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  #1  
Old 12-04-2017, 05:08 PM
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speach (Simon)
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pier tops

It has me puzzled why people go to all the trouble of making a pier then negate the solidity of it by putting the mount on four bolts that are at least 100mm from the top plate of the pier. why not place the mount straight on the top plate?
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  #2  
Old 12-04-2017, 05:16 PM
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Is it because most mounts have a bolt that comes through from underneath to secure the mount to the plate? Unless there is a large hole in the side of the pier, the bolt can't be accessed otherwise.
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  #3  
Old 12-04-2017, 05:26 PM
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Quote:
Originally Posted by Dave221 View Post
Is it because most mounts have a bolt that comes through from underneath to secure the mount to the plate? Unless there is a large hole in the side of the pier, the bolt can't be accessed otherwise.
Yes it can just take the legs off the tripod and fix it straight on the top plate which is fixes on the pier top, bolt it right into the pier, that's what I've done
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  #4  
Old 12-04-2017, 06:32 PM
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Quote:
Originally Posted by Dave221 View Post
Is it because most mounts have a bolt that comes through from underneath to secure the mount to the plate? Unless there is a large hole in the side of the pier, the bolt can't be accessed otherwise.
If that were the case, it would still be vastly preferable than using a "rat cage". Some people use it to level the top of the pier but a little care during construction eliminates that problem as well. It makes absolutely no sense to build a 100 kg pier and then hang a huge moving mass on 4 bolts.
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  #5  
Old 12-04-2017, 06:48 PM
glend (Glen)
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Many mounts require an adaptor to fit securely to a plate. Even my old EQ6, which had the tripod top bolted to the plate by a single central bolt, was not stable due to the relatively narrow support base of the tripod top section (without the legs). Larger mounts like the CGX and CGX-L, and EQ8, CGE Pro etc, require support and there are adaptors for that purpose, adaptors have to be fixed to a plate, hence a top plate. They do not have to be elevated any higher than required for tool access. There are hundreds, if not thousands, of pier mounts around the world being used for imaging, with minimal issues related to top plate slop. A correctly designed structure will not be moving around.
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  #6  
Old 12-04-2017, 07:41 PM
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I think that any sort of pier has to be much more stable than the foldable tripod legs that come with most mounts. The only way my rig is going to fall over is if the single central bolt that holds the mount down breaks. No point in constructing a pier that can support 1000kg when you are only putting a 40kg payload on it. Most piers and their concrete bases are probably way over engineered.
I have a rats cage top and the pier is concreted in with only a wheelbarrow and a half of concrete. No stability issues here with a 10' newt and 20kgs of counterweights on top.
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  #7  
Old 12-04-2017, 10:14 PM
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Rick,

The strength requirement of a pier is the easy part of the pier design, and what you say is true.
But the other main function of a pier (at least for astrophotography) is also to transmit any and all movement and vibration to the ground, that requires much greater rigidity, which has the unnecessary byproduct of being over engineered as far as strength is concerend.

So there is a point to it, but its not for strength.

Of course if there are weak links in the chain - eg rats nest on little M12 threaded rods, mount backlash and high PE then the quest becomes less useful, but its all about progression, so building the cheapest part of the system (pier) to be a strong link rather than a weak link makes sense as you are only arguing about loose change by comparison.
Maybe $50-100 or less and a bigger hole = more labour !

Quote:
Originally Posted by doppler View Post
I think that any sort of pier has to be much more stable than the foldable tripod legs that come with most mounts. The only way my rig is going to fall over is if the single central bolt that holds the mount down breaks. No point in constructing a pier that can support 1000kg when you are only putting a 40kg payload on it. Most piers and their concrete bases are probably way over engineered.
I have a rats cage top and the pier is concreted in with only a wheelbarrow and a half of concrete. No stability issues here with a 10' newt and 20kgs of counterweights on top.
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  #8  
Old 13-04-2017, 01:31 PM
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Quote:
Originally Posted by speach View Post
Yes it can just take the legs off the tripod and fix it straight on the top plate which is fixes on the pier top, bolt it right into the pier, that's what I've done
Can you provide a picture of how you have done this? How do some of the other types of mounts attach to the tripod if not by a central bolt? If you bolt the pier top down, how do you secure the mount to the pier if it has a central bolt?
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  #9  
Old 13-04-2017, 01:38 PM
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One way of doing this:
http://www.iceinspace.com.au/forum/a...e.php?a=105341
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  #10  
Old 13-04-2017, 06:12 PM
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Rally,

