Can someone explain the logic of a carb balance tube when running triple carbs? It seems to contradict the point of having multi carbs, that is each port having unrestricted access to a carb, without interference from other cylinders. Also when a balance tube is used, why then have a small tube? If a tube is good why not make a big one?

Greetings . . .

My understanding is that balance tubes are used to tune the setup for idle and part throttle conditions. And that as the throttle opening increases the balance tube becomes less and less relevant.

Some will have you believe that balance tubes were largely misunderstood 'back in the day' . . . but some of the technical literature I have read suggests that balance pipes/tubes were engineered to a certain size:
SU Carbs

I guess if you increase the balance pipe to a large enough size - the setup would become a log manifold . . .

regards,
stock49