Why are turrets of modern tanks so long?

[shep854]

Remember the construction of the ammunition is also a factor.  The separate ammo of Russian tanks don't need the space behind the gun that longer Western fixed cartridges require.

[Arminius]

On 11/21/2022 at 12:11 AM, KV7 said:

I think they are thinking there is a longer recoil stroke, so the turret needs to be longer to stop the gun at full recoil hitting the back face. But typically there is ample space here.

Exactly. I did not think of the turret ring, but of the recoil stroke. There HAS to be room for the recoil stroke and for inserting that long shell. Longer recoil path, longer shell = longer turret.

Hermann

[Stefan Kotsch]

1 minute ago, Arminius said:

Longer recoil path, longer shell = longer turret.

To do this, the turret ring would have to be enlarged.  Because the gun needs vertical mobility

 Larger turret ring = wider hull.

[bojan]

1 hour ago, Domobran7 said:

... and Degman was also supposed to use it)?

No, only planned improvement (that was already planned for Vihor, but early Degman mockup did not use it for some reason) was reverse rotation of carousel and slightly increased rotation speed.

There was another project however, that was basically Leclerc turret on T-72 hull, but that was French projects and AFAIK Croatia had nothing to do with it.

[DB]

One could envisage a bustle autoloader that would require minimal additional space behind the breech - just enough to allow for a ramming mechanism behind the round to push it forward - so the limiting factor (as has been mentioned before) would be the length of recoil. The depth "saved" would be related to approximately the difference between the length of the round, plus the space needed for the loader to bring the round into position; minus the length of the recoil stroke, more or less. (And you'd have to have enough space to allow for ejecting a case stub, too.)

If one were to use two-part ammunition, then the depth of the round would be about halved, so the bustle length could be reduced, but you'd need to ram in two stages and probably carry half as many rounds, neither of which you'd want.

 

[Stefan Kotsch]

This is the Soviet style auto loader. 

[KV7]

2 hours ago, DB said:

One could envisage a bustle autoloader that would require minimal additional space behind the breech - just enough to allow for a ramming mechanism behind the round to push it forward - so the limiting factor (as has been mentioned before) would be the length of recoil. The depth "saved" would be related to approximately the difference between the length of the round, plus the space needed for the loader to bring the round into position; minus the length of the recoil stroke, more or less. (And you'd have to have enough space to allow for ejecting a case stub, too.)

If one were to use two-part ammunition, then the depth of the round would be about halved, so the bustle length could be reduced, but you'd need to ram in two stages and probably carry half as many rounds, neither of which you'd want.

 

You could also bring the gun to horizontal to load from the bustle. Then you need only the recoil distance.

[shep854]

 

[Stuart Galbraith]

For a horrible moment I could have swore that was Elon Musk.😳

[GJK]

21 hours ago, Stefan Kotsch said:

That would be new to me. Due to modern electronics, thermal cameras take up little space.

I was referring specifically to the cooling system required for thermal sights of a certain vintage.  Didn't want to be too specific.

[Stefan Kotsch]

1 hour ago, GJK said:

I was referring specifically to the cooling system required for thermal sights of a certain vintage

Such a Stirling cooler is relatively small and fits directly into the camera. 

[GJK]

23 minutes ago, Stefan Kotsch said:

Such a Stirling cooler is relatively small and fits directly into the camera. 

That may be so, but not fitted to anything I worked on.

[Wobbly Head]

1 hour ago, GJK said:

That may be so, but not fitted to anything I worked on.

 

I remember working on the TOGS compressors on Challenger 1 they were big the same size as the TISH Camera head. Then the SPIRE system an interim sight fitted to some CVRT Scimitars that was used during one of the Bosnia campaigns. A copy of the sight the Bradley IFV had it had a small cooler on the side but still needed several assembies.

The I had to play with the BGTI as part of the Bowman project they used the old Raven sight bodies (the sights fitted to the first Warriors) and mounted a complete thermal sight in them for some of the warrior varients. The technology has definately changed and the size has seriously shrunk.

[GJK]

3 hours ago, Wobbly Head said:

 

I remember working on the TOGS compressors on Challenger 1 they were big the same size as the TISH Camera head. Then the SPIRE system an interim sight fitted to some CVRT Scimitars that was used during one of the Bosnia campaigns. A copy of the sight the Bradley IFV had it had a small cooler on the side but still needed several assembies.

The I had to play with the BGTI as part of the Bowman project they used the old Raven sight bodies (the sights fitted to the first Warriors) and mounted a complete thermal sight in them for some of the warrior varients. The technology has definately changed and the size has seriously shrunk.

TOGS is the system I was referring to.  I didn't personally do anything hands-on with BGTI or SPIRE.

[Stuart Galbraith]

11 hours ago, Wobbly Head said:

 

I remember working on the TOGS compressors on Challenger 1 they were big the same size as the TISH Camera head. Then the SPIRE system an interim sight fitted to some CVRT Scimitars that was used during one of the Bosnia campaigns. A copy of the sight the Bradley IFV had it had a small cooler on the side but still needed several assembies.

