Frames are available as structural members or roll formed members. Roll formed channels start out at our plant as flat coil stock and are fed through a series of rolls that form it into a channel. This channel continues through a series of machines that punch holes in the web and flanges and is finally sheared off in standard 10'-0" lengths. As a result, roll formed channels such as AR, CR, PR, and QR have a set pattern for axle holes and flange punching. The hex axle punching is on 1-1/2" centers, the bottom flange punching is on 1-1/2" centers and the top flange punching is a 12" repeating pattern.
The multiple punching for AR, CR, PR, and QR rails serves several purposes.
1. Versatility for future applications. If the initial application requires roller centers of 6" and a later application requires 3" or 4-1/2" centers, the same equipment could be reused by adding additional rollers in the available pre-punched axle holes.
2. Allows for placement of supports and accessories anywhere along the underside for the conveyor.
3. Allows for attachment of guards anywhere along the top side of the conveyor without interfering with the roller axles.
M.S. CENTER RAILS - Elements of Sections
Code Size Area Axis 1-1
I S
The above values take into consideration the reduction in capacity of frame rails caused by standard web and flange punching. They are based on a uniformly distributed load between supports with the load equally shared by both rails.
There are two methods generally used to calculate the capacity of two rail frames: deflection and stress. The frame capacity is normally limited by the allowable working stress unless the deflection affects product conveyablility. The stress method is used for level lines and the lowest of the stress method and deflection method capacities is used for the graded lines.
Maximum Allowable Deflection = ∆
CALCULATING FRAME CAPACITIES
Type Symbol Dimensions
For Two Rails
Allowable Stress
Frame Capacity #/ft.
Net
10’-0” Between Supports
1467 366 244
J 5” at 6.7# 4.474 11.184 2385 596 496
K 6” at 8.2# 6.752 20.258 3601 900 900
L 7” at 9.8# 8.678 30.374 4628 1157 1157
Structural
Therefore the maximum allowable deflection for frames with supports on 5'-0" centers is .167". The maximum allowable deflection for frames with supports on 10'-0" centers is .333"
Where:
W = Total Frame Capacity (lbs./ft.)
∆ = Deflection at the Center of the Span (inches) 5'-0" Support Centers = .167
10'-0" Support Centers = .333"
E = Modulus of Elasticity (PSI), 10 x 106 for Aluminum 30 x 106 for Steel
I = Net Moment of Inertia for two rails, with Allowance for Axle and Bolt Holes (inches4) See Above for Values
L = Distance Between Supports (inches)
f = Allowable Working Stress (PSI) See Above for Values
S = Net Section Modulus for Two Rails, with Allowance for Axle and Bolt Holes (inches3)
In order to simplify frame selection, standard roller and frame combinations are available that offer compatibility in size and capacity. Having determined the roller size and spacing, check the capacity of the standard frame rail that is offered with that roller. You need to add the total load on the conveyor at the worst loading condition (live load) plus the weight of the rollers and frames and compare that with the frame capacity. Since the standard length of most conveyor sections is 10'-0", the capacities are given for that length so supports can be placed at the section splice or joint whenever possible. If additional capacity is required, it may be necessary to provide supports on 5'-0" centers.
A comparison should be made to see if it is more economical to select a larger and stronger frame and support it on 10'-0" centers or select a smaller frame with less capacity and put the supports on 5'-0"
centers. If your choice is more supports, don’t forget the increase in installation costs for those supports, i.e. drilling anchor holes, adjusting the height, attaching to the conveyor section, etc.
In reviewing the frame capacities in this catalog you will see that there are capacities listed for supports on 10'-0" centers and 5'-0" centers. There are also different capacities for level conveyors and graded conveyors.
1. Normally the limiting factor for frame capacity for graded gravity lines is deflection or sagging of the frame. The support centers are important because the farther apart the supports, the greater the sag for the same load. Therefore, the capacities for 5'-0" centers are always greater then for 10'-0" centers.
2. The reason the capacities for level conveyors are greater than for graded conveyors is that for a level line the only way the product will move is if it is being pushed. Therefore, if physical force is required, a greater sag in the frames can be tolerated. For graded conveyor, we are depending on the force of gravity to move product forward on a decline unit. If a graded conveyor was loaded to the same capacity as a level unit, the sag may be so great that at certain points along the con-veyor, a stopped carton would not be able to restart by its own weight.
The method of loading may be a factor in determining frame rail size. Generally, the conveyor loading point will require more frame capacity because of possible impact or abuse from the loading mechanisms such as fork trucks.
( )A W 384( )∆ El x12 5 x L4
--- Deflection Method( )
=
( )B W 96 x f x S L2
--- Stress Method( )
=
Couplings
There are several methods of attaching one conveyor section to another. Due to design criteria, all types of couplings are not available on all sizes and styles of roller conveyor. Mathews has pre-selected couplings for all units and optional couplings are also identified.