Seeing that pier and scope mounting systems are a hobby thing and there are no actual building standards to go by, I can only make my comments from personal experience.
My pier was put in as a temporary quick fix and is very light weight in comparison with most that I have seen on this forum. Minimal concrete used , but my ground is hard compacted sandy loam. Top plates are 8mm thick and rat cage bolts 10mm. The only vibration spike that I have been able to detect is when the dog has barked next to the pier, the walls of my pier tube are too thin and sharp noise resonates there. I have since constructed a shorter pier with a thicker steel tube that doesn't seem to have that issue. Considering how many people here have rats cages as part of their pier that there would be more comments about their unsuitability for the purpose? The weakest link still is the single central bolt holding the mount and scope down.


Quote:
Originally Posted by rally View Post
Rick,

The strength requirement of a pier is the easy part of the pier design, and what you say is true.
But the other main function of a pier (at least for astrophotography) is also to transmit any and all movement and vibration to the ground, that requires much greater rigidity, which has the unnecessary byproduct of being over engineered as far as strength is concerend.

So there is a point to it, but its not for strength.

Of course if there are weak links in the chain - eg rats nest on little M12 threaded rods, mount backlash and high PE then the quest becomes less useful, but its all about progression, so building the cheapest part of the system (pier) to be a strong link rather than a weak link makes sense as you are only arguing about loose change by comparison.
Maybe $50-100 or less and a bigger hole = more labour !
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  #11  
Old 13-04-2017, 07:26 PM
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Here's a possible solution to the problematic altitude adjustment and mounting system for Heq5 and Neq6 mounts. This mount has an outer sleeve that fits over the pier tube and is locked after ra adjustment with 3 bolts.
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  #12  
Old 14-04-2017, 08:43 AM
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Quote:
Originally Posted by bojan View Post
Hi Bojan, that is the most common method and a variation of the general theme. I was trying to draw out the OP to view his solution.

Nice pier and top by the way.
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  #13  
Old 14-04-2017, 09:07 AM
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Quote:
Originally Posted by Bart View Post
Can you provide a picture of how you have done this? How do some of the other types of mounts attach to the tripod if not by a central bolt? If you bolt the pier top down, how do you secure the mount to the pier if it has a central bolt?
I used the central bolt fixing of the head of the tripod, that was fixed to a plate that goes on the top of the hollow pier. inside the pier there are four steel plates that are welded to flush with the top edge of the pier these are tapped and than the plate with the mount attached is bolted on the pier.
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  #14  
Old 14-04-2017, 10:19 AM
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With a rats cage you can loosen the central bolt to make fine adjustments on the RA axis for precise tracking, this would not be easy with the fixed plate system, you would still need a hole in the side of the pier to at least fit a spanner to loosen and tighten the bolt.
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  #15  
Old 14-04-2017, 10:49 AM
AndrewJ
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Gday Rick

Orrrr....., you can make the plate that attaches to the mount similar to a wedge base. Ie you have three or 4 slotted holes in the baseplate so that it can rotate on the pier head, and also add new az adjust screws to allow it to be tweaked in azimuth. ( ie ignore using the Az adjust bolts in the mount itself ).
Then bolt the mount securely to the plate and fit it flush with the pier.
To adjust in Az, you loosen the 3..4 hold down bolts and rotate the plate using the new adjust mechanism. This also allows for a longer lever arm and a finer bolt pitch, which gives a much smoother and finer resolution.

I did something like this when i made a small pier extension that could take either my AZEQ5 or EQ6 and i needed to fit it to my pier head which is designed to mount my homemade wedge. The Az adjust pillars are on a different radius between the mounts and this made using a std pier extension rather difficult. So i thunk outside the square
In the piccy, the alloy plate sits on some laminex and the Az adjust mechanism is designed to match the wedge position.
The pierette is then held onto the pier using a single centre bolt extension and is done up hard. Moving the new plate in Az then rotates the pillar.
Alt adjusts are done as normal, but Az adjusts get done by the new mechanism, which easily rotates under load given the fine thread used and longer lever arm.
Works like a charm

Andrew
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  #16  
Old 14-04-2017, 01:43 PM
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traveller (Bo)
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Quote:
Originally Posted by Bart View Post
Hi Bojan, that is the most common method and a variation of the general theme. I was trying to draw out the OP to view his solution.

Nice pier and top by the way.
Maybe he did something like this?
http://www.iceinspace.com.au/forum/s...d.php?t=136618
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