Pier Base Setup

[CDKPhil]

I have Just found out that I will not be getting my tripod for the MX until March (if I am lucky ). The mount arrives on Monday, so I will have nothing to put it on. I do not want to wait till March to try out the MX so I thought I would put a pier in.
I have read in other threads that people use a solid block of cement about 1m3 for the base.
I was wondering instead of digging one big hole and filling it with cement and steel, I could use a post hole digger and put five columns into the ground?
One in each corner and one in the middle and a slab across the top, to join them together.

The dimensions of the columns would be 300mm dia by 1300mm deep and the slab would be 1000mm x 1000mm x 200mm. All re-enforced with steel.

I am not an engineer so I am asking would this be better than one big hole?

I did some quick calculations and the surface area in contact with the ground would be slightly more with the columns and it would use less cement than a hole that is 1m3.

All advice is much appreciated.

By the way I have a tractor to drill the holes

Cheers
Phil

[gregbradley]

If you are using a tripod mount a simple slab would be fine.

If you plan to do a pier fixed to the slab then a 1 metre deep x 1m cube and slab on top separated from the rest of the floor would be the go. Reinforce it with steel.

My observatory is built that way and the pier is rock solid.

You don't do one big floor slab as walking, vibrations etc can transmit to the scope.

Several piers into the ground conneted to one top slab as you mentioned sounds like it would work as well. But its mass you want so a M3 of steel reo in concrete and a pier bolted to that would be pretty hard to beat.

I have pavers for floor around my pier slabs so vibrations do not transmit to the pier concrete block ( a gap where they meet the pier).

Greg.

Originally Posted by CDKPhil

I have Just found out that I will not be getting my tripod for the MX until March (if I am lucky ). The mount arrives on Monday, so I will have nothing to put it on. I do not want to wait till March to try out the MX so I thought I would put a pier in.
I have read in other threads that people use a solid block of cement about 1m3 for the base.
I was wondering instead of digging one big hole and filling it with cement and steel, I could use a post hole digger and put five columns into the ground?
One in each corner and one in the middle and a slab across the top, to join them together.

The dimensions of the columns would be 300mm dia by 1300mm deep and the slab would be 1000mm x 1000mm x 200mm. All re-enforced with steel.

I am not an engineer so I am asking would this be better than one big hole?

I did some quick calculations and the surface area in contact with the ground would be slightly more with the columns and it would use less cement than a hole that is 1m3.

All advice is much appreciated.

By the way I have a tractor to drill the holes

Cheers
Phil

[CDKPhil]

Thanks Greg, that sounds like good advice.

I thought of using the post hole auger because that saves me a lot of digging.
But if it is mass it needs then it is mass it will have.

I read on the SB website that just bolting a pier to cement can cause vibrations if the cement is not perfectly level and the pier is not grounded properly.
SB recommended using treated ply, I don't think wood left in the elements will last very long, treated or not. I guess it would be fine in a sealed environment. here is the link https://www.bisque.com:443/help/para...nent_piers.htm
So I was thinking of using a levelling compound, to make a perfectly flat surface.




Thanks

Phil

[mikerr (Michael)]

Phil, I mounted my pier to a concrete water tank as shown. The spacer nuts between the bootom plate and pier are used for levelling
.

http://img.photobucket.com/albums/v4...RONOMY/032.jpg

http://img.photobucket.com/albums/v4...RONOMY/019.jpg

http://img.photobucket.com/albums/v4...RONOMY/036.jpg

http://img.photobucket.com/albums/v4...ewChair002.jpg



Michael

[CDKPhil]

Originally Posted by mikerr

Not tellingPhil, I mounted my pier to a concrete water tank as shown. The spacer nuts between the bootom plate and pier are used for levelling
.

http://img.photobucket.com/albums/v4...RONOMY/032.jpg

http://img.photobucket.com/albums/v4...RONOMY/019.jpg

http://img.photobucket.com/albums/v4...RONOMY/036.jpg

http://img.photobucket.com/albums/v4...ewChair002.jpg



Michael

Nice job Michael, I only wish I had a nice big tank to bolt a pier on.
Alas I have to start from scratch.

