Pier ready!

[g0ibi]

Thanks to Gary1968 and his EQ5 pier top he made for me, my pier is Polar aligned and ready to use!

Plans are afoot to build an obsy over the Christmas break to complete my set up!

[Aoraki]

I'm having a little difficulty with piers at the moment, I need to fabricate one soon and the research I have done seems to steer me away from the threaded bar/adjustable top plate. Could I ask why you have gone down the adjustable route and not the solid top? What if any, are the advantages of your set up over the solid/fixed top plate? The disadvantage appears to be flexure, although you look like you are using M16 so that should help.

[malc-c]

There is the old argument that an EQ mount is best leveled. Irrespective of which side of the fence you sit on this debate, having a top plate that is adjustable by three or four bolts does give you that ability if you wish to have a level base on which to bolt the mount

[spaceboy]

I agree it adds to flex but I doubt no more so than what you get from the average mount anyway. As long as you use the best and most rigid bolts you can practically use I don't foresee any problems. This said I have seen some amazing piers created with "tons" of steel and concrete only to be finished off with 3 M12 bolts holding the mount. There is a formula some where for judging how deep a post should fix into the ground given it's height. The calculations also determine how wide the post should be to reduce any loss of strength. I think this is more for construction purposes but I guess it could be related to telescope piers if you wanted to go to those extremes. Either way how you actually attach the mount to the pier is as you say as important as the pier itself. In the case of a 6" drain pipe filled with concrete I doubt there will be that noticeable a difference between mounting it directly to the pier over raising it up on 3-4 substantial bolts. The only exception being it will be easier to level the mount.

[g0ibi]

I have used this top (thanks Gary1968!) for adjustability as well as strength, I am using a EQ5 Goto with a SW 200DPS for visual only. I was not able to site it anywhere else but on a 7" thick concrete floor (Built 1938) so weight and size had to be considered! Pleased with the result though!

[Gina]

If you have a concrete pier you have to have some way of attaching the pier adapter. Four thick rods or bolts provide a very solid connection. I did some testing with my NEQ6 mount and the mount was the weak link by a long way. I was unable to induce any measurable movement up to and including the adapter but there was a small amount of movement in the mount itself - even this monster isn't perfect and there are much more expensive mounts used for bigger scopes that will "knock the EQ6 into a cocked hat".

[Zakalwe]

I personally do not believe in this flex nonsense.......has anyone actulayy tried to bend a 16mm bolt that is 75 mm long?

[spaceboy]

I don't think it's flex per say. More so the fact that a 6" solid pier is reduced down to a cross section of only 48 mm in the case of 4 x M12 bolts. Where as if the mount was attached directly to the pier it would retain the 150mm eliminating the possibility of "any" weakness introduced by other mounting methods.

[malc-c]

I don't think it's flex per say. More so the fact that a 6" solid pier is reduced down to a cross section of only 48 mm in the case of 4 x M12 bolts. Where as if the mount was attached directly to the pier it would retain the 150mm eliminating the possibility of "any" weakness introduced by other mounting methods.

But how would you otherwise attach the mount to a tube full of concrete ?

[g0ibi]

There seems to be an awful lot of 'overkill' on piers and mountings and yet many get by on a flimsy tripod without any problems!!

[g0ibi]

Scope mounted on pier, just need this high cloud to clear!!!

[Aoraki]

But how would you otherwise attach the mount to a tube full of concrete ?

Resin anchors

[rawhead]

Looking very nice

One of my biggest bugbears was accidentally booting the tripod. Meticulous polar alignment right up the swanny!

[Aoraki]

I personally do not believe in this flex nonsense.......has anyone actulayy tried to bend a 16mm bolt that is 75 mm long?

It's really not that hard to induce flex in a M16 bolt, even at 75mm long. We are after all moving upwards of 10~15 kg about in all manor of ways. A couple of thou at the mount will be a fair amount by the time you get to some far away galaxy.

[Zakalwe]

It's really not that hard to induce flex in a M16 bolt, even at 75mm long. We are after all moving upwards of 10~15 kg about in all manor of ways. A couple of thou at the mount will be a fair amount by the time you get to some far away galaxy.

Really? Try it....get a 16mm threaded bar and mount it in a vice. Then try and get it to move by swinging on it. When you've finished exhausting yourself, get 2 bits of flat plate separated by 16mm threaded bar. See how much "flex" you can get into that.

Believe me, it is not going to budge.

<edit> As a matter of interest, a 10Kg force acting on the end of a 100mm long, 16mm steel pin will result in a deflection of 0.05 millimetres. Thats 1/50 of a millimetre, or one half the width of a human hair. Now imagine 3 x 16mm bolts separating two steel plates. It aint going to move.

