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Post by Ron Walker on Aug 24, 2022 11:22:58 GMT -7
Posted by: Ron Walker Jan 7 2008, 03:57 PM The Latitude motor is also a 1/70HP 1725 rpm motor. This motor has a different speed reducer on it providing 3.5 inch/lbs of torque at 58 rpm with a 30:1 gear reduction.
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Post by Ron Walker on Aug 24, 2022 11:25:48 GMT -7
Posted by: Ron Walker Jan 7 2008, 04:18 PM Note that the Daily motion motor goes through a 2:1 reduction when it enters the central core before it drives the large 78:1 worm gear. The latitude drive motor connects directly to the large 78:1 worm gear. The 2:1 bevel reduction gear is probably why the drive motor runs faster for the daily drive. What I don't understand is why the faster output shaft has a higher torque rating, unless it is harder to stall the faster turning shaft.
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Post by Ron Walker on Aug 24, 2022 11:26:29 GMT -7
Posted by: charles jones Jan 7 2008, 07:17 PM Ron, thanks for all this!
I also cannot understand as I would have thought the slower RPM rating would produce a higher torque.
The reason for all this is to get an idea of how large a motor to purchase for these two functions. And I believe I will be using a similar setup as in the A3P. Reason: My design is keeping the northern and southern assemblies very close together leaving little room for this size daily motion motor even though it makes more sense to mount it in the central core.
Also, it makes more sense to mount the latitude motor on top of one of the supports. However, this may interfere with the projection of some stars and planets near the horizon. In this design, a portion of the northern stars are projected from the southern assembly globe as you know. That means there will be some projector positions that a motor would obstruct some stars. So, the less up there, the better.
I can visualize the motor for annual motion and the two synchronous motors for precession can be smaller (less torque). These have to be mounted on the northern and southern assemblies.
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Post by Ron Walker on Aug 24, 2022 11:29:57 GMT -7
Posted by: Ron Walker Jan 16 2008, 04:41 PM My first mechanical deviation from the original design it to slow down the daily motion. The original Spitz A3P was designed to run off a day from about approximately six minutes to approximately one minute. I personally think that one minute is much too fast and indeed Spitz even states that this speed is provided for setting the projector between shows and not designed for use during a show unless you want to get people ill. Since I don't mind at all taking my time with setting the projector, I really didn't need a speed as fast as one minute. On the other end I really didn't think a day in six minutes was slow enough. There are demonstrations during which I would like a slow moving day. My initial thought was that a ten minute day would be very good. Playing around with the Homestar I really liked that motion and it is stated to be twelve minutes. With a simple 2 to 1 gear reduction on the daily drive motor I would have a drive speed of twelve minutes down to two minutes. It would also add some extra torque to the entire system which should help out at the slowest speed. Some time ago, when I was planning on making my own planet cage, I purchased a bunch of small plastic pulleys with a nice 1/4 inch ball bearing on the inside. Since I'm not the best machinist in the world, I thought these would be perfect for use as bearings in anything that I build because the outside plastic pulley could be used as a mounting flange. The original drive consists of a DC motor which runs through a right angle worm drive terminating in a 5/16 inch shaft facing directly upward through the main bottom support plate for the entire planetarium. A small universal joint coupling transfers the power from the 5/16 inch shaft to a 1/4 inch shaft which drives the daily motion. Since I've tried to standardize on a 1/4 inch shaft, I first needed to reduce the 5/16 inch shaft of the motor down to 1/4 inch. I also wanted a longer shaft to be able to mount other devices. I could have machined down the original shaft but it would not have been long enough. Besides, making an adaptor was easier then taking the motor apart. Then I used two of my small bearings (one on each side of the base plate) to make a support for a second shaft. The next step was to place the two timing gears on their respective shafts. I used a 40 and 80 tooth gear set.
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Post by Ron Walker on Aug 24, 2022 11:32:57 GMT -7
Posted by: Ron Walker Jan 16 2008, 04:53 PM I also designed the unit to run a 3/1 drive (40 to 120 tooth gears) in case I wanted a day as slow as 18 minutes. I was planning on buying a new universal joint to connect the 1/4 inch new shaft to the existing drive shaft, but at $40 bucks a crack, I thought I'd try my hand at making a very fine shaft adapter and use the existing universal.
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Post by Ron Walker on Aug 24, 2022 11:34:18 GMT -7
Posted by: Ron Walker Jan 16 2008, 04:56 PM It worked perfectly. The finished instillation is shown below. It is set up for the simple 2 to 1 gear ratio. Eventually I will probably add the other gears for the 3 to 1 drive mounted as well. First I need to see if I really need that slow of day and I'm using that particular gear right now for other experimentation.
