Bob Nogueira wrote:
>
> -- [ From: Bob Nogueira * EMC.Ver #3.1a ] --
>
> Hey Moggers
> Has anyone found or read of a fix for the problem of the Morgan chassis
>bending upward aft of the rear axle?
>
Hi Bob et al,
The dip in the Morgan chassis top flange at the rear wheel axle is
unfortunately (and has to be for clearance to the axle) at the worst
spot structuraly. Just where the bending moment from the bump load is
maximum, the chassis resistance to bending is minimum. In an I beam, or
a Z beam like a Morgan chassis, the resistance to bending is
proportional to the cross sectional area of the flanges and their
distance apart from each other. The distance apart (web depth) is
minimum at the axle. What to do? You can't change the dip shape, so
you have to add to the cross-sectional area of the flanges both upper
and lower. In a +4 and a 4/4 that I rebuilt, I welded in a 1/8" thick
plate with a 90 deg bend to the bottom flange and vertical web. The
plate was cut to match the curve of the top flange and extends beyond
the dip by a few inches. A second strip of 1/8 was added inside the
curved top flange and welded to the bent plate and original chassis
flange. I rebuilt these cars several years ago and so far so good. The
4/4 has been autocrossed many times and so far the chassis is still
straight at the rear axle.
That's my tuppence.
Regards, Tony Souza
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