UNITED STATES DEPARTMENT OF THE INTERIOR 
Report of Investigations 9143 

Protective Structures for Low-Coal 

Shuttle Car Operator 

By John R. Bartels, August J. Kwitowski, 

and William D. Mayercheck 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 

David S. Brown, Acting Director 
Library of Congress Cataloging in Publication Data: 

i 

. 

Bartels, John R. 

Protective structures for low-coal shuttle car operator. 

(Report of investigations; 9143) 

Bibliography: p. 21 

Supt. of Docs. no.: I 28.23: 9143 

1. Mine haulagdafety measures. 2. Coal mines and mining-Safety measures. I. 

Kwitowski, August J. 11. Mayercheck, William D. 111. Title. IV. Series: Report of 

investigations (United States. Bureau of Mines); 9143 

TN23.U43 [TN3311 622 s [622'.81 87-600183 
CONTENTS 

. 

Page 

Abstract .............a...........a............................................. 

Introduction ................................................................... Technical approach .......................mmm.m.......m..mm.m..mmm....

Design concepts ................................................................ Limited coverage concepts ...............m.m........aam....mm......m..........

Roll-bar canopy .............m.....m.....m....m..mmm.m.....m.mmmmm..mmm.m.mm.a 

Sliding canopy ......................m.......m..m...m......mmm......m..m

Flip-top-canopy operator compartment ...........m....a......mm..m.......mm.m

Testing ...........................................m...........m..........m..... 

Summary of test results ..............a...........m..mm..m........mm.m.mm

Conclusions ............................a...........a...m.......m............... 

References .............................m.m.m.........m........mm...m..m

Appendix.--Symbols used in this report .....................m.m.m...mm.......... 

ILLUSTRATIONS 

Canopy-to-machine height relationhips ..................................... Operator-head-room-to-compartment-length relationships .................... Coal miner anthropometrics ................................................ Shuttle car seat .........................................m...m.........m.. 

Roll-bar protection ....................................................... Sliding canopy ........................................................m... 

Flip-top operator compartment ............................................. Flip-top compartment in raised position ................................... Sling seat ................................................m...........a... 

Schematic of modified hydraulic system .................................... Human eye reference measurement instrument (HERMI) ........................ Visual attention locations for shuttle car ................................ Roll-bar loadings ......................................................... Structural analysis of roll-bar member 1 .................................. Structural analysis of roll-bar member 2 .................................. Finite-element grid ........................................................ TABLES 

1 . High-speed low-coal shuttle car accidents. 1982-84 ........................ 2 . Specifications for shuttle car. roll-bar canopy. and sliding compartment .. 3 . Specifications for shuttle car and the flip-top canopy operator 

compartment ...........................................m.................. 

4 . Visual attention locations priority scores for shuttle car ................ 5 . Visual attention location score ........................................... 

PROTECTIVE STRUCTURES FOR LOW-COAL SHUTTLE CAR 

OPERATOR 

By John R. Bartels,' August J. Kwitowski,' and William D. Mayercheck2 

ABSTRACT 

This report discusses the Bureau of Mines' efforts to develop partial 

protective structures for operators of low-coal shuttle cars. In coal 

seams 48 in high or less, full-coverage canopies are generally difficult 

or may be impossible to implement on high-speed face equipment due to 

the restrictions they impose on the operator's vision and comfort. Limited coverage is one alternative that provides an acceptable level of 

operator protection in thin-seam applications where conventional fullcoverage canopies cannot be used. Three possible limited-coverage design scenarios (roll bars, sliding canopies, and flip-top canopies) were 

designed, fabricated, and evaluated for low-coal shuttle cars. All 

three designs were determined to be feasible and desirable for low-coal 

shuttle car application. 

'civil engineer. 

'supervisory physical scientist. 

Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
INTRODUCTION 

Since January 1, 1974, cabs and canopies have been required on underground 

face equipment by Federal law (30 CFR 

75.1710) and have been successful in reducing the total number of face equipment 

operator injuries. The Mine Safety and 

Health Administration (MSHA) , U. S. Department of Labor, has estimated that 233 

lives have been saved from January 1971 

through December 1985 (6-7). MSHA has 

also estimated that approximately 70 pct 

of all equipment operator accidents that 

occurred in coal seams 48 in or less 

could have been prevented had protective 

structures been employed on all face 

equipment (6-7). -- 

Through past Bureau programs, adequate 

canopy equipment has been developed for 

application to mining equipment used 

where seam heights are 48 in or less. 

Canopies are used in 48- to 60-in seams, 

but not without problems. In seam 

heights less than 48 in, previous attempts to apply canopy technologies have 

resulted in adverse comments from operators and mine management. Typical problems are reduced visibility and fatigue 

caused by unusual and cramped operator 

positions. 

Although advancements have been made 

to improve operator safety, preventable 

injuries continue to occur. A 1983 study 

showed that there were 616 preventable 

accidents between 1975 and 1978 for 

equipment operated in coal seam heights 

less than 48 in (3). Of the preventable 

accidents, the &st frequent types of 

equipment involved were high-speed face 

equipment such as shuttle cars, scoops, 

and tractors, which accounted for 226 

injuries, or 36 pct of such accidents. 

