The Femur and Tibia black servo screws keep loosening up. I’m running on short carpet but it’s probably grippy with the rubber leg covers. It happens after only a couple of minutes of operation at medium to high speed. Will probably slow things down and keep doing observations till I can figure it out.
Does anyone else have this problem on a Phoenix?
Hi br549,
I have had the same issue and solved it by adding some “locking ringsâ€
If the screw is threading into a nut on the back side, try running a piece of thread thru the nut before inserting the screw. This could provide a bit of an interferance fit to keep the screw from comming lose.
Thanks for clearing up the eternal tooth star washer! 8)
We’re talking about the screw to mount the servo horn. So placing a nut isn’t a option. I do use some M3 version on my rover though.
Xan
um sorry I didn’t get exactly which screws were being referenced.
I’d go with the star washer probably, however if you have the MG or SG servos, specifically a servo where the splined output shaft is metal and not nylon, but the servo output horn IS nylon then you can try a very very small touch of non-permanent thread lock (like Lock-tite) on the screw thread. You should not need to do that with metal servo horns if you use the star washer though.
How about using METAL servo horns? Love 'em.
Alan KM6VV
I got some small star washers. Still coming loose. I have a metal servo horn. I might try and get some star washers that are a little bigger next. Don’t want to go to lock-tite but I might have to.
I use teflon tape, the kind plumbers use for keeping showerheads from leaking. Just wrap a really thin strip around the screw as it goes in. Works like a charm.
Are you talking about the screw that threads into the servo output shaft that holds the servo horn on the shaft? Do you have a metal servo horn or a metal servo output shaft, or both? If it is the screw that holds the horn on the servo shaft, I’d put the horn on the shaft, put the ends of a thread or two down into the screw hole (don’t pack the thread down in the hole, just have the thread running down the side of the hole with the other end outside), then thread the screw in the hole. Similar to using thin toothpicks for a stripped out wood screw.
Yes
Both
Here is a picture of my setup.
lynxmotion.com/images/jpg/phoen01.jpg
The black middle screw in the center that goes into the servo is the problem.
I’m going to try both the teflon tape and the thread and see what works best. Thanks everyone for the suggestions.
You can also use a little loctite just under the head of the screw just before tightening it down the rest of the way. Then the screw is locked to the horn, but the threads are not effected at all.
The problem exists because the metal horn on the metal output has no give and take as a nylon horn would. So even though there is like a thousandths of a mm of rotational slop, it’s enough to work the screw out. There is nothing wrong with adding a little loctite. It’s what it is designed for. Just don’t go overboard…
Just don’t use the permanent stuff. 
I use threadlocks in RC application due to the high vibration and shock introduced to the entire vehicle…
Loctite “Blue” is what you want to use if you don’t want it to be permanent. It’ll feel tight when you back out the screw, but this is an indication that the loctite is working.
If you are serious about locking it down, use Loctite “Red” compound. But you have been warned, this is near permanent locking of the threads.
Threadlocks are ONLY for metal to metal. DO NOT USE on metal to plastic or plastic to plastic. You shouldn’t need any locking compound for metal to plastic, the plastic should be able to have enough squeeze on the screw to hold it on.
If you do need to do metal to plastic, I recommend a SMALL amount of CA glue. You can find CA glues in all hobbyshops. They can also be found at supermarkets, the brand at the supermarkets are often “Krazy Glue,” “Super Glue,” and sometimes “Bondini.”
