Archive for the ‘RC’ Category.

Model Aviation Wowness

I’m starting to think about model aviation again. It’s been a long while. I had promised Ma’at that I’d get her in the air at Burning Man 2006. It still seems like a great challenge. There are two big challenges I can think of. First, finding the right plane to put her on. The Trick 1000 didn’t work very well for a few reasons. The second challenge is safety. I want to fly her over the heads of Burners at night. What I want to do is put her on a platform that can (in a worst case scenario) hit a person and have it not hurt. I’ve been hit by my Zagi a few times and the EPP foam and rear-mounted motor made the strike a non-issue. I think it’s possible to make a crash-safe plane but it’s going to take some effort to get such a plane to be able to carry the 12 oz payload of Ma’at and her batteries.

My apartment is strewn with playa-dusty airplane parts as I begin to get things together. While I was looking online for some answers to my questions, I ran across an inspiring video. Give it a view and then tell me flying isn’t uplifting and beautiful.

(Article with video link)
(Video link), Mark Leseberg at Tucson Shootout 2003.

(local version) (26megabytes)

mark-video.jpg

Mostly flying the Trick 1000

That crazy plane.. I’ve had some trouble with it.

First I tried flying it with one 10-cell KAN-1050-knockoff pack. For the first flight, I tried taking off from the landing gear. Blech. It rolled. It went up, it twisted, it went down. I went to launch it again but when I held it in my hands and gave it throttle, it made a funny low buzzing sound. As I was turning it off, I felt something hit the side of my neck in my hair. It was a screw from the motor mount! That was kind of weird since I think the screw had to of hit the prop and gone in a giant arc up and then down into my hair. And I even caught it. Cool. Weird.

When I was putting it together, I had some trouble with the motor mount. See the drawing at the right. There is a mostly hollow rear motor mount (red) that’s glued to the fuselage, and a front motor mount (green) that holds the motor with the two inner (purple) screws. Trouble was (so I thought) that 1 of the 4 screws that holds the front mount to the rear mount (teal) didn’t go in tightly. I thought it would be alright. I was wrong. It is held in just with friction; the screws didn’t have enough bite, the hole was too big… whatever the problem, it didn’t stay in. So after my crash, I got out the CA glue!

It was suggested that instead of taxing, I should just toss it in the air. Gosh darn it if it didn’t work. Problem #2 & 3 cropped up. The center of gravity was way too far back and it was porpoising. Also, I only got 3 minutes of battery life out of it. But it flew!

I got it down in a hurried state, way low on battery (the problem might have been that the speed control was set to turn off at the wrong voltage. I haven’t had time to diagnose that yet… but I digress). It was a rough landing but in one piece. So I stuck 2 battery packs in parallel (I suspected I’d have to do this so I bought 4 packs, all the same :-) ). I brought it out to the field, got ready to toss it, reved it up and CRACK!

The foam forward of the motor mount (denoted in sad yellow) tore off! It wasn’t glued in well enough from the factory! So that was that for my flying day. I got it home, took out the fiberglass tape and epoxy and went to town. The nose ain’t falling off anymore! (See picture)
You’ll also notice in the picture that the bottom screws are larger than the top screws. Well, both of them had started coming loose so I went goofy on it. I drilled out the holes a little larger, cut down some long screws and screwed them in the holes and then I epoxied the shit out of them! The little circles in the fuselage are toothpicks (slathered in epoxy) I drove into it to reinforce. You’ll also notice the wear marks on the prop. It only got 1 more flight before cracking (I flew into a house… the house won)

Blah blah blah…. I got one 15 second flight out of it on Saturday morning. On board was 2 batteries, all the lighting, and the power module for the lighting. It’s a heavy plane! It took off and I couldn’t give enough right aileron to keep it up. I think the lighting was interfering with it. Nevertheless. It flew. Since I was out of time, I repaired the damage (House 1, Plane 0) and boxed it up for the trip to Burning Man. No wait. It didn’t fit in the box. I had to leave for the container in 30 minutes and I didn’t have a box big enough for the tail section!! ACK! The boxes I thought would fit…. didn’t I started driving toward the bike shop to make my own box out of a bike box…. then I turned around and started driving toward Hackettstown because it was closer, and “I would have to find something.” And I turned home with a plan.

