Yikes,
First off the 6" - 4" sphere was because of kids falling through, I posted the studies and the documentation that validated the reduced size on ANOTHER THREAD.
Second, heads getting stuck was talked about, but not in the main reason statements nor the reason. I posted a link on another post about this.
Third, getting the head through and then the body follows has been an assumption for cable, the main issue on that is fixed balusters.
When the head goes in and the cables snap closed the kids pull back, also it very common for kids to not play around the cable style guards because they move and the second reason is that the 1x19 cable is very catchy to small children hairs on the arms and legs. It catches and as they move a long and rub the cables and it pulls the hair out making them step back. Parents have noted it looks like they get a shock. but it is not.
Yikes Mark, I do not necessarily agree with Yankee on the rationale of his interpretation, but if he is the building official, does he not have a right to make his own interpretation per IBC 104?
If I disagree with his interpretation, there is an appeals process, at least here in California. I can also request an interpretation from the State Fire Marshal that is binding upon the local department.
Yikes, you are correct that under IBC 104 the inspector may have that right, however he did not fail it for IBC-104 he failed it for IBC 1607.7.1.2.
Also I will say it again, 50lbs on a 4" sphere is not a correct method nor good test method.
ASTM 935 has a complete testing method for this type of testing of spreading, it requires a specially design ice-cream cone type device that does get 50 lbs of force applied but the shape, slope and size are based on maximum size x 1.25 plus a whole bunch of other requirements.
I can tell you this, we have tested cables this way and 1/8" cables spaced 3-3/6" centerline with 44 inches between the vertical posts or post and tension bar requires with 400 lbs of tension takes about 87lb of force to spread to failure which is 75% greater than fail point.
finger pulling is not correct as all have noted, but saying 4" with 50lb is correct when the engineers and ASTM process has published and updated many times not changing this method, well I side with the proven method, not back yard theory.
