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This tiddler was automatically created to record the details of this server
Arrange some potted bamboo, said to grow quite quickly, so that as the shoot gets longer, it moves the platform. Control the rate of bamboo growth by adjusting its water and plantfood supplies.
One of the key implementation details of the McCrearyMount is the use of extremely high-precision bearing balls. These are very, very inexpensive because they are routinely mass-produced by many companies world-wide to incredibly fine tolerances.
[img[Precision Bearing Balls|./images/balls.jpg]]
The balls that I intend to purchase for the prototype mount ar 1" diameter Grade 24 chrome balls, accurate to a precision of .000024" (that's 24 one-millionths of an inch!). These balls are available for the princely sum of $2 each in small quantity, plus shipping.
Founded in 1950, the [[Marsh Bellofram|http://www.marshbellofram.com/diaphragm.htm]] company designs and manufactures the exact device that I believe could be the ideal solution to the McCrearyMount drive problem.

It is called a "rolling diaphram" and I previously described my thoughts about something like this which I called the RubberDrive. The Bellofram company has a long history and engineering expertise in designing and manufacturing this kind of diaphram, and I hope to contact them the next time they are open to inquire about some technical and cost details.
[img[Rolling Diaphram Illustration|./images/bellofram.jpg]]
I clipped this excellent schematic illlustration out of an engineering guide that the company publishes on their website. All of the properties that the claims for the Bellofram product indicate to me that this could be the ideal device for moving the McCrearyMount!
Rather than support the edge of the platform from below, how about letting it hang from above with a block and tackle arrangement having a large number of pulleys?

The more pulleys, the smoother the average motion would be, and the finer the control would be over the speed of the motion.
Welcome to the ~CompactDrive (formerly known as the TrashBagDrive). Here are some photos of today's experiments, followed by a commentary:

I started with the same empty cylinder as used in the TrashBagDrive before:
[img[2nd Gen Experiement|./images/compact/cyl.jpg]]

This is the triple-layer 1.2mil trashbag with water in it:
[img[Triple Bags|./images/compact/bag.jpg]]

To assemble, lift it up:
[img[Bag and Piston|./images/compact/bagandpiston.jpg]]

Then drop it into the open-top cylinder, being careful not to pinch the bags between the piston and the cylinder sides:

Closeup of the ABS fittings:
[img[ABS 1.5" Fittings|./images/compact/fittings.jpg]]

Looking down into the open fitting; one port will be used for re-filling the bag with water after an observing session; the other will be fitted with a connection to the drip valves.
[img[Now You See It|./images/compact/open.jpg]]

Here is an alternate cylinder; I will probably make the "show version" of the ~CompactDrive from a section of this 12" pipe capped with some plywood and bolted together. Because it is basically "straight" and not "curved" as would be ideal, I will couple both ends of the cylinder with 1" bearing balls identical to the main axis supports.
[img[A Larger Cylinder|./images/compact/othercyl.jpg]]

This closeup of the edge of the piston shows that the bag is NOT quite coming through; however, in the final version I need to make a better-conforming piston; probably with some thick foam with plywood backing. It also needs to be thick enough to "self guide" in the cylinder to avoid complicated support rods.

Hey, if it can hold me quite comfortably, I should be able to compete head-to-head with Takahashi and Astro Physics! :) Takahashi wants $99K for a mount that will support 350 pounds! I also tested and determined that the added weight greatly IMPROVED the stability of the setup, reducing oscillation and vibration.
[img[Look Ma, No Hands!|./images/compact/strong.jpg]]

Here's a closeup of the temporary piston rod... Yes, another stack of 2x4 chunks! :)
[img[Temporary Installation 2|./images/compact/tempdrive2.jpg]]

The mouths of the three bags are fastened tightly to the ABS fitting with a hose clamp. The fitting is a "Y" type with a ridge at the bottom, so the clamp is securely in place.
[img[View From Above|./images/compact/top.jpg]]

For the "final version" of this cylinder, I will use Trash Compactor bags which are MUCH stronger... (also where I got the name ~CompactDrive :). I may also use a few industrial nylon ratchet-ties instead of a hose clamp to hold the bags onto the fitting. I will also use a 2" Male Pipe Thread to 2" pipe coupler passed through the top of the plywood piston and secured below; this will guard the bag somewhat at the interface to the piston, and more importantly, keep the bag from "balooning" out around the opening.
This is really the "standard / original" drive concept, namely to use a flexible bladder or a cylinder containing water or oil, and to allow the fluid to exit through an adjustable valve to produce the motion. The varieties of ~DripDrives I've been considering include WaterBellows, WaterCylinder, and RubberDrive types.
Here is one of today's epiphanies:

How about a friction-based drive system? It might be possible, with the right materials, to use something like brake shoes or pads and and adjustable pressure mechanism to modulate friction, allowing the platform to descend at a carefully controlled rate. Perhaps the pads could press against polished metal, or against a teflon coated surface. The smoothness of the surface would be important to keep the motion smooth.
Glory is the name I gave my 12.5" Dobsonian telescope when I built it.
I named it Glory because it has been my hope all along that everyone who looks through Glory would be able to see the glory of God as it is so wonderfully displayed in the heavens.
Picture a large block of wax. Now picture some hot knives criss-crossing the wax. Control the temperature of the knives, and you can control how fast they will melt through the wax. Use this to control the speed of descent of the McCrearyMount platform.
This is a "pseudo-fluid" variation of the DripDrives. Rather than using water, however, it uses sand or (perhaps even better) tiny glass beads.

The 64-dollar question is, of course, will this produce the ultimate smoothness of motion that the McCrearyMount demands?

''UPDATE:'' I received two pounds of glass spheres (one pound of 2mm spheres, and one pound of ~1mm spheres) the other day, samples courtesy of [[Potters Industries|http://www.pottersbeads.com/]]. This evening I did some very preliminary testing with them by pouring them through a plastic funnel into a glass.
[<img[Glass Beads|./images/glassbeads.gif]]
Do you have any idea how many 1mm glass spheres are in a pound? Neither do I, but it is an incredible number! I know because quite a few wound up all over the kitchen floor and counter!

In any case, my preliminary indication (this is a rather subjective impression) is that the motion of the glass spheres, at least in these sizes, is too "jerky" - almost a sense of quantization, or a ratcheting feeling. And so my guess is that this will NOT be a suitable drive. However, it may be possible that a wider cylinder would result in smoother motion. Further study and experimentation may be in order, but probably not at a high priority.
NOTE: These instructions cloned from tiddlywiki - updated to 2.0.7 on 5 April 2006.

