Steel Pier Construction

[Ibbo!]

14 minutes ago, ollypenrice said:

Here's a levelling thought experiment: precisely polar align your mount on a perfectly level pier. Now run a tight fitting steel shaft through the RA axis and bolted at one end to the floor and at the other to the obsy wall. It will get in the way but this is a thought experiment! ) Your PA is now absolutely fixed by that shaft, agreed? Nothing can can move it. Now unbolt your pier from the floor and loosen the alt-az adjusters on the mount. You can point the pier wherever you like. It can slope forwards, backwards and sideways without in any way affecting your PA.

For the more practically minded, this is a very expensive Takahashi tripod for their equatorial mounts. Notice anything missing?

Olly

 

Nope nothing missing there, unless you count the flagstone for higher latitudes ??

[souls33k3r]

Please don't forget to answer my question while we're all having fun with the levelling discussions

[Gina]

It doesn't pack up very small...

[Gina]

When I built my first pier I did level the top but that was before I found out it wasn't needed.  My second pier doesn't have any method of levelling.

[adyj1]

1 hour ago, souls33k3r said:

 

You make a fair point, but as a consolation, this has been a quite emotive subject at times and your thread (or the misuse therein) has provided a light-hearted platform for this disxussion... Apologies for the misuse*. 

Whilst I can offer theoretical advice on your questions, I'm actually lurking on this thread because I am constructing a cheap steel pier myself (out of an I-beam), and am also looking for advice from the more experienced members who have done it for real.

Personally, I'll be going with the pier flush with the concrete as it is easieat/cheapest for me. Neither seems unstable if done properly. 

Similarly for the shape of those fins. Both will make it more stable - I expect the tapered fins are the slightly better option, but the rectangular ones will be well within tolerances...

As I said - hopefully someone with useful advice will be along soon ? 

Ady

*If we meet at a star party, I owe you a beer

[souls33k3r]

3 minutes ago, adyj1 said:

You make a fair point, but as a consolation, this has been a quite emotive subject at times and your thread (or the misuse therein) has provided a light-hearted platform for this disxussion... Apologies for the misuse. 

Whilst I can offer theoretical advice on your questions, I'm actually lurking on this thread because I am constructing a cheap steel pier myself (out of an I-beam), and am also looking for advice from the more experienced members who have done it for real.

(personally, I'll be going flush as it is easieat/cheapest for me - I think over-engineering is OK, but only if you've got the budget...) 

Ady

 

Don't get me wrong, the thread has not been misused but rather provided some great insight but i guess Olly with his imaginary shaft example made it super clear. Makes complete sense

But i also do not want this thread to move away from the fact that i have some questions along the way  You're more than welcome to ask any questions if you like using this thread. 

[spillage]

Yep not they have had your mount and ota away but not to worry...you still have the magical levitating tripod.

[ollypenrice]

1 hour ago, souls33k3r said:

Don't get me wrong, the thread has not been misused but rather provided some great insight but i guess Olly with his imaginary shaft example made it super clear. Makes complete sense

But i also do not want this thread to move away from the fact that i have some questions along the way  You're more than welcome to ask any questions if you like using this thread. 

My point was to urge you to forget about ratboxes and owls' nests and all the snake oil of that salesman bloke in the infamous video who coined the term ratbox in the first place. Just make yourself a nice strong pier with a top that's fairly flat and enjoy the perfect pier. Don't solve problems that don't exist. There are more than enough which do!

Olly

Edit: I have lambasted this unknown person on previous occasions but whoever decided that mounts should be attached to top plates from below should have his SCT dewheater turned off for a year. There is no need for it and it introduces an entire ratbox of owls' nests.

 

[ollypenrice]

1 hour ago, Ibbo! said:

Nope nothing missing there, unless you count the flagstone for higher latitudes ??

Shrewd, very shrewd... 

Olly

[JamesF]

1 hour ago, adyj1 said:

Personally, I'll be going with the pier flush with the concrete as it is easieat/cheapest for me. Neither seems unstable if done properly. 