I took a utility knife to the epoxied tail. I took a screwdriver to the landing gear. And darnit, I made the plane flat. I made it fit in the hard case I found at a junk yard in Vermont that I had gotten for this very purpose. (Well, I was going to use it for the Projeti, but the Projeti didn’t fit in it. It was only still in the garage because I didn’t have time to get rid of it (and I was secretly thinking that I had to find SOME use for it. Well I did!))

I put the Trick 1000 in a box. Projeti in a box. Tools in a box, supplies in boxes. bike in a box. I strapped the bike box to the roof of the Jaguar (finally, a good use for the Jag!) and I was Brooklyn bound!

My main piece of art, what I’ve worked on for 50 hrs+ MIGHT fly. It MIGHT light up in the air (only briefly tested!). Then again, maybe it won’t. Maybe it’ll melt in the heat of the container. Maybe it’ll rock.

Buying Last Minute Parts

Tuesday: I finished the plane! I put the batteries in. I tested the controls. ACK! One of the servos is bad! ACK! It takes 3 weeks for warrantee service! ACK! The nearest hobby store has recently proven that it regularly doesn’t have the most essential supplies (last week I asked for Deans Ultra connectors and Zagi props. No go.) I called him up and PHEW, he had them. Grumble, grumble, I had to drive 30 minutes each way just for this little 0.2 oz part on Wednesday.

Flaming Lithium Polymer Chunks

The guy at Zeppelin Hobbies told me why they don’t allow Li-Poly batteries at model car races. They don’t just burn, they throw burning chunks several feet. Cool. Imagine one battery blowing up and lighting all the neighboring cars on fire. Rinse and repeat. How’s that for adding an element of danger to models? Cool.

Making Ma’at in EL wire

She’s done! Take a look

How: I got window weatherproofing plastic (it’s lightweight and crystal clear. Thanks for the hint, oh my genius sister!) and 3M packing tape. As I’d go along, I’d shape the EL wire and then tape it to the plastic.

I ran into some weirdness when I tried to run some of the EL wires in parallel. Depending on how I did the positive and negatives, sometimes they’d light in parallel, sometimes not. Sometimes the brightness would be affected, sometimes not. I think the power supply didn’t like having 3 in parallel. I found one configuration that worked by putting some in series…

Projeti Coolness

I took her out today. It’s really a blast. My favorite from today was taking off at 3/4 throttle, taking a moment to verify stability and then giving her full throttle. She pulled out at an 80 degree angle until I told her to stop… about 400 feet. I’d have her go higher but I can’t see her any further away!I lost my 10 cell NiMH :-( I was practicing hammerheads (and getting moderately good, I might add!) when the battery fell out. I foolishly watched the big yellow plane fall all the way to the ground instead of following the tiny little battery. I looked for about 30 minutes but no luck. Well, I guess I’ll be getting a new matched set of NiMHs.

Wow, Cheapbatterypacks.com can build me a 10 cell generic 1050 mah pack with Dean connectors for $20/pack. That’s like 1/2 the price of my local hobby shop, with -exactly- what I’m looking for instead of whatever happens to be in stock.

I’ll wait to put together the Trick 1000 and see how it flies with the LiPoly pack. Then I’ll probably get a double set of batteries.

Cool Neon Order Placed

I wonder how I’m going to get all this stuff on the plane!

Item

Qty

Description

Options

Price

Total

DBB 1 Big Boy Driver- Will power 50- 165 feet of Cool Neon wire.
 
$13.50 $13.50
ACPPC-W 5 Plug & Play Connectors- Wire Side
 
$0.45 $2.25
DF1 1 Fish Driver+ 1- Will power 5- 45 feet of Cool Neon wire. Cut the white wire to stop blink mode.
 