The core TiddlyWiki code is regularly updated with bug fixes and	 new features. If you're using an earlier revision of TiddlyWiki, here's the simple way to upgrade to the latest version:
* Open your TiddlyWiki file in FireFox (say it's called "mystuff.html")
* SaveChanges (with SaveBackups switched on) to make sure that you've got a backup of it
* Without closing that page, right-click on [[this link|http://www.tiddlywiki.com/empty.html]], select 'Save target' or 'Save link' and save it as "mystuff.html", replacing your existing file
* Now go back to the previously opened copy of "mystuff.html" in your browser and SaveChanges again. It will inherit the newly saved code
* Refresh the page in the browser to verify that the upgrade has worked
The most likely cause of the upgrade process not working properly is that one of the [[Plugins]] you're using is not compatible with a change in the new release. If so, you can use the [[ImportTiddlersPlugin|http://www.tiddlytools.com/#ImportTiddlersPlugin]] from TiddlyTools to selectively import your content and [[Plugins]] into a new empty TiddlyWiki. 
Use a block of ice under the corner of the platform, and a hotplate. Control the rate of melt by adjusting the hotplate temperature.

This could come in two flavors, //wet// or //dry//.
Greetings, Friend! Welcome to the McCrearyMount Inventor's blog!

Please visit [[WhatsNew?]] for the latest news flashes, and check out my latest, "TheDickens," an ''RTMC 2012 Merit Award''-winning project.

A SPECIAL ''SHOUT-OUT'' to all who attended my presentation at the 2011 RTMC! Thanks for "showing up." :)

This is where I hope to record assorted thoughts and wild ideas about implementation details of the McCrearyMount as I continue to develop it.

I created the very first ever implementation of this invention, which I called the ProofOfConcept prototype, somewhere around the turn of the millenium. I am presently working on what I call the ProofOfWonderfulness prototype. This is also where you, gentle reader, can take part in the bleeding edge of development. ''//Your//'' [[comments and ideas|http://www.subarcsec.com/9912/index.html]] would be ''//most//'' welcome! If you check the "Timeline" in the right-hand column of this page, you can see what has been updated recently, or just visit [[WhatsNew?]] for the latest news.

''IMPORTANT NOTE:'' This is a "non-linear blog" powered by TiddlyWiki, and it may take a while to get used to navigating around. There is A LOT of "stuff" in here, so please experiment with clicking on various links to see how a TiddlyWiki works. :)
The Jug Drive is my initial test setup for the purpose of preliminary evaluation of the ProofOfWonderfulness prototype. The jug is a discarded shipping container from a medical saline solution. Similar flexible containers are readily available from many sources, typically vendors of camping equipment.
[img[Jug Drive|images/jugdrive.jpg]]
The Jug Drive may not be pretty, but it is functional and should provide some valid insights into how well the WaterBellows drive category works. I also hope to be able to do some star trail images with it to derive some actual data about the possible smoothness of motion with a bladder-type drive mechanism.
[[Odds and Ends]]
[img[McCreary Mount|./45528.jpg]]
^^TiddlyWiki <<version>>^^
The ~McCrearyMount is a new-technology equatorial platform for astronomical telescopes. It is a radical departure from prior art in this field in that, rather than attempting to compensate or correct for periodic error, it seeks rather to completely eliminate it at the source.

To read "the basics" about the ~McCreary Mount, visit [[subarcsec.com|http://subarcsec.com]].
Son Chris suggested this idea; use "memory metal" which changes its shape when an electric current is applied to it. Possible, with lots of questions:
*How much does it cost?
*Where to get it?
*How strong is it?
*Are there standard sizes and shapes?
*And etc.?
Settling on a "final version" of the drive mechanism is "driving" me crazy! This is conceptually one of the simple aspects of a McCrearyMount; however, as an implementation detail it is proving to be quite difficult to complete. So many options, so little time!

Here, in no particular order of preference, are some of my "conventional ideas" along with some of my "wild ideas" for drives... ''But, fair warning!'' These ideas range from the ridiculous to the sublime, and in some cases are here only to help keep the creative juices flowing! :) It is entirely up to you, dear reader, to discern among them, and to [[offer your feedback|http://www.subarcsec.com/9912/index.html]].

*Other Drives
I've added this new category to the main menu, because (now that I've discovered what may be the ideal solution to MotorMadness) it is past time to get serious about testing the real-world qualities of the McCrearyMount.

I am ''looking for help'' from any interested parties. If you have any knowledge or ideas about:
* Astrophotography
* Guiding, manual or electronic
* Star-trail photography
* Ways to measure tracking quality and precision
''//PLEASE//'' [[contact me|http://www.subarcsec.com/9912/index.html]] as soon as possible! Thanks! :)
!Various thoughts about materials and etc.

I'm waiting for a couple of one-pound samples of glass beads from [[Potters Industries Inc.|http://www.pottersbeads.com/]]. The idea is to see whether or not these might be suitable for use in some sort of HourGlassDrive.

I bought a disk of plastic material from an RV place. The guy there who sold it to me said (repeatedly, when I questioned him) that it is made of Teflon. The disk is used to replace grease where a 5th-Wheel hitch rests. Unfortunately, I have been unable to confirm for certain that it is Teflon, although it does look and feel like teflon.

Wood... Why wood? Wood is the simplest, strongest, least expensive and easy to work with material for prototyping this device. Future and other implementations may be made from other materials, but for now, wood is king.

BearingBalls are a key precision implementation element.
!Saturday, July 15, 2006 - Progress? In Recent Days...
I appreciate recent requests from interested folks wanting to know "What's been going on for the last month or so?". As usual, progress is much slower that I would like... In case any of you out there happen to be or know of anyone independently wealthy who would like to help fund further development of this invention, please let me know! :)

Here is a summary of recent progress:

After RTMC (see below), I signed up for several internet forums and mailing lists, and in the course of telling folks about my invention, I've taken quite a lot of heat! Some of it has been deserved, some not, but all of it has been thought provoking and I think will eventually be helpful as I work on this project. The major issues have been:
*Is there "prior art" that proves this is NOT an original invention?
*Have I proven my claims of accuracy?
*Can a fluid drive be made precise and smooth enough to meet my objectives?
On the first issue, many long-time ~ATMs (Amateur Telescope Makers) jumped in to say that they had seen designs like mine in the past. I asked for help to locate information about any such designs, as it has always been my intent and practice to provide "credit where credit due". Some very helpful folks actually did locate and send me copies of photos and articles showing what were indeed some very similar developments in times past. Unfortunately, I am afraid that many on the forums went away after simply concluding that I have nothing original. However, one very kind soul out there (Don Good - Thanks, Don!) came to my defense in pointing out that an invention is the complete sum of ALL of its parts, and that the ~McCreary Mount incorporates a polar axis design that is original to the best of his (Don's) knowledge. No one came back to refute that. Quoting from Don, who said it perhaps better than I have been able to say it so far:
"In particular, I have not seen a polar alignment mechanism on
a portable equatorial mount, platform or standard, with such fine
alignment control.  I would truly like to know if something of similar
fineness exists?  And it is true that any rotation around and in
contact with the surface of two spheres on the great circles (condition
guaranteed by this geometry), is a rotation around the line between
the centers. This has higher accuracy than a solid axel thru bearings
because it depends only on the accuracy or the two balls instead of
all the balls in the ball bearings and the roundness and straightness
of the axel." - (Don Good to ATM mailing list on 14 June 2006)
I really appreciated those comments! And also, to date anyway, no one has come forward claiming prior use of this kind of polar axis design.

