Armtrac 75 Assessment Phase 1 - GICHD

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Copyright © QinetiQ ltd 2004 Unclassified

This document is supplied by QinetiQ for DFID under Contract No. CNTR012395

Armtrac 75 Assessment Phase 1

Peter Blatchford & Chris Leach QINETIQ/FST/TRD042153 April 2004

Requests for wider use or release must be sought from: Intellectual Property Division QinetiQ Ltd Cody Technology Park Farnborough Hampshire GU14 0LX

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QINETIQ/FST/TRD042153 Page 2 Unclassified

Administration page Customer Information

Customer reference number

Project title Armtrac 75 Evaluation

Customer Organisation DFID

Customer contact Mr A Willson

Contract number CNTR012395

Principal author

Peter Blatchford Phone number : 01252 374192

Cody Technology Park

Rm S4, Bldg 412

Pyestock

Ively Road, Farnborough

Hants. GU14 0LX

[email protected]

Chris Leach Phone number : 01252 374005

Cody Technology Park

Rm S17, Bldg 412

Pyestock

Ively Road, Farnborough

Hants. GU14 0LX

[email protected]

Release Authority

Name John Hambly

Post Technical Manager

Date of issue April 2004

Record of changes

Issue Date Detail of Changes

1.0 March 2004 First Issue

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Executive Summary This report details the results of an assessment of the Armtrac 75 mine clearing flail. The trial was designed to be the first phase of a 3-phase assessment process, evaluating handling and mobility characteristics and general performance capabilities. Phase 2 will provide a more thorough assessment of its mine clearance ability against a large number of representative targets under a range of controlled conditions, plus vehicle and operator survivability tests; phase 3 will involve field testing over several months to provide productivity and running cost information.

The tests conducted demonstrated that the machine has the ability to clear both mines and vegetation, albeit with limitations. They highlighted a number of important characteristics of the machine, both positive and negative :

Positive • The extending arm provides excellent reach and articulation, particularly useful

for clearing banks and ditches • The extending arm also facilitates self-recovery when bogged down • A number of different tools can be easily fitted in place of the flail, providing

good versatility • It is compact and easily transportable • Highly manoeuvrable due to 4-wheel steering

Negative • The minimum forward speed is too high for effective flailing • Difficulty was experienced in making fine adjustments to the speed and in

accurately adjusting the flail height to follow ground undulations • Control of speed, direction and flail height were particularly difficult under

remote control • The machine gets bogged down in soft ground very easily • There is insufficient torque at the wheels for good hill climbing ability

It was recommended that the minimum speed be reduced by a factor of at least 4 before the machine should be considered for proceeding to phase 2 of the assessment process, which will be repeatable mine clearance performance testing under more controlled conditions.

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List of contents 1 Introduction 6

1.1 Background 6 1.2 Aim 6 1.3 Scope 6 1.4 Trial Objectives 6 1.5 Authority 6 1.6 Support Request 6

2 Equipment under test 7

3 Trials methodology 9 3.1 Location and personnel 9 3.2 Trial rationale 9 3.3 Records 9

4 Test Procedure 10

5 Results 11 5.1 Weights and Dimensions 11 5.1.1 General Dimensions 11 5.1.2 Weights 13 5.1.3 Tilt test 14 5.2 Handling and Mobility 16 5.2.1 Turning Circle 16 5.2.2 Straight Line Speed and Braking 18 5.2.3 Slopes and Gradients 18 5.2.4 Cresting Ramp 18 5.2.5 Obstacles 19 5.2.6 Rough Terrain 20 5.3 Field of vision 21 5.4 Remote Control 24 5.4.1 Failsafe 24 5.4.2 Controlled Shutdown 24 5.4.3 Range 24 5.4.4 Operational control 24 5.5 Ground Flailing 24 5.5.1 Speed versus depth 24 5.5.2 Terrain following 27 5.5.3 Slope and ditch clearance 30 5.6 Vegetation clearance 36 5.7 Logistics 37 5.8 Multi-tool versatility 38

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6 Conclusions 39

7 Recommendations 41

8 References 42

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1 Introduction

1.1 Background This UK based trial is phase 1 of a three-phase trial to fully test the Armtrac 75. The UK trial concentrated on the mobility and aspects of performance. Subject to the preliminary results of the UK trial the Armtrac 75 will be shipped to Sweden for further performance testing and also survivability testing. Finally the Armtrac 75 will be subjected to reliability and user acceptance testing in a mine affected country (planned to be Cambodia).

