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"Stabilisation of AFV guns" Topic


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UshCha09 Apr 2021 2:33 a.m. PST

It's really quiet here so I thought it was time to contribute.

NOTE This topic is unsutable for D6 fanatics, you will be instantly boored. ;-).

A few days ago we had a fascinating discussion running for some 2 hrs on stabilisation and standards of gun sights on AFV's. As game designers it's key to understanding the ins and outs of technology in far more detail than is required by the rules in many cases. The reason is the understanding is key to making sure any simplification is both plausible and consistent with the rest of the system and will not cause anomalies that can destroy credibility of the overall game.

Stabilisation and sight standard at one level are somewhat similar in that both improve accuracy one under all conditions and stabilisation while moving, in the case of early AFV's, as they can fire faster after a stop as the stabilisation even if crude, can allow a stationary vehicle to fire accurately before suspension rock has fully stopped.

In the initial rules our expert proof reader noted a level of a poor relationship between sight standard and stabilisation standard. Effectively we had linked sight standard and stabilisation standard together. High Teck sights implied 3rd gen stabilisation. Thus from a purely results perspective we could have ignored, to some extent stabilisation, standard even though it features in our specifications.

So there ended a spirited debate as to where and how to present the information to the gamers. In the sight table standard of stabilisation did not matter as it was implied, but as AFV enthusiasts this seemed inappropriate.

We settled for keeping the rules more or less as original, it was not wrong generally. However Issue 2 will have a few notes on this issue and if we come across a system that cannot reasonably be "lumped together" then there will be option variations in the army listing. This is not my perfect solution there never is a perfect solution, just the best compromise. I we try to avoid army list variations of rules as it adds unnecessary complication as someone without the list will not know of the variation, not ideal but perhaps tolerable at a push.

What is your approach on such issues in simulation?

Gwydion09 Apr 2021 4:47 a.m. PST

Depends what I am simulating and at what level of leadership/action.

If I were simulating a tank on tank 'duel', or following the fortunes of one crew through a battle/battles, I'd want the variations in, as those minor differences may be crucial and will give the flavour/feeling of the role I am simulating.

If I am simulating a battalion commander's experience then not so much I will accept subsuming the minor differences into a generally acceptable statistical model of combat and concentrate more on what that level of leadership should be concerning themselves with in battle- ie not the thing I can't do anything about sight/stabilisation design.

That may add something to my deliberations about how many Shermans I may need to deploy to cripple/scare off a Tiger. Ideally I'd like to lay up in enfilade defilade but if I've got to attack then move and fire it is and the tank commander and troop leader will work out the details. Bothering about each gun sight will be an overcomplication of game mechanics at this level and add little to the simulation.

Agree on the compromise thought perfection doesn't exist.

PatriotGrunt09 Apr 2021 6:01 a.m. PST

"A fascinating discussion running for some 2 hrs on stabilisation and standards of gun sights on AFV's"?

Brother, I am a gearhead and even I would say that is a contradiction in terms. ;)

Wolfhag09 Apr 2021 7:29 a.m. PST

At the 1:1 tactical level, I allow stabilized and shoulder-mounted guns to fire a few seconds sooner when performing a halt fire. Firing at a point target on the move does allow slightly more accurate firing but it was advised against doing it at over 600 yards according to the Sherman manual. Firing on the move is less of an accuracy penalty with a stabilizer. The speed and ground type affected accuracy too. Torsion bar suspension did stabilize the entire tank so would have a slight accuracy advantage firing on the move.

Of course, historically it took an experienced and trained crew to use them, and depending on the type of combat may not have needed them to begin with.

There were some limitations. With the Sherman it took time to adjust the stabilizer and took 5+ minutes for the gyros to spin up and be stabilized. They needed to be set for AP or HE rounds. You could not just flip it on or off. It also made loading on the move more difficult with the receiver moving up and down while attempting to load a round.

One problem I see regarding firing on the move with or without a stabilizer is how do you adjust follow-up shots? There is up to a 1/10 of a second delay between firing and the round leaving the tube with the muzzle moving up or down slightly as there was a slight lag time with the stabilizer adjusting up or down. That means if the gunner fired when the crosshairs are on the target he'd most likely miss. Also, the sights were not stabilized which means the barrel and sights are not pointing at the same spot most of the time. It reminds me of 17-18th century naval gunnery where the gunner fired on the up or down motion of the ship to target the hull or masts.

Stabilized guns do have an advantage for an attacker allowing him to move and conduct Recon by Fire into treelines. I think this may be one of the reasons US Shermans overloaded their tanks with HE rounds. Recon by Fire does not need to be accurate and rounds exploding in treelines give an air burst and rounds hitting short can ricochet and travel 20-30 more yards before exploding as an airburst.

