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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: Geo31]
      #6102253 - 09/26/13 12:23 PM

Quote:

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.




I've considered doing that or using a jig saw to remove bigger areas. I've also got an idea about making legs with the same flange pieces but using horizontal strips of wood as the webs. The material for the legs cost less than $15 so I don't mind making another set and keeping the originals intact in case I remove to much.

Quote:

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.




Thanks! I've got some adhesive felt but haven't put it on yet. I'm waiting to put the finish on the wood first. I have a wide variety of topics on my site for sure. I'm glad you found them interesting. I picked up my cast iron pans from a flea market so there might have been industrial grease on them for all I know. It had to go! It'd be different if I knew the history of the pans.


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DavidinFL
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Reged: 08/28/09

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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6104372 - 09/27/13 02:38 PM

I made the new legs for the tripod this morning. They’re the same shape as before but lack the large webs of the solid legs. The previous legs weigh 4lb 2oz while the new ones weigh 2lb 12oz a piece. Total, the tripod is now 4lb 2oz lighter. It still feels very rigid when the spreader is used. I hope to give it a try tonight.



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Geo31
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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6104394 - 09/27/13 02:53 PM

Outstanding!

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richard7Moderator
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Re: Wood and Pipe Equatorial Mount new [Re: Geo31]
      #6105066 - 09/27/13 10:45 PM

Darn good looking tripod Dave.

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allardster
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Re: Wood and Pipe Equatorial Mount new [Re: richard7]
      #6105141 - 09/28/13 12:06 AM

Nice intricate triple lap joint there! What tools did you use to make these?

This is one of my favourite threads. Full of ideas to borrow. Thank you for documenting and everyone for piping in on the pipe part.


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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: allardster]
      #6105181 - 09/28/13 12:58 AM

Quote:

Nice intricate triple lap joint there! What tools did you use to make these?

This is one of my favourite threads. Full of ideas to borrow. Thank you for documenting and everyone for piping in on the pipe part.




I used a table saw with a dado stack and miter gauge to cut the triple lap. It's actually not to hard to cut once you see how it's done.

I did some more work on the scope this afternoon and integrated DavidG's Teflon bearings. That makes a huge difference and completely changes the way the scope feels when moving. It's much improved over the pipe on pipe setup. I also made a few more small changes. I'll post some updated pics and more info tomorrow.


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Boot
wildly diverse musical tastes
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Reged: 06/04/07

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Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6105809 - 09/28/13 12:02 PM

Quote:

I made the new legs for the tripod this morning. They’re the same shape as before but lack the large webs of the solid legs. The previous legs weigh 4lb 2oz while the new ones weigh 2lb 12oz a piece. Total, the tripod is now 4lb 2oz lighter. It still feels very rigid when the spreader is used. I hope to give it a try tonight.






(Reminds me of a pair and a half of crutches)

Like the tripods Ed Turco's made, shown here.

Nice work all around. Thanks for sharing.


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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: Boot]
      #6106414 - 09/28/13 06:16 PM

I've implemented the changes DavidG suggested for his Delmarva mount system. The mount now utilizes some PVC reducers and Teflon to provide better bearings.

The first step is to modify the PVC 1-1/4" to 3/4" bushings. The 3/4" side needs to be bored out using a 1-1/8" Forstner bit so that a 3/4" galvanized pipe can pass through it.



Next, the 1-1/4" end needs to be bored out to large enough so that the 3/4" pipe with Teflon wrapped around it can fit. I used 1/8" thick Teflon which required me to bore bushing out to 1-3/8". I did this on the lathe as it is easier to find the center of bushing. When boring the bushing you want to bore down only as far as needed so that a shoulder is left in the bushing to keep the Teflon from sliding out.



The thread on most plumbing pipe is tapered. This can be used to our advantage to increase or decrease the friction on the bearings. If the bushing is slotted as shown below, as it is tightened it will bend in pushing harder on the Teflon and pipe. The bushing on the right has the Teflon bearing material installed.



