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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Wood and Pipe Equatorial Mount
      #6096591 - 09/23/13 10:48 AM

I picked up one of the Celestron 4" (102mm) refractor telescope OTAs that was being sold cheaply that was the rage in the refractor forum. I've been keeping my eye out for something along the lines of a CG-4 or CG-5 mount but in the mean time I decided to see how well a pipe mount would work.

Hereís the scope that I picked up if you're unaware of what it looks like.



Iím going to break the mount down into two pieces: the head and tripod. This post will cover the equatorial head. Iím going to use the classic iron pipe mount.

Here's all the pipe I bought for the mount. The pieces are 1-1/4" fittings which is probably overkill for a scope this size. I might stick a larger scope on the mount at some point if all goes well. In the mean time, it should flex less than a mount made of smaller pipe.



Iíd like to have a way of adding friction to an axis if needed or a way to lock the scope in position. To do this, Iíll use a couple nylon bolts to put pressure on the rotating threads of the pipe. The first step is to mark off the location where the nylon bolts will go and center punch them. Next, using the appropriate tap drill for a 1/4-20 thread, two holes are drilled into the T.



Both these holes have threads cut into them with tapping fluid and a thread tap. Care must be exercised to hold the tap vertical to the surface so that the bolt isnít crooked.



With the pipe portion of the head completed, I turned my attention to making a set of rings. I measured the diameter of the scope tube and then added a little extra to account for felt that Iíll use between the rings and scope tube. I laid out the rings on a piece of plywood with a compass and set about cutting on the tablesaw.



The rings were split so they can fit around the scope tube. The pieces were marked to avoid mixing the pieces up.



To clamp the rings to the scope tube I plan to use a couple 1/4" diameter bolts. Itís much easier to drill straight while the pieces are still square. I donít have a drill bit that is long enough to drill both halves at once so I drilled the top first. Drilling into the side of plywood can be troublesome because the bit may wander due to the layers of wood. Using a center punch to mark the spot you want to drill will help the bit stay where you want it to.



I then clamped both halves together and used the top half as a guide for the drill bit. Once shallow holes were drilled in the lower half, the pieces were taken apart and the lower half was drilled out.



The bandsaw makes quick work of cutting out the rings.



Now it is over to the bench drill press with a spindle sander to clean up the inside of the rings.



The mini-belt sander is used to clean up the outside of the rings. The cut outs in the rings allow the bolt heads and washers to sit flat on the surface.



A base is needed to connect the rings to the pipe flange. I used another piece of plywood 12" long for this. The lower rings halves and a center transfer punch were used to locate the holes for the rings. The flange was used as a template to lay out the holes for it. Off to the drill press againÖwhich I will spare you pics of.



Next, I need a wedge that will hold the assembly at the proper angle to the ground. For me this is 30 degrees. Luckily, 30 degrees is a common angle used in woodworking so most of the saws and guides have it already marked out. I came up with a simple design for my wedge and set about cutting it out on the table saw. In the picture below, Iím about to turn the rectangular piece into another side of my wedge like the one on the right. The rest of the wedge consisted of two more rectangular pieces 1-1/4" thick. The pieces were clamped, drilled, and bolted together.



Now Iím ready to start putting everything together. The lower halves of the rings were attached to the plate using a couple screws. I didnít glue them together though because I may want to use another set of rings one day. The flange was attached with more 1/4" bolts.




Shown below is the equatorial head in its current form. The mount is connected to the wedge with a couple of pipe strapsÖbolted down of course. I couldnít find any nylon bolts and instead got some nylon machine screws. They work pretty well. I can add friction to the system and hold the pieces in place from moving on their own. I can overpower them pretty easily which was expected. All of the pipes were tightened down except the threads near the nylon bolts so they can turn. I have about four complete revolutions before the parts fall apart so I donít have any fears of it falling apart in use. I do plan to do some more sanding and finish the parts. I want to try it out before I do so I can make changes if need be.



Later, Iíll post about the tripod that Iím in the process of making. So far itís looking pretty good.


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Mirzam
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6096617 - 09/23/13 11:01 AM

Nice job and well documented!

Another solution to the ring problem for small scopes is to use large hose clamps with a small section of rubber hose covering the part of the clamp that makes contact against the telescope.

