Tall pier advice

[Rainsey]

Living on a tight residential block I do have a good spot to permanently mount my scope at the side of my south facing garage.


My thought is to build a platform approx 1800 on the side of the garage which will eventually be encased in a structure and a slide off roof.



issue is the pier. There is an exiting concrete slab that was to house a water tank that I can build on but the effective height of the peir would need to be around the 2 meter tall, possibly a tad higher.



Anyone out there done this and if so what did you use. I have seen a couple of American sites that use what they call chimney blocks which are around 400 square. The plan is to build the pier and then the structure around ti without touching.



Advice appeciated.


Cheers

Rainsey

[JA]

Originally Posted by Rainsey

Living on a tight residential block I do have a good spot to permanently mount my scope at the side of my south facing garage.

My thought is to build a platform approx 1800 on the side of the garage which will eventually be encased in a structure and a slide off roof.

issue is the pier. There is an exiting concrete slab that was to house a water tank that I can build on but the effective height of the peir would need to be around the 2 meter tall, possibly a tad higher.

Anyone out there done this and if so what did you use. I have seen a couple of American sites that use what they call chimney blocks which are around 400 square. The plan is to build the pier and then the structure around ti without touching.

Hi Rainsey,

One of our members here, Bojan (Hello Bojan) did something along the lines of what you are contemplating, using building blocks to create a tall column / pier. You can see some of the details in his observatory build thread and some pictures midway down the following page link.....

Bojan's Observatory Pier Column

Best
JA

[Rainsey]

Ja,


Hey thanks kindly mate. I'll have a look.


Kindest Regards
Graham

[bojan]

Yep (hello JA :-) )
I did this 3-4 years ago, it is still rock solid and my mount (EQ6) was aligned then and still tracks OK (maybe now it needs re-tuning... )

[Rainsey]

Originally Posted by bojan

Yep (hello JA :-) )
I did this 3-4 years ago, it is still rock solid and my mount (EQ6) was align then and still tracks OK (maybe now it needs re-tuning... )

Hey Bojan, thanks for the info. I am planning a tad higher than what you have by the looks of it. Where I am wanting to put it I still have to get visual over the Hip tile roof of the garage. Because of this a rough estimate is around the 2400 high mark.
Regardless what you have done sets the foundation. I could for example just have a higher initial brick pillar.
From your explanation I am guessing you used besser bricks. I would ideally need to fin something that would give me a square so I could alternate the brick alighnment for strength.
Hmmm all good food for thought. Thanks heaps.

[Rainsey]

Bojan,


I just realised, and I am a bit of a boffin for not realising it, by using a 390 x 190 x 190 concrete brick, and allowing for say 10mm of mortar, I do get a 390 square pillar.
Take back what I had previously said...

[bojan]

When deciding about column height, I considered couple of things:
- Closing the roof without damaging the equipment,
- Is it worth to go to the horizon, given the LP at low altitudes?.

I used two blocks per layer for the whole thing, but you can use 4 blocks (with middle cavity) for lower part, this will give you more stability and overall strength (provided it is really needed.. people tend to overdo those things, generally speaking) so you can go higher.

[Rainsey]

Originally Posted by bojan

When deciding about column height, I considered couple of things:
- Closing the roof without damaging the equipment,
- Is it worth to go to the horizon, given the LP at low altitudes?.

I used two blocks per layer for the whole thing, but you can use 4 blocks (with middle cavity) for lower part, this will give you more stability and overall strength (provided it is really needed.. people tend to overdo those things, generally speaking) so you can go higher.

Ha ha yeah Im probably one of those people. But your points are valid and they have been, especially getting low to the horizon.
I ideally want to get down to around the 20 to 25 degree mark and to do so I need to get up higher due to trees more than LP.

Again, thanks heaps for your feedback. Appreciated.

[gregbradley]

I've seen piers that are telescopic so you can raise them or lower them.

Probably a bit pricey but it's an option.

Gteg.

[Rainsey]

Originally Posted by gregbradley

I've seen piers that are telescopic so you can raise them or lower them.

Probably a bit pricey but it's an option.

Gteg.

Now that would be awesome but yes definitely our of my reach I think.


Love to see how they do it though

[FrancoRodriguez (Franco)]

Just a few things to consider: I'd be quite concerned about wobble/oscillation with such a tall pier, especially with a pre-existing slab. I wonder of you could drill into the slab to find out how thick it is? Perhaps you could look into a wide diameter base (500mm or thereabouts) welded to a thinner top 2/3. I'd use the longest Chemset bolts you can get away with on the slab (that's what I did but my pier goes 1.5m underground with a subterranean buttressed base--very solid indeed). Another option would be large buttress/vanes attached the the pier--this is what people usually do. I'd certainly go for very beefy wide vanes if I were you though or you might be very disappointed with oscillation. For added heft you might like to consider filling the pier with loose sand. Some people on the internet recommend adding some mineral oil to the mixture to prevent rust but I don't like the idea of that at all! Do you know any boiler makers? If not I'm sure you'd easily be able to get a small local engineering company to weld you up a solid rig. Best of luck!

[appiice (Ed)]

Hello Rainsey

Sorry to be jumping in so late but a couple of points / questions

Are you thinking of being in the garage away from the telescope or are you thinking of looking through the scope/

How exposed to wind will the mount / scope be?

Whilst generally our time is cheap ( at least when working on our own projects ) it is limited, the cost of concrete, blocks, steel really isn't all that great, so I would ( and did ) take the view that to spend a bit more on materials and be happy with the outcome is better than saving some money but getting a job that you are unhappy with.

Seems to me you are being hamstrung by the idea of an existing slab of unknown quality. I would remove the slab, either in whole or just enough for a new pier.

My set up is a block of concrete abut 1.5 by 1.2 by 1.2, with a 900mm square " riser " about 800mm tall off it, so all up about 7 tons of concrete, with a 1200mm tall 250mm diameter steel tube attached to the base with 8, 16mm threaded rods welded to the reinforcing steel.

Is it over kill? yes, but I get NO vibration at all, the telescope is protected by a dome that obviously helps.

I was a house builder for 40 odd years so I have some construction experience but the basic premise is anyone can dig a hole, anyone can dump concrete into that hole and anyone who is thinking of doing what you are most likely has the skills to place formwork. I have seen some pretty horrific amateur welds but they rarely fail and youtube can show you the basics, it is unlikely you will need to be able to weld vertically down ����

Good luck with your project