On the issue of claims of high accuracy, my licks were probably well deserved. While I have been very enthusiastic about the POSSIBILITY of very high accuracy inherent in this design, I have not yet proven that accuracy by measurement. Part of my "quietness" lately has been in response to that; I will probably be much quieter about this invention for a while until I am able to actually make objective measurements to prove the design.

Finally, the question of whether or not a fluid drive can be made to function smoothly enough to demonstrate such accuracy was raised quite forcefully. The consensus seemed to be that there are insurmountable difficulties with that, and my protestations to the contrary seemed to be largely ignored. Well, the good result of that verbal thrashing is that I now have thought of an additional approach to solving those problems, and I'll tell you more about that after I get a little further down the development and testing road.
!Star Party Platform Development
One other good result has come out of my bashing on the forums: I've begun to design and build another version of the ~McCreary Mount - one that I call a "Star Party Quality" platform. It has occurred to me that there are perhaps a large number of people out there who would love to have a simple, quick and easy to build, inexpensive equatorial platform on which to place their mid to large size Dobsonian telescope. The main requirement for this design is to be transportable, easy to set up and align, and to keep some beautiful instance of God's celstial handiwork in the field of view for fifteen or twenty minutes, long enough for a "star party" group of observers to each have a chance at the eyepiece. In other words, not necessarily for photography or ultimate precision, just for good, plain visual observing fun.

And so, here I will tell you about the simple but useful "Star Party" design I've been working on.

Here's a view of the platform base. Most if not all construction will be of 2x3s:
[img[StarParty Platform|./images_starparty/planbase.jpg]]
Note that where two of the structural members abut each other, there are hinges underneath that allow the assembly to fold. When unfolded, there are three "feet" that support the base at three widely spaced points. I have cut out the pieces for the base, but have not yet assembled them.

Here's a view of the movable part of the platform:
[img[StarParty Platform|./images_starparty/planplat.jpg]]
This part also folds, and the circles illustrate the range within which the telescope rocker box rotates when it is on the platform.

I have so far cut and built the triangular portion of the platform, seen here resting on what I call a "two-tube" drive mechanism.
[img[StarParty Platform|./images_starparty/plattubes.jpg]]
Water in one tube is driven into the other tube as the platform tracks, after which you simply lift the corner of the platform and swap tubes for another fifteen or twenty minutes of operation.

The rate of water flow is regulated by this very simple valve, made from a door hinge and the interconnecting tube itself:
[img[StarParty Platform|./images_starparty/valve.jpg]]

The platform is of course quite strong by design, here I am standing on it in the "open" position with the corners supported on blocks:
[img[StarParty Platform|./images_starparty/strong.jpg]]

No locks or bolts are needed to hold it open; it stops in the full open position, but then when lifted up it easily folds again on the hinges:
[img[StarParty Platform|./images_starparty/folding.jpg]]

Valve stems are removed from the tubes and a vinyl tube is hose-clamped on the valve:
[img[StarParty Platform|./images_starparty/connection.jpg]]
A piece of foam pipe insulation is used to cover the hose clamps and prevent sharp edges from puncturing the tubes.

The tubes are relatively small and can be stacked to put them away:
[img[StarParty Platform|./images_starparty/tubestack.jpg]]

The Star Party Platform should cost about $75 if you buy all new materials, or considerably less if you scrounge or have things "on-hand". If you have an electric mitre saw, drill, and average skills, I would be surprised if it took you longer than a weekend to build completely and put into use. I've been drafting some plans and intend to put the whole thing together into a PDF file that I will give away on the condition that it not be modified, i.e. that people who look at or use the plans will always be able to get back to the main website where more serious developments are in progress, or be able to "send a donation" if they so desire. The whole package folds so that it should fit into the back of most cars.

Work that remains on the Star Party Platform is to assemble the base and to finish calculating the lengths and shapes of, and to cut out, the assorted pieces needed for the North support of the polar axis for both the base and the movable platform. I hope that my next update on the blog will have a report of a completed and tested platform for your enjoyment, and that perhaps the next after that will announce the availability of plans so that anyone will be able to build one of these. Stay tuned! :)
!Thursday, June 1, 2006 - "How-To" Booklet In The Works
Due to frequent and repeated requests from many at the RTMC show, I've decided to make a "~How-To" booklet available to those who have decided to build a McCrearyMount.

The booklet will contain many of my notes and prototype construction photographs, as well as parts lists and sources, spreadsheets for various design calculations, and many other "extras".

For details on how you can download yours, please [[Click Here|http://www.subarcsec.com/9955/index.html]].
!Tuesday, May 30, 2006 - RTMC Overview Report!
[<img[The McCreary Mount at RTMC|./images_rtmc/compdrive.jpg]]

I arrived back home from the [[Riverside Telescope Makers Conference|http://www.rtmcastronomyexpo.org]] yesterday afternoon. The conference was an utter delight! I found myself frequently saying to others things like, "I'm having WAY too much fun!", or "I'm having more fun than a human being should be allowed to have!" :)

The number of attendees was astounding to me. Somewhere between two and three thousand people showed up from all over the country. I was told that this unusually high attendance was partly due to the fact that Memorial Day Weekend this year coincided with new moon, resulting in the darker skies best suited for astronomy.

For complete details of my time and the events at this year's Riverside Telescope Makers Conference, click on RTMC2006, but here is the executive summary:
*I met many friends at RTMC, both old and new.
*The ~McCreary Mount, which was fully assembled and operating for the first time ever, worked reasonably well in spite of some remaining technical problems.
*Dozens of people actually visited and saw my invention.
*The response was overwhelmingly positive!
*As I hoped, many who saw what I've done had good questions, ideas, and suggestions for improvements.
*Perhaps half a dozen or so looked through the eyepiece when the mount was operating on Friday and Saturday nights.
*I had the priviledge of presenting a "mini-sermon" at morning worship in the Camp Oakes beautiful open-air chapel.
*My presentation went very well, and I was able to share with the 60 to 100 listeners my personal recognition that the universe we astronomers all enjoy viewing came from God's hand.
*At least two of the attendees plan to build ~McCreary Mounts!
*Throughout the conference I had a strong personal sense that the Lord was directing my every step, and brought exactly the right people into contact with me. Thank You, Lord!

For my complete conference report (with lots of photos), check out RTMC2006.

!Tuesday, May 23, 2006
Getting close to ShowTime! :) Today I finished assembling the CompactDrive and plumbed it up to the 12V pump. It almost kinda sorta works! :)
[<img[Compact Motion|./images/compact.gif]]

If you look closely as it moves, you can see the CompactDrive cylinder changing angles as the platform descends. I had some trouble initially with the bags "slipping by" the piston, but after using the pump once or twice to refill, I didn't see them any more.

