PS Magazine - TB 43-PS-673

PS, The Preventative Maintenance Monthly

ISSUE 673

DECEMBER 2008
PS Magazine - TB 43-PS-673 - Page 8 of 33
12
PS 673
DEC 08
These steps will ensure
that the trailer safety
chains are the right size:
1.
Remove the current hook
and connecting link from the
forward end of the trailer
safety chains.
2.
Couple the trailer to the
FMTV at a 45-degree angle.
3.
Attach the new safety
chain hook to the FMTV
tow shackle opposite the
trailer angle.
4.
Cross the safety chain
under the trailer tongue.
Then pull the end of the
chain and eye or clevis end
of the new hook toward
each other.
5.
Measure the distance
between the eye or clevis of
the hook and the end of the
safety chain. Add the length
of one more chain link. That
will be the cut-length for the
extension chain.
6
The connecting link
joining the
3
/
8-in extended
chain to the original
3
/
8-in
chain will add the correct
amount of slack to the
safety chain without its
being too long or too
short. The same thing
applies to the
1
/
2-in hook,
two connecting links and
extension chains.
Note that when attaching to a truck that does not have
the extended pintle, you will need to shorten the trailer
safety chains so that they are not too long and drag or get
caught on underbrush, commo wire or other hazards. One
way is to twist the chain several times to take up the slack.
By the way, all but one model lunette trailer and dolly set
have
3
/
8-in safety chains. Only the M345 model has
1
/
2-in
safety chains.
All material listed in our solution have load limits that are as good as the
original equipment safety chains. We’ve confirmed that both listed hooks
fit the current FMTV tow shackles. Plus, all listed materials are available
through the Army’s supply system. Engineering, safety and the FMTV team
have all approved this solution.
Note that all other guidance and previous PS Magazine articles related to
lunette trailer safety chain length and hook size while FMTVs are the towing
vehicle don’t apply now. Disregard them and follow this guidance instead.
Gary Mitchell
Trailer Equipment Specialist
TACOM-Warren
Editor’s note:
You’ve just hooked our
readers up with some good information.
Thanks
!
If your towing vehicle is an FMTV and
your lunette trailer or dolly set has a
3
/
8
-in
safety chain, use these materials:
If your towing vehicle is an FMTV and
your lunette trailer or dolly set has a
1
/
2
-in
safety chain, use these materials:
Chain, NSN 4010-00-286-5645
Alternate
3
/
8
-in connecting link,
3
/
8
-in connecting link,
Chain, NSN 4010-00-149-5584
Alternate
1
/
2
-in connecting link,
1
/
2
-in connecting link,
Length of chain extension to
be determined by user
Existing chain
Length of chain extension to
be determined by user
Existing chain
1
/
2
-in connecting link,
Note that if you have an M105A3,
M101A2 or -A3, or a lunette trailer with
a surge brake device, you have to adjust
the length of the breakaway cable/chain.
Make it a bit shorter than the safety chains.
Then if the trailer disconnects from the tow
pintle, the breakaway cable/chain will fully
actuate the trailer brakes before the slack
in the safety chains is taken up.
673.12-13.indd
1-2
11/4/08
3:02:50 PM
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