Some time ago I listed a posting on fitting cross members with gussets
already fitted, and somebody replied saying that the curvature of the side
frame would pose a problem, I did mean to reply but have been lost with other
activities of late, and I know, its a subject which has been flogged to death
time and time again, so if you are disinterested, just don't bother to read any
further, But, if you fitted a mathematical curve to the longeron so that any
infinite point could be plotted by a set of co ordinates, using a axis system
as a frame of reference, and at the point of intersection of the centre line of
the cross member with the longeron, the curve was differentiated to obtain the
gradient ( ie, the slope of the tangent to the curve at the intersection point,
), and the same exercise was executed for the leading edge of the fwd gusset,
and the trailing edge of the aft gusset, ( to give the maximum deviation in the
gradients ), and compared all three values, then you would more than likely
find the difference in all three gradientsd to be next to zip. What this means
is that over the short distance of the curve involved over the length of the
gussets, the deviation of the curve from that of a straight line approximation
is so small to be meaningless. However, if you were really concerned about the
matter, then you could take to the problem with a sanding block and face a
small taper on the leading and trailing blocks so that, in plan view anyway,
you would have three straight lines approximating the curve, but if you are
really convinced that there is a serious bend in the thing then you may as well
keep right on sanding and sand of the high points and fit some sort of a curve
on the gussets. I would have thought that the error induced by the glue line
would have a greater order of significance than any deviation of the curve from
its straight line approximation but then, what would I know, I only have a
small number ( Two ) of brain cells, and these are fully occupied with walking
and talking, so not much spare capacity at all on these higher order things.
I really think the core of the problem is being missed, being that the
number of variables are being reduced by fixing the gussets to the cross
member, its much easier to fit one cross member and its associated bits, than
to try and fit three pieces which will slip and slop and slide all over the
place, how you want to mate those components together with the side frame is a
minor problem and can be done by whatever method you see fit, you can always
fit the cross member and then the gussets later, ( and this works cause thats
the way I did it ), but then you have to get excess dried glue out of the
joint, which in itself is not impossible to do, we all have different resources
at hand, and different levels of experience, so the best I can say is whatever
method you get to work for you is probably the best way to get the job done!
Chris johnston
North Richmond
Australia.