1.2 Aim The aim of the trial was to evaluate the performance and mobility of the Armtrac 75 under defined threat and terrain conditions.

1.3 Scope The tests included an assessment of mobility to, in and from the minefield area. The equipment was also evaluated on its ability to flail the ground consistently, to clear representative surrogate anti-personnel (AP) mines and to clear vegetation. The operational running and maintenance costs were assessed as best as possible within this limited trial.

1.4 Trial Objectives The objectives of the trial were:

• To assess the mobility of the Armtrac 75 using the vehicle testing facilities. • To make a “rule of thumb” assessment of the performance of the equipment

under prescribed conditions and to estimate clearance rates of both mined and vegetated areas.

• To make an estimate of the running costs and logistical support required for the equipment during operations, from available information.

1.5 Authority QinetiQ have been tasked to carry out the trials by the Department For International Development (DFID).

1.6 Support Request Armtrac Ltd were requested by DFID to supply the machine for test. The support required included operation, maintenance and spares throughout the trial and delivery to site.

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2 Equipment under test Armtrac 75 has been developed by Armtrac Ltd. The system has been designed to clear anti-personnel (AP) mines as well as smaller sized Unexploded Ordnance (UXO). The system consists of a commercial telehandler (JCB 520) unit fitted with protective armour, with a hydraulically powered flail unit attached to the telescopic arm, and uprated with a Deutz diesel engine. The flail unit is easily detachable, and a variety of other equipment including a milling device can be used in its place. The machine can be operated from within the armoured cab or by remote control.

Figure 2-1 Armtrac 75 (with arm fully extended)

The general specifications of the machine, as provided in the manufacturer’s literature are as follows :

ENGINE • Latest technology and advanced design provide low fuel consumption, reduced

noise, high torque & power output, total reliability & minimal maintenance • Two stage, dry type air filter with primary and safety elements including forced

suction. • Engine confirms to EC mobile off highway emissions Tier 3. • 4 cylinder charge cooled direct injection, with programmable engine

management with data log. • Engine protection for oil, coolant temp etc. Hydraulic fluid protection for level

& temp. • Power rating: Gross SAE J1995 kW(hp) 126 (168).


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CAB • 10mm fully armoured 7.6 ballistic point blank enclosure. 45mm laminate glass

7.6 ballistic point blank x3. • Full harness suspended bucket seat. • Full climate control • Full Murphy in-cab machine monitoring system.

TRANSMISSION • Full single lever electro-hydraulic proportional drive. • Front & rear epicyclic hub reduction axles with limited slip differentials and a

mid mounted drop box. [NB the vehicle under test did not appear to be fitted with limited slip differentials]

• Rear axle oscillation. • Single hydraulically operated service brake. Manually operated parking brake. • 3 mode 4WS & permanent 4WD. • Solid low ground pressure tyres. [NB the vehicle under test was fitted with

normal pneumatic tyres rather than solid]

CHASSIS • Fully welded monoque frame. • Full 6mm under body armour skid and blast plates. Full 6mm axle armour

skid/blast plates.

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3 Trials methodology

3.1 Location and personnel

The trial took place between 23rd and 27th February 2004 at the QinetiQ Hurn test site. Personnel involved were as follows:

Chris Leach (QinetiQ FST) - Trials Officer

Peter Blatchford (QinetiQ FST) - Assistant Trials Officer

Chris Smith (QinetiQ CMS) - Facility staff

Howard Noyce (QinetiQ CMS) - Facility staff

Paul Jesty (Armtrac) - Operator/technician

Steve Brown (Armtrac) - Owner/Manufacturer

Bob Gravett (for Mines Advisory Group) - Demining advisor

3.2 Trial rationale

The rationale behind the trial was to provide an assessment of the mobility, functionality and general performance capabilities of the machine. This was not intended to be an exhaustive test providing comprehensive mine clearance data, but rather a qualitative assessment of the machine’s limitations and capabilities to give an indication of its suitability for operating in a field environment.

It is being considered as phase 1 of a 3 phase test regime, as follows:

Phase 1 – mobility, functionality and general performance

Phase 2 – thorough mine clearance testing, under controlled conditions against a statistically significant number of targets, plus vehicle and operator survivability tests

Phase 3 – field testing over a period of several months, to provide realistic productivity and running cost information.

