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How to fix too stiff hinges

#1
Hello all,

I am trying to enter this hobby and I just started building my first plane. I bought the Scout Mini and everything was going very well until installing the servos. I still didn't get my receiver but I connected the servo to an arduino and was able to center and move it.

I found out that my elevator is too stiff (the servo can't move it even to "low rate" position). I am using 4,4g servos (which is the closest to the recommended 5g I could quickly use) and the rudder seems to move OK although you can hear it struggle ("vibrating") in the extreme positions. Is this normal?.

I suppose I might have left too much hot glue in the hinge area when scarpping it. The only thing I remember to solve this is to pass the hot tip of the glue gun through the hinge and "melt my way" to the paper along all the hinge line.

Have any of you had similar issues? How did you solve it? I have no idea of a simple and durable solution.

Thank you!
 

Ketchup

4s mini mustang
#2
I have had this problem many times and I also tried to fix it by dragging my hot glue gun tip through the hinge. It always took a while but it worked to some extent. If it still doesn’t work though, you can always build a new rudder and elevator if nobody else has any ideas. Good luck and welcome to the hobby!
 

Piotrsko

Well-known member
#3
After you run the tip of the glue gun through the hinge glue scrape a bunch away using a piece of scrap then move the surface up & down some until it cools
 

quorneng

Well-known member
#4
FTBRibeiro
"Stiff" hinges are likely to be source of all sorts of control problems.
You are using a small servos so it is important that all or very nearly all the available servo torque is available to move the control surface. That means an efficient linkage and as little 'friction' as possible.
Remember when it is flying the servo has to act against an aerodynamic load particularly at the limits of travel!
If necessary fit new hinges. Better than trying to 'free up' stiff ones.
 

kdobson83

Well-known member
#5
I literally just had this problem with my FT se5 when adding ailerons as an experiment. I mounted one servo under the plane to control both Ailerons. Guessing they were too stiff as it was too much for one servo. I ended up cutting the control surfaces off at the hinge and re-attached it with packing tape. Super strong and moves very free. If you don't mind having tape visible it is a cheap/quick option.
 

Keno

Active member
#6
I quite using hot glue and now use FiX-N- Flex. That is my choice but If you do use hot glue you do have to scape it out cleanly. You can also flex the joint while it cools. Happy flying
 
#7
Hi,

Thank you all for your replies!

I will start by using the hot gun tip and, if not enough, cut the hinge and use tape (is gaffer tape a better option? Heavier but probably sticks better).
I would prefer to build a new one but actually I have never seen foamboard for sale in my country.

Again, thank you for your support. I will let you know how it goes.
 

kdobson83

Well-known member
#8
Hi,

Thank you all for your replies!

I will start by using the hot gun tip and, if not enough, cut the hinge and use tape (is gaffer tape a better option? Heavier but probably sticks better).
I would prefer to build a new one but actually I have never seen foamboard for sale in my country.

Again, thank you for your support. I will let you know how it goes.
Gaffers tape would probably work but it'll add a lot of weight on the tale of your plane making balancing harder. I would use regular packing tape, should be plenty strong enough and super light.
Try taking off the glue first tho for sure! Good luck!!
 

daxian

Well-known member
#9
glue gun nozzle ,is the way to go ! i use my covering iron to even out the glue surface when i get to much in the wrong places ...which is great ,if you have one !!
 

quorneng

Well-known member
#10
Just to add I am a strong advocate for using top 'tape' hinges.
The tape on this Super Cub aileron is virtually invisible. Matt finish sellotape can be painted.
A further advantage is it gives a smooth top wing surface. AilTop.JPG
AilUnder.JPG
Super free moving it 'drops' under it own weight with the servo link rod disconnected.
The tape has been in place untouched for 4 years!
 
#11
Just to add I am a strong advocate for using top 'tape' hinges.
The tape on this Super Cub aileron is virtually invisible. Matt finish sellotape can be painted.
A further advantage is it gives a smooth top wing surface. View attachment 137571
View attachment 137572
Super free moving it 'drops' under it own weight with the servo link rod disconnected.
The tape has been in place untouched for 4 years!
Wow, 4 years for packaging tape is impressive. Definitely my choice if the glue gun doesn't do it.

I am eager to arrive home and test it.

Again, thank you all for the support.
 
#12
I managed to use the tip of the glue gun and the results seem quite good: The elevator can move with ease by hand and the servo can turn it symmetrically to both directions. I actually did the same with the rudder although it was quite good before.

Question: Is it normal or acceptable that the servo "vibrates" when holding the extreme positions or does this mean that I need to free the hinge a bit more? I think there is still some minor room for improvement using this process but I don't know if it is necessary.

Thank you all for your great tips.
 

cdfigueredo

Well-known member
#13
I managed to use the tip of the glue gun and the results seem quite good: The elevator can move with ease by hand and the servo can turn it symmetrically to both directions. I actually did the same with the rudder although it was quite good before.

Question: Is it normal or acceptable that the servo "vibrates" when holding the extreme positions or does this mean that I need to free the hinge a bit more? I think there is still some minor room for improvement using this process but I don't know if it is necessary.

Thank you all for your great tips.
The servo should not vibrate, it is evident that it cannot complete the movement of the arm. That could be because of the hinge, but If you are within the ranges of motion for the control surface, try placing the control rod in a hole closer to the center of the servo and/or further away from the horn base on the control surface. That will decrease the control of the surface allowing the servo to complete the arm movement.

123.png
The image shows trhee settings from less to more control.
 

Brett_N

Well-known member
#15
And now you know reason #472 of why to NOT use hot glue.

Get some Titebond II Quick & Thick (or any other good carpenters glue) and some rubber bands. Hot glue only for very minor stuff. Carpenters glue is stronger, lighter, cheaper, and doesn't burn your fingers
 

Merv

Well-known member
#16
Question: Is it normal or acceptable that the servo "vibrates" when holding the extreme positions or does this mean that I need to free the hinge a bit more?
Sounds like the servo wants to go further but can not because something is stopping it. It other words the servo is stalled out.

If you can, remove the obstacle. The other alturntive, set you end point in the Tx to limit the servo travel.

Regarding hot glue hinges, I have used an old covering (or clothing) iron to smooth out the hot glue. An old soldering iron is also useful, just don't use a good soldering tip, that you indent to solder with.

I make all of my hinges with tape & hot glue. Put the hot glue on a hinge, smooth it out with an iron, put the tape on, use the iron to reactivate the glue. Now the tape is glued to the foam. Quick, easy, super flexible & it has never failed me.
 
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#17
So, it seems that what I did was not enough. I will try some more and then switch to packaging tape.

I already had the control rod set up to maximum mechanical advantage. Either I can "unblock" it or I need stronger servos.

The question with using different glues is that I don't know what would be an equivalent to the ones you suggested here in Portugal.

I will work on it a bit more tomorrow and let you know.

Thank you!
 
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