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Garden Pier..


NickK

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Cutting the strips for the pier former - be advised, if you're doing this with a circular saw.. it's going to take a while! 3/8 cut - there's a lot of measuring and clamping involved to get the blade (at 23 deg tilt) to cut to the right dimensions. If you have a saw table this is literally a case of set it up and then feed alternate sides... with a circular saw it means cutting in alternate directions and as the saw isn't identical measurements on the base to the plane.. lots of messing about!

Getting there!

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Update - created the 8 side panels (took ages!).

I quickly created two collar pieces - however these aren't correctly sized so they need a little bit more work.

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Annoying but this will be simpler to put right.

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These pieces are 1.2m high. I will fill any gaps and give it a coating of external varnish to seal the boards.

Cutting OSB is tiring - you need a respirator (like MDF it's glued), goggles (it throws sharp shards and dust)!

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Has anyone used a concrete sealant? From all the research it seems to be the thing todo - give a coating to prevent ingress of moisture.

Hi

I have always used Bondaglass G4 pond sealant for waterproofing sealing concrete it's lasted 15 years in my observatory base and you can recoat it if you need to .It beats anything else out their i have tried .

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Spent a hour or so fitting the first ring - now I know how a barrel maker feels like.. it's like a parallel jigsaw puzzle..

I still need to resize the bottom ring. There's a few gaps and one of the pieces I may recut.

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So the idea is to have the two/three rings providing two halves of the octagon and held together by bolt/clips.

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I've been advised to make a couple of wood 2x4 frames (put at 45 degrees) would help support the lower part of the former and prevent the pressure of the concrete from blowing out the shutters.

Given other experiences here (duct tape to the rescue in that instance) I think I'll do that!

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So I picked up 2x6m lengths of 10mm rebar, cut down to 2m lengths to fit in the car. I've also picked up the remaining sand and concrete.

I've fitted the former base and created a couple of metal wire loops to keep things in alignment whist a couple of gaps are being plugged with super strength glue. I've also put on a first coat of varnish inside and out to prevent water from penetrating. A couple more coats will be needed but it's good to get the first on early to allow it all to have a good hardening.

This is actually upside down:

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And the base that will fit at the bottom, you can see the rebar leaning too:

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I will create a couple of thick reinforcements, struts for keeping everything vertically aligned.

Still need to order the brake discs or find a pair in a scrappy, a piece of 1.5" tubing, a piece of conduit for the electrics, armoured cable for power..  start digging.

I have a section of the pond anti-kid lattice that the previous owner had that has been broken up.. it will be big enough to cover the hole whilst it's being dug and will act as a source of struct wood..

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So I started the dig - in 1 hour it was finished. I can heartily recommend the wickes post hole digger!

So hole dug, old bricks broken up and put at the bottom, wood batons for the top of the hole done and embedded, rebar is now bent and wired. I still need to sort out the support for the pier former but that will be tomorrow as it's started to rain 2 hours before forecast. I have a tarp over the top of the hole with a pipe in the centre to make a wigwam.. fingers crossed the hole will remain intact and dry.

Tomorrow sees the arrival of the cement mixer.. I hired it for two days so if the rain causes issues I have the option to delay the pour a day.

After the stress of the last week (almost certain possibility of being made redundant so CV and applications have started already), it's good to finally get this moving!

I've noted that it's 5degC tonight.. 3 degC tomorrow night... so I think I need to take steps to keep it all cozy..

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Well - I ache and it's done :D

I picked up the concrete mixer this morning.. 

Base filling nicely..

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I was compacting the pour using a piece of rebar and the hammer action (no rotation) to vibrate everything nicely. I also used the rebar that was sunk to agitate too.. bubbles appeared:

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Right up to the top..

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I reinforced the base heavily (including screwing in from the bottom to prevent blow out. The wire loops hold the concrete in place nicely.

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I've added the threaded bolts (1m each), created a template and used the brake disc to keep the threaded bolts in parallel with the holes. Unfortunately I had todo this once the sun had set and so no photo. 

For the record the solid corsa brake discs say 60mm but they're just a little too small for the EQ6 without a little widening.

I have 1 concrete, 2 sand and 4 pea shingle left. Probably caused by the base not being 100% square and the calculation being a circle rather than octagon that cuts chords (i.e. less volume).

Long day, pleased it's all tucked under a tarp as it's due to get to 3degC tonight and rain heavily tomorrow, friday etc.

I also learnt that the SDS drill hammer actions kills a SDS keyed chuck in about 30 seconds.. but .. I also learnt that the SDS can act as a pile driver for rebar..

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Nick you can rest well today that's some progress you've made.  Mixing and pouring concrete by hand is hellishly hard work, no wonder you ache. Never mind, once you get that shuttering off and view that pier you'll forget all about the aches and pains; it's going to be a beauty.  Good luck with the CVs.

Jim

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I've ground out the inner upper brake disc now too - the EQ6 fits perfectly. The adjustment alt-az works, and I needs an M12 bolt for the base..

So in the sunlight:

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Closeup of the disk and the inner former to hold the bolts parallel:

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The side has managed to keep quite well. If I had the chance again I may have spent an extra week on the former to glue the slats but this is acceptable :D

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All important southern view

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And the northern view

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Update - had a look today, everything looking good. The concrete (spill around the top) has hardened considerably (doing a 'snap test') each day which is a good indicator that it's curing well.

I still have the former on, this will be left for at least mid next week possibly the friday.. although the day/night temps have been decent (above 8degC at night) it's still going to be slower this time of year..

