i am building a14 ft conference of black limba it sets in a 1 1/2 angle iron frame around outer edge how much gap or clearence do i need to leave between wood and frame for expansion

Youe question is to vague to get a good answer. Is the 14' across the grain, or down the length?
What is the MC of the wood now, and what is the EMC expected to be where it will end up?

Surely to god 14' is the length. Regardless of the width or length the captive steel frame is a death sentence. Heck, what would the expansion be on a 4' top? 1/4-3/8" minimum?

Shrinkulator

Bad design cannot be overcome by the statistical design parameters of the Shrinkulator. Wood is meant to float - allowed to expand and contract. If it is not allowed to move with normal seasonal changes in RH, then it will self-destruct somehow.
The OP needs a different design. When people that do not know about wood get involved in designing a large table, they always go to steel to allay their ignorance of the subject. Most likely, there is no reason for the steel other than to 'prevent warp'.

You can predict the amount of movement
using our Wood Shrinkage Calculator at the
link included with my response.

If Gene Wengert weighs in, I suspect he'll
remind us all that the amount of wood
movement is based on species, the
change(s) in relative humidity, and the
"style" of the board (flatsawn Vs. 1/4 sawn). What
I've learned after many years of paying attention
to Gene's posts .... if the humidity in the
room the table will reside stays the same
(climate control), and the MC of the table/wood
when put in service matches the EMC of
the room, then there will be no movement.

Not a likely scenario - the EMC (equilibrium
moisture content) is a finite value - if you
know the relative humidity of a room, then you
can accurately predict the what the moisture content
of wood will acclimate to.

A short snippet from a WOODWEB Knowledge Base
article on EMC:

-----------
0% RH = 0% MC = 0% EMC
30% RH = 6% MC = 6% EMC
50% RH = 9% MC = 9% EMC
65% RH = 12% MC = 12% EMC
80% RH = 16% MC = 16% EMC
99% RH = 28% MC (approx.) = 28% EMC (approx.)

Note that most heated homes and offices will run 6% EMC
in the wintertime and even a bit lower. In the summertime,
9% EMC is common. Outside in most of North America,
the outside is 12% EMC, summer and winter. In coastal
locations, 16% EMC outside is common.
-----------

So - if you know what the RH swing will be where your
table will reside, you can use the calculator to predict
the amount of wood movement.

As mentioned be others, a steel-bound wood table slab
will likely be a problem. You don't mention a width,
but as an example, a 36" wide glued up wood slab
of flat sawn red maple (a relatively tame movement
species) will expand (or shrink) 5/16" cycling between
6% to 9% MC. If the table is 9% MC when put in service
in that scenario, it would shrink 5/16 - if it is
6% MC when put in service, it would expand 5/16.

Hope this helps, and if we're lucky, Gene will
confirm (or correct) my thoughts.

Carl

WOODWEB's Wood Shrinkage Calculator