Quote:
Originally Posted by cosmick
You can do yours however you feel safe. Me, I see that new mass produced cars are designed to have a rigid occupant enclosure with crush zones before and aft. But the bumpers themselves mustn't crush. (State law for DIY vehicles.) So I can do likewise. Besides, the thinner the steel, the more difficult to weld.
|
There's nothing wrong with the concept but take a look at the section and wall thickness of those cars (with safety cages). They're not even close to equivalent to 2"x2"x1/4" and they're not using that material as efficiently as a true space frame. Even more important, the lightest of those cars weigh more than twice what you will be aiming for.
The protective cage needs to react the mass of the car against the crush structure at the acceleration it crushes at in an impact. If the car is half the mass, the cage needs only be half the strength. F=ma in practice.
If you look for it you can find data on survivable rates of deceleration for human bodies. The rates vary with direction (on the body) and duration.
The tricky bit is designing a structure that will crush at the desired rate. Some racecar series have a spec. crush structure, at least for the front of the car. You might like to look for those. (The most accessible is probably FSAE.)