How to read the load and reach chart of an aerial lift

With boom lifts, that is articulating and telescopic boom lifts (cherry pickers, aerial work platforms, MEWPs), working height alone is not enough to judge whether the machine will reach where you need it. Two things from the catalogue data sheet are key: the range of motion chart (the reach chart) and the dimensions table. They show how far sideways and upwards the platform reaches, and with what platform capacity. Below we explain how to read them.

The range of motion chart: what it shows

The range of motion chart is a side view of the machine drawn on a grid: the vertical axis is height, and the horizontal axis is the distance from the slew axis (horizontal outreach). The shaded area (the working envelope) shows all the points that the platform can reach. The edges of the area are the extreme positions of the boom.

• The highest point of the envelope = the maximum working height (platform vertically at the top).
• The furthest point to the right = the maximum horizontal outreach (how far “sideways” you can reach, for example over an obstacle).
• The zero point (0 m / 0 m) is usually the slew axis of the machine: distances are measured from it, not from the edge of the chassis.

Why does platform capacity fall with distance?

The chart often shows two or three zones marked with different platform capacities, for example 454 kg / 300 kg / 230 kg. This is not a mistake: the further out and the higher the boom is extended, the lower the permitted weight in the platform. This comes from the moment (a longer arm means a greater load on the structure and lower stability). That is why full platform capacity usually applies in the zone closer to the machine, and at maximum outreach the capacity is lowest.

The practical conclusion: if you plan for two people with tools to work at a large horizontal outreach, check that your weight fits within the zone for that reach, and not only within the maximum platform capacity quoted as a headline figure.

Horizontal outreach (up-and-over reach): the most important with obstacles

Horizontal outreach is the distance the platform reaches horizontally from the machine. It is decisive when you cannot drive directly under the point of work and have to “jump” over an obstacle (a machine, an excavation, a row of racking, the roof of a shelter). Articulating boom lifts usually have better “up-and-over” reach than telescopic boom lifts, which in turn reach further in a straight line. On the range of motion chart you can see this on articulating boom lifts as a characteristic “indentation” in the envelope near the base (room for the obstacle).

The dimensions table (letters A–J): what they mean

Next to the chart on the catalogue data sheet there is a drawing of the machine with letters and a table of their values. The letters refer to specific dimensions on the drawing. On boom lifts you will most often come across:

• A: length of the machine in the stowed (transport) position,
• B: width in the stowed position,
• C: height in the stowed position (important for gates and entrances),
• D, E: length and width of the platform,
• F: wheelbase,
• G: ground clearance under the machine.

On scissor lifts the letters describe, among other things, the height of the platform lowered and raised, the platform dimensions, the length and width of the machine, the wheelbase and the ground clearance. These dimensions decide whether the machine will go through a door, fit in a goods lift and travel along a paved access road.

What to look at when choosing a machine

• Working height: remember the “+2 m” rule (a person works about 2 m above the platform floor). There is more in the article on choosing the working height.
• Horizontal outreach at the point where you will really be working, not only the maximum value.
• Platform capacity in the given zone: whether it holds the people, tools and material at the planned reach.
• Transport dimensions (A, B, C): for gates, entrances, lifts and the access road to the site.
• Ground and outriggers: terrain or floor, and whether self-levelling outriggers are needed (on rough terrain machines).

Don't want to analyse charts? We will do it for you

On the machine pages on our website you will find dimension drawings and range of motion charts, and for most models a table of dimensions. If you would rather have a ready-made selection, describe the job to us (height, sideways reach, weight in the platform, ground, access) and we will choose a machine that really reaches where it needs to, and prepare a quote.