Too heavy? or Just fine? - RC Groups
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Sep 03, 2005, 06:58 PM
Nem Jr.
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Too heavy? or Just fine?

Just wondering how heavy I can go with a indoor ornithopter?
Span is 16" chord is 2.25" taperd to nothing at tip.
I am shooting for no more than 3-4 grams.
Is that too heavy?
Also, is there a certain formula for these things?
Last edited by Nemesis_49788; Sep 06, 2005 at 11:07 PM. Reason: spelling
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Sep 05, 2005, 12:05 AM
To my knowledge there is no simple formula for ornithopters. There are just to many variables. However if you do ever find one let us know. I have built a number of ornithopters of a certain design I have been working on (watch for a kit coming soon). They have a wingspan of 21Ē and a chord of 4 9/16Ē. The heaviest on I built weighed in at 9.5 grams I think. The normal weight is 8.3 grams. I have never experimented with payload capacity but I can tell you that a gram can make quite a difference in flight time.
I think the free bird has a wingspan of 16Ē but its chord must be at least twice that of yours. Donít remember its weight off the top of my head but Nathan probably has it listed on his site Iíd say if you can hit 3-4 grams you should be fine. Be sure to let us know how it turns out. Pictures are great too.

Sep 05, 2005, 01:19 AM
Nem Jr.
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Thanks for your response,
I am in the building phase right now.
Having weighed all materials prior to building, Materials weighed in at 2.5 grams
Since then I have trimmed them as needed but have not glued the structure as of yet. It lies pinned to the board as we speek. I have added 1.5 grams to the total weight though as an experiment. You see,instead of rolling a balsa tube for my body/fuse I chose to utilize a clear drinking straw. Perhaps alittle heavier than the balsa but still very light weight. It won't register on my postage scale. It only reads grams/ounces up to 5 lbs. I chose the drinking straw for one reason really...(Visual Effect) when flying I hope to achieve the body/fuse dissapearing in flight, so that the only thing the spectator sees is wing and tail. Also, I mentioned that I added 1.5 grams to the overall wieght. This is for cargo......
Picture if you will, darkness, night time flights once the winds are died down. I install/slip a 3volt lithium batt and bright LED inside the fuse, adjust to get the C.O.G. right and let it slip into the darkness glowing bright as can be. How would that be for effect? ....
The battery blink between 0-1 gram on my scale and the LED doesn't register nothing at all. I will include info on this ornithopter in my next post.

Sep 05, 2005, 01:49 AM
Nem Jr.
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My Project

Here is a little info on the ornithopter I am building.
It is called the Lil Iggle or Breadboard Bird.

I am trying to just load pics that contain info on the orni that I am building, if it don't work I will upload the pdf. open it and scroll down to the breadboard bird.
I could use all the advice I can get....
Once I get airframe glued together and model built I will weigh again and upload pics of Model, Battery and LED

Hey, I just thought of something.....If this idea works like I hope it will , maybe I can use it to send a airmail message across the street to the lil lady sunbatheing all the time?..

Thanks again,

Last edited by Nemesis_49788; Sep 06, 2005 at 11:09 PM. Reason: spelling
Sep 05, 2005, 01:50 AM
My mother is a hair dresser and she once found these incredibly small glow sticks, you know the things you snap and they glow, they were supposed to be attached to the hair with clips or rubber bands or something but they were probably smaller than the diameter of a straw. Iíve taken pills larger than these things. I tried some on my light stick and they worked well. Only problem is they only work once.

Sep 05, 2005, 02:05 AM
Nem Jr.
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The PDF is 1.36 mb, it says it is too large to upload....maybe ya can do a search if you are interested, or I will upload photos when I get this thing glued.....Anyways, i will keep all informed....If ya think I might need to know something, please, let me know.

Sep 06, 2005, 11:05 PM
Nem Jr.
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Here is the latest development..

Please excuse the clarity of the pics as they are taken with a pc cam .

Could it fly?

I don't know if the pictures are clear enough but AUW is 1 gram without rubber.

Also, here is the battery and led to slip inside the fuse. glows very brightly and only adds 1 gram.
Last edited by Nemesis_49788; Sep 06, 2005 at 11:16 PM. Reason: Added pic
Sep 09, 2005, 10:58 AM
Nem Jr.
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Ok, here is the update on my lil orni,
I wont flap it's wings under power. I think I built the crank wrong, there seems to be some binding and it stops at the end of each rotation. I knew these things had to be precise, but holy moly....
Flapping range is 80 degrees but when conrods come full travel horizontal it sticks/binds and I have to touch the crank for it to travel another revolution, and then it does it again on the next turn. Any ideas? new conrods? crank? ect.....power is supplied by 2 strands of 1/8 inch rubber 10 inches long.
Sep 09, 2005, 12:34 PM
Thatís a very nice looking ornithopter, from the looks of it Iíd say once you get the bugs worked out of it you should have a good flying airplane. I canít really say whatís causing your mechanism to bind up without actually seeing the crank mechanism and conrod connections. A new ornithopter almost never works right on the first try; they seem to always require an adjustment or two. My best advice would be to make sure your conrods and crank are not catching on anything. It may take some experimenting before you get it to flap smoothly but in the end the frustration and work are always worth it. Good Luck

Sep 09, 2005, 03:36 PM
Nem Jr.
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thanks for your reply. the main crank is supposed to be a simple one built flat,
Sep 09, 2005, 04:54 PM
Nathan Chronister
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It could be that the mechanism is near locking up so that the torque of the rubber band doesn't have enough leverage to continue the motion. Check the angle between the connecting rod and the wing lever (which is the line between the wing hinge and the place where the connecting rod attaches to the wing). That angle should average about 90 degrees, and it should never be more than 60 degrees off of that figure, either direction. If it is, then you need to lengthen or shorten the connecting rod.

You may also want to decrease the crank radius, so that the wings flap through only about 60 degrees, instead of 80. This will give you more torque at the wings, and more power, though of course the rubber band will unwind quicker too.
Sep 11, 2005, 10:30 PM
Nem Jr.
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Working on building another one now. hopefully I will be able to shave 1/10 of a gram off the weight. The crank mechanism was found to be at fault. I was 1/16th off of center on the left wing. model does fly with payload. getting about 1 minute. twice that without payload. After I build a few more of these I might incorperate pager motor/gearbox and simple IR control.
Sep 11, 2005, 11:25 PM
Wow flights of two minutes, thatís great! Sounds like that straw idea paid off. Good luck on your next model.

Sep 12, 2005, 12:55 AM
Nem Jr.
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yeah it is pretty good, but what I am slowly working up to is a 36" flying dragon with RC. Though right now I am building up a little something for the kids on halloween. A 5' tall witch on a broomstick to fly over our small village of Barryton.
Sep 12, 2005, 01:53 AM
Iíve always wanted to build an R/C dragon, fire breathing of course. Iíve had my free flight dragon design on hold for a while, I guess itís time to get back to it.

As for the flying witch, thatís just plane cool! Youíll have too post a picture of that. (If youíre serious of course.)

Easiest way to make a witch fly - shoot her out of a cannon. Not many willing volunteers though. Pity, guess I bought that broom for nothing.

Have fun and try not to terrorize the villagers too much.


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