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The FReeper Foxhole's TreadHead Tuesday - M551 Sheridan Light Tank - Jul. 20th, 2004
afvdb.50megs.com ^

Posted on 07/20/2004 12:02:28 AM PDT by SAMWolf



Lord,

Keep our Troops forever in Your care

Give them victory over the enemy...

Grant them a safe and swift return...

Bless those who mourn the lost.
.

FReepers from the Foxhole join in prayer
for all those serving their country at this time.


...................................................................................... ...........................................

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152mm Gun-launcher
Armored Reconnaissance
Airborne Assault Vehicle
M551 Sheridan




As can be surmised from the designation, the M551 Sheridan was intended to fill a multitude of roles. It was a light airdroppable tank, a reconnaissance vehicle, and was able to take on enemy armor thanks to its 152mm combination gun/missile launcher. The driver's hatch was unusual in that it rotated around the driver on a vertical axis, while the commander's cupola hatch and loader's hatch were more conventional. M551's hull was ringed by a lightweight structure filled with closed cell polystyrene foam for buoyancy, and a flotation screen could be raised to allow the vehicle to float across water obstacles. There were four smoke grenade launchers on either side of the turret which were supported by a brace on early vehicles. Early M551s had a turret ventilator dome on the left rear side wall; this was moved to the turret left front on later Sheridans.


The M551 Sheridan, from just off the assembly line at the Cleveland Tank Plant


The original M81 152mm gun-launcher on the M551 was equipped with a bore evacuator and an open breech carbon dioxide scavenging system, which was composed of two jets that blew CO2 into the open breech after firing to get rid of any remnants of the combustible case ammunition. However, this system also blew any burning pieces of left over combustible cases around the turret, which was unpleasant for the crew and deadly with the rest of the ammunition around. A closed breech scavenging system (CBSS) was developed by Allison to remedy this problem. CBSS blew any remaining pieces of the ammunition out of the weapon while the breech was still closed. CBSS was first installed on M551 number 700, and retrofit kits were developed for the previous vehicles. In vehicles with CBSS, ammunition stowage was reduced to a total of 29 rounds and missiles since one of the air cylinders replaced an ammunition rack.



The 152mm gun-launchers differ in the following ways: M81 was fitted with a bore evacuator and the open breech scavenging system; M81 Modified was an M81 retrofitted with the CBSS; M81E1 had a shallower missile keyway to reduce firing stresses on the barrel, and the barrel was thickened near the muzzle. When CBSS was introduced, the bore evacuator was omitted from new-production gun-launchers.

The MGM-51 Shillelagh missile was a SACLOS infrared-guided missile fitted with a shaped-charge warhead. MGM-51B extended the maximum range to 3km from the MGM-51A's 2km, and the MGM-51C was fitted with a shorter key compatible with the M81E1 gun-launcher. Sheridans 140 through 223 and 740 through 885 were produced without the missile guidance hardware.



In early 1972, laser rangefinders AN/VVG-1 were fitted to the commander's cupola, and the transceiver replaced the forward vision block. The rest of the laser rangefinder was mounted behind the commander, and a cable cover ran around the right side of the cupola from the transceiver to the rear of the TC's position. Sheridans fitted with the laser rangefinder were designated M551A1. M551A1s also replaced the gunner's M127 sighting telescope with the M127A1, which provided protection against laser light, and the cupola could be aligned with the main gun-launcher automatically.

In early 1989, the tank thermal sight from the 105mm gun tank M60A3(TTS) was also fitted to the M551A1. These vehicles were known as M551A1(TTS).



This view shows the M551's unusual driver's hatch in the open position. The hatch rotated around the driver, removing the need for an adjustable-height seat for open-hatch operation, and also eliminating the worry of turret rotation over the driver's exposed head. The black container on the hatch to the mannequin's right is the periscope washer fluid reservoir. The smoke grenade launchers on this vehicle are mounted in a line, however the original design featured a metal bar mount that ran under the grenade launcher assemblies.


