Centenary Bulletin 19 – Horton Fan Clutches

February 13, 2019

As Textiles, Carbon Black and Off-Road machinery had been the back-bone of Norman G Clark in its first 50 years – Horton and its air operated clutches and brakes were the basis of our success in the second half of the century.

John Clark had formed the relationship with Hugh Schilling, of Horton, in Minneapolis in 1963 and local manufacturing of the Horton Air Champ clutches and brakes became firmly established in subsequent years.

One of the interesting early applications for Air Champ, was fitting a Horton clutch to the air conditioning system of an Ansett Pioneer rear engine tourist bus. While the unit performed well in the workshop, bearing collapse always seemed to occur between remote service locations on the Kimberley coast road, with 100 degree plus days, and a full load of passengers who predictably were not very impressed.

By upgrading the bearings to double row high temperature models acceptable bearing life was obtained, but the combination of high ambient temperatures and diesel engine vibration was a warning for what was to come.

At the same time, on the other side of the world, Horton were also working on a similar clutch installation on trucks fitted with snow clearing equipment. In a Minnesota winter, a diesel engine never warmed up enough for the radiator to allow cabin heating for the driver. The solution was to stop the fan and only engage it when required by engine temperature. The Horton Fan Clutch had been born.

Bearing problems, due to engine vibration, soon became the main problem. By upgrading the bearings Horton developed a product that was reliable enough for the winter snow clearing season, however, this was a very small niche market.

In 1972 the Middle East Oil Crisis caused alarm around the world as the price of oil products rose sharply. Large consumers of petroleum products became very cost conscious and went looking for ways to reduce fuel consumption. The solution for the trucking industry was to stop the engine cooling fan when not required. This could give improved fuel economies of 5% to 10 %, and for large truck fleets, this amounted to significant savings. The fan clutch was immediately in demand on new vehicles, and became an optional fit for most truck fleets.

As the oil crisis passed, and fuel prices fell, the benefits of a fan clutch were not as apparent. However, the US government through the EPA, passed environmental noise legislation which was aimed directly at heavy duty trucks. Around one quarter of the noise produced by a vehicle comes from the fan, and by disengaging it for most of the vehicle is operating time, significant overall vehicle noise reduction is achieved.

This meant the truck manufacturers had a need to fit fan clutches, demanded by legislation, and the Horton Fan Clutch became the industry standard.

The final legislative requirement made on the truck industry was the Clean Air Act demanding regular improvements to engine emissions. One of the ways for diesel engines to operate within these emission requirements is to keep the engine temperature within a narrow band at the top end of the operating spectrum. Temperature control could be best obtained using a fan clutch to only cool an engine when it was at the top end of its optimal operating range. Again, the Horton Fan Clutch was perfect for this task.

The original Horton Air Champ clutch was an air operated / spring disengaged clutch. Norman G Clark introduced the Horton Fan Clutch to Australia in 1975 based on the same air-on / spring-off concept as the Air Champ Clutch. Horton have since added spring-on / air-off, 2-speed and multi-speed, and viscous drive versions to their range together with several different control options. These variations can be used in different applications, in different industries, and give Horton a full range to suit many different operating requirements.

We quickly found out that while Australia had a significant local manufacturing base of both American and European truck brands, the locals had modified the original truck designs to accommodate Australian conditions. The local manufacturers were not very interested in fitting anything to their trucks which complicated their manufacturing process. The demand for new ideas had to come from their customers, who soon found the 5%-10% fuel saving most attractive and insisted that their truck needed a temperature-controlled fan drive.

Compared to the USA or Europe, the Australian truck operator was much harder on his equipment driving faster on poorer roads, with heavier loads and in higher ambient temperatures and less stringent maintenance regimes. On top of that, simple things like right-hand drive vehicles meant that under bonnet designs needed modification to accommodate a steering column beside the exhaust system with its additional heat loads.

Finally, double, triple and up to seven trailer operations put demands on the truck not seen elsewhere in the world.

Evolving environmental requirements, for emission reductions, have forced diesel engine manufacturers to run their engines in a narrow temperature range at the upper-end of temperature scale, resulting in tighter fan clutch control demands and even more stress on the fan clutch itself.

