Re: Bent frame rail

Posted by DJ.Voyce on September 30, 1997 at 12:38:28

In Reply to: Bent frame rail
posted by Glen Weilbaker on September 30, 1997 at 07:49:19

: Why does the frame commonly bend at the rear motor mounts?
: I'm currently doing a frame off that has the passenger rail bent and the driver's straight. At first I thought maybe it was weak to carry weight and the bend occured over time, but why one side? When I replaced the rubber for the mounts, there was rust scaling into the rail behind the rubber but that was on the straight side which makes it even weaker, so I don't think weight could be the cause. Then I noticed the passenger frame horn bent, probably frome a fender bender. Could this be the cause? The reason I ask is I don't want to have a problem after the car is together that can be prevent now. Currently I'm planning to repair the rusted section which is only inbetween the 3 motor mount bolts and straighten the frame. Would this be ok or should I consider another option?
: GW
G'Day Glen,
My theory as to why the frame/chassis tends to bend at the rear motor mounts (& I may stand corrected on this) is that all of the vehicles weight & shock loadings whilst in motion are carried at the furthermost extremities of the chassis, ie. the front & rear cross members where the springs are mounted. Most of the vehicles mass is located just rear of the front axle in the form of the engine & transmission, steering box, cowl & fuel tank, & battery, so the three large holes for the engine mounts drilled so close together in the side rail then tend to become a weak point, hence the tendency to always bend there. What should also be taken into consideration is that the vehicle is at least sixty-some-change years old & didn't have today's kind of surfaces underfoot.
Next problem is how bad is the rusted section & how do you intend to repair it as any welding on any longditudinal chassis member is definately a big "NO-NO" unless you want to end up with more cracks than you can shake a stick at. Not knowing the extent of the corrosion I'd hesitate to advise any type of repair before being aware of all the facts, but if it's only scaling & just leaves a bunch of deep pits after sandblasting or wire brushing, I'd say just prime & paint it. Hope this helps.
Regardz
DJ.
OutOfAfrica A's

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