Phil Lammatina Incident, chassis experts thoughts?
Discussion
http://www.youtube.com/watch?v=tiF2KHDXXZ8
First of all, yet another testament to the fantastic safety standards that we all know and love. Scary looking incident for sure.
Comparing the footage with other similar incidents of chassis failure (ie Barry Sheavills), it is interesting to note that in the Australian incident, the chassis broke ahead of the drivers feet, rather than behind the driver as happenned with Barry's incident. I am no chassis expert, so I am asking those on here who know; is this a consequence of more modern chassis design, or simply the case that the car happened to break at this point in this instance?
First of all, yet another testament to the fantastic safety standards that we all know and love. Scary looking incident for sure.
Comparing the footage with other similar incidents of chassis failure (ie Barry Sheavills), it is interesting to note that in the Australian incident, the chassis broke ahead of the drivers feet, rather than behind the driver as happenned with Barry's incident. I am no chassis expert, so I am asking those on here who know; is this a consequence of more modern chassis design, or simply the case that the car happened to break at this point in this instance?
Very scary.
I remember Larry Dixon having similar incidents.
The Lammatina Family's (who own Australias biggest carrot farm - yes really) car was a 2000 Gary Scelzi car.
A chassis fault of the time as Dixons car did the same in 2000? Is it a case of to much bowing of the chassis? Front and rear downforce to great?
Here is Dixons incident:
http://www.nhra.com/movies00/race21/TFFinal_00race...
I remember Larry Dixon having similar incidents.
The Lammatina Family's (who own Australias biggest carrot farm - yes really) car was a 2000 Gary Scelzi car.
A chassis fault of the time as Dixons car did the same in 2000? Is it a case of to much bowing of the chassis? Front and rear downforce to great?
Here is Dixons incident:
http://www.nhra.com/movies00/race21/TFFinal_00race...
The reason many pro class chassis are left unpainted is so cracks can be more easily seen. Paint is just a filler, especially epoxy powder.
But you have to remember to look for cracks to get any benefit !
Even a thorough visual inspection won't save you; that's why some people use dye penetrant sprays to show up cracks while they're still tiny.
Ultrasound can help but its awkward to use on welded areas where you can't get a good probe contact, and the welded joints are where the frame normally breaks, or at least the edge of the heat affected zone of a weld.
4130 chrome moly chassis are stronger than seamless drawn over mandrel steel chassis, but less ductile so they're more prone to stress cracking. This tendancy to stress cracking can be minimised by correct welding procedure and technique, but conversely also made far worse as well.
4130 tubing was originally designed for aerospace use and welding with gas which also stress relieves the weld; but the only guy who knows if the weld is good is the welder who laid the bead.
TIG process is (on the face of it) a little more forgiving and panders to the lowest common denominator in welder ability and thats why its in the NHRA rule book as the mandated welding process. However it doesn't build in post weld heat treatment and control of the welding heat has more than a little to do with overall quality of the finished piece.
Finally don't forget that a hard run TF chassis is effectively trashed at about 100 passes and after that you're just waiting for it to break up.
[Stands back and waits to be slaughtered by any coded welders on the forum]
But you have to remember to look for cracks to get any benefit !
Even a thorough visual inspection won't save you; that's why some people use dye penetrant sprays to show up cracks while they're still tiny.
Ultrasound can help but its awkward to use on welded areas where you can't get a good probe contact, and the welded joints are where the frame normally breaks, or at least the edge of the heat affected zone of a weld.
4130 chrome moly chassis are stronger than seamless drawn over mandrel steel chassis, but less ductile so they're more prone to stress cracking. This tendancy to stress cracking can be minimised by correct welding procedure and technique, but conversely also made far worse as well.
4130 tubing was originally designed for aerospace use and welding with gas which also stress relieves the weld; but the only guy who knows if the weld is good is the welder who laid the bead.
TIG process is (on the face of it) a little more forgiving and panders to the lowest common denominator in welder ability and thats why its in the NHRA rule book as the mandated welding process. However it doesn't build in post weld heat treatment and control of the welding heat has more than a little to do with overall quality of the finished piece.
Finally don't forget that a hard run TF chassis is effectively trashed at about 100 passes and after that you're just waiting for it to break up.
[Stands back and waits to be slaughtered by any coded welders on the forum]
veryoldfart said:
are chassis's ultrasound checked for stress cracks? (like an airframe i believe)
if i raced TF id like the chassis checked (then again id need a JCB or Scania chassis with my 'arris.....)
No, they are not, but I guess there is nothing stopping the owners getting them done if they wantedif i raced TF id like the chassis checked (then again id need a JCB or Scania chassis with my 'arris.....)
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