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Post by Ron Walker on Aug 24, 2022 13:31:27 GMT -7
Posted by: Ron Walker Mar 3 2008, 12:28 PM QUOTE(charles jones @ Mar 2 2008, 05:05 PM) * Do you think a small motor could be attached to the shaft for the planet adjustment in each analog? Do you think it would require more torque to move them than a small motor similiar to the ones that are built into the A3P can provide (the little Bristol synchronous motors)?
As I recall several of the analogs I have were hard to move. This may only be because they need a little loosening with lubricant. I remember the Mercury and Venus analogs are adjusted from outside the plastic containers, using a worm gear and were easily moved. Several of the other analogs were harder to move.
I guess that depends on how fast you want to make the adjustment. Remember that the analogs are run by a 2/3 rpm motor. Also I found the adjustments harder to turn then the actual analogs. That's probably because you have to overcome the friction of a slip clutch. If you add a motor you might be able to remove the slip clutch as the stopped motor would replace it. I know Spitz added motors for the inferior planets when the A4 came out. Not so sure about the superior planets as I believe that shaft turns normally during planet operation.
The inferior planet analogs that I have are adjusted from the back just like the superior ones. The use of a worm gear negates the need for a clutch and increases the torque considerably, so they would be very easy to adjust. It is the actual normal drive that varies in required torque depending on the gear ratios required for operation. The hardest analog to move should be Mercury (which is why I placed it as first drive from the Sun), followed by Venus and Mars. Jupiter and Saturn should be fairly easy to turn and then the Moon easiest of all.
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Post by Ron Walker on Aug 24, 2022 13:31:50 GMT -7
Posted by: charles jones Mar 3 2008, 03:03 PM How, weird! The analogs I have definitely have Mercury and Venus adjusted by a thumb screw shaft that is at right angles to the planet/mirror shaft and goes through the plastic case. So, there must have been variations on the A3P. I wonder if I have one of the earliest A3P analogs.
I don’t have the unit in front of me, but I would suspect you still need the friction clutch or some kind of differential to direct motion to the planet via the sun drive (reduced) and via the thumb screw adjustment drive through a second motor. You would still need the gear train to move from the sun projector motion.
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Post by Ron Walker on Aug 24, 2022 13:32:14 GMT -7
Posted by: Ron Walker Mar 3 2008, 07:03 PM QUOTE(charles jones @ Mar 3 2008, 03:03 PM) * How, weird! The analogs I have definitely have Mercury and Venus adjusted by a thumb screw shaft that is at right angles to the planet/mirror shaft and goes through the plastic case. So, there must have been variations on the A3P. I wonder if I have one of the earliest A3P analogs.
I don’t have the unit in front of me, but I would suspect you still need the friction clutch or some kind of differential to direct motion to the planet via the sun drive (reduced) and via the thumb screw adjustment drive through a second motor. You would still need the gear train to move from the sun projector motion.
Yes you have the earliest version of the A3P. When they "improved" it by allowing the adjustment rods to go straight back they basically saved themselves the cost of a worm and gear. Now they just need a slip clutch which allowed them to save money and stock fewer parts. Since the required the slip clutch on the superior planets anyway.
This is kind of hard to explain without a unit directly in front of you but here goes. If you look at the operation of the inferior planets, the aluminum bar caries the magnet that holds the steel ball that represents Mercury or Venus. The normal rotation of this bar is derived from a stationary gear at the base of the analog. As the large thick plate rotates representing the Earth motion is generated by gearing connected to this stationary gear that turns the aluminum bar. The adjustment knob rotates this stationary gear and thus the inferior planet bar around until the planet is projected in proper place for any given time.
With the superior planets this job belongs to the large thick disc and the aluminum bar now caries the Earth. Since all the Earths must always be lined up together, you can not adjust the planet as above. You must turn the large disc via the adjustment knob. This large disc representing the superior planets derive their motion from the main drive turning at Earth speed. The adjustment knob is just placed within this gear train. The drive power normally just transfers through a friction clutch and is overpowered when you turn the adjustment knob. I would imagine this is why the latest versions of the projector don't have the extra motor (at least I don't think they do, I have yet to see a 1024). If you had a motor there its load would probably stop the entire analog unless you had a magnetic clutch that kept the motor disengaged unless you were using the adjustment motor.
Remember that both motions (the planet and the Earth) are derived from the central shaft that rotates at Earth speed. The aluminum bar is sped up for the inferior planets and the large thick disc is slowed down for the superior planets. Also any adjustment can only be made to the projected planets drive and not the Earth position as the Earths position must be synchronized and be in exactly the same position for each analog. This is one of the problems that electronic slippage causes with this type of drive. After enough of it you could have a planet like Mercury moving back and forth next to the Sun rather then around it, or you could have Mars go into retrograde motion next to the Sun rather then at conjunction. The nice thing about tying all of the analogs together with the timing belts is that once all of the Earth positions are synchronized together, then the planets should all "rotate" around and do what they should do at any given time. This still allows you to set any planet or group of planets to any position and any theoretical possible conjunction you would like to produce. The system is just as easy to set as before but you no longer have to worry about "electronic slippage" which probably made up about 99% of the improper placement of the planet immages.