I have started digging out today. I am building the footing on the side of a very steep bank. I have to use Gabion cages to form retaining walls. I will end up using about 2m3 of concrete. The footing will be about 2m deep.
It shouldn't move.

I will post some pictures to show the progress.

cheers
Phil

[gregbradley]

2 metres deep should be plenty. Mine is about 900mm deep and 800 x 800 with quite a bit of steel in it then the top was raised about 100mm with the final top part more like 1.2metre square so there was a flange in concrete on top. That may also be helping to prevent movement.

I think what SB are saying is the bottom of the pier needs to be supported and not sticking in the air. I anchor bolted my pier to the slab and then I levelled it with packing pieces. Then I put sand/cement mix under the pier to pack it up.

You can get nonshrinking grout that is good for that purpose. I believe it can be quite liquid so you could flow it under the plate. Stone masons use it to grout big blocks of sandstone that are in place on a building so its good stuff. In my case sand/cement shoved under with a trowel and smoothed off worked really well and my pier is well supported.

It makes sense to ground the pier well as Brendan could tell you, it would be a waste of the strength of that deep pier if you allowed flex from the weak point which is where the pier attached to the pier slab.
That base plate needs to be well supported with no air gaps and lots of anchor bolts nice and tight. That's where the slots are handy as you need to know which way is the south celestial pole before you fix it down hard otherwise unless you have a rotating pier adapter you may not have your mount close enough to the south celestial pole to achieve polar alignment. So mark that out on your pier before you install anchor bolts.

Greg.

[CDKPhil]

Originally Posted by gregbradley

That's where the slots are handy as you need to know which way is the south celestial pole before you fix it down hard otherwise unless you have a rotating pier adapter you may not have your mount close enough to the south celestial pole to achieve polar alignment. So mark that out on your pier before you install anchor bolts.

Greg.

Good point, I was going to use a plumb bob and get the shadow from it.
Wouldn't want to go to all that effort and have it facing east. I am sure it has been done before.
Here are a few pics on my effort today. Still a long way to go. I want to have the cement poured by the end of this week.


Cheers
Phil

[gregbradley]

Originally Posted by CDKPhil

Good point, I was going to use a plumb bob and get the shadow from it.
Wouldn't want to go to all that effort and have it facing east. I am sure it has been done before.
Here are a few pics on my effort today. Still a long way to go. I want to have the cement poured by the end of this week.


Cheers
Phil

Looking good.

Greg.

[CDKPhil]

I poured the concrete this morning. The footing size ended up being 910x870x2400. I had to dig down through quite a bit of fill to find the bedrock. I ended up using about 2.2m3 of concrete.
I used 18mm MDF for the form work, that will come off in a couple of days.

Now all I have to do is finish the gabions and back fill.


Cheers
Phil

[jenchris (Jennifer)]

Holy snapping crocodiles Batman - that is some lump!

[mswhin63 (Malcolm)]

Nicely done, no vibration on you.

[mswhin63 (Malcolm)]

Do you intend on placing a pier on the concrete?

I am not sure but if you can further extend the concrete and use the concrete as the pier then vibration issue will be a lot less compared to a metal pier. Some of the equipment driving the mount can be fixed to the concrete as well.

[CDKPhil]

Originally Posted by jenchris

Holy snapping crocodiles Batman - that is some lump!

The location dictated that I use that much concrete. As Greg said its all about the mass.

Originally Posted by mswhin63

Do you intend on placing a pier on the concrete?

I am not sure but if you can further extend the concrete and use the concrete as the pier then vibration issue will be a lot less compared to a metal pier. Some of the equipment driving the mount can be fixed to the concrete as well.

I am going to place a pier onto the concrete. It will be a Software Bisque pier. It has a tube diameter of 254mm and base and top plate of 12mm. The mounting holes are pre drilled.

