Jim;
This subject is similar to a previous string about energy absorption of
different roll cage tubing.
Crash energy is dissipated by permanently deforming a material. For this
application, 1020 mild steel is excellent. It is strong, deforms a large %
without fracture, is inexpensive, easily obtained, readily weldable, easily
machined, etc. On the other hand, 4130N is stronger, available to higher
quality MIL-SPECs, and it's available in lighter gauge round tubes, etc.
Actually, for crash absorption, I'd use mild steel for a chassis and save
the 4130N for highly-stressed members such as suspension pieces. The
rulebook limits you on how thin you can go on the tubing so there doesn't
seem to be any weight advantage in going to chrome moly. If you had freedom
to go to something like 1" diameter 0.049" 4130N, that would be a different
story.
Homebuilt aircraft (experimental a/c) have used very thinwall 4130N for
years and their light weight structures are amazing. They aren't designed to
survive crashes, though-- big difference.
Regards, Neil Tucson, AZ
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/land-speed
/// what is needed. It isn't that difficult, folks.
|