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Patented Track vs. I-Beam or Wide Flange

In the early history of material handling for monorails and under-hung cranes, structural I-beams (also known as S- beams) and nowadays wide flanges, were used as runway track and bridge girders. Structural members are designed and rolled for use as structural members; not cranes, monorails or runways. Because the requirements of material handling are vastly different than those for structural, patented rail sections were designed and manufactured specifically for that purpose. John Maye Associates provides patented rail systems from ACCO under the Louden and Trambeam brand names.

Today, many in the material handling industry are not aware of the advantages of patented track. Because of this, the major advantages of patented track and comparisons between it and structural members are discussed in greater detail below:

The Basics:

I-beams or structural members are engineered and chosen based on the load bearing or wheel load needed to support the crane, which means the size of the member along with the lower flange varies as well. Trolleys or end trucks that run on the lower flange have to adjust to this change in width and size.

Patented rail is similar in that it is also engineered and chosen based on the load bearing and wheel loads needed to support the crane, but the one constant is the lower running flange. The lower flange is always the same width; 3-1/4” or 3.33”, which allows for uniformity in end truck or trolley selection.

There are 2 different lower running flange thicknesses associated with patented track (typically 7/16” and 11/16”), classified as “standard” patented track and “heavy duty” patented track. This rarely changes the wheel or end truck selection though. And unlike I-beams, the flange on patented track is flat, straight and true without camber or sweep.

Material composition and manufacturing comparisons:

S or I-beam structural members are made of a mild steel with a tapered flange for a running surface. It is rolled with a normal maximum of .45 carbon. The tapered flange, together with a necessarily contoured wheel, results in a point of contact for the carrier and crane wheels at a comparatively thin point of the flange. Additionally, the taper causes the wheels to try and run down the slope, creating a wiping action between the wheels and the running flange.

Wide flange structural members are manufactured and rolled similarly to I-beam, but have a flat flange not a tapered flange like the I-beam. Because of this, the lower flanges of a wide flange beam are often weaker in their wheel load and load bearing capabilities. The result is that in order to off-set the lower flange loading capabilities, excessively heavy wide flange members must be chosen. This adds cost and additional dead loads to support members or buildings. These large, wide members guarantee that the wheels of the carrier or trolley will ride at the far edges of the flange, causing peening to occur. When using wide flanges for runways, caution must be used to verify both beam span maximum loading and lower flange loading.

Patented rail on the other hand, has a high carbon, high manganese, precision rolled lower ‘T’ section with a flat flange and equal thickness throughout. The lower flange steel has a content of .55 - .65 carbon and .60 - .90 manganese. Hardness as rolled is 225 Brinell minimum. The two flat surfaces on which the carrier wheels roll are in the same horizontal plane, assuring maximum contact for the wheel treads. Wheel contact with this rail continues to cold roll the surface, hardening it so that the smooth surface is continually improved. The result is maximum life without peening and minimum wear due to flanging.

Basic Shapes: Patented Track, Wide Flange & “S” or “I” Beam-

Patented Rail, Wide Flange Beam, 'S' Beam Comparison Image

Equipment operation comparisons:

Because of the tapered flange on I-beam, the wheels of the carrier or crane must have a similarly tapered tread, or must be mounted in a slanted position. In either case, proper contact between the wheel and the beam flange is difficult to obtain. As I-beam sizes and dimensions vary, so does the angle of the taper; thus prohibiting the “one size fits all” tapered wheel on most of the standard trolleys or carriers manufactured from seating, and ultimately running properly. The result is thrust loading on bearings; skewing of wheels which in turn causes excessive wear of bearings, wheels and the rail itself; flanging of the rail; binding of carriers and cranes.

Flat tread, flanged wheels are necessary to keep the wheels running correctly on the lower flange of a wide flange. The loose tolerances permitted in the rolling of structural members allows for uneven lower flange dimensions and straightness; creating premature wheel and flange wear and failure.

Patented rail with a smooth and flat running surface permits mounting wheels in a vertical position with the thread in a horizontal plane. When coupled with associated carriers designed for patented track, it greatly reduces thrust loadings on bearings. Carriers with swiveling heads eliminate the skewing of wheels, binding of carrier or crane wheels, and flanging of the rail.

Because of patented track’s popularity and longevity, many manufacturers of enclosed track crane systems provide end trucks that can operate on patented track. This allows the hybridization of crane systems where the bridge may be one type of enclosed track, but the runways are of patented track design. In many instances, this allows more cranes to operate on a patented track runway system due to its greater load bearing strength at like spans. With patented tracks greater load bearing capabilities it also allows for longer runway support centers. This manifests itself in less support columns allowing for maximum use of floor space and reducing cost.

With patented rail, there are ergonomic benefits for the operator as well. The close tolerances of patented track along with the flat, smooth running surface result in minimum effort required to move a load; it is estimated that it takes half the effort to move a load on patented track than with structural members.

Design flexibility and installation simplification:

Structural members are limited to straight runs or monorail systems only; no switches, curves, transfer sections or latches. Expansion can be troublesome; the various flange types, widths and thicknesses will require different trolley types or sizes.

The relatively “loose” manufacturing tolerances of structural members make it difficult to install where multiple pieces are joined and used for a continuous runway or monorail. Structural is known for having excessive camber and/or sweep, all of which are considered within spec when milled. Camber is a “bend” or “bow” in the rail along the horizontal axis. Sweep is unevenness or curving of the piece. One can imagine how difficult mating or attaching members that exhibit these types of issues might be. As stated at the beginning of this article, structural members were not really designed for material handling applications.

Patented track rail sections on the other hand have much tighter dimensional tolerances; and with the common lower flange shapes and size allow for easy mating of track sections at install. The lower flange of patented rail hardens and improves over time, allowing sections of rail that are in good condition to be re-used at other locations within a facility again and again.

In addition, components such as switches, curves and transfers can be easily added later to allow for material flow changes or expansion. One type trolley can be used for the whole system, no need for tapered and flat tread trolleys on the same system.
New patented track systems include pre-engineered hangers, hanger rods, splice plates, end stops, etc. No need to design and fabricate different items for the different size structural members at each installation.

John Maye Associates of Wisconsin has sold and serviced hundreds of patented track crane & monorail systems for over 50 years. Please contact us at 262-542-0026 or Contactu Us to help determine if patented rail is the right choice for you.

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