DLE Section : Tips

Hints & Tips Articles.


Brushless Motor Disassembly

P.S : Before disassembling the motor, if your item carries a warranty, opening and attempting your own repair, will void whatever warranty you have.

 

Motor 01 Rev0

The following article contains a short tips on disassembling the brushless motor. Brushless motor should run smoothly from the lowest to maximum throttle with minimum vibration. We could easily listen to the smooth running noise of the motor without mounting the prop. Crashes from major to minor ones might cause unexpected damage to the motor; causing a rough run and noise, bad vibration and/or even twitching/stuttering at the start of the motor or during lowest throttle. Often, you might be able to hear a clicking or scrubbing noise when you rotate the motor manually. This is caused by the surface contact between the stator and the permanent magnets on the rotor; scratch lines can be seen on the stator and the rotor. Damaged bearings and bent shaft are the primary cause of this phenomenon. However, if the bearings and/or the shaft are replaced immediately, the motor might be restored to normal. Sometimes the motor has already been damaged badly and the phenomenon still present even after replacing the bearings and shaft.

To start disassembling the motor, various tools are required. The safest method is to use the bench press tool, however in this article, the disassembly procedure is done using the tools as shown in the picture below.

Motor 02 Rev0

The first step involves in removing the circlip (E-ring), followed by the collar ring from the rear shaft using the pliers. Be cautious when removing the circlip because it might spring out. If you do not have any spares, do not lose it or bend it out of shape.

Motor 03 Rev0

The second step is to pull and remove the rotor (the bell) from the stator (the body).

Motor 04 Rev0

Notice that there are two bearings attached to the rear end and front end of the stator. The next step is to remove the bearings from the stator. Sometimes, the bearings are easy to remove, and some have a tight fit. Remove one of the bearings using barbeque skewer or any wooden stick to plug out the bearing from the stator. Usually, the front end bearing is easier to remove.

Motor 05 Rev0                        Motor 06 Rev0

After you have managed to remove one of the bearings, use a pin punch tool to push the other bearing out from the stator.

Motor 07 Rev0

Place the stator on the plastic wire spool / solder bobbin and carefully tap the pin punch tool using the hammer until the bearing drops out from the stator.

Motor 08 Rev0

Motor 09 Rev0

Now you can replace the old bearings with the new ones. You might use the pin punch tool to push the new bearings into place. Just lightly tap to prevent any damage to the new bearings.

The next procedure is to remove the shaft from the rotor (the bell). Use the allen key to remove the set screw on the rotor.

Motor 10 Rev0            Motor 11 Rev0

The final step is to push the shaft out from the rotor using the similar pin punch tool technique implemented previously to remove the bearings.

Motor 12 Rev0

Motor 13 Rev0

Now you can replace the shaft with the new one. Carefully tap the new shaft back to the rotor. Make sure the flat surface on the shaft is position directly above the hole for the set screw.

Assemble back the rotor to the stator and followed by inserting back the collar and the circlip to the shaft’s rear end. You are done!

“Unless you try to do something beyond what you have already mastered, you will never grow.”

― Ralph Waldo Emerson


Prepare the propeller before use

Reamer and prop balance tool

 

The driving system plays a primary role in the model aviation. The thrust force produced by the driving system is required to be as precise as possible for an effective and efficient flight. An electrical motor drives the propeller in a revolution motion; providing the propulsion thrust for the flight.

The propeller looks simple, yet it requires precision to produce and to assemble to the model. In this article, the scope is only on a nylon propeller for electric model with direct drive (without gearbox) through a propeller adapter. However, some of this technique is also applicable to other systems which implement a prop adapter.

This technique is optional and some modelers prefer to just use the propeller without any pre-preparation. Most of the propellers provided from the manufacturer are already able to fit in the prop adapter just fine, but some have hub center holes which are required to be enlarged.

There are many ways to enlarge the existing center holes of the propeller. The most precise process is to use a bench drill press, but a proper clamp has to be used for securing the propeller in place during the drilling process. There is also risk involves a propeller damage during the clamping process. Secure it too tightly; it might damage the leading or trailing edge of the propeller blade or damaging the center hub. Secure it too loose; the propeller might fly- off, hurting the people in the area (this should be prevented at all cost).

