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My pier build ..


AlistairW

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Hello,

My pier build .... not done yet but happy for comments if going in the wrong direction.

> Hole in the ground ....

> Paving slab will be set in concrete in the ground.

> Paving slab has a hole in the middle with a 12mm x 1000mm steel threaded rod running through it.

> Rod runs through a large flower pot (frost proof).

> Paving stone and pot are bolted down on the steel rod.

> Plastic tube fits over the rod in the flower pot.

> Plastic tube has a number of large holes in it to allow concrete to flow between base and pier. Also has a number of steel rods going across the diameter to help the concrete 'stick'

> Head mount assembly (build form scratch myself) then sits on top, with J bolts set in the concrete pier.

Any comments appreciated before I start pouring concrete .... it will be a two stage pour, first to set the paving slab, and the second to fill the flower pot and pier.

Only mounting a small refactor for astrophotography, so I think it should be stable enough.

Alistair

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Is the joint between the flower pot and the paving slab a potential weak point?  I'd add a few extra bolts there to prevent movement, but then I do tend to over-engineer things.

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the mounting plates were from ebay at http://www.ebay.co.uk/itm/Skywatcher-EQ6-EQ5-EQ3-2-Mount-Pier-Adapter-/291420656960?pt=LH_DefaultDomain_146&hash=item43da065540

the plates again off ebay http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2055845.m570.l1313.TR0.TRC0.H0.XMild+Steel+Discs+Circles+50%2C60%2C75%2C100%2C125%2C150%2C200mm+x+3+%26+5mm+Thick+-+Laser+Cut.TRS0&_nkw=Mild+Steel+Discs+Circles+50%2C60%2C75%2C100%2C125%2C150%2C200mm+x+3+%26+5mm+Thick+-+Laser+Cut+&_sacat=0 plates were 200mm x 5mm

Bolts and nuts were from B&Q - main supports were M12 x 180mm

Zinc Plated J Hook Bolt M8 x 200mm which are to be set in the concrete are from http://www.raygrahams.com/?gclid=Cj0KEQjwxpipBRCap8PR2Om7vq4BEiQA6V7OVXBET55l_nDGScWStugekyY3SxifwQYv9SjeKWwoLfoaAgrD8P8HAQ

Hope those links work

Did think about putting it all in the ground, but digging the hole was killing me ....

Thanks for sharing that shopping list!

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Hi Alistair,

One weak point is that all steel will eventually rust. Cement can corrode steel and it is not entirely waterproof. There is a solution, when putting in footings with steel reinforcement  I use a product available from some builders merchants called Sika 1. When water comes into contact it forms a barrier. Just look on the web for the info. It is not cheep but then again do you want to have to dig it out in say 8 or 10 years time if it rots through. It depends upon how wet the ground will be. usually if indoors, i.e. in the observatory and dry ground  there will be no problem. But outside in the open is a different matter. I would in that case also raise the cement at a slight angle up to the pier, so rain cannot puddle around the base. Lastly I would  paint the metal with an epoxy paint. This will ensure that it lasts for a very long time. The one I use  states that it will provide protection for 10 years. It is called Rust Bullit. comes from USA originally but can be bought here.  www.rustbullet.com/. Appart from that looks good, hope you get it all sorted.

Best of luck with the project.

Derek

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Thanks Derek for the advice on the rusting of steel, that is something I will definitely be investigating. I was kind of aware of it, but looks like there are some solutions I can look at.

Tested the mounting plate assembly fixes to the mount today ... thankfully it does. Simple star shapped bolt connecting from underneath.

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One other thing I forgot to mention. When you mix the concrete use a fairly large ballast. I.e. Inch or bigger. This increases the strength. Also you use less water in the mix. Less water takes less time to dry out and ensures that there is less moisture in the cured mix once set. It takes months if not years for the water to fully dry out. Concrete also hardens basically forever. So don't make the mix too strong 123 is a good mix I.e. 1 part cement, 2 sand, 3 gravel/ ballast. It will need several weeks to become hard enough, although it will set in a day. If it is going to be frosty don't do it. You can mix in frost proofer but it will react badly with the Sika1. If you really have to get it done in the cold where frost is likely cover the job with a few old towels and a plastic bag.

