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Discussion Starter · #1 ·
Does anyone know how serious a problem the reported oil leaks are? I know I heard that this was to be expected if the temp got above a certain # but I cant remember what the results of the leaks are. Is it just a matter of cleaning off the oil or does this damage the seal? Will this cause changes to be made to either the design or assembly process?

One more thing; I know Larry Davis has had his for a day or two now so I would assume that others are starting to get there lenses also (this assumes that more than one lens is produced every three days but I don't know for sure) and hopefull they are not having the same problem. So if any of you lucky first lot people want to share your experiences I am sure a lot of people are interested.
 

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I just received a P752 today and it was not leaking at all. I also talked with Shawn and he plans to work over the weekend to work on the issue and keep units shipping next week.


Tom
 

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I see a super thin film of oil. It's not dripping. It's a microscopic leak. As Tom said, Shawn knows about this and he will fix it.
 

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Discussion Starter · #5 ·
Larry, is there a gasket or seal that is leaking or is it just a bead of silicon (or equivalent) that is leaking? Once the temperature goes down does the leak stop or is the lens ruined. How careful are we going to have to be with heat and the positioning of the lens. Is it a mandatory outside the hushbox installation?

Tommyboy2. aren't you the lucky one. First to have the original and now second to have the 752. You should expect the Panamorph 2 next week. later
 

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Re Panamorph oil temp.


Did I read somewhere that the Panamorph oil temp limit is 95 degrees F? If they're being shipped UPS, it is fact that in summertime, their brown pick-up trucks sometimes achieve 130 degree F inside temperatures during the daytime. Depending on how long our beloved lenses sit in these trucks, is it any wonder they spring a leak. Maybe these delays (till cooler shipping days) could be a blessing!


I never thought I'd say that!
 

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I'm afraid the panny may need a retrofit(drill and tap) with a oil refill plug and dip-stick. Actually this would provide for dry assembly. May-be we could add an optional pressure relief valve for high temperature applications and Shawn could sell refill-kits and oil at $10 a teaspoon, or maybe an optional panamorph heat exchange device. Any other problems, just let me know. I am an eggi-neer.



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--Bob
 

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Martin,

I'm not sure how to answer your question. The leak is at the bottom of the lens. There seems to be some kind of baffle or notch or I don't know what, at the bottom of the lens. Like it fits in there. Clear as mud, right? I don't know how Shawn has put this thing together. I don't work at or for, Cygnus, so just by eyeballing it, I can't tell much. There does appear to be an adhesive at one of the lens junctions. I don't know what is at the lens/aluminum joint/seal. I simply can't see what's there.


I would assume that since heat causes liquids to expand, that heat would cause an expansion of the oil in the lens. I think Shawn put some emphasis on the heat rise being slow as opposed to fast. A fast increase in temp might prompt a leak. I don't want to put words in Shawn's mouth, so I remind you these aren't his words. I was under the impression that the lens was supposed to handle a slow increase in temp, but a sudden, dramatic rise might overcome the barriers (whatever they are) and a leak could develop.


I wish I could say more, but I can't answer your questions about hushboxes or the heat issue. I don't know the current state of progress on lens assembly or the QC steps that are in place at Cygnus. Your questions are valid, but I can't answer them. It is dawning on me that keeping the oil in the lens is like keeping the genie in the bottle. I'm sure it can be done, but there are some kinks that need to be worked out. I will send my lens back to be repaired when Shawn has this problem fixed. Tommyboy2 said his lens had no leak at all. I am looking forward to a more detailed appraisal when he gets a chance. We are heading into the hottest month of the year (August). It's important that the problem be fixed and I'm sure it will be.
 

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Discussion Starter · #9 ·
Larry, the one good thing about this is that if the tolerances are so tight that you can't tell what the seal is by looking the build quality must be very precise. It should look good. I also remember Shawn saying something about the quick rise in temp being the problem and if the temp rose slowly the lens could tolerate more heat. More than likely your lens has been through what could be considered a torture test in the back of the UPS van and those that survive the trip to our doors should have no problem with heat once installed. Maybe Shawn should contact one of the companies that ship frozen meat and add a few lenses to the BBQ delivery. Once delivered cook to taste and then install. later
 

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In response to Larry's unit having even a small leak from shipping we reexamined the seal structure. Each cavity contains a diaphragm to relieve pressure during volume changes, particularly during temperature variations possible during shipping. Each diaphragm is held with a clamp with ten screws. Apparently there are extremes under which this approach is inadequate. We have created a new approach which crimps the diaphragm instead of using screws. This provides a much more uniform seal pressure around the diaphragm while also removing screw holes that may have been a channel for leaks under pressure. We have now successfully tested a crimp-sealed system at freezing temperatures and also at 150 degrees for an hour. Machining has begun to create replacement components using this new approach. This should be finished on Monday and we are hoping to get the parts back from anodizing by Wednesday.


