How to choose the right wheel support and calculate its carrying capacity
Purpose of wheel mechanisms
The main factor that you need to pay attention to when selecting a wheel base is the compliance of the device parameters with the expected weight, mechanical, chemical and temperature loads, as well as the suitability of the mobile structure for its purpose:
household needs - coffee tables, bedside tables, bookcases;
commercial and general use - supermarket trolleys, office chairs, hospital beds, medical or culinary shelves;
manufacturing and industrial sectors - waste containers, mobile scaffolding, hydraulic forklifts.
The suitability of the caster for the conditions of its application will minimize the occurrence of malfunctions and significantly increase the efficiency of the transport equipment.
Attention! Violation of the operating rules: exceeding the load and speed limit, ignoring the activated brake systems or foreign objects caught in the wheel rim can damage the device and endanger personnel and visitors.
Steps for selecting wheel bases
When a complete understanding of the purpose of the mobile mechanism, the condition and characteristics of the working surface has been drawn up, and the operating conditions of the equipment have been analyzed, you can proceed to the four main stages of the selection of the wheel support:
determination of the type, material and design features of the wheel, which will correspond to the floor surface, temperature regime, indicators of humidity and aggressiveness of the environment;
the choice of support and mountings that ensure intensive work and equipment maneuverability;
calculating the possible load on one support mechanism and on the entire system as a whole;
checking the performance of the structure.
For the reliability of the wheel support, it is important to complete all the above steps, so we will try to disassemble each item in more detail.
Wheel bearings for various purposes
The usual furniture casters that are installed on office chairs are often set on the axis of rotation itself, which is quite acceptable for small weight loads. For bogies moving massive and oversized loads, wheels are used, the design of which includes bearings of one of three types:
plain bearings are the simplest and most affordable products. They withstand well any mechanical stress and are resistant to corrosive processes. Suitable for hardware wheel bases, transport equipment and heat-resistant cast iron or aluminum models. Such parts need regular lubrication by means of a special nipple;
roller bearings - composed of steel rods (treated with long-lasting grease) fixed in a plastic housing. This modification is used in trolleys intended for transport operations;
precision ball bearings are a set of hardened steel balls fixed in a cage. This is the most lifting type of product, resistant to any negative impact. Ball bearings are often used for large diameter wheels.
A reliable bearing will improve the running characteristics of the bearings, slow down wear on the wheel mechanism and extend the life of the mobile device.
Important! The quality of the contact layer of the wheel (tire) is of great importance during the operation of wheel bearings. For its manufacture, ordinary or thermoplastic rubber, polyurethane, polyamide or polypropylene are used. The material for the shank should interact well with the working surface of the floor.
Types of bases and methods of their fastening
Depending on the mobility required by the mobile equipment, one of two types of wheel support maneuverability is selected:
fixed - cannot rotate around the axis and move only in one specified direction;
swivel - they turn in any direction and are easily controlled in the direction of travel, sometimes they are equipped with a brake mechanism.
The most common way to attach both fixed and swivel models to the base of the cart is to use a special panel. Swivel feet can also be mounted using a special rod or mounting hole.
Note! There are several wheel support combinations, each suited to a specific load and bogie maneuverability. To increase stability and controllability of the device, rotary and fixed models can be used in the same design.
Calculation of the lifting capacity of the wheel bearings
One of the key factors in determining the correct wheel type is calculating the load on the wheel support. The maximum load capacity indicated in the product passport implies a flat floor surface, a speed of less than 4 km / h, obstacles up to 5% of the wheel height, and an air temperature of +20 ° C. Under these ideal conditions, the load is evenly distributed across all four wheel bases. Any deviation from the standard leads to a decrease in carrying capacity, therefore one wheel is excluded from the generally accepted formula:
X = (M + m) / (n-1),
X is the load on one wheel;
M is the mass of the cargo;
m is the weight of the structure;
n is the number of wheels.
This formula is used when transporting solid goods, and when liquids are transported, one more support is taken away from the total number of wheels, thus (n-2) is indicated in the denominator.
Testing of finished products
The enterprise necessarily conducts testing of finished products. The standard list of tests includes:
static test - long-term presence of supports under a load exceeding the maximum;
dynamic test - passing the lane "with obstacles";
anti-corrosion diagnostics - prolonged stay in a humid environment;
temperature test - carried out specifically for heat-resistant wheels.
Such a responsible approach of the manufacturing company excludes unjustified equipment breakdowns and ensures a long service life of the wheel bearings. You can choose the wheels in our catalog.