These 3 phases of testing are aligned to the recommendations under development in CEN WS12, which aims to provide agreed international standards for the testing of mine clearance machines. The intention is to conduct phase 2 of the tests at SWEDEC (Swedish EOD and Demining Centre) in Sweden and phase 3 in Cambodia in conjunction with MAG (Mines Advisory Group). This will ensure best possible use is made of the facilities available in each location, and that the machine is not put forward to the next phase of testing until it has been confirmed that it is ready and suitable.

3.3 Records

A trials plan [1], safety plan [2] and environmental impact assessment [3] were prepared in advance of the trial. All trial activities were recorded on video and still photographs. Results of each test were recorded on trial performance sheets which have been retained by QinetiQ and are available on request. A separate report on the trial was produced by Bob Gravett for MAG [4].

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4 Test Procedure Test procedure sheets were issued for each test, a summary of the tests is shown in Table 1 below. A description, summary of results and comments/observations of each test are detailed on the following pages.

Test Description Category

A1 Weights & Dimensions Mobility

A1a General Dimensions Mobility

A1b Axle Weights Mobility

A1c Stability/Tilt Test Mobility

A2 Handling & Mobility Mobility

A2a Turning Circle Mobility

A2b Straight Line Speed & Braking Mobility

A2c Slopes & Gradients Mobility

A2d Obstacles Mobility

A2e Rough Terrain Mobility

A3 Field of Vision Mobility

A4 Remote Control Mobility

A4a Failsafe Mobility

A4b Controlled Shutdown Mobility

A4c Range Mobility

A4d Operational Control Mobility/performance

A5 Ground Flailing Performance

A5a Speed versus Depth Performance

A5b Terrain following Performance

A5c Slope & Ditch Clearance Performance

A6 Vegetation Clearance Performance

A7 Logistics Logistics

Table 4-1 List of planned tests

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5 Results

5.1 Weights and Dimensions

5.1.1 General Dimensions

The following measurements were taken using a tape measure and a straight edge:

Measurement Length/Angle

Height 2.14m

Overall length (arm retracted and extended) 5.30-6.82m

Wheelbase (Length between front & rear axles) 1.89m

Width between the external faces of the wheels 1.77m

Width of flail header 2.68m

Width of cut made by flail 1.90m

Ground clearance under belly of tractor 0.29m

Approach angle 90° *

Departure angle 47°

(* The approach angle is effectively 90° since with the tele-arm raised, the front wheels are the first part of the vehicle to hit an obstacle)

Table 5-1 Armtrac 75 general dimensions


Plan View

Front ViewSide View

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Figure 5-1 Dimensions of Armtrac 75

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5.1.2 Weights

The Armtrac 100 was driven onto the QinetiQ Hurn 50 tonne weighbridge. The gross vehicle weight was measured, then front and rear axle weights and individual wheelstation weights. All measurements were made with the driver in his seat, and were repeated with the flail unit in the travelling position, with the arm fully extended and with the flail removed.

The following results were obtained. All measurements are in kilograms.

Travelling position Arm fully extended Without flail

Gross vehicle weight 7510 7510 6270

Front axle weight 4370 5500 2020

Rear axle weight 3140 2010 4250

Left side weight 3660 3660 3050

Right side weight 3820 3810 3240

Table 5-2 Armtrac 75 weights

Figure 5-2 Armtrac 75 on the weighbridge


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5.1.3 Tilt test

The Armtrac 75 was driven onto the QinetiQ Hurn 60 tonne tilt platform and secured with chains. Restraining blocks (75mm tall) were used to prevent the wheels sliding down the platform when tilted. A body roll clinometer was attached to the rear of the vehicle body to measure any difference between the table inclination and body inclination (i.e. body roll). The angle at which the first wheel lifted was recorded.

The worst case orientations of the vehicle were selected with the flail unit in both travelling and flailing positions. Hence the following tilts were conducted :

• Right tilt (as the right hand side is heaviest) in both travelling and flailing positions

• Forwards tilt (nose down) in travelling position • Backwards tilt (nose up) in travelling position • Nose down with the tele-arm fully extended and horizontal (i.e. most front-

heavy).

The following results were obtained, all angles are in degrees :

Travelling position Flailing position

Right tilt Nose down Nose up Arm retracted, right tilt

Arm extended, right tilt

Arm extended (horizontal), nose down

Platform angle 25.1 43.9 48.8 26.6 30.2 23.2

Rear body angle 29.7 - - 31.1 34.1 -

Maximum body roll 4.6 - - 4.5 3.9 -

First wheel to lift Left front Both rears Both fronts Left front Left front Both rears

* Body angle measurements were not taken during the nose up/down tilt test.