JimC


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DAVIDG
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Reged: 12/02/04

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Re: Wood and Pipe Equatorial Mount new [Re: Mirzam]
      #6096683 - 09/23/13 11:54 AM

You might want to read my article on the Delmarva Pipe mount that was published in the Nov 2012 Sky and Tel. I developed a simple to construct bearing system using PVC reducers and Teflon and the result is a very smooth motion, no machining and 360 degree rotation without having the issue of bearings that use pipe thread.

- Dave


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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: DAVIDG]
      #6096939 - 09/23/13 02:33 PM

Mirzam: Thanks! I'd heard of hose clamps being used but I thought I'd go with rings since I'm able to make them.

DavidG: I'll have to see if I can find a copy of that article. That sounds pretty nice. It's been cloudy since I got the scope and I haven't had a change to try out this mount yet.


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Pinbout
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6096985 - 09/23/13 03:12 PM

Quote:

That sounds pretty nice




I've tried his mount and its much better than just lapped threads.

the only trick is the adapter has to jump 2 sizes down. so 1-1/2" to 1" instead of a normal 1-1/2to 1-1/4, not something I've found stock in the big box stores. maybe order it, mcmaster carr?


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DAVIDG
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Reged: 12/02/04

Loc: Hockessin, De
Re: Wood and Pipe Equatorial Mount new [Re: Pinbout]
      #6096997 - 09/23/13 03:33 PM

My prototype mount used standard 1-1/4" pipe tee and 1-1/4" to 3/4" NPT, PVC adapters which are common and available at my local HomeDepot for under $2 each. The 3/4" pipe I used for the shafts is just a few thousand larger in diameter then standard 1" shaft material. Here is a link to the Stellafane website were there are pictures of the scope which should give you some idea of how it works. It's the 4" f/11.5 "Scope on a Stick" http://stellafane.org/convention/2012/2012-scopes.html

- Dave


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Arjan
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Re: Wood and Pipe Equatorial Mount new [Re: DAVIDG]
      #6097041 - 09/23/13 03:59 PM

Good work!
As an alternative, you can also use copper and brass plumbing parts for a light scope. Tolerances are so good that you get very smooth and hysteresis free movement.
See here.

Edited by Arjan (09/23/13 04:02 PM)


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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: DAVIDG]
      #6097071 - 09/23/13 04:13 PM

Quote:

My prototype mount used standard 1-1/4" pipe tee and 1-1/4" to 3/4" NPT, PVC adapters which are common and available at my local HomeDepot for under $2 each. The 3/4" pipe I used for the shafts is just a few thousand larger in diameter then standard 1" shaft material. Here is a link to the Stellafane website were there are pictures of the scope which should give you some idea of how it works. It's the 4" f/11.5 "Scope on a Stick" http://stellafane.org/convention/2012/2012-scopes.html

- Dave




I'm trying to look at the pics to see what you've done. It appears you've drilled out the PVC adapter to 1" and then run a 3/4" iron pipe through it?


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DAVIDG
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6097167 - 09/23/13 05:12 PM Attachment (65 downloads)

You take the 1-1/4" to 3/4" PVC adapter and drill out the threads so the pipe slips thru. This is NOT the bearing surface so the hole doesn't need to be precise. The pipe just needs to slip thru the hole. I happened to use a 1" forstner bit only because I had it. Now you flip the reducer over and make two cuts at 90 degrees thru the threaded section down to close to the base. This makes four tabs that can move and squeeze down on the pipe as you screw it into the tee since pipe thread is tapered. You then cut a strip of Teflon and bend it into a ring. The strip is about 3/4" wide and a few inches long and made from 3/16" Teflon. This fits inside the reducer. This is the bearing surface and it wraps around the piece of 3/4" pipe that I used as the shafts. Now when you tighten the reducer, it squeezes down on the ring of Teflon which squeezes down on the pipe. The result is no play, very smooth motion, 360 degrees of rotation and you can easily adjust the amount of friction. You make four of these that screw in the ends of the two tees.

- Dave


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DAVIDG
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Re: Wood and Pipe Equatorial Mount new [Re: DAVIDG]
      #6097320 - 09/23/13 07:25 PM Attachment (78 downloads)

Here is a close-up of the back of the modified reducer and the Teflon strip bent into a ring that fits inside it.

- Dave


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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: DAVIDG]
      #6097331 - 09/23/13 07:30 PM

That's very slick (pun intended)! I'm going to give my mount a try in this configuration since I've already built it but I can see upgrading to your setup soon.

