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Old Jul 03, 2012, 02:41 PM
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I have not done this is sometime now, hope it does not bit me.

Here is my idea, using two motor/props, the one on the bottom a higher pitch. The props shown are just for illustration and will be replaced with an APC 8x3.8 on the top and an APC 8x6 on the bottom. Reason for the Pitch differences is, the second prop will accelerate the air produced by the first prop.
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Old Jul 03, 2012, 02:46 PM
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not a need for dual prop... the Dia-changing shroud will increase pressure on downstream.. if the d is constant... different pitch prop will create a vacuum like state in between.. either the lower prop cant get enough air.. or the top prop get dragging faster due to the demand of more air (cant think of how to explain more clearer)
Old Jul 03, 2012, 02:47 PM
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Also ...
This reference is for flow measuring nozzles. But their shape useful because in flow measurement one wants to have a laminar flow in the device because unsteady or turbulent flow will mess up the readings. The reference has drawings with proportional dimensions of nozzles that could be used a shrouds.

http://edge.rit.edu/content/P12056/p...167-3-2003.pdf
Jim
Old Jul 03, 2012, 02:48 PM
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Ok, I understand. We will start testing with just one prop/motor.

Thanks for the input.
Old Jul 03, 2012, 02:49 PM
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Quote:
Originally Posted by Jem3 View Post
Also ...
This reference is for flow measuring nozzles. But their shape useful because in flow measurement one wants to have a laminar flow in the device because unsteady or turbulent flow will mess up the readings. The reference has drawings with proportional dimensions of nozzles that could be used a shrouds.

http://edge.rit.edu/content/P12056/p...167-3-2003.pdf
Jim
Thank you, have some reading to do.
Old Jul 03, 2012, 02:54 PM
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Now this brings back memories.



I once worked for a company that made Turbochargers.
Old Jul 03, 2012, 02:59 PM
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i actually got an easier way to measure the thrust

compare the reading


calibration:
holding gauge upright. record the reading for motor&prop and motor&prop&shroud
Old Jul 03, 2012, 05:23 PM
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there is alot of engineering that goes into optimizing the duct. Here's some light reading...

http://www.personal.psu.edu/cxc11/pa...CTED_FAN_1.pdf

regarding blade tip clearance, once it exceeds 5.17%, the ducting becomes much less efficient. Inlet lip and diffusion duct geometry also have serious influences.
Old Jul 03, 2012, 05:28 PM
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Thanks Rob!
Old Jul 03, 2012, 07:50 PM
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If I may, here is an interesting video that maybe could genarate some ideas.

Honeywell T Hawk Described (2 min 53 sec)


It's the Honeywell Hawk uav, some of you guys may have allready seen it here it is anyway!
Old Jul 03, 2012, 08:01 PM
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this is the one in BF3.

http://www.thawkmav.com/system_features.php
spec from HW

gas engine

48min flight time
Old Jul 03, 2012, 08:06 PM
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Thank you David for sharing the video with us. Very interesting what I like the most is it all weather capability.

All Weather Day/Night Operation

Operates in rain, salt, fog, sand, and dust
Takes off and lands in winds up to 17 miles per hour
Old Jul 03, 2012, 08:38 PM
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i think that is due to it's gas engine... all the electronics are sealed in the case... which should be water proof
Old Jul 03, 2012, 08:57 PM
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The gas engine produces 4hp, something that can be acheived with the brushless motors that we use for our 700 class e-helis today... Would be nice to see something like that. I know it wouldn't be a multi anymore but the "general idea" is still there. Just need to get a control board that could be used to control the servos for the vector surfaces...
Old Jul 03, 2012, 09:12 PM
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Funny that you should mention control board, the WiiCopter just so happens to have a new addition. http://www.multiwii.com/forum/viewtopic.php?f=8&t=1882

keep in mind here, we are looking at the control system and not the aircraft itself.

MultiWii SingleCopter (0 min 29 sec)


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