Metallurgist opinion needed please

[Double Venom]

Rodger,
Thank, and I seldom do.
DV

[LoBelly]

I'm sure you have something similar in the US but just in the nature of FYI...

page 6 of 8 shows the mounting requirements for street rods
http://www.infrastructure.gov.au/roa..._COP_sec_8.pdf

refers specifically to 'seat belt bolts'



And in case you're having difficulty sleeping - a UN approved standard
http://www.comlaw.gov.au/ComLaw/Legislation/LegislativeInstrument1.nsf/0/FA508A2DCB831686CA25716300227BE4/$file/ADR+5-05+[FINAL+FRLI].doc

to save you some pain - page 30 of 81 has this line buried in it...

'5.5.1. An anchorage shall have a threaded hole of 7/16 inch (20 UNF 2B).'

LoBelly

[Robert McLinden]

Having worked for some 40 years as a structural analysis on aircraft I agree with Rodger. For all critical applications (things you can get hurt from a failure) you should use at least AN Bolts (125ksi minimum). Make sure the "grip" is correct for the application. Try to avoid "bolt bending" as that can kill the fastener real quick. If possible upgrade to NAS level (160 - 180 ksi) for areas you are really nervous about.

For reference a AN4 (.25 dia) has a shear strength of 3680 lb and a tension strength of 4080 lb.

[Double Venom]

Man this is a great place, now we're even getting international guidelines! Problem with that info does not indicate what material the mounting substance is or needs to be!
If you thought that it would be 'legal' to fasten as shown and your floor is fiberglass- me thinks/knows it would fail.

But great stuff, I'm not sure if the U.S. even has guidelines like that? Somebody tell me I'm wrong...AND NSRA rules ARE only suggestions, they are not legislative rules/guidelines!
DV

[Don]

DV.........checked with SCCA Tech, reply was:

" I always recommend contacting the manufacturers of the seat belts for
specific mounting instructions."

Initially thought there would be a specification used during the inspection process.

[Rwillia4]

A grade 8 bolt is stronger in shear and tension than a grade 5.

A 1/2" grade 8 bolt has 5009lbs tension and 4470lbs shear strength...I'm not sure if I'm reading something different than others. http://www.rockcrawler.com/techrepor...ners/index.asp

[Double Venom]

Don,
At least they are consistent. They told me the same thing in '01

DV

[Don]

DV:

From the Simpson web site:

" Mounting brackets should be installed at an angle that is compatible with the direction of pull on the webbing under full load. Preferred mount is in a double shear with allowance for the bolt-in bracket to pivot and align toward the direction of the load as shown in Figure 1."

" Minimum specification for bolts and washers to attach the seat belts, harnesses and anti-submarine belt hardware are Grade 8. "

http://simpsonraceproducts.com/safet...ting-brackets/

GrassRoots Motorsports: Mentions follow the vendor specs, but no specifics on the bolts

http://grassrootsmotorsports.com/articles/black-belts/

[Double Venom]

Well it certainly looks like "Carol Smith" has been updated on the attaching hardware.
It does seem to be the consensus that grade 8 is the best choice. But, in agreement to some people here also 'in the know' AN is the ultimate bolt assembly for seat belts.

Now, not to start another debate but position of the shoulder straps also has some major grey areas.

NSRA / NHRA: Level to the shoulders to a maximum of 4"s below the shoulders. (This can be very tough in street rods!)

Simpson: Should have a downward angle?

All kinds of variations come into play here, I think a good dose of common sense falls into play here.

And, thanks to everybody- I learned a lot, including the right way!
DV

[Scoober]

bolts are an energy storage device like a capacitor or bungee cord. Normally bolts are used as really stiff springs to hold the parts together. Bolts will stretch a few thousands to creat clamp load. The part being clamped needs to be stiffer than the spring(bolt) to hold and not have a loss of preload wihich will cause self loosening. Tighten it too much and you will arrive in yield or permanent deformation. If you tighten to proof (about 80% of yield) and there is alot of vibration or thermal expansion will yield the fastener. Some belting type applications that I have experienced are a shoulder type bolt that will allow movement of the belt mounting bracket and the shoulder is contacting the secure surface. Maybe a tube over the bolt and inside the belt bracket is the way to go for movement type and a large hardened flat washer for non movement.

Grade 5 are more compliant, they will be more tollerant to extreme vibration than grade 8 will. Grade 8 is a bit more brittle but are stronger. Metric fasteners are typically stronger than SAE in the same sizes.

[Don]

Received an update from Simpson:

Good Afternoon,

Bolts should be grade 8 bolts.

Thank you,
Customer Service
Simpson Race Products
328 FM 306
New Braunfels, TX 78130