Re-installing software: still the magic bullet

Had some trouble with video decoders a while back; graphedit wasn't even showing a video pin when I opened up a .m2ts file. Today I re-installed Matroska Splitter, and now it works. Meh.

Monterey aquarium members

Went to Monterey aquarium today. Buying the student membership breaks even after two visits, so we decided to get the membership. Now we can go whenever we want! Well, we'll still have the 160 mi / 7 gal / $21 transportation cost, but that's not too bad.

We spent a lot of time looking at the cuttlefish. They're much bigger than the last time we saw them, and they're much more mature now. When they were young, there was a couple fish in the tank with them and they were pretty intimidated by the fish. When startled, they'd jet backwards, and if this trajectory intersected the wall, the bump would startle them into jetting backwards again, right into the same wall. We also got to see them get fed, which was very cool to see.

Anyways, they're big now. They have the tank all to themselves and are now fighting amongst each other. It looks like they're getting pickier about their food, too, because there was lots of food lying around the tank being slowly scavenged by hermit crabs and worm things.

We dropped in on the octopi a few times, but both were inactive. One was pretending (very successfully) to be a rock, and the other was sucked up against the top corner of the glass.

The new flamingo exhibit was nice, but I miss the planted tanks in the old river otter exhibit. We saw a spoonbill standing on a mangrove eating things off its leaves, which was rather odd. The terrariums seemed a little small for birds, though. The exhibit was accompanied by after-school-special anti-carbon messages, which is starting to feel a little heavy-handed, but I think the target there is right. Also apparently the Seafood Watch pamphlets are working, at least according to the aquarium organizers, so that's pretty cool.

Hopping fishes!

We saw them feeding the big kelp tank. A diver went in and all the fishes (including the rockfishes who look dead when they drift along in strange orientations) swam up to her to get the food (restaurant-quality squid, apparently) she was handing out.

Afterwards we talked to the dude narrating the feeding. Learned some pretty cool things. The kelp reproduces in the tank (and grows up, which he calls "recruitment") and grows pretty fast (couple inches a day) in the peak season. The tank water comes from the bay; filtered during the day for clarity, but raw water at night for the nutrients.

Lots of active predation in the tank. Scavengers keep it clear of dead fishes. The fishes reproduce, but other fishes eat the eggs, so there isn't recruitment. Other fishes eat sea urchins, which could pose a problem for the kelp.

Fishes school by size, so you'll have mixed species in a single school. When other species sneak into the tank, they can have trouble when the outgrow the species they sneaked in as...their larger size marks them for predation.

The first set of tuna in the big tank had unnaturally short life spans, and their autopsy showed it was due to cholesterol from the rich diet they were being fed. Oh noes! So they started feeding them healthier food (squid), and life span increased.

Baby jellyfish in a tube

Whelks, with feeding tubes

We also bought some strawberries and artichokes at a farmers' market on the drive down. The strawberries were meh and rotting quite rapidly (a day in a hot car didn't help). The small artichokes (10 for $1, which was what drew us in) are okay; not much of a heart but also not much of a choke. The big artichokes have a tasty heart, but what a strange vegetable to eat!

Updates from the past week

Abbreviated posts:

Saturday (6/5)
Helicopter test flight with Aaron and Max. Had some close calls myself (lost track of heading and then the wind took it far away where I couldn't see it very well), but managed to keep the blades away from danger. Let Aaron fly it. He's got some co-axial experience and some simulator time (well, 5 minutes worth), and was much better at holding a hover than I was. Unfortunately ended with crashing into a bike tire. Broke the landing gear.

Glued the landing gear back in place, replaced the feathering shaft (dunno exactly when it got bent). Lately have been seeing the system act glitchy; I don't know why and I don't even know where to start looking. The most plausible scenario I can think of is the increased vibrations (due to unbalanced blades or other damage) putting excessive noise into the AHRS.

Tuesday (6/8)
A rasbora died! :( It was the loner fish who looked like he had tail damage, possibly as a result of fights. His tail was completely gone when I found him. And that morning, the other fishes were strangely quiet (they usually fight in the morning), huddled together in the center of the tank.

Wednesday (6/9)
Muir Beach and pirates' cove with Max, Bryce, and Nick. A really windy spot. I climb a boulder. Throwing rocks. Fiji water and expensive sammiches from JJ&F.

Thursday (6/10)
Old oto (a.k.a. fat oto) died :( Afterwards, we changed the water, because that's all that we really can do, but water tests didn't show anything particularly out of the ordinary. But it is a troubling spate of fish deaths. While changing the water, did notice the thin tube (between the two tanks) was clogged by a wayward snail.

Friday (6/11)
Family (parents and brother) in town! Presented the helicopter to my dad. Took it out for a test run, but ended up crashing the landing. I think it was a level landing, just a little hard, and then the previously-broken landing gear broke, causing the helicopter to roll over on that side until the blades struck the ground. Feathering shaft is noticeably bent. Damnit. Felt pretty bad about it all.

Went to Mediterranean Wraps for lunch, then made beef Stroganov for dinner. Used beef flank this time, which I didn't like as much as the tenderloin we used last time. Also had watermelon, which was a great treat in the hot weather.

Saturday (6/12)
Went up to Muir Woods and walked around (Hillside trail, ~2 mi). Big sequoias. Very straight. Asexual reproduction through burls, which cause a ring of clonal redwoods to grow around the burnt-out stump of the parent. Also, bendy phototroping bay laurels, which seem to be able to grow out of dead logs. And redwood sorrels, which sleep in the sun and open up in the shade (except for some lazy ones we saw napping in the shade).