Formula:

MI for Solid Round = (PI * Diameter4) / 64

Deflection = (Length3 * Force) / (3 * E * MI)

Bending Stress = (Force * Length) / (MI / (0.5 * Height))

Where,

MI = Moment of Inertia

E = Modulus of Elasticity in psi

[Aoraki]

I own a welding and fabrication business. I produce items from small brackets to structural steel. I use threaded rod etc weekly. I CAN produce flex quite easily in M16 rod.

Flex and twist of bar and plates will occur, it is inevitable. Your example above is not the whole story; you are looking at 10kg on the end of a 100mm bar. A scope, finder scope, camera and DSLR are not mounted at 100mm from the top of the adaptor plate but more like 300/400mm so the total movement in considerably more.

I’m not one for formulas as “real world situations” are what matter to me.

It seems like we must agree to disagree.

PS Although we are assuming M16 in the piers/photo's in this thread, a lot of the adaptors I have seen on this and other forums appear to be M12 therefore making the situation worse. If you remove the adjustors completly, there will be NO flex apart in the pier itself.

[spaceboy]

But how would you otherwise attach the mount to a tube full of concrete ?

A steel plate. The center fixing bolt is counter sunk so as not to cause an obstruction and the plate is then mounter flush to the pier in the same way you would an adapter. It makes AZI adjustment for PA a little tight but if you have a pier it's rare you'd need to make this adjustment very often once done anyway.

But as I said before on a 6" concreted drain pipe it's pointless. The diameter vs length often means a 6" pier will vibrate like a tuning fork. Might only be the most minute of vibrations but the stars in view will be dancing around like little tinkerbell's.

[g0ibi]

Tested last night, no Tinkerbells!

[damnut]

Hi g0ibi,

That looks like a fine bit of kit, hoping that I have earned enough brownie points to put a pier in for my SCT next year.

Clear Skies

[spaceboy]

Tested last night, no Tinkerbells!

Sorry g0ibi if you got the impression I was referring to your pier. I was making a point to those that could be considered some what over kill. Half a cement mixer load holding it in the ground and more steel than the Eiffel tower just to be topped off with 3 x M12 bolts.

I personally think you have done a great job on your pier and I have a similar set up myself http://stargazerslounge.com/members-equipment-gallery/153723-my-take-eq6-pier-adapter.html I've always found the pier itself to be the weaker link in my case as there simply isn't enough girth to absorb vibration effectively. Given the chance again I would have done things a lot different but when your starting out any pier is better than having to keep setting up tripods.

[malc-c]

Resin anchors

Just googled that as I've never come across this. Whilst it seems that resin anchors are used where the brickwork or material the anchor is being used is too soft to get a decent purchase, they are still in effect bolts which are screwed into the brick / concrete.

Due to the nature of having to secure the mount to a plate, and then that plate to the pier, I can't see any advantage of using resin anchors over sinking three or four 24" lengths of threaded rod into the wet concrete, and then using three more lengths to secure the top plate. Whilst using 12mm - 16mm rod between the base plate and top plate may not be ideal, and can be improved by using larger diameter threaded rods, as been mentioned, it's probably has less flex than a standard EQ5 tripod !

[Gina]

There's much less flexing than an EQ6 mount even - I've tested it!

[spaceboy]

Again I think we have all made the mistake of referring to it as flexing (myself included) It's vibration we are trying to avoid. Vibration resonates through a thin bar where a thicker bar dampens it. The shorter the length of a thin bar the better as the thinner bar is often attached to a larger structure and the vibration is transfered quicker into this. Needless to say what the larger structure is made of also determines how well the vibration is suppressed. As I mentioned above I doubt this really applies to those of us who are using the 6" drain pipe method. I felt it was worth bringing up for those reading the thread considering a drain pipe pier and that they really don't need to over spend on tons of concrete and steel just to top it off with 3 x M12 bolts. It just "reduces" the cross section and so the dampening properties of the pier. No matter how many bags of concrete you put in the ground to hold the pier the 3x bolts will introduce a weak link. I'm looking to save members money if anything by arguing this point.

[Jessun]

Spaceboy I agree! I intend to save that money one day!

As long as the polar axis of the mount is aligned with the the celestial pole then job done - and the mount can be adjusted to achieve this - it's already 'misaligned' from the ground when you set the latitude to your location isn't is? Worst case you need to move the setting circles accordingly if you intend to use them. Leveling is not needed. Look at some of the bigger piers, they are even angled at the top allowing for huge scopes to effectively hang off it! We agree on this.

I wonder tho how much 'bolting it up' really matters in terms of vibrations etc put against seeing and wobbly guide stars tube flexing and other bending parts. Perhaps the thruth is the bolts gain nothing, but neither do you lose anything really all things considered? Apart from some time and cash :-)

So in short I am still very jelous of the piers in this thread, nice work! Wish I had one too!!

/Jesper

[Zakalwe]

Vibration resonates through a thin bar where a thicker bar dampens it.

..... the thinner bar is often attached to a larger structure and the vibration is transfered quicker into this.

Have you got any evidence of this (other than "common sense" or anecdotes) or sources to verify this?