To use the new bushings I had to redesign the mount. Some of the parts are still there but I’ve added a few new pieces. Instead of pipe threads acting as bearings on each other, 3/4" galvanized pipe is held by the PVC and Teflon bushings. The 3/4" pipe is threaded into a 1-1/4" to 3/4" galvanized reducer and the whole piece spins.



Previously to get the scope rings apart I had to remove four 1/4" nuts. To speed this process up I put small hinges on one side of the rings.



On the other side, I put some well nuts. I stumbled upon them at Lowe’s and they work well for this purpose. They’re made out of rubber with a 1/4" nut set into the bottom. They’re easier to get a grip on than the hex nuts.



Viewing with the scope is much improved over the previous design. The scope now turns smoothly and stiction is pretty much nonexistent. On the downside, the mount gained another 2.6 lbs bringing the total weight up to 41 lbs with scope and counterweight. This was definitely a worthy modification though.

Edited by DavidinFL (09/29/13 11:40 AM)


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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: DavidinFL]
      #6106676 - 09/28/13 10:28 PM

Dave,
Great job, and glad to see that the Delmarva Mount worked well for you as well. I'm a little surprised that you had to bore the back side of the reducer out for the Teflon. I used a couple of different thickness of Teflon when I developing the design and all worked well without any boring of the back side of the bushing. I just cut the length of the strip of the Teflon so it would fit inside the bushing when it was bent into a ring and had a gap in the end so the Teflon could have remove the move as it was squeezed down around the pipe. The taper of the pipe thread gives a wide range of how much it can be screwed into the piping fitting, offering a simple way to compensate for different thickness of Teflon, within reason. I designed the system so that only simple hand tools are required to make the bearing. One could, for example uses a file to just remove the threads in the bushing so the 3/4" pipe would slip through. My goal was a system that worked very well but also kids or someone with the access to power tools could build.

- Dave


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Rougeaux
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Reged: 08/15/13

Loc: Southwest Virginia
Re: Wood and Pipe Equatorial Mount new [Re: DAVIDG]
      #6107430 - 09/29/13 12:50 PM

Do you think the equatorial axis would move freely enough to be motor-driveable? I'm looking at building a mount for my 102 and it would be great if I could do some rudimentary astrophotography experiments with it while I save up for something good. My current designs involve ball bearings but I get the feeling PTFE will probably end up being better on both the cost and workability fronts.

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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: Rougeaux]
      #6107822 - 09/29/13 04:36 PM

Quote:

Do you think the equatorial axis would move freely enough to be motor-driveable? I'm looking at building a mount for my 102 and it would be great if I could do some rudimentary astrophotography experiments with it while I save up for something good. My current designs involve ball bearings but I get the feeling PTFE will probably end up being better on both the cost and workability fronts.




Yes, it moves freely and the amount of friction can be varied. I've considered it as well.


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Dick Parker
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Reged: 08/17/07

Loc: Tolland, CT and Chiefland, FL
Re: Wood and Pipe Equatorial Mount new [Re: DavidinFL]
      #6108192 - 09/29/13 08:56 PM Attachment (50 downloads)

David -

FWIW, I have used wood and pipe mounts since the 1960's and my primary mount is still the wood and pipe mount that I have iterated since then. I have tried every sensible type of bushing and bushing material in the attempt to get a clock drive to work. Yes, even the PVC and teflon and ebony star etc. I was not successful getting a clock drive to track well until I put a ball bearing on the North polar shaft end. At one point I did get the mount to track before I added the ball bearing, but with the clutch very tight which was a strain on the gears. For best results, the polar shaft must be absolutely frictionless.

Now, I was using a worm and gear type drive with a synchronous motor. Don't know about steppers etc.

Good luck
Dick Parker


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Boot
wildly diverse musical tastes
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Reged: 06/04/07

Loc: The Outernet
Re: Wood and Pipe Equatorial Mount new [Re: Dick Parker]
      #6108306 - 09/29/13 10:08 PM

Dick - That is stunning.

Any plans available for that beauty?