I thought about using concrete as a pier but decided against it. I am sure I read on another thread that a concrete pier will have more flex than a metal one. ( Don't quote me on this, I might have it backwards). I am sure there would be someone here that can clarify this.

As far as vibrations go, filling the pier with some sort of dampening material might work. I am not sure if this needs to be done or not. I will have to wait till I get the mount and the telescope setup and trial it.

Cheers
Phil

[mswhin63 (Malcolm)]

Originally Posted by CDKPhil

I am going to place a pier onto the concrete. It will be a Software Bisque pier. It has a tube diameter of 254mm and base and top plate of 12mm. The mounting holes are pre drilled.

I thought about using concrete as a pier but decided against it. I am sure I read on another thread that a concrete pier will have more flex than a metal one. ( Don't quote me on this, I might have it backwards). I am sure there would be someone here that can clarify this.

As far as vibrations go, filling the pier with some sort of dampening material might work. I am not sure if this needs to be done or not. I will have to wait till I get the mount and the telescope setup and trial it.

Cheers
Phil

I watched a video on vibration and myths associated with some mounts especially DIY that there are a few features that create more vibration than concrete or simply proper construction. Mind you this is an issue with some high end mounts and hard for me know if this is relevant if you use a low cost (EQ5/EQ6) mounts.

I for the life of me can't find the video as usual, but it uses simple holes in the base for mounting not elongated. Fins travelling from the bottom to the top and vary for form and cut off triangle (to prevent single resonance). and also does not use extended bolts for the mount cap (again resonance). Maybe someone else can find it.

The video was shown by an mount designer (can't remember the name) but mentioned in the video he knew that he was not going to worry about the DIY market which is the primary reason for creating the video.

[CDKPhil]

Originally Posted by mswhin63

I watched a video on vibration and myths associated with some mounts especially DIY that there are a few features that create more vibration than concrete or simply proper construction. Mind you this is an issue with some high end mounts and hard for me know if this is relevant if you use a low cost (EQ5/EQ6) mounts.

I for the life of me can't find the video as usual, but it uses simple holes in the base for mounting not elongated. Fins travelling from the bottom to the top and vary for form and cut off triangle (to prevent single resonance). and also does not use extended bolts for the mount cap (again resonance). Maybe someone else can find it.

The video was shown by an mount designer (can't remember the name) but mentioned in the video he knew that he was not going to worry about the DIY market which is the primary reason for creating the video.

That sounds interesting. I would like to see the video.

I wonder if you could use carbon fibre? I have a carbon fibre pushbike it is extremely strong and light. It is much better to ride on the road than a steel frame. It absorbs a huge amount of vibration, and still transfers a lot of power to the wheels. It is very stiff.
I would say it would be rather expensive to build a carbon pier. An engineer would have a good idea about the pros and cons of carbon fibre.

cheers
phil

[mswhin63 (Malcolm)]

Found the video it was actually in a thread recently posted-

http://www.iceinspace.com.au/forum/s...ad.php?t=84547

The videos listed here (to give credit to the person who found them for me)
http://www.iceinspace.com.au/forum/s...2&postcount=11

Personally i think concrete would have a slight dampening affect on vibration. but that also may depend on how thick it is and the mixture.

[CDKPhil]

Originally Posted by mswhin63

Found the video it was actually in a thread recently posted-

http://www.iceinspace.com.au/forum/s...ad.php?t=84547

The videos listed here (to give credit to the person who found them for me)
http://www.iceinspace.com.au/forum/s...2&postcount=11

Personally i think concrete would have a slight dampening affect on vibration. but that also may depend on how thick it is and the mixture.

Thanks for the link.
The video was very informative. At least I have the foundation for the pier right. The presenter said that 1m3 of concrete weighs 1 metric ton, but I think he has got this wrong. 1m3 of concrete would weigh 2000kg give or take a few hundred kg depending on the types of materials used. My footing would weigh well over 4000kg.

