PS Magazine - TB 43-PS-721

PS, The Preventative Maintenance Monthly

ISSUE 721

DECEMBER 2012
PS Magazine - TB 43-PS-721 - Page 7 of 33
10
PS 721
DEC 12
Dear Editor,
Would you please tell your readers not to bend the hooks on trailer
safety chains to fit the shackles on the back of FMTVs? You told us on
Pages 11-13 of PS 673 about NSNs for larger hooks and extensions for
the chains. That should’ve been enough to stop people from bending open
hooks, but we’re still seeing this in the field.
Robert L. Matson
ARFORGEN-LBE Specialist
TACOM LCMC
Fort Hood, TX
Editor’s Note:
Can do, Sir. To give you a little history, the FMTV manufacturer
increased the size of the FMTV’s tow shackles to meet new air transport and rail
tie-down requirements. When this happened, the tow shackles ±t the size and
weight of the FMTV trailer, but not the smaller hook size of the lunette trailers that
must be towed.
Instead of bending open hooks, follow these steps to ensure the trailer safety
chains are the right ±t:
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.
And here are a few special reminders:
When attaching to a truck that has no extended pintle, you’ll need to shorten the
trailer safety chains so they’re not too long and drag or get caught on underbrush
or commo wire. One way is to twist the chain several times to take up the slack.
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.
Consider this the latest and greatest guidance on this issue.
FMTVs and Lunette Trailers…
Hok-Up On Trailer
Safety Chain Hoks
Your lunette trailer or dolly set has a
3
/
8
-in safety chain.
Use these materials when your towing vehicle is an FMTV:
Hook,
Chain, NSN 4010-00-286-5645
Alternate
3
/
8
-in connecting link,
3
/
8
-in connecting link,
Length of chain extension to
be determined by user
Existing chain
too
small,
eh?
aw, man!
this hook is
too small!
there y’go!
thanks.
I…uhh.
there’s
no need to
thank me!
huh?
lemme
see
it.
721 10-11.indd
1-2
10/26/12
3:37 PM
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