Tag Archives: Servo

Building 4 Star 60 Day 46: Throttle control adjustments

Tuesday was a productive session though it appears not much was done as it was about getting the throttle working properly (with the transmitter) through a lot of adjusting and installing the extension for adjusting one of the speed settings, see below:

Speed Adjustment Extension Installed
Speed Adjustment Extension Installed

In order to accomplish these two tasks a bigger hole had to be drilled for the speed adjustment extension as things didn’t quite line up properly (that is in order to give room for vibrations).  Some other touch ups will now be required of the covering.

For getting the throttle set properly, which means that at the one end of the throw you are wide open and at the other end you are at idle so that if you hit the kill switch it closes off the throttle shutting off the engine.  This involved a lot of tweaking on both the mechanical and end point adjustments (on the transmitter) sides of things.

We had to remove the engine to adjust the throttle “lever” by taking it off and putting it back on in a new position as it is geared.

Peter also had the tail wheel installed for me already, see below, and on Thursday him and John did the balancing of the aircraft outside since it was a nice day and due to circumstances we couldn’t connect up so I could be there too.  My task next time will be to install the weights they determined are required.

Tail wheel installed
Tail wheel installed

Building 4 Star 60 Day 38: Rudder & Elevator Push Rods

Rudder & Elevator Push Rods Installed at Servos

Tuesday was another 2hr building session, which is about my typical.  When you look at what I got done to the uninitiated you may think to yourself “It took you that long to do what?”.  In order to install the rudder and elevator push rods correctly it takes time.

The first step is to figure out where the control horns need to be attached to the control surface (rudder & elevator).  This is done by using a combination of the plans, to get a general idea where the horn needs to go as it’ll show where the support for it resides, and attaching the push rod to the servo to see where it lines up.   The second allows you to determine the angle at which the control horn needs to be fastened to line up with the end of the push rod.  As seen in the picture at the top I already have a hook in the push rod, which is attached to the servo arm.

Ensure that when you are installing the control horn and push rod the servo and control surface is in the neutral position.

Once this is determined you drill two holes through the control surface to act as the guides for the screws using a hand push drill, not electric, with a tiny bit.  In my case it is two holes kitty corner to each other on the base of the control horn for fastening.  When drilling you need to ensure you are going perpendicular to the surface and straight through, not at an angle, so take your time as it will pay off!  I made this mistake and didn’t get it right so when placing the screws the opening on the back wasn’t lining up with the holes in the back plate causing issues.  Thank-you John for the help correcting this and getting me on the straight and narrow for the elevator!

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Building 4 Star 60 Day 20: Servos, Push Rods and Wing Cleanup

Joined wing clean up Angle view

Had a productive 2hr building session at Peters today.  Started with a trial fit of the push rods for controlling the elevator and rudder of the plane.  Needed to sand the one opening (making sure it’s not the side of the plane being sanded) in order to get the rod to fit.

Elevator & Rudder Push Rods
Elevator & Rudder Push Rods

We also continued working on the wing.  Since the glue was dried from the last session and now the left and right wings are joined.  I removed any excess glue that I could including sanding the glue away from along where the main spars from both wings meet to ensure a smoother finish when it comes time to cover.  Since it’s not a perfectly flush match I used scrap wood to fill the gaps, specifically for the little gap between the rear spars and the trailing edge.

The trailing edge took a little more tweaking due to a clump of glue I had to compensate for by cutting out a section in the filling piece of wood.  You can see another angle of the shims in the top, featured, photo.

Joined wing clean up
Joined wing clean up

Below you can see the servos I assembled and screwed into the servo tray.  Afterwords I glued the servo tray into the slot in the doubler of the fuselage.  In order to know where it needed to be for balancing we visited John to see where his was and determined its 2.5 inches from the front.  He uses the same engine.

