Jounce & Squirm

[RHeadrick]

Does any one know what the specifications are or where I can get them from. (SAE, FMVSS) The # of the specs would be nice.

Thanks,
Bones

P.S. I have enclosed a link to the FMVSS 49CFR571 if any one is interrested. Free to view and Print sections from.

http://www.access.gpo.gov/nara/cfr/waisidx_05/49cfr571_05.html

 

[GregLocock]

Jounce is wheel travel in the upwards direction. Squirm sounds like a subjective descriptor - stability under braking maybe. Evaluators invent these terms and then they get written up and you have to live with the embarrassment ever after.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[reidh]

I have heard tire squirm referenced to when tires move side to side when they are not supposed to be. Like Greg said, I don't think there is a quantitative measurement for tire squirm.

Reidh

 

[RHeadrick]

Jounce & Squirm is a process in which you can test seats for your car, truck, class8 trucks or any seat. You can test other things if you want to know haw long it will take to wear a hole, rip the fabric and so on.

It is a test required by the FMVSS/SAE and others.

Sorry if the question was miss leading.

Bones

 

[MarkTEng]

I'm not sure that the test is required by the Feds and SAE only provides standards for best practices.
When I use to do the testing it was more for fabric and cushion durability evaluation/integrity and not an FMVSS requirement, those are safety standards and what you are looking for is more for durability and cosmetic evaluation.
Most of the specifications I used came from the seating suppliers, I did look quickly through the SAE standards and found nothing related to jounce and squirm, only H-point determination and vibration performance. It was a quick look and I had over 6000+ hits on the "seat" keyword.
If my memory serves me correctly, it has been 15 years since I did this test
The test involved using a butt form covered in 10# duck material that is loaded into the seat approaching downward at a 45deg angle with contact at the thigh and lat bolster, loading to some predetermined load, rotating to forward position, rotating back to exit position, and unloading out at 45deg.

 

[GregLocock]

Ah, that makes some sense. Yes we've got a rig for that test. Test method and targets would be company specific, but if it is for a truck then ask the seat supplier.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[RHeadrick]

Turczinator are you thinking of the Ingress/Engress test?

I would ask the seat suppliers but we are the seat suppliers.

 

[MarkTEng]

I guess I am talking about the ingress/egress test... It has been sometime...
Maybe the one your looking for is the loading of the butt form directly into the seat cushion, rotating it ±30°, and then removing the load. I vaguely remember a test being performed according to that method, I always worked on the MASTs for NVH issues and durability.
I find it surprising as a seat supplier you don't have an internal specification to work with and build upon.

 

[RHeadrick]

We go by OEM standards and each truck company is a little different. We had must of the jounce/squirm, mast, ect. was out sourced. In the process of building a new test lab with all state of art equipment. I'm trying to find out all I can about all the test.