On 21/02/17 17:19, Nick Maclaren wrote:
In article ,
Tim Watts wrote:

Can you explain why tree surgeons almost always have a tripod ladder?

Tripod ladders are easier to get closer to trees.

They have a very wide area of footing and 3 legs is inherently stable on
unplanar ground.

You're missing the point. For a given leg separation, the distance
from the centre (at ground level) to the closest point outside the
triangle is much less than it is for the quadrilateral. Therefore,
the ladder will fall over for a much lower imbalance in the weight
or sideways force.


Regards,
Nick Maclaren.


However, the tripod ladder leg spacings are MUCH larger than 4 legged
ladders - and a 4 legged ladder would be very unstable on non planar ground.

So tripods of a suitable size seem like a win to me for that particular
purpose.