12" Gauge Cast Iron Switches
The basic switch requirements demand a variety of radii to manipulate the track around columns, motors and any other obstructions, 5'- 6" and 6'- 0" radii are the typical standards. However, 4'- 5 1/2" radius and 6'- 6" radius allow tight turns and broad sweeping turns, respectively.
Ideally, the entire track system will use only one radius selection. It is however, possible to use different radii in problem areas and to use custom cut curves to return to the desired radius, via a serpentine arrangement.
In addition, note that the switches should be 45' to form half of the 90' turn (a curve, another one-way, two-way or three-way switch) would complete a 90' turn. Two pieces and one splice should accomplish a right angle turn.
The most durable "wheel friendly" switch lever assembly used in the industry is manganese bronze, an extremely copper-rich alloy. This alloy has tensile strength of 70,000 pounds per square inch, a degree of plasticity, high resistance to salt and fresh water, oil and steam, and is used extensively by the Navy for composition castings requiring great strength (prop hubs and blades for example).
In essence, the switch area is one of the most critical areas of the Cast Iron Track System; equal in importance to proper wheels and wheel diameter.
The switch itself must contain the ability to handle impact loading, both radially and dynamically, concentrated centrifugal loading forces, and wear at a rate that will protect the imbedded track. The switch area, as well as the switch lever itself, are precision engineered components, integral with the overall design of the system.
Direction changes of a dolly, loaded with a full paper roll, obviously generate the greatest forces on any system, thus the area where the switch lever is located is the most subject to wear. By absorbing the shock loading via a component (switch lever), which is easily field replaced, protection of the imbedded track system is accomplished.
A close examination will reveal that as the wheel travels through the switch (turn) all contact with the most critical part of the track is eliminated. The forces are transferred to the switch lever. A depression pocket in the track casting creates a void preventing wheel contact with the casting.
The precision designed switch lever, properly maintained and replaced when worn, will virtually eliminate any damage to this critical portion of the track.
Switch lever replacement is dictated by observing casting and lever wear, depending on usage, a ten year to 25 year life span can be expected.
A) Raised transition allows wheels to ride on flange, the 7" wheel riding surface is lifted clear of track impact points, transition should be 9/16" deep, examine for wear with a straight edge and rule.
B) Typical track wear location (centrifugally loaded sides of track wall).
C) Splice plates should be pre-installed and hardware included to reduce field labor (field welding and grinding is an antiquated, labor intensive, track connecting method).
D) Pre-drilled and countersunk bolt holes are necessary to reduce installation time.
E) Manganese Bronze lever assembly (replacement part).
F) Casting ends should be machined for a precise flush joint.
G) Impact points - 5 total per One-Way Switch
4 total per Two-Way Switch
12 total per Three-Way Switch
H) Casting depression which eliminates wheel contact on track.
* Inspect raised transition and impact points. Field modify raised transition to original 9/16" depth when transition wears to below 11/16" or damage will occur to impact points. See Drawing Note "A".
* Inspect Manganese Bronze switch lever for wear, also observe switch lever trench bottom, wheels should not contact trench bottom.
* Inspect outside curve track wall where wheels contact track with centrifugally generated forces.
* Accelerated wear on the switch lever and outside wall is usually attributable to bad wheels.
* Wheels, levers, and raised transitions are simple but basic maintenance items and extremely simple to repair without specialized labor.
* PROTECT YOUR IMBEDDED TRACK.
* The wearing process will progress so slowly that it will probably occur after your existing maintenance supervisor retires. It is therefore imperative this information is handed down to future maintenance personnel.
A) When using the "switch system" of track design (versus "turntable system"), wheel diameter is crucial. The 7" wheel diameter is inherent to the standard switch design. As the wheel moves over the raised transition areas, not only should the wheel raise clear of impact points, the wheel diameter must be large enough to straddle the intersection gap or damage will occur at the impact points.
B) Switch levers, manufactured of steel or not precision cast to the exact track curvature will act as a whetstone on cast iron wheels. These "sharpened" wheels will in-turn "mill" your imbedded track, significantly reducing its life expectancy.
C) Steel wheels on a cast iron track will accelerate the wear of the imbedded track. The inherent system design is to have the wheels wear instead of the imbedded track, since wheels are easily replaced.
© 2001 Capital Track Co.