All these risks also present when you decide to use an electric hand drill. The less precise and safest way is to use manual hand reamer tool. You could just slowly rotate the reamer tool manually by hand; the tapered cone should self-feed to the centre axis of the hole. With this manual tapered hand reamer, you are free from the mentioned risks.

Prop preparation 01

Hand reamer tool                                Reaming

The deeper the reamer feed into the hole, the larger the hole is formed. Be cautious not to oversize the hole. Try to test fit the propeller to the prop adapter after a few revolution of the reaming process and repeat the process until the propeller is just-fit into the prop adapter.

Reamed prop

Another preparation process involves in balancing the propeller. The production process from the manufacturers is already precise, but there are always tolerances in the manufacturing process. Again, this is optional. A more balanced propeller would help to minimize vibration during the flight. Vibration could be small, but even a small and continuous prolong vibration will caused uneven wear on the ball-bearing of the motor; reducing the performance and the lifetime. Besides the wear and tear issue, vibration is the notorious enemy for aerial photography/videography/cinematography. The vibration results in a jelly-like video. This issue is overcome by implementing steady gimbals for the camera.

In this article, only the 2 blade-propeller is discussed. A prop balancer tool is used to show whether the propeller is balanced or not. The propeller is secured on its center by cone nuts on a shaft. For a smaller prop center hole, the cone nuts are configured in such way that the cone’s peak is facing each other. For a larger prop center hole, the one of the cone nuts is swapped for its face orientation. When the shaft is mounted on the tool, the magnets on each end will automatically hold the shaft at its centre axis.

Prop balance config

If the propeller is unbalanced, it should be heavy on one side and one of the blades will rest on the ground.

Unbalance

To balance the propeller, a strip of tapes is used. Try to mount the tape closer to the center as it will reduce the disturbance near the edge of the blade. Adjust the mount position and the amount of the tapes until the propeller is balanced and automatically rest on the center.

 

 

Tapes on prop

 

 

If you have finished with the adjustment, you may finalize it. Try not to mount around the leading and trailing edge of the blade to minimize the change in the blade’s airfoil. You may mount the tapes on both the front and back sides.

Tapes on prop 02

Balanced prop

The propeller is now ready for use.

Prepared prop 02

“Have no fear of perfection – you’ll never reach it.” ― Salvador Dalí


Counterweight made from fishing lead sinkers

C.O.G (Center of Gravity) location is one of the most crucial parameter provided by the model’s manufacturer. The proper C.O.G location enables easy and stable flight. However, some pilot prefer different C.O.G location; deviating from the factory setting in order to obtain unique flight characteristics. They can be nose heavy or tail heavy. In most cases, battery mount location is adjusted to obtain the desired C.O.G.

There are some cases where the desired C.O.G is failed to be achieved, for example when using a much larger and heavier battery or smaller and lighter battery. This might also occur when using FPV models without mounting any FPV gears (just for flying the model). Additional weights called counterweights are used to solve this issue. There are many ways to find additional weight to be used as a counterweight (coins, stones, etc). Solid lead sinkers for casting/fishing are another option.

Fishing lead sinkers

They come in a variety of sizes and weights. You might directly use and load them to your model, or you might want to merge a couple of them into a single shape.

Firstly, the required weight is to be measured or you could try loading some of the lead sinkers to the model until the desired C.O.G location is achieved.

weights

Secondly, construct the mold / die using wooden materials to a desired shape. Cover the internal part of the mold / die with thin aluminium sheet.

Mold

                                      Alu sheet

Finally, the lead sinkers are to be heated until they reach melting point and formed into liquid state. Immediately pour in the liquid lead to the mold / die.

 

Notes : Consult a professional for heating and melting process as the gas fumes from lead is extremely hazardous to human health.

Counterweight

                                Weight loss

“Don’t confuse symmetry with balance.”   ― Tom Robbins, Even Cowgirls Get the Blues


Radio Receiver Antenna Replacement

This is a short tips on radio Rx antenna replacement; in this case FUTABA 2.4 Ghz receiver. Crashes from major to minor ones might cause unexpected damage to your model’s parts. They can be either the model’s airframe or the electronics. One of the examples is the radio receiver or Rx unit which is one of the largest value in your investment.

