DIFFERENTIALS EXPLAINED

WHAT’S THE DIFF? WE EXPLAIN HOW A DIFFERENTIAL CONTROLS THE SPEED OF A 4X4’S WHEELS.

AUSTRALIAN-OWNED company KTI has designed and made the world’s smallest personal locating beacon (PLB) with a 10 year battery replacement interval: the SA2G PLB.

While the issue of battery replacement may seem minor, it’s an important consideration for owners of PLBS, as battery replacement can cost in excess of $200.

The KTI’S PLB has been approved for use on COSPAS-SARSAT – the only dedicated search and rescue satellite system. This means the product had to undergo elaborate and exhaustive tests to very explicit performance standards.

The KTI SA2G provides GPS position updates every five minutes, whereas some others only update every 20 minutes – or not at all. Being able to update your position is important if, for example, you’re in a current or if the original signal was corrupted, which can occur for many reasons.

The whip antenna has a 360-degree swivel for reliable satellite detection. So if you’re trapped upside-down in a vehicle rollover, or in the ocean, you can point the KTI’S antenna upwards at all times. It’s also selfbuoyant, while most rivals need some form of floatation jacket.

KTI’S PLB uses two batteries, each comprising two lithium cells – any system with in-built back-ups is a good thing. Each battery has a nominal capacity of nine watt hours once activated, but the device draws less than 0.5-watt per hour – so you should be okay for between 24-48 hours, provided the battery is fully functional.

Other key features of the KTI SA2G PLB include: 66 channels, fast acquisition GPS receiver, zero warm-up satellite communication technology, high intensity photoflash strobe light, ultra-compact size (88mm x 64mm x 31mm), ultralight weight (140g), waterproof, and resistance to immersion to more than three metres.

The SA2G has a 10 year warranty.

WHY do we need differentials? It’s simple: when turning a corner the outside wheel on an axle follows a larger arc than the inside wheel, so the differential gearing allows one wheel to travel at a different speed than the other, while both remain powered. But differential gearing also has the disadvantage of sending the power to the path of least resistance, just like water and electricity.