Successful designs for all equipment 

types have not yet been developed. Face 

equipment such as continuous miners, roof 

bolters, and face drills, are usually 

much easier to equip with protective 

operator cabs and canopies than shuttle 

cars. These types of face equipment perform their functions primarily at one 

location; i.e., a continuous miner extracts coal at the face, whereas shuttle 

cars frequently travel through the working section. Also the tram rate of shuttle cars is significantly higher than 

that of other types of face equipment. 

These factors require that a shuttle car 

be maneuverable and have as much clearance as possible in order to tram through 

the tight spots inthe section. The 

requirement for tramming clearance is opposed by the fact that a primary goal in 

shuttle car design is to maximize the 

amount of cut coal that can be transported from the face. The overall effect of these factors is that space that 

could otherwise be utilized for the operator is used for increased coal capacity 

and tram clearance. 

The limited-coverage technique was developed as a means of providing operator 

protection in seams 48 in or less. This 

technique provides protection from the 

most frequent injuries while maintaining 

adequate operator visibility and 

comfort. 

TECHNICAL APPROACH 

The limited success of current design 

methods in producing acceptable operator 

compartments for thin-seam, high-speed 

face equipment required that new design 

approaches be taken. The initial problem 

was to determine the most frequent types 

3~nderlined numbers in parentheses refer to items in the list of references 

preceding the appendix. 

and causes of high-speed, low-coal face 

equipment accidents. Afterwards, the 

goal was to determine the most effective 

means of either preventing the accidents 

or protecting the operator without creating additional hazards. 

Accident analysis (table 1) indicated 

that, for high-speed face equipment, the 

majority of accidents (87 pct) were 

pinching and/or squeezing. These are 
TABLE 1. - High-speed low-coal shuttle car accidents, 1982-84 

accidents where the operator becomes of design factors which must be considcrushed between the machine frame and ered in low coal canopy designs have been 

overhead obstructions or the rib. The defined. These design considerations, 

major causes of this type of accident which are listed below, have been inwere lack of operator visibility and lack corporated into this program: 

Other 

~0.17 11 

13 4 

1984.. .... Total.. 

of adequate protection. 

Based on this data, it was concluded PA--p Overall Safetythat a significant number of low-coal, 

high-speed face equipment accidents could Safety must remain the keystone cribe prevented with alternatives to full- teria of good compartment design. This 

coverage canopies. (However full- involves operator protection from as many 

coverage canopies are the most preferable conceivable injuries as possible, from 

means of protection where they are prac- life-threatening injuries due to roof 

Year 

1982...... 

1983.. .... 

tical.) In low coal, full coverage can falls to bruises and contusions caused by 

restrict physical movement and visibility sharp corners within the cab. Safety 

to such an extent that safe machine oper- also involves providing a comfortable 

Roof fall 

275 

870 

ation becomes difficult. Therefore, lim- physical and psychological environment to 

ited coverage was determined to be a promote safe work habits. 

viable option in cases where no operator 

Total 

334 

261 

No. 

34 

19 

protection was available. Adequacy of Operator Vision -- and ---- Vision 

This report is aimed at preventing in- Windows 

jury due to the most common type of lowcoal, high-speed face equipment accident, Restricted visibility is the operator's 

Pct 

10 

7 

235 

753 

pinching and/or squeezing. In order to major objection to canopies. Owing to 

achieve this, operator coverage must be either their width or location in the 

Pinching and/or squeezing 

- 87 2 

kept to a minimum to provide adequate compartment, canopy posts often obstruct 

visibility and be strategically placed to vital areas from the operator's view. 

provide maximum protection. This The view of the roof is often obstructed 

No. 

289 

229 

requires the operator protection to be 

placed above and in front of the operator's head to prevent trapping the operator between the machine frame and overhead obstructions. Also side restraints 

should be provided to prevent the operator from leaning out of the protective 

envelope and becoming squeezed between 

the moving machine and rib. 

The Bureau of Mines has sponsored several programs to advance the design and 

application of canopies and to demonstrate the new technologies in underground coal mines. These programs have 

made advances in human factors engineering and standardized operator controls 

and seat design. Additionally, a number 

PC t 

87 

89 

by the thickness and shape of the canopy 

top. It is imperative that the machine 

operator be able to see over the top of 

the machine frame to safely operate the 

equipment. The proper canopy-to-machine 

height relationships (3-4) for safe oper- -- 

ation are shown in figure 1. 

Other common causes of vision obstruction include sideboards, tire covers, and 

machine frames that are too high for the 

seam height. Poor visibility is a serious safety hazard. Machine operators are 

less likely to hit overhead obstructions 

or lean out of the protective canopy if 

they can comfortably view the area beyond 

the machine from within the canopy while 

tramming. 
provided within thin-seam compartments. 

As canopy heights are lowered for 50 

thin-seam operation, the operator is 

placed in an increasingly reclined posi- c 45 tion. This requires an increased working .- 

length if comfort is to be maintained. 

