9 replies to this topic

[wera44]

Im getting ready to start my cage build in the next few days and had a question. I went to the last nasa race and took a bunch of pictures of built cages and noticed one major difference. On some cages the rear most attachment points landed right next to the suspension mount and some were run well past that. I like the idea of it being welded past the suspension to give the rear more protection in event of a crash and maybe even saving the suspension components but will I lose some the advantage of a stiffer suspension by moving that point further back? Sorry if this has been covered, I did a search and didn't come up with much. Thanks in advance for any input.

[38bfast]

Mazda has enginnered in crumple zones in the back of the car to absorb energy. Adding bars way rearward would defeat Mazdas engineering. I prefer to mount the rear bars just over the rear subframe attachment. 

[Jim Drago]

Mazda has enginnered in crumple zones in the back of the car to absorb energy. Adding bars way rearward would defeat Mazdas engineering. I prefer to mount the rear bars just over the rear subframe attachment. 

I agree and do the same

[wera44]

Thanks guys. I was kinda leaning that way now I'll build it that way.

[davew]

I completely dis agree.

 

I have seen many cars back into walls that have utilized the "crumple zones'. The damage is extensive and expensive. Sometimes totalling the car. By having the bars extend back, the damage is minimalized. With the short design it is impossible to put a trunk crossbar into the cage. And very difficult to add a rear diagonal bar.

 

Everybody has an opinion

Dave

[Jim Drago]

I completely dis agree.

 

I have seen many cars back into walls that have utilized the "crumple zones'. The damage is extensive and expensive. Sometimes totalling the car. By having the bars extend back, the damage is minimalized. With the short design it is impossible to put a trunk crossbar into the cage. And very difficult to add a rear diagonal bar.

 

Everybody has an opinion

Dave

 

 

Cars and crash damage in Sm are relatively cheap all things considered.. Backs, spines and neck injuries can be expensive an painful for years.   I agree both methods have benefits, but I'm only worried about myself in the car, not the possible cost of damage.  I agree every one is entitled to their opinion and no idea if mine is "right" just an opinion  

[38bfast]

I worked a lot in the OE industry working in design to meet impact requirements. The OEs spend millions and millions in development to meet the standards. I for one and not going to second guess all their development work. Guess it come down to what do you value more, your body or your car. JMHO. 

[wera44]

I wouldn't take anything to the track that I wasn't willing to leave there in pile of parts.

[Bench Racer]

Guess it come down to what do you value more, your body or your car. JMHO. 

Maybe both if one has the long rear support tubes. Could cause damage to main hoop/entire cage and the drivers body. First time out back with new build, the car took a harsh a$$ packing from another car. Crunched the living crap out of everything behind the rear tubes mounted near the shock mount. Shall we say the OEM crumple zone did it's job. The four tire alignment was not knocked out one bit. On a frame stretcher the unibody pulled back to normal and new rear body parts fit perfect.

 

Different strokes for different folks : )

[DavidNJ]

Maybe both if one has the long rear support tubes. Could cause damage to main hoop/entire cage and the drivers body. First time out back with new build, the car took a harsh a$$ packing from another car. Crunched the living crap out of everything behind the rear tubes mounted near the shock mount. Shall we say the OEM crumple zone did it's job. The four tire alignment was not knocked out one bit. On a frame stretcher the unibody pulled back to normal and new rear body parts fit perfect.

 

Different strokes for different folks : )

 

What was the speed differential between the cars? How much movement was there after the crash?

Wouldn't spinning at the end of a long straight and backing into a guardrail or tire wall at have been a lot more serious?

To the best of my knowledge the only rear impact tests in the US or EU are low speed to test the seat and head restraint (e.g. http://www.euroncap....ion/whiplash/).

How much do the rear cage braces do in a longitudinal crash? Does anyone triangulate the rear braces longitudinally? Lacking that, wouldn't the longitudinal contribution from the braces just be for relatively small impacts? TransAm cars use an end to end cage (pictured below).