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Steel drive tapes in military sighting system

Edited by the Engineeringtalk editorial team Mar 23, 2001

It was the unique properties of a drive tape system that led to Belt Technologies' steel drive tapes being adopted by Avimo for a drive in the high precision mechanism of military sighting systems

Belt Technologies' steel drive tapes are used for many varied applications where a high precision zero-backlash drive is required.

It was the unique properties of a drive tape system that led to it being adopted by Avimo for an unusual application - providing a vital drive in the very high precision mechanism of all military sighting systems manufactured by the Taunton based company.

At the heart of each sighting system is a mechanism to provide information on how far to elevate the gun depending on how far the target is away.

Due to the optical effect of the sight mirror, a 1� movement of the mirror results in the actual line of sight moving by 2deg, making it necessary to have an exact 2:1 reduction within the sight mechanism to give a true reading.

Belt Technologies high tensile stainless steel drive tape, 8mm wide x 0.15mm thick, provides the critical drive to a large pulley attached to the sighting system mirror from a small pulley attached to the gun trunnions, giving a zero backlash drive of precisely 2:1 reduction, thereby assuring sight accuracy to the exacting standards required.

The unique advantages of metal drive tapes over other drive systems makes them ideal for high precision positioning applications requiring zero backlash and smooth operation.

With a high strength to weight ratio and high durability, the non-stretchable belts do not generate particulates, thereby ensuring non-contamination in sealed units such as the Avimo sighting systems.

A major priority for any military equipment is absolute reliability.

"The drive tape provides us with the very high accuracy and reliability we require," says Mr Laurence Mortimer, Mechanical Design Manager at Avimo.

"Before using the drive tape system we used a system of levers and forks that was very time consuming to set up and adjust.

Now, with the drive tape and accurately machined pulleys all we have to do is set the tension of the tape with turnbuckles." Because of the very high precision demands of the sighting systems, manufacture at Avimo is undertaken in a clean room environment.

Accuracy of the system is such that the presence of even the smallest foreign body between the rollers and drive tape would lead to errors in measurement, the sighting systems being accurate to better than 0.4 milliradians over 50�movement.

Being at the cutting edge of technology means that backup is essential to Avimo, Mr.Mortimer continued, "We always get excellent service from Belt Technologies.

We had a case where the ends of the tape were tending to pull out due to the attachment holes forming stress-raisers.

We needed to find a solution urgently and Belt Technologies came up with a special reinforcement tab, fusion welded on to the belt, and quickly solved the problem.".