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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6097567 - 09/23/13 10:25 PM

I finished up the tripod enough to try the mount and scope out tonight. I'll try to get some pics up of the assembly of the tripod later. Overall, I'd say the mount and tripod are a success. It moves pretty well and once I got the counter balance weight right I didn't have to fiddle with the nylon screws much. It pushes around well and holds position. Vibration from focusing seems to die out quickly (easily under a second) and vibration from tapping on the legs dies out even quicker. There was a light breeze blowing tonight and I didn't notice it at the eyepiece. I swung around and checked out the Messier objects in Sagittarius, found M13, and looked at the Double Double. Everything looked good in the scope.

On the downside, I do think the motions could be a little smoother and there is a little bit of sticktion. It's also pretty big when all setup. I expected it to be large but it is something to see it all together. On the bright side viewing at zenith isn't uncomfortable though using the straight through finder is. I can still pick it up in one piece and move it around the yard though. I'll try to weigh it later. I also miss the Rigel on my dob. But that can be fixed.


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Chuck Hards
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6097964 - 09/24/13 08:31 AM

Examine any flanges that you purchase very carefully. The last time I built a pipe mount, I discovered that the face of the flanges was not anywhere near orthoganol to the threaded axis. I had to face them on a lathe.

Not a big concern on a strictly visual mount for a small telescope, but something to be aware of.

When using the pipe threads as the bearing surface, it helps to lap them with automotive rubbing compound prior to final assembly. Mirror-grinding extra-fine grit and oil can be used, as well. Spin the fittings together many times with the lapping medium generously applied, tightening them and loosening them repeatedly, until you gain another 1/4 to 1/2 turn. Then clean them with laquer thinner or other solvent before final assembly and use your lubricant of choice on the threads. It noticeably improves the smoothness of the action.


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Edward E
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6100500 - 09/25/13 02:13 PM

Now that is a nice looking DIY GEM!

I like your belt sander. I'm going to get one some day. What model/make & table size is your band saw?

Edited by Edward E (09/25/13 02:15 PM)


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DavidinFL
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Re: Wood and Pipe Equatorial Mount new [Re: Edward E]
      #6100554 - 09/25/13 02:36 PM

Quote:

Now that is a nice looking DIY GEM!

I like your belt sander. I'm going to get one some day. What model/make & table size is your band saw?




Thanks! It's a Rockwell 14" band saw from the 1970s. I'm not sure of the table size off the top of my head. I'll try to measure it tonight. If you'd like to see more pics of it I've got some on my site. This link and the next three posts there are about the band saw: http://somanyhobbies.wordpress.com/2012/09/15/rockwell-bandsaw/


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StarStuff1
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6100897 - 09/25/13 05:16 PM

Let's see: pipe fittings, plywood and PVC parts for an ATM EQ mount. MMMMmmmmm... GOOD!

Looking forward to seeing pics of the tripod.


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Rutilus
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Reged: 12/17/10

Re: Wood and Pipe Equatorial Mount new [Re: StarStuff1]
      #6100914 - 09/25/13 05:26 PM

Nice work with the Equatorial.

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DavidinFL
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Re: Wood and Pipe Equatorial Mount new [Re: Rutilus]
      #6101641 - 09/26/13 01:47 AM

In the previous post I described the equatorial head I'd made for my telescope mount. Now I'm going to cover the tripod. First, I needed to figure out how large the tripod needs to be. To do this I measured the highest and lowest points the eyepiece would be from the floor with my scope in the equatorial head clamped to a bench. Then I measured the height of my eye while I was bent over in the sitting position. From here I figured how how much I need to raise the eyepiece at the lowest point to get it to a comfortable position. This resulted in me needing a tripod that lifted the equatorial mount 46" from the ground.

I looked around for designs of wooden tripods and came across a design I liked in a book called "Build Your Own Telescope" by Richard Berry. The book covers several telescope builds and one of them was for a tripod mounted 6" refractor. I used the design as a jumping off point to make my own design. In the book, each leg was held at an angle of 75 degree from the ground which results in me needing roughly 48" long legs. In the book, each tripod leg is an I beam made up of three pieces of wood. I decided to go with a C channel shaped beam still made up of three pieces. The legs start wide at the top and then taper to a point at the bottom in the book. I liked this element and went with it. I laid out the design for the wed of the C channel on the pieces of wood and then cut them out on the band saw.



The band saw doesn't leave a smooth surface on the edges of the pieces. A hand plane makes quick work of smoothing the sides.



