gliding/climbing time ratio - Page 2 - RC Groups
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May 19, 2004, 04:07 AM
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That is right Willi. The thing with servo works. Karel
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May 20, 2004, 11:08 AM
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Willi,
do you use motor controller brake for wing locking? I do not understand why your system works so good and mine so complicated not better. Maybe that your wing is lighter as mine 100g. Now i begin braking in upper position of wing, just before i set speed to fix value. But brake way changes with accu voltage. I can set this speed from transmitter and so i try to stop in locking position. If wing stops far from posi than PIC tries once more and more and i can change speed during this procedure. Complicated and probably not better as your system. Karel
Last edited by kaja; May 20, 2004 at 05:07 PM.
May 21, 2004, 08:04 AM
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,,,
Last edited by wmueller10; Nov 04, 2007 at 08:58 AM.
May 21, 2004, 05:20 PM
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Willi,
my max flapping rate is about 4/s, wing ends flapp +-10deg from main wing. Main wing flapp about +-5deg on ends. Karel
May 23, 2004, 10:08 PM
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,,,
Last edited by wmueller10; Nov 04, 2007 at 08:58 AM.
Jun 08, 2004, 05:01 PM
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Willi,
i read it again, i think you maked error. It is not possible , i think, 137m in 33s descent. It will be 4m/s descent/s, impossible.
Karel
Jun 08, 2004, 08:53 PM
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,,,
Last edited by wmueller10; Nov 04, 2007 at 08:58 AM.
Jun 11, 2004, 06:49 PM
Nathan Chronister
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Time is much easier to measure than altitude. I suspect your altitude was somewhat overestimated rather than the time being off. Could you describe the procedure you used with the Estes Altitrak device? It will only be accurate if the ornithopter is directly above a known point on the ground. That's fine for rockets as they tend to fly more or less straight up. You could work out a signalling system. For example, when the pilot has the bird directly overhead, he signals the tracker, who then records the altitude. This will still be sketchy because it's hard to judge "directly overhead" and the ornithopter is moving horizontally so it won't stay in position while the measurement is taken. The longer your baseline, the less your measurement will be affected by the horizontal position of the ornithopter.

Estes also sells a cheap barometric altimeter for rockets, available only as part of the MaxTrax starter outfit. It would be light enough for an ornithopter to carry, but it would affect the climb and glide performance in some way.

I just calculated a climb/glide time ratio from some video footage I shot this morning. The climb was 2:49 and the glide was 28 seconds. This is with a 2-cell lipoly and a 10 gram payload so it can't compete with your 3-cell setup. Also the glide was in pigeon mode and it was windy which probably interfered with the climb rate. I had it at or near full throttle the whole time as my goal was to get some high altitude shots. Unfortunately the wind was starting to pull the bird downrange so I had to land. The highest altitude reached was probably something like 300 feet.

If I measure the height of some objects in the video I may be able to get a better idea of the height reached. It took 27 seconds to reach the height of the light towers surrounding the field. It took 20 seconds to come back down to that level when gliding. Assuming linear climb and glide rates, the altitude was 6.3 or 3.5 times the height of the poles, depending on which you go by. Oh well I guess that's about as sketchy as Altitrak.

The discrepancy could be accounted for by the higher winds aloft and by the initial dive at the start of the glide. Also the battery would have more power in the beginning of its run.
Jun 11, 2004, 07:54 PM
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the interesting thing would be to compare the times you get with F5d or similar powered glider classes.

At low subsonic mach numbers (as long as the prop diameter is less than the wingspan!) ornithopters should rule - thus if an ornithopter doesn't beat a prop plane of the same span and wing loading that's a clear sign of room for improvement.

M
Jun 11, 2004, 08:29 PM
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KOROBELNIK's Avatar

Eagletreesystem !!!!


According to me, the most simple means would be to use the eagle tree system (recording of height / has the driving stop)
http://www.eagletreesystems.com/Flig...roductInfo.htm
Regrettably: no available time at present to make this test
Robert Korobelnik
Jun 11, 2004, 08:54 PM
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,,,
Last edited by wmueller10; Nov 04, 2007 at 08:59 AM.
Jun 12, 2004, 12:51 PM
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,,,
Last edited by wmueller10; Nov 04, 2007 at 08:59 AM.
Jun 12, 2004, 02:45 PM
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Yes, logger like http://www.lomcovak.cz/a2/a2.html is perfect for measure altitude and time.
Karel
Jun 14, 2004, 10:06 AM
Nathan Chronister
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Rocket people also use two and three station tracking systems. If you can get a bunch of guys together this would allow you to pinpoint the exact location of the ornithopter in three dimensions, without adding any weight to the bird. The Estes technical report on tracking techniques has some info on how to do this:

http://www.esteseducator.com/Pdf_files/1976clas.pdf

This publication only shows a two-station method which requires that the ornithopter is in line with the two tracking stations. In other words, when the ornithopter gets in line with the two stations that's when they know to take their measurements.

A three station setup is also possible, though you'd have to do a web search to find out how to do the calculations (or figure it out yourself). You would use a timing signal to make sure all three trackers take their measurements at the same time. A loud auditory signal would work, as long as the source is equidistant from the tracking stations.
Jun 14, 2004, 06:29 PM
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,,,
Last edited by wmueller10; Nov 04, 2007 at 09:00 AM.


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