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Posted on 07/20/2004 12:02:28 AM PDT by SAMWolf
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 are acknowledged, affirmed and commemorated.
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| Our Mission: The FReeper Foxhole is dedicated to Veterans of our Nation's military forces and to others who are affected in their relationships with Veterans. In the FReeper Foxhole, Veterans or their family members should feel free to address their specific circumstances or whatever issues concern them in an atmosphere of peace, understanding, brotherhood and support. The FReeper Foxhole hopes to share with it's readers an open forum where we can learn about and discuss military history, military news and other topics of concern or interest to our readers be they Veteran's, Current Duty or anyone interested in what we have to offer. If the Foxhole makes someone appreciate, even a little, what others have sacrificed for us, then it has accomplished one of it's missions. We hope the Foxhole in some small way helps us to remember and honor those who came before us.
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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.
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I can't believe this tank was created in the 60s and is now retired
It just wasn't very good, it tried to be too many different things and didn't perform any of them well.
Nice drawing Feather.
Amen!
I would have wanted my Model T to run faster, too. ;-)
M551 Sheridan of G Troop, 2/11th ACR bustin' bush in Hau Nghia province. Image courtesy of Doug Kibbey
In line formation with M551, G Trp., 2/11th ACR, Hau Nghia province '72. Image courtesy of Doug Kibbey, cmdr. M113 ACAV G71, 2/11th ACR.
Again from the early M551 TM, this photo shows the protective padded/fire proof asbestos bags added to the conventional rounds to help provide some protection. Each round was removed from the rack and both the asbestos bag and an inner neoprene liner bag stripped off before loading it into the G/L, obviously slowing the loading process greatly. By the mid 1970s a newer plastic bag was used as the cases were now redesigned stronger and more robust and did not require the extra padding of the early shell casings. This rack is the horizontal 5-round rack under the gun. One of the two CBSS air bottles is to the left.
By the mid 1970s most deployed Sheridans had the CBSS. However, many of them retained the older gun/launcher with the bore evacuator, known as the M-81. The newer tubes were the M-81A1. Also, many active unit Sheridans at this time were Viet Nam rebuilds, issued directly from Anniston Arsenal, including many with the older gun/launchers. Generally, the older G/Ls were replaced with newer ones only when they were worn out (from shooting) or condemned for other reasons. While the CBSS rendered the bore evacuator redundant (and an additional point for maintenance), the two types of g/ls were still interchangeable. If a Sheridan required a new tube, and if a plain ol' M-81 was available, that's what you got stuck with until they were depleted from the inventory through normal demand.
The Sheridan's last battle action was with the 3rd Battalion (Airborne), 73rd Armor of the 82nd Airborne Division during the Gulf War. When the M551A1(TTS) vehicles were finally placed in the battlefield position that they were originally designed to dominate, the long armed Shillelagh missile system killed Iraqi armor very well indeed. After taking over twenty five years to prove itself on the field of battle, the Sheridan weapon system was then quietly withdrawn from front line service just five years later.
From US M551 Armored Reconnaissance/Airborne Assault Vehicle, "Sheridan", Part 2, Revised 1/12/01
M551A1 TTS Armored Reconnaissance/Airborne Assault Vehicle "Sheridan"
In other news, former National Security Advisor Samuel "Sammy" Berger is the subject of a criminal investigation for having stuffed the plans for the Pentagon's new anti-gravity force-field-protected particle-beam-weapons infantry vehicle into his jacket, pants, and socks:
LOL! on that first picture. :-)
The Sheridan's last battle action was with the 3rd Battalion (Airborne), 73rd Armor of the 82nd Airborne Division during the Gulf War. When the M551A1(TTS) vehicles were finally placed in the battlefield position that they were originally designed to dominate, the long armed Shillelagh missile system killed Iraqi armor very well indeed.
After taking over twenty five years to prove itself on the field of battle, the Sheridan weapon system was then quietly withdrawn from front line service just five years later.
Another case of a weapons system being developed and then misused.
Hi Phil. Love the SuperAmerica photo. You've posted some great pictures and websites to go along with them. Thanks.
I hope they fry Berger!
BTTT!!!!!!
Sweeeeet ride you have there!
I agree with you about the HE round. From the battle descriptions I've read it would have come in handy in a lot of situations in Iraq but they had to settle for shooting HEAT at unarmored targets.
IMHO the main problem with the M551 was they didn't seem to know what role they wanted it to play. So it ended up a jack of all trades and master of none.
The M551 was the roughest riding SOB of a tank that I ever drove, and I've driven just about all of them with the exception of the M1 Abrams.
You'd hit a bump and the shock would travel right up your spine. I hated it.
Now the M60 rode like a Cadillac.
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