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DavidinFL
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Reged: 08/28/09

Loc: Navarre, FL
Re: Wood and Pipe Equatorial Mount new [Re: Dick Parker]
      #6108466 - 09/30/13 12:02 AM

Quote:

David -

FWIW, I have used wood and pipe mounts since the 1960's and my primary mount is still the wood and pipe mount that I have iterated since then. I have tried every sensible type of bushing and bushing material in the attempt to get a clock drive to work. Yes, even the PVC and teflon and ebony star etc. I was not successful getting a clock drive to track well until I put a ball bearing on the North polar shaft end. At one point I did get the mount to track before I added the ball bearing, but with the clutch very tight which was a strain on the gears. For best results, the polar shaft must be absolutely frictionless.

Now, I was using a worm and gear type drive with a synchronous motor. Don't know about steppers etc.

Good luck
Dick Parker




Hmm, thanks for the info. That could complicate things. I've already ordered some stuff to construct a drive so I think I'll give it a try even I will be walking the unsuccessful path you walked before. Was there to much friction for the motor to work or did it just grab and release? Or something else?

I like the tangent arm fine adjustment knob on the declination axis. Nice scope overall!

Edited by DavidinFL (09/30/13 12:04 AM)


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careysub
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Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: Wood and Pipe Equatorial Mount [Re: DAVIDG]
      #6108619 - 09/30/13 02:52 AM

Do you think that 3/4" wide, 1/8" thick UHMW

http://www.mcmaster.com/#8702k22/=oq84z1

or 3/4" wide. 1/4" UHMW might serve in place of the Teflon?

http://www.mcmaster.com/#8702k62/=oq84if

I ask for two reasons, this material is quite cheap (about 1/10 the cost of the PTFE), convenient (already cut to width), and it has superior wear resistance (about 8 times that of PTFE).

It would be nifty if this could be used instead of 3/16" PTFE.


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StarStuff1
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Re: Wood and Pipe Equatorial Mount new [Re: careysub]
      #6108704 - 09/30/13 06:10 AM Attachment (29 downloads)

The triple lap joint for the tripod leg spreader is very nice.

A slightly simpler solution is to arrange the leg spreaders to connect by the thickness of the wood. I hope this pic makes this clear.


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DAVIDG
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Re: Wood and Pipe Equatorial Mount new [Re: Rougeaux]
      #6109015 - 09/30/13 10:28 AM

Quote:

Do you think the equatorial axis would move freely enough to be motor-driveable? I'm looking at building a mount for my 102 and it would be great if I could do some rudimentary astrophotography experiments with it while I save up for something good. My current designs involve ball bearings but I get the feeling PTFE will probably end up being better on both the cost and workability fronts.




Dick Parker is a good friend of mine, and one of THE BEST telescope makers around, along with being an excellent engineer so I value his opinion. At the same time I'm also an engineer and the designer the Delmarva mount, so I do believe that the friction is low enough that one could make a clock drive and have the scope track well. Mounts like the Poncet type use a simple bearing system similar to the Delmarva system and can be made to track well. It is going to come down to how well the drive is engineered. There are many examples of commerical mounts that used either a simple Nylon or Teflon bushings as the bearing which is the principle used in the Delmarva system that also came with clock drives and would track

All the Best
- Dave


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MKV
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Re: Wood and Pipe Equatorial Mount new [Re: Dick Parker]
      #6109622 - 09/30/13 04:57 PM Attachment (35 downloads)

Dick Parker's and DavidG's solutions are both easthetically beautiful as well as fuctional. I wish some manufacturers were offering mounts fashioned after Dick Parker's example shown, or something simple as teflon pipe mount bearing mounts DavidG made. The difference is that Dick's beauty required a machine shop while David's doesn't.

However, Dick is right about the R.A. axis having to be smooth and for that, some kind of frictionless bearing is required for a telescope to track correctly. If the desire was to come up with something that an ATM without a machine shop can do, then a combination of pipe fitting and pillow block bearings seems to be the easiest solution to pursue.