(Picture taken 1 Dec 1990 by Spc. Henry; available from the Defense Visual Information Center.)


The gun-launcher on this M551A1(TTS) lacks a bore evacuator, so this vehicle is equipped with the closed-breech scavenging system. The guidance unit for the Shillelagh missiles is mounted above the base of the gun-launcher. The commander's weapon station has been fitted with armor protection, and additional machine gun ammunition could be stowed around the circumferance of the turret. The laser rangefinder transceiver is visible just above the spare ammunition box, and the cable cover runs around the right side of the cupola. The smoke grenade launchers are mounted over the brackets for the older style grenade launchers, which had four tubes on each side of the turret mounted linearly instead of clustered. One-hundred fifty-two millimeter ammunition is stored with protective bags around the combustible cartridge case; the bag is removed before firing.


The surf board is in the fording position and the swim screens, stored in chambers running along the upper edges of the hull, are fitted together. It wasn't pretty but it met the Army requirements.


The M551 Sheridan tank was designed in the early 1960's, as a need arose for U.S. forces needing a light tank. Constructed of aluminum armor, it is extremely fast, using a 300 hp Detroit Diesel engine and cross drive transmission. It mounts a steel turret and an aluminum hull. It was air transportable and fully amphibious with the screen around the sides raised. The main gun fired a 152mm standard projectile or a missile. It packed a lot of punch for a small tank. A similar gun was also used on the M728 Combat Engineer Vehicle. It is equipped with nuclear, biological, and chemical protection for the crew of four men. This enables it to fight in almost any climate or situation. The vehicle has seen combat use in Vietnam, Panama and Desert Storm, and it is used today for training in the California desert by the Armored Force Opposing Forces training center. Weight is 34,900 lbs. Top speed is 43 mph. It was built by the Allison Division of General Motors.



The M551 Sheridan was developed to provide the US Army with a light armored reconnaissance vehicle with heavy firepower. The main armament consists of an 152mm M81 gun/missile launcher capable of firing conventional ammunition and the MGM-51 Shillelagh antitank missile (20 conventional rounds and 8 missiles). Due to problems with the gun-tube-launched antitank missile, the Sheridan was not fielded widely throughout the Army. The gun would foul with caseless ammuniton, gun firing would interfere with missle electronics, and the entire vehicle recoiled with unusual vigor when the gun was fired, since the 152mm gun was too big for the light-weight chassis. The Shillelagh missles were evidently never used in anger. In addition to the main gun/missile launcher, the M551 is armed with a 7.62mm M240 machine gun and a 12.7mm M2 HB antiaircraft machine gun. A Detroit Diesel 6V-53T 300hp turbo-charged V-6 diesel engine and an Allison TG-250-2A poweshift transmission provide the Sheridan's power. Protection for the four-man crew is provided by an aluminum hull and steel turret. Although light enough to be airdrop-capable, the alumninum armour was thin enough to be pierced by heavy machine-gun rounds, and the vehicle was particularly vulnerable to mines.



Initially produced in 1966, the M551 was fielded in 1968. 1,562 M551s were built between 1966 and 1970. The Sheridan saw limited action in Vietnam, where many deficiencies were revealed. The missle system was useless against an enemy that employed tanks, though the Sheridan saw a lot of use towards the end of the war because of its mobility. Sheridan-equiped units participated in Operation Just Cause in Panama (1989), and was deployed to Saudi Arabia during Operation Desert Shield. As projectile technology advanced, the Sheridan's potential declined and it was phased out of the US inventory beginning in 1978. The M551 was last used by the 82nd Airborne Division. Some 330 "visually-modified" Sheridans represent threat tanks and armored vehicles at the National Training Center in Fort Irwin, California.



