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Old Jul 07, 2012, 08:46 PM
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Variable Wiggle Drive.

After reading a lot on this forum about wing construction, wing movement and articulation – All of it very interesting reading, I thought I might add my contribution. Myself being from an engineering background, I loved the ‘alternative’ method of creating linier motion from a rotating shaft that was presented by the wiggle drive. After a few prototypes I have thought to maybe improve it by the addition of variable throw.

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Description: The finished assembly. Name: IMG_4779.jpg
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Description: Finished assembly showing tethering arm.

My design shown here (in its basic form), although more complex can still be machined simply using a home lathe and a simple pillar drill.

I have taken the standard wiggle drive as presented in various threads and produced a prototype Variable Wiggle Drive (VWD), which allows the user to alter the wing flapping range from zero to maximum independent of any flapping speed. My thought being that by using differing wing flapping amplitude coupled with leading / trailing wing movement (also a bye product of the wiggle drive system) and an elevator (tail) an ornithopter could be steered in flight. Electronic mixing would also make things simpler.

The VWD parts…

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Description: Variable Wiggle Cap.

The Variable Wiggle Cap – This part holds the two wing spars and is the top most part of the assembly. It sits on a 23x19x4 miniature bearing readily available on Ebay (mine were removed from a scrap swash plate assembly taken from a Esky Blade Helicopter). This cap is held down by a flanged 4x9x4 ball bearing also taken from my spares box. These two bearings firmly locate the Wiggle Cap in position and allow freedom of rotation. The two wing spar holes are designed to hold 3/16” tube (brass, aluminium or Stainless Steel with an inner diameter of 3 mm) – just right for 3mm carbon rods. These tubes are locked in place with 3mm grub screws for ease of replacement. At the rear of the Wiggle Cap is a M2 tapped hole for fitment of a Ball link, again taken from the scrap swash plate to anchor it.

It should be mentioned that in my first prototype the two wing spar holes are drilled parallel to the Wiggle Cap base which gives wing movement equally about the horizontal plane. I have also made a set of Wiggle Caps with these holes at +15’ which results in wing movement centred about that reference. (i.e. 20’ wing movement would be 35’ up (15+20) and 5’ down (15-20) about the horizontal plane.

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Description: Variable Wiggle Base. Name: IMG_4775.jpg
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Description: VWB partly assembled.

The Variable Wiggle Base – This is the main support of the Variable Wiggle Drive, from below it is driven via a universal joint on the end of 5mm shaft courtesy of a 4x4 TRAXXS or Associated off road machine, and pivots on two 3x8x4 ball bearings (again my spares box) thus allowing it to tilt in only one plane. When the larger ball race is fitted the two smaller bearings are locked in position. A CSK 4mm screw is fitted from underneath (Loctited in position.) and when the cap is placed on top and sat on the radial bearing it is securely held in place by a 4mm Nyloc. This forms the basis of the Variable Wiggle Drive.

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Description: THe main shaft. Name: IMG_4780.jpg
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Description: Rod showing removal of pin. Name: IMG_4781.jpg
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Description: Rod with new (Removal pin) and bearings - trial fit.

Pictures show the rod as received, the pin is then removed with a pin punch and a new 3mm x 18mm pin made (slide fit) and trial assembly with the two 3x8x4 bearings.

Under the base I have used a tail pitch assembly taken from a Gaui X5 helicopter (pt # 213654), which is free to slide up and down the drive shaft, but as it is connected to the base assembly by the little connecting arm, so it alters the angle of the Base and hence the wiggle cap and the wing spars.

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Description: Variable Wiggle FIx.

The third part which I unimaginatively call the Variable Wiggle Fix - I designed as a multipurpose part. It can be used to create (with the other two parts) a simple fixed wiggle drive (i.e. not variable angle), by replacing the tail pitch assembly and holding the Wiggle Drive Base at a fixed angle via the connecting arm. When you have set the required angle it is held in place on the drive shaft by grub screws. Or it can simply be used to hold the gears that are need to keep the pair of Variable Wiggle Drives in synch etc.

Planned Implementation.

With a pair of VWD’s it should be possible to have the following control of a pair of wings:-

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Description: VWB fitted to shaft showing zero wing flaping position. Name: IMG_4778.jpg
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Description: VWB fitted to shaft showing maximum wing flapping position.