The Horton Fan Clutch was very much adaptable, and after more than forty years, has evolved to the point where it is the only realistic option for heavy duty truck operations in Australia. Australian operating conditions and expectations of truck operators, far exceed overseas demands, and the Horton Fan Clutch of today, made by Norman G Clark, has constantly evolved to accommodate these demands.

The most exciting future prospects for the Horton Fan Clutch are in the off-road market, with clutch requirements for mining and stationary applications now becoming essential. The situation is like the on-road truck market. Customers are demanding better fuel consumption, noise reduction, and exhaust emission controls to meet industry standards. Stopping the fan also makes additional horsepower available to give the vehicle better operating capacity.

In 1999, the Schilling family decided to split the two arms of their air drive business into separate companies.

The Air Champ products are essentially industrial drives sold to many different industries, across a large customer base, in low volume lots, with a wide range of applications and uses. A lot of technical support is required for each sale, and consequently, the customer recognised that there was a premium price is justified to support the engineering input.

The Fan Clutch, on the other hand, is sold into the truck market where the volumes are high and the model range much smaller. The truck manufacturing customer base is also much smaller, and the industry is much more demanding of cost reductions. Once the application is engineered into an application, very little engineering support is required. At the same time, the truck industry needs a broad range of after sales support at the dealer and operator level.

The decision to split the business into two companies was sensible and practical. The Horton name remains with the Fan Clutch business. The new industrial company which manufactures and distributes Air Champ is known as Nexen.

Both companies have added to their product ranges substantially since 1999. Horton have expanded the fan clutch range acquiring a German subsidiary making viscous fan drives, cooling fan manufacturing and targeting the agricultural, stationary and mining markets for fan and fan drive opportunities.

Nexen have taken the basic air drive principles and expanded into safety controls, linear controls and precision motion control devices.

Norman G Clark, in its one-hundredth year, still highly values both Horton and Nexen, these principals and continues to actively and successfully promote their products in our region.

Engine Fans

When Norman G Clark first started selling fan clutches for non-American engines, there were problems adapting the original fan being used on these engines to suit our clutches. We eventually found a solution in a very good nine bladed plastic fan, fitted as standard on MAN trucks and buses.

This fan, we eventually discovered, was manufactured in Germany, and when we specified bigger diameters and bigger capacity fans, MAN told us to buy the product ourselves direct from the German manufacturer.

Although a good suggestion, the Germans were not terribly interested, and advised us that they only did business with engine manufacturers, and we did not qualify. We told them that we were an OEM and that our interest was for the supply of the fan with our fan clutch, which we fitted to almost every truck built in Australia with a US type diesel engine. At that point they agreed to sell to us, and we sold hundreds as retrofits to the truck manufacturers.

We found out the hard way that the fan was good, but it had zero tolerance to striking anything, and because there was quite a lot of blade flexing under load, there had to be reasonable clearance around the fan to guarantee its survival.

Ford trucks had an enormous number of failures due to a very tight clearance and vibration. It took some considerable effort to convince them that it was basically their design, and not the fan, that was responsible for all the plastic littering the national highways.

Everything about a plastic fan is better than metal. There is an enormous weight advantage, the noise level is lower as there is no resonance, and the lack of rivets and reinforcing plates means a cleaner air flow.

The moulded plastic fan business was relatively easy to enter for any company with access to large diameter injection moulding machines, however, the “black art” of air movement in a constricted engine compartment, with the ram airflow on a moving vehicle over a rotating fan required some very sophisticated engineering to achieve high performance.

Eventually Horton purchased a fan manufacturer, and designed a range of fans which were to be fully compatible with the Horton Fan Clutch. Horton have moved these fan designs forward, and broadened the range, to include large diameter fans for off-road and stationary machines.

The off-road market has enormous potential, not only for high performance fans, but also for next generation controllable fan drives. The Horton developments in this area are now being introduced to the mining industry. They are being very well received due to their outstanding fuel saving and noise reduction benefits.

Horton now have the best and most versatile range of fans to suit a wide range of vehicle cooling needs