Seemed like a reasonable response from an engineering standpoint to me.

Kevin

Some people over think this game and take all the fun out of doing it wrong the first time. Old Poly talks about 10 miles over my head but I’m sure he saves a few guys a few bucks so that’s a good thing.

actually , with (nice) bicycle frames it's similar concerns.
do you use 1"/1.125" tubes or the "oversize" tubes 1.125"/1.25" tubes with thinner butting. Likely you can gain significant stiffness with minimal weight penalty.

Yep, Poly is right. Once one starts thinking like an engineer it's hard to stop. He didn't indicate which choice to make.

His post seems to me to be mostly fact and not indicating a choice, only that there IS a difference. And yes, a cage made to optimize any of the three options would look different for each one.

Strengths of Materials is the one course I use most in my professional and personal life. Ron Apanian should be proud.

R.

My friends B body. Lots of clearance underneath and you don't have to work around a bar in the engine compartment.

A good cage at work. CM - the halo bar deflected about two inches - when the whole car landed on it during the barrel roll. Front supports from the cage to the front longitudinal under the fender. The roof was later cut off and the cage cut out of the car - only bar needing repair was the halo bar.

One place not to be cheap.

True.

Passing tech is the minimal accepted cage structure. Rarely is it adequate or sufficient for improving the car. And there's typically plenty of room for improvement of driver safety.

Safety is a given. We see people walk away from things like hitting the wall at high speed and the Stevie Jackson blow-over. Rarely these days do we see a tube car chassis/cab structure compromised. The structure is stiff and strong. Rule changes usually result from some unusual situation that we don't want to have happen again. The idea is to contain the driver in that protective structure. Recent improvements have been in driver gear - helmets, HANS, padding, shields, restraints. There is such a thing as an unsurvivable wreck. The body can only take so much G-force.

Chassis response/flex or the lack of it, is by design. Added or reduced tubing and tube sizing, bracing, diagonals, slip joints, while maintaining the requirements of the spec, can be used. Proper bracing is a more effective way of stiffening the structure. While they could, I don't know of anyone who uses 1.75" in place of 1.625".