Similarly for the shape of those fins. Both will make it more stable - I expect the tapered fins are the slightly better option, but the rectangular ones will be well within tolerances...

Pretty much agree with this.

In the case of the "fins", the tapered ones are all that's required, if indeed they're necessary at all, but I see no reason that rectangular ones should not work just as well.  I suspect rectangular ones may be more prone to catching on passing clothing and cables however.  At the very least I'd be tempted to round off the exposed corner a fair bit.

As to whether they are actually necessary at all, perhaps a materials scientist could tell you given a suitable understanding of the load on the top, but my suspicion is that they aren't unless you've gone for a relatively narrow or thin-walled pier tube.  I feel sure matey-boy from the astronomy and nature centre or whatever it used to be called said in some of his videos that they were required to stop the pier vibrating or "ringing" if it were hit, but my feeling is that it's cheaper and easier, not to mention less painful, if you just don't kick the pier whilst you're imaging.

James

[Gina]

If I'd had the EQ8 when I built my observatory and pier it would have saved an enormous amount of work compared the NEQ6 I had at the time.  The ED8 mounts on a nice simple flat base unlike the NEQ6 which has a "lump" in the middle and mounts with a centre bolt.  I also made the mistake of building the concrete pier too low so I still need the four M14 studs to raise the mount to working height.  However, the mount is well stable enough for the smallest DSO with a metre focal length telescope and high resolution image sensor.

[Astrokev]

1 hour ago, ollypenrice said:

My point was to urge you to forget about ratboxes and owls' nests and all the snake oil of that salesman bloke in the infamous video who coined the term ratbox in the first place. Just make yourself a nice strong pier with a top that's fairly flat and enjoy the perfect pier. Don't solve problems that don't exist. There are more than enough which do!

Olly

Edit: I have lambasted this unknown person on previous occasions but whoever decided that mounts should be attached to top plates from below should have his SCT dewheater turned off for a year. There is no need for it and it introduces an entire ratbox of owls' nests.

 

Yes, his videos were quite entertaining. Most of it was utter nonsense as I recall, with liberal use of terms that were, I'm sure, previously unknown to mechanical engineers. Is he still around, or in hiding somewhere?

 

[Astrokev]

3 hours ago, ollypenrice said:

Here's a levelling thought experiment: precisely polar align your mount on a perfectly level pier. Now run a tight fitting steel shaft through the RA axis and bolted at one end to the floor and at the other to the obsy wall. It will get in the way but this is a thought experiment! ) Your PA is now absolutely fixed by that shaft, agreed? Nothing can can move it. Now unbolt your pier from the floor and loosen the alt-az adjusters on the mount. You can point the pier wherever you like. It can slope forwards, backwards and sideways without in any way affecting your PA.

For the more practically minded, this is a very expensive Takahashi tripod for their equatorial mounts. Notice anything missing?

 

 

I like thought experiments, but one could argue it's no easier than imagining fixing the pier, then loosening the alt-az adjusters, which allows you to move the PA wherever you like. I guess it depends on which frame of reference you find easiest to visualise. ?

[JamesF]

15 minutes ago, Astrokev said:

Yes, his videos were quite entertaining. Most of it was utter nonsense as I recall, with liberal use of terms that were, I'm sure, previously unknown to mechanical engineers. Is he still around, or in hiding somewhere?

"In hiding" in Sweden where he opened another telescope shop, I think, assuming we're talking about the same chap.

James

[Astrokev]

2 minutes ago, JamesF said:

"In hiding" in Sweden where he opened another telescope shop, I think, assuming we're talking about the same chap.

James

Yes, the astronomy and nature centre chap. Loved his videos for a good laugh, but I'm sure some may have been taken in and persuaded to part with hard-earned cash for his over-engineered piers.

[souls33k3r]

5 minutes ago, JamesF said:

"In hiding" in Sweden where he opened another telescope shop, I think, assuming we're talking about the same chap.

James

Thou shalt not be named ... or we can if there's a massive itch ?

@ollypenrice hehehe don't worry, i'm off the levelling horse

1 hour ago, JamesF said:

Pretty much agree with this.

