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JA Mobile Glass Rack Engineering Note
A larger wheel can make a mobile A-frame rack easier to roll over obstacles—but it also raises the rack and its load. For a loaded glass storage rack, stability must be checked before clearance.
When a factory is choosing a mobile glass storage rack with casters, “bigger wheels” sounds like the safer answer. A 200 mm wheel appears to offer more clearance and easier movement over small floor imperfections. But the wheel lifts the entire rack. The load rises with it, the center of gravity moves upward, and a push, turn, floor joint, or slope can create more tipping leverage. In practical terms, the wheel improves passage height—not the basic stability of the loaded rack.
That was the key discussion in project 14427 for a Mgrack double-sided A-frame panel storage trolley. The project configuration was 1500 × 1100 × 1903 mm including the wheels, with a stated 2-ton capacity, two 6-inch swivel brake casters and two 6-inch fixed casters. The customer initially requested Ø200 mm wheels. We recommended 6-inch wheels, approximately Ø150 mm, because the operating priority was to keep the center of gravity lower while retaining a workable factory trolley layout. This Ø150 choice belongs to that project configuration; it is not a universal Mgrack wheel standard.
Why the 200 mm request became a 6-inch recommendation
A mobile glass storage rack has two competing requirements: it must roll, and it must stay controlled while loaded. Increasing wheel diameter can help when the rack must cross a large threshold or rough transition, but it also increases the clearance between the floor and the rack base. On an A-frame rack carrying high, fragile panels, that added height is not a free upgrade. It can increase the overturning effect during steering and make braking feel less settled. For the 14427 design, the selected arrangement used two swivel casters with brakes for steering and parking control, plus two fixed casters for directional tracking. It was a project-specific balance between mobility, braking, and a lower overall center of gravity—not a claim that every job should use Ø150 mm wheels.
The four 30 mm support legs are a backup, not an anti-tip certification
Project 14427 also included four bottom support legs positioned approximately 30 mm above the floor during normal caster operation. Their purpose is easy to misunderstand. They are not a replacement for correctly selected casters, a brake, a level floor, or a secured load. They are a mechanical fallback: if a caster is damaged or loses its normal working position, the nearby support leg can contact the floor sooner and help limit the immediate progression of a lean. That detail provides a second line of defense against a sudden loss of caster support, but it must not be described as anti-tip certification or proof that the rack cannot overturn. The rack still needs proper loading, controlled pushing, and inspection of wheels, fasteners, welds, and support legs.
When iron-core polyurethane casters fit the workshop
The 14427 project used iron-core polyurethane swivel casters. This type of wheel can be a sensible choice for indoor material handling where the concrete or coated workshop floor is reasonably smooth, clean, and free of large steps, loose debris, deep joints, or standing liquid. Polyurethane offers a practical rolling surface for routine internal movement, while the iron core supports the caster assembly. The wheel is not a license to ignore the floor. If the route includes ramps, expansion gaps, outdoor paving, trailer loading, frequent thresholds, or rough stone floors, the wheel and rack should be reviewed against those actual conditions. Caster rating was not recorded in the available project information and must be verified for the configured total load and duty cycle.
What to confirm before specifying a mobile A-frame rack
- Check the floor first: confirm flatness, thresholds, joints, debris, and the maximum slope on the actual route; a smooth indoor floor supports a different wheel decision from a ramp or rough yard.
- Confirm the movement method: is the rack pushed inside the plant, moved by forklift, or carried on a truck? A wheeled rack for internal handling needs a different review from a rack that must be restrained for road transport.
- Decide whether brakes are required: for a loaded rack that is parked, aligned, or worked around, specify the number and position of swivel brake casters; do not assume a fixed-wheel set can provide parking control.
- Send the panel size, unit weight, total load, aisle width, slope, handling equipment, and surface-protection requirement. Mgrack can then be configured around the real load path, with rubber contact protection, limit bars, tie-downs, and project-specific wheels rather than an assumed standard.