Bukko

1 hour ago, souls33k3r said:

So true about the rabbit hole. 

But would M16 be better than using M12s or 14s in any practical way? 

I think it would all depend on how you bolt the whole lot together...I know many here do not like the rats nest used to mate the mount to a pier, if you do similar between the pier and foundation, I would think you would amplify the problems associated with it.

My second home-built pier was out of 12mm steel top and bottom with 8" nominal bore, heavy walled pipe. It did have an initial rigidity problem, until I grouted between the bolts and the foundation. This is how I always do them now and have no issue with movement through the pier and footings. othmy piers are the same construction, with the longer one for the ME2 also sporting some fins around 40cm long. I really don't think they will add much, but they were free with the pipe, base and top plate, so only the cost of a few welding sticks to fit.

The bolts really only hold things together until the cement hardens so in my case, I could probably get away with something a lot smaller. But the pier weighs in around 100kg, so it would be impractical to really test how small I could go....

Have you decided how you want to secure the pier down yet?

Gordon.

1 hour ago, souls33k3r said:

A little bit of advice needed. What bolt size and length do i need for the base plate? 

I used M16's...

You are already so far down the rabbit hole, an extra couple of quid will make no difference...

Gordon.

If you go with your Plan B...

Make sure the mixer is cleaned out afterwards, I would think that's why they want a £100 deposit...

Good luck.

Gordon.

You don't need a big mixer, something around a 85 to 100 litre volume..

Mix small batches, a wheelbarrow amount at a time. With two people, one can load and mix, the second emptying thee wheelbarrow into the hole whilie the first re-loads the mixer...

"I" laid three foundations when I started my build, it was enough to justify a ready-mix load, but it was agreed with my builder that it would be cheaper (and easier to manage) if we just mixed as required.

Good luck with the base, I am sure it will go well...

Gordon.

25 minutes ago, adyj1 said:

I would agree that operating a mixer isn't nearly as easy as it looks. Luckily the neighbour who helped me with my base was a builder, so I got to watch not do... 

Never found operating a mixer particularly difficult, only still hard work. Us "thinkers" rather than "doers" are not designed for hard work...

Gordon.

I really recommend not only hiring a mixer, but someone to operate it for you too !!

Outsourcing didn't really fade away after the 90's... Just went underground...

Gordon.

4 minutes ago, StarDodger said:

If you are digging the hole 75cm square and 75cm deep, then that is 0.75m3 of concrete, where do your figures come from...I think you are way out...

0.75x0.75x0.75 is 0.4218 m3

Still overkill and is about the dimensions I did for my ME2 and 16" ODK...

14 minutes ago, souls33k3r said:

I will agree with you on that mate but the reason why i mentioned the word Muslim is because he's one of the good eggs, like me we don't drink so Biryani will have to do

I have yet to meet a bad Muslim !!

Friendly, helpful and their whole world revolves around thier families.

I am sure you will get the help you need.

Gordon.

5 minutes ago, souls33k3r said:

My neighbour is a Muslim ... just like me so beer won't cut it but i do make a mean BBQ so can tempt him to that and some special homemade Biryani 

 

You would not be the first Muslim I know who was partial to the odd spot of alcohol... I worked in Saudi for over 2 years and had far too many discussions about different beers, wines and spirits for them not to have tried it.

Not judging anyone, it's not my place to do so.

But if you can win him over with a Biryani, then that's the way forward.

So, lots of advice comingin how to dig a hole, now you need volunteers!!

Gordon.

1 minute ago, souls33k3r said:

Hi Gordon,

My God man, i've been following your brilliant thread. The mount head isn't going to be massively heavy ... i'm thinking around 15Kgs of mount head at best and in total around 15kgs of gear on the top of the mount.

Wise words about minimal air trapped. I sure will seek some professional advice from my neighbour on that. He's a plumber by trade but quite handy and a great neighbour.

Mark (above) suggested a great place for the hire but i've also checked with a mate who lives quite close, he has a cement mixer so will use that. 

I too plan on using M16 studs and resin to make sure the contact remains solid.

My back is definitely not going to survive for the first few weeks but i guess i'm preparing myself that in the end, it will be all worth it

Thanks, I hope it has been entertaining... Ground to a halt ATM, having to completely re-do the terrace... Priorities from Mrs. Bukko...