Motion overall seemed smoother than in my earlier test. I still want to move on to a rolling diaphram ( WaterBellows) drive, but this should at least be something that I can demonstrate at RTMC. Now if I can only get the rest of the details done before Friday AM rolls around! 

!Saturday, May 13, 2006
Finished construction and began testing of the CompactDrive today! Here are the three major parts of the complete system: the base, the platform, and the compact drive.
[img[Three Major Parts|./images/compact1/threeparts.jpg]]
Here's the Compact Drive all plumbed up and ready to install.
[img[Compact Drive|./images/compact1/cd1.jpg]]
You can see how strong this thing is!
[img[Strong Platform!|./images/compact1/strong.jpg]]
Here are a couple of photos with the scope in place and the drive tracking:
Now for the not-so-good news...

On the first preliminary tests, it does not work as well as I had hoped, at least by my initial observations. The bag began to creep by the side of the piston. There is some "creaking" as the platform descends, indicating that there may be some sticking which clearly will affect motion. The flow was irregular. I think I have achieved overkill in my cylinder diameter; my intention was to have a widely adustable flow, but I wound up with too low a pressure; I think I need to find a "happy medium" somewhere.

My conclusion is that I want to build a WaterBellows as soon as possible, although that is almost certain not to be before RTMC.

Before giving up completely on the ~CompactDrive, I will do some more "fine tuning" and experimenting. It may work better with three bags (at least with respect to "creep by.")

!Monday, May 01, 2006
Made some actual construction progress today. Here's a sketch of the CompactDrive cylinder that I'm using to work out cylinder dimension details and to see how the cylinder will fit into the platform.
[img[Compact Drive Sketch|./images/compact/cd_dwg.jpg]]
I built a "dummy cylinder" to see how it would change length and angle as the platform moves. The bearing arrangement is identical to the main mount bearings in order to take advantage of the grade 24 ball precision. The Compact Drive is a straight telescoping low pressure cylinder. By mounting each end with a bearing ball, the length of the cylinder can change as needed and the endpoints will follow their respective paths while changing angles as needed.
[img[Lower Cylinder Bearing|./images/compact/cd_bearing.jpg]]
I used some rubber bands as a "virtual cylinder" to visualize the change in length and angle    that the cylinder must follow.
[img[Checking Alignment|./images/compact/cd_align.jpg]]
Pam picked up the trash compactor bags that I needed for me today. These are 2.5mil white 18 gallon bags... about the right size, and more than twice as thick as the last CompactDrive experiment.
[img[Compactor Bags|./images/compact/bags.jpg]]
The support for the lower cylinder bearing ball is in place, subject to final evaluation when I finish the CompactDrive cylinder itself.
[img[Lower Cylinder Bearing Balls and Mount|./images/compact/lower_cyl_ball.jpg]]
I also made progress on other aspects of construction.The chrome grade 24 bearing balls arrived today from Small Parts.
[img[New Upper Bearing Ball|./images/upper_ball.jpg]]
I improved the upper platform bearing support:
[img[Upper Bearing Support|./images/new_upper.jpg]]
I put a new ball in the lower bearing as well.
[img[Lower Bearing Ball|./images/lower_ball.jpg]]
I have been wanting to stiffen the north pier of the base to reduce sway and vibration, and so I cut out, glued, and screwed in two inner braces to help do that.
[img[First of Two Inner Braces|./images/inner_brace1.jpg]]
[img[Second of Two Inner Braces|./images/inner_brace2.jpg]]
I also made new ball supports for both ends of the CompactDrive cylinder, and a new support for the north platform corner.
[img[New Bearing Ball Supports|./images/ball_supports.jpg]]
!Saturday, April 29, 2006
A busy day! Also very frustrating, spending hours combing through the plumbing fitting bins at Home Depot trying to fit just the right fittings together!

It was, however, very rewarding because my second experiment with the TrashBagDrive concept was quite successful! After spending a couple of weeks apologizing for the name, I had another insight today and will re-name it the CompactDrive -- click on that and you can read about todays tests and see photos.
!Thursday, April 27, 2006
Well, they changed the presentation schedule at RTMC -- meaning that I won't give my presentation at 1:30PM on Sunday, but rather at 3:30PM. :( Which means that my good friend Gene will not be able to stay for it. :(

In other news, the Marsh Bellofram company wants $500 (!!!) for three samples of the diaphram that I would like to test for the mount! On the brighter side, my friend Roger located a bunch of alternate (other than BelloFram) sources for rolling diaphrams, which is good news. Here's a cool animation from one of those sources:
[<img[Rolling Diaphram|./images/dia-ani.gif]]
By the way, the 1" grade 24 Chrome bearing balls have been ordered from [[Small Parts|http://smallparts.com/]].
!Friday, April 14, 2006
Yesterday I visited my friends at [[Cladan Corporation|http://www.cladancorp.com/]] for a tour of their new facility. This was quite entertaining in its own right; however, I picked up an ''//exciting//'' bit of information about what may become the ideal solution to my MotorMadness struggles!
Ken at Cladan told me about a device that I had previously envisioned (see what I have been calling the RubberDrive) that already exists in a commercialized form! It is called a "rolling diaphram" and you can read more about it here -> BelloFram.
!Wednesday, April 12, 2006
The BIG news for today is that I have been accepted to present my paper about the McCrearyMount at this year's Riverside Telescope Maker's Conference! Hallelujah! :) My presentation is scheduled for 1:30 PM on Sunday, May 28th. You are most cordially invited to attend! :)
!Saturday, April 08, 2006
Check out today's experiments on the TrashBagDrive! The summary statement is, this looks like it could work well and be built readily by a home-builder. Drawbacks would be: lack of durability (however easy to replace the bags), and a general "kludginess"... but hard to beat for simplicity, readily available materials, inexpensiveness, and home-buildability.
|Author|Eric Shulman|
|Description|Embed a media player in a tiddler|
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''If you use [[AttachFilePlugin]] to encode and store a media file within your document, you can play embedded media content by using the title of the //attachment tiddler//'' as a parameter in place of the usual reference to an external URL.  When playing an attached media content, you should always explicitly specify the media type parameter, because the name used for the attachment tiddler may not contain a known file extension from which a default media type can be readily determined.
Default player size:
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+++[Windows Media]...
Times Square Live Webcam
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Asteroids arcade game
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YouTube Video
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+++[Still Images]...
GIF (best for illustrations, animations, diagrams, etc.)
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JPG (best for photographs, scanned images, etc.)
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2008.05.10 [1.1.4] in handlers(), immediately return if no params (prevents error in macro).  Also, refactored auto-detect code to make type mapping configurable.
2007.10.15 [1.1.3] in loadURL(), add recognition for .PNG (still image), fallback to iframe for unrecognized media types
2007.08.31 [1.1.2] added 'click-through' link for JPG/GIF images
2007.06.21 [1.1.1] changed "hidecontrols" param to "showcontrols" and recognize true/false values in addition to 'showcontrols', added "autoplay" param (also recognize true/false values), allow "auto" as value for type param
2007.05.22 [1.1.0] added support for type=="iframe" (displays src URL in an IFRAME)
2006.12.06 [1.0.1] in handler(), corrected check for config.macros.attach (instead of config.macros.attach.getAttachment) so that player plugin will work when AttachFilePlugin is NOT installed.  (Thanks to Phillip Ehses for bug report)
2006.11.30 [1.0.0] support embedded media content using getAttachment() API defined by AttachFilePlugin or AttachFilePluginFormatters.  Also added support for 'image' type to render JPG/GIF still images
2006.02.26 [0.7.0] major re-write.  handles default params better.  create/recreate player objects via loadURL() API for use with interactive forms and scripts.
2006.01.27 [0.6.0] added support for 'extra' macro params to pass through to object parameters
2006.01.19 [0.5.0] Initial ALPHA release
2005.12.23 [0.0.0] Started
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The ~PlungerDrive was the original hydraulic motor for my ProofOfConcept prototype.