The only capability that is denied this timing belt drive is to be able to show the phases of the Moon as it is held stationary in the sky. This could be overcome easily with a clutch and an extra motor but I think it would lead to confusion in the audience. The phases of the Moon are a direct result of its rotation about the Earth and thus should be observable in the planetarium sky. With the new motor drive a month can be reduced to more then half a minute. This allows a substantial amount of time to show the phases with respect to the Sun's position and to planetarium time. The daily motion can be engaged to hold the Moon in position if you want to hold the Moon in one position as the phase changes, but the entire projection will remain accurate to the observer. A full Moon showing right next to the Sun will never happen again.
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Post by Ron Walker on Aug 24, 2022 13:32:35 GMT -7
Posted by: chemed Mar 4 2008, 10:49 AM why not make a SPFX projector that does moon phases? My projector has two moon projectors, one with the moon phases tied to the position of the sun (has a diurnal/annual coupler), the other is just a phase motor.
Does the A3P come with an ecliptic? It probably does, I'm just curious. Will the sun rise and set, if so, how is it turned off...automatically or manually?
For your timescale, will you run sidereal time?
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Post by Ron Walker on Aug 24, 2022 13:32:53 GMT -7
Posted by: charles jones Mar 4 2008, 01:35 PM QUOTE(Ron Walker @ Mar 3 2008, 07:03 PM) * Yes you have the earliest version of the A3P. When they "improved" it by allowing the adjustment rods to go straight back they basically saved themselves the cost of a worm and gear. Now they just need a slip clutch which allowed them to save money and stock fewer parts. Since the required the slip clutch on the superior planets anyway..
I am assuming that the worm gear in the inferior planets also went through a friction. Don't know as I am still gone and can't see it for myself.
I think what you have done to tie all the planets together without slippage is great and one I will follow if I ever get home and start building.
I can't remember the great Zeiss in Griffith ever being able to show the moon's phases without the movement of the moon across the dome.
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Post by Ron Walker on Aug 24, 2022 13:37:49 GMT -7
Posted by: Ron Walker Mar 4 2008, 01:40 PM QUOTE(chemed @ Mar 4 2008, 10:49 AM) * why not make a SPFX projector that does moon phases? My projector has two moon projectors, one with the moon phases tied to the position of the sun (has a diurnal/annual coupler), the other is just a phase motor. Does the A3P come with an ecliptic? It probably does, I'm just curious. Will the sun rise and set, if so, how is it turned off...automatically or manually? For your timescale, will you run sidereal time? If this entire retrofit that I'm doing works the way I think it will blink.gif then there will be no need for a SPFX projector. Spitz chose to make the Sun and Moon both two degrees in the sky. Probably as a result of the projector designed for smaller 20 to 30 foot domes. Zeiss did the same thing only held to one degree and only after viewing a true half degree projection looked just too small. The two degree projection of the Spitz look just fine to me and using an actual picture of the Moon to project out gives the Moon an extremely good look. Perhaps some time in the future I would look into a SPFX unit that makes a larger projection would be in order. The projectors for the equatorial hour circle and the ecliptic are at the far south end of the planet cage. From bottom to top we have the equator/hour circle projector, in the middle the projector for the ecliptic, and then at the top the plate holding the projectors for the planets and the Sun. In the A3P the hour circle and ecliptic projectors were simple "brute force" light and shadow projectors. In the A4 and later models, these projectors were replaced with optical units placed directly below the star ball at the north end. You will note the the lamps and optics for the Sun and planet projectors are fixed on the plate which eliminates the need for slip rings for these projectors. The design for these systems is actually quite brilliant in eliminating parts that can cause problems. As you can see, the projectors themselves project into front surface mirrors through holes in the plate. From this hole (top of picture) the image of the planet is projected onto a second front surface mirror and then out to the dome.
