Cantilever Rack Components
How to Order - Cantilever Racking
Divide the total weight by the number of arms required. Example: with a load weight of 6,000 lbs. on 3 arms, each arm needs a capacity of at least 2,000 lbs. (6,000 divided by 3).
Stacking Height and Vertical Arm Spacing
- Height to ceiling: Measure distance from floor to ceiling and subtract 10" clearance (subtract 18" clearance where ceiling sprinklers are present). Consult building codes in your area for exact clearance required.
- Allow for equipment capabilities: When usable floor-to-ceiling space exceeds equipment lift heights, determine maximum equipment lift height and subtract 6" margin. Add the height of top level load for revisedstacking weight.
- Number of load levels: For loads of consistent size, determine height of one load plus 10" for arm clearance. Divide that stacking height by dimension above to determine number of possible load levels.
Horizontal Arm Spacing
When figuring the length of a load, allow for clearance between loads; 8 to 10 inches is a good rule of thumb for long loads. Check rack arm spacing with fork arm spacing on handling equipment for safe working clearances.
- Arm spacing is determined by degree of load deflection between arms, which is dependent on rigidity of load. For safe loads with two-arm support, distance between arms should be 1/2 the load length. Three-arm support should be 1/3 the load length.
- You can perform on-site tests by setting required load on two 2x4's on floor at maximum arm spacing (96") and reduce spacing in 24" increments to arrive at an acceptable sag tolerance. If necessary, add more 2x4's to accomplish this. Loose loads have a tendency to sag more than bundled loads.
Designing a Cantilever Rack System
The key to a successful cantilever rack system is the answer to one question: What is the product (load) being stored? The answer must include the length, depth, height and weight of the product. Once this data is ascertained it becomes a simple matter to determine the required arms, uprights and braces.
A. Determine the Number and Spacing of Arms
The load must be supported by enough arms to prevent load deflection. Deflection may cause damage to the load being stored as well as the arms (figure A1). To detect deflection, place the load over two wooden blocks (to represent cantilever arms) as shown in figure A2. If deflection is not present it is acceptable to use a two arm system as long as this does not create an overload condition. If the load shows deflection use three blocks as shown in figure A3 or four blocks as in figure A4.
IMPORTANT: The load should overhang the end arms by one-half the distance from upright centerline to upright centerline. Failure to observe this measure may cause an overload condition on the arms.
B. Determine the Length of the Arms
The depth of the load should never exceed the length of the arm. A 48" wide bundle of plywood requires a 48" long arm, bundles of steel 24" wide require a 24" arm and so on. Rated arm capacities may be seriously diminished if proper loading techniques are not observed. Figure B1, B2 and B3 illustrate correct and incorrect arm loading.
NOTE: All arm capacities are based on an evenly distributed load as in figures B4 and B5 below.
C. Determine the Height of the Upright
When determining the height of the upright it is important to consider the ceiling height, forklift reach, sprinkler systems and other factors, such as a local building codes that might affect the overall height.
The height of the upright in figure C1 is determined by adding the base height, the number of loads to be stored, the arm thickness plus 6" clearance between the load and next arm. Contact our sales professionals for various rack dimensions such as base height and arm thickness.
IMPORTANT: The load placed on the base does not diminish the rated capacity of the upright. Thus, the heaviest loads should be placed on the base.
D. Determine Arm and Upright Capacities
As previously discussed, each arm supports an equal amount of the load's weight. By determining the number of arms per level and dividing it into the weight per level, the required arm capacity can be determined (see example at right).
To determine the required capacity of each upright, multiply the number of arms per side by the load on each arm. In figure D1, each aram holds 2500 lbs. Twelve arms per side times 2500 lbs. per arm equals 30,000 lbs., which when divided by three uprights, results in a required minimum capacity of 10,000 lbs. per upright.
The correct upright can be selected by matching the minimum upright capacity of 10,000 lbs. with the upright capacities set forth on the product pages. Assuming a 48" arm, the U1061-NS with 10,200 lbs. capacity and the U1061 with 12,600 lbs. capacity are the only uprights that will handle the load. NOTE: The Series 1000 MU1057 has only 3100 lbs. capacity while the Series 2000 2U1062 has 8600 lbs. capacity.
The proper 48" arm (requiring 2500 lbs. of capacity) would be either the XHDSA48 at 2500 lbs. or the XHDSA483M at 3000 lbs. capacity.
NOTE: Total arm capacity must never exceed total upright capacity.
E. Determine Brace Length
Brace length is defined as the horizontal distance from centerline of upright to centerline of the next upright.