cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong) (06/13/89)
From: cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong)
I was catching up on several months backlog of Jane's Defence weekly
and International Defence review when I came across an article with several
artists' rendition of future MBTs. Basically they were nothing very new or
exciting (seen 'em all before :-)), One thing that caught eye though :-
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). All the references that I have looked up on don't seem to
address this question at all : why 80%-90% of the tanks that exists today
(and in the 1990's) have their turrets in the middle of the hull.
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.
b) Fast evacuation for the crew in case of emergencies through the back
exit, an option not available for the "middle turret" tank crews.
This, I'm sure saves a lot of lives as a lot of tank crews were
killed whilst exiting through top hatches in face of enemy fire.
(of course this assuming that it is knocked out)
c) Ease of reloading through the back door, (mechanical resupply
as used in the M-109); also with a back door the tank becomes
more flexible tactically. In Lebanon, the Merkava was used as an
APC (albeit very crowded) and makeshift ambulance.
d) A safer location for the powerpack and fuel tanks with them being
located at the most thickly armored area of the vehicle.
(This is a bit shaky though, grasping at straws even :-)
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; it's not as if this
is new unproven stuff...Hidebound traditionalism? The reasons (a) and (b) alone
are good enough reasons to have the turret built at the back of the hull.
The only minuses that I can think of for it are:
a) Reduced tank gun depression.
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?
Anyway after all this; I may be making a fool out of myself, One of you
chaps will probably blow me out of the water with some simple reason why
the "turret at the back" configuration is not so hot.....Oh Well live and
learn. Post soon !!!! I'm leaving for a vacation in a few weeks time AND
it's soon going to be MOOT point!!!!! MBTs in the 2000's have NO TURRETS!
They leave their guns dangling out! (external gun) ;-)
Tan See Teng ------------> cindi@bucsb.bu.edu
------------> engn1bc@buacca.bu.edu
No end-signature but I'm working on it.military@att.att.com (Bill Thacker) (06/13/89)
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
smb@ulysses.homer.nj.att.com (Steven M. Bellovin) (06/14/89)
From: smb@ulysses.homer.nj.att.com (Steven M. Bellovin) Might there be balance problems from the recoil, if the turret were mounted too far to the rear? Just guessing...
welty@lewis.crd.ge.com (richard welty) (06/14/89)
From: welty@lewis.crd.ge.com (richard welty) In article <7406@cbnews.ATT.COM>, Bill Thacker writes: =cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong) writes: => a) Reduced tank gun depression. =And this is important; depression is critical for obtaining hull =defilade positions behind hill crestlines. indeed. this is one of the reasons why US tank designs have tended to be taller than Soviet designs since WWII (another reason is that US tank designers take crew comfort more seriously than Soviet designers.) => 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. there is a major advantage to providing a large hatch over the engine compartment (large enough to pull the engine as a complete unit); it allows you to do a complete swap quickly when you are in a hurry (e.g. you need to get units back into combat as soon as possible.) at least some of the T-series Soviet tanks require disassembly of the engine inside the compartment piece-by-piece to make repairs. =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. this is sort of tricky. if the engine and transmission are at opposite ends, then you have to provide a driveshaft; a potentially messy problem in a tank design. there shouldn't be much effiency loss due to the presence of a drive shaft; more will be lost in the differential if the engine is longitudinal instead of transverse. richard -- richard welty welty@lewis.crd.ge.com welty@algol.crd.ge.com 518-387-6346, GE R&D, K1-5C39, Niskayuna, New York
jkmedcal@uunet.UU.NET (Jeff K Medcalf) (06/15/89)
From: Jeff K Medcalf <sun!Central!uokmax!jkmedcal@uunet.UU.NET> >From: cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong) > >[MBT's for '90's] 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 an almost purely defensive tank, such as the Merkava, mobility is sacrificed for armor and firepower. Putting the engine at the front both protects it when the tank is hull-down, and since the engine is less important than in a tank designed for mobility, means less detriment if the engine is disabled. However, a hit on the armor over the engine can disable the engine. Fuel lines may rupture under the impact shock, seals can be breached, the engine can vibrate off of its mounting. In fact, Soviet-made tanks in the desert wars had a tendency to explode when the hull was hit near the fuel tanks because the fuel would sometimes leak onto the hot engine... When you count mobility into