Saturday, April 18, 2009
In the post dated 3/22, I posed the question about what to do with an unbalanced load. I got the answer that I didn’t want, that the cabin couldn’t hang freely, but rather needed an active mechanical positioning system to correct the problem. Unfortunately, the beauty of the gondola design is that it minimizes errant G forces within the cabin by free hanging, so having an active system to correct for “level” would seem to be counter-productive. I think I have solved the problem. First let’s look at a little picture (above) I did to explain how to stop a passenger compartment from swinging too freely. If a vehicle swings too freely a turn or a gust of wind could get it swinging back and forth like a swing set. Pictured are two hydraulic/pneumatic cylinders tapped to work in both directions. (Sorry they look like car shocks, personal clip-art)
The cylinders are connected by hydraulic fluid lines with valves. When the valves are fully open, the “gondola” swings freely. When fully closed it doesn’t swing at all. The valves can then be adjusted for best performance. My guess is that a small bubble of air in the system will enhance performance. Note that two pair of such cylinders are needed, one for front to back swing control and one for side-to-side control. These would be integrated with any other suspension system.
Here is the “Ah-Hah!” part. The unbalanced load creates a difference between the (loaded) cabin position and the position that the cabin should take from (unoccupied) gravity. But this gravity is not necessarily down. It is whatever the forces of momentum make it. Therefore a simple “out of level” detector will work continuously during a journey, because it won’t just detect down, it will detect gravitational force and an active system meant to detect a severely unbalanced load can be added to a free-swinging system. It can straighten out a weight-tipped cabin while still allowing the cabin to swing.
Here’s how it works. A simple tilt detector like this
mercury switch (similar to those found in a pinball machine) determines that the cabin is tilted and the motor (pictured in blue) activates a screw jack to adjust the level. This process is purposely a bit slow, say 3 seconds. During a trip, the cabin will swing somewhat freely. (dampened by the hydraulic system) Any variation from the cabin floor being perpendicular to gravity or G forces will activate the motor, which will contribute to G force mitigation in a minor way during velocity changes and banking, but will principally keep the “gondola” level during constant velocity straight-aways and during “docking.” I have to say that this is a very immature, out of proportion design, posted as a conceptual drawing only.