The relationship of operator head room to 40 

proper working length (3-4) - - is shown in 2 

figure 2. Additionally, the compartment 35 

width must be adequate for comfortable 

operation and visibility alongside the 

machine. $ 30 

LT 

W 

a 

Seating 0 25 

Most original equipment manufacturer 2 0 

(OEM) low-coal shuttle car seating is inadequate. Proper seating should be padded and equipped with an adjustable back I52o 25 30 35 40 45 50 55 

(with lumbar support) and an adjustable OPERATOR WORKING LENGTH, in 

headrest. Specific requirements are that 

the eye level of a 5th-percentile female FIGURE 2.4perator-head-room-to-compartment-length 

and 95th-percentile male operator be high relationships. Lowest possible headroom. 
Shoulder height 

Eye-to- helmet top 

Forearm - hand length 

Buttock - knee length 

Buttock- leg length 

Back-of -knee height 

Shoulder breadth 

Hip breadth 

Eye height 

Sitting height 

S~tting height 

with helmet 

I Dimenions, in I 

FIGURE 3.-Coal miner anthropometrics. 

5th percentile 

female 

19.7 

' 6.0 

15.3 

20.5 

38.0 

14.8 

14.1 

12.9 

26.9 

30.9 

32.9 

enough to see over the top of the machine 

frame and the seat width be adequate for 

a 95th-percentile male. (See figure 3.) 

95th percentile 

male 

25.7 

6.5 

20.2 

25.9 

46.1 

18.2 

20.1 

15.4 

33.9 

38.4 

40.4 

Com~lexitv of Design 

Based on the results of previous canopy 

projects, it has become apparent that 

overly complex canopy designs have not 

all been successful. Canopies with numerous and complex moving parts and/or extensive hydraulic adjustments are difficult to install and maintain, and their 

novel features are often not used or become damaged to the point where they 

cannot be used. Designs should be kept 

as simple as possible to minimize operational problems. 

Frequency of Maintenance and Ease of --- -- ------- 

Field Retrofit 

Complicated canopy designs that incorporate too many hydraulic adjustment features, too many moving parts, and "gadget 

type" features of ten fall into disrepair 

because the frequent maintenance they 

require is simply not done. Past experience has shown that a simple, structurally sound and human-engineered canopy 

design is the most accepted type of canopy. Canopies should be constructed of 

readily available materials and should 

require minimal machining work. 

Ingress and Egress 

Structural Integrity 

Another major complaint of operators is 

the difficulty of ingress and egress 

caused by canopy design. Openings must 

be free of obstacles that tend to snag 

the operator's belt, cap-lamp battery, or 

self-rescuer. Two important design features can be employed to aid the operator. The first is to use as many handrails and handholds as are feasible to 

facilitate quick and smooth ingress and 

egress. The second feature for design 

consideration involves alternate exits. 

There are situations when the operator 

must exit in a hurry (for example, fire, 

inundation, etc. ). If for any reason the 

main egress route from the machine is 

blocked, there should be an alternative 

way out. This alternative escape opening 

should measure at least 18 by 30 in. 

Each canopy should be designed to withstand a vertical load of 18,000 lb or 

15 psi distributed over the plan view 

area of the canopy roof structure in compliance with 30 CFR 75.1710. A design 

feature which is not an MSHA requirement, 

but should be incorporated, is the ability of the canopy to withstand significant horizontal impacts without deforming 

the canopy top, posts, or the compartment 

support structure. 

With these considerations in mind, a 

list of features that should be included 

in a limited-coverage operator structure 

was compiled. These features are as 

follows: 
1. Floating deck for maximum operaator room. 

2. Wider and longer compartment 

for comfort and visibility. 

3. Padded adjustable seat and 

headrest. 

4. Optimum location of controls 

for easier operation. 

5. Handholds for ingress and 

egress. 

6. Optional emergency exit for ingress or egress. 

7. Reduced canopy size for better 

visibility. 

8. Side protection to prevent 

operator from leaning out. 

9. Lower sideboards for better 

visibility. 

10. Wheel covers removed for better 

visibility. 

11. Optimum location of canopy support posts for better visibility. 

12. Simplicity of design for ease 

of fabrication. 

13. Structural integrity for operator protection. 

DESIGN CONCEPTS 

The initial step in this project was to 

select a typical low-coal shuttle car to 

retrofit with improved operator portective structure concepts. There are two 

general shuttle car designs of the 

straight-through chain conveyor type commonly used in low-coal mining operations. 

Both designs possess unique advantages 

and disadvant qges . The first is a 

center-driven configuration that provides 

the operator with a marginal, but acceptable, field of vision in both tram directions. This configuration poses some 

vision difficulties when tramming outby 

with a full load of coal, particularly 

when the operator tries to align the 

shuttle car with the dumpsite. The second general configuration is the enddriven shuttle car. This configuration 

provides excellent vision when tramming 

outby by eliminating the need to look 

over the coal pile. However, it does 

restrict vision when tramming inby due to 

its position on the far end of the car. 

Since both of these design configurations 

are relatively common, it was decided 

that design concepts should be developed 

for both vehicle types. Two shuttle cars 

were available on-site, a National Mine 

Service (NMS) Torkar 28B-S12-40 centerdriven shuttle car and a FMC 6L-52 enddriven shuttle car. Although neither of 

these cars are typically used in low 

coal, they were determined to be adequate 

4~ef erence to specific products does 

not imply endorsement by the Bureau of 

Mines. 

for demonstrating the overall design 

concepts. 

Three design concepts were chosen to be 

developed into prototype operator protective structures. All three were based on 

the limited-coverage philosophy. These 

concepts eliminated the major drawback of 

current canopy designs by providing adequate visibility. Although these designs 

do not provide the ideal objective of 

providing full-coverage operator protection, they do protect the operator from 

the most frequent cause of shuttle car 

operator injuries (pinching and/or 

squeezing accidents). Thus, the implementation of these designs constitutes a 

vast improvement over the current practice of providing no protection. 

