OMPHobby M4 Build Picture Guide

This guide is meant to be used along with the OMPHobby M4 User manual or OMPHobby M4 Max User Manual
Best viewed on a larger screen like a Tablet or Laptop.



1 Cyclic Servo rack assembly

NOTE: Use thread-locker on all screws except servo balls and nyloc nuts.

Tail servo assembly

Tail servo install

Main Frame assembly

Main frame: Tail pulley assembly

Main frame assembly: Right side

Main frame assembly: Left side

Motor assembly

The 8x10x0.2mm shims are supposed to be provided in a spare parts bag containing spare screws and washers. First batch of kits may not contain them.

Motor Install

Motor block install

Servo block install

NOTE: The 3 bolts need to go through the servo block, motor block and the motor. Make sure the holes of all those 3 components are aligned correctly before installing the bolts.

Flight controller mount and Landing Gear

Tail Bell Crank Assembly

Tail Slider assembly

WARNING: Tail slider bolt has reverse thread. Remember to use Loctite-243 on it.

Tail Rotor assembly

Tail rotor is the trickiest part of the build so please pay extra attention. The sequence in this guide will make it a bit easier for you.

Explosion view:Tail housing brace is missing in this picture but will be shown later
Tail pulley assembly

Pay careful attention to the orientation of the Pulley Guidance Flange, Tail pulley and Tail case.

  • Pulley Guidance flange: larger diameter side should face the pulley
  • Tail pulley: pin cavity should face the pin.
  • Tail case: The larger diameter of Tail case Flange bearing should face inwards.
Tail Fin and Bell-crank installation
Tail bell-crank pins assembly
Finished Tail pulley and Tail slider assembly

Tail Rotor Grips assembly

Tail boom installation

  • Install tail control rod guide before inserting tail boom in the frame
  • Push the tail boom all the way in so you can install the tail belt on the motor pulley.
  • Pull the tail boom out to properly tension the belt and then tighten the tail boom clamp bolts.

WARNING: Do not over-tighten the belt, as this can lead to increased wear and reduced tail drive efficiency.

Tail control rod assembly

Finished tail control rod

Apply AB epoxy glue to fix the link to the control rod. Wipe of excess glue. Leave aside for curing time of epoxy glue ~24 hours.

Screw the M2x8 self tapping screw to the tail control rod guide after inserting the control rod into the guide’s slot. Do not over-tighten the screw.

Fix the rod ends to the ball links on the Tail servo and Tail ball crank.

Tail rod binding with boom clamp: needs to be fixed

Ensure that the Tail Control Rod does not bind with the Tail Boom Clamp over the entire range of Tail Control Rod motion. If it binds then it means the ball links are not perfectly in-line with the control rod. A quick fix is to flip the link at the Tail servo ball link.

Swashplate install

  • Make three linkages of the same length (~31mm hole-hole), note that turnbuckles feature one right hand and one left hand thread each. The tapered side of the turnbuckle faces down.
  • The ball joint’s flat spot with OMP logo faces outward when connecting the linkages with the ball screws.
  • The turnbuckles can be adjusted in length without removing them from the helicopter.
  • Tapering portion of main shaft collar should point downwards.
  • Pull the shaft upwards and press the collar downwards while tightening the collar set screw. Use Loctite-243.
  • To make it easier to install the swash plate you can loosen the anti-rotation guide screws and bend it outwards a bit. Remember to tighten the anti-rotation guide screws with Loctite-243.

Motor roll bar

Main rotor head

  • Make three linkages of the same length (~38mm hole-hole). Note that turnbuckles feature one right hand and one left hand thread each.
  • The tapered side of the turnbuckle faces down. The ball joint’s flat spot with OMP logo faces outward when connecting the linkages with the ball screws.
  • The turnbuckles can be adjusted in length without removing them from the helicopter.

ESC Install

Wiring

Battery install

  • Use additional hook & loop tape to secure battery to the tray. This will ensure battery does not slip out in the event of a crash.
  • You may have to adjust battery position a bit to get perfect C.G. Make sure you check C.G. with Canopy installed.
  • To remove the battery tray, firmly press the quick release and slide out the battery tray.
  • It is a good idea to have a dedicated battery tray and strap for each battery pack so you don’t have to play around with battery alignment on the tray.

Rotor blades

Swash plate leveling

Swash plate leveling ensures the following at center collective stick position.

  • Swash plate is level
  • Collective pitch is zero

OriginHobbies swash leveling tool makes it very easy to level the swash plate without removing the Rotor Head assembly.

  • Give positive collective to allow installing the swash plate leveling tool.
  • Slide the swash leveling tool below the swash plate from the front of the helicopter. Make sure it is sitting flat on the bearing block.
  • Bring collective pitch back to center. Adjust servo trim in flybarless controller to have 90degrees servo arms. Adjust servo links length so that swash plate is sitting perfectly on the swash plate leveling tool. Notice that the swash washout arms are leveled out. (green line in picture). This will ensure that you have symmetric positive and negative collective pitch.
  • Adjust blade links so that blade pitch is zero. You can do that by folding the blades to be perpendicular to the blade grips and making sure that both blade edges are parallel to each other when viewing from the side. See above picture.

Canopy

Brain2 / Vbar settings

Brain / Ikon setup with EdgeTX

All done!

Congratulations on successfully building your M4 helicopter!
Carefully follow your FBL controller and Radio Transmitter setup guide to correctly setup your helicopter and best wishes for your maiden flight.