The engine for the M551 was a General Motors 6V53T, V-6 cylinder, supercharged, 2-stroke diesel engine. It produced around 300hp at 2800rpm and could push the AFV at over 43mph on level roads. The 158gal of diesel could fuel the Sheridan for 350 miles between fill ups. The white transmission is seen to the right in this photo and is at the rear of the engine. This left side view shows the radiator and cooling fan to the left in the picture, the cylinder head cover along the top and exhaust manifold covered with foil insulation along the side. The canister mounted upright on this side, near the top/rear of the engine, is the coolant surge tank and the other cylinder seen horizontal behind it is the supercharger. Down below is the cylindrical oil filter and the engine breather drain connection is at the very bottom of the block.


National Training Center M551 Sheridans


Initially, the power plant had problems with over-heating and its huge plume of black diesel smoke ("rooster tail") was a burden for the vehicle's primary role of recon. A later Product Improvement Program (PIP) decreased the smoke signature by adding a throttle delay feature and exhaust deflector. The original aluminum alloy engine block that was prone to heat warping was also replaced with a cast iron block that eliminated that problem.



TOPICS: VetsCoR
KEYWORDS: armor; freeperfoxhole; m551; mgm51shillelagh; sheridantank; tanks; treadhead; veterans; vietnam
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To: Valin
1944 Von Stauffenberg fails on an attempt on Hitler's life

After Adolf Hitler, Hermann Goering and Heinrich Himmler had been assassinated, it was planned for troops in Berlin to seize key government buildings, telephone and signal centres and radio stations.

At least six attempts were aborted before Claus von Stauffenberg decided on trying again during a conference attended by Hitler on July 20, 1944. It was decided to drop plans to kill Goering and Himmler at the same time. Stauffenberg, who had never met Hitler before, carried the bomb in a briefcase and placed it on the floor while he left to make a phone-call. The bomb exploded killing four men in the hut. Hitler's right arm was badly injured but he survived the bomb blast.

The plan was for Ludwig Beck, Erwin von Witzleben and Friedrich Fromm to take control of the German Army. This idea was abandoned when it became known that Adolf Hitler had survived the assassination attempt. In an attempt to protect himself, Fromm organized the execution of Claus von Stauffenberg along with two other conspirators, Friedrich Olbricht and Werner von Haeften, in the courtyard of the War Ministry. It was later reported the Stauffenberg died shouting "Long live free Germany".

As a result of the July Plot, the new chief of staff, Heinz Guderian demanded the resignation of any officer who did not fully support the ideals of the Nazi Party. Over the next few months Guderian sat with Gerd von Rundstedt and Wilhelm Keitel on the Army Court of Honor that expelled hundreds of officers suspected of being opposed to the policies of Adolf Hitler. This removed them from court martial jurisdiction and turned them over to Roland Freisler and his People's Court.

Over the next few months most of the group, including Wilhelm Canaris, Carl Goerdeler, Julius Leber, Ulrich Hassell, Hans Oster, Peter von Wartenburg, Henning von Tresckow, Ludwig Beck, Erwin von Witzleben and Friedrich Fromm, were either executed or committed suicide.

It is etimated that 4,980 Germans were executed after the July Plot. Hitler decided that the leaders should have a slow death. They were hung with piano wire from meat-hooks. Their executions were filmed and later shown to senior members of both the NSDAP and the armed forces.

41 posted on 07/20/2004 7:34:50 AM PDT by SAMWolf (This tagline does not require Micro$oft Windows.)
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To: U S Army EOD
Morning EOD

If you want to see a smaller of version of this, behold the RPG 7 which is exactly a rocket assisted, recoiless laucher.

I could never figure out why we never developed a decent equivalent to the RPG.

42 posted on 07/20/2004 7:37:08 AM PDT by SAMWolf (This tagline does not require Micro$oft Windows.)
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To: U S Army EOD
we all thought it looked kind of neat

Ok I'll give you that, I thought it looked kinda neat too. There's a novel called "Fire Arrow" about a major hostage rescue mission in Libya in which the M551 is featured prominently.

43 posted on 07/20/2004 7:41:44 AM PDT by SAMWolf (This tagline does not require Micro$oft Windows.)
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To: SAMWolf

Because the 90mm Recoiless is a better weapon. Of course we had the LAW and what ever replaced it.