The hilly drive up put higher demands on the engine than I'd seen before. Even on the highway, there were parts where full throttle in fifth just wasn't enough (well, not quite WOT...I wanted to avoid the rich burn and other power-boosting tweaks that happen up there).

This whole weekend I've been feeling the car act a little more sluggish than usual. Due to the high correlation between input variables, I can't tell whether this is due to increased passenger mass (~15% of the vehicle weight) or the air conditioner load. Actually, now that I think about it, in addition to slower acceleration, I've also noticed longer stopping distances (which can only be explained by increased mass). An unrelated observation: the A/C is more powerful at higher engine speeds.

Also went to the Golden Gate Bridge visitor center, and the Richmond district's Chinatown. Came back to have dinner with family friends at Jade Palace/Duck restaurant.

Sunday (6/13)
Got up early to get a Master's hood from the bookstore. Graduation today! Turns out the Master's robe is slightly different from the Bachelor's: it's got extensions from the bottoms of the sleeves, as if you might have 2 forearms like the Gatekeepers from Schlock Mercenary. Skipped the commencement ceremony, though; just went to the department ceremony.

Afterwards, went to the San Jose Tech Museum; it was free second Sundays, which was cool, and we spent the whole time going through the exhibits. Not much new since the last time I've been there (there was a Genghis Kahn exhibit, but it was kinda expensive and the rest of the family wasn't very interested), but it was much less crowded than I've seen before, which was nice.

Oh - check engine light came on again; still the neutral position switch and knock sensor, so I just cleared it again.

Helicopter repairs

Parts arrived Wednesday! Very fast shipping: I ordered on Sunday, shipped out from Hong Kong on Monday (well, still Sunday by GMT+8:00 "Pacific" time), got delivered to my house on Wednesday. And all that for $25. So why does it cost $30 to get something overnighted from Oakland? The mysteries of international shipping...

Anyways, hit up hardware stores looking for a 5.5mm nut driver and got laughed out. Finally ordered it from McMaster. Since the nut is recessed deep inside the blade clamp, you need a nut driver with a small OD. 53965A17 is the smallest McMaster has (OD .318" = 8.0 mm), followed by 6919A13 (OD .343" = 8.7 mm), which just barely fits in the blade clamp. The power driver (8534A52) is way too big, and I didn't try out the hollow-shaft nutdriver (7299A19).

That arrived Thursday. The actual repair was very simple; took about 10 minutes. You can see the damaged shafts below: flybar (top) and feathering shaft (bottom).

For size reference, that's an M3 thread on the feathering shaft. The rubber mounting rings on the feathering shaft are damaged, too, but I don't have a replacement so I just stuck it back in. After repair I had to adjust some linkage lengths (just needed 2 turns) to get the two new blades to rotate in the same plane.

Today I flew; everything is fine. I got some sustained hovers and decent landings, which is pretty exciting. Need to do something about the yaw controller at takeoff: the integrator builds up angle error while it's on the ground, so when it lifts off there's a huge rudder command which causes the helicopter to whip around until it's in what it thinks to be zero angle error. Pretty disconcerting.

The goal, though, is not for me to get better at flying, but to improve the control system. So I put in some frequency sweeps (telemetry is working better now), which again was a really bad idea in my small parking lot surrounded by trees and fences. Caught a fence with a blade tip and was down for the count.

Damage report: blade tip smashed up a bit; not too bad. Swashplate popped out of the anti-rotation bracket; that was an easy fix. Flybar might be bent; hard to tell, so I won't reject the null hypothesis of "not bent". The two halves of the helicopter chassis split at the main shaft top bearing; this also happened last time and I think the threads in the plastic are stripped now. Maybe okay to ignore; otherwise will need a longer screw to go through the stripped half and into a nut.

Tried replacing the damaged blade with the un-damaged blade from the previous crash, but the blades are sold in balanced sets and mix-and-match don't work so well. So I kept the damaged blade. Needed to re-adjust linkage lengths to get the blades rotating in the same plane, and added some aluminum foil tape to the damaged blade in an amateur attempt at blade balancing.

Flew again this afternoon. Blades aren't as well balanced as they were pre-crash, but that doesn't seem to affect things too much at flight conditions (though we do see much more wobble while the rotor is spinning up or down). More flying (this time in a larger space) tomorrow.

Badfish, and goodbye to shrimp

Rasboras were fighting again today. One of them had some scale damage near the caudal fin, so it seemed like the fighting could be pretty serious. We identified one (two-stripe fish) who seemed to be a primary instigator, so we netted him out to put into solitary confinement (a plastic jar floating in the main tank).

As soon as we took him out, another fish seemed to take his role in terrorizing the other fish. We were getting ready to take him out when I found one of the shrimp (the lighter-colored one) lying dead on his side, which was quite a surprise because the shrimp have been out and about and growing quite large.

We immediately did a water test, and as I was waiting for the results (ammonia < 0.25 ppm, nitrate 10 ppm, phosphate 0.5 ppm) I hear a tiny splash and look up to see a guilty-looking rasbora at the surface of the water. He immediately darts for cover. Upon further inspection, the jail cell is empty! Yet another instance of jumping rasbora...this is why we have to keep the lid closed.