BTTM0416-01-1

SERVICE BULLETIN
TO REPAIR AND/OR REINFORCE EXISTING HANGAR TO
FRAME I BEAM JOINTS ON THE 20AC-51 TRAILERS

PURPOSE

Safety Precautions
Before making any modifications or repairs to a vehicle, make sure that the vehicle is properly supported with lifting or
support devices that have the correct capacity.

CAUTION

CAUTION

Personal protective equipment must be worn
when making vehicle repairs or modifications.
This includes, but is not limited to, safety glass,
steel toe boots and gloves.

Never depend on the axles and jacks alone to
support the vehicle when making repairs or
modifications. A vehicle that is not adequately
supported can fall and cause severe injuries or
death.

Note: If a 20AC-51 has a crack at the Ibeam joint, both scenario 1 procedure and scenario 2 procedure need to be completed. If a
20AC-51 doesn’t have any cracks at the joint location, then the scenario 2 procedure may be applied.

Joint location

20AC-51 side view

Lo

Lo

Location for all
Figures

SCENARIO 1:figures
CRACK IN I BEAM EXISTS AT AXLE/I BEAM JOINT.
LO required for install:
Parts
Part number
3040002

Description
FB 3 X ¼ X 10L

Qty
2

Scenario 1 Procedure
1.
2.
3.
4.
5.
6.
7.
Page 1 of 4

Drill 3/16" hole at the end of the crack to prevent
further propagation.
Lo
Weld a 1/4" bead across existing cracks. If there are web cracks, place these welds on the outside of the Ibeam/trailer.
Grind flush any raised welds if any of the new parts don’t make a full surface contact.
Leave a 1/2" gap between the bottom 12" Ibeam flange and part 3040002. Place part 3040002 (Figure 1) over web
crack location, on the web of inner Ibeam side of trailer, and run a 1/4" x 2"- 4" weld around the perimeter.
Inspect the welds for poor porosity, inadequate penetration, and verify that there are no cracks or undercuts.
Repeat steps 1-5 for the Ibeam on the other side.
Continue to scenario 2:
©Big Tex Trailers - 4/7/2016

20AC-51 JOINT REINFORCEMENT.docx

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3040002
FB 3 X ¼ X 10L

Lo

Figure 1

SCENARIO 2: SCENARIO 1 PROCEDURE IS COMPLETED OR TRAILER DOES NOT HAVE EXISTING CRACK. THIS
PROCEDURE CAN BE APPLIED TO REINFORCE A TRAILER WITHOUT A JOINT CRACK.
Parts required for install:

Lo
Part number
2970005
3060006(20AC-51)

Description
FB 1-1/2” x 3/16” x 16”
FB 4 X .25 X 16

Qty
8
2

NOTE: PART 3060006(20AC-51) MUST BE FORMED (BENT) WITH A 3/8" RADIUS BEND.
Scenario 2 Procedure
1.
2.
3.
4.
5.
6.

Page 2 of 4

Verify there is a full weld across the entire width of this joint before installing new parts(Figure 2). If there is not a full
weld, continue a ¼” weld to the edge of the flange.
Verify there is a ¼” weld 2” around the corner of the Ibeam flange on both sides(Figure 2). There needs to be a
continuous weld around the corner at this location on both the inside and outside.
Place parts at the locations shown in Figure 3 and Figure 4
Weld the parts according to Figure 5 and verify that there is a 2" weld on all sides at location A and the gap is filled at
location A.
Inspect the welds for poor porosity, inadequate penetration, and verify that there are no cracks or undercuts.
Repeat steps 1-5 for the Ibeam on the other side.

©Big Tex Trailers - 4/7/2016

20AC-51 JOINT REINFORCEMENT.docx

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Part 3060006(20AC-51) is hidden to show the existing
corner.

Verify there is a full weld across the entire width of this
joint before installing new parts. If there is not a full weld,
continue a ¼” weld to the edge of the flange.

Verify there is a ¼” weld 2” along the edge of the Ibeam
flange on both sides. There needs to be a continuous weld
around the corner at this location on both the inside and
outside.

Figure 2
Ibeam Joint
Cutaway front inside
view of Joint

Cutaway rear outside
view of joint
2970005 is flush with 12"
channel flange tip on outside.

Lo

Lo
Lo
Lowith 12"
2970005 is flush
channel web on inside.

2970005 is on the top of the “bottom Ibeam flange”
and on the bottom of the “top Ibeam flange.”

Lo

Page 3 of 4

©Big Tex Trailers - 4/7/2016

20AC-51 JOINT REINFORCEMENT.docx

Rev A

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Figure 3
View from inside

Figure 4
View from outside

Lo

Lo

Figure 5
Parts and welding callouts

Page 4 of 4

©Big Tex Trailers - 4/7/2016

20AC-51 JOINT REINFORCEMENT.docx

Rev A