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EARLIER PROTOTYPES |
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Prodders - 1996 and 19971997-2000***Development responsibility: HARC What are prodders used for?The deminer needs a range of specialised tools. The heart of the manual demining process is searching through the ground for buried mines. The most primitive (and sometimes the only method) is to probe the ground with a sharp pointed tool (called a probe or prodder) searching for a hard object large enough to be a mine. In some areas, tree roots, rocks, rubbish, rubble, pipes etc. may make this impractical, in which case the ground has to be literally excavated or dismantled to perform this search process. Dogs or metal detectors can often be used to reduce the size of the area which needs to be probed or excavated. Origin of concept Afghan deminers currently use bayonets and small picks for prodding. The accident rate is unacceptably high (particularly with PMN mines) and the work is slow and tedious. Improved tools are essential to improve safety and to speed up the work. Bayonets are light and effective, but expose the user to severe risk of hand injuries (at the minimum). They cause calluses to the user's hand, which reduces sensitivity to touch: this being essential for detecting buried targets.
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Demonstration prototype Constructed in August 1996. The prodder consisted of a force sensing handle (axial) with a glass fibre fishing rod tip. A simple pre-loaded axial compression spring provides the force sensing. The deminer only feels a sensation when the force exceeds 2.5 Kg (level can be adjusted, but not by deminer). Simulated field demonstrations The prodder was too delicate for hard ground conditions. If the deminer always keeps within the force limit, progress is much slower. See hard ground prodding technique. Deminers need to exert large forces when digging near the suspect metal target or mine, but are careful when they are very close. Status (July 1997) Used for demonstrations at UWA only. |
Development responsibility: UWA
Origin of concept
Charles Trevelyan suggested that a pistol grip would be much more comfortable for extended prodding than the axial grip of a bayonet. A concept model (2a) was made in September 1996, with mechanical force overload sensing.
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Demonstration prototype (2b) Constructed in December 1996. The prodder consisted of a pistol grip force sensing handle (axial) with a 3mm thick steel blade about 250 mm long. A guard was fitted to protect against mine explosions. The force sensing device is a steel bar which emerges from the length of the back of the handle against the palm of the hand when the pre-set force is exceeded. Simulated field demonstrations The prodder worked well in hard ground conditions. If the deminer always keeps within the force limit, progress is much slower. Most of the early stage of prodding consists of excavating a trench in the ground which is gradually extended towards the suspected target location. Therefore, much of the time the force level exceeded the pre-set limit and this caused some discomfort to the palm of the hand. Ideally, the force overload mechanism needs to be turned off for all except the final phase of prodding around the suspected target location. Comments from Deminers The prodder was evaluated by deminers in January 1997. They liked the concept but found it was too heavy (it also incorporated a 6mm aluminium blast shield - see below). They thought the bayonet was preferable. The mechanism requires extensive simplification and design for low-cost manufacture. Status (July 1997) Used for display purposes at UWA, only. |
Development responsibility: HARC
Origin of concept
This evolved from the comments on version 2b. Brett McLean (UWA honours student) was asked to design a low-cost prodder with the best of the ideas from version 2, aiming for a light weight design. We decided to leave out force sensing for the time being.
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Demonstration prototype Constructed in May 1997 (after several other trial versions). Features include the use of a commercial saw handle for a comfortable grip and folded sheet metal blade. The prototype has been designed for soft and hard ground, but probably works better in soft ground. It requires extended simulated field tests. The blade has a sharp edge, with saw teeth for cutting roots and small bushes. The end is widened like a trowel to remove dirt from a trench or hole. |
Comments from Deminers
Received enthusiastically, though they suggested a narrower and longer blade. In June 1997 in Pakistan we learned that deminers use a prodder mainly as a scraper to expose buried objects. Before any excavation starts, the deminers scrape the ground surface (with great care) to see if a metal fragement lies on or just beneath the surface (most do).
Note that excavation could be speeded by removing spoil to a bucket or tray which is checked separately by a metal detector - when the metal object "hits" the tray, an indication is heard, so the deminer does not have to actually find the metal object which is normally covered in mud and so it is difficult to distinguish from a stone.
HARC Version
A local variant was made by HARC personnel in June 1997. Second model at UWA. Batch of 15 have been made for field trials in Pakistan.
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HARC Prodder (August 1997) The handle is custom made from plywood. The blade is made from re-cycled band-saw blade (high tensile steel) which is bent longitudinally, and reinforced with a folded mild steel backing strip along the top. The blast shield is recycled polycarbonate, hot-formed. Resilient self-adhesive tape (as used on bicycle handle-bars) can be wrapped around the hand grip. It requires extended simulated field tests. The blade has a sharp edge, with saw teeth for cutting roots and small bushes. The end is widened like a trowel to remove dirt from a trench or hole. |
Perth steel supplier, Atlas Steels, has suggested using stainless steel alloys for prodder blades. Samples of 3CR12 have been made for testing. Materials such as 430BA (bright annealed, used for dishwasher panels) and 2205 have also been suggested, because they combine toughness with abrasion and corrosion resistance.
Feedback from UNOCHA and deminers suggested that they are very happy, though the blast shield needed to be trimmed, and the blade needs more and deeper saw teeth. Simulated field tests by deminers to evaluate its durability commenced in November at Risalpur, Pakistan.
Deminer Feedback
1) The blade is tool long. The original intention was to keep the hand at least 300mm from the tip to reduce the chance of injuries. However the handle adds more length than we expected.
2) The reinforcing strip along the back of the blade adds weight and makes the prodder harder to push into the ground - this can be reduced or eliminated by changing the blade design.
3) The feature most liked by the deminers is the saw teeth - they make working in vegetation areas much easier than with bayonets.
4) The handle is attached at the wrong angle - the handle needs to be turned about 45 to 60 degrees counter-clockwise to the blade.
5) The deminers were worried that the fingers may be trapped in the handle and ripped off in the event of an accidental explosion.
6) The rigid guard, even when trimmed, gets in the way and can knock against the helmet visor.
The next step - prodder #3.
A new design will be tested with a shorter and modified handle and flexible blast shield in December.
Analysis of injury reports (Afghanistan, UNOCHA) revealed that most injuries occur in the deminer's prodding hand, upper arm, shoulder, neck, knees and lower legs. The majority of injuires are superficial, but are often sufficient to stop the deminer from working in the field because of finger/thumb amputation or severe hand injuries. It is very important, therefore, to try to design a prodder which provides effective protection to the deminer's hand.
Development responsibility: HARC
Origin of concept
Andy Smith has developed a U-ended prodder for probing in soft ground. (For Afghanistan - this ground condition is classified as "hard" in other countries!)
Soft Ground Prodder (or Probe)The prodder has a long in-line handle which suits a kneeling or squatting position. |
Status (December 1997)
A number of variants have been tried (prodder #2, 2A) and the blade now seems to be useful. Like #1, it has some saw teeth for cutting roots.
Design 2A overcomes a tendency for stones or mud to become jammed between the sides of the U.
Origin of concept
Afghan deminers prefer to squat because of considerable discomfort (heat, flying dust, insects, stones/sticks) when lying on the ground. Due to this, they expose themselves to much greater risk of serious injuries in the event of an accidental mine detonation.
However, longer tools may enable them to squat and work at a safer distance (1.5 - 2 metres).
Status (July 1997)Demonstration model built by first year engineering students. Awaiting further ideas and reactions from field. When in discussion with Bill van Ree, UNOCHA, he showed concern that the support device between the deminer and the mine might injure the deminer if blasted by a mine explosion. |
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