The fuselage is upside down and front to the right.  Since I’m using a 4 stroke engine (Saito 100) the servo for controlling the throttle is on the left side of the plane, pilots perspective or bottom servo in the picture.  The others are for the rudder and elevator, don’t have the plans on me so not sure which is which at the moment.

Throttle & Tail Servos
Throttle & Tail Servos

That concluded another fun building session and love seeing the progress we’re making!

Building 4 Star 60 Day 18: Aileron Edge Sanding & Servos

Last night started with a bunch more sanding.  I rounded the trailing edge of both ailerons and bevelled the leading edges.  Peter already had a line made as to how far down I could for the bevel.

To bevel it I performed similar steps I did with the rudder.  Started by taking two passes with a tool that shaves off the wood, making sure to hold it at a 45° angle to start getting the bevel look. I then used a piece of sand paper that was wrapped around flat wood to go back and forth, holding at the same angle, until I sanded to the line on both sides of the edge.  Then repeated for the other aileron.

For the trailing edge of the ailerons I had it in the vice and held a loose piece of sand paper against the sides of the aileron with my thumbs rounding the paper and moving in a motion side to side as well as up and down the length.  I started with rougher sand paper and then fine to complete the look with a smoothly rounded finish.

The next thing I did was cut four hatch rails from the special-cut 1/4″x1/2″x16″ basswood stick provided in the kit.  As you can tell in the pic below there is a little ledge and this is where the servo hatch will be recessed and screwed into.  Each rail (except for the one I screwed up) is cut from the same basswood stick to be a bit over 3.5″ and then sanded until it fits snug.  Once I had them fitted we glued and clamped them into place.  For the one I screwed up (cut it too short… even measured twice, just had the wrong length in my head!) we had to cut a little piece of the excess to make up the difference.  We glued the longer piece of the two into place last night and then Peter was going to fit and glue the little piece into place before our next session.

Hatch Rails Glued
Hatch Rails Glued

Lastly for the day I worked on the servos themselves.  Since this is my first build, my LT40 is an ARF, I got to learn the process of assembly a new (unboxed) servo.  The steps involved here were:

  1. Take out the Phillips screw holding the control horn on
    • Came with a rounded one with holes that wouldn’t work well for my scenario
    • Make sure not to loose the screw as they’re specially threaded and hard to find replacements!
  2. Pull off the ’rounded’ control horn that came with
  3. Put on the appropriate control arm
    • The horns are geared on one so make sure they line up when pushing on
    • The other end is flat & recessed a bit for the screw
  4. Secure with the specially threaded screw (removed earlier)
  5. Place the rubber (for shock absorption perhaps?) pieces into the 4 slots (2 on each mounting flange)
    • Make sure rounded end that sticks out is facing out

Once the servo was assembled the next step was to cut four 3/8″x1/2″x7/8″ pieces out of the 3/8″x1/2″x6″ basswood to use as aileron servo mounts.  Using a 1/32″ shim, the size of the aileron servo, I laid the servo down on the shim and stood the basswood mounts on end against the servo.   Using one of Peters tools I marked the location of the servo mounting screws and then drilled four 1/16″ pilot holes for the screws through the pieces.  Next I used screws provided by Peter (as he doesn’t like the ones provided) to attach the servo mounts to the servos.

We mounted the servos to the hatch cover by gluing the servo mounts (on the side that allowed the servo to be raised off the hatch cover a bit to protect against vibrations) to the hatch cover and then clamping.  When doing this need to ensure:

  • Have one for the left and one for the right wing (it’d be an oopsy to have two for the one wing!)
  • That the control arm is in the center of the slot in the hatch cover both length wise and width wise
    • Peter already marked the center length wise

You can see a picture of the servos mounted to the hatch covers below.

Servos assembled and mounted
Servos assembled and mounted

This concluded another night of building as we got as far as we could, so it was time to crack out the tea :).  I’m looking forward to our next building session as we are moving at a comfortable pace and the aircraft is really starting to take shape!