Ladder bars..??..
The problem I have with the ladders in the video is the way they attach to the axle bracket...
Large dia ARB's place a lot of stress on the bar's attachment points, the catch-22 in this design is in the area of the attachment bolts. That center bolt adds very little strength to the connection, and the other two middle bolts don't add much more. The front and rear bolts take the lions share of the stress, and i'm guessing they are only about 5" apart.
Quick calculations here that are likely flawed, but let's say a car weighs 3300lbs with 825lbs on each tire. If the car articulates or gets out of shape enough to cause the ARB effect to transfer all the rear weight to one side, that places a incredible amount of stress on those rear attachment bolts. If the effective length of those ladders is say 42" and the rear attachment bolts are only 5" apart, stress at the front of the bar is amplified by about 8.4x thru those rear bolts. Then consider that the track width is wider than the width between the two ladders, that amplifies stress due to weight transfer even more. Transferring 825lbs thru 42" long ladders 30" apart on a car with around 60" of track width, to bolts about 5" apart on the axle brackets equals around 14000lbs. Tensile strength of a 1/2" gr8 bolt is around 21000, but that flat area of the axle bracket where the bolt goes thru is going to bend/fatigue first. Add to that the forward hole thru the ladder itself is a stress riser, may be reducing the bar's section in that area by about 50%. The bar material looks to be hot rolled, nowhere near gr8 tensile strength.
That front axle bracket bolt area just looks like trouble to me.
Grant
The problem I have with the ladders in the video is the way they attach to the axle bracket...
Large dia ARB's place a lot of stress on the bar's attachment points, the catch-22 in this design is in the area of the attachment bolts. That center bolt adds very little strength to the connection, and the other two middle bolts don't add much more. The front and rear bolts take the lions share of the stress, and i'm guessing they are only about 5" apart.
Quick calculations here that are likely flawed, but let's say a car weighs 3300lbs with 825lbs on each tire. If the car articulates or gets out of shape enough to cause the ARB effect to transfer all the rear weight to one side, that places a incredible amount of stress on those rear attachment bolts. If the effective length of those ladders is say 42" and the rear attachment bolts are only 5" apart, stress at the front of the bar is amplified by about 8.4x thru those rear bolts. Then consider that the track width is wider than the width between the two ladders, that amplifies stress due to weight transfer even more. Transferring 825lbs thru 42" long ladders 30" apart on a car with around 60" of track width, to bolts about 5" apart on the axle brackets equals around 14000lbs. Tensile strength of a 1/2" gr8 bolt is around 21000, but that flat area of the axle bracket where the bolt goes thru is going to bend/fatigue first. Add to that the forward hole thru the ladder itself is a stress riser, may be reducing the bar's section in that area by about 50%. The bar material looks to be hot rolled, nowhere near gr8 tensile strength.
That front axle bracket bolt area just looks like trouble to me.
Grant
