EXTRA
April 1999
HEAD to HEAD:
|
EXTRA
April 1999 HEAD to HEAD: |
 Metalsub pack clips on both ways up  The Metalsub pack can be disconnected |
Divers who need a lamp with high output and long burntime need one with a big battery. To keep such lamps manageable in the hand, they are now commonly designed with a battery pack separated from the lamphead by an umbilical. The pack can be integrated with the diver's kit - mounted on the tank, for instance - as a supplement to the weightbelt. Here we compare two lamps of this type. Neither is cheap. One is made in the Netherlands, the other in no-nonsense Yorkshire. With prices starting at £399, you'll buy a Metalsub Hi-tech Diving Lamp only if you are prepared to pay for the finest-quality engineering. So why include this seductive piece of almost paramilitary hardware in these pages? Well, car magazines test Ferraris when most readers buy Fords, and this is the equivalent. If your car was built like a Metalsub lamp, it would have a turret, tracks and scare traffic wardens. It is built to the same exacting standards as a multi-million pound fighting machine. The aluminium of both the battery pack and lamp are coated with a material "in accordance with American Military Standard MIL-A-8625E type 3 class 2" and impregnated with Teflon. It's a big boy's toy! The mounting bracket can be fitted to your tank either by using semi-permanent metal bands or by the 5cm webbing of your BC's camband. Rubber pads stop it slipping. The rectangular ni-cad battery pack clunks into place, like a magazine attaching to an M16 rifle. A precision, double-ball-bearing, stainless-steel clip keeps it there, either way up. The machined metal casing uses hexagonal-ended bolts. The lamp cable plugs in by way of a bayonet fitting, wet-proofed by an O-ring. A 90cm cable with spectacularly efficient cable protectors at either end connect the battery pack to the KL1270 lamphead (215 x 82mm diameter). The lamphead weighs about 0.1kg under water and burntime at full power is about 110 minutes. The battery pack weighs much the same as a Challenger tank in air, but little more than 2kg in water. A smaller pack (65min burntime) for the less muscular saves about 0.5kg. What colour is it all finished in? Gunmetal, of course. Julian Dyson's precision engineering company JMD Technologies makes radar, aerospace and communications components. Julian is also a diver. He appreciated the quality of a lamp like the Metalsub. but realised that few could afford one. Dismayed by the quality of more affordable items, he decided to build his own. Using Aluminium 6082, the JMD Umbilical Torch is similar to the Metalsub with smaller power packs. Its ni-cad pack, housed in a rectangular box, gives a burntime of 70min with the 50W bulb. BLUE LIGHT Both products use similar xenon gas-filled 50W bulbs. These lamps give a lot of light compared to halogen. Some of the more expensive German cars now have xenon headlamps - the ones that blind you with a characteristic blue light as they approach. The charger for the battery of the Metalsub is sophisticated, as one would expect. Electronics sense when the unit is fully charged, and switch to a pulse charge so that you can't overdo it. Simply unplug the lamp lead and substitute the charger lead. There is no need to jeopardise the watertightness of the battery casing. Unlike the Dutch product, the JMD lamphead is permanently linked by its cable to the power pack, which is charged for 16 hours by removing a threaded plug cover and inserting the charger's jack-plug in the hole. This disables the lamp, eliminating any chance of an accident. The charger had a three-pin plug. If you are careful about how you charge batteries, the JMD's method is adequate. If you are less methodical, you might save on expensive ni-cad replacements later by investing in the Metalsub. As on the Metalsub, the mounting plate for the JMD's power pack can be fitted via a camband, such as the BC's. The pack clamps on and is locked in place by a threaded stainless-steel pin. There are no rubber pads, so for use with an unnetted tank I suggest you improvise with a thin layer of neoprene to prevent slippage. The Metalsub is controlled by a collar switch. This has a locked-off position as well as a detent at which 50 per cent light output is delivered. A small stainless-steel shackle allows you to improvise a lanyard or clip it directly to your person. Rotating the handle of the JMD lamp both switches on its bulb and racks it forward progressively to alter the angle of the beam. A fine lanyard can be threaded through the small hole provided. I was circumspect about taking the Metalsub light abroad, convinced that one sight of it on an airport X-ray machine would have burly security women hustling me away. The JMD lamp was not exactly light to transport, either. It weighed the same as the smaller of its Dutch rivals. So I took them to good old Stoney Cove. It had no depth to challenge the Metalsub lamp's watertight integrity, rated to 100m, nor that of the JMD, said to be good for 150m. On a dark winter day, both lit up my underwater surroundings with equally broad, even beams, almost indistinguishable in spread, colour and brightness. PARKING SPACE The JMD lamp was more difficult to turn on and off with numbed hands; something very easy to do in the car park seemed extraordinarily difficult at 20m and 8°C. Nor did I find much advantage in being able to alter the beam angle, and tended to move it from "off" directly to its widest setting. Ribbing along the stem of the lamp-head would give a more precise grip. Ascending with both lights on must have resembled a close encounter of the third kind. Climbing out, I heard mutterings about decommissioning weapons, and nobody challenged me for a parking space! On my second dive, I inverted the Metalsub power pack. It was more convenient under water to have the cables coming from lower down. Inverting it was an instant manoeuvre, though with the JMD I would have had to derig it all and start again, as it fits only one way into its mounting plate. The fixed lamphead connection also made donning the full scuba rig more of a challenge, with yet another line in which to tangle. As the power began to run down, I discovered another difference between the two products. Electronics within the Metalsub lamp sense the drop in voltage and reduce the light output by half, once only eight minutes of burntime remains. To make sure you've noticed, it also makes the lamp flash on and off. The Metalsub products meet the highest standards of manufacturing; the JMD lamp did seem to have more sharp edges. I can promise any wrekkie that if you go in with a Metalsub light you won't come back with anything better. But the JMD always wins on price. The Metalsub KL1270 lamphead and PR1205 battery pack costs £399 (£500 with PR1208 pack). The JMD (A5070) Umbilical Diving Torch comes with red or blue anodised finish at £325, or extra-hard-wearing military green anodised finish at £35 extra. 
 JMD pack clips on one way only  The JMD pack cannot be disconnected |
