29 September 2000

Transmission

technology on move again

By David Anthony

FOR many tractor drivers the most significant design improvement during the last 10 years has been the development of new easy-to-use transmissions.

This is also the trend for ATVs, with new and updated drive systems near the top of the priority list for the design engineers.

When the first ATVs arrived on UK farms gear shifting was controlled by a foot pedal, a familiar technique for motor-cycle enthusiasts, but not always ideal when wearing big, mud-caked boots.

Shifting by foot pedal is still widely available – and plenty of users prefer to use their feet – but all the leading ATV companies now offer at least some models with either an automatic transmission or an electrically controlled push-button shift system, and both are taking a bigger slice of the market.

Automatic transmissions have been available for ATVs since the mid 1980s when E P Barrus began distributing the American built Polaris range with a constantly variable transmission or CVT included in the standard specification. CVTs, which use a belt and pulley drive to change ratios automatically in response to changing engine revs, usually allow the operator to select from two or three different ranges.

Since then many of the other ATV companies have brought CVT type transmission options into their ranges. Recent arrivals include Yamaha with a CVT drive on their Kodiak 400 model announced earlier this year, and the same type of transmission is standard on Yamahas Grizzly 600 with an impressive 37hp rated output, said to be the most powerful four-wheel drive ATV available.

New addition

The newest addition to the Kawasaki range, the KVF300A announced at the end of last year, also has a CVT auto drive to transmit the power from the 290cc engine, and the Quad Master 500 powered by a 493cc engine, is the latest arrival from Suzuki and also their first CVT drive model. There is also a recently introduced CVT model at the top of the Arctic Cat ATV range, and as the Massey Ferguson ATVs announced this summer are all based on the Arctic Cat range, the top MF model also features the auto transmission.

An alternative to a fully automatic transmission is using an electric switch mounted on the handlebars to give finger-tip control of gear shifting. This is similar to the push-button controls on some tractor transmissions and is the system chosen by the Bombardier company for their Traxter ATV announced in the UK in the spring. Press the rocker switch on the handlebars upwards to select a higher gear or down for a lower ratio, while a selector lever allows the operator to choose high or low ratio and also includes neutral and reverse plus a "park" setting.

Switch control

Honda, easily the top-selling ATV range in the UK, has also chosen a switch control. It is called the ES or Electric Shift Programme and is an option on the FourTrax 350 announced in July and on the older 450 model. Specifying ES adds between £200 and £300 to list prices, and it is a popular option according to David Williams, ATV manager for Fieldens of Stowmarket, Suffolk.

Well over 50% of his customers for the 450 specify the ES version, and with the newer 350 model the figure is similar, showing that many farmers believe the benefits of the push-button transmission outweigh the extra cost.

"The main advantage of both ES and an automatic transmission is that the operator does not use his foot for gear changing, and that means you can have proper footwells which are much more comfortable and give better protection from injury," says Mr Williams.

"The ES control is also popular in the used ATV market, and this shows up in trade-in values."

But for some operators a push-button shift is not the best choice, he says. A recent example was a sheep farmer customer who sometimes needs one hand free to carry a lamb. With the right hand working the throttle control, the left hand would be needed for the lamb and would not be available to operate the gearshift switch.

"If the driver needs to keep one hand free, a transmission with a conventional foot control or an automatic is more suitable, and this would include anyone working with a hand-held lance for patch spraying, for example."

An indication of future developments in ATV transmissions comes from America where Honda has recently announced the Rubicon 500 with a completely new drive system. Although the 500 is not available in this country, reports from the US show that Honda has ignored the familiar CVT approach used by most of its rivals and developed its own fully automatic transmission, described by one American magazine as "an amazing piece of technology."

Instead of drive belts the Hondamatic transmission uses a hydraulic pump to provide an oil flow to power a variable-pitch swash plate motor with electronic control.

The result is a high tech version of the hydrostatic transmissions used on equipment such as combine harvesters and ride-on lawnmowers, giving smooth, infinitely variable speed control.

The hydrostatic transmission unit is sealed and is claimed to require no servicing, and the controls include a mode selector with speed, torque and manual shift settings. There is also a hand lever to select drive, low, neutral and reverse, plus a switch allowing manual selection of five different drive settings.

Although Honda has no immediate plans to import the 500, a spokesman confirmed that it is a potential candidate for their UK range. &#42

Kawasakis KVF 3000 complete with automatic transmission.

Suzukis LT500 has a five-speed manual transmission with a high/low ratio box.