Saturday, April 30, 2011

Ginpole anyone?

Two of these little gems will be employed to raise the Lattice truss walls once they are assembled at their final location in South Wayne. Installing the lifting yokes to the top chord and rigging the pulleys on the ginpole was a good practice run that will be repeated and studied before the real thing latter this summer. The 3/8" to 1" scale model is just the right size for this.

A good critical analysis of the steps in the process will insure that the maximum safety practices are used and followed by all those involved with the raising.  Safety. Think, what is the worst that could happen?

 (Above) With a rope tied and "wrapped" around the bottom chord and secured at the bottom of the ginpole. This rope keeps the bottom of the truss from slipping outward during raising. The bottom of the ginpole will be placed in a hole to prevent sliding of it also.

 (Above) Two lifting yokes will be attached to the outside of the top chord of the truss. The yokes keep the ginpoles aligned and prevents it from sliding sideways along the top chord during lifting.

 (Above) The gilpoles must be long enough to leave room for the pulleys at the top of the ginpole when they have done their work bringing the truss to vertical. Finding out the ginpole is to short with a 2,500 pound truss 3/4 of the way up would not be appreciated.

(Above) Here is a close-up of how the pulleys are rigged. The pulley at the top of the ginpole, reverses the force on the rope. The "moving" pulley,  attached to the lifting yoke,  acts as a second class lever providing a 2:1 lifting force mechanical advantage. The pulling end of the rope is attached to the hand winch at the bottom of each jinpole. The winch provides more mechanical advantage and braking control as the truss is raised.

Puzzler - How many things could go wrong during the truss raising process using ginpoles? Will winches having a 2000 pound capacity each do the job?

Tech Vocab - 1st class lever - 2nd class lever - 3rd class lever - 6 Simple Machines - Fulcrum - Lever Arm - Mechanical Advantage (MA) - Ratio - Winch - Ginpole - Moving Pulley

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