A philosophy of human factors design 

was adapted to the necessary functions of 

the shuttle cars. The restricted environment of low-coal requires special considerations. Absolute comfort for the 

operator is not possible given the limited space compartment. Compromises must 

be made with respect to what is theoretically desirable versus what is possible 

from a practical viewpoint. Thus, the 

human factors challenge was how to best 

meet both the functional requirements and 

at the same time avoid undue physiological or psychological stress on the 

operator. 

The first concept to be developed was a 

roll-bar configuration. This concept had 

the advantage of providing a protective 

envelope which could be quickly and 
easily retrofitted underground between 

working shifts. 

The second concept was a sliding canopy 

which would provide protection over one 

end of the operator compartment at a 

time; it must be slid from one end of the 

cab to the other, depending upon the 

operator's position for the current tram 

direction. While slightly more complex 

to install than the roll-bar design, this 

concept had the advantage of providing 

some roof fall protection in addition to 

protection from pinching and/or squeezing 

type accidents. 

The third concept was a "flip-top" design which featured an arc-shaped canopy 

that could be flipped from one end of 

the operator compartment to the other 

decided that this design should be developed into a total operator compartment 

design concept utilizing the latest in 

anthropometric design criteria. 

Prior to construction, each of the concepts was built in mockup form utilizing 

plywood and plastic pipe. This technique 

had proven extremely useful in previous 

Bureau programs. The plywood mockups 

allowed design deEiciencies to be readily 

identified and corrected prior to actual 

hardware construction. Once the mockups 

were evaluated for operator comfort, visibility, and general overall suitability 

for the selected shuttle cars, the designs were finalized and actual fabrication commenced. A detailed description 

of each canopy design is listed below. 

depending on the tram direction. It was 

LIMITED COVERAGE CONCEPTS 

ROLL-BAR CANOPY The original tram deck was too narrow 

for adequate operator comfort or visibilThe simplest and most obvious solution ity along the side of the shuttle car 

for providing limited-coverage protection 

is a roll-bar type protective structure. 

This type of protection is recommended 

only for the most restrictive environment 

(seam heights less than 42 in), where 

more comprehensive protection cannot be 

provided. This concept can provide protection and maintain reasonable operator 

visibility in all but the lowest coal 

seam applications (less than 32 in) where 

batch-type haulage is commonly applied. 

The base vehicle chosen for design work 

was the National Mine Service Torkar 28BS12-52. This shuttle car was originally 

designed for moderately low-coal operation (40- to 52-in seam heights), but 

still provided a suitable base for concept construction and evaluation. Also, 

the OEM operator compartment came with a 

full-floating tram deck, which precluded 

the need for construction of a new floating mechanism or radical rearrangement of 

the operator controls. 

The initial task was to prepare the 

shuttle car for low-coal operation. 

First, the high wheel covers were removed 

and replaced with belt material to imwithout leaning out of the compartment (a 

major cause of operator injuries (3-4). -- Ideally, the seating width should be at 

least 20 in, and compartments should be 

at least 30 in wide, not including space 

taken up by controls (3-4). The tram -- 

deck of the Torkar was widened by 8 in to 

give the operator a full view along the 

side of the machine and provide 30 in 

side-to-side room for the operator. 

OEM seating consisted of an 8-in-wide 

steel plate that folded up to provide the 

operator with very minimal back support; 

this seating arrangement was removed. A 

new seating system was devised to overcome the limitations imposed by bidirectional equipment compartment design, 

which requires opposing seats at either 

end of the cab that are small enough not 

to interfere with the tram and brake controls. The new design consists of a 

single seat with track-mounted rollers so 

it can be moved from one end to the other 

with minimal effort. This seat (fig. 4) 

contains numerous features for operator 

comfort. They are as follows: 

prove operator visibility over the top of 

the car. 
Adjustable headrest 

Bearing (180" swivel) mountey ,Q- // Sliding base 

FIGURE 4.-Shuttle car seat. 

1. Padded seat, 20 in wide. 

2. Padded backrest with lumbar 

support. 

3. Padded headrest. 

4. Horizontal seat adjustments for 

comfortable control reach. 

5. Vertically adjustable backrest 

for proper seating height. 

6. Adjustable headrest for 

comfort. 

7. Rugged construction to withstand 

the mining environment. 

This totally adjustable seating system 

provided comfort and proper seating 

height for visibility through the entire 

range from 5th percentile female to 95th 

percentile male. 

The next problem was designing and installing the roll bars. The main concern 

is proper placement to provide the maximum operator protection. The main thrust 

of this protection is to prevent pinching 

and/or squeezing accidents. The roll bar 

should therefore be placed in front of, 
y v, p

head. The next consideration is to place 

the roll bar so that the temptation to 

lean out of the cab is inhibited. 

The roll-bar concept was applied to the 

modified Nat.iona1 Mine Service Torkar 

compartment (fig. 5). Two roll bars constructed of 3 in structural steel tubing 

were placed at the quarter points in from 

each end of the 76-in-long compartment. 

The resulting structure was capable of 

supporting vertical loads of at least 

,g 

4,000 lb. 

