Nylon vs Metal Gears
 

Morning Guys
I am interested to know what is the general opinion on the best gear train in a servo when used in a high vibration environment (such as a single cylinder 55cc).
Which one? Nylon or Metal.

Metal is definitely better. Nylon gears are less susceptible to wear but more prone to break under loads and vibration.

KBob is correct.
Nylon gears are great for small planes that don't have a lot of stress but on larger AC they will let you down.

The nylon gears main claim to fame is low Weight & Price - once you hit the 30cc Class of models (and above) neither item should be an issue, go with the metal gears!

Hi Guys

Thank you for your reponses - Metal geared servos it will be.

I would advise caution if one of the options is Karbonite gears. I have had a high rate of failure in gas engine equipped planes when I used Karbonite gears. They seem to be okay for glow and electric. When they were first introduced, there was no warning about using them on gassers. It appears we were the beta testers.

Some application of nylon gears is appropriate when using gas, but on the bigger engines, metal is preferred.

Hitec sais 12lbs is the limit for Karbonite gears for non-gas applications. I have a 30cc plane that will be electric powered and should weigh just under 12lbs. My plan is to use Karbonite as that's what I have laying around, but I guess I'm nervous about it.

You fall within their specs. I wouldn't worry.

Electric motors don't put out the vibrations of a 30cc gasser.

Something to consider when considering gear composition, is the size of the control surfaces they'll be attached to? Especially on light weight later model scale/sport planes, and no doubt on anything that might be considered 3D capable! Even without considering the extra beating the gas engine is going to hand them, flutter can often rear it's ugly head, even just momentarily, like when you inadvertently forget to pull the power on a down line? I would ask you to consider flutter resistance when selecting your servos? Obviously not a factor on a moderately powered Cub, but surely a factor on an Extra - even a 15-20cc sized Extra? Flutter, even for just a second, can wipe out gear sets in a heartbeat. With nothing available to hold the flying surface steady any longer, the flutter can continue (possibly worsening) as the plane slows, and you could easily loose that control surface, or worse, the entire plane. IMHO, metal gears are your friend here. They're MUCH more resistant to this kind of thing? Extra cost easy to justify. That's me though, FWIW. -Al

Use good aluminum arms on those metal gear servo's too, not nylon.. otherwise you defeat the purpose of the metal gear servo's.

Exsactly, thats how I decied weather to use metal or not, if I need to use a good aluminum arm then I need metal gears.

I have a top flite gaint p51 when I first built it, I used plastic gear 100oz futaba servos, but after a little while I became uncomfortable as realized I was bumping the control serfaces a lot while putting them in and out of my exsplore, so I figured it was not worth the risk,

As you can bump a plastic gear servo and mess it up and it may not center once in the air.

PS I can not stand the Dubro hevy duty plastic arms, I have serveral that have striped very easly on me couseing me greef.

Thanks Tom, that is pretty much what I was thinking. Hopefully they have a little margin added in their limits - I will be under 12lbs but I don't know by how much.

I fly sailplanes , winch launched. I fly only metal gears . One less thing to be concerned about . It's that simple .

Good nylon beats the metal they use in servo gears. Problem is nobody seems to use good quality nylon anymore. Also if you live in arizona or someplace else with low low humidity, nylon will tend to dry out and fracture much easier.