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Post by Ron Walker on Aug 24, 2022 14:09:31 GMT -7
Posted by: Ron Walker Mar 4 2008, 02:29 PM QUOTE(chemed @ Mar 4 2008, 10:49 AM) * why not make a SPFX projector that does moon phases? My projector has two moon projectors, one with the moon phases tied to the position of the sun (has a diurnal/annual coupler), the other is just a phase motor. Does the A3P come with an ecliptic? It probably does, I'm just curious. Will the sun rise and set, if so, how is it turned off...automatically or manually? For your timescale, will you run sidereal time? The Sun better rise and set or I wouldn't have much respect for the projector. I'm assuming that you are asking how the image of the Sun (Moon and planets) are kept from projecting below the spring or horizon line. On my small Goto E-5 which has what I call a more classic planet projection which consists of a projector between two geared points (one representing the Earth and the other the planet projected) the projectors are turned on and off by small mercury switches attached to the projectors themselves. As the optics start to project below the horizon, the mercury shifts do to gravity and the projector is turned off. At first I thought this was a great idea until I realized that the constant on off of the lamp (especially at full voltage) really took a tole on lamp life. Being the "story teller" as well as the operator, I didn't want to rely on manual operation of the power supply to brighten an object just before it rose. Also, since all of the planets are on one circuit, it would require being left up as I doubt there would be many times all of the planets would be below the horizon. My first thought was to place a resistor across the mercury switch so that a small amount of current would keep the filament lit, but at a much lower level then normal. This would help with bulb life but would still allow projections of the planet images below the spring line and into the eyes of the audience. My plan with that projector is much the same solution as the original Zeiss I projector used. (More on this when I actually do it.) I bring all of this up because it relates to the very simple but elegant solution that is used in the A3P and all of the following series. Around each analog mirror is a small half drum which is weighted keeping the solid half always pointed towards the ground and the open half facing the dome. When the image of the planet (Sun or Moon) reaches the spring line it is occulted by this half cylinder until it reaches its rise point 180 degrees away. This mirror is aimed at the midnight position for the Sun projector. The image is just absorbed by the black paint of the drum. Here the image would be projected out just before Sun or planet set. In later projector series they added small adjustable vanes that could adjust the exact point of occultation. I'm thinking of adding (hot glue guns are wonderful) a thin strip of orange gel, so that as the Sun nears the horizon it will turn golden orange as in nature. Since these are all optical projectors, the image is so out of focus at this point that the transition from clear to golden will be slow and soft and not a line across the image. This final picture shows the entire planet cage with each mirror/cup assembly offset in such a way that none get in the way of any other. The thin frame wire of the support system is such that again considering the images are so out of focus at this point that the only effect on the projection is a slight dimming of the smallest projected images. It is surprising so slight that you must be looking for it to perceive it. The positive to all of this is that the projectors can all be left on for an entire show so that there would be no quick off/on cycles at full voltage so detrimental to filaments and that they have the extra heat sink advantage of the common mounting plate. As far as time goes, I am just sticking to solar time as I really don't foresee the need for a sidereal readout. If I really need it I could just subtract the four odd minutes off the position. I really want these readouts just to get an idea of how much night has gone by during my presentations.
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Post by Ron Walker on Aug 24, 2022 14:10:15 GMT -7
Posted by: Ron Walker Mar 4 2008, 02:43 PM QUOTE(charles jones @ Mar 4 2008, 01:35 PM) * I am assuming that the worm gear in the inferior planets also went through a friction. Don't know as I am still gone and can't see it for myself.
I think what you have done to tie all the planets together without slippage is great and one I will follow if I ever get home and start building.
I can't remember the great Zeiss in Griffith ever being able to show the moon's phases without the movement of the moon across the dome.
It will be interesting to see. Having a worm gear would hold the system still unless the actual worm was turned by the finger knob, but they might still have had the friction clutch.
When I receive this final order of parts we shall see if my plan works or not. Also I should be able to measure the exact amount of torque required to make the entire system move.
You are correct on the Zeiss. It had to move in the planetarium sky to show phase as it relates to the Suns position.
When you ordered you motors did the subject of position ever come up? There is a note in the Bodine book that mentions keeping the motor level or possible spillage of lubricant might result. Perhaps the smallest ones don't have this problem but it is something to look into.
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Post by Ron Walker on Aug 24, 2022 14:10:39 GMT -7
Posted by: chemed Mar 4 2008, 02:56 PM I've never fully understood how the planets are projected on an A3P, but that last description and picture really put it all together for me. Thank you!
my GOTO runs on mercury switches too for each planet. the voltage is supplied via slip rings. It is getting hard to find replacement mercury switches. You may have guessed, that I'm asking these questions for a reason. Well, I'm seriously considering trading out the GOTO for an A3P.
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Post by Ron Walker on Aug 24, 2022 14:13:03 GMT -7
Posted by: Ron Walker Mar 4 2008, 03:51 PM QUOTE(chemed @ Mar 4 2008, 02:56 PM) * I've never fully understood how the planets are projected on an A3P, but that last description and picture really put it all together for me. Thank you!
my GOTO runs on mercury switches too for each planet. the voltage is supplied via slip rings. It is getting hard to find replacement mercury switches. You may have guessed, that I'm asking these questions for a reason. Well, I'm seriously considering trading out the GOTO for an A3P.