suvivability, as the Germans especially do, then losing the engine means losing a great deal of your ability to survive. So you protect the engine. Also, the engine-in-back scheme has the advantage of making internal arrangements more comfortable. With the engine in front, spare ammo is almost literally under foot unless specially designed racks are used, which cut down on internal space (as opposed to many tanks having bins for ammo not stored in the turret). > b) Fast evacuation for the crew in case of emergencies through the back > exit, an option not available for the "middle turret" tank crews. > This, I'm sure saves a lot of lives as a lot of tank crews were > killed whilst exiting through top hatches in face of enemy fire. > (of course this assuming that it is knocked out) A bottom hatch solves this problem. > a) Reduced tank gun depression. Although this could be overcome by digging Merkava in, facing away from the enemy, so that the gun, rotated aft, has full depression, but the tank can sprint (well, as much as a Merkava can) away without first reversing. -- I dream I'm safe jkmedcal@uokmax.UUCP In my hotel womb Jeff Medcalf Soft and so nice It's a wonderful womb <-The Church, "Hotel Womb"
allen%codon1.Berkeley.EDU@ucbvax.Berkeley.EDU (Edward Allen;345 Mulford;x2-9025) (06/16/89)
From: allen%codon1.Berkeley.EDU@ucbvax.Berkeley.EDU (Edward Allen;345 Mulford;x2-9025) Richard Welty mentions that U.S. tanks are taller than Russian ones in part because of crew comfort. Part of the reason the Russians can get away with small crew compartments is that they select tank crews differently. We design our tanks so that men of a bit greater than average height can operate them. They select tank crews from among their smallest soldiers (smallest 10% is the figure I seem to remember). My dad told me about a (nonclassified) orientation film on the Soviet military organization that he saw when he was in the Air Force. I believe that's the source where I first learned this tidbit. If I remember right, fighter pilots and cosmonauts were picked from among the shortest men in the potential pools for the same reason. I also seem to remember accounts of the difficulty that crews of Isrealis had with captured Russian built tanks because of the crewman size difference. Ed Allen (allen@enzyme.berkeley.edu)
fiddler@Sun.COM (Steve Hix) (06/20/89)
From: fiddler@Sun.COM (Steve Hix) In article <7457@cbnews.ATT.COM>, welty@lewis.crd.ge.com (richard welty) writes: > > > From: welty@lewis.crd.ge.com (richard welty) > =cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong) writes: > => a) Reduced tank gun depression. > > =And this is important; depression is critical for obtaining hull > =defilade positions behind hill crestlines. > > indeed. this is one of the reasons why US tank designs have tended > to be taller than Soviet designs since WWII (another reason is that > US tank designers take crew comfort more seriously than Soviet > designers.) The Swedish S-tank (?) did away with the turret entirely. The use the adjustable suspension to get elevation and depression of the main gun. (And differential steering for aiming.) This makes for a *really* low profile, but how well does the beast work in practice?
fiddler@Sun.COM (Steve Hix) (06/20/89)
From: fiddler@Sun.COM (Steve Hix) In article <7405@cbnews.ATT.COM>, cindi%bucsb.BU.EDU@bu-it.bu.edu (Cynthia Fong) writes: > > 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. This is where a tank's armor is usually heaviest anyway...the engine in back should provide a bit of mass where the armor is thin. > b) Fast evacuation for the crew in case of emergencies through the back > exit, an option not available for the "middle turret" tank crews. > This, I'm sure saves a lot of lives as a lot of tank crews were > killed whilst exiting through top hatches in face of enemy fire. > (of course this assuming that it is knocked out) Several types of tanks have a belly hatch for such departures. This has the advantage of providing a bit of cover once you're outside. Bailing out during battle often has the disadvantage of putting your soft self out where bits of hard stuff are zipping about at high rates.
henry@zoo.toronto.edu (Henry Spencer) (06/20/89)
From: henry@zoo.toronto.edu (Henry Spencer) >... Part of the reason the Russians can get >away with small crew compartments is that they select tank crews >differently. We design our tanks so that men of a bit greater than >average height can operate them. They select tank crews from among their >smallest soldiers ... It's not just a difference in selection procedure; they've also got a rather different pool of manpower to draw on. For one thing, the pool is much bigger (they have universal conscription), so picking the smallest few percent still gives large numbers of tank crew. For another, the sort of mechanical background that one would prefer a tanker to have -- tank crew spend a *lot* of time making repairs -- is rare in the Soviet Union, so they don't have the complicating factor of trying to select tankers with the best background. It wouldn't work in the US. Henry Spencer at U of Toronto Zoology uunet!attcan!utzoo!henry henry@zoo.toronto.edu