The complete package of roll bars, 

wider compartment, full floating deck, 

and improved seating meets most of the 

ideal design criteria. This type of operator protection can be easily implemented on face equipment, providing some 

protection in mining environments where 

no other protective measures exist and 

where conditions preclude the implementation of more complete protection. 
;Complete specifications for the shuttle 

car with roll-bar protection are given in 

bable 2. 

TABLE 2. -Specifications for shuttle 

car, roll-bar canopy, and sliding 

compartment 

Shuttle car: 

Unit weight .......... lb.. 26,000 

Overall length ....... ft.. 26 

Frame height.. ...... .in.. 32 

Working height.. .... .in. . 40 

Width................in.. 109 

Conveyor width.......in.. 5 5 

Conveyor speed ... ft/min.. 60 

Capacity 

(water level)....cu ft.. 130 

Tram speed.. ....... .mph.. 4.0 

Tire size................ 12 by 20 

Ground clearance. ... .in. . 6.5 

Wheel base...........ft.. 9 

Boom extension.. .... .in.. 40 

Turning radius: 

Inside.............ft.. 7-516 

Outside............ft.. 22 

Motor: Hydraulic .... hp.. 45 

Roll-bar canopy, in: 

Height (with cab)........ 36 

Width.................... 32 

Length.. ................. 7 6 

Post thickness........... 3 

Seat width............... 20 

Sliding canopy, in: 

Height (with cab)........ 38 

Width.................... 32 

Length. .................. 76 

Canopy coverage.. ........ 37.5 by 37.5 

Post thickness........... 3 

Seat width............... 20 

1 SLIDING CANOPY 

The second concept constructed was a 

sliding canopy design (fig. 6). This 

system provides the operator with significant roof fall protection in addition to 

protection from pinching and/or squeezing 

accidents. For the shuttle car used, 

this design is acceptable for coal seams 

heights as low as 40 in. Depending on 

the shuttle car's frame height, suitable 

operator protection is obtainable in even 

lower coal seams, minimizing the most 

frequent high speed face equipment 

operator injuries (the pinching and/or 

squeezing accident) and providing ample 

ingress and egress points. 

The sliding canopy provides protection 

over the half of the cab where the operator is sitting and an unrestricted field 

of vision in the opposite direction. The 

canopy position is repositioned manually, 

with minimal operator effort, and is 

automatically locked in position. 

This concept was also constructed on 

the improved Torkar base vehicle. The 

canopy was constructed of a 37.5-insquare, 314-in plate with rounded corners 

to minimize hang-ups in the event of 

roofing. The canopy is supported on 

3-in o-posts mounted on 3-in cam followers which slide in two 314-in-thick 

C-channels and are locked in place by 

spring-loaded latches. 

Again, support posts were located to 

provide the maximum protection and visibility. The outside post was located at 

the quarter point to prevent the operator 

from leaning out; the inside posts were 

located at mid point to provide a clear 

line-of-sight to the conveyor. Handholds 

were provided for easy ingress and egress 

and to assist in sliding the canopy from 

one half of the compartment to the other. 

The canopy vertical load capacity far 

exceeded MSHA's minimum requirement of 

18,000 lb distributed over the plan view 

area. The horizontal load capacity was 

calculated to be 4,000 lb. The design 

also provides alternative egress routes. 

The sliding canopy provides protection 

from pinching and/or squeezing accidents 

and partial protection from roof falls. 

Specifications for the sliding canopy are 

given in table 2. 

FLIP-TOP-CANOPY OPEEMTOR COMPARTMENT 1 

The most recent design was the flip-top 

canopy integrated into a totally anthropometrically designed operator compartment 

(fig. 7). This concept is somewhat more 

complex than the preceding concepts, requiring that the retrofit be made either 

in a rebuild shop or during initial construction at the manufacturer's plant. 

Although it is more complex, this design 

is considered to be beneficial in terms 

of increased protection and overall 
FIGURE 7.-Flip-top operator compartment. 

pp

environment. 

The total design concept is applicable 

to even lower case designs. It was designed for and mounted to an available 

FMC 6L-52 end-drivenshuttle car. An 

end-driven shuttle car was selected because the flip-top concept provides the 

maximum possible visibility when tramming 

inby. End-driven shuttle cars have inherently poor visibility inby due to the 

position of the operator's compartment at 

the far end of the shuttle car and thus 

very little interference with the operator's vision can be tolerated. 

The final design resulted in an operator compartment that was 59 in long, 39 

in wide, and 44 in high. The canopy top 

and side frames form a quarter circle 

with 25-in radial support arms pinned at 

the center. The top is rotated (flipped) 

from end to end (depending on the 
1 I:, 

FIGURE 8.-Flip-top compartment in raised position. 
brake whenever the pressure bleeds off 

below a predetermined threshold value. 

All of the shuttle car controls are 

strategically placed within the operator's reach envelope. Activation of the 

foot controls is consistent so that confusion is avoided when changing tram direction (right foot always operates tram 

pedal and left foot always operates 

brake). Additional features of the fliptop-canopy design are as follows: 

or lowered by tightening or loosening the 

sling. 

