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Old Jan 15, 2006, 11:20 PM
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THUREN's Avatar
United States, OR, Bend
Joined Jun 2005
2,932 Posts
Discussion
Servo gear strength. Micro metal vs. standard nylon

I searched around a bit with no concrete answers... So here's some questions..

Would a sull size NYLON GEAR servo, with similar torque specs to to a micro METAL GEAR servo, have a similar gear strength? It wouldn't seem that the nylon could hold up as well as the metal but I remember reading it somewhere that full size regular servos nylon gear sets are of comparable strength. Here's an example as I have a radio coming with 5 of these JR digitals...

NES537,
Specs
Torque: 40.3 oz/in
Speed: .25 sec/60
Dimensions: 0.73 x 1.52 x 1.32in
Weight: 1.58 oz
Bearing: single
Motor Type: 3-Pole Ferrite

compare that to say........

HS85MG's....
Torque 42oz
Speed .16 second
Size : 1.1"x 0.5"x 1.1"
Weight - 0.77 oz

I have the JR digitals coming for "basically" free with the radio but I don't know if the gears are worth much... I don't want to bury these servo's in a EPP plank if I'm just going to be digging em' out after 2 flights...

THANK YOU!!!

Don
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Old Jan 16, 2006, 11:02 AM
Fly R/C writer
Redlands, Ca
Joined Dec 2004
1,967 Posts
Hi Don,

One of the things you have to consider in this formula is that metal geared servos do not have the same size gears and gear ratios as the same or similar servo with nylon gears. So, the relative "strength" of the material is somewhat lost in this question you have. In general a metal gear servo has superior strength. Most manufacturers will place at least one of the gears in there as a nylon gear to protect the electronics and motor from damage in the event of a severe shock to the servo, (like hitting the ground). They would rather you break the gears than to destroy the rest of the servo and have intact gears.

Normally, the rule of thumb is that for harsh service environments, use a metal gear servo. They are more robust and can handle more abuse. When they do strip a gear, the gears may cost you more. You should also consider that if you do strip the gears, can you buy new ones very easily? If not, not only will you be digging out the striped servos, but you'll be down longer than you might want to be.

Mike Lee
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Old Jan 16, 2006, 11:30 AM
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Joined Feb 2004
337 Posts
I would tend to use the digital servoes because in a plank type plane the servoes need to center very well. I have had trouble with my bluto and my halfpipe with centering issues with Hitec 85 metal gear servos. Planks are very touchy with elevator changes so I think the centering power of digis might be in order. I am waiting for someone to come out with inexpensive digital servoes with metal gears with the size of minis or mids
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Old Jan 16, 2006, 12:18 PM
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Florida
Joined Aug 2004
4,156 Posts
In general, metal gears are stronger but metal gears also develope slop and wear much faster than nylon gears do. Unless you are pushing gear strength, nylon gears will give you longer and more slop free service.
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Old Jan 16, 2006, 09:22 PM
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THUREN's Avatar
United States, OR, Bend
Joined Jun 2005
2,932 Posts
Thanks everyone!!!

I know that micro size nylon gear servos can strip almost by themselves... Are standard size servos as touchy? Some of these servos could be going in a combat-type wing if they could stand a few knocks...

I guess I'd just have to try it...

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