Back in the 90s I was very interested in Micro Aerial Vehicles (MAVs).
I researched hummingbirds and bumblebees in hover flight and discovered their wings flapped in a figure eight motion. This motion is similar to how you would move your arms and hands when trying to stay afloat in water.
So I researched all kinds of mechanisms and designs that could provide this motion and was surprised with the complexity of every system.
I decided to figure out my own mechanism and started running simulations using a kinematic dynamic software package called Mechanica Motion. NOTE: Mechanica is now ProEngineer which can be found at http://www.ptc.com/products/proengineer/mechanism-dynamics
For my first simulation i was thinking that a figure eight looks like two circles touching each other. Based on that i created a two gear system with two connecting rods. I arranged the gears to first provide a circle as they both spun at the same speed. I then thought if I spun one of the gears twice as fast as the other i should see two perfect lobes. Well i didn't. I got something close to a lopsided figure eight with one side having a convex shape. So i played with phasing of the gears and still no perfect figure eight. A colleague of mine happened to be visiting and asked me to spin the two gears at the same speed. I told her i already tried that and proceeded to show her. It was a truly eureka moment as the mechanism traced a really small figure 8! It was all in the phasing.
So after a few optimizations the perfect figure eight motion was accomplished with 4 basic parts, ie 2 counter rotating gears coupled with two connecting arms.
I was so excited, applied for a patent and two years later the US Patent & Trademark Office gave me the saddest news of my life. The mechanism had already been patented ( #2,775,899 ) in 1957 by C.L. Vagneur .
During the anxious two years i researched features like adding a second pair of connecting rods to flip the "wing" during the figure eight motion.
I looked at other applications like rowing & bike pedaling mechanisms, hair braiding, ceiling fans, wind energy device, etc . I researched the web on all things figure eight and found it was a common motion for polishing, cleaning and mixing.
Anyway, after discovering Instructables I thought it would be great to share all this info for anyone looking for that perfect figure eight motion drive!
Sabri Sansoy
The steps are more of slide presentation.
I researched hummingbirds and bumblebees in hover flight and discovered their wings flapped in a figure eight motion. This motion is similar to how you would move your arms and hands when trying to stay afloat in water.
So I researched all kinds of mechanisms and designs that could provide this motion and was surprised with the complexity of every system.
I decided to figure out my own mechanism and started running simulations using a kinematic dynamic software package called Mechanica Motion. NOTE: Mechanica is now ProEngineer which can be found at http://www.ptc.com/products/proengineer/mechanism-dynamics
For my first simulation i was thinking that a figure eight looks like two circles touching each other. Based on that i created a two gear system with two connecting rods. I arranged the gears to first provide a circle as they both spun at the same speed. I then thought if I spun one of the gears twice as fast as the other i should see two perfect lobes. Well i didn't. I got something close to a lopsided figure eight with one side having a convex shape. So i played with phasing of the gears and still no perfect figure eight. A colleague of mine happened to be visiting and asked me to spin the two gears at the same speed. I told her i already tried that and proceeded to show her. It was a truly eureka moment as the mechanism traced a really small figure 8! It was all in the phasing.
So after a few optimizations the perfect figure eight motion was accomplished with 4 basic parts, ie 2 counter rotating gears coupled with two connecting arms.
I was so excited, applied for a patent and two years later the US Patent & Trademark Office gave me the saddest news of my life. The mechanism had already been patented ( #2,775,899 ) in 1957 by C.L. Vagneur .
During the anxious two years i researched features like adding a second pair of connecting rods to flip the "wing" during the figure eight motion.
I looked at other applications like rowing & bike pedaling mechanisms, hair braiding, ceiling fans, wind energy device, etc . I researched the web on all things figure eight and found it was a common motion for polishing, cleaning and mixing.
Anyway, after discovering Instructables I thought it would be great to share all this info for anyone looking for that perfect figure eight motion drive!
Sabri Sansoy
The steps are more of slide presentation.
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Signing UpStep 1: Frame by Frame Trace
Frame by Frame analysis showing how the point where the two connecting rods are connected traces the figure 8. The two gears must counterrotate at the same speed.
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Basically, I exported the motion data out of Mechanica Motion and imported it into Lightwave.
There is a free animation package you can download today at http://www.blender.org/ .
It has inverse kinematics (IK) which should allow you to make the same mechanism and any of your own design.
More info about IK can be found at
http://wiki.blender.org/index.php/Manual/Inverse_Kinematics
Lift the rear portion up and off you go into the forward direction....maybe..its only in theory..lol. i do need to build a prototype.