The flanges on my C channel legs are made of a 1x4 ripped in half on the table saw. To make sure both pieces were the same width, I ran all the pieces back through the saw after setting the fence to the width of the thinnest piece.



To attach the flanges to the web I drilled holes every six inches for screws. I also drilled the hole for the bolt that the leg will pivot on.



The pieces were glued, clamped, and the screwed together. I clamped sections, inserted screws and then moved down the line leading the way with clamps.



On the pointed ends of the legs, clamping is a must to bend the wood to the shape. The web at the location for the last hole isn't thick enough to be screwed into. Instead I bolted the pieces together. It's not coming apart now.



To connect all the legs together I borrowed another idea from the book. My hub consists of two pieces of 3/4" plywood in the shape shown below. I started with a 10" diameter circle and then laid everything out with a straight edge and protractor. It's always good to shade the areas you want to cut as it is tough to add material back.



Off to the band saw for more cutting. I freehand cut all the pieces because I planned to clean them up on the sander.



Here's the two pieces clamped up while the glue sets. After the glue dried the inside edges of the piece was sanded.



To go on top of my hub I cut out a 10" diameter circle. All the parts were center drilled, glued, and then temporarily bolted together so I could sand them as one piece.



To attach the legs I held them in the extended position pushed up against the top of the hub. This way the legs will jam tightly when opened to increase the stability of the tripod. I marked the location for the bolt holes by drilling shallowly into the hub with the legs in this position. I finished the holes using the drill press. I drilled down halfway on one side and flipped the piece over to drill the other half of the hole. This way, if your drilling isn't perfect the problem is inside the piece where it can be fixed as opposed to being off when you exit the other side of the piece you're drilling.



Here's everything together. To attach the head to the tripod I drilled a 3/8" hole and bolted the two together. A wing nut on the bolt allows me to move the head around in azimuth.



The tripod was very stable but when lifted the feet would come together as expected. To fix this I added a spreader in between the legs. I thought about it for a little bit and decided I'd add braces attached to each leg that would meet in the middle. I recalled a joint in a book I have around here called the Triple Lap joint that would be perfect. Here's the one I made.



How do three pieces of wood occupy the same space? Here are the piece separated for a better view.



I installed the spreader using hinges and put a bolt through it to hold it closed. The joint is meant to be stacked vertically. Swinging the arms together on an arc causes results in them not coming together smoothly. I think I'll need to remove a little material to solve this problem sometime soon. But it does come together nicely.



Here's an underside view on one of the spreader arms. The end of the arm is cut at a 15 degree angle to jam up against the legs.



The spreader can be disassembled allowing the legs to collapse for storage.



Finally, the pic you've been waiting for. This is the setup currently. I'm still testing so I haven't finished any of the pieces. No finish means I haven't put felt in the rings so I'm using a towel to take up the space.



I put it all on the bathroom scale and measured the weight of all the pieces. Currently the tripod weighs 16.4 lbs, the equatorial head weighs 11.6 lbs, the scope with diagonal and finder weighs 7.6lbs, and the counterweight is 7.5 lbs. Summed this results in about 43 lbs. I have given thought to making new legs with material taken out of the webs to reduce weight. I think I could lighten it some but I don't want to decrease its rigidity. Currently, it may be on the heavy side but it is solid as a rock. I may add a tray on top of the spreader as well. Next up will be rounding corners, sanding, and finishing.

I had the scope out tonight looking at Uranus and some double stars. I noticed a little more vibration than I did previously and still had the sticktion issues. I'm also still trying to think of ways to reduce setup time and hassle. I ordered some Teflon so I can give DavidG's design a try. Home Depot had the reducers so I should be all set when the Teflon arrives.


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Geo31
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6101761 - 09/26/13 06:43 AM

Instead of producing new legs, why not drill a series of holes along the length? Maintain much of the strength and rigidity but still shedding mass.

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Edward E
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6102140 - 09/26/13 11:20 AM

Excellent build! A very steady mount for that refractor.

I would recommend putting some self adhesive green felt on the OTA clamps to protect the OTA finish. Has always worked for me.

Drilling the holes into the legs to lighten the weight is a good idea. I have seen that done in other builds here in ATM as well as in Richard Berry's books.

I enjoyed reading your web page blogs, though I nearly cried reading about the iron skillet restoration. The rust must go but Ooooo, the removable of the seasoning layer. It would be like erasing my grandmothers memory (I have her cast iron skillets); all those biscuits, ham, bacon and pinapple up side down cake. I think I'm hunger now.


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