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Post by Ron Walker on Aug 24, 2022 11:34:53 GMT -7
Posted by: Owen Phairis Jan 16 2008, 05:03 PM QUOTE(Ron Walker @ Jan 16 2008, 03:56 PM) * It worked perfectly. The finished instilation is shown below. It is set up for the simple 2 to 1 gear ratio. Eventually I will probably add the other gears for the 3 to 1 drive mounted as well. First I need to see if I really need that slow of day and I'm using that particular gear right now for other experimentation. Ron, Great and interesting report! My S-2 projector runs around 7 or 8 minutes per day and I always thought a little slower might be nice. Snowing and 2 degrees this morning in Aspen. Owen Planetarium Projector and Space Museum www.pictorialism.com
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Post by Ron Walker on Aug 24, 2022 11:39:03 GMT -7
Posted by: Ron Walker Jan 16 2008, 05:43 PM The next step (and most complex) is the conversion of the multiple synchronous drive motors for the various planet projectors to a single DC motor drive. In the posts above, you can see the removal of the various drive motors from the various planet projectors. The Sun motor was mounted directly in the center. Since each of the projectors was driven by the same speed motor (the Moon is different and we will talk about it later) all of the analogs require the exact same rotational drive speed, basically the Sun through a period of a year, or the movement of the Earth around the Sun. Since Mercury orbits in about 88 days, its analog required the most torque to drive the gear system. Saturn required the least. Thus I desided to drive this analog directly and allow the other units to derive power from it. My first Idea was to use one large timing belt that would interconnect all of the analogs. Again I machined small adapters to change the 1/8 inch shaft of the analogs to 1/4 inch. They also needed to be longer to allow for my various changes. This worked but I noted a few problems. Since each timing gear only engages a few teeth of the belt, the entire system must be put under a fair amount of stress so as not to slip. I think the stress on the various bearings and the adapters would be too much. The way around this was to add a second gear to each shaft and then have a timing belt between each unit. This allows each gear to have half its teeth engaged at all times.
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Post by Ron Walker on Aug 24, 2022 11:39:39 GMT -7
Posted by: mrgare5050 Jan 17 2008, 08:24 AM something tells me they dont sell those belts at auto zone...
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Post by Ron Walker on Aug 24, 2022 11:40:53 GMT -7
Posted by: Ron Walker Jan 17 2008, 08:58 AM QUOTE(Owen Phairis @ Jan 16 2008, 05:03 PM) * Ron, Great and interesting report! My S-2 projector runs around 7 or 8 minutes per day and I always thought a little slower might be nice. Snowing and 2 degrees this morning in Aspen. Owen Planetarium Projector and Space Museum www.pictorialism.comThanks Owen. Post some pictures of the drive when you get back and I'll try and come up with a simple way to lengthen your day. Pack a lot of batteries for your cameras. Two degrees and here I'm complaining about the 50's.
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Post by Ron Walker on Aug 24, 2022 11:41:18 GMT -7
Posted by: Ron Walker Jan 17 2008, 09:05 AM QUOTE(mrgare5050 @ Jan 17 2008, 08:24 AM) * something tells me they dont sell those belts at auto zone... That's for sure. I've done a lot of work with larger (what they call light) timing belts but thought, because of the spaces involved, the very slow speeds, and the low torque, that I would use the "Extra Light" belts. They appear to be working out fine. They can be found at: www.sdp-si.com/
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Post by Ron Walker on Aug 24, 2022 11:41:43 GMT -7
Posted by: mrgare5050 Jan 17 2008, 09:23 AM planetarium people love 'arcane' machinery do they not?
you can buy almost ANYTHING and turn it into planetarium equipment.
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Post by Ron Walker on Aug 24, 2022 11:44:26 GMT -7
Posted by: Ron Walker Jan 17 2008, 11:46 AM The Sun projector was driven by a motor mounted directly in the central analog core. An aluminum rod was used to connect the motor shaft to one of the hollow type rods that is used to drive the projection mirrors. You can see the tip of the aluminum rod and the connection to the thin shaft in this picture of the central core. I machined a simple 1/4 inch brass rod to replace the motor drive shaft and allow mounting of other new drive components. To the right is the original aluminum drive shaft and to the left is the new added brass rod. On it you can see a set of my special bearings and a large 120 tooth drive gear. The Mercury and thus the rest of the planet analogs would now be driven from the central Sun analog position. Here is a test set up of the new drive system hung in place with a 40 tooth gear. I basically picked 40 teeth so that the gear would not cover the shaft that allows adjusting of each individual analog and would allow the continued adjustment of the analogs from the back of the planet cage. You can also see the two ball bearings that have yet to be mounted, one on each side of the back plate where the Sun motor was mounted before.
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Post by Ron Walker on Aug 24, 2022 11:44:52 GMT -7
Posted by: mrgare5050 Jan 17 2008, 11:52 AM why 40? a rather biblical number
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Post by Ron Walker on Aug 24, 2022 11:48:17 GMT -7
Posted by: Ron Walker Jan 17 2008, 12:02 PM My basic gut feeling is that the amount of torque required on this main drive gear might be to much so I desided to increase the size of the main drive gear to 120 teeth. Because of the larger circumference and the larger number of gear teeth engaged, the amount of torque on the belt is reduced significantly. The only problem is that the gear is so large that it will prevent the extension of the setting drive shaft to the back of the motor cage. It can still be set from the interior of the drive cage but will require the opening of the central unit. For me, this is not a problem, since the positive gear drive will do away with any slippage that existed in the unit before due to "electronic slippage". The only reason that I foresee of needing to change the planet positions is if I give a show relating to another time period such as the "Star of Bethlehem". I would do a preset of the machine before the show so it would not be a problem at all. Here you can see the adjustment shaft at the top of the analog blocked by the larger drive gear. The small coupling would be replaced with a larger thumb wheel for easier adjusting. Here is a shot of the central drive with 120 gears in place. The central Sun drive will be driven from the moon position with a 12 to 1 reduction gear. I must buy more parts so I will continue this saga at that time.
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