A MATERIAL THAT BONDS TO PLASTICAfter years of JB Weld, Cyanoacrylate, & epoxy failures, someone in China finally invented a material that bonds to plastic: SHAPELOCK You might even bypass the shipping costs by driving to Sunnyvale & getting it from this guy's house.http://shapelock.com/Heat it to 150F & it permanently sticks to plastic, allowing repairs to ever broken T-Rex landing gear. It can also be hand molded into arbitrary shapes. Skip the makerbot & use Shapelock to make camera mounts, sensor mounts, antenna mounts, battery holders, carbon fiber joints, fuselage brackets, servo mounts, maybe even motor mounts.Apparently it's equivalent to teflon & can be drilled & tapped. Our main use would be carbon fiber joints & propeller guards.PROPELLER SURGERY
Grinding the 3x2's down to 2.5x2's got them to last 20 minutes instead of 10 before breaking. 3x3's ground to 2.5x3's haven't broken after 30 minutes. The 2S 800mAh battery has a 10min flight time. Got used to the power management to the point where she feels like a slowly responsive copter. Unlike a normal copter, release cyclic & she sort of stabilizes in a hover.She's extremely unstable dynamically. Throttle derived attitude control doesn't seem enough for any tight position hold. She's not likely to stay inside the sonar radius on autopilot. May just put a uBlox on her & retire her.An RPM governer would be nice. Tried a simple PID loop & realized the RPM is too slow & requires too much variation to get very far. An RPM governor works best for constant, fast RPM.Got some long exposures showing position changes in no wind.
SONAR DISASTERSHaving sonar & telemetry on separate boards ended up busted. Sonar can't use laptop beacons for synchronization if the sonar & radio ground stations are on separate boards.Tried using the laptop clock but there's too much latency. The idea with clock synchronization is to broadcast a beacon from the laptop to every microprocessor to get the clock differences.With that, the Marcy 1 ground station was triple busted & we had a joyous time reverting hardware to Vika 1. It would have been better to give the Marcy 1 radio its own microprocessor & have it communicate over UART with the Vika 1 ground station.Fortunately synchronization with Marcy 1 radios works much better than XBees. The XBees added random latency.Properly calibrated sonar gives decent results.
After some sonar flight tests.
Nicely bent from water landings.MARCY-1 FIGHTS THE WINDGot some progress against wind by reducing RPM to get more horizontal thrust. Minimizing RPM gives more horizontal force at the expense of instability. Unfortunately the radio connections are real lousy & lost contact in the end. Not sure if it's having telemetry & remote control on 900Mhz or the use of dipole antennas.THROTTLE INDUCED BANKThis one shows changes in angle of attack caused by Marcy 1's throttle modulation algorithm. Not much bank because she's bolted on a test stand & also because throttle modulation doesn't cause much banking.The magnetometer derived azimuth is sloppy but flyable. The problem is modulating throttle to bank changes the RPM.Now some long exposures showing the extent of throttle induced banking.
Getting clearer that the single PWM monocopter is a lousy indoor sonar demo because of the rotor diameter & the instability required for single PWM control. A large GPS guided monocopter which spins just fast enough to stabilize pitch yet maximize horizontal thrust might work outside.
Went through many ideas for Marcy 2. A partially fabricated single fan with servo controlled vanes was busted on efficiency. A large monocopter that converts into a flying wing was busted because the CG has to change. Steve Morris did that with a clumsy tractor mechanism. Transforming aircraft certainly aren't new.A compact tri rotor using Vika 2 parts is gaining popularity for Marcy 2.M.M.M.Made a slideshow of our early flying photos with real Major Marcy Music. Apparently 1 other human in the world used Major Marcy as a username on a music service so how could we resist making a video. Maybe it was a Jack Crossfire reader.
I'm wondering if its the same stuff as I saw at Maplins in UK, can't for the life of me remember what it was called, maybe it was just the same. hang on I think this was it, Polymorph http://www.instructables.com/id/DIY-Material-Guide:-Polymorph-Plast... Both my girlfriend the sculptor and myself looked at it and thought wow but did'nt buy, perhaps I will now.
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