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Cox Engine of The Month
Cox servos, any users?
Page 1 of 1
Cox servos, any users?
I bought a few of the Cox servos, mostly out of curiosity but also because they are have the nice feature of rubber grommets even though they are very small and light-weight. Usually one will only find grommets on much larger servos. 
Does anyone here have any experiences with them? Any verdicts?
In theory these could be great as a throttle servos, as they have (or should have) vibrational isolation, but there are a few errors with the grommet attachment. It doesn't fit in the plastic and the brass tube is too short. The supplied mounting screws seem a bit too short too.
The rubber can be cut on one side to fit. The plastic holes can easily be enlarged from 3mm to about 3.8-4mm, but the metal part will not reach the screw head as it should. Not sure what to do about that...


Does anyone here have any experiences with them? Any verdicts?
In theory these could be great as a throttle servos, as they have (or should have) vibrational isolation, but there are a few errors with the grommet attachment. It doesn't fit in the plastic and the brass tube is too short. The supplied mounting screws seem a bit too short too.
The rubber can be cut on one side to fit. The plastic holes can easily be enlarged from 3mm to about 3.8-4mm, but the metal part will not reach the screw head as it should. Not sure what to do about that...


Surfer_kris- Diamond Member
- Posts : 1877
Join date : 2010-11-20
Location : Sweden
Re: Cox servos, any users?
I bought some when Bernie had them on sale a while back. I have not yet installed one, but the light bulb in my head indicated I would mount them with some double sided tape or zip ties to a foamie or coroplast profile application. If I were to use it for a throttle servo in a balsa airframe and the screws were to short I would 1- scrounge thru my old servo screw bin and find some longer ones, failing that , 2 - I 'd contact Bernie , 3- I want to go to the basement and get mine out and look at them before further comments about loose or short screws!!

Marleysky- Top Poster
Posts : 3617
Join date : 2014-09-28
Age : 70
Location : Grand Rapids, MI
Re: Cox servos, any users?
Yes, I have enough screws laying around already, so that's quickly solved, it is just strange that the supplied ones are not long enough.
It is the brass tubes that are the real issue, they are simply too short and the vibrational damping will not work as intended. I guess I can make new ones in lathe but that I can do for any other servo too...
It is the brass tubes that are the real issue, they are simply too short and the vibrational damping will not work as intended. I guess I can make new ones in lathe but that I can do for any other servo too...
Surfer_kris- Diamond Member
- Posts : 1877
Join date : 2010-11-20
Location : Sweden
Re: Cox servos, any users?
I bought several from Bernie a while back. Only one was put to work, on the throttle of my .049 Cub. The servo does its job well but it doesn't take much to strain it.
I agree the supplied screws are too short. I picked up some 3/8" mounting screws from the LHS.
I agree the supplied screws are too short. I picked up some 3/8" mounting screws from the LHS.
Re: Cox servos, any users?
Well, I dug out my Cox servos and a DragonFly Servo...looks like twins, cox is red with yellow arms, dragonfly is yellow with red arms. I can color coordinate! Both have the Brass eyelets with rubber bushings and same size screws. I mounted both to a Popsicle stick and the screws just penetrated thru and stuck out 16th of inch before bottoming out on the brass eyelet. I also pushed a standard servo screw theu the rubber bushing and it almost penetrated the wiring harness, so becarefull if you substitute the Standard servo screw for the shorty's shipped with the micro servo.


IIRC the only function of the brass eyelet is to keep the screw from crushing the rubber bushing and elimination of the vibration cushion it provides.
If you can fabricate those on a lathe...wow, my hats off to you.


IIRC the only function of the brass eyelet is to keep the screw from crushing the rubber bushing and elimination of the vibration cushion it provides.
If you can fabricate those on a lathe...wow, my hats off to you.
Marleysky- Top Poster
Posts : 3617
Join date : 2014-09-28
Age : 70
Location : Grand Rapids, MI
Re: Cox servos, any users?
Marleysky wrote:
IIRC the only function of the brass eyelet is to keep the screw from crushing the rubber bushing and elimination of the vibration cushion it provides.
Yes, the brass eyelet is what the screw should tighten down on, without crushing the rubber.
I've found a pair of eyelets on another old servo, these are about twice as long and will do just fine.

Here is what it looks like, proper length on the left hand side;

Surfer_kris- Diamond Member
- Posts : 1877
Join date : 2010-11-20
Location : Sweden
Re: Cox servos, any users?
These COX servos were one of my early buys from Bernie a couple years ago and they did not last for too long. They cannot be steained as much as other similar servos because they simply fail.
I just bought 6 from Bernie at discounted price.
I just bought 6 from Bernie at discounted price.
balogh- Top Poster
Posts : 4434
Join date : 2011-11-06
Age : 64
Location : Budapest Hungary
Surfer_kris- Diamond Member
- Posts : 1877
Join date : 2010-11-20
Location : Sweden
Re: Cox servos, any users?
Thanks for all the inputs. I bought about 6 of these from the Estes surplus store until they closed over 10 years ago. They are limited in power, were used on small electric RTF planes, which tells me that their power is very limited. I've got two on my Minnie Mambo, for throttle and rudder. Thought I'd use the same on my 46" Berkeley Impulse build on the same channels, but may boost the rudder to an 8 or 9 gram servo, leaving only the Icon servo for throttle. I can live with a throttle servo failure, but not on a flight surface.
I'd think them best for 1/4-A stuff. When I get a chance to fly the Minnie Mambo, will know more if they are appropriate or not. Rudder is small enough on it that I think it should hold up without an air balance on it.
I'd think them best for 1/4-A stuff. When I get a chance to fly the Minnie Mambo, will know more if they are appropriate or not. Rudder is small enough on it that I think it should hold up without an air balance on it.
GallopingGhostler- Top Poster
Posts : 4453
Join date : 2013-07-13
Age : 69
Location : Clovis, NM, USA

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