To: Edgar Castro

From: Jon Hagen

Date: 5-11-99

Subject: Monthly report for April '99

The spring problem on the encoder for the carriage house over-speed limiter was solved, only to have the unit fail when its pinion gear worked loose. The pinion was fixed and the encoder was modified to ride closer to the center of the rack. This required a larger protective cover, which is being made in Ithaca. Meanwhile, the over-speed limiter on the Gregorian dome has had no failures.

Computer modeling is underway in the development of a 430 transmitting turnstile for Gregorian dome.

Tests show that the servo motors in the tie-down drive system are unable to overcome the gear box static friction when the tie-down tensions are high, e.g. 80,000 lbs. We can increase the torque by a factor of 2.3 by changing to the same motor used in the Gregorian drive trucks. Mechanical adapters must be made but we have on hand a spare Gregorian motor and servo amplifier which we can borrow for testing at one of the tie-down stations.

Two coop students from Sweden, Benny and Magnus Johansen, have rebuilt the chirp detector in the 430 MHz transmitter. They have also built 430 MHz calibration antenna for use in making a sensitive radiation survey of the controlled and uncontrolled areas on the side.