3T Method - Mobile Access Tower Technical Update (Fitting Diagonal Braces)

This again will vary from Tower to Tower - the issue here is whether or not there is room to have diagonal braces running past the edges of a fully boarded intermediate deck as required with the 3T Method (with no handrail location rivets).

We believe that the Boss 1450 Span frames were deliberately designed to be "extra wide" to allow this (originally so that working decks could be placed across any pair of rungs without compromising the diagonal bracing pattern of the Tower). Even so, because of the "common node" bracing used, and the restrictions on deck positioning caused by the Ladderspan frames, we have found that the diagonal bracing pattern needs to be started in the correct position at the base of the tower to ensure that they are tight up against the frame uprights when they pass a deck edge.

Diagonal Braces need to be fitted correctly to allow them to pass intermediate deck levels

A simple rule to ensure that this happens with the Boss 1450 Ladderspan Tower is:

"ONE = ODD, TWO = EVEN"

• If the Final deck height is to be an odd-metre height (3,5,7,9,11 etc.), the first pair of diagonal braces must be fitted hard up against the frame uprights ("position 1" - see photo right). The next pair will then go inboard of the first pair ("position 2") and so on. This works because the intermediate decks are placed at 2m intervals down from the final deck level and the bracing pattern goes "full circle" every 2 metres, ensuring the braces always have the maximum space possible between them when they pass a deck level
• If the Final deck height is to be an even-metre height (2,4,6,8,10 etc.), the first pair of diagonal braces must be fitted a hooks width inboard of the frame uprights ("position 2" - see photo right). The next pair will then go hard up against the frame uprights ("position 1") and so on.

You will need to experiment with your Tower to see if this is an issue. As always, speak to your manufacturer if you are unsure, especially if the solution requires moving the braces up or down from the positions specified in the User Guide which could be dangerous!