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Shawn Kelly

Cygnus Imaging
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Shawn

Its good to hear you are onto this small problem. I guess with variences of temp and three different surfaces (alloy,glass and rubber) involved, different rates of contraction and expansion place demands on the seal.

Are you using a moulded seal to sit the glass into ?

Just out of interest can the user refill the oil ?

Using liquid to transfer the light seems like a pretty good and simple option over using coatings.


DavidW
 

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I was just curious is there a reason why there using oil. I thought the originla panamorphs used prizms. Is it just more cost effected to use oil or is there something else?

That the oil offers compare to the prizm.



Just curious

Hugo
 

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Hugo


If I am correct, just as a good quality lens will have coatings to increase contrast and light output the Panamorph achieves this by adding a liquid to the prism.


I also think this aides to cut down any unwanted reflections that would also deteriorate the image.


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Alan Gouger

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Forgive me for asking something that's intuitively obvious- but if liquid makes a better refractive prism, why doesnt nasa use it for those telescopes they hoist into space, instead of machining mirrors and lenes to high tolerance$. Leaks , I guess.

 

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Reflective optics such as telescopic mirror systems have many advantages over refractive optics. One of the primary advantages is that it easier to make a large mirror than to make a large lens. Telescopes need large optics in order to gather as much light as possible. Since a mirror can be supported from below it possible to produce very large mirrors that are mostly hollow which helps reduce weight. It's also easier to grind one surface with optical precision rather than two.



Reflective optics also do not suffer from chromatic aberration which can be thought of as an unwanted prism effect. Reducing chromatic aberration requires the refractive elements be multi layer lenses made up of multiple glass layers that are bonded together using optical cement. Each layer of glass has a different index of refraction that is carefully chosen to correct the chromatic aberration. Since its difficult to produce glass with a specific index of refraction there will always be some chromatic aberration with refractive optics.


The optical fluid in an Panamorph is being used to reduce chromatic aberration. The optical coatings on the exterior flat sections of the glass are what reduce reflections.
 

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Is there any chance that ambient heat or heat changes in the room will cause convection currents in the oil and thus visible "waves" (hopefully very small, if any)in the protected image.
 

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Shawn mentioned at the Panamorph Party that a significant change in the temperature from one point in a presentation to another could cause a temporary change in the compression ratio. This can easily be accounted for with the provided adjustments. I'm no thermal dynamics expert (I'll bet that there's one in this forum http://www.avsforum.com/ubb/wink.gif ), but it seems like a convection wave would require an extreme heat source. I don't know if the vent from my VT540 (which will be directly above/below the P752) would qualify as extreme. Hot, yes, but not extreme. I would say, definitely don't mount this over the campfire in your teepee http://www.avsforum.com/ubb/wink.gif



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Quote:
Originally posted by karos:
Forgive me for asking something that's intuitively obvious- but if liquid makes a better refractive prism, why doesnt nasa use it for those telescopes they hoist into space, instead of machining mirrors and lenes to high tolerance$. Leaks , I guess.
Building optical systems for spacecraft using mirrors and lenses is difficult enough without trying to manage a liquid in space.


For example, when constructing a supercooled instrument (from hard materials like aluminum, etc) there's a major bit of engineering and a minor bit of luck to get the right alignments when the instrument is chilled (ie when you sink into it's bath of liquid nitrogen or helium). Parts move around quite a bit depending on the thermal characteristics of the material its made from.


Few liquids will remain liquid at these temperatures and those that do probably make lousy optical mediums or don't have the right wavelength characteristics.


Non-supercooled instruments also go through an extreme range of temperatures. This is controlled through radiators and heaters but the bottom line is that you have to design the components to be tolerant of heat changes as you go from sunlight and dark conditions.


You'd see more signficant changes from temperature using a liquid as opposed to solid optical system.


As an example of the effects of heating and cooling, the first solar panels (built by ESA) for Hubble were built on spiral telescoping arms. Very efficient in terms of deployment and size but as they found out, flexes during temperature changes. This resulted in a very slow flapping motion on the panels that slowly jiggled the spacecraft...leading to even more fuzziness in the images.


They were replaced on the first Hubble servicing mission.


Nigel
 
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