6. The canopy is a unique flip-top design that provides protection from pinching and/or squeezing accidents and some 

roof fall protection while leaving the 

operator's field of vision completely 

unobstructed; it is flipped 90' to the 

other side of the compartment by a rotary 

actuator to provide protection when tramming in the opposite direction. The 
flip-top actuator control is placed in a 

protective box outside of the operator 

compartment to prevent accidental activation. of the canopy with the operator 

inside the cab. and yet. is conveniently 

located for easy access . The flip-top 

canopy is a quarter-circular design with 

a 25-in radius. constructed of 2.5-in-OD, 

high-strength structural steel tubing and 

covered with 0.75-in steel plate . The 

canopy unit is supported and rotated by a 

1.5-in 90-kip/in2 tool-steel shaft . 7 . All control improvements are easily 

integrated into the stock hydraulic system with some system modifications (fig . 10) . All added controls are of flowthrough center construction and placed in 

series with the existing controls . Specifications for the flip-top canopy and 

shuttle car are given in table 3 . TABLE 3 . . Specifications for shuttle car and the flip-top 

canopy operator compartment 

Shuttle car: 

Unit weight ...................................... lb.. 22. 000 

Overall length ................................... ft.. 24 

Frame height .................................. ...in.. 35 

Working height ................................... in.. 48 

Width ............................................ in.. 107 

Conveyor width ................................... in.. 55 

Conveyor speed ............................... ft/mn .. 64 

Capacity (water level)........................^^ ft .. 160 

Tram speed ...................................... mph.. 4.2 

Tire size ............................................ 10 by 15 

Ground clearance ................................ .in.. 7.5 

Wheel base ..................................... ..ft.. 8-1 /6 

Boom extension ................................. ..in.. 41 

Turning radius: 

Inside .................................. .......f to 9-1/12 

Outside ................................. .......ft.. 21-5/12 

Motors. 250-V dc: 

Traction (2) ................................... hp .. 15 

Conveyor .................................... ...hp.. 15 

Flip-top canopy operator compartment: 

Height .......................................... .in.. 44 

Width...................... ........ in^^ 39 

Lengthin^^ in.. 59 

Canopy coverage ................................ in 25 by 34 

Flip-top flip speed ............................. sec.. 3.5 

Seat width ....................................... in.. 20 

Floating bottom point ............................ in.. 0-10 
I 1.600 psi 

1;600 ps i 

Rotory actuator 

1,000 psi 

'%o psi 

Steering rams -fi&l valve !!@ Boom rams 

Cable ree +Tpr ; 650 psi 1 1 

moter 

- -7 Park brake 

Sequence I I valve j 

valve 

I rams 

Oil 

cooler 

FIGURE 10.-Schematic of modified hydraulic system. 

- 

TESTING 

Park brake 

All of the canopy concepts were verified to insure that they were in compliance with the MSHA requirements set 

forth in 30 CFR 75.1710, which requires canopies to withstand a vertical 

load of 18,000 lb, or 15 psi distributed 

over the plan view area of the canopy. 

The roll bar and the sliding canopy were 

verified mathematically utilizing computer software packages. The roll bar 

was analyzed using Structural Software 

System's FATPAK. The sliding canopy was 

analyzed using the University of 

California-Berkley's SAP IV program. Due 

to its structural complexity, the fliptop canopy was physically tested using 

established MSHA guidelines (7). 

The three new canopy concep~s, as well 

as the OEM canopies and tram deck with no 

canopy, were also tested using the 

Bureau-developed Human Eye Reference 

Measurement Instrument (HERMI) (6). This 

testing established a quantitative measurement of operator visibility for each 

of the canopy types. 
tem is developed to indicate the priority 

of each of the visual attention locations 

(table 4), where 3 = most significant, 

2 = significant, and 1 = least significant. Next, a weighting system is applied to the HERMI (fig. 11 where 

3 = location can be seen without flexion, 

2 = location can be seen with neck flexion, 1 = location can be seen with neck 

and trunk flexion, and 0 = location cannot be seen. 

The visibility score can be computed as 

follows: 

Front edge 

Rear edge I ---------I ------ 

Note: 

Numbers shown are used 

for reference in table 4. 0 - 10 

Scale. ft 

FIGURE 12.-Visual attention locations for shuttle car. 
TABLE 4 . . Visual attention locations priority scores for shuttle car 

point 1 Up-down location I priority2 11 Point 1 Up-down location 

~i~hest machine point .. Operator eye height .... Highest machine point .. 

No . 1 

1 .... 

Operator eye height .... Floor .................. Highest machine point .. Floor .................. Median machine height .. Operator eye height .... Highest machine point .. Median machine point ... Operator eye height .... Highest machine point .. Seam height ............ Floor .................. Median machine height .. Highest machine point .. Floor .................. Median machine height .. Operator eye height .... Highest machine point .. Floor .................. 

Operator eye height .... 

where V = Visibility score. 

2 

24 ... 25 ... 26 ... 27 ... 

P = Priority weight for visual 

attention locations. 

U = 95th percentile (upper arc) 

points. 

No . ' 

28 ... 

'see figure 12 . 23 - most significant. 2 - significant. 1 - least 

Operator eye height .... Highest machine point .. Floor .................. Highest machine point .. 

and L = 5th percentile (lower arc) 

points. 

Median machine height .. Seam height ............ Floor .................. Seam height ............ 

3 

3 

3 

3 

Floor .................. Median machine height .. Highest machine point .. Floor .................. Highest machine point .. Floor .................. Operator eye height .... Highest machine paint .. Floor .................. 

