for a majority of the parameters.
Noteworthy differences in the ratings are shown for
tramming outby, foot controls, comfort of the ride in terms
of the seating, cab space, and operator position relative to
the direction of travel. Here the experienced operators,
compared with the other operators, had the higher ratings,
4.17 to 3.67, 4.11 to 3.56, 3.83 to 2.83, 3.50 to 3.00, and

MEAN RATING

SELECTED OPERATING PARAMETER

Figure 16.—Mean total ratings of 12 test subjects for selected operating parameters of full-floating, end-
cab SC (very good = 4, good = 3, fair = 2, poor = 1).


Table 1.—Specifications for retrofitted 21SC Joy SC
and end-mounted operator cab

Shuttle car:
Unit weight . . 29,800
Overall length 28.2
Frame height (with 6.5-in side boards) . 35
Working height . 40
Width... 118
Conveyor width sin. 56
Conveyor speed . fpm.. 90
Capacity faverage of 3 loaded weighings) fP.. 217
Tram speed . mph .. 5
Ground clearance . - in. 65
Wheel base . . ft. 93
Boom extension sin. 18.5
Turning radius:

Inside. 2 ft, 84

Outside ion 218
Motors:

Traction (2), 160 and 275 V de 20

Conveyor 440 V ac 25

End-mounted operator cab:

Weight tb 8,000
Length .. in 72
Height (lowest canopy position) . in 36
Width ...... in.. 37
Canopy coverage . .in.. 40 by 77
Seat width .... in 18
Cab ground clearance .. . in. 35

CONNECTING OPERATOR CAB

The operator cab is centered end to end at the rear
(hopper end) of the SC and oriented so the operator is

facing 90° to the direction of travel. Connection of the
operator cab to the SC is made with sliding brackets, To
mount the brackets, 5- by 7-1/2-in slots 45 in apart were
cut into the bumper. The sliding brackets are made of
1/2-in rectangular tube stcel. They allow the cab to "float"
along the mine bottom. A 3- by 5-in inner bracket slides
within the 5- by 7-in outer bracket (figure 4 top and
bottom).

The inner brackct has 3/8-in steel welded to each side
for enlarging the perimeter of the inner bracket. In addi
tion, the inner bracket features a 1-1/4-in-wide and 18-in-
long slot through which a 1- by 3-in hardened dow pin
passes. The pin and slot arrangement limits the total
movement of the cab to 17 in and the vertical disengage-
ment between the inner and outer brackets to 9 in, when
the cab moves down relative to the SC, and 8 in the up
direction,

Furthermore, a steel collar, 1 in thick by 2 in wide, and
nearly three-quarters of the perimeter of the outer brack-
et, is used to reinforce the outer brackets.

RELOCATION OF CABLE REEL

Since loading now would take place at the opposite end
of the SC, the power-cable reel and guide-pulley arrange-
ment needed to be relocated. These items were moved
from the right side of the boom (viewing from the new
end-mounted cab) to the former operator compartment
located on the left side of the SC between the wheels.
The cable reel was rotated 90° on end in its new location
to avoid increasing the width of the SC.

Figure 3.—Modified SC conveyor boom.


RI

9471

By Alan G. Mayton

REPORT OF INVESTIGATIONS/1993

Transverse-Mounted End-Cab Design
for Low-Coal Shuttle Cars

United States Department of the Interior

Bureau of Mines



sis

Figure 6.—Explosion-proof enclosure housing a single video
camera.

Figure 7.—Explosion-proof enclosure housing video monitor.

were made intermittently throughout the vibrating interval.
The video components were then subjected to vibration in
the vertical dimension on the computer-controlled vibra-
tion platform at levels of shock and vibration typical of a
SC operating in the "tramming empty’ and “discharging
load" cycles. The other dimensions of SC shock and vibra-
tion (side-to-side and fore-and-aft) were deemed insignifi-
cant for the purposes of this evaluation.

The continuous shock and vibration intervals ranged
from 1 to 7h, with an average interval of 4.6 h of contin-
uous shock and vibration. Shorter periods resulted from
necessary stoppages of the platform primarily because of
a damaged coaxial cable (corrected by relocating the cable
gland in the monitor enclosure), broken and ineffective

clamps for securing the enclosures to the platform, and a
faulty hydraulic cylinder on the vibration platform.