Looking at the specs for the Software Bisque pier, it seems they have a very different approach. The slotted holes, not a wide base plate compared to the diameter of the vertical shaft and there are no webs that run from the base plate to the top of the pier.
The only similarity would be the way the mount bolts onto the top plate of the pier.

So the question is, in practice which is the better pier?
To me the Astro Engineering pier looks to be a far better design.

Cheers
Phil

[gregbradley]

Wow, that sure isn't going anywhere!

Those stone walls - are they retaining walls? You're not building the observatory walls using them are you? They look like they'd retain a lot of the daily heat and radiate it up for hours in the night.

Lightweight walls would be the go. Timber or metal frame and colorbond with aircell insulbreak is what I used and it works great. During a hot day the observatory is reasonably cooler inside. I have it under the roof and walls and spray painted it matt black as it is silver otherwise.

What about roll off roof and wheels etc? That can be tricky and really affect the outcome.

My advice here is:

1. Ask on the forum for various systems as there are many ways of doing it.
2. Make sure the roof clears the scope so if the scope swings it can't hit the roof. Also that a truss horizontal member clears the scope.
3. Keep your walls parallel and work out the track system so the roof rolls off and closes fairly easily. If you go to Bunnings your wheel choices are very limited. Richmond Castors and wheels have lots and I think they have an online store. They are in Wetherill Park Sydney.
4. You could use 100mm C purlin for the track, it comes in 6.1 metre lengths. I'd ask around as there have been some nice systems here and mine has been a source of trouble.

Greg.

[mswhin63 (Malcolm)]

No worries Phil,

It is a difficult one to think about seeing I am currently not building a pier but always interested. I usually take a lot of time to mull over a project before commencing. I usually end up making a prototype and end up looking at the problems later.

[CDKPhil]

Originally Posted by gregbradley

Wow, that sure isn't going anywhere!

Those stone walls - are they retaining walls? You're not building the observatory walls using them are you? They look like they'd retain a lot of the daily heat and radiate it up for hours in the night.

Lightweight walls would be the go. Timber or metal frame and colorbond with aircell insulbreak is what I used and it works great. During a hot day the observatory is reasonably cooler inside. I have it under the roof and walls and spray painted it matt black as it is silver otherwise.

What about roll off roof and wheels etc? That can be tricky and really affect the outcome.

My advice here is:

1. Ask on the forum for various systems as there are many ways of doing it.
2. Make sure the roof clears the scope so if the scope swings it can't hit the roof. Also that a truss horizontal member clears the scope.
3. Keep your walls parallel and work out the track system so the roof rolls off and closes fairly easily. If you go to Bunnings your wheel choices are very limited. Richmond Castors and wheels have lots and I think they have an online store. They are in Wetherill Park Sydney.
4. You could use 100mm C purlin for the track, it comes in 6.1 metre lengths. I'd ask around as there have been some nice systems here and mine has been a source of trouble.

Greg.

Hi Greg
The stone walls are for retaining. They will not be going any higher than 1m. The site will be backfilled and levelled.
The next part of the plane was to build a platform over the top of the retaining walls and over the top of the pier footing. The platform will not touch the footing. It will protrude over the edge of the retaining walls by 1.5m this will offer shade to the stone so it will not heat up to much.
The platform will be made of Galvanised i beam as the main bearer, then timber joists with a timber floor. The timber I will use will be Cypress, very termite resistant. There will be a railing around the edge of the platform. Walking around in the dark with a sharp drop is not recommended.

As far as the walls and roof are concerned I have not given it a lot of thought yet. This has been a bit of a rush job so I can get a pier in and use the MX.
Your suggestion of light weight walls make sense. I will most likely use a treated pine timber frame and as you said some colour bond cladding with insulation in between.
The roof, I will be asking a lot of questions.

I wil post more photos as I go. I could not do any work today as it has been raining all day. ( must be all that new gear)

Cheers
Phil