International Harvester Payhauler

a Tonka Truck

Getting a Load of Rock

Getting a Load of Pulp wood

The following International Payhauler is a 25 ton model implying that it is designed to haul a net load of 25 tons. It is called a rigid frame truck because the frame is very stiff, and unlike a highway truck, the frame of this truck is designed NOT to flex with the twists of the road. The tare weight is in the 30 ton range (or a little more). Rear tires are 18x25 20 ply and the fronts are 14x24 20 ply. The stock engine was a turbo-charged 743 cu. in. Cummins intended to produce 335 hp. An large multi-speed automatic transmission is provided. A melted down exhaust manifold is a symptom of engine overloading and was eventually the downfall of the stock engine in this vehicle as around our place the rock moves out of the borrow pit and up an extended 15% adverse road. It has now been repowered with a more modern 855 Cu. in Cummins 350. It does better, but one must still watch the pyrometer carefully to avoid turbo and manifold meltdown. There are good reasons for attempting to keep adverse grades (ones you must go up) under 10% (federal highways require 6%, and Railroads 1%) but when you are in the mountains it is not that easy, and in laying out a haul road one must often balance running it all over creation (to get a better grade) or just going where you need to go.

Everything about this Payhauler is big and ugly, although by contemporary standards for rock trucks it is not a large one. Indeed in the 25 ton class nearly all the 'rock trucks' are now of an articulated design instead of the classic 'rigid frame'. You often see these on construction jobs. They are fairly low to the ground and are 4 wheel drive and steer by bending in the middle behind the cab. These articulated trucks get around a lot better in soft ground and under poor traction conditions.

Regardless of brand, you can often judge the size of a rock truck by the size of tires that it utilizes. The 25 ton models classically have 18x25 dual rear tires and 14x24 fronts. In this configuration these vehicles have the load almost balanced over the rear tires. The next size up is a 35 ton truck. They typically have a slightly longer bed and 18x25 front tires and, of course a more powerful engine, but will otherwise be similar in appearance. Beyond that there are 50, 75 and 100 ton rock trucks as well as even larger ones, however , their gross size limits their usefulness to large mining operations. As you can see here, this model has multiple uses.

Euclid R190

Just as an example of a larger rock truck what you see here is an Euclid R190 which is of a serious size. Note the ladder up ot the front bumper and then the stairway up the front to the driver`s compartment. You aren't likely to find this puppy cruising the Interstate during rush hour, but if you do, yield the right of way. Unlike the smaller trucks which can be used for a variety of things, the mass size of these trucks limits their use to open pit mining operations. To work efficiently they have to be matched to a loader that will load them in 3 to 5 scoops which also implies a rather large loader. Furthermore to keep the loader busy one usually has a string of several trucks all of which implies that one must want to move a lot of daily tonnage to use vehicles of this size.