Two-inch pipe flanges and a 45-degree fitting is ideal for mounting on a tripod and also for mounting the R.A. axis on it. The declination axis can be flanged using hardwood bored with Forstner bits, and making sure the steel axis goes all the way through the declination plate. Using oak for both plates and the tripod is the way to go.

The mount will weigh a ton but that is actually good!


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magic612
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Re: Wood and Pipe Equatorial Mount new [Re: careysub]
      #6111108 - 10/01/13 12:18 PM

Quote:

Do you think that 3/4" wide, 1/8" thick UHMW

http://www.mcmaster.com/#8702k22/=oq84z1

or 3/4" wide. 1/4" UHMW might serve in place of the Teflon?

http://www.mcmaster.com/#8702k62/=oq84if

I ask for two reasons, this material is quite cheap (about 1/10 the cost of the PTFE), convenient (already cut to width), and it has superior wear resistance (about 8 times that of PTFE).

It would be nifty if this could be used instead of 3/16" PTFE.




The coefficient of friction for PTFE/Teflon is lower than UHMW. Given the small range of motions and extremely low speeds these are used at, I think Teflon is probably better, despite the lower abrasion resistance. I've used UHMW on Dob mounts before - there is some "stiction" that occurs. PTFE/Teflon is more expensive, but it generally works better for telescope applications, too. At least that is my experience with it.


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DavidinFL
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Reged: 08/28/09

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Re: Wood and Pipe Equatorial Mount new [Re: magic612]
      #6120671 - 10/06/13 02:09 PM

I worked on the drive for my mount some over the past week. I decided to go for a tangent arm style drive. I don't want to do long term photography so I care about the errors associated with a tangent arm over time. If I could hold something pretty much steady for a little bit I'd be happy.

I have a 2.5" tangent arm being pushed by a carriage on a 1/4-20 bolt driven by a 0.5 RPM motor, from Servocity.com, geared down to 0.3 RPM. Ideally, I need to run at 0.218 RPM according to the math. To vary the speed I'm using a simple potentiometer. The arm is made of wood and I clamp it down on the RA shaft via a bolt. To increase the friction between the wood and shaft I used a strip of sandpaper. Ideally, I'd move the object I want to track in place, turn on the motor and then tighten down the clamp bolt.

I'd say I've met with moderate success. It works intermittently. To test it I stared a Altair a lot through my 7mm eyepiece at 144x magnification. Most of the time I could decrease the rate at which it was moving and only rarely could I arrest the motion or push the star in the wrong direction. The few times I got it to track well I really had to crank down on the bolt holding the arm onto the RA shaft. Still there were a few times the star moved off to the left instead of down indicating it was working but that my RA shaft wasn't pointed perfectly at the celestial north pole.

There are a couple issues that I think are giving me trouble. The first is that getting the arm to clamp tightly on the RA shaft so they turn as one is tough. Yeah I know, soft wood on steel is an issue. Making this piece of out metal would work better I think. To get it really tight though I think I'd have to have some sort of tool to use on the clamping bolt. The second issue I'm having trouble with is flex. As most of the drive is made out of wood there aren't super tight tolerances. As the drive runs it removes these tolerances by jamming everything together but that takes time because the carriage only moves at 0.01"/min. I also have a spring on the threaded 1/4-20 bolt so I could unlock the gears to rewind the carriage. I'm pretty sure this is compressing some as it runs.

To fix things I need to increase the friction between the RA shaft and arm. I can't permanently join the together and I'd like to avoid having to use something like an Allen wrench to tighten something like a set screw. To fix the tolerance issue I can try to make everything tighter or make the tangent arm longer. Making the arm longer requires the carriage to move faster which would remove the slack faster. Getting the carriage moving faster would require me to order some more gears if I want to rotate faster than 1 RPM. Of course making the whole thing out of Aluminum would probably work too...but thats beyond my current capabilities.

All that aside, if I had a normal style spur and worm gear setup on this mount the motor would drive it ok.

Here's a couple pics of the current setup.




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