Designing trolleys

Trolley push effort

Occupational Health & Safety experts* recommend the following safety suggestions:

Push efforts for trolleys, beds and mobile equipment:

• 167 - 216N (17 - 21kg) (37.5 - 46.2lb) initial force, and

• 60 - 120N (6 - 12kg) (13.2 - 26.4lb) sustained force for infrequent, short distances.

Spring scales are a simple, accurate way to measure push effort. They are very cheap to buy and are available from most hardware stores. Simply clip the hook of the scale and pull until the trolley begins to move. If it takes less than 17kg (37.4lb) to get the trolley moving and less than 6kg (13.2lb) to keep it moving, then the trolley design and work load are best-practice.

Most trolleys actually measured in surveys of hospitals* were only within these recommendations if lightly loaded and used on smooth, hard floors. Often, as the trolleys were more heavily loaded up to their design capacity, they exceeded these recommendations, often doubling, and sometimes needing six times the recommended force. For example, simply moving from a hard, smooth floor to a carpeted area could more than double the force required.

Trolley design fundamentals

A trolley should be:

NOT TOO WIDE:
Hand pushed trolleys should be at least 80mm (33/16”) narrower than the narrowest doorway. Towed trolleys should be 500mm (17/8”) narrower than the narrowest isle or doorway, and more if towed in a train.

NOT TOO LONG:
Trolley length should be between 1.5 to 2 times the width, otherwise it will not track smoothly around corners. If it must be long, you may need to experiment to find the best castor arrangement to suit your particular needs.

NOT TOO HIGH:
A maximum height of 1400mm (4’7”) is recommended (including the goods being carried) to enable a clear line of sight.

NOT TOO LIGHT:
As a rough guide, the weight of the trolley is usually 15% to 20% of the load it is to carry. For the castor to function properly, the frame of the trolley must be strong enough to hold the castor head truly vertical so it can swivel freely (that is, the mounting plate must remain horizontal, or the stem must remain vertical), and the frame must not bend under the impacts that inevitably occur. The most common cause of castors not tracking properly is that the mounting has twisted off square.

NOT TOO HEAVY:
It is often safer, and more efficient, to divide the heavy load over a number of trolleys rather than concentrating it into one. Trolleys which are too heavy to move conveniently remain unused, or people suffer back injuries.

Handle height & position

Optimal handle height for ‘average’ females is 910mm (3’) Optimal handle height for ‘average’ males is 990mm (3’)
A good compromise handle height for mixed users is 950mm (3’11/2”).

If a trolley is to be pulled (and most are at some time), the handle should be located far enough out from the trolley to ensure feet do not hit the trolley (approx. 400mm (1’3”)). This can be closer if the trolley has no shelves or tubes below 350mm (1’33/4”)

Large wheels are easier to push

In addition to wheel diameter and tyre hardness/resilience the following design factors should be considered:

The most common mistake when fitting castors is to fit wheel diameters too small for the real needs of the trolley and its user. The surveys, both in Australia and overseas, show again and again that small castors which get caught in uneven floors, ridges, gaps and holes, cause many injuries. Large diameter wheels, as against small wheels, will often add less than 10% to the cost of the trolley, and yet make that trolley 500% easier to use.

The guideline is for a minimum diameter of:
• 125mm (5”) for non-patient trolleys
• 175mm (7”) for patient trolleys used indoors
• 200mm (8”) for trolleys used out doors or for loads over 200kg (485lb)

Smaller castors can still be used in restricted circumstances, for instance, use on lightweight equipment.

In general, castors of:

• 100mm (4”) size are recommended up to 120kg (265lb) trolley loads, but ony on smooth floors and for short distances. They can be used on ward furniture, but not on catering equipment.

• 75mm (3”) are even more restricted, being recommended only up to 100kg (220lb) trolley loads and again only on smooth floors without obstructions for short distances.

• 50mm (2”) are recommended only up to 80kg (175lb) trolley loads and for very short distances. If used on carpets a maximum load of 50kg (110lb) is appropriate.