Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Chassis rust on 2012 M3W

Good synopsis. One must consider China's steel making facilities are state of the art, being relatively new. But how they manage their quality control is, as mentioned above, unknown. Sulfur and phosphorous content tend to make steel brittle at temperature extremes,ie below zero F, can't quite remember which is which, I think the sulfur makes if cold short. I also think a huge factor here is joint design, the metallurgical changes in the heat affected zone from welding ie grain growth which makes the fracture look like cast iron, and fatigue stresses, which can be hard to estimate. Using a chrome-moly alloy usually requires post weld heat treatment, difficult and expensive for a small manufacturer. Plain old mild steel is pretty ductile and can take a lot, IF the joint is properly designed to keep the stresses well under the fatigue limits. I still think a broke frame can be welded IF properly reinforced to lower the stresses, including minimizing residual stresses from the welding.

I was going to suggest Reynolds 531, it would probably be lighter as well.

True, but Reynolds 531 is not intrinsically that much lighter than other grades of steel - its superiority comes from the fact that it is ductile and suitable for double-butted and triple-butted designs. Car tubular chassis' typically use straight-gauge tubing - but no reason why a butted design couldn't be used. Caterham built a proof of concept - at not inconsiderable cost!

http://www.pistonheads.com/gassing/topic.asp?t=1550657

With over 1000 M3Ws out there

How many other car companies would allow any form of corrective or warranty work to be done outside of the dealer network?

I was just going to add that I have total confidence in RD Racing. I have looked at some of their work. They had re-bodied an alloy long tail lightweight E-Type with all its double curves, beautifully. If they can do things like, the rather crude Three Wheeler should be child's play.

BTW I was looking at a Polaris Slingshot three wheeler today on a rally I was on. The chassis which has doubled longitudinal tubes, so that there are a total of eight fore-aft tubes. They are all frequently cross braced and apparently made from chrome moly steel. It all makes the M3W chassis rather under-designed.

Wilson

I have been following the evolution of the Slingshot for some time and it certainly is interesting to note the differences in approach to the engineering and development program and with a base price under US$29,000 also looks good value.