Mike Clark

What a group of nice guys to pit next to at Sharon Speedway, Our deepest condolences for the loss of a team member and beloved brother.

Clark Racing #7

Just wanted to clear something up about impact forces. The equation for impact force is F=(1/2 x m x v²)/s. Where F=force, m=mass, v=velocity, and s=amount of crush on car.

So lets assume all of the cars we test have a crush of s=.5 ft.

Late Model 2350 lbs, and an average speed of 85 mph

Stock Car 3050 lbs, and an average speed of 75 mph

Late Model: F=(1/2 x 2350 lb x 85 mph(or 125 ft/s)²)/.5 ft = 3.67 x 10 ⁷ ft lbs/s²

Stock Car: F=(1/2 x 3050 lb x 75 mph(or 110 ft/s)²/.5 ft = 3.69 x 10 ⁷ ft lbs/s²

So as you can see the force of impact is basically the weight of the car multiplied by the speed, which in the example above the forces are very similar.

Also there are many things to consider in roll cage design: using correct triangulation the placement of much lighter bars can be much stronger then heaver bars.

Also you have to consider welded seam tubing verses DOM verses Chromoly. Chromoly being much stronger alloy then standard alloys.

You must also consider that bigger diameter tubing is much stronger, for example: 1.750" diameter by .065" wall thickness has a section modulus of .139 and 1.500" diameter by .095" wall thickness has a section modulus of .138. As shown they are almost identical in terms of strength.

Therefore there are several things to consider when a tech guy looks at a roll cage and tries to determine its safety, it would be virtually impossible without knowing what material was used and its thickness, let alone having a full understanding in roll cage design. That is where the big name chassis builders use CAD and Finite Element Analysis to determine actual strengths. But for that stock car guy who builds his own chassis they just needs to research a little and learn a few basic principles to build a safe roll cage. 

My thoughts and prayers to the Henry Family. 

This is a picture of Jim in his last car that he drove. Jim and my dad were partners for a couple of years in the mid 80's, and he won the track championship that year at Sharon in the semi-late division. Jim was and excellent chassis man and a very smooth fast driver who was rarely in trouble. RIP my friend.