51 ... 52 

53 ... 54 ... 

Operator eye height .... Highest machine point .. Median machine height .. Highest machine point .. Floor .................. Median machine height .. Operator eye height .... Highest machine point .. Floor .................. Operator eye height .... Highest machine point .. Floor .................. Highest machine point .. 

significant . 

qualitatively evaluated at the Bureau's 

mining equipment test facility (METF) in 

order to obtain operators' reactions to 

the new concepts . A part of the METF 

features simulated mine workings. complete with an adjustable roof height . Several shuttle car operators were asked 

to maneuver the shuttle cars equipped 

with the limited-coverage canopies 

through the entries and to give their reactions to each of the three concepts . Once the initial testing was completed. 

the limi ted-coverage compartments were 
SUMMARY OF TEST RESULTS 

All three of the compartment designs 1.834 kips 

easily met MSHA load-capacity require- 2 6 "--I 

ments. The roll-bar canopy was evalu- 8.655kips6r 8.655 kips 16.22 kips/in ated using a moment distribution tech- ?%l.46 kipsAn 1.834 kips 

nique with applied loads of 18,000 lb 

vertical and 4,000 lb horizontal (fig. 

13). Analysis indicated that the canopy 

was well below yield at these loadings 

(figs. 14-1 5). The sliding canopy analysis was a somewhat more complex plate and 

shell canopy that required a finiteelement analysis (fig. 16). This canopy 

was subjected to the same 18,000 lb vertical and 4,000 lb horizontal loadings, 

and it also never exceeded its elastic 

limit at these loadings. 

Loads 

KEY 

V- Shear 

M -Moment " '17 Fa-Allowable axial load 

-1.834 kip Fb-Allowable bending load 

fa - Axial load 

f b -Bending load 

FIGURE 14.-Structural analysis of roll-bar member 1. 

-3 5.834 kips 

31.46 tt32'4 kips/in 4276klps/in 

8.655 kips 9.361 kips 

Material: 3 -in P schedule 80 pipe; 

A =3.02in2 

I =3.89in4 

s = 2. 23in3 -9.361 kip 

15.38" 16.62" 

KEY 

FIGURE 13.-Roll-bar loadings. FIGURE 15.-Structural analysis of roll-bar member 2. 

35.06 kips/in V- Shear Global M- Moment 

Y Fa- Allowable axial load 

Fb-Al lowable 

2 T (0.26) ( 32.26) fa- Axial load 

fy-Bending load 

MEM GEM^ 

Coordinates 

/m4 -31.46 kip/in 

(32.20) -42.76 klp/in 

2 fa= 5'834 1,931 kips/in ' fb=422y37$"n = 19.17 kips/in 2 

MEM I 3.02 in Fa = 20.16 kips/in I at Fy 36 kips/in Fb= 24 kips/in 

Im (0.0)~ 1.931 19.17 

Global X 20.16 + 24 =0.095+0.79 =0.88 1 I 
VlEW 

39; I1 

7% 7 I,; 9; 3% 

I dt= 3p I \A, 

'7 37 'L211 'I, 

SIDE VlEW 

KEY 

Global ordinate 

Global ordinate 

Global ordinate 

FIGURE 16.-Finiteelement grid used for analysls of slldlng canopy. 
Due to the complexity of the flip-top 

canopy, it was decided to perform physical testing rather than mathematical 

analysis. The standard MSHA procedure 

(5) was used; the canopy was loaded to 

11,745 lb distributed over the middle 

third of the canopy (15 psi distributed 

over the plan view area), and deflections 

were recorded using a dial gauge indicator. A total of 10 pct residual deflection in the canopy is permitted after 

the load is removed. The flip-top canopy 

showed 0.163 in deflection at full load 

with 0 in residual deflection, indicating 

it is well within the structural integrity limits set by MSHA. 

Limited-coverage designs improved visibility and operator comfort through compartment modification, improved seating, 

and implementation of an alternative 

means of operator protection in low coal 

where conventional full-coverage canopies 

are usually removed or not implemented. 

Operator visibility was quantitatively 

measured using the Bureau-developed 

(HERMI. ) 

Visibility measurements were taken at 

54 previously established points where 

operators must have adequate visibility 

for safe operation of their equipment. 

These readings were added together to 

produce visual attention location scores 

(tables 5). 

The designs were evaluated on the basis 

of 898 possible points, which represents 

the ideal visibility score. As expected, 

the compartment with no canopy ranked 

highest, with 700 points, or 78 pct of 

the ideal score. This configuration is 

probably the most commonly used in lowcoal mines, but could hardly be recommended since it provides the operator 

with no protection. 

TABLE 5. - Visual attention location 

score 

The flip-top-canopy operator compartment tied for second, with 665 points, or 

74 pct of the ideal score. This configuration is the most comprehensive 

operator-oriented compartment, providing 

good visibility, good pinching and/or 

squeezing protection, and some roof fall 

protection. Since it is a cab-and-canopy 

compartment concept, its complexity precludes inlnine installation, and it would 

best be installed by the manufacturer or 

in a rebuild shop. Of all the concepts 

considered, the flip-top-canopy design 

should afford the greatest improvement in 

safety because of the overall improvement 

in the operator's environment. 

The sliding canopy tied for second with 

665 points, or 74 pct of the ideal score. 