Recordings of shock and vibration were collected from
an operating SC on the production section of an active
underground mine. The "tramming empty" and “discharg-
ing load” cycles represented the most severe conditions of
shock and vibration. Approximately half of the total time
was allotted to vibrating the enclosures in each SC op-
erating cycle. Both the camera and monitor were still
operating at the end of the test with no apparent damage.
In summary, the evaluation shows that the video system
components (with the viscoelastic foam materials used in
the XP enclosures) are capable of withstanding, for a
period of time, some conditions of SC shock and vibration
occurring in an underground mine.

The two video cameras are arranged on the SC so that
one camera is mounted in a fixed position at the end of
the boom. This camera is equipped with a wide-angle
lens, which enables the operator to see any obstacles,
other workers, etc., when maneuvering the loaded SC at
the dump. The second camera is on the opposite side of
the SC and mounted above the controller. This camera
has a 90° panning feature that is designed to operate
remotely with a push-pull cable from the end cab, (The
push-pull cable was not installed for surface trials.) A
selector is located in the operator compartment to permit
the operator to switch scenes on the monitor between the
two cameras.

The monitor, within its XP housing, is mounted to the
left underside of the canopy (looking inby) above the tram
foot pedal. It is held by a stecl-angle bracket and a sliding
mechanism that allows small increments of vertical tilting
and movement in the fore-and-aft direction. Four control
knobs protrude through the front cover of the enclosure
for the on-off, vertical hold, brightness, and contrast
controls.

PNEUMATIC SELF-CLEANING SYSTEM
FOR CAMERA ENCLOSURE WINDOW

Both camera enclosures are equipped with an air-wipe
system to keep dust from accumulating on the enclosure
windows. Air (20 cfm total at 20.7 psia, 68° F) is supplied
by a belt-driven, rotary-vane, oilless compressor powered
with a hydraulic motor. The components of the system in-
clude a diffusion ring and mounting assembly. The dif-
fusion ring has 12 equally spaced, 1/8-in-diameter holes
drilled around its circumference. The holes are drilled at
right angles to the long axis of the enclosure. Air de-
livered by the compressor enters the enclosure through
two inlet ports, 180° apart, in the diffusion ring mounting
assembly and passes on through the holes in the ring. The
hole pattern causes opposing streams of air to strike one
another, creating a high degree of turbulence in front of


Similarly, the cable guide system needed revision. A
roller arrangement was added above and to the side of the
tire nearer the end cab. In addition, cable guide eyes sim-
ilar to the guide on the cable reel spooling device were
added along the sideboard of the hopper. These direct the
cable to a redesigned guide-pulley arrangement that uses
smaller pulleys than the previous arrangement (fig. 5).

CLOSED-CIRCUIT VIDEO SYSTEM

Even though the end-mounted cab significantly im-
proves operator visibility during tramming (not during
loading and dumping), blind areas are not eliminated
entirely. Hence, the need for the closed-circuit video
system. The primary purpose of the video system is to
assist the SC operator in viewing areas blocked by the
loaded coal. The two main instances when SC operators
will use the video cameras are when loading at the miner
to minimize coal spillage and at the discharge area when
their view will be partially obscured by the load. In this
case, the SC operator must rely on the video system a
great deal to maneuver and discharge the load.

The video system consists of two small (palm-size)
monochrome video cameras and a monitor with a 9-in
screen. Each of these is housed in an explosion-proof

(XP) enclosure certified by the Mine Safety and Health
Administration. The enclosures contain viscoelastic foams,
extra-soft and medium, to protect the cameras and moni-
tor from damaging shock and vibration. These materials
were selected after placing the camera and monitor indi-
vidually on pieces of the extra-soft and medium foam ma-
terials, respectively, and observing the static deflection
of the material. Figures 6 and 7 show the XP enclosures
containing one of the video cameras and the monitor.

One video camera and the video monitor were sub-
jected to more than 50 h of shock and vibration in a Bu-
reau laboratory to determine how well they would function
and hold up under such conditions. The 50 h equates to
approximately 10 shifts of SC operation, given a typical 5-h
actual operating time for a SC on a CM scction (9).

The procedures used for the shock and vibration eval-
uation were as follows. Both the camera and monitor, in
their respective XP enclosures, were fastened securely to
the vibrating platform, and a target was placed in front of
the camera. The image of the target was, in turn, trans-
mitted to the monitor screen. The camera and monitor
were checked to ensure that a distinct image of the target
appeared on the monitor screen prior to starting the plat-
form with the selected SC operating cycle. Visual checks
of each enclosure and the image on the monitor screen

Figure 5.—Revised cable reel and cable guide arrangement.


