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Problems with the A Pack

buzzbomb

I know nothing!
#1
I was so excited. I built the plane. With help, I got the A Pack to power it. I learned to program a transmitter and again with help (thanks, Hai-Lee) I got all the electronics working. Then it went down hill into a hole at the bottom of a crater where it crashed and died.

Linkage stoppers. They don't work. The diameter of the screw was so much larger than the holes in the servo arm, that I hand drilled the hole with a dremel bit to widen it out. The plastic still split. I thought, OK. The nut will hold it in place. Only the nut can't because the servo stoppers are only threaded to 50%. The nut can't meet the broken plastic.

I've already broken a control horn trying to do a Z-Bend. I am essentially grounded. My plane that has never flown, cannot fly. I've got an email into the FT Customer Service department. We'll see what they come up with.
 

Hai-Lee

Old and Bold RC PILOT
#2
Just a heads up. When I fit my linkage stoppers I do not drill the servo holes or the control horns using a twist drill, instead I use the point of my No 11 knife blade to grind out the plastic one little crumb of plastic at a time. Whilst this might seem a little tedious it does allow me to get the control horn or servo to fit the linkage stoppers or pushrods exactly!

Most servos come with an array of output arms or disks and if yours did couldn't you use one of the alternates? The distance between the servo axis and the hole in the output arm is not important as long as the ratio between the servo output arm distance from centre axis and the control horn to hinge distance can be maintained.

As for the linkage stoppers they are not supposed to be able to be tightened but rather rely on their ability to spin in the hole to couple the forces to the control horn without adding significant extra load on the servo output.

On the linkage stoppers that use a nut to secure I fit a washer both sides of the control horn/or servo and then fit the nut to finger tight only. Then I secure the nut with a drop of CA. This gives me a good solid installation that I can strip and reuse elsewhere if I wish to!

You can make your own temp control horn from just about any flat scrap plastic or similar material.

have fun!
 

FDS

Well-known member
#4
The above is a reaming bit, they are very useful. Get yourself a small hand reamer example here, may be available from a US tool store etc, they are quite cheap.
If you have no other servo horns they are easy to get at hobby stores or online, I had a similar problem but used the reamer instead.
You could also use a spacer to cover up the un threaded end of the linkage stopper, a small zip tie wrapped around the base would work for now, then swap the arm out later.
 

buzzbomb

I know nothing!
#5
I use this bit on my Dremel to gently widen up holes for linkage stoppers and the like, lightly from either side.
View attachment 119334
Caroline, if it hasn't been said before, you rock it like Elvis. That is nearly the exact tool I used, to hand drill the holes in the servo arms and finally made the stoppers fit.

I retracted my email to FT concerning the issue. The tops of the stoppers still will strip instantly. I've learned that they will still work. It just takes a little creativity and a dremel tool.

It bothers me when stuff doesn't work perfectly. You'd think that would make me an unhappy person, but it doesn't. I've matured enough that I'm used to it.

When you've the inclination, stop by the bar somewhere in the middle of nowhere. (It exists. I made it. It's here on the FT forum.) I'll buy the round.
 

CarolineTyler

Well-known member
#6
Caroline, if it hasn't been said before, you rock it like Elvis. That is nearly the exact tool I used, to hand drill the holes in the servo arms and finally made the stoppers fit.

I retracted my email to FT concerning the issue. The tops of the stoppers still will strip instantly. I've learned that they will still work. It just takes a little creativity and a dremel tool.

It bothers me when stuff doesn't work perfectly. You'd think that would make me an unhappy person, but it doesn't. I've matured enough that I'm used to it.

When you've the inclination, stop by the bar somewhere in the middle of nowhere. (It exists. I made it. It's here on the FT forum.) I'll buy the round.
Thank you :)
I'll have a pornstar martini ta!
 

d8veh

Well-known member
#7
I must admit that, having watched a lot of FT build videos, I don’t remember seeing any detail on how to fit those push-rod terminals. The problem is that they're a standard part, so they won't fit every different type of servo arm. The holes always need to be drilled to 2mm on mini and micro servos, and the thickness of the arms varies too. You need washers on some, which are not provided. A loose fit will cause poor control. Other arms are too thick, which means the rotation will jam if you tighten the nut, so you either need to thin down the arm or glue the nut in the right position. Finally, it's dead easy to strip the thread if you over-tighten the nut.

You don't have to follow exactly the method FT uses to install servos. Often, you can glue the servo in to match the length of a push-rod with a z-bend in both ends. If you have a fixed servo position, you can bend the push-rod to the exact length if you're careful using the method JB demonstrates with normal pliers.

Finally, if the control horn is already glued in, you put the z-bend in it first, then the loose servo arm, then fix the servo arm to the servo.