|
Servo Growling & GlitchingFrom information printed in the CR-914 NEWS
Any servo may "growl" or "buzz" when it is at stall load or close to it. A servo is stalled when it has a load that is so large that it can't move the servo arm to the position being commanded. In strong winds the sheet loads can pull the sheet out, actually moving the servo arm in the opposite direction. It certainly growls when this happens but you will never hear it. Experiment by using your radio to set the arm in a mid-point position with no load. Grab the common sheet and pull until you back-up the servo arm. It should growl or buzz. Growling is not of concern in most cases. However, the battery drain is high when a servo is stalled. For instance, the stalled sail servo draws more than one amp (1000 mA). Drum servos used by other classes of model boats have overheated and failed when operated at stall for too long. I have never heard of an arm type servo failing from stalling, however. Occasionally an owner will set up the sail servo arm so it contacts the brass keel pipe when sheeted in. This stalls the servo and, if continued for a long time, might do damage to the servo. Servos will sometimes "buzz" briefly when not highly loaded. No one really understands why. SERVO GLITCHING Glitching is best described as growling and jumping, or fluttering. This frequently happens when you have your boat on shore with your transmitter turned off, but the boat left on. It is generally attributed to the proximity of other transmitters on different frequencies. The solution, turn off your boat. Glitching can happen when sailing and you will notice the sails jerk in and out, or the boat steering becomes erratic. This is usually caused but a frequency bounce from something around you or interference from someone transmitting near you. The best solution is to move the transmitter to a new location, just a few steps usually does the trick. Sometimes with older servos, glitching is caused by dirt in the potentiometer (pot). Solution is to replace the servo or disassemble the servo and clean the pot. What you do is a trade-off between the cost of a servo and the time it takes to attempt to clean the pot. Remove the four screws holding the three sections of the case together. By removing only the bottom case, the gears in the top don't have to be disturbed. If you do remove the top case, remember how the gears are to be reinstalled. The pot is at the bottom end of the output shaft for the servo arm. Carefully remove the cover over the pot by bending back the metal "ears." Look for dirt in the track of the wiper arm on the pot. (Manually move the arm to see how the pot works.) A jewelers loupe, or magnification of some kind, may be useful. Carefully remove the dirt and test to see if the problem is fixed. Then reassemble. Edited 12/99 from the NEWS
Questions or comments - contact Steve Lang, ModelSailingCenter.com 303-670-4670 or Steve@ModelSailingCenter.com |