The complete radio control model airplane FAQ.
Misc. radio and servo questions relating to radio controlled model airplanes.
How do I repair my receiver antenna?
What do all of the servo terms mean?
Metal Gear Servo Control Arm Screw Sizes
What is a Standard servo? What is a ball bearing servo? What do all the servo terms mean?
A "standard" servo often just refers to the size. Some people use it to refer to the cheapest thing they can get their hands on, though.
A cheap standard servo doesn't have ball bearings. That means that the output shaft just rubs on the plastic housing...and as it wears out, you get slop. That translates to more flutter potential and less precision. Then you have to replace the case. I believe Hitec has a version that uses "oilite" bearings, which are basically bronze bushings--much like you have on the connecting rod of your glow engine. This is a compromise between the plastic bushings and ball bearings--you get lower cost than ball bearings, but better durability and life than plastic bushings.
A ball bearing servo has...a ball bearing, instead of rubbing on the plastic. They'll take more side loads without wearing out nearly as fast.
Unless otherwise stated, servos are analog. They update the position of the output shaft once every signal pulse--typically 20ms. A digital servo, on the other hand, can update several times between each pulse, too. That means they can have more torque and higher speed. Of course, if your plane actually demands the torque, then you pay the price with reduced battery life.
Then there's the five-pole servos that Hitec has...which are basically a faster, more accurate standard motor. Better yet is the coreless motors. Because of their design, they can accelerate faster, are more accurate and are less prone to overheating.
What size screw does
my metal gear servo take?
Futaba S9202 M2.6x8
Futaba S9303 M2.6x8
Futaba S9304 M2.6x8
Hitec HS-615MG M2.6x8
Hitec HS-645MG M2.6x8
JR DS8411 M3x6
JR DS9411 M3x6
Multiplex mc/V2 Jumbo M3x6
Multiplex mc/V2 Jumbo Spd M3x6
Multiplex mc/V2 Power M3x8
Multiplex mc/V2 Profi M3x8
Multiplex mc/V2 Profi Spd M3x8
All the above sizes are available from Micro-Fasteners. The M2.6 are expensive. Thanks to Craig on the Scale Aerobatics list.
How do I repair my receiver antenna, and is it worth it?
You can replace it yourself if you are competent to do a proper solder joint. You can use any stranded, insulated wire of about 24 gauge cut to about 39" long. That length will be acceptable for any of the 72 MHz channels. The job should take no more than 5 minutes. Sid Washer
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Revised: December 13, 2001 .