FeiJi's blog View Details
Posted by FeiJi | Aug 20, 2020 @ 11:55 PM | 2,412 Views
Latest incarnation of my self balancing two wheeler with horizontal axis rotor that allows right and left turns. Now need more powerful gimbal rotor to control sharp and fast turns. Have tried several motor drivers and settled on VNH5019 12amp controller. Now need more powerful motor than the 385 I am using. Tried a 550 motor and it works but jerks too much due to cogging. A coreless motor would be ideal but expensive and hard to find.

I wired the RC receiver to the Arduino Uno to control the drive wheel and steering and it works great.

Self Balancing Gyroscope Two Wheeler (Part 10) Right And Left Turns (6 min 37 sec)

Posted by FeiJi | Apr 06, 2020 @ 09:27 PM | 6,434 Views
Here is a free pdf ebook on how to make a self balancing vehicle. Contains details on my models, problems, resolutions, suggestions, etc.


What I have discovered with my current vehicle model:

1. Vehicle makes right turns very sharply without falling over (gyroscope rotor is spinning to the left at about 10000 rpm) but falls on sharp turns to the left. It also falls making backward right-hand turns but not backward left turns.
2. Programming requires taking into account the natural precession of the rotor and corrections must take into account which of four sectors the rotor axis is in. This is forced precession as you cannot just place the gyroscope rotor at the balance point - that will not work. It is like you have to coax the rotor into a balanced position.
3. Corrections to the gyroscope gimbal must be programmatically made in short (approximately 50 millisecond) spurts with a slight delay following to allow the gyroscope to naturally precess to a balanced point.
4. Balancing requires a gyroscope rotor of mass/total vehicle weight of anywhere from 15 to 20%. Some seem to have been successful at 8% but I think that must be because it is a full-sized vehicle and probably more efficient than at the model level. Not sure.

How can we make sharp left turns (gyro spinning to the left) without falling over and only using a single gyroscope (two gyroscopes solves this problem but has other issues). One possible solution that I have yet to try is to put the gyroscope on a 2nd gimbal and turn it when the vehicle turns (like the Gyro-X car).

Update Aug 21: I have since mounted the rotor on a horizontal axis and this allows right and left turns - just not fast ones, yet. Working now on a stronger gimbal motor to allow faster, tighter turns.
Posted by FeiJi | Feb 16, 2020 @ 07:23 PM | 3,098 Views
I have my gyroscopic two-wheeler vehicle mobile now. It turns left and right though I have not tested sharp turns yet. Need to change the steering linkage a bit and test that out. Usually, gyroscopic two-wheeled vehicles with a single gyroscope will turn well in only one direction and typically fall over in the other direction. I use RC electrics to drive the front wheel and the steering servo. A 550 12volt 18000rpm (no load) motor drives the 360gram gyroscope rotor. Using three 3S 800mah lipos for power, one for the Arduino Uno, one for the gyroscope rotor motor, and one for the RC electrics. Using an LM327 voltage regulator.
Self Balancing Gyroscope Two Wheeler (Part 3) (2 min 30 sec)

Posted by FeiJi | Feb 08, 2020 @ 03:03 AM | 5,334 Views
Here is something a little different: an inline two-wheeler that is balanced with a mechanical gyroscope. I have been building these for several years and finally got one working that uses a servo motor to control the gyro gimbal that keeps the model balanced. I used some of the ideas from Mori, Hiroshi who builds gyroscopic monorail trains and here is his excellent booklet that explains the theories of how they work: https://thebbb.net/free/theories-and...-monorails.pdf

Eventually, my two-wheeler will be RC controlled, except for the gyroscope which is controlled by Arduino Uno.

Self Balancing Gyroscope Inline Two Wheeler With Active Gimbal Control (14 min 57 sec)

Posted by FeiJi | Jan 31, 2020 @ 09:55 PM | 4,304 Views
Nice article showing that sharp leading edge on small models can improve flight performance in windy situations.