• Independent flap range (regardless of flapping rate) of either wing. (Flap angle is centred about a point determined by the hole angle in Wiggle Cap during manufacture.)

• Variable lead / lag of wings by adjustment of the wiggle cap angle. (Using just a single servo would give control of both wings, advancing one whilst retarding the other & maybe not altering the C of G.?)

• Flap rate by motor speed control.
Because of the weight penalty imposed by a pair of VWD’s, four servos etc the test bed for this drive system needs to be mid size and currently I am thinking 60” wing span (Slow Yard Hawk Size) or 50% bigger than the kestrel / Park Hawk.

As you can see, one of the VWD's is complete the other i will assemble this week and hopfully have a working test assembly within a week or two...

If anybody is interested DXF drawings of the parts have been made and i will gladly share them..
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Old Jul 07, 2012, 09:45 PM
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thanks for sharing
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Old Jul 08, 2012, 05:30 AM
Kjell Dahlberg
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Mallorca Spain
Joined Nov 2005
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Hi Snetzka.
You can understand my interest in your new application of the Wiggle Drive. It looks clever.
I am interested to study your DXF drawings.
I am interested to see how you are connecting the VWD to move the wings.
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Last edited by KJELL; Jul 08, 2012 at 11:59 AM.
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Old Jul 08, 2012, 02:46 PM
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Joined Jun 2010
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Of course, please find attached for anybody interested archive files containing 3D pictures & DXF files for the three main parts. The DXF files have been used to manufacture the items, so i know they are correct.

Wiggle top-2

Wiggle Fix

wiggle cap

Wing attachment..

I designed the VWD Cap with two parrallel holes (4.77mm) machined in it, 26mm apart. These hold 3/16" Brass (or aluminium)Tubes (50mm long) with an inside diameter of 3mm in which 3mm Carbon rods (wing spars) are glued. The brass (or aluminium) tubes are held in place by 3mm grub screws insertred into the side tapped holes of the VWD cap.

This was designed to hold the rod securly, yet removeable without damage to the carbon rods & provide support to the rod at the drive end.

I hope this helps clarify my intentions, i am more than happy to explain the background to my thinking, share my thoughts and of course listen to ideas....

Mike...
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Old Jul 08, 2012, 10:14 PM
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To further explain my thoughts / direction here are two further drawings, one is a Kjell drawing (My insperation..!!!) i modified to try to explain my thoughts on wing forward / backward motion via a single servo, giving the same (i hope) CofG but shift of weight to side wards (much like alerons on a normal plane).

And an assembly drawing showing two VWD's in position linked by two gears to ensure sync, and provide drive in the correct direction, my drive motor will be via a belt / pulley to one shaft. each one has a servo to control the wing flap amplitude ( from zero to maximum).

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Description: Name: vwd-outline.png
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Description:

Also the arrangment should allow for control of the wing dihedral during soaring / 'power motor off' phase.
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Last edited by Snetzka; Jul 08, 2012 at 10:31 PM. Reason: Forgot..
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Old Jul 09, 2012, 01:22 AM
Kjell Dahlberg
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Mallorca Spain
Joined Nov 2005
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Thanks for your informtion. I understand why you make it posible to alter the wiggle angle. The price is more weight and more complicated construction. There is one poit I don’t like. You have altered the most important part. The Wiggle-Mid-point.
This is my design of my Wiggle-Drive for bigger Ornithopters.
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Old Jul 09, 2012, 02:55 PM
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Thanks for the drawing (wish i had the skill or package to produce such master peices - mine are hand drawn) - anyway.. Yes, i did consider the worm gear reduction, (high reduction in a small space) but running one directly form a brushless motor, and the high speeds obtained with them you will need a high grade wormgear assy (or even a pre-reduction system), i even have a set up using a single motor / wormgear driving both gears on my bench for trial. But in the end i opted for a normal gear reduction for reasons of weight.

As for two motors..... how would you plan to acheive wing flap sync..? The only way i can think of is by using a positional encoder and some smarts... (Electronices) = weight & complexity... Not out of my realm or reach, but do we need wings out of sync...???? and again weight penalty.

