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Camera vibrations
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#12
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Camera vibrations
James wrote:
I bought a Mobius miniature camera to fit to my handlebars. https://www.mobius-actioncam.com/ Image quality is great. It's small and light. Didn't cost a bundle. I've read about vibration damping and so on, as I see when I go over bumpy road I get the jello effect through the video. I came across another bicycle vibration analysis study today http://mecano.gme.usherb.ca/~jmdrouet/velus/assets/0707cham.pdf and one part caught my eye. Frequency 27.8Hz Front-to-back motion of fork. This got me to thinking. The jello effect is a rippling through the picture at a few Hz. Could this be a beat frequency between the shutter speed (30Hz), and the front wheel moving back and forth as it rides over bumps? Further to this, if the camera simply moved up and down a small amount, but continued to aim approximately in the same direction, I don't think there would be such a big effect on the video. I think to cause the jello effect the camera is being aimed slightly higher and lower than the average position, at near 30Hz. That is the camera has changing pitch, not just raised and lowered. So I wonder how much bending is transferred through the fork steerer, on to the head stem and through to the bars? My next test will be to (temporarily) mount the camera in the middle of the head tube. There may be some pitch change as the front wheel rides over a bump and a little later the back wheel follows, but I wouldn't have thought the bike would pitch at 30Hz. Thoughts? It is a build in feature to make it all look more dramatic :-). I have a Garmin Virb to make little clips from club rides, mostly off road. The camera has some kind of anti vibration mode but I see little difference with or without. Still I am impressed with the image quality despite the bumpy rides on a unsuspended crossbike off road. -- Lou |
#13
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Camera vibrations
On 12/7/2015 3:17 PM, James wrote:
On 08/12/15 02:29, Frank Krygowski wrote: On 12/7/2015 12:56 AM, James wrote: I bought a Mobius miniature camera to fit to my handlebars. https://www.mobius-actioncam.com/ Image quality is great. It's small and light. Didn't cost a bundle. I've read about vibration damping and so on, as I see when I go over bumpy road I get the jello effect through the video. I came across another bicycle vibration analysis study today http://mecano.gme.usherb.ca/~jmdrouet/velus/assets/0707cham.pdf and one part caught my eye. Frequency 27.8Hz Front-to-back motion of fork. This got me to thinking. The jello effect is a rippling through the picture at a few Hz. Could this be a beat frequency between the shutter speed (30Hz), and the front wheel moving back and forth as it rides over bumps? Further to this, if the camera simply moved up and down a small amount, but continued to aim approximately in the same direction, I don't think there would be such a big effect on the video. I think to cause the jello effect the camera is being aimed slightly higher and lower than the average position, at near 30Hz. That is the camera has changing pitch, not just raised and lowered. So I wonder how much bending is transferred through the fork steerer, on to the head stem and through to the bars? My next test will be to (temporarily) mount the camera in the middle of the head tube. There may be some pitch change as the front wheel rides over a bump and a little later the back wheel follows, but I wouldn't have thought the bike would pitch at 30Hz. Thoughts? Interesting. I hadn't heard of the Jello Effect. I guess this is a good example: https://vimeo.com/69906288 The beat frequency idea seems possible to me. If the effect is dependent on changes in pitch, I wonder if it could be prevented by a parallelogram linkage like this: http://www.atticpaper.com/prodimages...banner1897.jpg Its intent is to provide vibration isolation without pitch change. Hmm.. I can understand how the parallelogram may act as a vertical motion suspension arm, but I do not see how it aims the lamp straight while the handlebars pitch (rotate to aim higher and lower). Ah. OK, I see what you're saying. If the flex of the stem and bars is the real culprit, it might be better to mount the camera elsewhere on the bike - say, to the head tube. Nothing is rigid, of course, but I'd expect very little vibration-induced pitching motion there - just lots of vibration, which you'll have anywhere. Perhaps the parallelogram would do the job in that location. If you must have a handlebar mount and the handlebars and/or stem are changing the pitch, you might have a chance with a modified not-quite-parallelogram configuration. That parallelogram is what we MEs call a four bar linkage, with (in this case) the rear or fixed base being one bar. If the front vertical bar is shorter than the base bar, then a downward motion would tend to tilt the camera upward. I suppose it might be possible to choose the spring constant, mass, and dimensions so the linkage compensates for the bar's downward tilt. Sounds tricky, though. -- - Frank Krygowski |
#14
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Camera vibrations
On Tue, 8 Dec 2015 06:07:33 +1000, James