Go here: https://newatlas.com/drones/bird-inspired-drone-wing/
Posted by FeiJi | Jan 19, 2020 @ 10:07 PM | 10,905 Views
Yesterday my wife and I visited the Flying Tigers Museum in downtown Kunming. I didn't really know anything about them until we moved here and now I want to document any artifacts, memorials, and cemeteries that are left here....Continue Reading
Posted by FeiJi | Oct 16, 2019 @ 01:33 AM | 3,548 Views
Cut up a perfect new Lighting EPP wing kit into 3 pieces for portability and to carry on my ebike. Was an experiment that worked out pretty well. Kit cost me about $20 so no loss if I failed. The wings are now very stiff, the new wing is lighter than my old one which I had embedded LEDs. I hold the wings together with a couple zip ties. Takes about 5 minutes to assemble it at the field.
All up weight with 64gram 800mah lipo is about 330grams. That includes metal spinner on folding props and a bigger 15amp ESC. The old wing really flaps its wings on a windy day but this wing is very rigid. CG is at 10cm from leading edge. I don't know how anyone can fly with it at the recommended 50mm. Perhaps it is 3D at that point and I can't fly 3D. It is powerful enough with a 3S lipo to move out pretty quick. I fly around at about 40% throttle.

My maiden went ok but on the third flight the battery dropped out the bottom and I flew it down to a landing without any harm. Looked pretty funny flying with the battery hanging below by the wires. Guess that is the inevitable hazard with the battery hatch being on the bottom of the fuselage.
The video is kind of long and drawn out and out of frame sometimes. Maiden plus one flight is at the end. My wife kindly videoed but in portrait mode. I was training her to video my flights but she has already lost interest so will have to self video in future flights.

Very happy with how this wing turned out. I fly at a large university football field and it is perfect for that size field.

Backpackable Lighting EPP Wing (13 min 42 sec)

Posted by FeiJi | Oct 06, 2019 @ 04:05 AM | 3,335 Views
Live and learn I guess. This wing is more versatile than I imagined. I built it according to the designer specs and didn't like the way it flew because I just didn't know how to fly it - almost 3d. Found several videos that built it according to specs and it flies lightly withing a baseball diamond area. I built mine much heavier(almost 300 grams as opposed to 240) and it flies in wind with long graceful loops, rolls and glides. CG can range from 40mm up to about 5mm.

Haven't flown for 6 months until 2 weeks ago and then today. I love flying this plank as it looks like a bird in flight, is easy to control, very predictable, loops and rolls nicely and is a just cool looking wing. Am located now in Kunming, Yunnan, China, the eternal spring city, where there is always a nice day popping up year-round to fly. I just ordered another one of these kits as this one has grown heavy with the LEDs in the wings. The ESC is located outside the fuselage to keep it cool. The little 1908 2050kv motor is a little small and warms up a bit but I haven't burned it out yet. I use a 3s 800 mah because the 2s is fine for poking around but I like to fly faster sometimes. I need to learn how to fly inverted - never learned. Guess I will get out the FMS.

Lighting EPP Plank WIng Oct 2019 (7 min 43 sec)

Posted by FeiJi | Sep 07, 2019 @ 02:52 AM | 3,454 Views
John (Jack) K. Northrop's final interview on why the YB-49 flying wing bomber contract got cancelled by Secretary of Air Force Symington. Dirt bag.
At least Northrop was vindicated by the B-2.

Flying Wings - John K. Northrop's Final Interview - 1979 (28 min 7 sec)

I haven't flown in quite a while but still turn to wings for the most fun. Still flying my Lighting forward swept wing that just won't break.
Going to get out next week for sure.
Posted by FeiJi | Sep 22, 2018 @ 01:32 AM | 6,211 Views
This is a neat article about using acceleration and roll torque sensor readings to make course corrections for better thermal navigation.
Posted by FeiJi | Aug 20, 2018 @ 07:03 PM | 6,871 Views
In making my epp plank wing I had inadvertently made a crushable fuselage - shock absorber when I extended the front of the fuselage by putting a smaller diameter rod inside a larger one. When I crashed nose-on the fuselage collapsed and just wrinkled up the epp foam and the motor just popped off, no real damage. Just hot-glued it all back together again.
Wish I had taken photo of fuselage all crunched up. Hopefully it wont happen again. I had just launched my plank but it was responding to a turn so slowly because the tail was loose and bending back and forth.
Posted by FeiJi | Aug 14, 2018 @ 08:00 PM | 6,670 Views
Added little nose wheel to drag out landings a bit. Seems to land nicer than and with less shock than just a skid. Now want to raise the nose wheel to give prop ground clearance to see if delta can take off from the ground. May have to change motor and prop to give it more thrust.
Update: I raised the nosewheel to provide clearance for the prop- did takeoff from the ground. It worked but was so unstable in the air that I clipped the nosewheel on the ground and it broke off. Wish I had videoed it - was funny and cool at the same time. Will glue it back on and try video sometime.

