Helmet to rollbar clearance

What kind of clearance do you guys shoot for between your helmet and the rollbar? Is it better to be closer to the bar or farther? I'm mainly looking at the center overhead bar in the SLC at the moment.

Thoughts? Good links on the subject?
 

Terry Oxandale

Skinny Man
There is a minimum for most sanctioning bodies. Ed hit it pretty close to what most require, and thus a good reference for any use of one.
 
Ed and Terry thank you for your input!

I read the rules for NASA and SCCA:

NASA: https://nasa-assets.s3.amazonaws.com/document/document/282/2016.5.pdf

SCCA: http://sports.racer.net/docs/rules/2002/sect_18_roll_cage_and_chassis_2002_gcr.pdf

NASA has no minimum distance specified and SCCA specifies a minimum of 2" from driver helmet to main hoop. Distance to main hoop isn't really an issue for the SLC though, it's the halo bars running down the middle and neither rule book has anything to say about that.

Reading these rules I can't help but think that they're really designed for production type cars with traditional square looking cages. A DP type car with an egg shell design roll cage is going to have very different dynamics.

Ultimately I don't really care what any of these club rule books say as I'm only planning to do open track events where the bar is set much lower (no pun intended LOL) But I'd like to understand a little about the design theory so I can set things up to have reasonable safety. I'm sure some of you have thought about this and I'd like to hear more.
 

Terry Oxandale

Skinny Man
The halo design inherently offers the advantage of not needing the margin under the top of the main hoop tube (due to the imaginary line between the main roll hoop, and the front framing structure at the front of the chassis, where the helmet must stay below). With the halo, that margin is not necessary due to the front hoop.
 
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