askman's blog archive for April, 2012 - RC Groups
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Archive for April, 2012
Posted by askman | Apr 18, 2012 @ 09:40 PM | 12,841 Views
well, I got my gemfans. they are nice blade. very well suited for DJI 450 and 550. you do need to drill out the hub. hub diameter is similiar to DJI blade, but with carbon reinforcement, the blades are much stiffer and should be stronger. I used step drill to get it close and reamed the bore hole to .3135. tight fit on the motor. they needed very little balancing, and it was ready to put on.

One thing I noticed about puttng on the new blade were that my 450 and 550 both were bouncing around more in the wind. they were no longer solid anymore.
so, I did a quick and dirty experiment to determine the cause, most obvious being the diskloading.

my 450 were at 1.5kg, and 550 were at 2.6kg. both with 8" and flew well in wind. this is about 200sq in and 300 sq in disk area. 1.39sqft and 2.08sqft leading to 38oz/sqft and 44oz/sqft. both flying very well.

with 9" blade, same weight, my disk area is now 254sqin and 382sqin. 1,76sqft and 2.65sqft which lead to disk load of 30oz/sqft, and 34oz/sqft.

while hexa was more stable, it still was not as stable as the quad with 8".

so, to prove this test out, I added weight to quad and brought it upto 1.85kg, which brought the diskload to 37oz/sqft and now it was almost as stable as before. . I've brought the f550 to 2.9kg and also repeated the test. and it was same . (about 40oz /sqft) very stable.

so, at least in windy condition, naza really...Continue Reading
Posted by askman | Apr 17, 2012 @ 03:04 PM | 11,410 Views
well, panasonic GF3 is getting a workout on my f550 with naza. It is a great camera and great value. with firmware hack, the video mode is as good as anything available. its four third size sensor only 22% smaller than nex-5n sensor, and used in many dslr.

anyway, I was testing my F550 with roll stabilization and tilt connected to the naza reg (roll servo had its own reg) and I got hit by glitches.

this basically reaffirm that you should never power the servo off regs that your multicopter depends on. lol. I did manage to land, but I was very nervous and I made record controlled descent. 8" props at 2.6kgm hexa load is still usable, but near the limit. I am waiting on the 9x45 from gemfans.

anyhow, here is the video.

GF3 test 4. tilt connected to RX. but powered by naza big mistake (1 min 38 sec)

update on 4/25/12
well: I finally tracked down this issue, and it was motor to esc connection. I swapped the esc out, and it is no longer an issue. I've tested that esc on ground, and it still works, so I am assuming connector issue.
Posted by askman | Apr 16, 2012 @ 10:39 AM | 11,261 Views
I finally got my gopro with sunex working well and fully focused. that was total pain to do. I finally used a street sign down the road to focus it in. just lot of iteration in 1080 mode to get it looking good in video . once that was done, 720 mode also looked good. I am using DJI 450 quad with 8" blade and naza. about as small as you can go and get great results in video

here is 1080 mode video
gopro 1080p.wmv (2 min 59 sec)

and here is 720 mode. testing fast panning (was 60fps down encoded to 30fps in sony vegas. no stabilization though still)

gopro 720r3 mode test using dji450 (3 min 55 sec)
...Continue Reading
Posted by askman | Apr 15, 2012 @ 10:29 AM | 11,700 Views
I've been doing lot of research into flight behavior and props on multicopter. Some just affirmed the old ideas and found some new ones.

This whole enterprise started with report of DJI 10" props breaking in air and trying to find alternative. Graupners are the best by all account and would have gotten the set, except for their current lack of availability precluded that for myself. So, I started testing props

The anecdotal evidence has always been to use light weight props, and this has always been old standby APC SF and EPP props. I've also had some hobby king 10x6 set on hand (they are very affordable) and purchased a set of 9x4.5 APC EP props. (figuring that they are similiar to graupner e props)

after testing, I find that APC EP props are not suitable for multicopter. they do work, but I could not get rid of wobble due to their weight. wobble was not big, but it existed in all condition and could not be tuned out. may be they would work better with slightly bigger motor, but not with stock DJI 920kv motor. also, I could not get 9x5 GWS 3bladed props to work well with naza. bit of wobble. could be due to balance issue as I could see at least 1 prop badly out of balance. (but again, 10x6 had at least as bad a balance on 1 prop and flew well) it is interesting, as gary had good luck with GWS and heavy loading. the motors do stay cool with gws 9x5. gary did have trouble getting rid of all vibration with gws, so not great...Continue Reading
Posted by askman | Apr 11, 2012 @ 06:41 PM | 9,799 Views
well, I am finally happy with the new Slow Stick LG. bit heavier than my original ones from 6 years ago, but lot stiffer. The new gopro adapter and new 4.4" gimbal is designed to be able to mount KK (openaero firmware) or openCC board.

the budget 4.4 gimbal is designed to use micro servo using pushrod to give tilt only control at affordable package with the LG.

it will be available in my website.