Delta Take Off and Landings With A Nose Wheel (2 min 16 sec)

Posted by FeiJi | Aug 13, 2018 @ 02:23 AM | 6,916 Views
Epp Plank finally flies. It flies fast considering it has a slowfly prop and tiny 2206/1400kv motor. It is heavy, 450 grams and I have to really heave it to get it into the air and then it sort of fights its way up. Way under powered plane but great once it gets going. Unfortunately I had a tiny ESC on it and it was too much at full throttle. Plane doesn't really land, it just kind of falls out of the sky onto the ground. But built Ford tough. Looking forward to getting this one up to speed. It sounds kind of cool because one end of the wing is open. Also replaced crooked control rods with stronger straight ones cause they were bending - that's why it ended up in a tree. Got it down with a 5 meter bamboo pole.
See if you can hear when the ESC gives up the ghost.

EPP Plank Maiden, Fourth Flight and ESC Expires (1 min 9 sec)

Posted by FeiJi | Aug 01, 2018 @ 10:52 PM | 6,785 Views
This is a lot better than the maiden. Smooth takeoff and landings, tight rolls but it just kind of flips over on loops. Very pitch sensitive. Think it is because too much play in the elevons. Elevons are too large too but if I fly it more aggressively then that makes it more fun. Don't like to use expo.

EPP Delta Second Flight (2 min 25 sec)

Posted by FeiJi | Aug 01, 2018 @ 07:15 PM | 6,782 Views
Got this headstrap that can hold my mobile phone which has a great camera. Much better than my micro camera which had such a small field of view that it was difficult to keep the airplane in sight.
Posted by FeiJi | Aug 01, 2018 @ 06:10 AM | 7,124 Views
Pretty much finished building this plane. It ain't pretty but it sure is strong. AUW is about 14 oz and wing area is about 270 sq inches so WCL is about 6. Should fly. Got a tiny motor 2206 1400kv with a slowfly prop but thrust will be about 1:1. Going to be an interesting maiden.
Used some servo arms for the control horns.
Rubber bands holding wing on but may use bolts.
Rubber bands holding hatch on but will use magnets.
If it flies then will try a larger motor and proper prop.
Also would like to build second very flat wing to see how fast it will go.

Raining so much lately just cant get out to fly.
Finally got a proper headgear to hold my cell phone for taking video.
Posted by FeiJi | Jul 30, 2018 @ 07:23 PM | 10,103 Views
You gotta watch this thing take off and land. Incredible.

DRACO - The Most Badass Monster Bush Plane EVER! (20 min 37 sec)

Posted by FeiJi | Jul 30, 2018 @ 12:55 AM | 7,518 Views
Wow, awful maiden - too many problems.
Servos were reversed so nosed into the ground when I thought I should be pitched up. Prop mounted backwards. Servos loose. Bent motor mount on first take off. CG too far back. Windy.
So fixed all those except CG and it flies - but motor angle is down because of motor mount so will redesign motor mount and it should fly fine.

This micro camera is awful - audio out of sync and video got sped up. Ordered a head mount for my mobile phone as I like the video it takes.
Next flight should go much smoother. It does have a lot of lift and the tiny motor still can make it scoot. Put a proper propeller on it and it should really move.

Scratchbuilt Delta Maiden (0 min 58 sec)

Posted by FeiJi | Jul 21, 2018 @ 10:41 PM | 7,511 Views
Started building a plank using 5mm (and a little 9mm) EPP and carbon fiber fishing pole tube sections. Will skin in 5mm foam and then laminate. Won't be pretty but will be strong. Will build wing same way. Love foam and hotglue and just eye balling it.
Posted by FeiJi | Jul 19, 2018 @ 09:13 PM | 7,287 Views
Not quite finished, needs a couple of hatches made but it is functional and ready for maiden which I could do tomorrow but will probably wait to get a headmount for my phone camera to take videos. CG is back about 23 cm and had to use a little ballast to get it to balance. Could use a much heavier motor and/or battery with more thrust - this little motor gives about 1:1 but the lift should be awesome as the AUW is 340 grams. I added some tape covered skids on bottom to protect fragile leading edges and to keep motor mount from digging into ground.

If it flies nice I might try faster prop rather than this slowfly prop, and add a rudder with 5g servo. Also could go with a bigger motor.

Excited to fly it but am thinking about my next project already which will be a scratchbuilt hotliner using same 5mm epp foam and fishing pole tubes and just elevons with only a vertical tail.