[<img[Plunger Drive|images/plungerdrive.jpg]]

I used a plunger very similar to these commonly available plastic ones. The proof of concept prototype enabled [[Glory]] to stay on track at star parties for fifteen minutes or more.
The original proof of concept prototype was thrown together and tested with an unmodified Dobsonian style telescope. It used the PlungerDrive for motion.

Note that the bearings on the original proof of concept were sharpened bolts.
The platform was supported on cones that rested on those two points.
Here is the upper hinge assembly.
[img[Upper Hinge Assembly|images/uhinge.jpg]]
Here is the lower hinge assembly.
[img[Lower Hinge Assembly|images/lhinge.jpg]]
The PlungerDrive was inserted into a couple of specially shaped holes/brackets.
[img[Plunger Drive Holder|images/drivesocket.jpg]]
Here is the Proof of Concept Prototype base.
[img[Proof of Concept Prototype Base|images/pocbase.jpg]]
Here is the platform resting on the base.
[img[Proof of Concept Prototype Platform|images/pocproto.jpg]]
Here is an animated illustration of the prototype moving.
[img[Proof of Concept|images/pocmoving.gif]]
The ~ProofOfWonderfulness prototype is the prototype that I am presently working on. I hope that this prototype, more fully described with photographs at [[http://subarcsec.com|http://subarcsec.com]], will prove that this design is capable of exceeding the best efforts previously made with other designs in terms of smoothness of operation and suitablility for astrophotography.

About five or six years ago, I built a ProofOfConcept prototype that worked but was not intended to prove the full extent of the ultimate capabilities of this invention.
!Friday, May 26, 2006 - Arriving at RTMC and Setting Up
After leaving home at the crack of doom, I got to the conference early Friday morning and was able to secure a space close to my dear old friend Gene Cross. My friendship with Gene goes back to the mid-eighties. Gene is the one who introduced me to RTMC to begin with. Thanks, Gene!
[<img[Houston: The McCreary Mount Has Landed! :)|./images_rtmc/level.jpg]]
Another "neighbor" already there, Jim, was very kind to me throughout the conference. For example, Jim loaned me a shovel to level a spot for my platform. On Saturday he also came and dragged me away so that I would be able to sign up in time for the judging.
Jim tells me that he built a German equatorial mount for a large telescope owned by his club. Jim, if you're reading this, please send me those photos! :) And thanks for your help and encouragement at RTMC!

[>img[Initial Setup at RTMC|./images_rtmc/jugdrive.jpg]]
At first I set up the platform with the JugDrive, thinking I would use that because of my misgivings about the current "state of the art" of my CompactDrive.

Yes, that IS a hearse you see in the background. I guess it always pays to be prepared. :)

[<img[Final Setup at RTMC|./images_rtmc/compdrive.jpg]]

Then perhaps because of platform stability concerns,  I swapped out the JugDrive with the CompactDrive, and started to prepare for Friday evening.

Note the weights (borrowed from son Chris) on the west end of the platform. These were to compensate somewhat for an unexpected engineering result. I deliberately built the CompactDrive cylinder with a large diameter (~12"!) thinking that with the large diameter I would have a relatively large fluid flow per unit-time as the platform tracks. While this is true, the unintended consequence is that the cylinder pressure is miniscule ( about .7 PSI) which results in a less than reliable flow out through the regulating drip valves.

[>img[Drive Training Whisker|./images_rtmc/whisker.jpg]]
I wanted to begin to "tune in" the motion of the drive before I wound up stumbling around completely in the dark, and then I had the inspiration to tape a "whisker" - one of those plastic-coated metal twist-ties that I had kicking around in my toolbox - to the front rim of my telescope tube to cast a shadow that might let me use the motion of the sun for an initial "ballpark" calibration.

I stuck a small piece of duct tape on top of the tube support box and drew a '+' target on it. Then I pointed [Glory] towards the sun (don't worry! The mirror was not yet installed, and the tube was still covered with its compactor bag dustcover!).

The whisker cast a shadow on the top of the tube box,

[<img[Training Target|./images_rtmc/target.jpg]]

and I adjusted it until the tip of the shadow was pointing directly to the center of the target. With my friend John's help, I then fiddled with the plumbing and the weights and the rough aim of the platform in order to achieve an "approximate tracking rate" that I expected to be able to easily refine later on after dark with stars to guide me.

This ad-hoc system worked fairly well, and I'm sure it saved me problems later on. Due to the fact that I had been working madly to prepare everything for the conference, and had thrown all my equipment into Pam's van at the very last minute in order to get there on time, this was actually the very first time ever that I had the platform with all it's associated CompactDrive and plumbing "fully up" and working!

[>img[John, Dann, and Gene|./images_rtmc/friends.jpg]]
Here's a "happy snap" of John and myself and Gene standing by the completed and initially calibrated setup.

[<img[First Light on Friday Night|./images_rtmc/firstlight.jpg]]

After dark Friday evening, it was time for "first light" of the fully-assembled McCreary Mount. My friend Rick provided considerable help and assistance as I fiddled with various variables.

It soon became apparent that the tracking was too slow, implying that less water was flowing out of the CompactDrive cylinder than required. I already had two drip irrigation valves installed in the circuit, and they were both cranked "wide open" to the point that the valve poppets were on the verge of falling out.

Rick suggested that I bore a hole in the vinyl tubing to provide an additional constant flow that could then be further adjusted with the existing valves. It actually took two holes, but the idea worked beautifully. Thanks, Rick! :)

!Saturday Visitors and Events
I had created a poster presentation so that people walking by could get some idea of what the invention is about whether or not I happened to be in camp at the moment. I also placed some historical artifacts from the development of the proof-of-concept prototype on the table.
[img[Poster Presentation|./images_rtmc/poster.jpg]]
The weekend was outrageously windy, with dust blowing into everything, and so I had to seriously anchor the poster down, and even weight the table legs using some rather large rocks found in the vicinity!