Table 5-3 Tilt table results

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Figure 5-3 Nose up tilt test

Figure 5-4 Nose down tilt test


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5.2 Handling and Mobility

5.2.1 Turning Circle

The Armtrac 75 was parked on an area of level tarmac. A container of salt was attached to the front left corner of the flail header, positioned so that salt would pour onto the ground directly beneath the outermost corner of the vehicle as it turned to the right. The vehicle was then driven slowly through 360° to the right using its maximum turning lock (using 4-wheel steer), whilst a second container of salt was held adjacent to the outer edge of the rear left wheel so as to mark a line showing the minimum kerb-to-kerb turning circle, as shown in Figure 5-5 below.

Figure 5-5 Turning circle being measured


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The diameters of the two circles of salt thus produced were measured as follows:

ØA 8.98m

ØB 6.00m

Figure 5-6 Turning circle of Armtrac 75

The ability to ‘crab steer’ was also demonstrated, whereby the front and rear wheels were steered in the same direction. This is potentially useful for operating in confined areas or close to trenches. Where it is required to clear ground close to a trench, care has to be taken when using heavy machines that the side of the trench does not collapse. Crab steering enables a machine to drive along close to the trench in a direction parallel to it, but with the vehicle angled such that it is further from the edge than would otherwise be possible.


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5.2.2 Straight Line Speed and Braking

From a rolling start the machine was timed over a 400m run on a flat and level tarmac surface. It was driven at the maximum safe speed, and at the end of the run it was brought to a halt in the minimum distance possible which was also recorded.

The following results were obtained:

Time for 400m 1m 13s

Maximum speed 5.48m/s = 19.7km/h = 12.3mph

Stopping distance from max speed 2.8m

Table 5-4 Maximum speed and braking results

5.2.3 Slopes and Gradients

The Armtrac 75 was required to drive up various asphalt slopes of known gradient, come to a complete stop halfway up the slope and then continue to the top of slope. The procedure was then repeated for the machine descending the slope, and both ascending and descending in reverse.

The following results were obtained.

Gradient Terrain Result

24.5% (13.8°) Stop & Restart Asphalt Satisfactory up & down slope, forward and

reverse, brakes OK

31% (17.2°) Stop & Restart Asphalt

Ascended about half way, stopped, insufficient torque to continue. Descended satisfactorily forward, brakes OK.

35% (19.3°) Descent Loamy Soil, light vegetation (Off-road) Satisfactory (down only), brakes OK.

Table 5-5 Results of the slope test

5.2.4 Cresting Ramp

The cresting ramps and fixed loading ramps are designed to highlight problems with excessive overhang or restricted underbelly clearance encountered on loading ramps and other scenarios where there is a sharp change in gradient.

The vehicle was driven both up and down the 33% (18.5°) ramp. On the 20%/45% (11.4°/24°) ramp, it was driven up the 20% side but its limited under-belly clearance prevented it from clearing the crest, as can be seen in the figure below.

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Figure 5-7 Armtrac 75 on crest of 20%/45% ramp

5.2.5 Obstacles

The Armtrac 75 was driven over a number of concrete blocks, in various orientations. The blocks were 23cm tall and the vehicle was able to cross them in all orientations attempted, which included one wheel at a time and both wheels on an axle together. The vehicle design allowed sufficient articulation for the blocks to be crossed without lifting any wheels.

Figure 5-8 Crossing concrete blocks


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A 25cm kerb was then crossed and again it was cleared. On one attempt however, the angle of approach was sufficiently acute for a wheel rim to contact the kerb, which bent the rim and deflated the tyre. The wheel was able to be removed by using the tele-arm to lift the front of the vehicle clear of the ground, enabling the rim to be repaired, see Figure 5-9.

Figure 5-9 Front wheel removed

5.2.6 Rough Terrain

The vehicle was driven over various areas of rough, undulating and soft terrain. On a number of occasions it lost traction when trying to cross small rises and rapidly got bogged down as wheels span. In wet soil and soft sand in particular it was very prone to bogging down, see Figure 5-10. However, on every occasion it was able to extract itself without assistance, by lowering the flail onto the ground and using the tele-arm to push the vehicle backwards. Whilst this feature was clearly very useful, it was of some concern how readily the vehicle got bogged down which can be explained by the relatively small wheels with high loading, and by not having the most suitable tyres for off-road use. Differential locks may also prove beneficial in reducing wheel spin.


