RunRyder RC
 1 page 853 views POST REPLY
HomeAircraftHelicopterCrashed? Discussion and Photos › stripped out servo
04-02-2005 12:32 AM  13 years agoPost 1



My Posts: All  Forum  Topic

Well I got the chance to fly my Raptor 60 today, I had just got it all trimed out and dialed in. On my first pass i pulled up into a stall turn, and started to pull out. The heli made a twich in the up direction, and the heli started to do back flips. I still had control of everything else but elev. I stayed with it through a couple of flips but it still it the ground hard.

When i got over tho the heli the only thing i could see that would cause such a thing was stripped out elev. Has anyone has had this problem with Fut. 9202. I'm also using a push pull system on the elev.

04-22-2005 05:50 AM  13 years agoPost 2



My Posts: All  Forum  Topic

keep in mind using a Futaba 9202 on the raptor 60 is okay for hovering and slow FF...anything assoicated with 3D....will result a stripped gear just as you stated.

Please use something stronger than 92 oz inch of torque on the collective...something like Futaba 9252 would be a good source collective....but more than 92oz of torque would be better.

If i remember correctly that 9202 has about 63 oz inch of torque...not an ideal stick banging servo.
Here is my thought...

Unless the higher torque servo has a stronger gear material, it will not be less likely to strip under load. Given the same gear material the lower torque servo will actually be LESS likely to strip, unless the torque/load ratio is so bad that the servo arm actually gets pushed back, to its physical extreme.

I'm not denying that he would be better off using higher torque servos, but I don't think having one would have prevented the servo from stripping (again, unless it has stronger gears).
The heli made a twich in the up direction, and the heli started to do back flips.
If the servo gears stripped during flight, how was the servo arm able to apply the pressure required keep the cyclic in the aft position to do continuous flips?

I'm not sure why the heli started to do flips, but it sounds to me like the servo stripped when it crashed.

I'm not trying to piss anyone off, I just thought I'd chime in with my post-crash "forensics"


04-22-2005 06:24 AM  13 years agoPost 3

rrElite Veteran

Huntsville, Al

My Posts: All  Forum  Topic

I agree with your forensic findings and have often been bashed for it as well The gear material is the same in both the 9202 and the 9252. All more torque does is raise load at which the servo motor will stall or fail point on the motor, a 9202 will stall before a 9252.. You can strip a 9202 no easier than a 9252. Where torque is needed on big birds is because of the bigger loads applied a good example would be collective pumping.. If falling fast and full positive collective was added the load may be such that the servo would stall at 76in/oz of torque and not give you full collective, but it would not be likely to cause a stripping. I fly the pants off of a few Raptor 70's and 90's and would not put a 9202 on collective I have either 9451's or 94758's but all of the 70's have 9202's on the cyclics.

Now as for the the stripped gear holding the servo locked and continually applying elevator it could easily happen. Many of inflight servo strips happen for one of two reasons. Binding, or damage from a sudden strike. If a few teeth broke off one gear and got into the mesh during the full back elevator it could effectively jam the servo gears and prevent them from returning "back" to neutral.

The twitch was probably from current draw caused by the bound servo..

Just my .02 worth of forensics and I could be way off base


Proud member of the Quick UK, Duralite Flight Systems, V-Blade, & KBDD team

 1 page 853 views POST REPLY
HomeAircraftHelicopterCrashed? Discussion and Photos › stripped out servo
 Print TOPIC  Make Suggestion 

 1  Topic Subscribe

Wednesday, July 18 - 5:52 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online