Chevy response to LATCH anchor question.

A

anpgorrell

Guest
Chevy response to LATCH anchor question.

A friend referred me to this forum for help deciphering an answer I got from Chevy when I asked what my LATCH anchors were tested to, as the manual to my Britax Marathon states not to use the LATCH attachments with a child weighing more than 48 lbs, unless the vehicle manufacturer says they are tested higher. The answer that Chevy gave me is very thourough, but not being an engineer I don't really understand it. Can someone help translate this?

Thank you,
Amanda--CPS Tech and mom to 2
*******
Regarding the weight that was used to test the LATCH bar in your 2001 Chevrolet
Venture, please note below:

Each lower anchorage would be tested separately by applying a force of 5,300 N
(1,190 pounds) to the anchorage in the forward horizontal direction parallel to
the vehicle's longitudinal axis. The force would be applied by means of a belt
strap that is fitted at one end with hardware for applying the force and at the
other end with hardware for attaching to an anchorage or connector.

The force would then be applied so that the 5,300 N (1,190 pounds) force is
attained within 30 seconds, with an onset rate not exceeding 135,000 N (30,337
pounds) per second, and would be maintained at the 5,300 N (1,190 pounds) level
for at least 10 seconds. When tested in this manner, no portion of any
component attaching to the lower anchorage bars shall move forward more than 125
mm (5 inches), and that there shall be no complete separation of any anchorage
component.
 
C

CPSDarren

Guest
Thanks, Amanda-

I am hoping to update my LATCH page with this information and other information I hope to get at Lifesavers and the Auto Show this year.

The NHTSA standards were apparently based on testing of the 4 year, 48 pound dummy in a 17 pound seat, and also some with the 3 year, 33 pound dummy in a 32 pound seat. That appears to indicate that a combined weight of about 65 pounds is certainly within limits for the lower anchors. There is also a safety margin above that based on the standards, and the auto makers may add another margin above that for liability reasons. I believe the testing is done without a top-tether, so top-tether use would add even more of a safety margin. Plus, as you read, the test is not for a complete failure, only for a certain yield of the bar to some bending point. There would presumably be a bit more margin above that for complete failure.

How much more all these margins add is the question, and no one seems to have that answer for most vehicles... Top-tether ratings are a similar issue.

Darren
 
U

UlrikeDG

Guest
But what does it *mean*?

They told her how many pounds of force the anchors were tested with, but what she needs to know is how many pounds of child will they hold?
 
C

CPSDarren

Guest
Re: But what does it *mean*?

Well, you can speculate given the standard crash test speeds and the rated forces but the result could potentially cause someone to disregard the recommended 48-50 pound limits. The crash tests are done for up to a combined weight of 65 pounds, so that is the only definitive answer there is right now. Anything else would be speculation on how much of a safety margin there is above 65 pounds, unless it comes directly from the automobile manufacturer. GM's response appears to be taken almost verbatim from FMVSS 225 and doesn't offer any more insight...
 

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