Quote Originally Posted by Firn View Post
It seems that quite a few here think that infantry organized to fight alongside MBTs need a carrier with MBT-like qualities, especially armor and mobility, minus the firepower. The Merkava - Namer combination has been named as a good example. Considering the low numbers of vehicles purchased, especially in Europe, and the advantages of a mostly shared vehicle does it make sense to go with a standard front engine configuration for new MBT projects?
A major factor in favour of a front-engine and transmission is use of their mass and bulk to increase forward protection up to the top of the glacis. That location and use can be considered as likely to increase the probability of a mobility kill. However, a penetration of the forward hull that causes such damage is anyway likely to injure crew members and otherwise disable the vehicle, or similarly an equivalent rear-engine vehicle. The other major gain with a front-engine is that the rear hull can then include a door and ramp that enables ready and better protected entry and egress for the crew and any passengers, possibly including one or more litter-borne casualties.

Conversely a major factor in favour of a rear-engine and transmission is that they act as a counterweight to armour concentrated at the front end which a crew typically aims at what they perceive to be their main threat. Another factor is that pulling track to a rear sprocket is more efficient in terms of energy lost to friction than pulling to a front sprocket, or to an elevated sprocket on a mid-engined tracked vehicle as used mainly by industry.

Each of those factors is obvious but assessment of their importance has been affected by considerations that are specific to and supposedly mandatory for a well-configured MBT with an enclosed main armament. One is that its gun should be mounted as low as practicable on the vehicle in order to minimise overall height and particularly the weight of armour on the turret front and to some extent its sides. Nothwithstanding that the turret roof must be high enough so the gun can depress below the horizontal for utility and hull-down fire over a berm or other form of cover. Somewhat similarly elevation is restricted to avoid recoil into the turret floor.

However, the Israeli Merkava Mark 1 through Mark 4 tanks each have the engine and transmission below a mildly sloped glacis and have a turret which provides depression and elevation of -8.5 and +20 within a turret roof height of 2.8 m. Corresponding figures for other western MBTS are: Abrams: -9, +20, 2.9m; Challenger: -10, +20, 2.5m; Le Clerc: -8, +15, 2.9m; Leopard-2: -9, +20, 3m. So relative to western rear-engined MBTs, Merkava has a small reduction in its main armament depression.

In regard to elevation the modern MBT can be required to employ its main and especially its co-axial armament in close-range fire against built-up and high-rise targets. To enable that its armament must be mounted higher above the hull floor in either a flat-roofed or contour-roofed turret which encloses the armament, or above the hull in a remotely operated super-elevated and armoured gun mount. That last type of mount brings its own set of problems. For example in order to be fired broadside on it may - to reduce the overturning moment - demand the complication of variable recoil length. The practicable increase in elevation and in depression will be large for an externally mounted main armament, with lesser increases gained for an armament enclosed in a flat-roofed or contoured turret. Notwithstanding such applied considerations, the vital aspect is that a front-engine chassis does not intrinsicly compromise the functioning or use of mounts or turrets.

Back in the late-1960s the Israeli’s decided it made sense to adopt a front-engine configuration for the Merkava MBT. Their rationale was clearcut then and is even more applicable today. For generally similar reasons a front-engine is also preferable for the heavy ARV/recovery and AEV/combat engineer vehicles and also the HAG/assault gun. To assist forward and backward towing and pushing, dozing, excavating, lifting and ripping the ARV (which functions also as an auxiliary AEV) and AEV (which functions as an auxiliary ARV) are often ballasted down. Adopting a front-engine configuration would require different arrangements for ballast. However that might be fully offset against the utility of a rear doorway/ramp for their mechanics and engineers.

The one exception is the heavy AVLB/assault bridge which needs a counterweight to support the launch of a scissor or cantilever bridge. An alternative front-engine configuration would require a reversing manoeuvre toward the gap followed by ‘rearward’ launch of a bridge. For that the crew’s vision could be augmented - as is already common - by means of closed-circuit cameras, and the stern of the vehicle could carry ‘additional’ armour transferred from the bow. Alternate crew positions might even be provided at each end. With bridge(s) offloaded an AVLB is commonly expected to function as an auxiliary ARV or AEV. Providing a dozer blade/stabilizer at each end could result in a double-ended auxiliary ARV/AEV, always provided that a door/ramp was still readily accessible at one or other end.

Enough theorising. The short answer to the question is an unqualified yes it makes sense to go with a front-engine configuration for new MBT projects.

If - however unlikely it seems - more than two new MBT projects are commenced in the future then one of those three or more could be rear-engined or mid-engined.