I thought I would post this here as well, my post from a topic about saw's roughness.
We had a bit of an engineering lecture in the SB the other day, run by yours truly
I was basically explaining what is wrong with saw, and it comes down to a very basic design flaw.
The front row overhangs the front wheel bogies by quite some distance, which over the years has placed undue stress on the pilot pivot/coupler between the two rows (see diagram below).
The "roughness" is actually mostly on the front row, with the back row not affected as much, as it's supported by wheel bogies both in front, and behind the row.
Because of the extra "play" in the pilot car joint, the front row actually bounces in front of the front wheel bogies, when under high G-forces. Next time you are on it you will notice it now I've said it.
Here's a basic diagram explaining what is causing the problem, followed by the best side-on view of one of the cars I could find:
(from Google image search)
As you can see by the diagram, there will be excessive "leverage" force being applied to the pivot point due to the sheer amount of force applied to the right of the fulcrum. This force is further multiplied by the massive difference in length between the pilot to the fulcrum, and fulcrum to the front of the car, and futher multiplied under the force of gravity.
This force will be further enhanced from the back rows weight, also pushing down on this joint, but not as severe due to the support from the rear wheel bogies.
To any mechanical engineer, this is a fundamental design flaw, that is obvious to anyone with even a basic engineering education, so how/why Gerst seemed to miss it, I will never know.
I can only hope the positioning of the wheels on The Smiler is further forward, or has been addressed in some other way, other wise it will fall prey to the same degradation of smoothness that Saw has experienced. It's difficult to tell from the current images, but it does look like the bogies DO attach further forward on Smiler's chassis, so all hope is not yet lost
Hope this has been enlightening for you all
I know this thread is pretty much dead now, but I thought I would mention a point that Boz seemed to overlook, yes the wheels are so close together to aid manoeuvrability, but why then did gerst not place the wheel assemblies in the middle of each car? Exactly the same distance apart, which would eliminate the problem defined by Boz. Would this have any performance problems? No. Would it restrict manoeuvrability? No. The train would be as capable, however why then did they chose not to do this?
The simple reason being that gerst cars aren't capable of universal movement, that is the car can only rotate arounds it's own Z axis, any movement on X and Y will be handled by the wheels, this, whilst providing a huge range of movement, also gives a fundamental flaw, what happens when you place too much load in the middle of the cars?
Well what will happen is the train will simply snap in half, it is a physical certainty. Which leads me to the point that placing the wheels where they are on the cars ensures that any load at the point where the cars are connected to one another is sent straight through the wheels, to the track.
In not saying that Boz is wrong, even if my post does seem a little disparaging, I'm just trying to add an extra level of depth to the reasons why gerst chose to design their euro fighter cars like this.
The engineers didn't chose the location due to manoeuvrability, nor because they are stupid, more because they realised the physical limitations of the joints and materials.
A university lecturer once told me: "you'll know that you're a physicist when you approximate a horse for a sphere to make the math easier, you'll know you're an engineer when you tell physicist that he's wrong."