$5.25 $5.25
ACPPC-D 4 Plug & Play Connectors- Driver Side
 
$0.35 $1.40
DPS 1 Lights 4- 20 feet of Cool Neon wire.
Pipsqueak Driver: Original, smaller- add $2
$5.00 $5.00
WHBL_100 15 High Bright Longer- Life wire: 100-199 Feet
High Bright Colors: Purple
$1.20 $18.00
WHBL_100 35 High Bright Longer- Life wire: 100-199 Feet
High Bright Colors: Yellow
$1.20 $42.00
WHBL_100 27 High Bright Longer- Life wire: 100-199 Feet
High Bright Colors: Lime
$1.20 $32.40
WHBL_100 10 High Bright Longer- Life wire: 100-199 Feet
High Bright Colors: White
$1.20 $12.00
WHBL_100 13 High Bright Longer- Life wire: 100-199 Feet
High Bright Colors: Red
$1.20 $15.60
Tax 0.00
Total $147.40
 

(Actually, that’s 2 planes, a bike and some extra neon to round the order up to 100 feet.)

EL Wire, Ma’at, EL Wire Redux

EL Wire

(eeearly morning edition)

Hmaat.jpgmm. I need a lot of electroluminescent wire for the plane! I’m starting the measurements and it looks like it’s going to take 11″ per loop/feather. I’m planning on 48 loops on the bottom of the plane, plus some outlining…. that’s at least 44 feet of wire just for the bottom! Hmm. What does 44 feet of wire weigh???

I have a sample coolneon kit with about 77 inches of the stuff. It weighs 1 oz +- 5%. So that’s 7 oz of wire for the underside… another 4 for the topside, 1.4 oz for a 9v battery. Hmmm 13 oz of payload on a 28 oz plane. Maybe not. I’ll work it out.

PPG gave me the really good idea to look for Egyptian figurines as a model. (yes, I saw her. I think our friendship will survive) I found Ma’at, the Egyptian goddess and embodiment of truth. You’ll likely be seeing an aerial Ma’at over the skies of Black Rock City in a month!

That’s Ma’at on the left and Isis on the right in the picture.

EL Wire redux

I took the Zagi out to do some sample flying

Zagi 400, 26 oz (including motor & battery but not payload) 292 sq in wing surface, Mega 16/15/4 motor, 6×4 prop, Zagi 8 cell 1700 Mah battery, + 10.5 oz of my grampa’s old tools

It flies just great… It flies a little erratic (probably because the weight is on the top of the wing, pushing the center of gravity up) and it’s a little harder to turn (likely inertia) but the big thing I was worried about was that it would sink like a rock and that isn’t an issue, and I needed to lay hard on the throttle (mostly due to me flying in 20mph slightly gusty winds just before a storm (I want to make this project happen NOW!)), and I had to jump a fence to fetch the plane once (When I took off, I lost a 1 oz weight that I had placed mid-wing, that started a leftward spiral that, in order to save from a really hard crash, I ended up hitting a fence and the Zagi tumbled over the fence… hence the climbing. I’m confident that I can put a 13 oz. lighting payload on a plane

Static thrust motor output: NiMH1: 16 oz, Nicad1: 16oz, LiPoly: 23 oz!

That’s a 36oz plane with 16-23 oz of thrust… very respectable for an electric. I had previously gotten used to getting 9oz of static thrust out of brushed speed 400s. Represented as fractions:

Plane thrust (oz) flying weight (oz) thrust/weight ratio
Old Zagi (brushed) 9 26 .35
New Zagi (brushless) 23 26 .88
New Zagi with payload 23 36 .64 (way better than the old Zagi)
New Zagi with payload (old batts) 16 36 .44
Projeti 23 20 1.15 (>1, vertical performance)

After crunching the numbers, I am resolved: just do it.

