His original question was why not the M60A1 style turret from the beginning? It is historically self-evident that the designers of the day did believe the longer turret with the smaller frontal aspect did provide the best compromise. We see that first with the M41 (ignore the M26 which predated the M41, and ignore the M46 because it was an emergency lash up), then with the M47. Then inexplicably the turret shape changed for the M48 (the M60 was another emergency design to quickly get a 105mm fielded), and then the M60A1.
And the M60A1/A3 turrets have significantly thicker armor at the front and on the sides. This shape is a compromise on both the internal volume requirement and the minimal weight requirement.
You can have a more ideal shape, or a more capacious turret, or less armor. But can't have all three if you have a weight requirement to meet.
Bojan's question was, and remains, a quite valid one. I agree with you that it offered more volume for a given weight of armor. I disagree that the shape was believed the best possible ballistic design for fighting other tanks, rather (scratching what I thought about casting ability) it was believed the best design shape and compromise to survive on the nuclear battlefied.
Nor did I say that the shape was the best possible ballistic design. What I'm pointing out is that the "users' had three requirements, and that the hemisphere shape best met those requirements. In fact, given the specifications, no other shape would have been geometrically possible, it would have drawn itself with the requirements input. Geometry dictates that the most efficient shape (least surface area) into which a given volume will fit is a sphere. Since half (or more) of the contents of the turrent are in the hull, we are speaking of a hemisphere, or a fraction thereof. Have a look at the turrets of virtually all the Russian designs after the T34/85....(not KV and such, but the T54/55/62/72). All of them are sections sliced off of a sphere. Oh, there are subtle distortions to the shape, but the effect is a sectioned sphere....that's just math and geometry at work dictating the most efficient shape for a given volume. Happily, it also gives you an acceptable, if not ideal, ballistic shape. Anything else cannot help but intrude into the fighting space of the turret. The M48 design was the best that could achieve the priorities stated in the requirements. Additionally, I suspect that trying to cast compound shapes into a single casting is either much more difficult or cannot be done. I love the lines of the M41, too, but notice how many welds it has. The objective was a large, well armored turret cast in one piece (Bojan does not seem to consider welds as participants in structural integrity/ballistic goodness. Well, they are. The M48 turret was intened to be of one piece with no structural welds, which makes it stronger. (hatches, mantlets, infantry rails, etc. are hardly part of the main structure). Every joint is a weak spot and the M48 has fewer of them than other designs of the era since it is of one piece.
I'd like to see figures for the internal volume of an M60 turret vs an M60A1 turret. My suspicion is that the volume will be less (unless the turret was stretched to compensate, which I think it was) in the A1 because it was later determined that the width provided for on the m48 turned out no longer to be as critical as expected when it was designed....but that's hindsight and has nothing to do with why one should have preceded the other.
I'm having severe sinus problems right now and looking at the screen does not help. I may draw a picture tomorrow and post so it is more easily scene what the introduction of a narrowed, planar surface does to a sectioned spherical shape.
Edited by Doug Kibbey, 13 October 2012 - 0121 AM.