 

When the model crashed, the Rx unit experienced a considerable huge amount of sudden pull or push force. The mounting Velcro / mounting double-sided tapes might be out of place; pulling the antennas along. The mistake comes when the antenna was secured on the airframe too tightly; the pull or push is sufficient enough to separate the antenna from the Rx unit.

Separated antenna

If we take a closer look at the receiver’s antenna, it requires more than a regular technique to solder the antenna coaxial cable back its header plug to restore the Rx unit back to factory performance.

Coaxial antenna

Therefore, it is much easier and safer to replace the antenna with the replacement parts. In this case, FUTABA provides the antenna replacement parts. The antenna replacement parts come with the header plug, which enable plug-and-play replacement procedure. However, they does not comes with the rubber bobbin ( black rubber ring ); you’ll have to use the originally provided bobbin from the Rx unit.

Antenna replacement parts

Notes : Before disassembling the Rx unit , if your item carries a warranty, opening and attempting your own repair, other than springs and ratchets, will void whatever warranty you have.

Futaba Rx unit

 

 

 

 

The replacement parts can be purchased from your local Great Planes authorized hobby store. Or you may contact directly to Futaba Service Center.

http://www.futaba-rc.com/techsupport/service-center.html

 

Strips of paper on tapes allow the antenna to be fastened in place, but easily remove if the receiver is accidentally displaced from its mounting location during a crash. This will prevent any unexpected antenna damage from a sudden pull or push.

Strips of paper on tapes

      Antenna placement

” Every new beginning comes from some other beginning’s end.” – Seneca


Why UBEC is required ?

An introduction of UBEC to your electrical system might save your model from an unexpected outcome which may lead to uncontrolled plunge and crash into the ground.

 

 

UBEC 01 Rev0

In the basic electrical system setup of model, the ESC has a built-in BEC. The Li-Po battery is connected to the ESC which will power-up the brushless motor, the radio Rx/receiver and all the servos. Most of the built-in BEC have a limited ability to supply power to the radio Rx/receiver and servos without overheating/glitch. When overheating / glitch occurs, the Rx receiver tends to reboot (restart) itself, leaving you unable to control until the reboot process is completed; usually almost 2 seconds. Sometimes during the reboot process, the servos turn to their max travel and then return to neutral position before you can gain control. This will cause your model to maneuver randomly. Your model is still save when the overheating/glitch happens at high altitude, but you will never know when will it happened.

 

 

 

 

Besides the limited ability to supply power, a built-in BEC is commonly a linear type. A switch-mode BEC has a much higher efficiency than a linear type BEC, when using Li-Po battery pack with 4S or more.

    • Linear BEC: a 4S Li-Po battery has a typical voltage of 14.8V, in order to produce BEC output of 5V/1A, the current flow into the BEC is at least 1A, therefore the power on BEC is (14.8V x 1A) = 14.8W. But the useful output power is only (5V x 1A) = 5W, so the efficiency of the BEC is just (5W / 14.8W) x 100% = 33.8%; the remaining power of (14.8W – 5W) = 9.8W is converted to heat energy. This makes the BEC hot and may caused overheating.

 

  • Switch mode BEC: to produce BEC output of 5V/1A, the current flow into BEC is only 0.38A (actual test data from EMAX UBEC manual). The power on BEC is (14.8V x 0.38A) = 5.6W, therefore the efficiency of the BEC is (5W / 5.6W) x 100% = 89.3%.

Therefore, adding UBEC with switch-mode BEC to your system will improve the reliability and performance of the model. There are 2 condition of installing UBEC to the system:

   1. The ESC has no built-in BEC.

The UBEC’s input cable is connected to the battery and the output cable to the radio Rx/receiver (batt channel). No change is required in the ESC connection.

   2. The ESC has a built-in BEC.

The built-in BEC of the ESC needs to be disabled; remove the red wire from the output cable of the ESC (the three-colours-cable which is connected to the Rx receiver). The UBEC’s input cable can be connected to the same Li-Po batt which is used to power up the ESC. This can be done by connecting the UBEC to the Li-Po batt’s balance plug. The header of the UBEC’s input cable is required to be changed to the proper Li-Po batt’s balance plug header.

UBEC 02 Rev0

 

“Don’t be satisfied with stories, how things have gone with others. Unfold your own myth.”

      ― Rumi, The Essential Rumi