JTC
Bronze Member
I like to start by saying, if someone isn't comfortable with modifying a structural component, they should not do it. I've seen this debate a few times on TBN so I've decided to chime in with my $0.02. The following is my opinion only and should not be considered advice.
I on the other hand feel very comfortable with doing these kinds of things. One could calculate the net effect of drilling holes for lights in a ROPS, I think this is overkill. A little common sense (or Engineering insight) will go a long way here. Think of where the stresses and forces are on the ROPS in a roll over accident. The top of the structure will contact the ground acting as a lever as the momentum of the tractor twists the base of the ROPS. The forces are concentrated and increase lower on the structure. Lights are typically mounted higher on a ROPS.
Another way to think of it is to take strip metal , say 2" wide by 1/8" thick and 24" long. Drill a 1/4" Dia. centered on the strip about 6" from one end. Clamp the other end in a vice and push the free end until the strip bends. I would bet that the strip will bend where it is clamped in the vice, not at the hole. Any lever that has a constant cross-section through its entire length is over designed by virtue of the fact that the forces increase at the fixed point of the lever. In the real world, it is more economical in most cases to use a constant cross-section structural member then to taper away from the base, but its easy to find examples where this is done: larger FEL and BH arms, some bridge trusses...
Most people get into trouble with floor joists when they notch them instead of cutting holes in the center. A notch can severely reduce the load bearing capacity where an equivelant sized hole centered in the joist may not significantly reduce its structural integrity.
Of course, any manufacture is going to warn of the dire consequences of modifying their product, I not a lawyer but my understanding is the modification would need to cause the failure for the manufacturer to be relieved of liablity. In other words: You roll your tractor, ROPS bends or breaks where you drilled holes -> your fault. You roll your tractor, ROPS bends or breaks at base -> their fault (not caused by your modification).
Jim
I on the other hand feel very comfortable with doing these kinds of things. One could calculate the net effect of drilling holes for lights in a ROPS, I think this is overkill. A little common sense (or Engineering insight) will go a long way here. Think of where the stresses and forces are on the ROPS in a roll over accident. The top of the structure will contact the ground acting as a lever as the momentum of the tractor twists the base of the ROPS. The forces are concentrated and increase lower on the structure. Lights are typically mounted higher on a ROPS.
Another way to think of it is to take strip metal , say 2" wide by 1/8" thick and 24" long. Drill a 1/4" Dia. centered on the strip about 6" from one end. Clamp the other end in a vice and push the free end until the strip bends. I would bet that the strip will bend where it is clamped in the vice, not at the hole. Any lever that has a constant cross-section through its entire length is over designed by virtue of the fact that the forces increase at the fixed point of the lever. In the real world, it is more economical in most cases to use a constant cross-section structural member then to taper away from the base, but its easy to find examples where this is done: larger FEL and BH arms, some bridge trusses...
Most people get into trouble with floor joists when they notch them instead of cutting holes in the center. A notch can severely reduce the load bearing capacity where an equivelant sized hole centered in the joist may not significantly reduce its structural integrity.
Of course, any manufacture is going to warn of the dire consequences of modifying their product, I not a lawyer but my understanding is the modification would need to cause the failure for the manufacturer to be relieved of liablity. In other words: You roll your tractor, ROPS bends or breaks where you drilled holes -> your fault. You roll your tractor, ROPS bends or breaks at base -> their fault (not caused by your modification).
Jim
