Trackmobile® Technology

In 1814 English engineer George Stephenson built the first steam locomotive for operation on iron rails. It was unique from previous self-powered steam vehicles in this respect; For traction it used flanged steel wheels for adhesion to steel rails. One hundred ninety years ago flanged steel wheels became the standard for worldwide railroading. Trackmobile® subscribes to that standard for the same reasons as the railroads:

• Steel wheels are more durable than rubber or polyurethane
• The coefficient of friction for steel on steel is more consistent over a range of conditions (snow, ice, rain, contamination) than the coefficient for rubber or polyurethane on steel
• Steel wheels have far less rolling resistance than rubber or polyurethane tires
• Steel wheels are unaffected by raised frogs, switch points, gaps between rails and by material packed into grade crossings
• Steel wheels maintain point contact with the rail while rubber pneumatic tires deform over the 2 inch (51mm) width of the railhead
• Steel wheels are puncture-proof while rubber tires must be either solid rubber or foam-filled to avoid puncture

The point about deformation is important. Tires are designed to spread their loads over the entire width of the tread positioned on a flat driving surface. When a pneumatic rubber tire is placed on a railhead, one fourth of the vehicle weight plus some weight transferred from trailing loads is concentrated on only 2 inches (51mm) of the tread width. The photo above shows how a tire deforms under a 42,000 pound (19,000kg) vehicle because 75% of the tread width of a typical industrial tire is unsupported. The deformation imposes loads on tire sidewalls, cords and beads that are not experienced in normal tire applications.

Additionally, while rubber has good characteristics under compressive loads, it does not have good shear resistance. In a rail application, the tires are subjected to compression of the vehicle weight, and simultaneously to shear forces when torque is applied to rotate the tire. Under shear plus compression forces plus friction between the tire and the steel rail, the tread rubber heats rapidly to the point the rubber breaks down.

For these reasons, steel wheels have always been chosen over rubber in serious railroading.

Durability: How long do the wheels last?

Steel wheels have proven to be more durable and long lasting than either rubber or polyurethane. The friction created from operating on rails produces much less wear on steel wheels than with other materials. Steel wheels are also puncture-proof, while rubber tires must be either solid rubber or foam-filled to avoid puncture. These factors ensure that steel wheels need to be replaced far less frequently than rubber or polyurethane wheels, which saves you time and money associated with maintenance costs.

Adhesion: How well does the wheel grab the rail?

Any number of conditions can affect how well a wheel adheres to the rails: snow, ice, rain, or many different types of debris or environmental contaminants. The coefficient of friction for steel on steel remains more consistent throughout these conditions than the coefficient for rubber or polyurethane on steel. In other words, steel wheels are capable of adhering to the rail better, despite these conditions. There is also far less rolling resistance with steel wheels, as opposed to rubber or polyurethane. Similarly, steel wheels are unaffected by a range of railway obstructions, such as raised frogs, switch points, gaps between rails, and by material packed into grade crossings. The ability to perform consistently over both natural and constructed conditions is a key factor in our decision to use steel wheels.

Steel wheels are designed to maintain point contact with the rail. The width of the wheel is comparable to the width of the rail head which helps distribute the weight of the load evenly across each wheel. Rubber tires are much wider, so they deform over the width of the rail head. When a pneumatic rubber tire is placed on a railhead, one fourth of the vehicle weight plus some weight transferred from trailing loads is concentrated on only 2 inches of the tread width. Because of this, 75% of the tread width of a typical industrial tire is unsupported. The deformation imposes loads on tire sidewalls, cords and beads that are not experienced in normal tire applications.

Tractive effort of a rail vehicle depends upon the weight of the vehicle. The higher the weight, the higher the tractive effort. Weight transfer is a simple means of increasing the weight of the traction vehicle using part of the weight of railcars coupled to it.

To take weight transfer, couple to one or two railcars, move a lever and raise the coupler(s). With finger-tip control, add up to 96,000 lbs (43,545 kg) to the weight of the Trackmobile®.

When additional weight for traction is no longer needed, move a lever and lower the coupler.

Is it complicated?

The system consists of a control valve, hoses and cylinders, the same as any hydraulic circuit. The guide wheel system on some mobile railcar movers actually has more components and requires more management than our weight transfer system. Elementary operator training covers use of weight transfer, which has been mastered by operators worldwide for more than 50 years.

Are there lots of Parts & Components?

It has the normal components found in any hydraulic system, including pump, tank, hoses, valves and cylinders. Mobile railcar movers that use rubber tires for drive must have a guide wheel system to keep the vehicle on the rails. The guide wheel system is also a hydraulic system and has the same basic components plus some specialized items. This chart gives a side-by-side comparison of the parts making up a weight transfer system and a guide wheel system.

As Trackmobile® products use flanged steel wheels for both traction and guidance on rail,
no guide wheels are required.

Is wheelbase important in Railcar Mover Technology?

Because Trackmobile® products use flanged steel wheels for both for traction and guidance. Yes, it is an important predictor of stability in curves. The shorter the wheelbase, the more the stability in curves. In our literature we always state the wheelbase as measured from the centers of flanged steel wheels. Other railcar mover literature shows the wheelbase measured from rubber tire center to rubber tire center, but does not show the wheelbase measured from guide wheel centerline to guide wheel centerline. This additional length adds up to 18% to the wheelbase. This is an important measurement when considering performance in curves.

Is a Computer-based System required ?

No. Our optional Max-Tran weight transfer management system aids the operator, enhancing his or her performance, but it’s not necessary.

Why Weight Transfer?

Because there is no point carrying dead weight when it isn’t needed. During road movement or during a portion of the work cycle when only the Trackmobile® vehicle itself is being moved, for example. During these times, the Trackmobile® is moving only its basic weight, saving fuel and wear and tear on the tracks and roadbed.

What about empty Railcars?

We can’t transfer weight that isn’t there, but we can transfer up to half of the empty weight of the car coupled to the Trackmobile® unit. That amounts to thousands of pounds and adds thousands of pounds of tractive effort. Additionally, rail-to-road conversion permits the Trackmobile® unit to position itself to take advantage of the heaviest railcars.

A Trackmobile® team of salespersons and engineers attended the Wabtec Corporation Freight Car Basic Air Brake Seminar in Wilmerding, PA. The seminar was conducted by Michael Zenert, Manager, Air Brake Training. Zenert is recognized nationally and internationally as an expert in the field of train air brake systems, and conducts seminars all over the world for railroad personnel, railroad shippers and original equipment manufacturers in the railroad industry. Our team completed hands-on laboratories and a written exam for Single Car Tests in accordance with Association of American Railroads (AAR) S-486 standards, and Federal Railroad Administration (FRA) Part 49, 232 standards. We want to share our expertise in this field with Trackmobile® distributors and customers with a brief analysis and animation showing important operating principles of train brake systems used throughout North America.

We trust that this information will be useful to increase the knowledge base and professionalism of the operators and crews using Trackmobile® equipment.

Train Air Charge Indicator

Train Air Brake Hold

Trackmobile®, Inc., and Ingersoll-Rand have teamed up to bring you the best and highest output train air pneumatics in the business: Originally an upgrade option with Magnum Series Trackmobiles and now Ingersoll-Rand Force 12 Pneumatics are standard equipment standard on the Atlas, Titan & Hercules model Trackmobiles® and available as optional equipment on our other current model Trackmobiles®. The power of Force 12 Pneumatics comes from an Ingersoll-Rand rotary screw-type airend, blasting our train air brake capacity from 37 cfm or even our optional 65 cfm system to an amazing 100 CFM.

Force 12 Pneumatics Features