Lastly use washed sharp sand not yellow sand. Unwashed sand contains salts. These salts will set up a track through the concrete for moisture to penetrate.

Hope your back is OK, I know I've done it many times. Hiring a mixer is a good idea if there is a lot to do.

Have fun.

Derek

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  • 1 month later...

Not posted here for a while .... (dad with twins so sometimes projects take a break) ..... anyway got to the concreting today .....

Concrete in the hole to a good depth. Then the slab with extra bars set in the concrete. Once that was set the pot was screwed on to the slab and tightened down, with the final pour in to the tube and pot. Just waiting for it to all set now .....

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This looks interesting, Ho stable have you found it? Im thinking of putting a pier in the garden but its quite small but this seems to offer a good solution to the problem if its stable enough to hold an Heq5 with A SW 127 MAK and a camera.

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The concrete is now well set and the thing is as solid as a rock. simmo39, I still have metals bars going through the pot in to the slab and the cement in the ground, so it is still a permanent installment, not sure if that was clear. But I am mounting a HEQ5 pro and a small WO GT81 on the pier and it is very solid. I have even added some decorative stones to the pot :-) - will post some pics when I get a chance.

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My next worry is that I want to leave the HEQ5 pro mount head on the pier permanently, so that i don't have to keep polar aligning etc, whilst keeping all the OTA & electrics indoors. I see that one solution is to simply use a BBQ cover over the mount, but I still worry about rust and moisture on the mount electronics. Am I being overly cautious, and a simple cover should be enough for UK weather conditions ?

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If it has moisture on it the cover will have to be breathable. Poly covers are obviously not  but a couple of sheets of air vent filtration mats will keep the cover far enough off the scope to allow air to circulate. You can get small poly or plastic out buildings  made for tools. Then bolt down and fold back when you need to use the scope. Someone else (SGL) here has done it and looks good.  I would be more worried about theft if not in a proper housing. It all depends upon your area and if you are covered by insurance.

Derek

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The concrete is now well set and the thing is as solid as a rock. simmo39, I still have metals bars going through the pot in to the slab and the cement in the ground, so it is still a permanent installment, not sure if that was clear. But I am mounting a HEQ5 pro and a small WO GT81 on the pier and it is very solid. I have even added some decorative stones to the pot :-) - will post some pics when I get a chance.

Yep, saw that later when I was looking, Im still thinking of going down the same route as you, I have just ordered the adapter plate on E bay. Did it fit the HEQ5 well?

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Simmo39 - i would be carefull if you bought the same plate as me - the hole for the alt-az was not right for my heq5 pro. I ended up having to redrill it. The plate does not seem to be like the altair astros which have many options for the post. I was fortunate as i have a pillar drill in my garage and was able to create a new hole. Not sure if the heq5 and the pro version are different though.

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Simmo39 - i would be carefull if you bought the same plate as me - the hole for the alt-az was not right for my heq5 pro. I ended up having to redrill it. The plate does not seem to be like the altair astros which have many options for the post. I was fortunate as i have a pillar drill in my garage and was able to create a new hole. Not sure if the heq5 and the pro version are different though.

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Simmo39 - i would be carefull if you bought the same plate as me - the hole for the alt-az was not right for my heq5 pro. I ended up having to redrill it. The plate does not seem to be like the altair astros which have many options for the post. I was fortunate as i have a pillar drill in my garage and was able to create a new hole. Not sure if the heq5 and the pro version are different though.

Thanks for the reply, I have ordered one anyway as for the money I couldnt find one cheaper, Will find somebody with a a piillar drill if i need to. Just looking for a pipe know.

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