That's a hard call. The Goto you have is a fantastic machine. Everything would depend on what all the problems are with the projector you have.
What goes wrong with the mercury switches? I didn't think there was anything to go wrong. I'd need to get some more detailed pictures of the planet cages and their interaction with the rest of the projector, but you might be able to build some mechanical horizon cut offs for it.
If there are a lot of mechanical and electrical problems they would need to be judged point by point. As I remember you said you had a 24 foot dome. Your machine is designed for a 30 to 40 foot dome so there could be some overlap of the star fields. This may or may not be a problem for you. I've never been close to a projector like yours so It's hard for me to judge. Very detailed pictures of each problem area would help.
I will say in support of the A3P is that it is a much better projector then I thought it would be. Also you can see that I'm basically removing and rebuilding any of the sections that I fear will show the age of the machine. If all of my experimentation works (and I have no reason to believe it won't) I expect the projector to run as long as I'll ever need it and then some.
The big difference between the two projectors is that yours is more "Zeissie" in that it is built like a tank and is also all optical projection. These are nice pluses but none of that matters if it doesn't work, so the final call must remain with you.
Again I would suggest we go over each and every problem to try and find a simple fix. Remember the cooling fan drive motor problem turned out to be just a loose slip ring. Has that fix held up or is it still causing problems?
When I first got my Goto E-5 the motors ground and gowned, the planets "jumped" along and the various lamps flickered. I'm not complaining as I purchased it as is. After tearing it completely apart and cleaning, re-lubricating, and rewiring, the projector works like new. Like all Goto's, even though small, it is built like a tank. I also built a new control section as the old systems were beyond my help and expertise.
I'm glad I was able to help in your understanding of the A3P and if I can be of any help with your Goto, just ask. If you don't know yet, I really love this stuff! tongue.gif
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Post by Ron Walker on Aug 24, 2022 14:13:43 GMT -7
Posted by: chemed Mar 4 2008, 06:49 PM The GOTO starfield is pretty great. The projector has so many moving parts, pieces, wires, lenses, bulbs, mirrors...etc. Its a very large, complicated, expensive clock.
What I really have to consider is the "educational value" of my projector. Unfortunately, along with its projection capabilities, that means: availability of parts, longevity, and ease of service.
I have a list of things that need to be done to the projector, and we can pick them out one-by-one, if you wish. I will post more in "Chemed's Planetarium", I don't want to hog the space for your A3P. The motor malfunction problem is still "solid". Occam's Razor, right?
and don't worry, there will be pics
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Post by Ron Walker on Aug 24, 2022 14:20:22 GMT -7
Posted by: Ron Walker Mar 10 2008, 04:07 PM Another bunch of parts arrive and I continue. As I've said before, the Moon projector is one of the more complicated for my rebuilding project since it was driven by four motors running at different speeds. The phase unit is quite interesting. Note the large black ring with slots placed in it. Each of these slots represents one complete Moon cycle. Originally it was driven by a 2/3 rpm motor placed just opposite the smallest gear. The slots actually make a very good phasing mechanism as a lens with a great amount of barrel distortion is placed in the Moon projector tube which this wheel bisects. This barrel distortion bends the edges of the slit to produce rather excellent looking phases on the image of the Moon projected. If you remember before I was having a problem as to how and transmit motive power to this point of the projector. I finally decided to use a set of 90 degree bevel gears as any other solution appeared to induce a greater amount of play in the system. From left to right we have the large phase box with a new bevel gear replacing the 2/3 rpm motor. The image is reflected 90 degrees into the dove prism which corrects for image rotation and has a 40 tooth belt drive replacing the 8 rpm motor. The light source end of the projector can be seen in the picture at the top of this post, just before the phasing mechanism. Once mounted, the interconnection of the Moon projector becomes evident. Mounted on the top (north end of planet motor cage) of the annular motor cage the Moon projectors gearing can be easily seen. The bevel gear for the phase, the bearing end for the dove prism which now resides inside the motor housing, and the main drive shaft to which I've added another bearing on the top plate. I felt that since the main motor would drive this shaft and that all the torque required would pass through this connection, having an extra bearing to support the load wouldn't hurt. (I tend to over engineer everything I build as I really don't want to go back in and rebuild again and again.)
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Post by Ron Walker on Aug 24, 2022 14:21:04 GMT -7
A close up view of the bevel gear for phasing which gets its power from the central motor core.
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Post by scotttucker on Aug 24, 2022 23:32:54 GMT -7
Thank you for rebuilding this thread Ron - I can't believe I missed this one first time around.
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Post by Ron Walker on Aug 25, 2022 10:08:07 GMT -7
Thank you for rebuilding this thread Ron - I can't believe I missed this one first time around. More to come. Can only do so much in a day.
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