AB-1386~U

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Description

AST AB-1386/U - NSN 5985-01-381-6341

Total mast height is variable from 8.3 to 33.1 ft (2.5 to 10.1 m) with all mast sections fully deployed. Accessories are provided to assist with guying, anchoring, and operating the mast in its ground mount configuration. They include a hammer, a tripod, guy assemblies, guy stakes, baseplate stakes, crank handle, baseplate, and a radius rope.

Two mounting kits may be used to adapt the HMMWV and the tracked vehicle with brackets and hardware to deploy the mast. The mounting kits are used to anchor the mast to the vehicle and to stabilize the mast when deploying it under normal conditions (i.e., winds below 25 mph [40 kph]).

Ab-1386-1.png Ab-1386-gearbox.png Ab-1386-gearbox-2.png


Common problems

No gearbox, or inoperable gearbox

If the gearbox is missing, this tower can still be used. you simple remove the drive screw and manually extend the tower. You will need something to place between the last section to hold it up, or a pin to prevent it from collapsing. The process for removing the drive screw is detailed in the TM linked below.


Section will not collapse

The tower is designed so that the sections cannot collapse until the one below it is fully down, there is a small toggle inside the "lock" where the "post" unlocks the next section. If for some reason the "post" engages but does not unlock the next section, use a flat screwdriver to toggle the lock and the section will unlock.


Frozen Bearing

Gearbox with Old Bearing
Gearbox with New Bearing

Upon removal there is a large bearing, I had to replace this, as mine was frozen up. the proper replacement bearing is a Koyo #62052RDC3. You will need a press to do this..

New bearing with old backing and bushing
  1. Remove the bearing from the housing
  2. Lightly tap the bearing while holding the outer ring to remove it (the one with the notch)
  3. Place the bearing in the press or suitable jig, and knock the brass bushing out from the rear.
  4. Remove the aluminum backing is attached to the bearing in the center, this wasn't meant to be re-used, so you will have to cut the bearing from around it. I tried using different pullers, but the aluminum will bend and deform, before the bearing is removed.
  5. Once this is cut off you can press this into the new bearing and re-install it.
Pressing new bearing onto the aluminum backing


Crank turns, but won't raise or lower the tower

This is usually due to the output shaft notch no longer being tight. When the crank shaft is turned, this also turns inside the saft and wont turn the large screw on the tower.

To test this, put a screwdriver in the output shaft, and attempt to hold the shaft in place while turning the crank, if you can turn the crank, and the screwdriver doesn't turn, you have confirmed it.

I attempted to resolve this many ways,

  1. Dimpling the edge of the shart to make the notch tight
  2. JB Weld
  3. Wedging it by taping it fron the back
  4. Welding

Welding was the only one that worked. What you dont want, which i was privileged enough to experience, is to get the tower up, then have this loosen up again, and have no way to lower it. Weld it, you don't want this problem.. trust me.

Arrows pointing to new welds



Other Images

Gear Box Images


Truck Pictures

Additional Files

Adobe PDF icon.png TM 11-5985-426-12&P

OPERATOR'S AND UNIT MAINTENANCE MANUAL INCLUDING REPAIR PARTS AND SPECIAL TOOLS LIST EQUIPMENT DATA
MAST AB-1386/U (NSN 5985-01-381-6341) (EIC:N/A)
OPERATOR PMCS WITH ELECTRICAL EQUIPMENT MOUNTING MT-6967/G (NSN MT-6968/G (NSN 5975-01-390-9612) (EIC: N/A)