Kenneth Walker Observatory

 

Background

The original shutter system was over 40 years old. Weather and use had deteriorated the wooden structure to the point where it was difficult to open easily. The shutter used two separate ropes and pulleys that made the door a challenge to control with one person. The goal of this phase was to alter the original system into a safe controlled configuration.

Research

Concept One This design concept changes the movement of the shutter from sliding up and down the dome to a left to right movement. Straight iron track will extend tangentially off the dome structure approximately five feet in two locations. The iron track locations will support the bottom and top ends of the shutter via steel trolleys. Although this design concept would have prevented free fall and constant monitoring of the shutter door, the disadvantages proved this design impractical. Modifications to the existing structure would have been extensive and costly. There was a very high risk of damaging the structural integrity of the dome by extending angle iron off of its supports. This door motion would also cause an uneven distribution of weight, making dome rotation more difficult.
Concept Two This concept changes the movement of the shutter from sliding up and down the dome to opening outward like a draw bridge. The bottom end of the shutter would be attached to the dome by means of high strength door hinges. The shutter and cabling would be controlled by a hand winch secured to the inside bottom frame of the wooden structure. Like concept one, the shutter door completely open would cause an offset of weight on the dome structure. Due to its age and deterioration, it was determined that there was a high possibility that the shutter door opening in this position could cause critical damage to the wooden structure. There was also a large risk of kids jumping on the door and star party participants being hit while the dome was rotating. Overall, the risks of this design were far greater than its advantages.

Final Solution

The cable continues up and over three pulley blocks then loops around a 12” pulley anchored near the top opening of the door. The cable rides back down the pulley blocks and attaches to the inner spool of the worm gear winch. This system was proven advantageous for this project because not only were there limited modifications to the dome structure but the loadings remain the same as the existing system. The worm gear winch acts as a clutch controlling the lifting and dropping of the shutter. This gives the user the capability of stopping the shutter at any location. Parts are easy to replace and easy on the budget.

Shutter Replacement

The original shutter’s wooden frame was replaced with a new aluminum frame, making the door weather resistant, lightweight, and easier to operate.