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Best to leave the former on for a good long time - don't be in any hurry to take it off.  I know this is easier said than done :D

Looking good so far :)

Given the monthly outlook... it could be on for a month! However I will need to come up with a solution for the covering tarp or the lawn will have patches of dead grass!

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Actually reading up on formers and winter laying - the US define formers as <12" and > 12" for pour temps and curing minimum temps - specifically preventing temps drop so that the temps cause expansion differences throughout the concrete (i.e. the centre of the pier, outer edge and block). The pour temps, headed formers, heated pipes in the ground.. 

The first 48 hours are critical. If it freezes it means a rip and re-lay. This is the time when the concrete starts developing it's strength, the percentage of water drops the most, and is generally the point when the concrete develops enough strength to (a) resist expansion caused by freezing (cure and  because of less water content) and (B) starts to get enough strength to stand by itself (although that is compression not any form of shear movement)..

Additional reading shows a general recommendation that the former is kept on for 7 days in summer as a minimum and 9-10 days minimum in winter for curing - then additional time over the next month to get to maximum strength. I have a bucket of the last concrete mix curing outside too - so that gives me a form of control to check that I prod with sharp things to see how it's getting on..

So it's like an advent calendar.. day 6 atm, day 10/11 at the weekend.. then probably next weekend (a weeks time i.e. 17-18 days) being the grand opening.

I have a bench drill press that I bought a while back, initially the chuck didn't give a great alignment but after resetting it, it's giving a neat hole in the brake disc with a 12mm metal bit - it's set to about 400 rpm. With a little sharpening stone oil acting to prevent overheating of the bit.  This weekend I will remove the brake disc currently set on the pier, give it a wire brush to remove the rust, drill it's holes and prime & paint.

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So update :) It's been 10 days since the pier concrete was laid, temps (apart from the first night reached 2 degC where I needed to add a heater) have been a minimum of about 8 degC.

I removed the brake disc (now rusty) to have a look underneath:

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The long bolts are actually 1 metre long, they have bolts in the concrete at the bottom and they will be cut down with the off cut being used to provide the levelling bolts for the discs. Waste-not; want-not.. They're M12 bolts.

I think getting the former that I used for the disc bolts will be a PITA to remove as it wasn't vanished.. in the end I'll probably put a couple of channels in so water drains if it does collect any.

You can see a drop of about an inch as the concrete dries:

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Examining the concrete spill that I left as a concrete test shows some interesting things. Firstly it's now rock hard - actually broke the aggregate:

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Also the spill on un vanished vs varnish shows it was a good idea. The smaller non-vanished portion (centre) came away from the top with a sound of wooden fibres being pulled (and you can see that in the sample below). The larger portion (left) with a smoother surface is form the varnished area:

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After wire brushing the top disk, then switching to emery paper (stuff you use on pipes that doesn't clog) to remove the rust - I've primed the break discs:

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I tried painting "non-drip" radiator primer on.. it resulted in the drips - so I ended up switching to spray aerosol primer that you can see gave a much smoother base. The older primed disc has it's holes drilled already.

This is my bucket control - which is sounding remarkably solid.. even with an inch of water on the top (hence the top is not as set)

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Sorry Gina - I couldn't wait any longer.... the concrete forms are off!!!!!!!!!!!! :D :D

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The base - this is showing the push out that I was expecting as my base of the former wasn't entirely weighted down.. but this helps strengthen the joint between the pier and the base block.

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Next up - the possible slight weaker layer due to a dryer mix. One thing that you see here is that the glue I used to bond a gap in the former reacted slightly with the concrete and left itself attached to the concrete (yellowing).. 

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The only "hole" in the edge is this one. Oddly the gaps in the shutters allowed the air to escape but this appeared on the glued side. The glue also left a small groove in the concrete - this will need some attention so that water does not freeze in it and flake the concrete off.

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So the top bolts were cut to size using a jigsaw and metal bit.

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So the initial fitting.. some adjustments needed.. some more bolts need - probably get some nylon bolts to prevent things from working loose.

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From the command centre HQ (the conservatory)

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The level in the EQ6 seems happy.. mine is pretty level compared to some.

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And finally the bottom bolting - how the EQ6 is attached to the top disk:

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There's some adjustments to lower the mount and to make things neater but for now... looking forward to a first light and polar alignment!

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Clouds stayed away long enough for a rough polar alignment and First Light (visually)..

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Now.. I can feel the gap between the EQ6 gear teeth..

I have one street light that covers my garden, one OMG-illuminate everything with a security light neighbour.. I may get the mrs to make a light baffle for the focuser.. that way no light will get through any cracks..

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The mount is steady enough to hold a IXUS80 against it and take a few frames (takes JPEGs only and is battered heavily :D).. aligned and stacked in PI.. it's up there... Vega! (and M57 next door :D)

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There's an odd feeling compared to using the tripod.. the stars seem steadier and the scope seems to easily whizz around :D but my 1.25" elbow can't get focus - which would have made it easier to view.

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Well done Nick, excellent work, the hexagonal design of the pier is really cool it adds another layer of interest, well worth the extra effort required.  How does it feel now to have a permanent capability?  Are you going to consider a scope cover or are you looking to remove/ set-up the scope on each session? I'm wondering if I will just leave mine mounted say on weekend sessions, I can't see me doing much during the working week.  Lol, what with the weather, I'm really narrowing down my observing opportunities!

Jim

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