ROLL CAGE INSPECTION HOLES

[ShadowBolt]

Do I need one in every bar? The CCR says "3/16" hole in all required bars".


JJ

[jeffburch]

If I had a new cage such as you, I wouldn't go drilling holes in it that won't be needed.

jb

[ShadowBolt]

Okay, JB says I don't need inspection holes. Gotta be right if the champ say it............Sounds good to me.

JJ

[Wirtz]

What I have done with new cars is take a drill and centerpunch with me to the first inspection to get the log book. The inspector may ask to check a few of the tubes, but I've never seen them want to check all of them. Mostly the main hoop and the main door bar, but it depends on who is doing the inspection.

Jeff

[y5e06]

I did similar. I drilled one inspection hole in the main hoop. I then also carried a 3/16 bit in the tool box just in case. never needed to drill another.

[GlennCMC70]

my cage does not have a single hole in it. i do however carry what i need to do so to every event.

[Al Fernandez]

An inspection hole is, according to the rules, required in every required bar. So, if a bar is not required to meet minimum standards, then a hole is not required. Of course as others have mentioned this is not something that scrutineers have been very consistent with.

There are inspectors that are not doing this at all because they are using ultrasonic thickness measurement devices. You could make a really good argument that even with that they should still use the holes to ensure the tubing is not ERW (ERW has a little ridge, or lip along the ID that you can feel using a bent paperclip). There are of course inspectors not paying enough attention to all of this.

Another way of looking at it is this: there is no structural loss to be concerned with IF you drill the hole somewhere other than that particular tube's highest stress areas. So, sure, carry a drill and a punch and be prepared...or just drill the thing and never worry about it. As long as your choice is away from the highest stress points, its a non issue. Stay away from tube ends, bends, midpoint.

[RichardP]

there is no structural loss to be concerned with IF you drill the hole somewhere other than that particular tube's highest stress areas.

I disagree with this. But I would also like to see more checking of this done in tech. Realistically, this is pretty low on my list of things that I would like to see checked but aren't.


The ultrasonic checking is cool. There were multiple cars at the Runoffs and ARRC found last year with under spec cages...


Richard P.

[GlennCMC70]

..... this is pretty low on my list of things that I would like to see checked but aren't. Richard P.

i'de be open to a list of things that are high on your list. send an email if you want.

[Al Fernandez]

Richard I thought you might object to my generality! 8)

A tube in a roll cage acts essentially like a fixed beam right? Therefore there are three basic types of stresses to be concerned about: shear, torsion, and compression (tension). Shear and torsion are not a function of the bar's length, but compression/tension will be since these are created by bending moments.

In general, in a tube in a roll cage, shear stresses and torsional stresses are much lower than compression and tension. Bending moments and compression loads translated into the beam trying to buckle result in the highest stresses being either at the ends or in the middle. Either way, if you avoid both then you will be avoiding trouble 8)

The fact is that stress is not uniform along cage bars. This is another reason why people make varying wall thickness tubes: try to save weight by tailoring the thickness to that required at that particular point along the tube.