Hopefully pic is attached. The manner of operation should be obvious enough. The larger spring is to return the mechanism to the cocked position... the valve on the opposite side has a simple needle valve that controls the speed of return. The smaller spring and little arm on the right decelerates the system after the stroke. Because this piece is designed for floppy implements, the stroke itself can provide little or no deceleration, and an overrun causes tooth skips on the drive sprocket. That would be easily fixed using a guard instead.
If money isn't an issue, you can replace all of this setup by using a good sized rotary actuator. Fast acting proportional valves would allow very precise control of both stroke and return. I would take this approach if tasked with cracking a whip.
Also note that you cannot throw in a circular arc if you want to crack. You have to throw in a long oval... nearly straight out from the machine. My approach would be a jointed arm that straightens over the course of a stroke, using a length of aircraft cable over a cam that creates the required relative acceleration of the second arm as the first arm advances. I think you would need something else -- perhaps even a third segment of arm acting independently -- to create the withdraw that will allow a loop of the whip to crack.
Bullwhip Machine
Re: Bullwhip Machine
Thanks for the pic!
I agree that a somewhat straight line motion is needed to crack a bullwhip, that is how I crack mine. I was thinking of using a Lambda Mechanism
https://en.wikipedia.org/wiki/Chebyshev ... _Mechanism
to do this, since it gives straight line motion without using a track and also it automatically handles deceleration at the end of the stroke. It can also pull back at the end of the stroke if I run it a little bit farther. It also lends itself to the use of a torsion spring, so that the spring itself does not have to move rapidly, wasting kinetic energy. (Only the potential energy of the spring can be used. The kinetic energy of the moving spring is not used, so represents a loss in the system). The downside is I would have to make it of aluminum alloy, and it would have to be fairly light and hence fragile. Also a little expensive to machine from scratch.
The other possible approach would be to use a V belt over two pulleys, powered by an elastic band off of a spear gun. The V belt would only do half of a turn, and the lash would be tied onto the top of it. It is another way to get straight line motion without using a track, plus everything is "soft" for handling sudden deceleration. It also moves the front end of the lash downwards and out of the way of the rest of the lash (as the front end goes a short distance downwards over the pulley at the end of the stroke), to encourage the formation of the wave that must be formed to crack the whip. The V belt would be lighter than an aluminum structure and far more robust, an attractive feature. Also easy to replace and available off the shelf.
On Mythbusters they clocked the cracker of a bullwhip at 1200 feet per second, which his around Mach 1.1. There are also some slow motion videos of cracking bullwhips on YouTube, somebody even did Schlieren photography of the cracker generating supersonic shock waves.
https://www.youtube.com/watch?v=lbomsOPSSII
If I get one of these working and ship it off to Slovakia, might you be interested in using it? No cash would change hands, I would just trade hardware for videos.
I agree that a somewhat straight line motion is needed to crack a bullwhip, that is how I crack mine. I was thinking of using a Lambda Mechanism
https://en.wikipedia.org/wiki/Chebyshev ... _Mechanism
to do this, since it gives straight line motion without using a track and also it automatically handles deceleration at the end of the stroke. It can also pull back at the end of the stroke if I run it a little bit farther. It also lends itself to the use of a torsion spring, so that the spring itself does not have to move rapidly, wasting kinetic energy. (Only the potential energy of the spring can be used. The kinetic energy of the moving spring is not used, so represents a loss in the system). The downside is I would have to make it of aluminum alloy, and it would have to be fairly light and hence fragile. Also a little expensive to machine from scratch.
The other possible approach would be to use a V belt over two pulleys, powered by an elastic band off of a spear gun. The V belt would only do half of a turn, and the lash would be tied onto the top of it. It is another way to get straight line motion without using a track, plus everything is "soft" for handling sudden deceleration. It also moves the front end of the lash downwards and out of the way of the rest of the lash (as the front end goes a short distance downwards over the pulley at the end of the stroke), to encourage the formation of the wave that must be formed to crack the whip. The V belt would be lighter than an aluminum structure and far more robust, an attractive feature. Also easy to replace and available off the shelf.
On Mythbusters they clocked the cracker of a bullwhip at 1200 feet per second, which his around Mach 1.1. There are also some slow motion videos of cracking bullwhips on YouTube, somebody even did Schlieren photography of the cracker generating supersonic shock waves.
https://www.youtube.com/watch?v=lbomsOPSSII
If I get one of these working and ship it off to Slovakia, might you be interested in using it? No cash would change hands, I would just trade hardware for videos.
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OrgasmAlley
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Re: Bullwhip Machine
Something along those lines, for sure, although you would throw out using the arced side of travel so the whip doesn't get it it's own way. Note that it is the draw-back, coupled with the narrowing whip belly, that accelerates the thing forward beyond the limit of travel. The transition in direction needs to be smooth but very swift.
