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russellhq

Designing The Pier Head

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This is probably a silly question to ask. But take my HEQ5 mount as an example, do I need access to the screw that connects the mount to the pier when polar aligning? I.e. Should it be loosened off a little for Azi adjustments and tightened up when finished?

I'm trying to understand why so many pier top adapters are designed to provide access to this screw and whether there's another way of doing it so that access from underneath is no longer required?

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Easy access to the azimuth knobs allows for more accurate polar alignment in the horizontal axis....

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Thanks, it's not the azimuth knobs I want to hide access to but instead it's the screw that holds the mount to the tripod/pier.

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20 minutes ago, russellhq said:

This is probably a silly question to ask. But take my HEQ5 mount as an example, do I need access to the screw that connects the mount to the pier when polar aligning??

YES, you are correct. I have a tripod mounted AZ EQ6. To PA, I slacken off the centre screw just a smidge, set PA, and then tighten back up.

For a permanent pier mount, you will hopefully only need to do it just the once, but you still need to tighten that bolt tight when you achieve good PA.

 

Huw

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One way to avoid the need to slacken the bolt is to use a thrust bearing between the bottom face of the adaptor top and the bolt head itself. You can fully tighten the bolt but it will still rotate as you adjust the azimuth. You might also need a Teflon washer between the bottom of the mount head and the top of the adaptor 

Edited by IanL

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Thanks Huw, that's what I though.

I'm wondering if something like this could work?

Looking down from the top

PierPlateTop.thumb.png.5c86501868ae602f6bbeb9bee5f87217.png

 

Looking up from the bottom

PierPlateBottom.thumb.png.7cf98b5048a709589bcc610d728a20c8.png

 

You would connect this to the bottom of the heq5 mount through the central hole. Then, on the pier you would have 4 threaded rods that would fit through the slots and a fifth rod for the azimuth adjustment screws to react off.

PuckOnPier.thumb.png.95d3cd107b8f18f23818a58874f9c8bd.png

Once you were happy with polar alignment, you would tighten down the nuts on top

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27 minutes ago, IanL said:

One way to avoid the need to slacken the bolt is to use a thrust bearing between the bottom face of the adaptor top and the bolt head itself. You can fully tighten the bolt but it will still rotate as you adjust the azimuth. You might also need a Teflon washer between the bottom of the mount head and the top of the adaptor 

What if you put a thrust bearing between the mount and the adapter i.e. a 100mm diameter thrust bearing? Something like this?

https://simplybearings.co.uk/shop/p504858/51115-Budget-Single-Thrust-Ball-Bearing-75x100x19mm/product_info.html

 

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I guess it's a question of stability. The small thrust bearing has the advantage of the mount being in contact with the adaptor across the entire surface. Might be a risk of this method being less stable depending on the bearing, but in theory it could work - basically the same idea as a dob base modification.

Edited by IanL

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1 hour ago, IanL said:

I guess it's a question of stability. The small thrust bearing has the advantage of the mount being in contact with the adaptor across the entire surface. Might be a risk of this method being less stable depending on the bearing, but in theory it could work - basically the same idea as a dob base modification.

If we are talking about a permanent installation, (which I think is what the OP had in mind) isn't a bolt we can 'get at' all we need? At most a large 'penny' washer on that main bolt will keep alignment fairly stable whilst setting up.

 

Huw

Edited by Horwig
can't type to savefd dmy lifeb
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10 hours ago, Horwig said:

If we are talking about a permanent installation, (which I think is what the OP had in mind) isn't a bolt we can 'get at' all we need? At most a large 'penny' washer on that main bolt will keep alignment fairly stable whilst setting up.

 

Huw

Just answering the question that was actually asked in the first post, i.e."us there another way".

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If you consider the central screw important when on its' tripod, for stability & attachment, then some form of bolt-down is required. I just use some M10 studding, that screws up into the mount with a large Penny Washer \ nut, tightened after polar alignment. And yes tightening up the nut too much will introduce slight errors in alignment, so not too tight....

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11 hours ago, IanL said:

Just answering the question that was actually asked in the first post, i.e."us there another way".

Sorry, I stand chastised!?

Actually, there is another way, it's the way the EQ8 does it with a 90 degree gearing arrangement

eq8.thumb.JPG.2b08d227ab3a0bc6eb5547344fb8704e.JPG

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11 hours ago, Horwig said:

Sorry, I stand chastised!?

Actually, there is another way, it's the way the EQ8 does it with a 90 degree gearing arrangement

eq8.thumb.JPG.2b08d227ab3a0bc6eb5547344fb8704e.JPG

Interesting but maybe over engineering it a bit? How does the primary shaft fit through the tube I wonder? Can't just be a through hole as I doubt that would keep the gears engaged?

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I use a meter length of 16mm threaded rod with a length of steel pipe acting as a sleeve.

So I can climb the stepladder inside my 14' tall pier and tighten the azimuth from underneath with a big spanner. 

