Guidance relating to use of Spreadsheet for calculating pad-size requirements
Overview
The spreadsheet is intended to assist users in determining minimum stabiliser foot/pad size
requirements, based on a calculation of the lorry-loaders gross lifting moment (Ma) and
subsequently the forces being placed through the stabilisers.
The only cells which can be altered on this sheet relate to the essential information required for the
lorry-loader being used, in terms of capacity and critical measurements etc. in the red cells on the
right hand side; and the ground bearing capacity in the yellow bell (B:19) on the left hand side. This
is stated in kN/m², although there is a small converter also on the sheet to convert from kN/m² to
t/m² and vice-versa.
The formulas used for calculating both the loader gross lifting moment (Ma) and the forces exerted
through the stabilisers are as per the product standard BS-EN12999:2011; which have been available
on ALLMI Guidance Note 013 – Stabilizer Forces, for approximately the last two years.
The following sections provide guidance and/or a confirmation of the criteria to be entered in each
of the lorry-loader boxes on the right-hand side of the spreadsheet.
Loader Crane Data
Maximum Hydraulic Radius – this is the maximum hydraulic radius of the loader crane being used for
the lifting operation. The figure inserted in this box must be stated in metres i.e. 10.10. *
Rated Capacity @ Max Radius – this is the maximum capacity corresponding to the radius stated
above. The figure inserted in this box must be in kilogrammes i.e. 2,500 *
*Note:
it is common practice to insert the required radius and rated capacity for the specific lifting operation being planned as
opposed to the maximum, with the aim of achieving a lower figure overall for the loader cranes gross lifting moment. This
should only be done if it can be proven elsewhere within the lifting plan that suitable control measures are in place to ensure
the radius and load stated are not exceeded.
Radius of the CoG for deadweight of the Loader – this information should be obtainable from the
manufacturer’s handbook and should be based on the measurement of the Centre of Gravity for the
Loader in its “booms extended” configuration. The figure inserted in this box must be stated in
metres i.e. 3.20.
Dead Weight of the Loader Crane – this is again available from the manufacturer’s handbook or
product range brochure. The weight inserted should be for the loader only (preferably excluding
stabilisers) and not the GVW or kerb weight of the truck and loader. The value entered must be
stated in kilogrammes i.e. 2,650.
Establishing Forces Through Stabilizers
Span of Crane Stabilizers – this is available from the manufacturer handbook and from the original
stability test certificate plus any subsequent reports of thorough examination. The figure must be
inserted in metres and is based on a measurement taken between the stabilizer foot centres in their
fully extended position.
Span of Auxiliary Stabilizers – If auxiliary stabilizers are fitted, information should be available as
above. Again, the figure inserted must be in metres.
Offset of Loader Crane Column – This figure should be available from the manufacturer handbook
and/or the product range literature/sales brochure. The figure should be stated in metres and will
typically range from 0.15 to 0.30 metres; although in some cases it could be significantly higher.
Distance Aux Stabs from Crane Column – if auxiliary stabilizers are fitted, this information should be
available from the original axle/stability calculations carried out by the manufacturer/installer.
Again, this figure should be stated in metres as opposed to mm or cm.
Once the above data has been inserted in the boxes on the right-hand side of the Spreadsheet, the
stabilizer forces for the Loader (and Auxiliaries if fitted) will be displayed in both kN and tonnes in
the boxes on the left-hand side of the sheet.
The one remaining piece of data required for the user to input is the Maximum Permissible Load
Bearing Capacity of the ground, which must be stated in kN/m². The table below gives some values
for the load bearing capacity of various ground types. Once this is inserted, the sheet will calculate
the minimum size of the pad required in m²; and on the right-hand side of the sheet at the bottom, it
will also show the relevant minimum dimensions for both square pads and round pads. The pad
must be strong enough to spread the stabilizer load over the full foundation area. Pad design
calculations are required to ensure the pad has sufficient stiffness and strength to spread the load.
Permissible pressure on the ground (load-bearing capacity of the ground) to DIN 1054
Filled ground, not artificially compacted
0Asphalt
Established, evidently undisturbed ground
1 Mud, peat, marshy ground
2 Non-cohesive, adequately firmly established ground:
Fine to medium sand
Coarse sand to gravel
Crushed stone compacted
3 Cohesive ground
Mushy
Soft
Firm
Half-solid
Hard (solid)
4 Rock
Weathered
100 kN/m²
200 kN/m²
0 kN/m²
150 kN/m²
200 kN/m²
250 kN/m²
0 kN/m²
40 kN/m²
100 kN/m²
200 kN/m²
300 kN/m²
100 kN/m²
Disclaimer
This note is for guidance only, it should be studied and the information applied with the assistance of expert advice as necessary. Every
effort has been made to ensure the accuracy of the information provided, but no legal liability can be accepted by ALLMI for any errors or
omissions, nor for any consequences thereof. The specifying of any safety factors and mat assembly configurations is the responsibility of
the competent (appointed) person.