Cages on piers?

[SimmoW]

Hi folks, I'm thinking of getting a pier custom built by a trusted contact.

Many ppl use a cage to fine tune levelling. This concerns me due to possible flexure. Are my concerns valid? Is it possible to have a perfectly horizontal base? Does it matter nowadays if it's not perfectly level?

Thanks in anticipation of any comments/ideas.

[Lognic04]

Levelling is not important at all for an equatorial mount because you polar align anyway, which aligns you to the pole. If you are using an alt-az mount then levelling becomes important.

A "cage" doesn't seem very secure to me either...20,30kg suspended on 4 narrow bolts, kinda gets rid of the whole point of the pier!

:thumbsup:

[billdan]

Big argument on Cloudy Nights at the moment, on this subject.

Here is the link if you want to be more confused.

https://www.cloudynights.com/topic/610052-for-those-using-rat-cage-design-for-those-selling-them-got-vibrations/

Cheers
Bill

[Merlin66]

Simon,
I built an extended pier for a NEQ6 pro head. I used a SW extension and used a central bolt to “lock” in to the top of the pier.

It’s been in action for the last two years, no issues, no drama.

[SimmoW]

Sorry Ken, so you mean you haven't used a cage?

Thanks a heap Bill, I think!

I must read it in any case, esp to convince myself of advantage of the equatorial mount

[glend]

There are a lot of piers around with cages of some sort. If you are pouring your own concrete pier the placement of the J bolts and angular spacing may not be very precise. A cage used in that situation provides a good way of presenting a load equalisation platform for your mount adaptor. Of course extreme cages are not a good idea, and mine is minimal height off my poured pier. Levelling is not important for EQs but good weight distribution and support is important. There are hundreds of piers with cages, and as long as they are designed to support the equipment used they are ok. That said, cages should not be used as pier extensions imho, there are better choices (like pipe sections).

[Merlin66]

Simon,
No cage. The SW extension bolted directly to the pier then the NEQ6 head to the top.
No issues, no drama.
It currently holds a C11 and spectroscope etc.

[h0ughy]

so this pier has everything wrong going for it http://www.iceinspace.com.au/forum/attachment_browse.php?a=201477

and http://www.iceinspace.com.au/forum/attachment_browse.php?a=201478

http://www.iceinspace.com.au/forum/attachment_browse.php?a=201478

[Merlin66]

No, I'm not saying that....just that a SW pier extension mounted on a central M12 x 1.75mm bolt works just as well.

[LostInSp_ce]

That's a nice setup Ken and the Nintendo controller is a nice touch. Simon I'm currently in the same boat as you but with the advice of a very helpful member in here this is what I decided to do. It's an old gas pipe with a cut out to allow the tightening of the adaptor plate bolts. Hopefully it will serve me well for years to come. The next step is figuring out what type of observatory to build around it :question:

[Kunama]

The 'rat cage' is fine provided that you use decent sized plate and bolts and keep it as short as possible.

I built a 1200mm high pier for Phil's observatory using 220mm OD pressure pipe with a 9.5mm wall thickness. The base plate measured 350mm square by 16mm thick. The top plate and adapter plate are 12mm thick steel. The adapter plate is installed with M16 stainless steel bolts and sits only about 50mm above the top plate.

This pier weighed a mere 85kg and carries an EM400/Mewlon300 etc, it does not move....

[doppler]

Apparently mine setup is completely unsuitable in all aspects. A single wheelbarrow full of concrete for the footing (no reo), a 1200mm high pier with 1.5mm thick walls (sand filled), a rats cage with m10 bolts and a 10" newt (15kgs with full kit) on a Heq5 pro.
This is doing everything wrong and should be vibrating like crazy according to some experts ,so I'm puzzled as to why it works so well. The only vibration I can notice is from the wind, fortunately when it's clear here it's usually very still. My ground is hard packed sandy decomposed granite so there is no vibration coming up through the pier.

[I.C.D]

Hi Simon I take you are talking about a base for a pier ,if you check this site out I have seen one of those over at Ilford last year the one they put was equal to 4 cubic meters of cement and if you move house you can reclaim it and take it with you
Ian
https://surefootfootings.com.au/

[traveller]

As others said Simon, no need for perfect leveling every time, so a cage free pier should be fine.
I have a similar setup as Ken's see this thread http://www.iceinspace.com.au/forum/showthread.php?t=136618
Bo

[OICURMT]

Which in turn references... http://www.iceinspace.com.au/forum/showthread.php?p=855252

[AndrewJ]

Been watching this thread and the one on CN.
The whole problem is moot unless you have something that will cause "resonant" vibrations in the first place, ie wind, mount motor or ground based, and you need to define that first.
Dealing with an "oops i bumped the mount" moment cannot be handled by any sort of mounting ( and is not cost effective )
Also you need to look at the problem as an entire chain, and doing vibration analysis on something like that is soooooooooooo difficult in theory, as to be almost impossible.
In my case, if i have my 10" Meade LX200 on a wedge, a rat cage would be the least of my problems.:)
The only way to truly "test" if you have problems with your "entire setup" would be to fit a few accelerometers onto the bits and see what they report. Accelerometers are cheap as chips these days.
Also, as to requiring a large mass in the ground, i dont always think thats best, esp if you have ground vibrations.
To me, if you got a long piece of pipe and a hole borer/auger,
you could bore down say 2 metres and drop in the pipe and then backfill.
Its not going anywhere, and also has a much lower footprint for transmitting ground pressure changes ( moisture change or vibrations ) to it.
Have attached a piccy of an early pier i did this way with wood.
The hole i made was limited by my shovel size, but an auger would have been better. It never moved until it started rotting:rofl:
an old telgraph/electricity pole would be perfect

Andrew

[h0ughy]

can i add something else to the mix, please have a look at this link to an image provided by Martin Pugh now look at the base of the whole setup?

http://www.iceinspace.com.au/forum/attachment_browse.php?a=224876

[SimmoW]

Thanks for all the ideas and theory everyone! Can't see much reason for a cage at this stage

[el_draco]

So, you spend a fortune building a really solid pier, bury it in a ton of concrete and then hang all your gear on 4 bolts and few nuts? :question:

Its stating the bleeding obvious that this is not a good idea. You effectively negate all the effort below the rats cage. As someone else said, get the top of the pier pretty level and use the equatorial head adjustments to fix the rest.

[RobF]

+1
Decent bolts and plate not set too high is fine for EQ6 style loads. Its nice to have easy access to lower bolt. Vibrations very likely far less than tracking and seeing errors for 99.99% of people.

[DarkArts]

These vids are probably well known to many. I'm just adding them to prompt discussion, not to take a particular position .... though my pier design doesn't use a rat cage .... ;)

Anti-vibration observatory piers (Part 1, Piers: The good the bad and the Rat Box) (https://www.youtube.com/watch?v=i1F4JUiZVec)
Anti-vibration observatory piers (Part 2, The foundation and fastening of the pier) (https://www.youtube.com/watch?v=4FrJziVWXbo&sns=em)