Out for a little spin and Zagi Surprises

Out for a little spin

Phew. I’m getting used to it. The darn thing scares me it’s so fast! I took the Projeti and both batteries (I didn’t forget them this time) out to the Allamuchy park. I’m surprised to say that, even though it’s only got a 32 inch wingspan to the Zagi’s 36″, that field is only barely large enough. I would zip from one end of the 3 little league fields to the other in no time flat. It was also kind of funny… I’m used to launching while standing at my car and then walking over to a good spot while gaining elevation. There was no need for that any more since she gains altitude so quickly! In just a few seconds, she will fly nearly out of site. I had to try banking left, right, up and down just to tell her attitude!

But I like that I was able to pop it in the car, drive over, pop the battery in and fly. Electric is nice.

I’m a bit concerned that I’m burning out NiMH1. When I took it out of the plane on 7-11-04, it was like 300 degrees hot. The EPS had slightly wilted underneath where it had touched inside the fuselage. On 7-23, I only got about 5 minutes out of it while I got about 20 minutes (Yes, 20 minutes!) out of LiPoly1

Zagi Surprises

I took the brushless off the Projeti and put it on the Zagi. It’s too fast! I can cause dreaded Zagi Flap in level flight! Of course, this also means that I can run it at 1/2 throttle with lots of speed for a very long time. I frown a little at the Zagi for not handling high speeds well, but hey, it’s good at other things like crashing. Which leads me to my next topic…

I was showing off a little for some kids that moved in to a house on Alphano Road, the middle house. Actually, when I crashed, I wasn’t hot dogging or anything, I was just making a sweeping turn near a tall kite-catching tree. And who could blame the tree for not knowing the difference between a kite and a flying wing? I’m just glad it didn’t get tangled up in the branches but fell to earth. I think it might be time to put those coroplast elevons on. The balsa elevons are more CA than wood!

The second surprise was with the batteries. I attached the 8 cell Zagi battery and flew the Zagi. I was surprised to find no difference at all in performance. But shouldn’t an 8 cell pack turn the motor slower than a 10 cell pack?? I didn’t listen too closely but I didn’t notice any difference in prop noise either. Hm! The Zagi battery doesn’t physically fit inside the Projeti so that test isn’t going to happen.

—————–

Battery use estimates:

  • NiMH1 is a 10 cell amalgam of the two old 1100 mah 8 cell packs. Those old packs had lost 1 battery apiece.
  • LiPoly1 is a 2100 Thunderpower 6C battery
  • NiCad1 is my original Zagi battery
NiMH1 LiPoly1 NiCad1

previous
totals

35? 0 26
7-11 2 0 0
7-23 2 1 1
total 39 1 27

.

Projeti Flight!

First flight was with the help of a new friend, Dan, who lives just down the street from me. I guess I’ve been having some bad days and it’s surfaced…. My car’s battery is dead. It’s a bit stressful that I can’t drive where and when I want. So I went to the field in my dad’s car. When I was getting ready to fly, I realized I had left the LiPoly at home. Bummer. Then I reached over to the transmitter and turned it off. But wait, shouldn’t I have turned it ON?! Grrr! I left it on for 2 days: dead transmitter battery! Dan was kind enough to give me a hand seating my NiMH pack and he lent me his transmitter, very nice.If flies fast and high! It likes to go up! It’s got –almost– full vertical performance… With a little speed, I can run straight up for like 75 feet, which is PLENTY. It’ll go up at a 45 degree angle until it’s out of sight. It goes about 90-100 MPH in level flight!

The entire first flight, I flew it as gently as I could, trying to get used to it and reminding myself that this wasn’t a crashproof plane! things got a little hairy with the sun getting in my eyes.