Figure 2Used 21SC JOY SC from Peabody Sunnyhill Mine,

ACKNOWLEDGMENTS

The author expresses his thanks and appreciation to
these employees of the Pittsburgh Research Center, U.S.
Bureau of Mines, Pittsburgh, PA: Albert Brautigam, elec-
trical engineer, for his assistance with design modifications
to the SC electrical system; Joseph DuCarme, mechanical
engineer, for his assistance with redesigning the cable
guide system and designing the end-cab mounting brack-
ets; Robert Allen, mechanical engincer, for his assistance

with design modifications to the SC hydraulic system; and
William Doyak, George Fischer, and Mary Ellen Nelson,
mechanical engineering technicians, for their assistance
with design modifications to the SC boom and the end
cab. The author also thanks JOY Technologies, Inc.,
Mining Machinery Division, Franklin, PA, for supplying
needed technical drawings and other technical information
for retrofitting the SC with the end cab.

RETROFITTING 21SC JOY SC WITH END CAB

To retrofit the Bureau-prototype operator cab effec-
tively, various changes on the 21SC JOY SC were nec-
essary. The main changes or modifications to the SC are
discussed in the ensuing sections of this report. They
concern the conveyor boom, the hopper end for mounting
the novel end-mounted operator cab, and cable reel and
guide arrangement. The ergonomic operator cab and
closed-circuit video system also are discussed.
Specifications for the 21SC JOY SC with end-mounted
operator cab are listed in table 1. The boom modifications
(including the 6-1/2-in high angled sideboards) resulted in
an overall frame height of 35 in measured at the boom.
This height was determined in view of plans to field test
the retrofitted SC in the Peabody Sunnyhill Mine, which
has an average working height of 50 in. In the Sunnyhill
operations, the tail boom of the continuous miner (CM)
required 15 in of clearance between the SC and the mine
roof for side loading of the SC. If the field testing had
been planned for a mine working height of 40 in, the SC
boom would have been modified for a lower overall frame
height measured at the boom. Also, table 1 indicates the

cab ground clearance of 3-1/2 in for surface trials. For in-
mine trials, the clearance would be reduced to 1/2 in.

CONVEYOR BOOM MODIFICATIONS

Owing to its intended use for receiving and discharging
the load, the boom of the SC underwent extensive rework-
ing. The boom was disconnected from the main body of
the machine, and minor repairs were made to the convey-
or deck. The 1/4-in steel sides were replaced with 3/8-in
plate to strengthen it for the abuse expected during the
loading cycle. In addition, 6-1/2-in-high sideboards were
added to the boom at an angle of 40.9° to simulate the
hopper end of the vehicle and to better accommodate side
loading by the miner. Angle iron sections 6 in by 6 in by
1/2-in thick were spaced along the length of the boom and
used to support the angled sideboards. New 1-in steel
plate replaced existing 3/4-in plate to reinforce the ends
on either side of the boom and to serve as a bumper.
Later, two 1- by 2-in bars were welded horizontally across
these plates to enhance bumper capacity and strength.
Figure 3 shows a view of the modified SC conveyor boom.


seemed to carry the most impact for operating the end-cab
SC. In addition, the movable camera mounted atop the
SC controller was moved out toward the edge of the
controller case.

The trials were conducted in a similar fashion to the
earlier trials and the test operators were asked the same
questions from the questionnaire. Results were dramatic-
ally more favorable. Figure 19 shows mean ratings of five
retested operators for the full-floating versus partial-
floating end cab. A twofold increase occurred in the rat-
ing for tramming inby in terms of field of view. Field of
view, in general, also increased nearly a full rating point
from 2.80 to 3.60. Moreover, the steering or maneuvering
and handling of the SC increased from 2.40 to 3.60, al-
though no changes were made in the steering. Further-
more, the rating on the "floating of the cab" increased
nearly twofold from 2.20 to 4.20. All other parameters
show a modest to slight increase attributed to the partial-
floating (upward movement only) of the cab, the elimina-
tion of debris coming into the cab, the reduction of noise
from the dragging-plowing, and the increased familiarity of
the test subjects with operation of the end-cab SC.

The four experienced operators compared both the full-
floating and partial-floating, end-cab SC with the standard
side-cab design. The parameters used in the comparison
are shown in figure 20. Note the high ratings for visibility,
operator position, protection from roof and rib hazards,
and no change in seating position when changing the di-
rection of travel. Mean rating scores of 4.5, "better" to
“much better," were given for these items comparing the

partial-floating, end-cab SC with the standard side-cab SC.
The rating of "same," 3.00, is shown for only the loading
procedure. All other ratings of the partial-floating, end-
cab SC compared with the standard SC are above the 3.0
rating.

