JANSEN - KLANN LINKAGE COMPARISON

Here is a comparison between the Jansen Linkage and the Klann linkage. Both are similar in that they operate in a single plane, provide a constant axle height, use only pivot joints, a rotating crank for input, and can easily be scaled in size but there are significant differences.


Jansen Linkage - Klann Linkage Comparison
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Jansen Linkage Klann Linkage


8 links per leg
120 degrees of crank rotation per stride.
3 legs will replace a wheel.
Counterclockwise rotation of the crank.
6 links per leg
180 degrees of crank rotation per stride.
2 legs will replace a wheel.
Clockwise rotation of the crank.
Step height is primarily achieved by a parallel linkage in the leg that is folded during the cycle angling the lower portion of the leg. Step height is achieved by rotating the connecting arm which is attached to the crank on one end and the middle of the leg on the other. It pivots on a grounded rocker.
Jansen started in 1990 using computer models to develop a walking linkage. Klann started exploring various linkage synthesis methods in 1993 after being inspired in a kinematics class.
The eight-bar Jansen linkage evolved through iterations of a computer program. The six-bar Klann linkage is an expansion of the four-bar Burmester linkage developed in 1888 for harbor cranes.
Published “The Great Pretender”
BMW commercial featured Theo Jansen
http://en.wikipedia.org/wiki/Theo_Jansen
U.S. Provisional Application Ser. No. 60/074,425, filed on Feb. 11, 1998
US Patent 6,260,862 issued July 17, 2001
US Patent 6,364,040 issued April 2, 2002
US Patent 6,478,374 issued November 12, 2002
Theo Jansen
Kinetic Sculptor
www.strandbeest.com
Joe Klann
Mechanical engineer
www.mechanicalspider.com
Size and Tilt
The step height, stride length, ground clearance, over all size, and maximum incline, as well as the ratios of these factors, are obvious ways to compare the two linkages. Both linkages can be proportioned differently based on the inputs in the relationships. The center of gravity coincided with the center of the crank in the comparison of these linkages’ ability to handle an incline but could be significantly different depending on a wide range of factors.
Interactive displays of these two linkages are posted on www.mechanisms101.com
Jansen linkage Klann linkage

The proportions used in the animation for the Klann linkage are from a project from the summer of 2008. A few other configurations are posted on the Concept Page.



Klann Linkage in Phun

This is a fairly extreme example done in phun. The foot steps higher than the vehicle during each stride, it has decent ground clearance, and it does a respectable job of climbing provided there are foot holds. There are compromises in efficiency between step height and speed and on a relatively smooth surface the wheel wins every time.

Youtube link: Klann Linkage in Phun



Comments welcome email mechanicalspider

Ryan - 08MAY10 -
Ryan sent an updated drawing of Theo Jansen's dimensions. Jansen Linkage

Jon - 27MAR10 -
In reference to Ryan's email, 15 Oct 08. You'll notice with the Jansen linkage that the "power" part of the stride is slightly inclined. If you were to raise the crank a little, you are effectively rotating the whole system, thus leveling this incline.

Wil N. - 28JUL09 -
More info on Ryan's drawing.

To paraphrase the accompanying Dutch text (shortly and sweetly), the lengths for the leg segments were generated by a genetic algorithm. A little less short and sweet (and therefore truer to the source):

"In the computer 1500 legs were created with segments of random lengths. The computer examined which legs approached the ideal walking gait and selected the best 100. These got the privilege to reproduce themselves. Their segment lengths were recombined to create a new generation of 1500 legs, which showed resemblance with their parents and were again tested on against the ideal curve. This process ran day and night for many generations over the course of several months.

"Eventually thirteen numbers resulted, indicating the ideal lengths for each segment. The eventual result became the leg of the Animaris Currens Vulgaris, the first current Strandbeest. But Vulgaris strongly resists running from time to time. A new computer evolution provided the legs for the species which followed.

Here are the magic numbers: [and then the list of lengths, as seen in Ryan's diagram.]"

Larry G. - 26MAR09 -
I was reading your comparison, and saw Ryan's "clarification" drawing. I think Ryan may have misinterpreted the termination point of link "K" on his version of Theo's drawing.

Jansen shows it ending on the crank end, at the intersection of "J" and "M" (and his Strandbeests do it there).

Ryan shows "K" terminating on the intersection of "A" and "L", at the hub of the crank. If it were there, it wouldn't move.

W. Thielicke - 21MAR09 -
An email from William Thielicke pointed me to two Youtube videos. Both are nicely done.
Klann Linkage in Phun - Walking Robot
Comparison of Theo Jansen's mechanism and the Klann Linkage in Phun



Ryan - 21MAR09 -
Ryan made a drawing for people who can’t make out the numbers or letters in the initial drawing he sent. Jansen Linkage

Ryan - 15OCT08 -
I did some digging and found this diagram of Theo Jansen's mechanism in his own hand. It took all of my interweb delving ability to find, but thought you might be interested to see it. I attached it. One interesting thing is that the actual cranking point (you'll have to forgive my improper terminology--what I mean is the point that, if it were on a bicycle, would be called the bottom bracket) is not on mounted on a horizontal line with the other fixed point of the linkage, but is actually raised up a bit. In every iteration I've seen of the linkage, this has been wrong. I confirmed it by watching the videos I could find on Theo Jansen. I'm not quite sure how much it affects the linkage, but... yeah... thought you might be interested to see it. You can see it in the drawing (though poorly). By the drawing, the amount it is raised from the stationary horizontal line is "L=7.8" and the squashed crank is "M=15." To my knowledge I'm the only one who has caught this... This does make me wonder, though, because Theo talks about his "11 holy numbers" in some of the videos and there are 13 total... I'm not sure what this means, but anyway! Jansen's Dimensions


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