An overhead door with height h30 and weight W800lb consists

An overhead door with height h=30 and weight W=800lb, consists of two identical sections hinged at C. The roller at A moves along a horizontal guide, whereas the rollers at B and D, which are midpoints of sections AC and CE, move along a vertical guide. The doors\'s operation is assisted by two identical springs attatched to the horizontally moving rollers (Only one of the two springs is shown). The springs are stetched 0.25 ft when the door is fully open. Determine the minimum value of the spring constant k if the roller at A is to strike the left end of the horizontal guide with a maximum speed of 1.5 ft/s after the door is released from the rest in the fully open position.

Horizontal guide Fully open Vertical guide Fully closed Figure P7.79 Assuming that friction between the rollers and the guide can be neglected, determine the equation (s) of motion of the system

Solution

Residential doors can be one piece or sectional. Sectional doors are far more common. They can be referred to as overhead doors sometimes because they roll on track that is over your head. Sectional doors are made of panels. One piece doors used to be referred to as California doors and are made of a single panel that flips up to open.

The materials that the doors are made of vary. They can be fiberglass (very light), aluminum, metal, and wood (very heavy). They can be insulated to keep in heat. Some may have glass in one or more panels. When doors have insulation and/or glass, they tend to be heavier. Wood doors (called carriage house doors) tend to more decorative and very heavy. Wood doors usually need a more robust operator, like a ¾ horsepower (HP) unit.

However, the track and rollers really just guide the door. The door itself is really heavy; they can weigh from a couple hundred pounds to a thousand pounds. Because of this, a door needs a counterbalance. This is done with either a torsion bar with springs or extensions springs. Older doors used a system of pulleys and sandbags. The torsion bar is far more popular than the extension spring.

If you look on each side of the door, there are two cables that attach at the bottom of the door and wind around drums at the top. The drums are attached to a long bar (torsion) that has a spring. As the door moves, this spring winds or unwinds to counter the weight of the door. Chamberlain does not manufacture or provide support for the door components. We do not assist in replacing, repairing or adjusting door springs. These springs are under a high amount of tension and service must be done by a qualified door systems technician.

Sectional door tracks

Sectional doors come in different styles for the tracks. They can be standard, high lift, vertical lift and low head room. This refers to the types of tracks that the door rolls. All residential and commercial door tracks are normally 2\" inches in width. Heavier door and industrial garage doors are supported by 3\" inch tracks.