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Figure 5-10 Bogged down in sand

5.3 Field of vision

The aim of this test was to assess all round driver visibility. The vehicle was positioned on a flat area of ground with concentric circles marked out, centred on the driver’s seat. The view from the driver’s seat was plotted with the flail at working height.

The vision diagram is reproduced in Figure 5-11. In the diagrams white represents clear vision and shaded area represents no vision. It was noted that the cowling on the front of the machine limited vision substantially. However, when the Armtrac 75 was required to travel any great distance the operator opened the doors on the blast plate to improve his forward vision (see Figure 5-12)

The vision to the sides and rear was restricted by the cab structure – however most of these areas could be seen by the driver adjusting position in his seat and by use of the rear view mirrors, see Figures Figure 5-13 and Figure 5-14.


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Figure 5-11 Vision diagram of Armtrac 75 with flail header at working height

Figure 5-12 View through front window in driving mode (flail blast flaps opened)

10m5m 20m 30m

Forward View

Left

Win

dow

Vie

wR

ight Window

View


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Figure 5-13 View through right-hand side window, towards front

Figure 5-14 View through right-hand side window, towards rear


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5.4 Remote Control

5.4.1 Failsafe

Prior to evaluating the performance of the system under remote control, a basic check of its safety was carried out. This was done by putting the vehicle into remote control mode, driving it forwards slowly and then cutting the power from the remote control handset. The vehicle stopped moving after a delay of no more than about 1 second, although the engine kept running. Thus it was felt safe to proceed with further tests as it was demonstrated that all functions would be disabled if communication was lost between the remote controller and the vehicle.

5.4.2 Controlled Shutdown

The next test of the remote control system was to ensure that the vehicle could be brought to a rapid and controlled shutdown. This was satisfactorily demonstrated, with no apparent delay between the operators commands and the vehicle responding.

5.4.3 Range

The vehicle was driven in a straight line away from the operator until there was an indication that the range limit of the system was reached. At a distance of about 220m control started to become erratic; it was suggested that a fresh battery in the remote control handset may extend this range, but this was not checked. It was clear that without any cameras on the vehicle it was very difficult for the operator to control the vehicle usefully from this range anyway due to limited visibility.

5.4.4 Operational control

All the vehicle functions could be controlled from the remote control unit with the same ease as from the cab; however the feedback available to the operator was limited to direct visual observation hence precise operation was not straightforward.

It was noted that maintaining a consistent direction of travel was not always easy as the system had no self-centring of its steering. A function that would return all wheels to the straight forward position would ease this considerably. The flail was also operated under remote control, during part of the performance test as described below in section 5.5.2.

5.5 Ground Flailing

5.5.1 Speed versus depth

A series of 6m long areas of flat ground were marked out for flailing. Each area had two hardboard sheets buried in it, 2.4m long by 0.3m wide, buried on edge flush with the surface, orientated across the direction of travel of the machine. The intention of these tests was to flail each area at a constant depth (around 20cm) and to increase the forward speed of the machine with each test until the hardboard sheets indicated that forward speed was too high and hence obtain maximum forward flailing speed for the machine at that flailing depth.

The boards provided a clear indication of how deep the flail chains were cutting and whether they were achieving consistent cutting across the width of the flail. Previous tests had indicated that if flailing depth is too large, or forward speed too high or flail rotational

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speed too low, uneven flailing will occur and sections of the hardboard strips will remain intact, whereas correct flailing will cut away an even depth of the boards across the entire width.

The first test revealed difficulty in maintaining a constant depth of flailing. The first board was cut away to a depth of about 5-10cm whereas the second board was cut down to about 20cm. However this second board was not cut evenly with large sections having not been touched, indicating that the forward speed had been too high for this depth. The two boards are shown in the figures below, after removal from the ground.

Figure 5-15 Board 1

Figure 5-16 Board 2

The same inconsistency of depth control was observed in the second test, where the first board was barely touched but the second board was cut quite evenly to about 10cm. Four identical tests were carried out in total, it became apparent that it was impossible to drive the machine slowly enough to be able to flail to a depth greater than about 10cm without missing areas of ground. Table 5-6 below shows the time taken for each 6m run and calculated speed. The figures below show the boards.

