Tire safety cage - design guide 1

[gasma1975]

Hi,

I have to design a tire safety cage, is there any design guide or minimum equivalent static force requirements ?

 

[MiketheEngineer]

Buy one

 

[gasma1975]

Good one! What if I want to understand how to design it and what exactly are the requirements?

 

[IRstuff]

You need to work for a company that does it for a living.

That's pretty much the only way. Books and nuggets from random strangers can only get you so far.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[gasma1975]

Actually its a manufacturer of safety cage who asked me to approve the structure. But like you said, I don't think you can calculate it on paper. It needs to be tested in real world controlled environnement and to see what exactly is the damage. As a structural engineer we design our beams to tolerate a minimum amount of deformation. But what I've seen on youtube, when a tire explode the cage has severe deformations, still it is not ripped appart, but it must be replaced. So I really cannot approve the design evaluating it only by hand calculation...

 

[IRstuff]

There ought to be a way to do this analytically. Most buildings designed for earthquake resistance are designed to deform, but not collapse, and they obviously don't build and test a real building. They might, perhaps, build and test scale models. For example, they might test wire mesh to see what impact speeds and materials result in deformations, but no penetrations.

A similar approach is taken with ballistic armor. Sample pieces are tested against various ammo/speeds and a physically-based analytical model is used to do the actual design.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[Ron]

My guess from the sketch in your other posting, is that Martins Industries has asked you to "certify" their cage for a customer, since their drawings have a caveat that the cages are not engineer approved but available upon request.

As several noted in the other thread, this is not likely calculable with any degree of predictability or accuracy. Proof testing is indicated for this type of venture.

As an engineer, it is perfectly valid for you to design the test, observe the test, then validate (I would be careful with the term "certify") the efficacy of the device through the testing program. Keep in mind that the testing program should include several repetitions and should include both the structural impact testing for rim impact and debris containment testing for tire rupture.

 

[GregLocock]

In the absence of test data you could estimate the maximum projectile mass and momentum, and then use a crash testing FEA like say LS DYNA, which can give very good results in the most non linear of situations. BUT this would cost what would probably seem like a fortune to do properly, and without experimental data behind it is more like a saturday morning cartoon than an engineering analysis.

Presumably these things are certified as safe for a certain maximum tire size and pressure, time to blow up (both meanings) a few tires I reckon.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[IRstuff]

There are lots of designs that involve controlled failure. Every new car that's designed with crumple zones were designed in FEA, otherwise, they'd be crashing a truckload of cars, which they obviously don't.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[Ron]

without experimental data behind it is more like a saturday morning cartoon than an engineering analysis.

nicely stated and accurate, Greg! Does ACME make these things?

 

[S275]

I agree with IRstuff about using FEA, it can be very helpful for your case.

Good luck

 

[MikeHalloran]

I could swear that SAE used to have a standard, but I couldn't find a trace of it.


29 CFR 1910.177(d)(3)(i) provides a load case, sort of.
full text:

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9825

Note that 1910.177 does not apply to LT and smaller tires, though conformance is claimed universally.

an interpretation of interest:

http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_id=19585&p_table=INTERPRETATIONS

Mike Halloran
Pembroke Pines, FL, USA