The I had to play with the BGTI as part of the Bowman project they used the old Raven sight bodies (the sights fitted to the first Warriors) and mounted a complete thermal sight in them for some of the warrior varients. The technology has definately changed and the size has seriously shrunk.

That had a good reputation. I recall reading one book where a senior army officer, after looking through a BGTI was told by a Sergeant 'Who needs Recce now?' Which illustrates the kind of performance the system would seem to have had.

[Stefan Kotsch]

12 hours ago, Wobbly Head said:

I remember working on the TOGS compressors on Challenger 1

Well, the Challenger 1 is rather less suitable as an example of long tank turrets. In the stern are assemblies of the weapon stabilization system, the batteries for the power supply of the turret and the NBC equipment. And then the cooler of the thermal imager was not in the rear of the tower, presumably. 

[alejandro_]

On 11/18/2022 at 7:42 AM, Domobran7 said:

And no, it doesn't make it more dangerous, at least if the turret is properly designed. Basically, ammunition stored in the hull is more difficult to hit, but if it cooks off, results are always catastrophic. Modern turret storage is done so that there are blowout panels, which means that instead of destroying the entire tank, explosion is (mostly) vented upwards, though the path of least resistance.

Following first encounters with Soviet tanks it was ordered to avoid using ammunition storage in the turret, but I am not sure if the order was followed/reinforced as tanks captured by the US Army later on had ammo in it. From Tigers in combat vol 1, chapter on SPzAb 501/424, page 46:

12 August 1944: The attack is stopped in face of strong resistance. Only 8 tanks are operational. A hidden T-34/85 of the 53rd Guards Tank Brigade ambushes them near Obledo and knocks out several Tiger lIs (3 tanks are totally destroyed). The ammunition stowed inside the turrets causes fatal explosions, killing many crewmembers. Following this, no 8.8-centimeter main-gun ammunition is stowed in the turret any more, reducing the stowage to 68 rounds.
 

Edited November 24, 2022 by alejandro_

[Domobran7]

12 hours ago, alejandro_ said:

Following first encounters with Soviet tanks it was ordered to avoid using ammunition storage in the turret, but I am not sure if the order was followed/reinforced as tanks captured by the US Army later on had ammo in it. From Tigers in combat vol 1, chapter on SPzAb 501/424, page 46:

12 August 1944: The attack is stopped in face of strong resistance. Only 8 tanks are operational. A hidden T-34/85 of the 53rd Guards Tank Brigade ambushes them near Obledo and knocks out several Tiger lIs (3 tanks are totally destroyed). The ammunition stowed inside the turrets causes fatal explosions, killing many crewmembers. Following this, no 8.8-centimeter main-gun ammunition is stowed in the turret any more, reducing the stowage to 68 rounds.
 

That is why I noted "at least if the turret is properly designed". If you look at Tiger II, it had ammunition in the turret, but that ammunition does not appear to have been separated from the crew compartment. It is simply sitting there.

That is definitely not modern tank turret stowage with blowout panels.

[GJK]

On 11/24/2022 at 8:51 AM, Stefan Kotsch said:

Well, the Challenger 1 is rather less suitable as an example of long tank turrets. In the stern are assemblies of the weapon stabilization system, the batteries for the power supply of the turret and the NBC equipment. And then the cooler of the thermal imager was not in the rear of the tower, presumably. 

Can't say for Challenger 1, it is Challenger 2 I have experience of.

My point regarding the size of the TOGS ancillaries is not where specifically in the turret they are, rather that it adds to the amount of equipment which must be accommodated within the turret.  This in turn affects the size of the turret.  Width is largely fixed, it is not desirable to increase the height, therefore it is the length which is increased.

Best,

Greg.

[alejandro_]

11 hours ago, Domobran7 said:

That is why I noted "at least if the turret is properly designed". If you look at Tiger II, it had ammunition in the turret, but that ammunition does not appear to have been separated from the crew compartment. It is simply sitting there.

That is definitely not modern tank turret stowage with blowout panels.

It seems to be similar in other countries. T-34-76 did not have any rounds in the turret, but IS-2 and T-34-85 did. IIRC in IS-2 the propellant was placed further down, so some thought was given to the safety. At the end of the day you needed to carry certain amount of projectiles, and German tanks carried more rounds.

[Renegade334]

Well, if ever we do get an upgrade to 140mm or thereabouts, wonder no more about where the length increase shall come from.

Just for the record, these are pictures of the M1 CATTB with its Benet Labs XM91 cassette autoloader, which fed an XM291 smoothbore gun...which was capable of swapping 120mm and 140mm barrels without too much trouble (the XM91 was also capable of accepting both ammo types).

And you can also judge for yourself the sheer thickness of the frontal armor package.

EDIT: the last vehicle is actually the M1 Thumper (see the rings on the turret sides), which was built in 1988, five years before CATTB Phase I (1993) and Phase II (1994), to test (among other things) the ATAC gun. Turret geometry is roughly the same, as it also had the XM91, though bustle protection is much better than the CATTB's.

Edited November 25, 2022 by Renegade334