If you are armed with an RPG then that is about all you can carry. With a LAW, everyone can carry one or two. If you want a dedicated weapon, you had the 90mm Recoiless.

When we went to the TOW and Dragon, we got rid of the 106mm and 90mm. This took away a cheap HE shell for the infrantry. We still could develop a laucher or missle that could be used with the 106mm or 90mm recoiless and give a cheap shell to shoot at cheap targets.


44 posted on 07/20/2004 7:45:11 AM PDT by U S Army EOD (John Kerry, the mother of all flip floppers.)
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To: SAMWolf
However on the other side, the M60 A3 tank with the 152mm gun/luncher looked kind of stupid. It definitely did not look as neat as its sisters with the 105mm.
45 posted on 07/20/2004 7:48:39 AM PDT by U S Army EOD (John Kerry, the mother of all flip floppers.)
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To: SAMWolf

Lets not forget Dietrich Bonhoeffer.


46 posted on 07/20/2004 7:58:39 AM PDT by Valin (Everyone is entitled to their own opinion. It's just that yours is stupid.)
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To: SAMWolf
IMPRESSIVE!


47 posted on 07/20/2004 8:37:17 AM PDT by Professional Engineer (The white gibberish on the blue screen says " Kill them. Kill them all!")
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To: U S Army EOD

IIRC the recoiless rifle was pretty popular around the Korean war.

The problem with the LAW was that it was a one shot weapon. The RPG is relatively cheap , very effective and reusable.


48 posted on 07/20/2004 9:02:45 AM PDT by SAMWolf (This tagline does not require Micro$oft Windows.)
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To: U S Army EOD
M60 A3 tank with the 152mm gun/launcher looked kind of stupid.

Yeah, it did look like some kind of bastard child. :-) Of course the M60 never really looked cool anyway.

49 posted on 07/20/2004 9:04:53 AM PDT by SAMWolf (This tagline does not require Micro$oft Windows.)
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To: Professional Engineer

That is a nice shot.


50 posted on 07/20/2004 9:06:03 AM PDT by SAMWolf (This tagline does not require Micro$oft Windows.)
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To: SAMWolf

An interesting idea that could have been made to work and work well it seems.
But what could have been done I have no idea..


51 posted on 07/20/2004 9:19:52 AM PDT by Darksheare (Show compassion, club a baby troll today!)
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To: bentfeather
I in inherited many pictures of my aunt and uncle standing in front of the Doolittle headstone.

Cool! Do you have any you'd like to share with us?

52 posted on 07/20/2004 9:25:25 AM PDT by Professional Engineer (The white gibberish on the blue screen says " Kill them. Kill them all!")
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To: SAMWolf
Sounds like a plan, but you know it'll never happen.

Guess not. I'm awake now. :-)

53 posted on 07/20/2004 9:26:08 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: Aeronaut

Morning Aeronaut.


54 posted on 07/20/2004 9:27:30 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: E.G.C.

Cool morning here in the Pacific NW.


55 posted on 07/20/2004 9:28:44 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: alfa6

Good morning alfa6.


56 posted on 07/20/2004 9:31:27 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: SAMWolf
(vehicles dispatched to Vietnam had the guidance system for their ATGW missiles removed)

What did I miss? Why were they removed?

57 posted on 07/20/2004 9:34:20 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: The Mayor

Psalm 27. A good prayer to use in the fight against the left that hopes to destroy us.

Good morning Mayor.


58 posted on 07/20/2004 9:38:13 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: GailA

Oh my. Might be a day to hit the mall or a movie to stay cool. Morning Gail.


59 posted on 07/20/2004 9:39:12 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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To: Professional Engineer

What a great poster! Thanks PE.


60 posted on 07/20/2004 9:39:59 AM PDT by snippy_about_it (Fall in --> The FReeper Foxhole. America's History. America's Soul.)
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