Finally, the total cumulative rating scores for the five
retested subjects for the 33 operating parameters were
compared for the full-floating and partial-floating, end-cab
SC. These scores are shown in figure 21. All scores
increased from 10% to 52% and dramatically show the
effect of limiting downward travel of the end cab. In part,
this increase is attributed also to greater familiarity of the
test subjects with operation of the vehicle. The experi-
enced low-coal operator again scored highest in the rat-
ings. Interestingly, the experienced operator who had the
lowest score of the 12 test subjects for the full-floating end
cab had the greatest increase (52%) in the cumulative rat-
ings compared with his score for the partial-floating end
cab. Although his experience was limited to mine working
heights of 60 in or above, his negative view of the end-cab
SC became a very favorable view as a result of making the
end cab partial-floating instead of full-floating,

In-Mine Production Trials

In-mine production trials were planned in conjunction
with the Sunnyhill Mine in eastern Ohio. However, the
mine closed and the company was unable to work out
suitable arrangements with another of its mines.

CONCLUSIONS AND RECOMMENDATIONS

The surface trials of the retrofitted end-cab SC pro-
vided very encouraging results. Although the trials were
not entirely conclusive as to how the end-cab SC will
perform in a production mode underground, they showed
this new design promises definite benefits in safety from
roof and rib falls for the low-coal SC operator. Strong
indicators of this were the comments and ratings by an
experienced low-coal SC operator and other experienced
operators. In the view of these experienced operators, the
end-cab design does enhance significantly operator safety
from roof and rib hazards as well as visibility when tram-
ming. The transverse-mounted, end-cab SC design offers
a more "operator friendly’ alternative to traditionally
designed SC operator cabs in terms of cab space, controls,
seating, and no change in seating position when changing
direction of travel. The closed-circuit video system is an
important feature of this new, alternative SC design in
helping the operator see blind areas obscured by the load
of coal and SC frame. The system, however, will require
some maintenance, and experienced operators may require
additional time to get used to the design. The hauling
capacity of the retrofit SC was not diminished, as shown by

several scale weighings, but met or exceeded the manufac-
turer’s specifications for the unmodified version of the SC.
From a production viewpoint, the end-cab arrangement al-
lows manufacturers to design a wider SC given the space
gained by transferring the operator cab from the side to
the end of the machine. This can result in increased
haulage capacity. Furthermore, the new alternative will
permit mining deeper cuts with a remotely controlled CM,‘
and thus increase the depth of cut by an additional 15 ft
compared with the depth when a center-driven, side-
mounted cab design is used. The only major drawback to
the end-cab design noted is the extra maneuvering needed
to discharge the load. This, however, should be more than
offset by enhanced safety for the SC operator, the produc-
tion benefits noted (wider SC and deeper cuts), and the
operator’s increased familiarity and experience with
operation of the end-cab SC.

The recommendation for future research is to conduct
in-mine evaluation of transverse-mounted, end-cab SC
design.

‘Mining deeper cuts will also depend on ventilation and roof control
considerations.


CONTENTS

Abstract
Introduction .
Acknowledgments
Retrofitting 21SC Joy SC with end cab
Conveyor boom modifications
Connecting operator cab . .
Relocation of cable reel . .
Closed-circuit video system
Pneumatic self-cleaning system for camera enclosure window .
Ergonomic, end-mounted operator cab
Hydraulic and electrical modifications
Surface trials .............55
Test subjects—SC operators . .
Test procedures ........ .
Loading ..............5
Haulage capacity
Trials with full-floating end cab .
Results from testing full-floating end cab
Discussion .. .
Difficulties . .
Strengths and weaknesses .. .
Recommended improvements
Partial-floating end-cab trials
In-mine production trials
Conclusions and recommendations .....
References 0.0.0... 6. cee cece eens

