ORIGINAL: G-Pete
ORIGINAL: ram3500-RCU
Nylon is superior to metal when strictly looking at vibration resistance ignoring the torque strength issue, as is the case with the throttle, choke, air valve, etc.
Sorry man but that statement is wrong.
Nylon gets soft under stress - that means when you have a high vibration under high stress they tend to brake off easy. Nylon is not in the family of high resistant plastics. Nylon is easy form able, cheap and has a good ''all around'' capabilities. Again, Nylon is soft and is a good media for small gears - with a
medium load.
One word to the vibrations - servos are protected against vibration (rubber mounts with bushings) because of the solder joints on the leads and circurit boards.
If you like to protect the bearings and gears - use heavy duty servo arms. They are nylon and work a shock absorber.
Barry, a dual elevator with this size of bird is a must. Even you have a strong enough servo which can pull both of them. If you lose one of them - no big deal the bird is may sluggish but still under control. The same with the ailerons - you lose one, sluggish but flyable.
The digital servos have a higher resolution and they are more precise
Give me your control surface measurements and I can calculate the minimum servo for each. And I need the movement in degree or inch, plus the estimated top speed.
Example:
Speed 75mph
aileron
12 long 2inch wide 1/2 inch max defection - and so forth.
Takes you 3 minutes to measure and another 2 to post.....
Not an engineer. But I did stay at a Holiday Inn
Seriously, my statement is based on over 40 years of experimenting and history. My nylon servos last indefinitely and indeed out live the airframes in most cases. Yes, that is why I say for the the throttle etc. And yes, rubber mounted servos are somewhat insulated from vibration. The throttle is not even medium load, it is no load in most cases. Nylon is used as a bearing material in industry and even furniture building, as I have done. Metal wear under the vibration of a gasser is accepted to be as fast if not faster. Miles Reed used nothing but JR servos, even the 8411s, with nylon gears instead of metal, for their tightness, all the way up to and including his famous 40% Weeks. Not to mention that metal on engine servos is a waste of weight. I prefer metal in torque situations on the giant stuff. But for low or no loads, nylon is my choice with 5 poles for durability and tightness.
A good, 5 pole, nylon servo will serve you well on your engines, and at a modest cost.
G-Pete is all over the math though, and will help you not waste money by grossly over engineering things.