Judging of the award entrants took place before noon on Saturday. If my neighbor Jim hadn't mothered me to be sure that I entered, I would have missed it! Thanks, Jim! :)
[img[Illustrating the Inherent Strength of the McCreary Mount for the Judges|./images_rtmc/judging.jpg]]
In this picture, you can see me standing on the McCrearyMount as a way of illustrating for the benefit of the judging committee just how inherently strong and stable this design is. I must confess that, after all was said and done, I was a little disappointed not to have won any awards this year.

However, one of the things that I have hoped for as a result of releasing my invention into the public domain has definitely begun to happen. Saturday afternoon, a gentleman named Dave stopped by and offered the excellent suggestion of the possibility of using something like a peristaltic pump on the outlet side of the relaxation drive cylinder to accurately and variably regulate the rate of flow, thus resulting in perhaps more precise tracking. Dave, are you reading this? Thanks! Please drop me a line! :)

[<img[Mike's Fabulous 20" Ball-Base Scope|./images_rtmc/ballscope.jpg]]
Mike, another neighbor of mine on the other side of Telescope Alley, brought this beautiful and very innovative telescope with him. It is a ball mounted scope with a 20 inch mirror that he ground and figured. The transparent plastic base is an industrial light fixture cover that Mike bought off the shelf for $250. His mirror is permanently mounted inside the ball in a flotation cell that cannot be aimed, and so all of his collimation is done with the apparatus that he built to support the focuser and secondary mirror. When dismantled, he whole thing fits neatly in the back of his compact car!

On Saturday evening, Mike treated me to a lovely view of the trio of galaxies in Leo, all in one field of view. His optics are superb! He told me that in order to be able to accurately figure the 20" mirror, he had to suspend his pitch lap from the ceiling with bungee cords to reduce the pressure between the lap and the mirror! While mike didn't win an award this year either, his design and implementation are certainly winners in my book. Beautiful job, Mike! :)

!Saturday Night Freeze

Sunday morning was a tremendous blessing! I woke considerably earlier than I had originally intended, and found myself thinking about the coming day and my upcoming presentation that afternoon. I had originally been a little disappointed that I had not been given the Saturday afternoon speaker's time slot that I requested in my application to speak. However, while meditating and praying, that morning, I realized that it was indeed a blessing for me to be assigned to speak on Sunday, because as Sunday is widely recognized as the Lord's Day, I might have some additional boldness to clearly and unequivocally be a witness to Jesus as the creator of the beautiful and unimaginably grand creation that we as astronomers all observe and stand in awe of. Well, as they say on the infomercials, "But wait! There's more!"

[>img[The Lines, Large and Small, Froze Overnight|./images_rtmc/frozen!.jpg]]

As I was sure that it had frozen overnight, I rose and went with some anticipation over to the prototype, hoping that I might find a skin of ice on the reservoir bucket to photograph for my scrapbook.

I was a little disappointed when I looked into the bucket not to see any ice. I dipped my finger in just in case the shadows might be hiding it, but - nope - no ice, and so I turned away towards other tasks. Then it struck me; the bucket probably didn't freeze because of the thermal mass of the large volume of water it contained. This was actually somewhat comforting, because the CompactDrive would then also likely be intact as well, not damaged by any ice.

It occurred to me that perhaps the small-gauge vinyl tubing in the drip circuit may have frozen!
[<img[Sunday Morning an Icicle Hangs from the Drip Valve!|./images_rtmc/icicle.jpg]]
I turned back to the prototype, and, sure enough! It had! While I happily began to take some photos of the frozen line, John said "Look! The refill line is frozen too!" Sure enough, the 3/4" vinyl refill line that I use to pump water back into the CompactDrive for resetting the platform was frozen solid! Looking closer, there was even an icicle hanging from one of the drip valves!

Although this circumstance was completely unforseen, it was kind of a treat for me to be able to take these photos for my scrapbook, and no harm done to the mechanism. :)

!Sunday Morning - Breakfast, Then Worship
As these events were transpiring, along with a general good humor, a small bearded man stopped by and was looking on. As it turned out, this was Dave, a Christian shepherd who was scheduled to lead the coming 9:00 AM worship service in Camp Oakes beautiful open air chapel. We spoke briefly, and I asked if there might be an opportunity for me to testify at that service, which he graciously granted.

[>img[Breakfast Sunday Morning|./images_rtmc/breakfast.jpg]]
I decided to walk over to the dining hall with John. During my time with him, he told me about his work with Dolby Sytems and offered me some recommendations for several software packages that I need to use in my work. At breakfast we also discussed the advantages of locating "genuine" Chinese restaurants and the superiority of the ethnic cuisine available there. "Accidentally" John Gregory sat down at the table right next to me. As it turned out, John was the speaker that Gene Cross had highly recommended to me earlier. His presentation later in the day was outstanding and very encouraging. He is also an aviation enthusiast; he flys a Bonanaza and is building what he calls his "project", a KR-2 aircraft.

John is also building a 41" telescope on an Alt-Azimuth mount. I asked him if he had any desire to do astrophotography with it, and when he allowed that he did, I suggested he put it on a McCreary Mount. His knee-jerk reaction was that he didn't think an equatorial mount could handle the weight. When I inquired as to his estimated system weight, he said "Three thousand pounds." Smilingly, I told him of my belief that my mount design, when properly scaled, might likely be able to support an instrument package of 20 to 30 tons! :) This was enough to persuade him to attend my lecture later that afternoon.

[>img[Worship On Sunday Morning|./images_rtmc/chapel.jpg]]
Worship in the open air chapel at Camp Oakes was a great blessing. There was a congregation of perhaps 30 or 40 believers present. Don Hunt opened the meeting with some observations about the likely diversity of Christian traditions that were present there, but emphasized our common brotherhood in Christ Jesus.

[<img[Shepherd Dave Holding Forth the Word of Life!|./images_rtmc/shepherddave.jpg]]

Shepherd Dave then shared a powerfully encouraging message from the Word of God, reading from old and new testament books.  Later on, he also read us a passage written long ago by St. Augustine. Dave told us that God has abundantly provided for us as His people a "toolbox" -- the Word of God -- containing everything that we need both for repair and maintainence and also for the encouragement and direction we need to move forward in our lives as we seek to better serve Him and draw nearer to Him. I found myself shedding tears of joy in my sense of God's particular blessing and kindness to me to allow me to be at the conference and be His witness in the world.

[>img[Don Hunt Shares His Life Story|./images_rtmc/don.jpg]]

After his message, Dave invited Don back to speak. Don told us how his life was a series of going back and forth towards and away from God. He was present (but unhurt) during the massive Alaskan earthquake in the sixties, and felt that God was by that reminding Don to return to Him. His story illustrated God's patience and persistance in seeking and finding His lost Sheep.