Run Time for 6m (s) Speed


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Km/h Miles/h

1 25.4 0.85 0.53

2 26.0 0.83 0.52

3 13.6 1.59 0.99

4 14.1 1.53 0.95

Table 5-6 Times and speeds for 6m flailing runs

Figure 5-17 Boards 3 and 4 (from run 2)



The main conclusion from this series of tests is that the minimum speed of the Armtrac 75 is too high for reliable flailing to a depth greater than about 10cm. It is believed that the system has adequate power for flailing down to about 20cm but in order to achieve this its forward speed will need to be reduced significantly. It was observed that for runs 3 and 4 the speed roughly doubled – this indicates the difficulty of controlling the speed as this represented about the smallest increment in speed that could be obtained. Also there appeared to be difficulty in maintaining a constant depth of flailing, with variations of around 10cm being observed within some of the runs, which all took place on quite flat ground.


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Another observation worth recording was that the debris from the flail was generally thrown in a forward trajectory, due to the shape of the cowling to the rear of the flail header. One of the problems with operating flails in dry, dusty environments is that the dirt thrown up can completely obscure the operators visibility. This did not appear to be as bad a problem with the Armtrac 75 as with some machines.

Figure 5-20 Armtrac 75 flailing

5.5.2 Terrain following

The tests described above demonstrated difficulty in maintaining a constant depth of flailing on flat ground. A further test on undulating ground was set up to determine how accurately uneven terrain could be followed.

A 12m long area was marked out, consisting of bumps and dips and a 3.5m long flat area at the end. A hardboard sheet was buried across the bottom of a large dip, and another was buried longitudinally in the flat area. This was intended to give an indication of how consistently the depth of flailing could be maintained in this flat area, as the wheels of the vehicle passed through the preceding bumps and dips.

A number of mechanical reproduction mines (MRMs) were buried as well – these are anti-personnel mine simulants which incorporate a realistic triggering mechanism. The intact mines can be detected with a scanner (similar to a metal detector) and uniquely identified. If they are triggered they can no longer be detected, hence they are a safe and easy way to determine whether the machine has the ability to clear mines.

MRMs were buried at various positions and depths, along with two rows of 6 peat mines – these are simple cylinders formed from compressed peat which when buried can provide another straightforward indication of how deeply and consistently a flail is working. The figures below illustrate the layout of the area.


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Figure 5-21 Uneven terrain test layout

Ridge

Ridge

Ridge

Ridge

Ridge

Dip

1

6

5

4

3

2

18cm peat mines10cm peat mines

10cm

10cm

7cm

10cm

7cm

10cm

Hardboard

= PMN MRM

= PMA2 MRM


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Figure 5-22 Start of uneven terrain test (pre-burial of MRMs and boards)

Figure 5-23 End of uneven terrain test (pre-burial of MRMs and boards)

MRMs 1, 2, 4 and 5 were all untouched, as were all of the peat mines. MRM 3 was struck by the flail and triggered, MRM 6 was also triggered but with no sign of contact, hence it may have been triggered by the weight of the vehicle. The figures below show the two hardboards after flailing. The transverse board indicates that poor flailing occurred in the bottom of the dip, whilst the longitudinal board indicates that the depth of flailing was not consistent.


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Figure 5-24 Transverse board

Figure 5-25 Longitudinal board

Similar results were obtained when flailing under remote control. Although no boards or mines were buried, it was clear that both forward speed and depth of engagement were difficult to control.

5.5.3 Slope and ditch clearance

One of the more distinctive features of the Armtrac 75 is its extending arm to which the flail (or other tool) is attached. This makes it particularly versatile for working in awkward areas such as the sides of slopes or ditches and trenches – features that normally prove difficult for mine clearance machines. Hence a series of tests were set up to assess the ability of the machine to clear the sides of steep slopes and deep ditches.

A board was buried in the side of a large embankment (with an inclination of about 45°), the Armtrac 75 then flailed a strip up the side of it. As can be seen in the figures below, it was able to effectively clear the bank to a height of around 3m.


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Figure 5-26 Flailing embankment

Figure 5-27 Embankment and board after flailing

A small ditch was then prepared, with a board buried in the bottom and MRMs on each side as shown below. The ditch was flailed and both mines were broken up. The extracted board shows that the depth of flailing was not even all the way across, but averaged about 10cm.


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Figure 5-28 Small ditch

Figure 5-29 Small ditch after flailing

0.9m

2.8m

PMN @ 10cm

PMA2 flush (under overhang)


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Figure 5-30 Small ditch board

A larger ditch was then prepared in a similar way, with two boards buried – one in the bottom and one in the side nearest to the machine. Two MRMs were buried on the opposite side.

