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Old April 17th, 2006, 07:52 PM   #16
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My suggestion would be to glue the GG unto the face of a 55mm Wheel Bearing with a large inner bore, the largest you'll find is about 40mm inner diameter. Slide the wheel bearing inside the tube and spin it by a rubber wheel attached to a small battery powered motor. The rubber wheel would rotate the inner bearing from the opposite side to about 12,000 rpms. I'm in the process of working on this idea as we speak, waiting for my wheel bearing to come in. Has anybody considered working on this type of spnning the GG?
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Old April 18th, 2006, 02:37 AM   #17
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Yes,
Nick Bartleet ( http://www.pixelloft.com/ ) designed this method over a year ago and has been using it ever since on his adapter.

http://www.sysmicfilms.com/wayne/PB050176.JPG

Only thing that bugs me, is that in theory the dead centre of the GG does not spin, and the spinning gets slower towards the centre of GG. You need very fine grit GG for this method to work.
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Old April 18th, 2006, 03:15 AM   #18
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What about GG artifacts near axis of rotation?
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Old April 18th, 2006, 03:40 AM   #19
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Frank,
Yes this is what I was trying to explain. You need a very fine GG. Nick works with the FX-1 in HD, had his work is on MTV alot, no problems.
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Old April 18th, 2006, 05:19 AM   #20
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Quote:
Originally Posted by Wayne Kinney
Only thing that bugs me, is that in theory the dead centre of the GG does not spin, and the spinning gets slower towards the centre of GG. You need very fine grit GG for this method to work.
Yes, i'm sorry i missed that. btw how micro35 is designed. How far is rotating axis from viewable area.
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Old April 18th, 2006, 06:55 AM   #21
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Cant speak for the m2, but the SGpro's rotational axis is around 28.7mm from the centre of the frame. I think this is getting off topic.
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Old April 18th, 2006, 09:25 AM   #22
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Exactly what I was referring too! The only thing is that my adapter will have the tiny motor inside the tube with a rubber wheel wheel that will spin the inner wheel of the bearing. It will eliminate extra metal parts and thereby weight. I found a bearing that will fit inside the tube and the inner diameter is 40mm, giving me more focus plane unto the GG. I am considering using the motor of a CPU fan for the project. Tnanks for the image.
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Old April 18th, 2006, 09:51 AM   #23
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isn't 40mm too small for a 36x24mm image, or are you aiming for 18x24?
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Old April 18th, 2006, 10:25 AM   #24
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Wayne,

The largest inner bore diameter wheel bearing that I found is about 40mm, and outer diameter that will be 55mm that I needed. Unless somebody can point me in the right direction where I could find a much bigger inner bore that will accommodate either a 55mm or 58mm outer diameter tube.
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Old April 19th, 2006, 01:53 AM   #25
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If you are still going this route, perhaps forget about the wheel bearing and examine the bearing which carries the pulley/clutch assembly on automotive airconditioners, particularly GM products circa 1990 or thereabouts.

These have a wide centre hole, a narrow race and a narrower outer diameter than a wheel bearing.

I think you will find this route a dead-end as have other developers done and abandoned early in the research phase.

An old bearing will run free but will be noisy. A new bearing will be too tight and kill off any lightweight motor and battery unless you remove the seals and dissolve the grease out with solvent and replace it with light oil.

All of these options are almost the exact opposite of operating mechanicals near optics which must be kept clean and grease free.
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Old April 19th, 2006, 10:10 AM   #26
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Bob,

Thanks for the feedback on the bearing. I found out that bearings can be ordered to either accept grease or oil, so I think an oil bearing would diminish the noise issue. But I can see the oil conntaminating the inside of the tube. Thanks for sharing this info.
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Old April 19th, 2006, 10:23 AM   #27
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P+S technik was using the rotation with dead center on their forst model.
they stopped it due to complaints about the "vortex effect" it caused while looking at video.
I had made such design (with 55mm inner circle) for my first mini35, but never take the time to put the stuff into rotation.
I think the vibrating glass got more success.
The idea vwould be to glue an ultrasonic transducer on the glse so you can clean dust just by activating it.(same as done on some digital SLR camera).
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Old April 19th, 2006, 11:07 AM   #28
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Thanks for your in depth reply. At least I know that I should consider another route that could yeild better results.
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Old April 19th, 2006, 11:27 AM   #29
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Two narrow race ball bearings, preferably twinrow races, one able to fit inside the inner diameter of the other with about 6mm clearance, then an eccentric sleeve to fit the inner bearing outer ring snugly inside the inner ring of the outer bearing would do the job with about a 3mm excursion available by the time you leave some metal on the thinnest portion of the eccentric sleeve.

The outer rim of the outer bearing is fixed to the housing of the device. The inner rim containing the groundglass also remains fixed from spinning but free to move in an orbital motion. The outer rim of the inner bearing, the eccentric bush and innner ring of the outer bearing move as one. this provides the orbital motion.

This is a design I have examined but abandoned due to sourcing difficulties with suitable bearings. The inner and outer bearings would have to be custom made with free balls working in the races.

For the loadings a GG would impose, something like silversteel, hardened after machining would probably suffice for making the custom races. The eccentric bush could be eliminated in favour of having an integrated inside/outside facing race with offset centres.

The intention was to machine small belt pulleys onto the outer rim of the eccentric section and also around the rim of the GG frame.

The belt around the GG rim is only there to stop the spinning of the GG and to have enough stretch to allow the GG to orbit. It replaces a sliding key channel and pin which would wear and get noisy.

Except for the machining of two x two rows of bearing tracks and the frustration of trying to get all those tiny bearing balls to obey and stay put during assembly, it would be a simpler solution than the three-crank or four-crank orbiting systems.

The eccentric sleeve, if made slightly thicker could be drilled to provide partial counter-balancing.

The CD disk system although bulky, remains the simplest and most reliable for low budget home builds.
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