The mixing puts a lot of air into the concrete and reduces its strength. Is it a problem? I am not sure but forcing the stuff into every nook and cranny in the hole will leave little room for the stuff to move later.

I would check if your neighbour works for packs of beer or something and get him to do the hard work... Best investment ever.

Gordon.

What are you planning to hang off the pier?

For mine, I had access to a digger and a huge concrete mixer and only dug the holes about 2 feet square. They were a little deeper than tall though.

Key thing is to make sure the concrete fills the hole completely; minimal air trapped and especially around the bottom and walls of the hole. We had one of those concrete vibrators to force the air bubbles out.

If you are digging the hole and mixing the concrete yourself, I am guessing you would like to make it as small as possible...

I can only say what I did, rather than what can be done, but when the concrete hardened, I drilled the holes and cemented in the studs (M16). When fitting the pier, I grouted between the pier and foundation, so making the best possible contact...

Good luck and hope your back survives!!

Gordon.

When we came to France house-hunting, I quickly started to focus on the power distribution - whatever anyone thinks as a poor installation is nothing comapred to what we have seen here...

James, if you are having a second phase commissioned, please be aware across the phases will be over 400 volts.

From memory of my higher education, where I did a years' module on three-phase power transmission, the supply is distributed on three wires, one per phase. At the step-down transformer, the three phase windings change configuraiton to make a 4-wire system. Three for the phases, the fourth a Neutral. Think about the shape of a Y with the centre being the neutral. This is then grounded at the transformer and this is the ground reference.

Ideally, the current in each phase is the same and if so, then no current would pass down the neutral wire (Kirchoff's law) Any difference in current will lead to current flow through the neutral and some offset in Neutral voltage to earth.

I would guess the four core cable you have would be the three phase supply and two of them have been isolated at some day.

Please make sure your electrician explains what you end up with before they leave.

My house has a three phase supply with it distributed around the house with at least 30mcb's as France does not do ring mains.

Take care.

Gordon.

Hi Gav,

glad to hear everything is sorted out now.

Still a big surprise things like this are not simply on the website but glad to hear the update is working fine.

And I think we are all waiting for clear skies !!

Gordon.

James,

How long is your cable run?

Mine is just over 60m of 4mm2 and the calculated numbers checked by my electrician for fault trip was fine. At my distribution point, there is an ELCB plus 16A breaker. I did not need to use an armoured cable. While I agree that steel is not as conductive as copper, it is still a reasonable conductor.. And as you said, there is a lot of it. Again, as I said, talk to your electrician. (again, assuming you used an armoured cable...)

If you have a really long run, then as Dave says, installing a ground spike would help deal with the grounding issue.

Good luck.

Gordon.

Hi Gav,

I thought this would be the easiest thing in the world to help with.. Go to the Pulsar website and follow a link titled "support" or similar... But there is none. I an surprised everything you needed was not supplied with the dome...

Did you get a reply to your email and the neccessary software to control it?

Gordon.

On 16/06/2019 at 21:53, JamesF said:

Yes, I think a bonded earth makes sense in this situation as it's a bit of a nightmare to export a suitably large earth from the house over such a distance (not to mention hideously expensive).  The electrician should be turning up at some point soon, so I'll discuss it with him.

James

Is there an earth leakage circuit breaker installed? If so, then this should take care of the earthing issue for you. If not, then if you have run armoured cable, the armouring could be used as the earth. Glanding off the armoured cable with a metal gland in your electrical box will do the earthing there too. Have a chat with your electrician and hopefully you have a low cost solution available.

Regrets on building an observatory? Plenty. But I am only part way through and over 6 months in on my over-ambitious build. But I know when done there will be absolutely no regrets remaining.

I spent an enormous amount of time thinking about exactly what to build, from ROR to hinged apex, to some sort of fold-down arrangement. But my place is on the top of a very exposed hill and the wind is pretty strong. I also have excellent southerly views to the horizon so wanted to take some advantage. This kind of ruled out any design with high walls and with the strong winds, went for a dome...

I also needed planning permission but in France and living in the middle of the countryside, it is more of a formality.