Figure 5-31 Large ditch

The machine cleared both mines and was able to reach into the bottom of the ditch and 1.2m up the opposite side. The board on the nearside was completely destroyed, the board in the bottom was cut away to a depth of about 15cm:

PMA2 @ 6cm

4.7m

1.7m

PMN @ 6cm


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Figure 5-32 Large ditch board (from bottom)

Figure 5-33 Flailing large ditch

The figure below shows the ditch after flailing. It can be seen that where the chains have encountered large rocks, they have spread and passed each side of them leaving ridges of unflailed soil, in the same way as occurs when the vehicle is moving forwards too quickly.


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Figure 5-34 Large ditch after flailing

In order to determine the maximum depth of ditch that could theoretically be cleared, the Armtrac 75 was positioned on top of a 2.2m tall loading ramp with the flail lowered as far as possible, as shown in the figure below. There was found to be 25cm of chain length on the ground, giving a total vertical reach of 2.45m. Hence it could clear down to 20cm in the bottom of a 2.25m ditch. This does not take into account the need for forward reach where the sides of a ditch are sloping as would normally be the case, which will limit vertical reach.


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Figure 5-35 Armtrac 75 on loading ramp

5.6 Vegetation clearance

In many situations flails are used just to clear vegetation without engaging the ground and hence the ability of the Armtrac 75 to do this was assessed.

The first test involved clearing two 25m long strips of light bracken with a few small gorse bushes. The times taken were approximately 1min 20secs and 1min 30secs, corresponding to an average speed of about 1km/h. The second run included clearing slightly heavier vegetation, with stems of around 50mm diameter. The figures below show the type of vegetation being cleared and the condition of the ground afterwards.


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Figure 5-36 Vegetation before and after flailing

Further attempts at clearing vegetation resulted in the machine getting stuck due to the soil being soft. It was not therefore possible to obtain an indication of the rate at which heavier vegetation could be cleared, or the maximum stem diameter that could be broken up. However, the tests described above did include clearing a small number of isolated bushes of substantial size and the machine appeared to be quite capable. More extensive testing of the Armtrac 100 conducted in 2002, which used a very similar flail unit, suggests that this system is well suited to vegetation clearance [5].

5.7 Logistics

During the five days of the trial, records were kept of fuel consumed and any maintenance carried out. Maintenance requirements are only indicative since the machine was brand new and still considered a prototype, hence experienced several minor faults that would be unlikely to occur on a production version. However they are recorded here for completeness.

Total engine hours : 17

Fuel used : 72 litres

Faults : oil pressure switch damaged during tilt test, resulted in engine management system shutting engine down. Several occurrences of a minor hydraulic oil leak.

The damage to the oil pressure switch resulted in the machine being inoperative for about half a day and required a Deutz engineer to be called out for diagnosis and repair. This highlighted the benefit of thorough ‘shakedown’ testing as the fault was thought to have occurred due to the switch contacting the chassis as the engine rocked during the tilt test. This minor design flaw could have resulted in substantial cost and inconvenience if it were not rectified prior to the machine being deployed.


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5.8 Multi-tool versatility

Although it does not fall into any of the pre-planned test categories, one important feature of the machine is worth highlighting – its ability to switch between various tools using standard tele-handler attachments. For the trial, these included a bucket and forks in addition to the flail unit. The speed with which these could be interchanged was demonstrated and a small test was set up whereby the bucket was used to collect some rocks and dump them in a pile, the bucket was exchanged for the flail and the pile flailed, then the bucket used again to level the remaining debris. Changing one tool for another took about 2 minutes, connecting or disconnecting the hydraulic pipes for the flail added about another 2 minutes. The machine and its three tools could all be loaded onto the low loader within about 3 minutes.

Figure 5-37 Armtrac 75 with selection of tools


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6 Conclusions Overall the Armtrac 75 was considered to have the potential to be a useful tool for mechanically assisted demining. A number of particularly useful features and capabilities were recognised, but also a number of significant shortcomings. These are summarised below.

Shortcomings:

• Minimum speed too high. The lowest forward speed attainable (about 0.8km/h) would only allow reliable flailing down to a depth of about 10cm. It is believed the machine is capable of flailing down to about 20cm (which is essential for useful mine clearance), but for this to be achieved the minimum speed will need to be reduced to around 0.2-0.4km/h.

• Fine speed control difficult. The linear speed controller did not allow fine control at low speeds. Hence the smallest movement of the controller resulted in a large jump in speed. This is unacceptable as variations in soil hardness and clearance depth require accurate control of forward speed.

• Ground contour following difficult. The operator needs to continually adjust the height of the flail to maintain a constant clearance depth on uneven terrain and this proved to be difficult. It is believed this was exaggerated by the excessive forward speed, but some form of automatic height control would be very beneficial.

