HS 7954sh problems (stripped) - RC Groups
Shop our Airplanes Products Drone Products Sales
Thread Tools
Jul 11, 2016, 12:30 PM
I kill throttle servos
3d-Chris's Avatar

HS 7954sh problems (stripped)

Yesterday I was flying my Extreme Flight 50cc Yak. The minimum torque rating for the plane is 250oz on a 1.5 inch arm. I run on 7.2 lipo 403oz on a 1.5 inch arm.

I did a crankshaft and noticed my left aileron was fully deflected and not moving. It stripped. I landed the plane. I took the servo apart and there was a kabonite gear! No wonder it broke, funny how Hitec recommends this as a giant scale gasser servo, but on their karbonite gear servos it says "DO NOT USE WITH A GAS ENGINE." Today I was making sure all the other servos are fine as well, and I noticed the left elevator is notchy. Stripped as well.

I set all of my throws with a hangar 9 amp meter and a pitch gauge with no binds.

The 7955 servo is a waste, it has the karbonite gear too! Your servo is only as strong as its weakest link....

I called Hitec and they told me you have to buy the gear. HUH? The servo is 2 months old! This isn't the service I have heard of.

I am a very disappointed Hitec user. My Savox 2270SG dosent do this. I didn't pay $500 for them all to go bad in 2 months.
Sign up now
to remove ads between posts
Jul 11, 2016, 01:07 PM
Xpress..'s Avatar
Sorry for the frustrations, unfortunately we cannot warranty stripped gears because of the nearly limitless number of ways they can strip out. Our manufacturers warranty cover defects in the servos electronic components. If you want to return the servos to us then we will take care of the issue for you.

Stripping the MK gear is something that very rarely happens and requires a huge amount of force on the servo geartrain in order to strip it so something I might suggest is taking a second look at how your airplane is setup with regards to control throws, linkages, ensuring that the servos aren't being driven to the point where your control surfaces can't travel any further, and ensuring that the servos aren't binding up at any point if you have ones that are mounted inside of the stabs (like what is common for most giant scales).

The MK gear was specifically designed for this application so it is very much capable of handling what the servo can push out. We advise not using the full Karbonite geartrain servos in gas models because they were not designed for it.
Jul 11, 2016, 01:23 PM
I kill throttle servos
3d-Chris's Avatar
Ill include a link of others having the same problem. Is there a reason other than they break easily that Tower sells just the MK gear?
Jul 11, 2016, 01:25 PM
I kill throttle servos
3d-Chris's Avatar
Jul 11, 2016, 01:26 PM
I kill throttle servos
3d-Chris's Avatar
Like I said I used a Hangar 9 current meter, .1 amp or less through the whole range of motion. No binds.
Jul 11, 2016, 01:37 PM
Xpress..'s Avatar
The comparison between airplanes and surface vehicles is very minimal, you're talking about another application entirely. The MK gear very rarely strips in giant scale applications, we make it available separately for those that do and generally it's only the rock crawler guys seeing this issue, but that's a totally different application that in no way relates to airplanes. You can send it into us and we'll fix the servos for you if you would like, otherwise you're more than welcome to replace the gears yourself and save some shipping cost.

I use these servos in my 30% and 35% airplanes and they are more than sufficient, even for my 35% Yak that has enlarged ailerons and they are thrashed every weekend. Why you stripped 2 servos out I don't know because that so rarely happens in these airplanes that it's very difficult for us to pinpoint the exact cause. We wouldn't recommend these servos for GS airplanes if they didn't work extremely well.

One other question I have is what type of flying do you do? Are you 3DXA or old school 3D?
Last edited by Xpress..; Jul 11, 2016 at 01:44 PM.
Nov 14, 2016, 07:22 AM
I kill throttle servos
3d-Chris's Avatar
By the way I stripped 5 now. Tower doesn't have the gears, do you?

Is there anyway you can make me a metal version?
Nov 14, 2016, 12:48 PM
Xpress..'s Avatar
We are out of stock of the replacement MK gears, there is no all metal version available.

Quick Reply

Thread Tools