In the case of the "fins", the tapered ones are all that's required, if indeed they're necessary at all, but I see no reason that rectangular ones should not work just as well.  I suspect rectangular ones may be more prone to catching on passing clothing and cables however.  At the very least I'd be tempted to round off the exposed corner a fair bit.

As to whether they are actually necessary at all, perhaps a materials scientist could tell you given a suitable understanding of the load on the top, but my suspicion is that they aren't unless you've gone for a relatively narrow or thin-walled pier tube.  I feel sure matey-boy from the astronomy and nature centre or whatever it used to be called said in some of his videos that they were required to stop the pier vibrating or "ringing" if it were hit, but my feeling is that it's cheaper and easier, not to mention less painful, if you just don't kick the pier whilst you're imaging.

James

yeah i always did wonder if those fins did made any sense or not.

[souls33k3r]

Just thinking out loud, what if one fills the pier with some gravel? Is that a good idea for extra stability or not?

[JamesF]

My recollection from reading an article years ago on pier design is that diameter is far more relevant in terms of the pier's resistance to deflection than anything else.  Filling it with gravel (or sand) won't make an enormous difference.  I'd suggest that if you're sufficiently worried to think it might be helpful to fill it with something, just have it made an inch larger in diameter and not worry.

James

[Xplode]

4 hours ago, souls33k3r said:

Great discussion and lots to think about. Cheers guys.

One question though, does the base plate of the the pier have to be flush with the concrete when putting it in? 

Also thinking about eliminating vibrations, i see some fins are placed around the pier. Do they have to be in a right angle triangle (figure 1) or can they be a right angle rectangle (figure 2)?

 

If you decide to make the extra effort to add fins you should make them as in figure 1, why? Since they aren't equal from top to bottom they can help eliminate oscillation created by vibrations.
In my opinion it also looks a lot nicer, but it's not really needed if the rest of the pier is made well enough.

You might also want to think about anything you might want to mount on the pier, focus controllers, PSU's, cable management etc.
If you got access to a 3D printer there's enless possibilites. Here's some brackets for a control box, cable management tube and handpad i made.

Here's an image of the top of the pier i made for a friend, it's a ~180cm heavy steel pier, around 95kg and it's sitting on top of a ~3m concrete filled "chimney".
The steel pier is filled with sand.

It was originally made for a Takahashi EM500 mount which can only be adjusted to 40-50 degrees so the original pier had an angle, it was cut and a steel plate was welded on to fit the 10 Micron GM2000.

[JamesF]

10 minutes ago, Xplode said:

If you decide to make the extra effort to add fins you should make them as in figure 1, why? Since they aren't equal from top to bottom they can help eliminate oscillation created by vibrations.
In my opinion it also looks a lot nicer, but it's not really needed if the rest of the pier is made well enough.

Quite.  This is really the point: if the pier tube is adequately sized in the first place, it will not vibrate enough for the effects to be visible at the eyepiece or on the camera sensor.  And in fact, there's very little that's going to cause it to vibrate unless you sit there smacking it with a lump hammer.

James

[ollypenrice]

I read that a blend of sand and oil was a good damping filler. I think we are solving non existent problems again...

Olly

[souls33k3r]

True, like I said I was just thinking out loud. Not worried at all, just making sure I've answered all those questions that are coming to my head and without complicating any of this build. 

Now all what I need is a few days off so that I can start digging and get this bad boy up. 

[Davey-T]

The biggest problem I have with my garden pier is snails crawling up it, tried copper tape which is supposed to deter them but obviously nobody told them 

Dave

[souls33k3r]

20 minutes ago, Davey-T said:

The biggest problem I have with my garden pier is snails crawling up it, tried copper tape which is supposed to deter them but obviously nobody told them 

Dave

I'm sure I've seen a repellent spray that you can spray around and on the pier. I must look at this. Good shout Dave, I totally forgot to factor this in. 

[bottletopburly]

5 hours ago, ollypenrice said:

I read that a blend of sand and oil was a good damping filler. I think we are solving non existent problems again...

Olly

I assume the oil was to stop ants ? apparently they’re not keen on oil , sand they love ??