According to the accounts I've read, the modern 3-axis stabilizers allow firing on the move to be almost like being stationery.

I could probably get into a 2-hour conversation about the topic, especially if someone disagreed with me. <grin>

Wolfhag

advocate09 Apr 2021 8:52 a.m. PST

I don't consider myself a d6 fanatic, but you might lump me in with them.

Blutarski09 Apr 2021 8:57 a.m. PST

I've also read that the Sherman gun stabilizer required regular care and maintenance that a lot of crews, for whatever reason, declined to perform. It probably appeared to be somewhat of an "alien technology" to many.

B

Wolfhag09 Apr 2021 9:53 a.m. PST

The training was important and not all units had the same level of training. If you lost the crew member that knew how to make it work it would be useless. It appears the British didn't have the same level of training so took them out or didn't use them. If you are in a tank/infantry attack and moving as fast as the infantry you would most likely not need a stabilizer to shoot on the move.

The manufacturers of the stabilizer may have sent tech reps to show and train the crews how to use and maintain them. I'm not sure if the Russians used them.

They did appear in the Grant for the 75 and 37mm gun. There were two manufacturers (Oilgear and Westinghouse?). The later one was better.

More info: link

Wolfhag

Major Mike09 Apr 2021 11:40 a.m. PST

I think the greater concern is getting the gunner, with his limited vision and sights, to actually acquire a target/threat the TC may or may not have spotted. Just because one member of a crew see's something does not mean it is really seen by the others. Firing on the move is rare unless it is the mg or you're just trying to scare your opponent as you drive at them and blast away. The moving breach is a very minor inconvenience, but the up/down movement of the muzzle of the main gun is an issue. Early azimuth stabilization was good for getting the gunner into the target area with his sight, then a short halt to allow for final corrections to the sight picture before firing.

UshCha09 Apr 2021 1:35 p.m. PST

PatriotGrunt. Nah you need a demotion 4 hrs min for a real gear head.;-) We diluted the discussion with the philosophy of modelling within the rules so we are certainly not gearheads.

advocate, consider yourself "lumped" ;-).

While mixed up with lots of things at the outset, the S Tank was considered faster to lay on than a Tank with a stabilized gun as they considered the post war stabilization inadequate and all tanks fired from stationary and they considered this was done faster with an S tank than a tank with a turret.

Somewhere on TMP there were links to the Brits assessment of the S Tank and the Swedes assessment of the Brits Assessment of the S tank. The Swedes assessment was the Brits were unable to work the way that was required to gain the advantages of the S tank. Its all an interesting study on the impact of stabilization, and systems design on recent post WW2 tank design.

emckinney09 Apr 2021 5:00 p.m. PST

"I think the greater concern is getting the gunner, with his limited vision and sights, to actually acquire a target/threat the TC may or may not have spotted."

That's why Creighton Abrams said that the M4's primary weapon was the commander's .50. If the commander spotted a target, his job was to put tracer down range so that the gunner knew where to look.

Of course, that was also why the commander had a turret rotation control … You point the turret in about the correct direction while the gunner spots!

Wolfhag09 Apr 2021 7:06 p.m. PST

I agree with Major Mike and emckinney.

Excerpts From M-4 Sherman at War by Michael Green and James M.Brown: Improving the Odds of Hitting a Target:To assist the gunner in combat, the 75mm main gun along with the .30 caliber coax machine gun featured a stabilizing system for both the gun and the sights. It allowed the gunner to fire his turret weapons when the tank was moving by keeping them at a predetermined vertical elevation accurate to within 1 mil of the target

The 1 mil is equal to about .5 meter at 500m.

In later versions, the gunsight was stabilized with the gun making it easier for the gunner to lay the gun on the target.

The Sherman had some features that not all tanks had. The TC has an override for the turret and a vane sight to help align the gun to the target. With a traverse speed of 25 degrees/second, he could be pointing at a target within seconds describing it to the gunner who has a panoramic 40 degree wide view roof-mounted periscope to quickly acquire the target. An order to stop is given and the stabilizer allows the gunner to keep the target in his sight and aim while the vehicle is decelerating. Crews were trained to execute this getting a shot off in less than 10 seconds.

The commander also had the option of laying the gun and firing it himself without the gunner's assistance. Having the gun battlesighted out to 600 yards would almost ensure a first-round hit up to that range which would have been typical for W. Europe. Lafayette Poole used this tactic often.

Unfortunately, games using IGYG and unit activations have a hard time simulating these features and tactics that made the Sherman "The Fastest Draw in the West".