Well, it might be useful information for somebody.  :biggrin:

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The standard solution is to drill an 'owl hole' or 'owls nest' in the side of your steel tube. It just has to be big enough to get your hand and a socket wrench in. Can also be used to bring your cabling up and out of the pier!

Owls nest for nut access/cable management.

42309883994_75f9212fe4_b.jpg

 

Alternatively- if your pier adaptor puck is a nice, rotating fit in the top of your steel tube, you can just rotate the puck within the steel tube and lock it off with grubscrews through the tube. No need for any access to the main nut needed. This is what I ended up doing on my second pier.

Edited by laser_jock99

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Because I plan to use concrete, I don't think drilling is an easy option. I do like the grub screw idea, but instead of one between the pier and puck I could put one between the puck and mount. That could work couldn't it?

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I have a 10mm thick round steel plate on top of my concrete pier then 4 M16 threaded rods to a similar round steel plate that takes the mount.  There is about 6" (150mm) between the plates giving easy access to the mount clamping bolt.

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As you say you are using a concrete pier, this is my arrangement.... 

All studding is A4 Stainless and the red box highlights the studding that lock the mount in-place.

IMG_2018_06_27_0708.JPG

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I made a former out of some mdf to make a wedge shaped access hole in my concrete pier.

Just remember that wood floats on concrete!

pier.jpg

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Here's a link to a blog post explaining how I did my small steel pipe and concrete imaging pier. I used a modified Skywatcher NEQ6 extension tube for the pier head (there are two parts covering the pier build):

https://www.blackwaterskies.co.uk/2017/09/building-a-small-imaging-observatory-part-1/

https://www.blackwaterskies.co.uk/2017/09/building-a-small-imaging-observatory-the-pier/

If you keep the main part of the pier below 1 metre in length and don't need a big load carrying capacity, you can get the pipe and rebar delivered from eBay fairly cheaply. It would work for a longer pier with a more substantial foundation block and a larger diameter pipe. If I was doing it again though, I'd use the black metal disk at the bottom of the extension as the form for the top of the concrete for a better fit, though mine works fine after I shimmed it a bit.

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1 hour ago, IanL said:

Here's a link to a blog post explaining how I did my small steel pipe and concrete imaging pier. I used a modified Skywatcher NEQ6 extension tube for the pier head (there are two parts covering the pier build):

https://www.blackwaterskies.co.uk/2017/09/building-a-small-imaging-observatory-part-1/

https://www.blackwaterskies.co.uk/2017/09/building-a-small-imaging-observatory-the-pier/

If you keep the main part of the pier below 1 metre in length and don't need a big load carrying capacity, you can get the pipe and rebar delivered from eBay fairly cheaply. It would work for a longer pier with a more substantial foundation block and a larger diameter pipe. If I was doing it again though, I'd use the black metal disk at the bottom of the extension as the form for the top of the concrete for a better fit, though mine works fine after I shimmed it a bit.

I've never seen the Skywatcher pier extension up close. How does it provide access to the mount retaining screw?

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41 minutes ago, russellhq said:

I've never seen the Skywatcher pier extension up close. How does it provide access to the mount retaining screw?

The top piece is held in to the extension tube with three screws around the circumference. It lifts off and there is a short bolt inside that goes through the hole in to the mount. You screw the top piece to the mount base using it, drop the assembly on to the tube and secure with the screws.

This is why is has a thrust bearing, so that the mount can rotate in azimuth as the central bolt is fully tightened and inaccessible before you start polar aligning. I'd recommend greasing the bearing well and using a telfon/plastic milk container washer between the mount and the top piece to aid rotation. 

It's not perfect as the adjustment is fairly stiff, and if you work the mount back and forth using the azimuth adjusters it can work the retaining bolt slightly loose making it hard to keep alignment, necessitating a quick break-down to re-tighten and start over. Second time was the charm for me and managed to get good polar alignment which has stuck fairly well over a year.

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+1 for the SW extension.

I use it on my pier for the NEQ6 and C11...

It is fixed to the pier with a 12.5 x 1.75mm bolt which holds the bottom plate of the extension tightly against the top of the pier.

No issues, no drama in over four years......

Mainsail Obs 001s.jpg

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The "Todmorden" piers come with "owl's nests" ready cast in.   ?       

002.JPG

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26 minutes ago, Peter Drew said:

The "Todmorden" piers come with "owl's nests" ready cast in.   ?       

002.JPG

Thanks Peter, this is something I had seen before and am considering as an option for the pier.

The only issue i can think of with this is the pier top I have for connecting the mount to the pier, it's got 5 screws to hold it down which I don't fancy drilling the holes for in the concrete block. I don't think I will be able to get them aligned correctly.

Top and bottom of pier puck:

IMG_20180620_211912.thumb.jpg.4bc376e773c63956074370747826550a.jpg

IMG_20180620_211927.thumb.jpg.5ffde3b209c5031bde3623c9c0d398b3.jpg

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