Rolling ResistanceRolling resistance determines the effort necessary to move the equipment from rest and to keep it rolling. If a wheel, so hard that it will not flatten under load, rolls on an absolutely flat hard surface, perfect rolling is possible. The nearer you get to this ideal, the lower the rolling resistance becomes.
In view of this, the first choice should be hard tread wheels but the average floor is far from smooth and clean and is often littered with small particles of some description.
Once the wheels are rolling they will pass over these small items with no problem, but if the equipment starts from rest with minor obstructions, such as swarf, in front of the wheels then the starting effort includes that necessary to lift the equipment to the height of the obstructions. In cases where hard wheels are used on soft floors such as carpeting, or even asphalt, the surface deformation causes the wheels to sit in small ruts and extra effort is needed to overcome such resistance. Resilient wheels move more easily over obstructions as they deform and roll over them instead of climbing. On the other hand, as a tyre flattens under load, an area instead of a line is always in contact with the floor and resistance to rolling is greater.
Individual characteristics of our wheels will be found elsewhere in this catalogue but, because of the wide variations in floor conditions, hardnesses, wheel diameters, tread profiles, etc., it is not practical to give rolling resistance figures in the tables. We will always be pleased to advise when given the necessary information, but the only accurate assessment is one based on the user making his own tests.
We do not give load capacities for ‘ideal working conditions’ as these rarely exist. Capacities given in this catalogue are based on normal working conditions on reasonably level floors free from grooves, breaks, door sills, lift entrances and other hazards. They are also based on a maximum speed of 4km/h unless
weight of transport equipment + load
For uneven floors, this should be divided by three as, often, only three wheels have contact with the floor on a 4-wheel trolley.
Castor and Wheel Lubrication
We recommend regular greasing of all nipples with a lithium based grease of the type used on car axles. Where nipples are not provided a few drops of light machine oil should be used.
Revvo’s standard finish for pressed steel castors is bright zinc electro-plating to BS1706. Wheels and fabricated castors are paint sprayed to a high finish. Other finishes can be supplied to special order, subject to economical batches.
Castor and Wheel Selection
The following factors all have a bearing on which wheel or castor is suitable for a particular application, including the performance to be expected.
Apart from the gross weight of the load and equipment, an allowance should be made for uneven distribution of weight as this often results in one wheel carrying more than the rest. Mechanical towing can also impose severe shock loading.
Rough uneven floors often go unnoticed but they cause severe overloading in some cases simply because one wheel leaves the ground and the load is thrust upon the remainder. Impact loads due to kerbs and holes in the floor also cause problems.
If a truck moved by hand meets an obstruction, it becomes harder to push and the truck slows down, takes an easier route, or the load is reduced. All these reduce the strain on the castors as well as the person pushing. This does not happen with mechanical towing as there is usually plenty of power in hand; This, combined with higher speed, results in considerably more castor stress.
All metal wheels will damage floors if the load is heavy. Resilient wheels are not so easy to move but they are certainly kinder to floors. It should be remembered that the floor will cost more to repair than the price of the wheel running on it.
Designed to steady the equipment to which they are fitted and stop horizontal movement, floor locks are never intended to act as a jack. Any attempt to vary the fitting height from the catalogue specification will give failure and/or damage. There is some built-in resilience in the foot pad, which will allow some variations in floor level. Nonetheless it is essential that the floor lock is fitted as closely as possible to one of the swivel castors. Please note that the floor lock can be severely damaged if the linkage is operated whilst the trolley is moving.
Castors and wheels are usually fitted to equipment that is used intermittently and is often stationary for much of the time. Revvo’s products are specifically designed to operate well under such conditions.
Health And Safety at work - 1974
Revvo endeavours to ensure that all its products are safe and without risk to health when they are adequately maintained and properly used according to the recommendations in this catalogue. Specific guidance is given in the notes on this page and elsewhere in this catalogue, where appropriate. We will always be pleased to advise on any application put before us.
Definitions and Uses - Swivel Castors
In swivel castors, the wheel and fork can rotate through a full 360 degrees, whilst the top or mounting plate remains in a fixed position. The horizontal distance between the centreline of the swivel and the centreline of the wheel is called the offset. When pressure is applied through the mounting plate, the offset causes the castor to swivel in line so that the wheel always trails in the opposite direction to the way in which the equipment is being moved.
Our tables give the swivel radius dimension for all swivel castors. This shows the mounting clearance required to allow the castor to swivel without obstruction.
Fixed castors have the top plate rigidly fastened to the fork legs with the wheel in line with the fixing bolt holes. These castors do not swivel at all and the wheel can only move in two directions, forwards and backwards.
Swivel Head Seals
Swivel head seals are fitted as standard to scaffold castors and all 5,H,P,X,Y and Z series castors. They are optional on the 3 and 4 series.
Adjustment of tapered roller bearings
All castor bearings are correctly adjusted when the castor is built and should require no attention other than greasing, and then only when they are subjected to particularly arduous conditions.
2 Swivel Castors and 2 Fixed Castors
Providing good load capacity and manoeuvrability, this combination ensures accurate steering, even on long straight runs, making it the most practical combination for industrial use. Any trolley with this castor combination should be pushed with the fixed castors leading.
4 Swivel Castors
As this combination gives good load capacity with exceptional manoeuvrability, it is suitable for winding runs and where sideways action is required. It is not recommended for straight runs or ramps, as it may be hard
1 Swivel Castor and 2 Fixed Castors
This combination provides an economical solution for lightly loaded trolleys requiring good manoeuvrability. The trolley must be reasonably small in size and any load must be evenly distributed to ensure stability.
3 Swivel Castors
This provides good load capacity with excellent manoeuvrability. However, equipment with this arrangement will
4 Swivel Castors and 2 Fixed Castors
2 Swivel Castors and 2 Fixed Castors
Wheels for applications other than castors
Chemical resistance of wheels
The extensive range of Revvo wheels have resistance to certain chemicals and oils. Please contact us for further information, if you have any queries.
Standards and Codes
BS.EN. ISO9000 Quality management and systems