BIL Castors & Wheels Division, part of
Baz-Roll International...

MOUNTINGS FOR CASTORS
TOP PLATE – commonest fixing with four boltholes to spread the load over the swivel head of the castor.
SINGLE BOLTHOLE – limited to loads of up to 320 kg having a fastener through the centre of the swivel head. Can be fitted with either threaded stems or round/square expanding sockets to fit in tubes.

Loadings for castors
The effect of uneven floors due to cracking, joints or gullies must be allowed for when assessing the required load rating of castors. The degree of such defects will determine the extra shock loads acting on the castors.

Castor configurations – these will also effect load calculations as, when moving, one or other castors may float on uneven floors removing its share from the loading. An allowance for this must be made, and so the castor load capacities are listed below, along with the uses and characteristics of each configuration.
TWO SWIVEL + TWO FIXED CASTORS – when pushed with the two fixed castors leading, this offers the best load control with good steering on straight runs and cambers. Suitable for most loads. Castor capacity at least 33% of total gross load.
FOUR SWIVEL CASTORS – for maximum manoeuvrability. Difficult to control on straight runs, cambers and uneven surfaces, particularly with heavy loads – to overcome this fit directional locks. Castor capacity at least 33% of total gross load.
ONE SWIVEL + TWO FIXED CASTORS – for easy manoeuvrability. Suitable only for small trolleys with light loads. Stability can be a problem so loads must be distributed evenly. Castor capacity at least 40% of total gross load.
THREE SWIVEL CASTORS– for maximum manoeuvrability. Can be difficult to control on straight runs, cambers and uneven surfaces. Suitable only for small trolleys with light loads. Castor capacity at least 40% of total gross load.
FOUR SWIVEL + TWO FIXED CASTORS, CENTRALLY PIVOTING – usually used on long trolleys to optimise control and manoeuvrability. The two central fixed castors are usually one size larger, or the same size as the swivel and fitted with 25mm packing under the top plate. Castor capacity for the fixed castors at least 50% of total gross load. Swivel castor loads will vary.
TWO SWIVEL + TWO FIXED CASTORS, CENTRALLY PIVOTING– similar to the above but less stable if the load is not evenly distributed. The two central fixed castors are usually one size larger, or the same size as the swivel and fitted with 25mm packing under the top plate. Castor capacity for the fixed castors at least 50% of total gross load. Swivel castor loads will vary.

WHEELS
Castor wheels are designed to be supported on both sides and intended for use on units with manual propulsion of up to 4mph. The extra stresses of powered towing should only be considered with specialist advice. Wheels are categorised into two groups – hard tread and soft tread wheels...

Hard Tread Wheels - the easiest to push as they have least tractive resistance. The main disadvantage is that they are noisy and can wear floors excessively. The main types of hard wheels are as follows...
CAST IRON & STEEL WHEELS - combine shock resistance with long life and economy. Temperature range -40°C to +300°C Nylon wheels – has high load capacity, is light and clean and causes little floor damage. Temperature range -40°C to +80°C Polypropylene wheels – has good load capacity but not the abrasion or fracture resistance of nylon. Operational temperature range -20°C to +80°C
PHENOLIC WHEELS - very hard, abrasion and fracture resistant but liable to wear and chipping. High operational temperature range up to +350°C

Soft Tread and Pneumatic Wheels - are resilient generally resulting in less noise, marking and floor wear. Tractive resistance is however much higher. New development grades of polyurethane and rubber have increased load capacities while reducing tractive resistance... Solid rubber wheels – the basic wheel, although new thermoplastic grades are harder wearing and low cost. Temperature range -20°C to +60°C
ELASTIC RUBBER WHEELS – has a high load capacity and wear resistance with a smooth soft-cushioned ride. Temperature range -20°C to +60°C Polyurethane wheels – has a very high load capacity with abrasion, tear and chemical resistance and a soft ride. Temperature range -30°C to +90°C
PNEUMATIC WHEELS – has excellent shock absorption working well on rough, uneven surface like grass or gravel. Temperature range -20°C to +60°C
HIGH TEMPERATURE WHEELS - wheels now available with rubber tyres suitable for use in the temperature range -30°C to +250°C

Bearings
The choice of bearing is determined by the application, working environment and loading levels... Plain bearings – are mainly used in low load, intermittent applications. Disadvantages include axle wear and squeaking in dusty or wet conditions.
ROLLER BEARINGS – are simple in construction, robust and excellent for regular use with light to medium loads working at low speeds. Ball journal bearings – precision construction bearings for higher loadings with moderate to high radial forces. Suitable for manual or low-speed powered towing.
TAPER ROLLER BEARINGS – are mainly used with larger diameter castors for the highest loads and most arduous applications including towing.
SINTERED BRONZE - or other metals, are a type of plain bearing used for high temperature applications to minimise friction and wear. Teflon sleeve – are another type of plain bearing used to reduce friction but generally used on lighter loads than sintered bronze.