Description
1969 U.S. Army M21 Huey Matched Worm-and-Worm-Wheel Gear Set, P/N 7792604, FSN 1005-973-3671
Item Overview
This original U.S. Army matched worm-and-worm-wheel gear set was used in the left- or right-hand mechanical-drive assembly of the M21 helicopter armament subsystem fitted to UH-1B and UH-1C Huey helicopters.The set contains three related gear components identified as Items 61, 69, and 94 in Figure 33 of Army Technical Manual TM 9-1090-202-35P. Part number 7792604 identifies the complete matched set, not one individual gear.
All three pieces carry the matching control marking SET-1322-12. They should remain together and should not be mixed with components from another gear set.
Identification and Features
- Official nomenclature: Gear Set, Worm and Worm Wheel, Matched
- Original Federal Stock Number: 1005-973-3671
- NIIN: 00-973-3671
- Complete-set part number: 7792604
- Set-control marking: SET-1322-12
- Number of components: Three
- Manual reference: TM 9-1090-202-35P
- Illustration: Figure 33, Items 61, 69, and 94
- Application: Left- or right-hand mechanical-drive assembly
- Parent system: M21 helicopter armament subsystem
- Associated aircraft: UH-1B and UH-1C Huey
- Package date: September 1969
- Status: Inert mechanical military surplus
Stock-Number Information
The original package is marked 1005-973-3671. This is the earlier Federal Stock Number issued when the set was classified with weapon-related components under Federal Supply Class 1005.
The 9/69 package marking records a September 1969 packaging date.
How the Gear Set Worked
A worm-and-worm-wheel arrangement uses a screw-shaped worm to turn a toothed wheel. This design changes the direction of rotary motion while providing gear reduction and controlled movement. Inside the M21 mechanical-drive assembly, the matched gears transferred motion through the gun-mount drive. Their fitted tooth surfaces helped maintain proper gear contact, backlash, and smooth operation. Because the components were fitted and supplied as one matched set, replacing only one piece or mixing parts from different sets could affect how the gears mesh. The shared SET-1322-12 marking identifies these three pieces as belonging together.
Historical Background
The M21 was a major U.S. Army helicopter armament subsystem of the Vietnam War. It equipped UH-1B and UH-1C Huey gunships used for close support, armed escort, reconnaissance, and attacks against ground positions.
The system combined paired 7.62mm M134 Miniguns with seven-tube 2.75-inch rocket launchers. Mechanical-drive assemblies controlled the movable gun mounts and allowed the weapons to be aimed during flight.
Gear sets such as P/N 7792604 worked inside these drive assemblies. Although rarely visible once installed, they were important to the controlled movement and dependable operation of the gun mounts.
The September 1969 package date places this set within the active Vietnam War service and supply period for the M21-equipped Huey gunship.
Condition
This is an original three-piece military-surplus matched gear set in period packaging. The gears may show old preservative, storage residue, discoloration, light oxidation, scratches, or other signs of age.
The original package may have fading, stains, creases, tears, handwriting, or shelf wear. Operational condition has not been tested or guaranteed.
The three components are supplied as one matched set and should remain together. This listing is for one gear set only. The mechanical-drive assembly, housing, motor, gun mount, M134 Minigun, rocket launcher, helicopter, and other parts are not included unless specifically pictured or stated.
Ideal For
- UH-1B and UH-1C Huey restoration projects
- M21 helicopter armament-system displays
- M134 Minigun mount research
- Vietnam War aviation collections
- Military mechanical-drive collections
- Original military packaging collections
- Museums and educational exhibits
Approx length 13", Approx width 7", Approx height 5", Approx weight 6.4 lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item’s general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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