ILLUSTRATIONS
1. Operator must lean out of cab because field of view is blocked . 2
2. Used 21SC JOY SC from Peabody Sunnyhill Mine 3
3. Modified SC conveyor boom 4
4. Sliding brackets that connect end-mounted cab to SC . 5
5. Revised cable reel and cable guide arrangement . . 6
6. Explosion-proof enclosure housing a single video camera . 7
7. Explosion-proof enclosure housing video monitor . . 7
8. Bureau-prototype end-mounted cab for low-coal SC 8
9. Modified SC hydraulic system ........ 9
10. Modified SC electrical system ........ 11
11, Test course for surface trials ................8. 12
12. Test subjects maneuver end-cab SC during surface trials 12
13. Portable scales to weigh loaded, end-cab SC . 13
14. Full-floating end cab plows bottom and causes visual obstruction 13
15. Total rating scores of 12 test subjects for 33 operating parameters of full-floating, end-cab SC 14

16. Mean total ratings of 12 test subjects for selected operating parameters of full-floating, end-cabSC .... 14
17. Mean ratings of experienced versus inexperienced operators for selected operating parameters of full-

floating, end-cab SC . 15
18. Stops welded to inner section of sliding brackets for partial-floating end cab to prevent downward

movement 16
19. Mean ratings of five test subjects comparing full-floating and partial-floating, end-cab SC 18


Difficulty with operating the reversible pump was ex-
perienced when it was first installed and operated. The
pump experienced cavitation caused by suction pressures
in excess of the maximum 2.5 psi specified by the manu-
facturer. This occurred largely because of excessive crack-
ing pressure (6 psi) for 3/4-in check valves, and line losses;
and to a lesser degree because of a partially clogged suc-
tion filter. Remedial action to correct the problem with
the pump circuit included replacing four 3/4-in check
valves with 1-in valves having a cracking pressure of 1 psi,
replacing the 1-1/4-in suction hose and 3/4-in lines with
1-1/2-in hose and 1-in lines, and cleaning the suction filter,
suction tube, and reservoir.

The inby side of the operator cab included a movable
plate to prevent coal from spilling into the cab and onto
the operator. Since the hydraulic control and cylinder for
moving the plate up and down were unavailable, the plate
was tack welded in place for surface trials. Having the
plate in a fixed position proved adequate for the surface
evaluation of the retrofitted end-cab SC.

Electrical modifications included the addition of a trans-
former to power the video monitor and cameras, a revers-
ing contactor, circuit breakers, mounting brackets for the
preceding items, and a modified circuit breaker switch
handle. Two other modifications consisted of unplugging
a spare gland opening in the controller and rerouting a ca-
ble to free up an additional gland opening in the control-
ler, Figure 10 shows a schematic of the modified electrical
system.

Reversing the conveyor also required cutting back about
8 in of the plate extending from the bumper over the tail
end of the conveyor to prevent the conveyor from becom-
ing jammed with pieces of coal or rock. In addition, work
had to be done on the flights for reversing the conveyor.
Several flights on the underside of the conveyor broke off
after being bent severely. Afterwards, thorough lubrica-
tion of the chain curtailed this problem. Other bent or de-
formed flights were removed and replaced with fabricated
ones. Moreover, 2 to 3 in of the conveyor deck was cut
off at the boom hinge shaft to prevent flights from becom-
ing jammed and hung up when reversing the conveyor.

SURFACE TRIALS

At the conclusion of the retrofitting work on the SC
(including debugging of the conveyor pump motor, flights,
and chains), the machine was tested in the Bureau’s Min-
ing Equipment Test Facilities at the Pittsburgh Research
Center (PRC). A 5,076-ft? test course (fig. 11) was set up
to simulate two mine entries and a crosscut. Fluorescent
orange traffic pylons with approximately 6-ft-long sticks
(painted the same color) were used in marking off the
course. The main entry was about 150 ft long. The sec-
ondary entry, adjacent to the main one, was about 35 ft
long. The crosscut was about 100 ft long and included a
20-ft-wide structure that was formerly part of a simulated
mine entry. Widths of the entries and other segment of
the crosscut were 18 ft. The retrofitted SC was evaluated
on information received from 12 Bureau employees at the
PRC, who operated the SC through the test course. A
questionnaire with 9 main questions, providing 54 pieces
of information, was used to gather the information fram
the test subject operators. (Six other questions were add-
ed to the questionnaire later.) Questions covered topics
such as field of view, maneuvering the SC around corners,
tramming inby and outby, tramming loaded and empty, the
closed-circuit video system, cab space, cab "floating," and
seating.

