Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!apple!rutgers!att!cbnews!military From: military@att.att.com (Bill Thacker) Newsgroups: sci.military Subject: Re: MBT Tank Turrets - (question) Message-ID: <7406@cbnews.ATT.COM> Date: 13 Jun 89 03:23:52 GMT Sender: military@cbnews.ATT.COM Lines: 111 Approved: military@att.att.com From: military@att.att.com (Bill Thacker) cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong) writes: > All the MBT's that are slated to enter service in the 1990's (the French >Le Clerc (sp?), the Korean XK-1, the Japanese MBT (name?), the M-1 upgrade >(with auto-loader)) all have their gun turrets located in the middle of the >hull; that is between the driver and the tank power-pack. This has always >puzzled me as one would think the more logical location for the turret would >be at the back of the tank, behind the driver and it's power-pack (a-la >Israeli Merkava). > > In the Israeli Merkava with it's turret behind the engine, I can see a >lot of advantages going for it : > > a) Extra protection provided by the mass of the engine in front of the > crew and ammo. But by the same token, having the engine in the rear adds protection against projectiles coming from that direction... where your armor is weak. Your other reasons are all good ones. > Well you get the general idea. Why are MBTs still designed with their >turrets in the middle???? I mean the M-109, Scorpion, Bradley, TAM (argentina), >and of course the Merkava have their turrets at the back; The M-109 is self-propelled arty, not an MBT; I expect the sacrifice is more reasonable there. The Bradley has a centrally-mounted turret, I believe, and being an infanty vehicle, has a mutant internal layout, anyway. And my photo of the TAM shows a centrally-mounted turret, albeit with a large overhang over the rear deck; but it's hard to tell. It's possible that the TAM retains the layout of the German Marder MICV on which it was based; with the engine side-by-side with the driver. >The only minuses that I can think of for it are: > > a) Reduced tank gun depression. And this is important; depression is critical for obtaining hull defilade positions behind hill crestlines. > b) Maintenance difficulties realting to access to the power-pack, but > this shouldn't be much of a big problem; the Merkava doesn't have > a bad maintenance rep does it? I would think that a good engine design would minimize the difficulties; but you'd still have problems with routine maintenance; lubrication and the like. With the large road wheels in current vogue, it'd be tough even if you provided side access panels; and the presence of these would weaken the side armor. I can think of a few other reasons, but frankly, I don't know for sure. Like you, I'm a bit surprised that more rear-turret designs aren't in use. 1) With the powerplant in the middle, cooling becomes a more difficult problem. This is especially important with turbine powerplants like that of the Abrams. (Of course, the Merkava makes do, even in the desert) 2) The transmission and differential have to be either at the front or rear, wherever you locate the drive sprockets. It probably improves space utilization to site the engine at the same place; maybe increases the power train's efficiency, too. 3) There's something to be said for having the driver in close proximity to the rest of the crew, rather than separated by the engine compartment. Even the Abrams, I believe, has a hatch connecting the turret basket and driver's compartment. 4) Gun overhang seems to be a major concern. In WWII, for example, the Germans rejected the idea of copying the T-34 because the longer German gun, combined with the forward-placed T-34 turret, would create an unacceptable gun overhang. I suppose this creates difficulties in maneuvering the vehicle. A rearward-placed turret would create similar problems with the gun traversed to the rear. 5) It may be that it improves the weight distribution to mount the turret centrally. The turret represents a major weight concentration, and perhaps placing it to the extreme rear adversely affects the balance of the tank. For example, it might make it prone to tipping when crossing obstacles or trenches, or increase the ground pressure in the rear, leading to easier bogging. If nothing else, it would require beefing up the rear suspension components. 6) The Abrams, at least, generates smoke by pumping oil into the exhaust system. If the engine was centrally located, the smoke would interfere with the turret's view. Finally, I suspect, as you mention, that there's a certain amount of tradition involved. >it's soon going to be MOOT point!!!!! MBTs in the 2000's have NO TURRETS! >They leave their guns dangling out! (external gun) ;-) Uh-huh. I'll believe it when I see it 8-) Let's not forget that MBT's of the 80's were supposed to use gun/missile launchers... - - - - - - - - - - - - - - - - - - - - - - - Bill Thacker moderator, sci.military military@att.att.com (614) 860-5294 "War is a matter of vital importance to the State; the province of life or death; the road to survival or ruin. It is mandatory that it be thoroughly studied." - Sun Tzu