STRENGTHENING THE MORGAN CHASSIS (December 2023)

Recently, the same discussion began in the two remaining anglo forums. I joined in on one forum but not the other. Some erroneous information and misunderstanding became public and searchable. Here is the story along with some engineering advice from friends.

Over time, the Works realized that they had innocently created unfortunate stress points on the famous Morgan flexing chassis and a chassis replacement runs into 10s of 10000s these days. 

CHASSIS GUSSETS AT THE FRONT

1. Gussets are great, but one must understand them and their effect before designing, making and using one.

Some preliminary background. A few decades ago, the MMC discovered to their dismay that the combination of the strength at the bulkhead cross member combined with a flexing chassis, cracked the frame at the bulkhead, a place that cannot even be patched. And patching a Morgan chassis anywhere is anything but a forever job on what should otherwise be a forever car. Gussets are a MUST. (However, many homemade chassis (chassis are wear parts on a used Morgan) and even one prominent chassis supplier in the US, omit them, making the resultant vehicles using them far more vulnerable for the want of a costless addition requiring an extra 15 minutes of labor. The lack of the gussets in pre-gusset cars are often the reason a new chassis was required in the first place! GoMoG Law of Human Habit: Habit is a stronger determinant of action than common sense.

Gussets move destructive forces where the gusset directs. The MMC gussets at the bulkhead crossmember moved the crack point away from the bulkhead. A very good thing. However, in the immediate post-gusset era, the MMC soon discovered they had merely created a new plague of cracked chassis at a different place. I think of such things the Deadly Domino Effect. Read on.

 2. Additionally, for some bizarre reason (cost?), Morgan went through model eras where they passed exhaust pipes through the CHASSIS, a huge no-no. Not only does that create bad weak points, but the remaining frame metal around the large hole is constantly being hyper heated and then cooled, expanding and contracting the metal around these holes, which bodes badly for longevity. Yet the MMC gussets ended exactly at these holes!!!! That made chassis cracking even more likely. AND in many cases, owners (like me) received chassis with such frame holes when their exhausts went through the valances! I can think of no perfect remedy for these Morgan frames.

3. Next they tried an imperfectly thought-out knew-jerk fix. But instead of merely extending the gusset past the exhaust holes, they added a metal strapping along the frame under the hole. So now we have a flexing chassis that cannot flex equally in that area, and accordingly, develops frame cracks at either end. :)  These have the same effect as a patch..so the later cars are "pre-patched".

However, at least the old crack point was moved away from the bulkhead. That was a good thing I guess. It allows for cracked chassis be emergency patched. We don't hear about these cracks as much as the earlier ones, (though from this perch they are more frequent). IMHO, a patch on a Morgan chassis is like a unpleasant brother-in-law that has come to live with you forever or until you or he move to that great garage in the sky. (wryly)

This is all to point out the obvious. The Morgan aftermarket and engineering types have confirmed that the gussets should theoretically extend to the front end of the frame, removing the destructive focusing of the stresses right off the chassis! The one displayed above is too short, exhaust hole or not. However, Morgan trad frames are open ended in front.

I think we are fine if they extend 24+ inches with a trad that has not been "exhaust holed" or 8-10 inches past the hole if they are.

WATCHPOINT 1 Contrary to the erroneous information recently given out an American Morgan forum, no Morgan dealer nor the Factory sell these or any other frame strengthening measures saving the very effective underscuttle roll bar, an idea of the legendary Bill Fink. This welcome addition became a feature of Morgans sold overseas early on, (post 1978ish) They are used to anchor the reinforced front doors front hinges. They also stiffer and steady Morgan steering ans save lives.

WATCHPOINT 2  The thin horizontal flange found on all Morgan trad chassis is VITAL. Its strength should be calculated horizontally rather than vertically. making it very important. If it is split or holed too widely the adjacent thick vertical section of the chassis will split as well!

FRAME STIFFENING AT THE REAR (now being written)

In 2002, the MMC and I added rear frame gussets when we recreated my original (1984) car. Also important are gussets at the rear but for suspension and safety reasons rather than structure. Another day..