This configuration provides reasonably 

good visibility, good pinching and/or 

squeezing protection, and some roof fall 

protection. Overall, it is a good limited-coverage design for in-mine installations and provides an immediate solution 

to the problem of operator protection. 

The sliding canopy is limited by the 

machine frame height and OEM compartment 

design; some compartment modification is 

required. Additionally, it is slightly 

more complex than the roll-bar design, 

thus requiring more maintenance. 

The roll-bar con£ iguration ranked 

third, with 615 points, or 68 pct of the 

ideal score. This was still a respectable rating. The lower rating is due to 

the necessity of placing one roll bar in 

front of the operator's field of vision. 

The main advantage of this system is that 

it is quite simple. It provides good 

protection from pinching and/or squeezing 

accidents and can be adapted to almost 

any machine underground between shifts. 

The lowest ranking configurations were 

the OEM full-coverage canopies, with 531 

points or 59 pct of ideal, and, 543 

points or 60 pct of ideal. These configurations do provide good overhead roof 

fall protection, but their limited visibility may encourage operators to lean 

out of the canopy, making the operators 

vulnerable to pinching and/or squeezing 

accidents. This is the reason why variances are generally granted by MSHA to 

permit the removal of canopies. 

Score pct 

of ideal 

78 

74 

74 

68 

60 

59 

No canopy.. . . . . Flip-top canopy 

Sliding canopy. 

Roll bar.. . . . . . FMC OEM canopy. 

NMS OEM canopy. 

Points 

(898 = ideal) 

700 

665 

665 

615 

543 

53 1 
In the qualitative evaluation at the visibility afforded by the new designs 

Bureau's test facilities, at least three and especially liked the comfort of the 

operators were asked to maneuver shuttle padded seats as opposed to the standard 

cars equipped with each of the limited- steel plate commonly used for shuttle car 

coverage canopies through the mine en- seating. The Bureau plans to conduct an 

tries. The shuttle car operators were extensive in-mine evaluation of the flipquite satisfied with the improvements in top-canopy design with a mine operator. 

CONCLUSIONS 

Limited-coverage canopies can provide 6. Operator exits have minimal obpartial operator protection for miners structions, affording quick exit if 

working in situations where conventional necessary. 

f ull-coverage canopies cannot be employed. The basic advantages of these 

systems are as follows: 

1. Protection from the most frequent 

type of shuttle car operator injuries 

(those caused by pinching and/or squeezing accidents), which account for 87 pct 

if all low-coal shuttle car accidents. 

2. Greater visibility, roof and working areas, compared to full-coverage 

canopies, resulting in safer operation. 

3. Canopies are designed to withstand 

lateral loads and provide a safer "shell" 

for the operator. 

4. For the roll-bar and sliding canopies, installation can be performed 

underground. 

5. The designs are simple and adaptable to a variety of equipment. 

7. Operator comfort is increased, 

thereby reducing fatigue. 

8. The overall improvement in operator 

space and human factors-engineered on a 

human-factors basis engineered control 

layouts provides an improved psychological environment for operators and therefore promotes safer working conditions. 

It is recommended that the designs developed during the course of this project 

be used on shuttle cars such as those 

described and on shuttle cars with lower 

frames. These designs could also be 

adapted to other types of high-speed mobile face equipment, such as scoops and 

tractors, to provide canopy technology 

that would improve the safety and efficiency of mine equipment operators. 

REFERENCES 

1. Aljoe, W. W., and K. L. Whitehead. 

Advancement of Cab and Canopy Design and 

Use in Coal Mines (contract 50199005, 

BCR), BuMines OFR 109-85, 1981, 306 pp.; 

NTIS PB 86-153574. 

2. Billmayer, H. Extension of Low 

Coal Canopy Technology To Include Drilling and Cutting Machines (contract 

H0318007, Wyle Labs). BuMines OFR 132- 

84, 1983, 56 pp.; NTIS PB 84-215052. 

3. Lineberry, G. To, and L. Adler. 

Velocity Clearance and Curves for Mobile 

Mining Equipment. Min. Eng. (Littleton, 

Co.), v. 36, No, 8, 1984, pp. 1196-1200. 

4. Sanders, M. S. Visual Attention 

Locat ions for Operating Continuous 

Miners, Shuttle Cars, and Scoops: A 

Summary (contract 50387213, Canyon Res. 

Group, Inc. ). BuMines OFR 29(2)-82, 

1981, 67 pp.; NTIS PB 82-187949. 

5. Sawyer, S. G., and D. K. Brogran. 

A Testing Procedure for Certification of 

Underground Protective Cabs and Canopies. 

MSHA (U.S. Dep. Labor) IR 1002, 1974, 

15 PP* 

6. Sawyer, S. G. , and J. A. McCormick. 

Cabs and Canopies Underground to Protect 

Miners. Coal Min. & Process., v. 10, No, 

2, Feb. 1975, pp. 40-44. 

7. Zona, A. ((MSHA) U.S. Dep. Labor). 

Private communications, Jan. 1986; available upon request from 5. R. Bartels, 

BuMines, Pittsburgh, PA. 
APPENDIX.--SYMBOLS USED IN THIS REPORT 

area 

depth 

axial stress 

bending stress 

allowable axial stress 

allowable bending stress 

moment of inertia 

outside dimension 

radius 

section modulus 

thickness 

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