After Don spoke, I had the tremendous privilege and blessing of being able to stand before the congregation and present a brief extemporaneous message from Scripture. I shared some of my favorite scriptures, including Proverbs 16:9 which says "A man plans his way, but the Lord directs his steps" and I told those gathered how I had felt perhaps as strongly as ever in my life God's hand guiding me through the weekend at every turn, with each personal meeting, and in all the events. I shared a brief outline of the story of Jesus and Lazarus, at which time Jesus told those with Him, "If you believe, you will see the Glory of God". I expressed my desire that, during the presentation of my invention to the conference that afternoon, I might clearly speak to God's glory and that at least some of those who would hear and perhaps later use my new technology, might through it also "see the Glory of God" in the heavens.

After the service, a group of brothers and sisters gathered around me and lifted me up in prayer for my request to be a good and bold witness in my presentation. Those prayers were answered that afternoon. :)

!Presentations and Visitors

[>img[John Gregory Presenting|./images_rtmc/john_gregory.jpg]]
I attended John Gregory's presentation entitled "My 60 Years of ~Astro-Optics" at 10 AM. and was very glad that I did. He presented an incredible series of photos, diagrams, and descriptions of various optical technologies that he had both used and participated in the design of during the course of his career.

I found John's presentation both interesting and informative, and also for me very personally encouraging as I saw instance after instance where innovative thinking had either made some optical system better than ever before, or in some cases even made possible tasks that had previously been unattainable.

[<img[Dann McCreary Presenting|./images_rtmc/dann_mccreary.jpg]]
Later that afternoon it was my turn to present "The ~McCreary Mount - A New Technology Equatorial Platform". After what my friend and brother Tony described as a somewhat nervous start, I settled in and was able to tell my audience exactly what a ~McCreary Mount is, how it is better than prior art, and why I believe that it could become the mount of choice for serious astrophotography.

I also spoke of my hopes that this design could become to telescope mounts what John Dobson's marvelous design has become to telescopes. It is my hope and my express desire that through the use of this new technology, many will have an ever greater opportunity to personally see the Glory of God in the heavens that He created through Jesus Christ.

After the talk, folks came up to ask questions or to thank me for the talk. Half a dozen or so then walked out to Telescope Alley with me to see the actual prototype. While out there, additional discussion ensued. I barely had time after that to get ready for and head down to the 6:30 PM Awards Presentation.

[>img[Outside the Hall for the Awards Ceremony|./images_rtmc/awards.jpg]]
The last meeting of the conference was the Awards Ceremony on Sunday evening. Here you can see a photo of the hall, and some of the people outside. The dining hall does have adequate capacity for an event like this, and so crowds gather both in front and behind the hall in eager anticipation of the door prize drawing. At the Saturday night gathering, based on a count of distributed door-prize tickets, there were nearly 1000 people present!

!Heading For Home
[>img[How'd You Get All That Stuff In There?|./images_rtmc/homegoing.jpg]]
By the time the last meeting was over, I was pretty tired and really wanted to head for home. However, I realized that trying to pack everything up in the dark was beyond my present state of mind so I spent another night and packed in the morning.

As you can see in this photo, the mount is much more bulky and unwieldy than your average bear. That is partly intentional due to the large geometries involved which give it strength and stability. I do believe that considerably more compact versions are possible. George, one of the RTMC attendees who heard my presentation came up and looked at the prototype. He told me that it is exactly the concept he has been looking for to support his astrophotography aspirations. George presently uses a very old Beyers German equatorial mount, which he has been unable to adjust to give satisfactory performance for photography. As a retiree, George can't afford one of the more expensive but accurate mounts like an Astro Physics or Takahashi.

George says he intends to design a folding version of the McCrearyMount that he will be able to easily take to dark sky locations. He's a CAD designer, and has promised to send me a copy of the plans when they are done. Thanks, George!

This is a rather attractive concept that combines aspects of the WaterCylinder and the WaterBellows into one. The idea came from a novelty toy that can be found in "science" or "nature" kinds of stores. The toy, sometimes called a "water wiggler", is a rubber or plastic cylinder that is nearly impossible to pick up, because it is actually (topologically speaking) a torus with a thin rubber (read "balloon-like") skin and a fluid center. When you try to pick it up, the weight of the fluid causes the torroidal skin to simply wrap around on itself and the whole thing exits your grasp.
[img[Water Wiggler|./images/dolphinwaterwiggler.gif]]
[img[Water Wiggler|./images/wiggler.gif]]
Now to make a drive out of it; Picture a rigid container that is essentially a curved cylinder just like one of the WaterCylinder design ideas. This container is analogous to your hand around the novelty toy. Now picture a piston resting on top of the bladder. The space between the edge of the piston and the cylinder is just wide enough for the rubber bladder to double up on itself, like the torroidal novelty toy, and as the water exits the bladder, the walls of the bladder slide by one another smoothly.

''NEWSFLASH!'' This device already exists as a commercially available product! See BelloFram!
This is a very special "hello" to all of you who attended my presentation at RTMC 2011 over Memorial Day weekend. Your presence, your laughter, applause, and your comments were all very encouraging! THANK YOU! :)

You asked some excellent questions, and many of you stayed after the talk to look over the one simple prototype that I had out in front of the dining hall and to "kick the tires," so to speak.

While I hope that I was able to satisfy your curiosity and answer your questions while we were there together, please know that I am available to answer any additional questions you may have. You can reach me at:  ''"subarcsec at sub arcsec dot com"'' (just "translate" that into a "standard" email address... :)

I am of course particularly interested in seeing one of my designs adopted by an observatory project. As I said in my talk, I believe that any group who may be embarking on the construction of a multi-ton instrument could potentially save time, effort, and more importantly, money in quantities of perhaps hundreds of thousands of dollars by using a Virtual Polar Axis in their design.

Why not save that expense and apply the savings instead to your primary optical instrument? :)

If you want to review the talk I gave, or share it with your club or with a friend, please follow the links from the [[WhatsNew?]] section.
some thoughts and wild ideas
Inventor's Blog
The ~SugarDrive is another tongue-in-cheek (pun intended) drive idea that is a little bit like the IceDrive concept.

Create a support column of some material that can be dissolved (like, for instance, sugar). Apply a suitable solvent (e.g. water) to one end to cause it to dissolve at a controlled rate.

Viola! Motion!
Like the BlockAndTackle, this is another "suspension drive". Hang the corner of the platform from a thick strand of stretchy material, like taffy. Let the taffy pull, perhaps using humidity or temperature to control the rate at which it stretches.
The Tangent Problem occurs when you use a linear actuator to move something that is rotating around an axis. The problem is, if you move the actuator at a constant rate, the rotational speed around the axis will vary.

In a McCrearyMount this is not likely to be a large problem, mainly because in order to achive the highest accuracy theoretically possible, motion needs to be controlled in a closed-loop that actually "guides" on a celestial object. This is necessitated in long exposures by the refractive effects of the atmosphere.

Not a problem if you're on the moon or other atmosphere-free environment. :)
I have named this project "The Dickens" because some folk upon first catching sight of it have been known to exclaim "What the Dickens is that?"