TEST SUBJECTS—SC OPERATORS

The 12 test subjects selected to operate the retrofitted
SC ranged from 30 to 53 years of age; 10 were males and

2 were females. The sizes of the subjects ranged from 5 ft
2 in, 118 Ib to 6 ft, 260 Ib. Six of the twelve subjects were
former SC operators with one having SC operating experi-
ence in low coal. The SC operating experience of these
subjects ranged from 1 to 8 yrs, whereas overall mining
experience varied from 5 to 20 yrs. The former low-coal
SC operator had experience in a mine working height
down to 38 in, whereas the other former SC operators had
experience in mine working heights of 60 in and above.
Two test subject operators had experience running other
heavy equipment such as continuous miners (CM), front
end loaders (FEL), cranes, trucks, and SC on the grounds
of the research center. The test subjects were three coal
miner mechanics from the PRC experimental mine, three
mechanical engineering technicians, two mining engineers,
a civil engineer, a mining industry research specialist, a
training research specialist, and a computer programmer
analyst.

TEST PROCEDURES

Each subject test operator was given an explanation of
the different controls and how they functioned. Then the
operator was given the opportunity to become familiar
with the operation of the retrofitted SC by tramming in
the inby and outby directions and making turns into the
18- and 20-ft-wide crosscut segments (fig. 12). Afterwards
the test operator was instructed to tram inby to have the
SC loaded in the main entry. The operator received a


art a a :
Figure 12.—Test subjects maneuver end-cab SC during surface trials,


Library of Congress Cataloging in Publication Data:

Mayton, Alan G.
‘Transverse-mounted end-cab design for low-coal shuttle cars / by Alan G. Mayton.

p. em. — (Report of investigations; 9471)
Includes bibliographical references (p. 19).

1, Shuttle cars (Mine haulage)—Design and construction. 2. Human engineering.
3. Coal mines and mining—Safety measures. I. Title. I. Series: Report of inves-
tigations (United States. Bureau of Mines); 9471.

TN23.U43 — [TN342] 622's—de20 [622.6] 93-15888 CIP



Report of Investigations 9471

Transverse-Mounted End-Cab Design
for Low-Coal Shuttle Cars

By Alan G. Mayton

UNITED STATES DEPARTMENT OF THE INTERIOR
Bruce Babbitt, Secretary

BUREAU OF MINES


the enclosure window. Laboratory tests have shown that
the air-wipe system, delivering 7.5 cfm at 2 psig of air, will
prevent dust from accumulating on the enclosure window,
and will remove dust that may exist on the window prior
to startup of the air-wipe system. The compressor delivers
approximately 10 cfm of air to each camera,

ERGONOMIC, END-MOUNTED OPERATOR CAB

The operator cab is designed to give the operator more
space to operate the machine from a comfortable operat-
ing position (fig. 8). Original operator controls were
retrofitted from the former operator cab to the new loca-
tions within the end-mounted cab. The controls include
hydraulic for steering, conveyor clutch, and service (foot)
brake; and electrical switches for lights, the pump and
traction motors, conveyor direction, tramming "butterfly’
(foot) pedal, panic bar, and selecting displays between the
two cameras. These controls were placed within the op-
erator cab with the aid of a draft of Proposed Society of
Automotive Engineers XJ1314 Human Factors Guidelines
for Mobile Mining Equipment, January 1, 1991. Addition-
ally, input from two individuals, approximating the larger
(95th percentile male) and smaller (5th percentile female)
operators, was used in pinpointing control locations,
These persons sat in the operator compartment, handled

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the controls, and gave verbal feedback as to the ease in
reaching and activating and deactivating a control lever or
switch. The controls were mounted along either side of
the operator seat within the SC operator’s envelope of
comfort and reach,

The seating in the cab features a reclining contoured
seat with a contoured headrest. The seat pan tilt can be
set at three angular positions; 0°, 11.7°, and 23.4°. Similar-
ly, the seat back positions include 53.1°, 45°, 36.9°, 28.8°,
and 20.7°, Dimensions of the seat and headrest are seat
pan, 15 in long by 18 in wide; seat back, 22 in long by
17 in wide; and head cushion, 5 in high by 10 in long by
4 in wide.

HYDRAULIC AND ELECTRICAL MODIFICATIONS

Other modifications were done concerning the electrical
and hydraulic systems of the SC. These modifications
were necessary to operate the video system with pneumatic
self-cleaning of the enclosure window, to make the convey-
or operate in both directions, and to accommodate the use
of two video cameras.

The hydraulic modifications included replacing the hy-
draulic pump with a reversible pump and adding the air
compressor and hydraulic motor to power it. A schematic
of the modified hydraulic system appears in figure 9.

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Figure 8.—Bureau-prototype end-mounted cab for low-coal SC.


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