Tuesday, March 4, 2014
Vehicle Ramp Specifications
Ramps are inclined planes---one of the six simple machines, and probably the oldest of them. While modern materials, configurations and purposes have changed the ramps appearance and construction methodology, the basics of its design pre-date humanity and still apply today. Ramps come in all sizes and can assume a variety of forms to suit any vehicle application.
Construction
Ramps come in two basic types---hollow or solid. A solid ramp has no empty space in the middle to collapse under the load, making them far stronger and more stable than a hollow ramp. The obvious downside is that solid ramps are very heavy, which makes them difficult or near impossible to transport and place.
Plane or Self-Supporting
Look at any ramp from the side and youll see that it basically forms a right triangle. Self-supporting ramps use a vertical support to suspend the high end of the ramp plane; a simple plane ramp spans the distance from a higher point to a lower point. In addition to being fully portable, self-supporting ramps can be stronger and less prone to bending since the support effectively shortens the ramps inclined plane. However, the ramps vertical legs require some sort of reinforcement or triangulated tie to keep them from kicking out under load.
Approach Angle
The ramps plane angle determines its approach angle, which is an important consideration when it comes to vehicle loading and ramp versatility. Imagine wedging one end of a yardstick under your front tire, then pulling the other end up until it hits the bottom of your front bumper. The angle that the yardstick forms relative to the ground is its approach angle, or the steepest ramp that it can traverse. Departure angle works the same way, but extends from the back of the rear tire to the bottom of the rear bumper. A low car with a long front overhang (like a Saleen S7) will have a lower approach angle than a jacked-up truck with a short front overhang (like a Hummer H1). Lower approach angles necessitate a longer ramp with a shallower angle.
Break-Over Angle
Break-over angle is the inverse of approach angle, and is equal to 180 minus ramp angle. Break-over angle is an important consideration since the top of the ramp effectively forms a peak that the bottom of the vehicle must be able to clear. Very low and long-wheelbase cars like the 1958 Cadillac Eldorado will have a lower break-over angle than taller, shorter-wheelbase vehicles like the Jeep CJ.
Load Rating
A number of factors go into determining a ramps load rating, including ramp size, material used and construction methodology. Self-supporting ramps are generally limited by their vertical supports, since the vehicle load is almost always trying to push them out from under the ramp or bend them in half.
No comments:
Post a Comment