The second flight didn’t go so good. I launched it, it flew about 30 feet and then….  well… large pieces started flying off it! I cut the power and it fell to the ground. It seems that the spinner had gotten loose and the prop vibration tore at the plane. The motor tore out of it’s mount, a not-so-important piece of the tail was chopped off by the prop and a crack in the EPS formed almost all the way across the fuselage about 4 inches back from the nose. :-(

Break out the crazy glue and tape! After a little while, I was ready to go again but Dan had to go (taking his transmitter with him. Jason showed up as Dan was leaving. He wanted to see it fly. I remembered that I had a home-made quick-charger plug for the battery and plugged it in. Surprisingly, I got a near-full peak charge after only 10 minutes on 1.5 Amps (the transmitter batteries are 600Mah AA batteries). I stuck the NiMH’s on and was ready to go in 20 minutes with a 75% charge. I prepped her for flight and let her fly! She went along straight as an arrow out of my hand, I pulled back on the stick and she dove into the ground like a lawn dart! AACK!

I had forgotten that Dan fiddled with my receiver, reversing a wire! I should have done a better flight test! I recall a quote from Cliff Whitney, “When flying inverted, down is up and up is expensive”. The motor mount had held up but the foam holding the motor mount, about 1 inch into the plane gave way, tearing about as large a chunk as possible from the top rear of the plane. When the tail came loose, it chopped through part of rear of the wing, leaving a gash.

Well, after about 30 minutes of gluing and taping, she was ready to go back in the air. I had tried to collect all of the yellow foam from the crash site but I was missing a couple bits. The gash in the wing remains even still. I got her up and she was great. Smooth and fast flying. She rolls like… she rolls quick. I was getting ready to try inverted flight but as it unsteadily came out of the 1/2 flip and nosed toward the ground a bit more than expected, I recalled that I needed more experience with the plane before doing to much with it. Suffice to say, she flies very well.

I don’t think it’s appropriate for the task I was going to put it to at Burning Man. She’s too small, too fast, too unstable. I need something big that can cruise around showing itself off. The Zagi is just about big enough but not stable enough. I’ve got my work cut out for me here!

I’d have taken pictures of all this but my aunt borrowed my camera. I’ll have it back soon.

Here is the Kavan web site (the maker of Projeti)

About LiPolys

With nothing better to do on the plane, I charged, discharged and charged the LiPoly battery to see how much capacity it really had. I got some strange results:The battery is a Thunderpower 2100, with a manufacturing stamp on the label of 6-4-04

  • 6-28-04: I set the Triton charger to charge at 2.1 AH, 11.1 volts. It ran for 69 minutes. Final charge was 12.56 volts, 1.796 AH put into the battery
  • 6-29-04: I set the Triton to discharge at 2.1 AH down to 9 volts. After 56 min, the Triton stopped at 10.5 volts, having discharged 1.635 AH.
  • 6-29-04: I set the Triton to charge at 1 AH. It started charging at 10.69 volts and finished at 12.56 volts, having put 1.654 AH into the battery after 110 minutes.

So, what’s up with the Triton only drawing down to 10.5 volts? And why did it only pull about 1.7 AH instead of 2.1 AH? I called Sal at NESail and he had a lot to say.

First, he warned me very sternly (!) that I shouldn’t ever ever ever discharge a LiPoly on a charger. There’s no need to and it could damage the battery by drawing the battery down too much. Discharging in a charger is bad because, if a LiPoly is brought down too flat, it’s capacity will be permanently significantly diminished; a charger discharges the battery too slowly to hit the obvious 3 volt/cell wall. If you are flying, the high drain on the pack lets the drain work correctly. In addition, a good speed control will tell you when it’s time to come in for a charge. You shouldn’t drain the battery more than 75% or they’ll go bad on you. That’s 1.575 AH on a 2.1 AH battery.

It sounds like the Triton company is aware of this 75% rule. That’s why they the charger only draws down to 10.5v on a 3 cell 11.1 v pack. The Triton charger seems to have a user interface problem. On the discharge cycle, the options it gives are “3v”, “6v”, and “9v”. The obvious implication is that it will draw the cell down to the specified amount but it doesn’t. It draws the pack down to what is considered “safe” flat… on the “9v” setting, it draws to 10.5v. Instead, it should give options like the following: “1 cell”, “2 cell”, “3 cell”. Or “3.7v”, “7.4v”, “11.1v”. Or “3.5v”, “7v”, “10.5v” because that’s what it draws down to.