Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing FLEXIBLE CHASSIS

So what exactly happens here?- is it just made of metal so thin that it gives, or is the 'flexibility' built in in a controlled way?If so,how is it done?
Why dont the floorboards crack and loosen?
what is the advantage?

It's not designed in, rather that it can't be designed out.
Prewar cars had ladder chassis - so called because they look similar to a ladder. A two dimensional chassis can't be braced three dimensionally, so it will twist laterally. If it's any consolation, this also happens with 60's monocoques such as MGB and Midget, where the door fit deteriorates if jacked up on one corner. Try jacking one wheel of your Mog, and you'll find that the doors won't close quite as well. The twist is only slight, so the floorboards are Ok - but they do have a flexible sealant applied.

The chassis of the Morgan is basically a ladder chassis, but instead of I beam, Box section or tube it's made of Z section steel. I assume it's done like this to make it easy to manufacture. Especially as this technique has been used from the initial designs.

It has little triagulation amongst it's key components, basic ladder, bulkhead and cross head.

The Ash reinforcement which is bolted down each side of the chassis under the main tub is put in to strengthen the chassis but allow flex.

Think of the chassis as 1/3's

Rear third, mounts and supports the rear axle
Centre third main tub and passenger compartment
Front third engine compartment and mount for the front suspension via the cross frame

To a certain extent the flex is esentially "built in"

Advantage:
Gives a slighly more supple ride, making up for drawbacks of rudimentary suspension.

There was a space frame supplimentary chassis used in one one racer I recall. ie. original chassis, with a second bolted to it to instill regidity.

I think the Big Blue +8 racer had a space frame chassis with honeycombe structural pannels.

Moving to a more modern and rigid chassis type would basically superceed the suspension both front and rear and introduce weight.

So wilst not perfect it gets the job done, all be it, in a traditional type way... which after all is what Morgan is all about.

For a comparison to effectiveness, just think about a similar output Lotus Elise. Similar weight, power output (ok slightly better aerodynamics). The lap-times and driving comfort are significantly better..... look at the differences in design as to why.

Here can you see the chassis:

http://www.mig-welding.co.uk/forum/attac...mp;d=1205325588

The Z-section has a good "weight-to-stiffness ratio" and allows to put the seats deeper down. About 20 years ago a German owner had his +8 chassis stiffened over the whole lenght. The roadholding of the car changed to the worse.

Frank

lookin at that pic,I'll lok out for potholes even more carefully!

Morgans are basically pre-war cars when flexible chassis and stiff suspension was the norm, modern cars of course being the opposite, one of the first mass-produced cars with a torsionally stiff monocoque was the Austin/Morris 1800/2200 [or if you were posh like my parents a Wolseley Six ]