wrote: On 07/12/15 21:01, John B. wrote: On Mon, 7 Dec 2015 15:56:14 +1000, James wrote: I bought a Mobius miniature camera to fit to my handlebars. https://www.mobius-actioncam.com/ Image quality is great. It's small and light. Didn't cost a bundle. I've read about vibration damping and so on, as I see when I go over bumpy road I get the jello effect through the video. I came across another bicycle vibration analysis study today http://mecano.gme.usherb.ca/~jmdrouet/velus/assets/0707cham.pdf and one part caught my eye. Frequency 27.8Hz Front-to-back motion of fork. This got me to thinking. The jello effect is a rippling through the picture at a few Hz. Could this be a beat frequency between the shutter speed (30Hz), and the front wheel moving back and forth as it rides over bumps? Further to this, if the camera simply moved up and down a small amount, but continued to aim approximately in the same direction, I don't think there would be such a big effect on the video. I think to cause the jello effect the camera is being aimed slightly higher and lower than the average position, at near 30Hz. That is the camera has changing pitch, not just raised and lowered. So I wonder how much bending is transferred through the fork steerer, on to the head stem and through to the bars? My next test will be to (temporarily) mount the camera in the middle of the head tube. There may be some pitch change as the front wheel rides over a bump and a little later the back wheel follows, but I wouldn't have thought the bike would pitch at 30Hz. Thoughts? From your description and some photography that I've done I suspect that the camera is moving, however little. That part is obvious. The question is whether it is simple up and down movement, or changing pitch, which is worse and how to reduce. My experience, with film cameras, is that they sometimes can be isolated from the vehicle to eliminate high frequency vibration but not actual movement, or perhaps I should use the term "gross movement" as vibration is, effectively, movement. I would wonder what would happen if you mounted the camera on your helmet (or hat :-)? Helmet, shoulder or chest mount apparently works, however the first is possibly illegal in Australia as it may affect the helmet crash worthiness - low as it is - and I don't care to wear a camera at all. It has to be bike mounted AFAIAC. If a mounting other then solidly on the bike seems to solve part or all of the problem then you have eliminated what you call "vibration", actually high speed and low amplitude movement. The next step would be to build/buy some sort of mount that has the properties of damping vibration. See below for examples: http://www.helipal.com/lp-0064-jello...ount-base.html http://flitetest.com/articles/_Vibra...e_Camera_Mount http://petapixel.com/2014/07/29/buil...rone-mount-10/ -- cheers, John B. |
#15
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Camera vibrations
On 08/12/15 10:27, John B. wrote:
On Tue, 8 Dec 2015 06:07:33 +1000, James wrote: On 07/12/15 21:01, John B. wrote: On Mon, 7 Dec 2015 15:56:14 +1000, James wrote: I bought a Mobius miniature camera to fit to my handlebars. https://www.mobius-actioncam.com/ Image quality is great. It's small and light. Didn't cost a bundle. I've read about vibration damping and so on, as I see when I go over bumpy road I get the jello effect through the video. I came across another bicycle vibration analysis study today http://mecano.gme.usherb.ca/~jmdrouet/velus/assets/0707cham.pdf and one part caught my eye. Frequency 27.8Hz Front-to-back motion of fork. This got me to thinking. The jello effect is a rippling through the picture at a few Hz. Could this be a beat frequency between the shutter speed (30Hz), and the front wheel moving back and forth as it rides over bumps? Further to this, if the camera simply moved up and down a small amount, but continued to aim approximately in the same direction, I don't think there would be such a big effect on the video. I think to cause the jello effect the camera is being aimed slightly higher and lower than the average position, at near 30Hz. That is the camera has changing pitch, not just raised and lowered. So I wonder how much bending is transferred through the fork steerer, on to the head stem and through to the bars? My next test will be to (temporarily) mount the camera in the middle of the head tube. There may be some pitch change as the front wheel rides over a bump and a little later the back wheel follows, but I wouldn't have thought the bike would pitch at 30Hz. Thoughts? From your description and some photography that I've done I suspect that the camera is moving, however little. That part is obvious. The question is whether it is simple up and down movement, or changing pitch, which is worse and how to reduce. My experience, with film cameras, is that they sometimes can be isolated from the vehicle to eliminate high frequency vibration but not actual movement, or perhaps I should use the term "gross movement" as vibration is, effectively, movement. I would wonder what would happen if you mounted the camera on your helmet (or hat :-)? Helmet, shoulder or chest mount apparently works, however the first is possibly illegal in Australia as it may affect the helmet crash worthiness - low as it is - and I don't care to wear a camera at all. It has to be bike mounted AFAIAC. If a mounting other then solidly on the bike seems to solve part or all of the problem then you have eliminated what you call "vibration", actually high speed and low amplitude movement. The next step would be to build/buy some sort of mount that has the properties of damping vibration. See below for examples: http://www.helipal.com/lp-0064-jello...ount-base.html http://flitetest.com/articles/_Vibra...e_Camera_Mount http://petapixel.com/2014/07/29/buil...rone-mount-10/ Yep. I have looked at such things. I made something similar using an aluminium sheet, some foam and a strip inner tube. My camera mount has slots that I can feed the inner tube strip through, and this holds the camera down on a couple of pieces of foam that sit between the camera and the aluminium plate, that is cable tied to the supplied handlebar mount platform. It certainly reduces some vibration, but all these ideas are for a quad-copter or similar, that probably has vibration amplitudes far lower than a bicycle handlebar being ridden over rough chip seal. My current thought is to produce an arm about 50-75mm long to mount the camera on, and pivot the arm using an elastomer bush (maybe silicon rubber) from a rigid handlebar clamp. The difficulty will be to get a low enough spring constant and high enough damping so that the natural frequency of the mass/arm/elastomer bush is around 10Hz or lower I guess, and over damped. I'm not keen on attaching it to the head tube if I can help it, but that might be the next step. -- JS |
#16
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Camera vibrations
minimalist device. Instaled an Audio vox forwardview vehicle loop recoder, same price similar size. The van does not vibrate with acceleration/distance/frequency of a chip sealed bicycle.