There is lots of good advice on SGL to help you decide what to build and where so you can get the most out of the build, so I recommend doing your homework and go for it! When done, no regrets.. Guaranteed.

Gordon.

Been a while since I posted an update...

The terrace job was not as simple as I thought; there was multiple thin layers of stuff over a mortar type of layer, sitting on top of the garage and pool room ceiling. When I was grinding the layers to try and increase the slope, the mortar layer started to break up.

Digging a litle further with an SDS chisel, the mortar layer started to lift in chunks. It seems to stick in some places, but lift pretty easily in others, so I think the whole lot needs to come up and I start again from the concrete roof layer....

I think the domes are really on the back-burner for a while now...

Any builders out there wanting a "free" holiday in sunny France???

Usual picture attached.

Gordon.

On 11/06/2019 at 21:25, Grierson said:

Many thanks James, but unfortunately I changed the focuser on my 80ED to a Feather Touch a while ago which has added to the problem of getting the correct bits! Having said that Alan indicates that UNC screws are American as well so I might be heading towards the answer and giving me a whole new area of knowledge around this simple question in the process. 😄

If you have a feathertouch, then email Starlight Instruments in the USA, they will certainly help you identify what you are after.

I have always found them to be extremely helpful.

Good luck.

Gordon

1 hour ago, DaveS said:

I would have liked a diagram showing planetary migration through time rather than just hand-waving, besides you cannot discuss the migration of Jupiter / Saturn without also discussing the ejection from the solar system of "Planet X", a Neptune sized object that took away a lot of the angular momentum, and the migration of Uranus / Neptune which IIRC changed places.

Having said which, I liked the program too, and am looking forward to the next episode.

I think you might have hit on the plot line for the next series...

Gordon.

23 hours ago, fwm891 said:

That depends on the tripod and in my case the need for flexibility. The Tri-pier is incredibly ridged and will sit on a concrete foundation isolated from the observatory building. My observatory will offer the quick usability a chance clear night might offer but I also want to go to location with a wider horizon and a pier in that situation is useless.

The context was placing a tripod on the lawn and hoping for stability.

The three legs, or contact points on the ground are a second problem for the unwary and I never managed a whole night without bumping a leg at least once. For visual, not a big deal, but imaging is made more difficult.

And I fully accept the limitation of a pier when transporting one around. It would be a great thing to have a self-boring pier that you can screw into the ground, then take it up again when done.

Hope this clarifies my point a little.

Gordon.

Hi James,

the IP65 boxes will be more than enough to keep the electronics dry. The problem will be the cable entries you need - a rubber grommet is not enough to maintain the IP rating. Little plastic cable glands like the link below will maintain the rating. To help, try and only drill through the bottom if you can and gravity will then help you.

Gordon.

https://www.ebay.co.uk/itm/IP68-BLACK-CABLE-GLAND-NYLON-WITH-NUT-PG7-PG9-PG11-PG13-5-PG16-PG19-PG21-PG29/282622655872?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D57923%26meid%3Db6547d16968f4f4f9e74a2debcbb6273%26pid%3D100005%26rk%3D4%26rkt%3D12%26sd%3D401751103669%26itm%3D282622655872&_trksid=p2047675.c100005.m1851

2 hours ago, Miguel1983 said:

Well i didn't isolate my pier from the rest of the slab, as you've seen i do have a raised floor around the pier, and the warm room is fitted with floor insulation, so i'm pretty sure no vibrations will be transferred to the pier, time will tell..

Worst case i can cut the concrete around te pier, i've got the gear for it 😉

With such a big pad and the raised floor, I also doubt you will notice any movement...

Gordon

If you consider the total cost of the build project, would the cost difference between the plain and roller type of bearing be noticable?

Gordon.

Absolutely - I would say almost any pier is an improvement over a tripod.

The ground movement does depend in part on the soil - my first pier was undersized with a similar amount of concrete under it that would be used for a fencepost. The soil was a problem and walking around the pier caused enough movement to affect the images (2500mm fl) The good bit was it was much easier to dig out than my last one - a couple of tons of concrete pad and pier footing.. I never want to remove my latest installation, it's even "worse"(better)

The building is not so important to be footed on tons of concrete and the blocks are much easier to manage.

Gordon.