jimboflying
MEMBER
Seatbelts are important. A friend of mine survived a crash but the seatbelts broke and he sustained serious facial injuries.
Jim,
The seat belt tabs are .090 4130. I bought them from Javron to save some time fabricating them. I have decided to wrap them around the cross tube, the surface of the tab will be parallel with the floor and angled up about 45 degrees. I think this will work easily. Pictures of the tabs are on another post, http://www.supercub.org/forum/showthread.php?49410-How-do-I-weld-in-my-seat-belt-tabs
Marty
These two comments are leading me to question how much thought is going into the seat belt installations. Not just Marty and Jim, but everyone. This might be a good exercise for a retired engineer's evening project. He could calculate the crash loads of a heavy human body against the seat belt. The angle these loads apply to the seat belt anchors. The size of the bolt which holds the belt to the anchor. Is this bolt in shear or bending? Is the bolt in a single (bending) or double shear installation? The tear out loads of the bolt in the hole of the anchor strap. What is the direction of the load on the welding of the anchor strap? Are there enough inches of weld for the applied load? Will the .090" by x" wide strap handle these loads? How far around the fuselage tube should the anchor strap be wrapped? Will the anchor strap tear off in a crash? What alloy should the strap be? Will the fuselage tube support all of the above loads? All of these questions, and perhaps others, need to be answered with certainty. Whichever of those questions produces the least strength is the location that will fail first.Seatbelts are important. A friend of mine survived a crash but the seatbelts broke and he sustained serious facial injuries.
Cub Junkie,
What does the term "double shear" mean?
Marty, in light of this discussion I'm a little embarrassed to admit that mine are the factory arrangement. However - the factory arrangement did serve me well when I wrecked my plane 25 years ago. I hit a large upturned spruce stump with enough speed to tear the engine mostly off of the fuselage, knock the radio out of the panel and destroy one wing. But the seat belt (and shoulder harness) held and I was unhurt except for a dislocated toe where the firewall folded over my foot. But despite that success, I wish I had routed the front seatbelt to the floor.Gordon, how are the seat belt's attached in your '12?
Marty, Is this your fuselage or just an example of the use of the steel nut? The reason that I ask is because I am questioning the weld joints of the two flat tabs, with the large burned out notch to the vertical tab and wondering what is the purpose of that cross tube. What is the load path through both? If that upper tube is part of the primary structure the tube should have it's load path centered in the cluster not in a bending location.