Skip to comments.The FReeper Foxhole's TreadHead Tuesday - M551 Sheridan Light Tank - Jul. 20th, 2004
Posted on 07/20/2004 12:02:28 AM PDT by SAMWolf
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Airborne Assault Vehicle
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.
Brigadier General James H. Doolittle, USAAF
Poses beside an Army Air Forces recruiting poster alluding to his April 1942 bombing raid on Japan. Photograph was taken circa 1943.
Official U.S. Air Force Photograph.
My Uncle's family was a relative of Jimmy Doolittle. I in inherited many pictures of my aunt and uncle standing in front of the Doolittle headstone.
Not to be mean but when is Memphis not hot and muggy in the summer:-)
Thanks for the pancakes maybe I will get some energy to work on the house so I can get finished...
or maybe I will just go back to sleep
Good luck with the AC, I used to do some HVAC work sorry i can't be of any further help
On This Day In History
Birthdates which occurred on July 20:
1304 Francesco Petrarch Italy, poet (Italia Mia)
1519 Innocent IX 230th Roman Catholic pope (1591)
1785 Mahmud II Ottoman sultan, Westernizer, reformer
1824 Alexander Schimmelfennig, Prussia, Brig General (Union volunteers)
1890 Theda Bara actress/vamp (Under Two Flags, Cleopatra) (or 0729)
1890 Verna Felton Salinas Calif, actress (Hilda-December Bride)
1919 Sir Edmund Hillary one of 1st 2 men to scale Mt Everest (namesake of the EX firstlady)
1920 Elliot L Richardson Attorney General (1973)/Sec of Defense (1973)
1924 Thomas Berger US, novelist (Vital Parts, Little Big Man)
1933 Nelson Doubleday publisher (Doubleday)/owner (NY Mets)
1938 Diana Rigg Doncaster England, actress (Emma Peel-Avengers)
1938 Jo Ann Campbell Jacksonville Fla, Lawrence Welk's champagne lady
1938 Natalie Wood [Natasha Gurdin], SF, (Gypsy, Rebel Without a Cause)
1939 Judy Chicago [Cohen], Chicago, artist (The Dinner Party)
1940 Tony Oliva ball player, batting champ (AL Rookie of Year 1964)
1941 Vladimir A Lyakhov cosmonaut (Soyuz 32, T-9)
1943 John Lodge bassist (Moody Blues)
1947 Carlos Santana Mexico, musician (Santana-Black Magic Woman)
1957 Donna Dixon Va, actress, Mrs Dan Ackwoyd (Couch Trip, Bossom Buddies)
Good Morning Ernest_at_the_Beach. Looks like we had a quite a late night crowd.
Good Morning Ernest_at_the_Beach. Looks like we had a quite a late night crowd.
There's a tagline in there somewhere.
Morning E.G.C. We've had a long spell of hot and not too humid. I'm ready for a break.
IMHO the Sheridan just didn't know what it wanted to be.
Airborne Assault Vehicle
Even the name is confusing. :-)
No one is beyond the reach of Gods love.
You know, deep down, I know that's true but there are some people I just can't see even God loving.
Yes the ammo was a major problem. Not only could the shell casing catch fire from initiation from the outside, it was quite fragile and had a tendency to break up. The same system was on the M60 A3 tank. The idea was good but it just didn't work.
If the Army wanted a gun/missle launcher, I always felt they should have developed something around a recoiless rifle such as the 106mm Recoiless. They may have had to go to a bigger bore, but it would have given the infantry a weapon that could have been mounted on a jeep or whatever that could fire a long range missle at a tank or a conventional shell act a bunker. This would have been a lot more cost effective than firing a TOW or Dragon at some guy hiding behind a pile of sand.
Actually they could have used the 106mm or 90mm by the use of an over caliber missle with the gun providing the initial launch. This would have been a rocket assisted, recoiless rifle, guided missle. If you want to see a smaller of version of this, behold the RPG 7 which is exactly a rocket assisted, recoiless laucher.
my central air is OUT, and the AC man says I need a new unit
It figures. :-(
AKA the "Shank" and not in a complimentary manner.
I wonder if anyone ever had anything complimentary to say about the M551.
If you really want to get to bin Laden, infect his camels and goat heard with Aids.
LOL! Love the poster!! Never saw that one before.
A "hot & humid" Morning to you!
I walked out this morning and it felt as hot & humid at 08:30 as it did at 3PM yesterday..... Gonna be an egg fryer today.
Well in the M551's defense, when it first came out, we all thought it looked kind of neat, but I guess that's about it.
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