• Remote control of speed, direction and flail height particularly difficult. The problems described above were worsened when the machine was under remote control, due to limited feedback to the operator. Difficulty was also experienced in maintaining a straight line of travel as the steering did not self-centre.

• Gets bogged very easily. The machine readily got bogged down in soft ground, due to high loading on small wheels. This is likely to be very restrictive in field use. This limited the extent to which the vegetation clearance of the machine could be assessed.

• Insufficient torque at wheels limits hill climbing ability. Power to weight ratio is adequate for good hill climbing, but it is currently limited by the torque available from the drive motor.

Positive features:

• Excellent reach with extending arm and good articulation – very useful for clearing banks and trenches.

• Self extraction when bogged down. The extending arm proved invaluable for pushing the machine backwards when it got bogged down.

• Multiple tool capability, for good versatility. This is likely to be an attractive feature for many demining scenarios where the ability of a machine to undertake several different tasks can increase its cost effectiveness greatly.

• Compact size, easily transportable. These are important features, particularly in areas where infrastructure is poor resulting in great difficulty moving large heavy machinery between sites.

• Highly manoeuvrable. 4-wheel steer results in a very small turning circle, crab steering capability has the potential to be useful in confined areas or for operating close to ditches/trenches.

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There are not thought to be any other machines available that offer this same combination of features and versatility, hence if the shortcomings can be overcome (and it is believed they are all solvable) the Armtrac 75 may well prove attractive to potential users.

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7 Recommendations The most important conclusion is that the minimum forward speed of the machine is too high for effective flailing. Because of this, it is recommended that the vehicle does not proceed to phase 2 of the proposed tests (comprehensive mine clearance performance tests) until modifications have been incorporated to correct this.

Other recommended modifications which do not necessarily preclude further testing but which would still be beneficial are as follows:

• Automatic ground contour following • Increased torque at wheels (which will be achieved if gearing is reduced) • Self-centring steering for remote control • Limited slip differentials • Lower ground pressure, through bigger tyres or lower tyre pressures • Video feedback for operation under remote control

Assuming that the gearing is modified as recommended, it is believed that the Armtrac 75 has the potential to be a valuable tool for the demining community and it is recommended that it be considered for field use, particularly in situations where its good reach and multi-tool versatility can be exploited.

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8 References [1] Armtrac 75 Evaluation Trials Plan, QINETIQ/FST/TI41098, C Leach, February 2004 [2] Armtrac 75 Evaluation Safety Plan, QINETIQ/FST/SAF041100, C Leach, February

2004 [3] Armtrac 75 Trial Environmental Assessment, R Denny, 1st February 2004 [4] Technical Report on the Evaluation Trials of the ARMTRAC 75 MINE CLEARANCE

FLAIL MACHINE, R Gravett, MAG, March 2004 [5] Armtrac 100 Trial Report, QINETIQ/FST/CRMV/CR022665, C Leach, April 2002

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Initial distribution list External

A Willson DFID

A Craib BARIC Consultants

S Brown Armtrac

R Gravett MAG

F Bory ITEP

G Danielsson SWEDEC

G Coley CCMAT

QinetiQ

J Hambly MCES

D Lewis MCES

File 290572/0015

Information Resources

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Report documentation page Originator's Report Number QINETIQ/FST/TRD042153

Originator's Name and Location Peter Blatchford, QinetiQ Pyestock

Customer Contract Number and Period Covered CNTR012395

Customer Sponsor's Post/Name and Location A Wilson, DFID

Report Protective Marking and any other markings

Date of issue Pagination No. of references

Unclassified March 2004 Cover + 45 4

Report Title

Armtrac 75 Assessment Phase 1

Translation / Conference details (if translation give foreign title / if part of conference then give conference particulars)

Title Protective Marking Unclassified

Authors Peter Blatchford, Chris Leach

Downgrading Statement

Secondary Release Limitations

Announcement Limitations

Keywords / Descriptors Mine clearance, flail, assessment

Abstract

The results of a trial to assess the mobility and performance of the Armtrac 75 mine clearing flail. The conclusions are that the machine has the potential to be a useful tool for humanitarian demining, but is limited by an excessive minimum speed which prevents effective flailing to a depth greater than about 10cm.

Abstract Protective Marking: Unclassified

This form meets DRIC-SPEC 1000 issue 7

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Armtrac 75 Assessment Phase 1 - GICHD