Third Major Blue Ox Casualty
Yesterday on our first trip of 2014, our Blue Ox Aventa LX Towbar separated in heavy traffic on I-85 near Charlotte, NC. One leg of the towbar came completely loose with the stub end dragging on the...
Forum Discussion
My 34 year career in fastener sales & fastener safety training seminars won't let me not put in my 2 cents.....so many areas to comment on:
1) Whiz Lock nuts are Grade #2, dead soft, low carbon steel, not designed to accept the loads of a Grade #5 bolt.....what happens is, under load, the threads in the nut "give" allowing the connection to lose clamping force (the tension holding the parts together). This can result in the bolt fatigue failing from the continual stretching & relaxing from the changing load conditions. Picture bending a coat hanger back and forth to failure...
2) Tack welding the nuts, either to the frame or the bolt, could apply enough heat to totally anneal the steel, causing it to lose strength.... or even alter its chemistry enough to cause a brittle condition.
3) Loctite, when applied, is a lubricant until it sets up... Most Torque Charts DO NOT account for this fact. An approximate 26% reduction in applied torque from a clean & dry torque value is required, otherwise, an overloaded condition can result, damaging the bolt on installation. An overloaded bolt can stretch and "neck out" ( reduction in diameter), causing a decrease in strength.
4) If the holes in the frame became elongated, I suspect the fastener had stretched, allowing the base plate to move.... Again, this could easily have been caused by the Whiz Lock, low grade nuts, or by over-torqueing because of the Loc-Tite
5) A Shear type failure is very, vey rare, actually occurring at a rate of about 2% of the fastener failures that happen. If the broken end of the bolt appears relatively smooth, except for a small "torn" area, and has "beach marks" ( like waves make on the beach), it is actually a fatigue failure.
6) My issue with ALL of the hitch & tow bar companies, is the providing of inadequate fasteners... perhaps grade 5 bolts, but grade 2 nuts... or wrought (dead soft) flat washers instead of alloy steel, thru hardened washers.....
7) Nuts & bolts should always be used with an alloy steel, thru hardened flat washer. A flat washers purpose in life is to provide a smooth, even bearing surface to enable the proper installation of the fasteners.
8) Many users of Torque Wrenches practice improper technique..... only hold the handle at the grip. If steadiness is a concern, hold your other hand only directly over the socket, without touching the bar of the wrench. Pull slowly and smoothly until the wrench clicks..... then STOP....It is possible to override the internal clutch in a torque wrench........
9) I usually cover this and much more in my 1 3/4 hour fastener safety training classes...........
1) Whiz Lock nuts are Grade #2, dead soft, low carbon steel, not designed to accept the loads of a Grade #5 bolt.....what happens is, under load, the threads in the nut "give" allowing the connection to lose clamping force (the tension holding the parts together). This can result in the bolt fatigue failing from the continual stretching & relaxing from the changing load conditions. Picture bending a coat hanger back and forth to failure...
2) Tack welding the nuts, either to the frame or the bolt, could apply enough heat to totally anneal the steel, causing it to lose strength.... or even alter its chemistry enough to cause a brittle condition.
3) Loctite, when applied, is a lubricant until it sets up... Most Torque Charts DO NOT account for this fact. An approximate 26% reduction in applied torque from a clean & dry torque value is required, otherwise, an overloaded condition can result, damaging the bolt on installation. An overloaded bolt can stretch and "neck out" ( reduction in diameter), causing a decrease in strength.
4) If the holes in the frame became elongated, I suspect the fastener had stretched, allowing the base plate to move.... Again, this could easily have been caused by the Whiz Lock, low grade nuts, or by over-torqueing because of the Loc-Tite
5) A Shear type failure is very, vey rare, actually occurring at a rate of about 2% of the fastener failures that happen. If the broken end of the bolt appears relatively smooth, except for a small "torn" area, and has "beach marks" ( like waves make on the beach), it is actually a fatigue failure.
6) My issue with ALL of the hitch & tow bar companies, is the providing of inadequate fasteners... perhaps grade 5 bolts, but grade 2 nuts... or wrought (dead soft) flat washers instead of alloy steel, thru hardened washers.....
7) Nuts & bolts should always be used with an alloy steel, thru hardened flat washer. A flat washers purpose in life is to provide a smooth, even bearing surface to enable the proper installation of the fasteners.
8) Many users of Torque Wrenches practice improper technique..... only hold the handle at the grip. If steadiness is a concern, hold your other hand only directly over the socket, without touching the bar of the wrench. Pull slowly and smoothly until the wrench clicks..... then STOP....It is possible to override the internal clutch in a torque wrench........
9) I usually cover this and much more in my 1 3/4 hour fastener safety training classes...........