Wolfhag

Wolfhag10 Apr 2021 1:33 p.m. PST

Just how fast was the Sherman?

Wolfhag

UshCha11 Apr 2021 2:52 a.m. PST

Its interesting that the topic although facination seems to be centered round the Sherman in WW2 one of the few WW2 vehicles to have a stabiliser and even then praised by few and switched off by many.

Technicaly the Crusader 2pdr was stabilised by the gunner and was indeed effective,having hit rates around 50% at ranges around 500yds on the move. This was a shoulder monted "harness" that the gunner could "iron out" movement with his body. It did not work beyond the 2pdrs as then the gun had too much inertia for a human body to damp.
It was really only Post WW2 that stabilisers of varuious standards became more common and of less limited use. Yet this has not recieved any attention in this topic. Not a compalint just interesting.

Wolfhag11 Apr 2021 8:04 a.m. PST

UshCha,
I've heard exactly the same thing. In my game, the 37-40mm shoulder-mounted guns get the benefit of stabilization but the 6pdr does not.

IIRC the British trained to shoot on the move with the Crusader. In N. Africa they were forced to shoot on the move to get within range to penetrate the Panzer III with the 2pdr gun.

Wolfhag

Andy ONeill12 Apr 2021 4:12 a.m. PST

The british and australians trained to fire on the move with their gunner-stabilisation.
The australians compared us mechanical stabilisation to their manual approach and their conclusion was the mechanical system was inferior.
There's a tiny minority of crews said they liked mechanical stabilisation.
As i understand it, the design intent was to allow faster acquisition after moving rather than shooting on the move.

The majority feeling seems to have been it was best removed or turned off.

Wolfhag12 Apr 2021 9:45 a.m. PST

Andy,

The australians compared us mechanical stabilisation to their manual approach and their conclusion was the mechanical system was inferior.

On which gun or vehicle?

There's a tiny minority of crews said they liked mechanical stabilisation.

Why did they like them and what advantage did they see?

If you are already on flat ground like a desert, a mechanical stabilizer would be a burden, especially if you have a shoulder-mounted weapon. If your tanks are moving at 10kph or less most of the time you most likely would not use a stabilizer even if you had one. If you were operating in a mountainous area like Italy I doubt if one would be useful. Since it takes up room in the turret the crews may think having more room is more of a benefit than a finicky device you only use occasionally even if it works as advertised.

I haven't found much info on the use of the stabilizer on the Grant and Lee. Some had stabilizers and some didn't.

Why didn't the US continue using them after WWII? I came across this:

It's not that the gyrostabilizer was ineffective, too complex or too expensive. In fact, the Westinghouse vertical stabilizer was very cheap, very simple and earned a very positive reputation, as it allowed the Sherman to fire the first shot due to stabilizing the gun when coming to a halt, and also allowed the tank to fire on the move with relative accuracy. Modifying it for larger guns was also not the issue, as only the hydraulics had to be changed the basic gyro unit was still the same.

In fact, Americans did perform tests of upscaled vertical stabilizers for the 90mm M3 tank gun. These tests were performed in 1944 on a T25 prototype a pilot prototype for the M26 Pershing tank. However, the brass eventually decided to halt any further development of the Westinghouse stabilizer. The reason was the stabilizer was vertical only and several US companies already started research of 2-axis stabilization systems.

This line of thought (aka to stop the development of the existing system and rather wait for a more advanced system) was then followed further even when the 2-axis stabilization was completed. At that point, the US Army representatives decided to wait until the 2-axis stabilization would be merged into a complete ballistic computer package. This resulted in the AOS upgrade for the M60A1 main battle tank, which was introduced in 1972 and gave the US Army the first tank with all-axis gun stabilizer, that was accepted into service.

I also ran across accounts of stabilizers being shipped without training manuals and leaders not wanting the troops to use them because the technology would fall into the hands of the Germans.

There appear to be many reasons why they were not used but when used by trained crews they did appear to give a tactical advantage when moving/attacking but probably not while waiting in the defense or moving alongside the infantry.

Wolfhag

Blutarski12 Apr 2021 5:02 p.m. PST

Jentz's book "Tank Combat in North Africa" discusses firing of shoulder controlled 2pdrs (elevation only) from moving tanks. Peacetime 1938 tests indicated that a tank advancing directly toward a stationary 8ft x 8ft target scored 14pct hits from 900 to 600 yards. No mention made of closing speed in this particular case.

B

Wolfhag13 Apr 2021 10:56 a.m. PST

More info:
link

This shows the Sherman difference between firing with and without a stabilizer on the move.

Wolfhag

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