See: iso vibration utube: Mobius software Google Images has charts for: iso vibration Within the cost design package seems no way the Mobius would image on a chip seal bicycle frame. only a Mobius forum or Mobius hisself could focus the application |
#17
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Camera vibrations
rOn Tue, 8 Dec 2015 12:16:35 +1000, James
wrote: On 08/12/15 10:27, John B. wrote: On Tue, 8 Dec 2015 06:07:33 +1000, James wrote: On 07/12/15 21:01, John B. wrote: On Mon, 7 Dec 2015 15:56:14 +1000, James wrote: I bought a Mobius miniature camera to fit to my handlebars. https://www.mobius-actioncam.com/ Image quality is great. It's small and light. Didn't cost a bundle. I've read about vibration damping and so on, as I see when I go over bumpy road I get the jello effect through the video. I came across another bicycle vibration analysis study today http://mecano.gme.usherb.ca/~jmdrouet/velus/assets/0707cham.pdf and one part caught my eye. Frequency 27.8Hz Front-to-back motion of fork. This got me to thinking. The jello effect is a rippling through the picture at a few Hz. Could this be a beat frequency between the shutter speed (30Hz), and the front wheel moving back and forth as it rides over bumps? Further to this, if the camera simply moved up and down a small amount, but continued to aim approximately in the same direction, I don't think there would be such a big effect on the video. I think to cause the jello effect the camera is being aimed slightly higher and lower than the average position, at near 30Hz. That is the camera has changing pitch, not just raised and lowered. So I wonder how much bending is transferred through the fork steerer, on to the head stem and through to the bars? My next test will be to (temporarily) mount the camera in the middle of the head tube. There may be some pitch change as the front wheel rides over a bump and a little later the back wheel follows, but I wouldn't have thought the bike would pitch at 30Hz. Thoughts? From your description and some photography that I've done I suspect that the camera is moving, however little. That part is obvious. The question is whether it is simple up and down movement, or changing pitch, which is worse and how to reduce. My experience, with film cameras, is that they sometimes can be isolated from the vehicle to eliminate high frequency vibration but not actual movement, or perhaps I should use the term "gross movement" as vibration is, effectively, movement. I would wonder what would happen if you mounted the camera on your helmet (or hat :-)? Helmet, shoulder or chest mount apparently works, however the first is possibly illegal in Australia as it may affect the helmet crash worthiness - low as it is - and I don't care to wear a camera at all. It has to be bike mounted AFAIAC. If a mounting other then solidly on the bike seems to solve part or all of the problem then you have eliminated what you call "vibration", actually high speed and low amplitude movement. The next step would be to build/buy some sort of mount that has the properties of damping vibration. See below for examples: http://www.helipal.com/lp-0064-jello...ount-base.html http://flitetest.com/articles/_Vibra...e_Camera_Mount http://petapixel.com/2014/07/29/buil...rone-mount-10/ Yep. I have looked at such things. I made something similar using an aluminium sheet, some foam and a strip inner tube. My camera mount has slots that I can feed the inner tube strip through, and this holds the camera down on a couple of pieces of foam that sit between the camera and the aluminium plate, that is cable tied to the supplied handlebar mount platform. It certainly reduces some vibration, but all these ideas are for a quad-copter or similar, that probably has vibration amplitudes far lower than a bicycle handlebar being ridden over rough chip seal. My current thought is to produce an arm about 50-75mm long to mount the camera on, and pivot the arm using an elastomer bush (maybe silicon rubber) from a rigid handlebar clamp. The difficulty will be to get a low enough spring constant and high enough damping so that the natural frequency of the mass/arm/elastomer bush is around 10Hz or lower I guess, and over damped. I'm not keen on attaching it to the head tube if I can help it, but that might be the next step. The basic idea - an arm with an elastic pivot is certainly sound but I think that you are going to have problems with both frequency dampening and gross movement, the "buzz" from smooth pavement versus hitting the big bump. Probably some large, low pressure, say 4 inch, tires would help a lot :-) -- cheers, John B. |
#18
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Camera vibrations
It certainly reduces some vibration, but all these ideas are for a quad-copter or similar, that probably has vibration amplitudes far lower than a bicycle handlebar being ridden over rough chip seal. Mount the camera on a quad-copter. http://reviews.mtbr.com/news-silca-l...-support-drone |
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