Engineering design of measuring instrument for testing propeller thrust

This mechanical design serves to measure the thrust generated by the propeller.  In the world of aeromodelling, to design a model aircraft  require  the performance datas of thrusts that generated by the propeller. This will find the suitability of the propeller for the type of aircraft.

Overall, the mechanical system can be divided into several parts:

  1. Pole
    Serves to hold the thrust by the propeller. At the bottom there is a weight load that does not shake.
  2. Slider
    Is a moving part which rests two linear bearings. This section is used to hold the motor / engine and propeller.
  3. Motor/Engine and propeller mount
    Serves to hold the motor/engine and propeller. This section will vary according to the motor/engine.
  4. Load cell
    Sensors that work mechanically, driven by a slider that moves as result of thrust backward.

This mechanical system can be used to test the thrust by using electric motors or engines. Thus it will become easier to get the appropriate size of the propeller.

The data can be obtained by using a mechanical system are:

  1. Relationship between the RPM with the generation of thrust. 
  2. The relationship between RPM and current/power which is absorbed.
  3. The relationship between the current/power which is absorbed and thrust.

Point (1) The first can be used to obtain the performance of the propeller (the motor has more power), the second is used to obtain the size of the propeller in accordance with the motor / engine specific.

Point (2) can be used to calculate or test a long fly to the configuration of the motor, propeller and certain batery capacity (mAH).

Point (3) can be used to calculate the efficiency of the power absorbed by the thrust generated. 

How it works

 

The main principle of this mechanical is the Motor/Engine and propeller can move through the slider. In order to be a little friction, slider is associated in two linear bearings. The use of two linear bearings also serve for the motor does not rotate. If the wind direction toward the front, then there will be thrust to the rear. One end of the slider there is a “load cell pusher” that serves to suppress the load cell at the time when thrust generated. By adding a signal conditioner, the output voltage of load cell can be converted to digital by using the ADC.

Motor/Engine Mount

In order to hold the motor/engine include propeller need mount that can joint to slider. This mount has a variety of forms according to the motor / engine that is used.

Load Cell

To measure the thrust with a direction to the rear, I use the sensor “load cell”. 

Load cell specification is: 

  1. CAPACITY:  15kg(30lb)
  2. RATED OUTPUT:  2.0 ±0.1mv/v
  3. ZERO BALANCE : ± 0.5 % F.S.
  4. OUTPUT EFFECT ON ZERO: 0.03 %F.S. ( within 5 minutes)
  5. CREEP: 0.030~0.05 %F.S. ( within 5 minutes)
  6. NONLINEARITY ,HYSTERESIS AND REPEATABILITY: <± 0.03 % F.S.
  7. INPUT IMPEDANCE: 395±5 Ohm
  8. OUTPUT IMPEDANCE: 350±5 Ohm
  9. TEMPERATURE EFFECT ON OUTPUT %OF APPLIED LOAD: ± 0.03, %F.S./10c°
  10. TEMPERATURE EFFECT ON ZERO %OF RATED OUTPUT: ± 0.8,%F.S./10c°
  11. EXCITATION VOLTAGE: 10 Volt
  12. INSULATION RESISTANCE: 300M W
  13. PRECISION GRADE: 0.03% F.S.
  14. MATERIAL: Aluminum Alloy 2024-T351
  15. SAFT OVERLOAD:  150% F.S.
  16. STORAGE TEMPERATURE: -25 to +70 deg. C
  17. OPERATING TEMPERATURE: -10 ~ 40 deg C
  18. MAXIMUM PLATFORM SIZE: 150×200 mm
  19. CONNECTION:
    (Red: +Excitation; Black:-Excitation
    Green: +Signal; White: -Signal)
    4 leads, flexible stranded wire – length 200 mm , PVC insulated AWG 28, UL listed 

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Avatar of Bambang Siswoyo

About Bambang Siswoyo

I am a college lecturer since 1988 at UB (University of Brawijaya) in the electronics department. My experience: Applications of Microprocessor system, Applications of Control System, Applications of Field Programmable Gate Array, Computer Programming in computer instrumentations. My hobby: Music especially playing the saxophone, hiking and exploring the countryside.
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