• Contact Me
  • Archives
  • Categories
  • Archive for April, 2010

    Week 11 | Final Proposal – “Scout”

    2010 - 04.08


    For my final mechanisms project I would like to build a twin tilt-rotor remote controlled helicopter.  I am calling it “Scout”.  I found that most types of remote control helicopters are very hard to fly for beginners.  Current R/C helicopter design come in two style coaxial rotors and single rotor with a tail rotor.  The coaxial rotors offer very stable flight but are not agile.  The single main rotor design offers great maneuverability but are hard to fly for novice users.  I want to create a hovering aircraft that is easy to fly and very nimble.  I also want the helicopter able to carry loads such as cameras and small payloads.

    I will be building Scout out of LEGO Technic building blocks.  I choose to build Scout out of LEGO bricks for several reasons.  First, LEGO bricks are a great prototyping platform.  I can build and rebuild my ideas very easily.  The cost of materials is cut because I can reuse LEGO bricks.  If I were to use a material such as aluminum once I cut a piece thats it I cannot go back.    Second, LEGO bricks are accessible to everyone.  I want people able to build Scout on there own with minimal amount of tools.  Third, going back to my first point, LEGO bricks offer modularity.  If I decide later that I want to add another battery bay or a camera arm to the helicopter, I can easily snap those parts into the main design.

    I will be using two electric ducted fans (EDF) for the propulsion.  The frame will be made out of LEGO Technic.  I am using several kits to build the helicopter.  I need to use several kits because one kit doesn’t include all the parts I need to build this helicopter.

    Here are the LEGO Technic  kits that I will be using:

    • LEGO 8297 Off Roader
    • Qty. 2 – LEGO 8265 Front Loader
    • LEGO 8258 Crane Truck

    I also acquired various parts such as gears and shocks off of eBay.  The helicopter is essentially two helicopters in one, hence I will need two of everything.  Each EDF will need an electronic speed controller (ESC), and battery.  I will also need a decent radio system.  I choose the Futaba 7C 7-Channel 2.4GHz Heli with 4 S3152 servos.  I choose the 7C because I need to do servo mixing.  Servo mixing is when two or more servo move together with only one joystick movement.  Cheaper radio cannot do this function.   The motors I will be using are 3600kv Outrunner Brushless Motors.  I will be using two 45A Brushless ESC.  The batteries to power Scout are lithium-ion polymer (LiPo) batteries.  I chose two 11.1 volt 2800mAh 30C batteries.

    Scout isn’t cheap but compared to current helicopter in it’s class it is a bargain.  I sourcing the EDF and batteries directly from Hong Kong, China.  I saving over $300 ordering directly from China.  All the electronics parts are made in China.  The US stores order their parts from China.  I am cutting out the middle man by ordering directly from China.  The downsides of ordering from China instead of order from the US is the shipping duration is weeks instead of days.  The other issue is the build quality of parts can be can be hit or miss.  You may order two batteries, one battery may operate perfectly while the other is DOA.  Chinese seller will replace your defective battery but you will have to send them the defective battery and they will not reimburse you for the return shipping cost.  Even with the risk of a DOA parts, it is still cheaper to order directly from China.  Price list of Scout are below.

    Price list:

    • LEGO 8297 Off Roader….$130
    • LEGO 8265 Front Loader….$80  x2
    • LEGO 8258 Crane Truck….$250
    • EDF with Motor and ESC….$48 x2
    • Futaba 7C heli with servos Radio System….$350
    • 11.1v 2800mAh 30C LiPo Battery….$25 x2

    Grand Total $1036


    March 15 – April 10….Order supplies

    March 20 – April 16….Begin Construction

    April 17 – 20………….Begin testing and setting up the radio

    April 21 – 27………….Test flight and revise

    April 29……………….Present

    Here is my concept design for Scout.  I used Omnigraffle to create the concept design.  I measured the parts and input them into Omnigraffle to get an accurate scale of my design.

    Scout Diagram

    First Prototype of Scout

    Scout Proposal PDF

    The PDF proposal also includes a part list with the weights of each part.  I also calculated the total power to weight ratio of Scout.

    Telemetry Receiver vs. Uniden BC346XT-Round 2

    2010 - 04.06

    Taking the advice from Eric Rosenthal I retested the Uniden radio receiver against Tony’s telemetry radio receiver.  I setup the Uniden by turning off all the auto features and manually controlling the frequency stepping.  I used the good collar which has a frequency of 148.500 MHz.  The setting that Eric Rosenthal recommended were set in the first round of testing and remained for this test.  The only change was I set the radio to manual mode instead of automatic.  The second test mimic the first.  I set the collar at a fixed position while I walked away from the collar with the telemetry receiver and the Uniden receiver in my hand.  One curious fact that I found in conducting the test was stepping the frequency higher and lower from the base of 148.500 MHz proved to increase the reception of the signal as I increased distance from the collar.  I stepped the frequency .1 KHz on the telemetry receiver and I stepped the frequency 10 KHz on the Undien (this is the minimal step increment for the Undien).  When I heard the signal dying off I would increment up and down the frequency to improve reception.  This was affective for the telemetry receiver but doing the same to the Uniden did not result in a better reception.  Both receiver received a clear signal for about 300 feet.  After 300 feet the Uniden receiver began to lose the signal as I walked further away.  In short the first test that Zeven and I did were accurate.  The settings that Eric suggested were indeed what we had configured for the first test.

    No change the Uniden scanners won’t work.

    Week 12 | Final Project Proposal – 3D Audio

    2010 - 04.05

    For my final Nature of Code project I want to continue  building upon my Audio Analyzer.  I would like to 3D audio using only two speakers.  The process to create the effect of 3D audio is to invert the left channel. Next, is  to reduce the amplitude of the left channel and feed into the right channel.  This process is done to the right channel but vice versa.  The effect is a binaural 3D sound field.  Currently, I have never tried this process and will see if this process works.

    Audio Analyzer  Mac App

    Source Code

    Week 10 – Free Body Diagram | Car Jack

    2010 - 04.01

    This is a free body diagram of a car jack. This free body diagram indicate some of the force that are acting on this car jack when in use.  Fn is the normal force pushing up from the floor.  Fg is gravity pushing down on the car jack. Ft is the torque force being applied by the user.  Fl is the lifting force being generated by Force torque.