M3 Grant and M4 Sherman Family of Vehicles

[Old Wombat]

Typically neat conversion from the Israelis but, even with their knack for making things remain effective long past their obsolescence dates, a lot of work for not much gain.

[Dizzyfugu]

Interesting - a custom chopper? 

[PR19_Kit]

Typically neat conversion from the Israelis but, even with their knack for making things remain effective long past their obsolescence dates, a lot of work for not much gain.

Yeah, but if you don't have any other source of supply, and your neighbours are beating at your door with sticks...............

[Old Wombat]

Typically neat conversion from the Israelis but, even with their knack for making things remain effective long past their obsolescence dates, a lot of work for not much gain.

Yeah, but if you don't have any other source of supply, and your neighbours are beating at your door with sticks...............

Yeah, but it doesn't significantly improve the effectiveness or survivability of the tank for the cost of the conversion which is why, I would suggest, that it only made it to the prototype stage.

[PR19_Kit]

Doesn't make it more difficult to see if it has a lower silhouette?

[Old Wombat]

C'mon, Kit!

Cost/Benefit, mate!

Does the cost of the modification out-weigh the benefits of reducing the height of the tank?

Can you achieve the same/a similar result through training?

I would say that the answer to both of those questions is "Yes".


In a defensive role: use a bulldozer to take a few more scrapes of soil out of the ground & you've dropped your silhouette by 30cm, or don't come so far up the ridge line you're shooting over & you're still only showing your turret (at most). The M4 Sherman could sit in ambush with only the optics (&, maybe, a machine gun) showing above a ridge line, lay onto the target, drive forward, gunner adjusts his aim slightly, fire a couple of shots & go back behind the ridge line.

During an advance: go forward in smaller groups with other tanks behind, in cover, to support the advance, use the terrain to your advantage.

That whole process is what drove the development of Western armour & tactics in the Cold War. Western tanks have always been taller & bigger than their Soviet/Russian counterparts but they've almost invariably had better crew ergonomics & a better gun depression for firing from cover. (This was also a very good indicator of the mindsets of the Western & Soviet/Russian militaries; the Western mindset was/is defensive, the Soviet/Russian mindset was/is aggressive.)

Sure, if you can design a tank to have a lower silhouette, do it, especially if there is no/minimal reduction in crew comfort & efficiency, but the cost in industrial capacity & money of cutting 30cm from the height of an existing tank is much too high, when compared to the minimal impact it would have on the survivability of the tank & its crew, compared to the benefits of better training & tactics.

[PR19_Kit]

That explains such things very well Womby, thanks a lot. 

I don't think like that but you obviously do, and it makes sense. I've always like the look of low tanks, like the crazy Swedish S tank, but not the 'squashed look' that the Sovs made with most of theirs.

[Weaver]

Spot on Wombat: that was exactly the conclusion of the Israeli experiment. 

Pure speculation here, but I wonder if part of the point of the exercise was to evaluate it against standard Shermans to quantify exactly HOW much advantage the lower profile gave it, in order to inform future tank purchase/design?

If you're fitting a Sherman with a more compact engine, thereby leaving spare space in the engine bay, then I suspect there are other things you can do with that space that give you a better payoff than lower sillouette. Three that immediately spring to mind are:

Bigger fuel tanks
Better cooling system
Better fire-suppression system

[Old Wombat]

If you're fitting a Sherman with a more compact engine, thereby leaving spare space in the engine bay, then I suspect there are other things you can do with that space that give you a better payoff than lower sillouette. Three that immediately spring to mind are:

Bigger fuel tanks
Better cooling system
Better fire-suppression system

Which, if I remember correctly, is almost exactly what the Israelis did with their diesel powered M4s.

[jcf]

The Degem Yud had the same Cummins VT8-460 turbo-diesel used in the M50/M51
series.

That series of Cummins engines; V-300, V8-300M, VT8-370M, VT8-460, V903, are all
approximately the same size in terms of base engine: ~48"L X 42"W X 40"H, give or
take depending on exact configuration. The length is from the face of the flywheel to
the front of the engine and does not include a clutch housing.
The marine versions are over 20" longer because of the reversing gearbox and larger
water pump.
The displacement is 785 cu.in. in all except the V903 which was increased to 903 cu.in.,
at the same time Cummins stopped using horsepower in their numbering scheme and
switched to displacement.

The Continental R-975-C1 used in the M4 was 53"L X 45"D, by the time the clutch
housing is added the Cummins OAL is probably greater than that of the Continental.

Changing the engine didn't really gain that much room in the engine bay, the main
advantage, like the other engines used in the M4 series, was that the driveshaft from
the engine to the transmission/final drive was no longer running at a diagonal.

As it happens the boat I worked on in Hawai'i for five years has a Cummins V8-300,
which is a naturally aspirated version of the engine, and it's a big ol' lump.

[Weaver]

It wasn't so much the length of the engine as the height that I think was significant. The radial needed a tall engine bay, and it's prop shaft lifted the turret basket up too. The V-12 would be lower, which is what allowed the IDF to lower the sillouette.

[Old Wombat]

It wasn't so much the length of the engine as the height that I think was significant. The radial needed a tall engine bay, and it's prop shaft lifted the turret basket up too. The V-12 would be lower, which is what allowed the IDF to lower the sillouette.

That is correct. The M4A2's, mainly used by the USMC, had a lot more room over the GM 6046 U-12 diesel engines than the earlier Continental R-975 powered M4's & M4A1's.

M4A3's, powered by the Ford GAA V8, also had more room above the engine. The additional height was re-used when the M4A4's went to the Chrysler A57 Multibank (5-bank W30's) & the M4A6's went to the Caterpillar D-200 (a diesel modified Wright R-1820 Cyclone).

[jcf]

The Cummins engine was a V-8, not a V-12.

As to the drive shaft angle, the GAA V-8 and GM 6046 diesel had a straighter run, but the Chrysler
A57 multi-bank still had a higher angle diagonal run. The hull of the M4A4 was lengthened and bulges
added to the engine deck and the bottom of the hull to accommodate the bulky A57.

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R-975

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A57

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6046 Diesel

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Ford GAA

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Engine specs. comparison.


Lowering the hull top as in the Yud only results in a cramped interior with Soviet style $hite ergonomics.

[Weaver]

You can see from those cutaways that the radial was mounted some distance off the engine bay floor to allow maintenance access to the lower cylinder heads, while the Vs sit almost flat on the floor. This means that the difference between the space needed for the two installations was greater than the difference in height between the two bare engines.

I don't see why the Degem Yud's ergonomics should be significantly worse than the normal M50's. The turret and basket are unmodified, just nearer the ground, so nothing really changes for the turret crew. The driver and hull gunner's seats are a significant distnace off the floor, so I suspect they would have been lowerd and the controls modified to match. Whether this worsened or improved the ergonomics would be a matter of detailed design, but if it made things worse, then that might be another reason why the Degem yud wasn't adopted.

[RAFF-35]

Reviving an old thread here, but I couldn't help noticing the lack of "JagdShermans". So I thought I'd add a few images I found whilst googling. I intend to build my own variation in the near(ish) future. The thing that's holding me back from building my own is that I haven't thought of a good, plausable scenario for such a vehicle that would be better suited than the real-world M36 Jackson. Any ideas??