does anyone know how does the central lock mechanism in articulated arm (magic arm) works?
The magic arm usually used to hold camera, with only 1 knob, it can lock all sides. How?
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$\begingroup$ Is the assertion that the end joints are not locked correct? $\endgroup$– martCommented Dec 8, 2016 at 6:56
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1$\begingroup$ both links and end ball joints are fixed in position with the central locking knob... and i wonder how.... $\endgroup$– Travis TCommented Dec 12, 2016 at 2:54
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2 Answers
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Locking the ball joints: Rotating the handle also rotates two cylinders with a section cut out. (see photo)
When rotated to a locked position, each cylinder pushes on a rod in each arm, applying force to the ball joint, holding the ball joints in place by friction.
When unlocked, each rod slides into the cut out in the cylinder, releasing the force on the ball joint.
Locking the central pivot joint: Rotating the handle presses the two halves of the arm together, locking two rings of teeth together (pictured below). I am unsure of the exact mechanism to convert the rotational force from the handle into force pressing the halves together.
This model may work differently from the one pictured in the question.
Images used: Spare part pdf under the downloads tab on this Manfrotto product page https://www.manfrotto.us/magic-arm-kit-143a-003-035
Product comparison image from this product listing page. I have not idea if this is a reputable website or not, I just found my image there. dx.com/p/aputure-a10-multifunctional-magic-arm-stabilizer-grip-for-camera-black-387217#.WHGSchsrLb1
I can't post more than 2 links yet, so you may need to add three "w" and a period before the third link to get it to work.
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$\begingroup$ I was looking for the same thing, but couldn't find the correct terminology to use in a SE search, and wrote up mostly a duplicate question asking the same thing, answered it at engineering.stackexchange.com/a/31793/14357 . In the original question there, I have added a ton of links showing different terminology for this mechanism. Combine the video I linked in that answer, with your extremely helpful drawing, should be helpful in "debugging" the mechanism or coming up with lower cost DIY alternatives. $\endgroup$– bgoodrCommented Nov 4, 2019 at 14:53
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I haven't used any, but from the image, it's clear that there are only two linked bars, so if the knob simply restricts the pin joint at the common vertex, the two links will be locked with respect to each other. The end points are ball joints and they won't be locked.
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$\begingroup$ Ya, the two links are locked with the knob. But, at the same time, the end ball joints do fixed as well and i wonder how.... bhphotovideo.com/c/product/325440-REG/… $\endgroup$– Travis TCommented Dec 12, 2016 at 2:44
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$\begingroup$ The ball joints have slots made to restrict movement (static.bhphoto.com/images/multiple_images/images750x750/…) .. maybe this is why they get fixed in one position? $\endgroup$ Commented Dec 12, 2016 at 3:08
