NHRA chassis tech-sonic weld tests
 

Im about to get a chassis certified and Ive heard that sometimes inspectors for NHRA will sonic test every peice on a chassis. What does this test do and what determines if it passes or fails? any other tips on passing chassis inspection? thanks Brian

Sonic tester measures thickness of roll bar tube. Say the spec on a particular bar is 0.125" or 0.083", for example.
If the tube thickness >= spec it passes. Thinner than spec it fails.

Inspectors also look for tube joints to be welded completely around (for example: at top of cage near headliner.) No grinding of welds. Gussets where required by rule book.

That's the basics. One of the members here is an NHRA tech inspector. Maybe he can fill in more details.

How fast is the car/ what certification are you looking for ? 8.50 to 9.99? 8.49 to 7.50? 7.49 and faster (1/4 mile times) There are new requirements to certify faster than 8.50 and 7.50 1/4 mile... ("funny car cage", SFI, etc.)

Why can't you grind the welds?

So they can see the quality of the welds or does grinding the welds affect them somehow?

one of the reasons they dont allow grinding of welds is so that they can see the quality of the weld

i realize that looks can mean little when it comes to strength, but in some cases its easy to look at a weld and say "wow, that has zero penetration"

if you cant make a decently smooth even weld around a tube, you shouldnt be welding together a safety cage

Well said, subject nailed, not that my affirming it matters, but I like to read post that are this accurate and informative..