The only other difference i see is the use of an servo (?) for each wing for horizonal wing movement, i did consider that, but in an effort to save weight i thought along these lines... 'If i want one wing further forward than the other, then i could move one forwards and at the same time move one back all with one servo.' But with my testbed it can be tried..

Note these are questions / not Criticisms - i am eger to learn, why, how etc..... I am keen to implement / deisgn / experiment but theory needs to be real-world so i also to see the fruits in action / flight and share our findings to move forwards.

I agree my implementation is more complex than your 'bent' shaft aproach, but the advantage (as i see it) of variable flap is worth it. I have already considered weight (it was one of my major concerns from the begining) and am currently trying to par down the drive weight by 50% which is no mean feat.

My other concern is torque reaction from the wings, flapping such big wings is going to put a lot of stress in the last horizontal bearing. In your design it's just below the joggle in the shaft, in mine it's the bearing just below the pitch assembly. Do you see signs of such pressure / issues in your implementations..?
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Old Jul 09, 2012, 03:09 PM
Kjell Dahlberg
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Joined Nov 2005
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I have been studding your DXF drawings. I like very much your variable Fan-Flapping control. I have made some prototypes before, but I can see that yours is better. I have now been working with your idea and it is possible to make it lighter and the important is that it can be mounted with the Wiggle center point in the proper position. I would like to get in contact with you by E-mail. kjellgood@gmail.com I like to show you my drawings before showing them in the forum.
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Old Jul 09, 2012, 10:17 PM
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i wish both of you success the idea sound great regards Brian
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Old Jul 09, 2012, 11:27 PM
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Quote:
Originally Posted by Snetzka View Post
Thanks for the drawing (wish i had the skill or package to produce such master peices - mine are hand drawn) - anyway.. Yes, i did consider the worm gear reduction, (high reduction in a small space) but running one directly form a brushless motor, and the high speeds obtained with them you will need a high grade wormgear assy (or even a pre-reduction system), i even have a set up using a single motor / wormgear driving both gears on my bench for trial. But in the end i opted for a normal gear reduction for reasons of weight.

As for two motors..... how would you plan to acheive wing flap sync..? The only way i can think of is by using a positional encoder and some smarts... (Electronices) = weight & complexity... Not out of my realm or reach, but do we need wings out of sync...???? and again weight penalty.

The only other difference i see is the use of an servo (?) for each wing for horizonal wing movement, i did consider that, but in an effort to save weight i thought along these lines... 'If i want one wing further forward than the other, then i could move one forwards and at the same time move one back all with one servo.' But with my testbed it can be tried..

Note these are questions / not Criticisms - i am eger to learn, why, how etc..... I am keen to implement / deisgn / experiment but theory needs to be real-world so i also to see the fruits in action / flight and share our findings to move forwards.

I agree my implementation is more complex than your 'bent' shaft aproach, but the advantage (as i see it) of variable flap is worth it. I have already considered weight (it was one of my major concerns from the begining) and am currently trying to par down the drive weight by 50% which is no mean feat.

My other concern is torque reaction from the wings, flapping such big wings is going to put a lot of stress in the last horizontal bearing. In your design it's just below the joggle in the shaft, in mine it's the bearing just below the pitch assembly. Do you see signs of such pressure / issues in your implementations..?
cant wait to see the trail setup but all in time no rush cheers Brian
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Old Jul 12, 2012, 02:16 PM
Kjell Dahlberg
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Variable Wiggle Drive.

Thanks to Mike´s clever idea, it now possible to make the Variable Wiggle Drive. The Fan-Flapping angle can be altered between 0º to 50º while flying.
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Old Jul 13, 2012, 07:58 AM
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very smart idea MIke regards Brian cant wait to see it in action
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Old Jul 13, 2012, 08:30 PM
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yea, managed to make it more simple, less height and weight, so next i'll put into drawing format and churn out prototype number 2....
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Old Jul 14, 2012, 08:12 AM
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sounds really good mike and what you plan to do i think with some fine tuning it will work well i wish you the greatest of success keep us informed
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Old Jul 14, 2012, 03:47 PM
Kjell Dahlberg
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The next Wiggle – drive for human controlled Ornithopter.
Hoping we soon see Mike’s VWD prototype.
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