Multi Rotor, Quad copters , Hex copters etc. Motor Maintenance checklist

With Quad copters and Hex copters becoming increasingly popular on the scene of RC flight as well as many other types of multi rotors,  it is important to realize that there are some inherent risks involved when it comes to flying one of these.   Electric motors in particular are very unforgiving once they are powered up and a disaster or injury can happen instantaneously and even without warning.  If you are new to multi rotor helicopters be sure to check online in the forums first and seek the help of someone or a group of people with good solid knowledge of the hobby and you will have a safe and enjoyable experience.   Realize that there are people out there who are willing to help you with good advice as to how go about getting into the hobby.   In regards to motor care especially I found some really useful information that you will really appreciate and find helpful if you are multi rotor enthusiast.   This information comes from the Multiwiicopter website and I wrote none of it nor do I take any credit for it but I thought it was important to share it with you.

Setup & Maintenance:

  • This is not a toy – Aviation requires discipline, inspection and risk analysis – Multicopter motors form part of the critical aircraft flight system and become your duty of care when purchased and built.
  • If a motor fails the Copter can fall from the sky and cause harm to person or property below – Always do a full pre-flight inspection on the motors ; A post flight temperature check for thermal stress (hot motor)
  • Schedule of maintenance you must perform includes : –
  1. Remove and add Blue Loctite® to the shaft grub screw – make sure Loctite® does not enter any bearing!
  2. Ensure the Circlip is set (crimped) correctly to hold the shaft in place – inspect closely for any sign of looseness
  3. Carefully apply 1 small drop of OIL to each bearing every 5 hours flight time – with a syringe & needle (new SAE20-50 motor oil) – allow the oil to soak in for 1 min; wipe away all excess oil – oil traps abrasive dust!
  4. Avoid all dusty Landing/Takeoff zones – We recommend Ops from a dust-free rooftop LZ on a 4WD/SUV vehicle or a 1.5m circular plywood dust-free Helipad on the ground to prevent any dust ingress to the bearings.  Abrasive dust entering bearings will shorten the effective life dramatically – inspect the bearngs for wear and replace if worn -Spin the motor – Magnetic cogging will slow and stop the motor which is normal – check for any wear or abnormal sound/roughness/dryness or non-linear friction indicating a bearing failure.
  5. Use high pressure air (can of comressed air – or air line) to clean any sand,dust, grass or dirt away from an engine after every flight
  6. Inspect the wires to ensure the insulation is in-tact
  7. Check that the collect (Prop-adapter) is tight and cannot be pulled off with 2kg force – Dont assume it’s tight – check it in Pre-flight
  8. Use Blue Loctite® to mount the engine screws to the carbon/G10 engine holder.  Check the engine mounting screws never penetrate too far into the engine & short the winding wires
  9. Inspect the prop for any fatigue cracks or white stress lines – immediately repalce any prop suspected of weakness – Routinely replace props every 10 flight hours.
  10. Shaft must be replaced if bent – using a 3mm punch and tapped out – or shaft can be reversed by removing the grub screw and using a bench vise to push it further in and out the other side – then retighten the grub screw
  11. if the motor is observed to be showing some initial warning sign – AN INDICATOR – noted by the pilot but not considered to be a risk by the pilot – and he decided to continue flight ; consider fully the RISK ; this can cause subsequent engine failure and total loss of your aircraft if it has less than six engines. Be aware –
    the most common causes of engine failure are
    • ingestion of FOD (foreign object damage) dirt, dust, stones or debris which can enter the motor during take off and landing – causing trauma (cuts) to the windings or insulation of the windings, damage to bearings
    • breakage of one or more of the internal lead-in stator winding wires by stress (pulling of the wires during ground handling or assembly) – can be caused in incorrectly handling a motor, crash impact tension, carry the craft by gripping the motor assembly wires causing a break inside a motor.
    • magnetic variation – de-magnetising of one or more magnets by placing the magnets on or against other motors/magnets or in magnetic fields – tapping against metal objects of the can of the motor – this partial de-magnetisation can cause the ESC to overheat the engine because the timing cannot be accurately determined by the ESC. Thermal run-away – engine overheats because it is effectively overloaded – Copter is too heavy.  Overheated magnets are permanently ruined.
    • dry-joints or inconsistent  loose push-connections/soldering between an ESC and a motor leading to timing faults – if one of the three connections is loose or not 100% soldered correct – Should you observe ANY motor hesitation or stutter on first power applied 10% throttle – immediately cut power – do not Power-up further or you will blow the ESC  – DO NOT FLY especially relevant for long wiring runs or self soldered joints – USE solder paste – use a Digital Multimeter DMM to check all 3 wires show the same Resistance in ohms – check the wires for breakage or shorts.  Save your ESC by careful observation of problem indicators.
    • Shorting of any motor wire(s) internally to the metal/carbon booms or too the airframe– INSULATION of ALL WIRES annd joints is vital.  – short of the insulation from sharp carbon edges not filed smooth during construction – leading to timing problems or stuttering – Should you observe ANY motor hesitation or stutter – DO NOT FLY – replace the motor /wires/ESC as applicable to the fault – Beginner fault to observe AN INDICATOR – such as hestition then continue to fly – delibrately blowing the ESc – leading to failure and a crash – Pro-Pilots discontinue flight/Land at the slightest hint of a problem – because they realise that warnings are only given once.
    • Poor bearing maintenance lubrication and/or exposure/ingress of abrasive dust leading to bearing breakdown
    it’s VITAL to monitor the temps of all engines on the post-flight check, avoid operations where FOD. dust is a risk and keep motors padded in transport.  It is also recommend to ground the aircraft and 100% locate the cause of any abnormal performance item.
  • NEVER fit the propellers to a motor until AFTER you have fully Tested and set-up the motor and YOU understand that electric motors can start suddenly without any warning.  With proper understanding and maintenance the motors are safe.
  • NEVER run a propeller without FIRST balancing it on a magnetic balancer
  • Do a staic and a dynamic balance of all props for best results
  • Do a hand Maiden – before any flight maiden;  to observe all engines running normally under power applied condition – and all controls responding correctly.
  • During the hand maiden feel the airframe for vibration levels – there should be none – smooth – vibration indicates an out of balance motor/prop and must be traced and balanced.

In conclusion I hope this really helped and I wish you many happy and safe flights !


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