[<img[The Dickens|./thedickens/DickensRTMC.jpg]]

In past years at RTMC, I've entered McCrearyMount prototypes but have not won any awards. Contemplating this situation, I came to the conclusion that the judges there weight their judging substantially in favor of beauty and craftsmanship. Well, in past years I've simply tried to introduce what I consider to be some radically beneficial concepts, such as what I now call the "Ideal Polar Axis." However, with prototypes made of 2x4s, I think it has been hard for people to "see" and appreciate the fundamental ideas.

This year, rather than "fighting city hall," I decided to try to make my entry beautiful as well as functional in the hope of drawing people's attention to the underlying design benefits of the McCrearyMount.

You can also watch ''//this short video://'' [[(courtesy of Animoto)|http://animoto.com/play/5MSS10TjTpHb01xxuwL2BQ]]

This is a "non-linear blog" powered by a really neat piece of software called TiddlyWiki. It may take you a bit to get used to navigating around.  If you find yourself struggling with the format and have any specific questions about how links and etc. work, please visit http://tiddlywiki.com/ where you can learn more.
The ~TrashBagDrive is very very similar to the RubberDrive. The idea is to take a very thin membrane, like a trashbag, and attach it to a piston with a hole in the top. Seal the trashbag all the way around the piston and put the whole thing into a cylinder. Fill the trashbag with water, bleed out all the air, and plug the fill hole but leave a hose and valve arrangement for water to exit through.

With the weight of the telescope and platform on this arrangement, there should not be any problem with leaking as in a WaterCylinder drive. As the water exits, the trash bag should simple "crumple", perhaps somewhat irregularly, but I think smoothly enough to provide a very fluid motion.

Here are some photos from today's experiments:

[img[Raw Materials|./images/rawmtls.jpg]]
Some of the "raw materials" used in this high-tech production!

[img[Plywood and Foam Piston|./images/piston.jpg]]
Here are the cut out circles of plywood and foam for the piston.

[img[Exploded View of TrashBagDrive|./images/exploded.jpg]]
Here is an "exploded view" of the drive. The "piston" is a plywood disk slightly smaller than the cylinder, with a slightly larger piece of foam plastic on the bottom side against the trashbags. The cylinder has one closed end. The mouths of the two bags (one inside the other for strength/leak backup) were pulled through the hole in the piston. For my tests, I simply filled the bag with water from a hose, twisted the outlet of the bag to control the outward flow, and let the water drip out onto the driveway.

[img[TrashBagDrive Guts|./images/guts.jpg]]
Here you can see the bags, full of water, settled down in the cylinder, with the piston about to be set on top.

[img[Assembled View of TrashBagDrive|./images/together.jpg]]
Here is an assembled view.

[img[Strong Support|./images/strong.jpg]]
The ~TrashBagDrive supports my entire weight with no problem!

When I made a "temporary installation" into the platform, it supported my weight sitting on the platform and felt quite steady and stable.

Today's tests were not entirely trouble free; but I learned a lot. The green 12" PVC pipe that I tried to use initially, and that I used to trace the plywood for cutting my piston, is slightly out of round... as a result, the piston did not fit perfectly, and at times some of the trash bag would work its way up between the cylinder wall and the piston. I think if I make a better fitting pistion, perhaps with a slightly larger piece of foam to push a little more snugly against the cylinder wall, it should work better.

Of course, I also need to create a mount for the cylinder that can be adjusted to match the angle of the polar axis. So much to do, so little time! :)

I will probably try to build a "working model" of this. I will try using some plumbing
fittings at the mouth of the bags and a hose clamp to seal the bags to the plumbing. Then with appropriate fittings I'll be able to adjust the outlet flow properly.

Also, don't let the pictures fool you; this is a "rough prototype" and I may build the final version to follow the curve of the platform motion and it may be rectangular rather than cylindrical. We shall see!

With respect to aesthetics, the trashbag is hidden by the surrounding support cylinder. With respect to durability, you would most likely have to replace the bag fairly often as it is repeatedly crumpled and re-filled.
This is one of the main variations of the DripDrive. It is very attractive for the following reasons:
*Properly shaped, a bellows should not exhibit the TangentProblem.
*All fluid is well-contained in a bellows, it is less likely to leak than a WaterCylinder.
A collapsible jug, such as one of these, might be a good candidate for a bellows.
[img[10qt Jug|./images/10qt.jpg]]
A water cylinder seems to be one of the most sensible means of implementing the drive. It can be made in many different shapes.

Ideally, for a simple manual version of the McCrearyMount, the cylinder should be curved to match the radius from the polar axis. This completely eliminates tangent error, although it does not address atmospheric refraction.

Leaks! I did an experiment with some 2" diameter PVC pipe. My first tests used some flexible plastic foam. It seemed to be closed-cell; in fact, I cut a 2" disk out of an inexpensive "noodle" plastic float. Of course, cutting it opened up the cells along the cut seams. I capped the pipe, filled it with water, and squeezed the foam disk into the pipe to see if it would work as a piston. It of course leaked around the edges....

Next I tried cutting a piston out of wood. I used the edge of a bench grinder to grove the piston to accept an O-ring. This was so irregular it wasn't even funny!

I next used a hole saw to cut another wooden attempt at a piston. After cutting it, I chucked it in a drill press and used a round file to groove it for an O-ring. Sadly, this too came out irregular to the point that there were gaps between the O-ring and the wall of the PVC pipe. The irregularity this time was due to the wood grain, and that it was not turned with a blade in a lathe... and so the grain worked it out of round.

Finally, I cut a piston out of some polyethelyne material (from a cutting board), and turned that in the drill press for an O-ring. No grain, no irregularity to speak of, and finally a pretty good fit in the PVC... however, it still leaks. This time I think it is due to native irregularities (quite visible) in the inside wall of the PVC pipe. Also probably to a cheap O-ring.

I think for the next cylinder experiment I will try something like a brake cylinder or a truely-turned, honed cylinder. Or maybe an old tire pump or water pump? These experiments are causing me to lean back towards the WaterBellows.
For archived earlier "~WhatsNew"s, click [[here|OldWhatsNew?]].
!Tuesday, May 31st, 2011 - RTMC 2011...
I got home Sunday evening from this year's Riverside Telescope Maker's Conference, where a good time was had by all.

Although I had not planned to give a talk this year, when I heard what the theme of the conference was to be (Building Telescopes and Observatories) I felt that I had no choice but to once again "throw my hat into the ring."

Click on this [[Champagne Observatories|http://subarcsec.com/champagne/champagne%20observatory.htm]] link to open an HTML version of the "Power Point" presentation in a separate window.

While you look at the slides, you can listen to the talk I gave right here on-line, by clicking below to play:<<player http://subarcsec.com/subarcsec%20audio/RTMCtalk.mp3 400 50>>
Or, you can "right-click" and download the ~MP3 file here: [[MP3 Audio|http://subarcsec.com/subarcsec%20audio/RTMCtalk.mp3]]

[img[Champagne Observatories|./chintro.jpg]]