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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Pier question ...
#4887428 - 10/29/11 06:22 PM
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Ok, so here is the situation :
My family, i.e. wife and daughter, and another munchkin on the way, live in Sweden, just 20 km outside of Stockholm (leafy suburb …) where we just bought a new house with two nice storage sheds on the property. One of these sheds is at least 14 x 14 feet, has a great concrete floor, electrical outlets, is insulated, and has a flat roof, i.e. the works. Within a couple of months I will be moving there permanently … Of course we are in a highly light polluted area close to a big city, and there are two street lights not too far from the storage sheds, which one probaly will not be able to “deactivate” with a suitable “projectile” due to pesky “legal” reasons …
My gorgeous wife, being wonderful, has agreed that after a few small renovation projects I am allowed to build a little observatory  so I would like to use the storage shed that has the concrete floor, etc., to make an observatory (the other shed is used for storing wood and garden tools and bbqs etc …) … I will only do visual for a long while using the equipment in my signature, and whatever is to come later …
So, to build an observatory from this existing shed, I would cut a large hole in the roof, and likely mount a rotatable dome on top (or roll off roof)… question is the pier … my idea is to build a pier from concrete blocks to be attached with mortar to the concrete floor, and filled with rebar and concrete to make a pier, and get a good pier plate machined (access to machine shop no problem), to mount the existing CG5-GT, or whatever comes next … then I would suspend a wooden floor, made of 2 x 12s and plywood, around the pier (without touching it), suspending the floor from at least 4 to 8 wooden posts made of 4x4s (4 in the corners and 4 elsewhere – it’s a square building) … the pier would be high enough to reach into the dome with the scopes to reach sufficiently near the horizon …
Since I only plan to do visual observing and, due to the LP, and at best only solar system imaging one day in the distant future, do you think this plan would be ok in terms of minimizing vibrations? Would walking on the wooden floor transmit too much vibration to the concrete floor, hence the pier? I think one could also add thick rubber insulation between the 4 – 8 wooden posts and the concrete floor …
Does this sound reasonable? This will be a long term project, so no immediate “ground breaking” anytime soon … we’re still in the planing stage …
All suggestions welcome.
Cheers and beers,
Michael
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Tom and Beth
Carpal Tunnel
Reged: 01/08/07
Loc: Tucson, AZ
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Re: Pier question ...
[Re: Guy Noir]
#4887543 - 10/29/11 07:27 PM
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IMO, as light polution will limit you, I'd take advantage of the dome or ROR to hide the street lights and concentrate on the THOUSANDS of double stars, as well as the Planets and Asteroids. You might consider Solar Observation as well.
As for your pier, you don't mention how thick your current concrete pad is. You MIGHT be able to have a local Steel fabricator weld you a 3 meter tall pipe of 200 to 250MM, with a large flat on the bottom that you could bolt to the floor with anchor bolts. You would need to rent what we call a "Hammer Drill" on this side of the pond to make the holes suitable for the anchor bolts. All this assumes that you have a very high tensile strength Concrete floor. If the Concrete floor doesn't have this strength, it's possible it would slowly buckle under the weight of the concrete pier you already discussed. This is an area that it is actually cheaper in the long run to have a professional concrete firm inspect what you have. Same goes for a structural Engineer to inspect the current roof and advise what you can cut away to get the opening without weakening the current roof.
Anyway, it's what I would do first if in your shoes.
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: Tom and Beth]
#4887606 - 10/29/11 08:12 PM
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Re.: "IMO, as light polution will limit you, I'd take advantage of the dome or ROR to hide the street lights and concentrate on the THOUSANDS of double stars, as well as the Planets and Asteroids. You might consider Solar Observation as well."
Yes, I agree ... also, giving our long summer with almost no night, a Hydrogen alpha etalon for the 120 ST is already being considered ... in addition to lunar, planetary observations ...
Regarding the floor, this being Sweden (meaning everything is done really well, AND everything works, well, almost  ), according to the house plans, the concret floor in the shed is 30 cm thick (about 11.8 inches) ... so would this be thick enough to bolt a steel pier to it? I am familiar with the tools you mention, being an American and all  plus being a hard core physics nerd, with machining experience, I even own a modest size "hammer drill" or Schlagbohrmaschine as its called in Germany, the land of my mother ... soooo, do you think this floor will do the trick thickness-wise, in which case I can drill the holes for the anchor bolts, and get the machine shop to weld and machine me the steel pier, or should I reconsider the plan???
Happy Halloween ...
Michael
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: Guy Noir]
#4887612 - 10/29/11 08:16 PM
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Oh, and yes, you are right about the roof, I will get the architect to check how much I can cut out ... the roof is 14 x 14 feet like the shed, but some reinforcements around the cut out part will likely be needed ... good thinkin'
Mike
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: Guy Noir]
#4887617 - 10/29/11 08:19 PM
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... oh, and I do not know the tensile strength of the concrete, there is no description in the house plans, so I guess its the same as the house foundation (we have no basement, so its thick) ...
Mike
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Bob Griffiths
Getting Grouchy
Reged: 10/10/05
Loc: Frederick Maryland
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Re: Pier question ...
[Re: Guy Noir]
#4888245 - 10/30/11 08:56 AM
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Wow...an 11" thick concrete floor...
I have a two post car lift in my garage that I use to work on my cars (another hobby) .. it is rated to lift a car or truck that weights up to 10,000 pounds that I simply bolted to a 6 inch thick reinforced concrete slab... I have no reservations at all of standing under a vehicle to work on it...
Unfortunately I do not remember what strength the concrete was as the floor was poured 25 years I would "guess" a regular 6 bag mix...
Bob G.
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: Bob Griffiths]
#4888331 - 10/30/11 10:32 AM
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Bob - so does your "wow" mean I can go ahead and plan to use achor bolts for a steel pier bolted to the floor --- it would save me some work ...
Btw, hope you did not get too much snow down there ... I used to live for 7 years in "Balemer" (hows about them Os?), I remember the snow storm during the winter of 78/79 I think ...
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astroRoy
professor emeritus
Reged: 07/09/11
Loc: Southern Oregon
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Re: Pier question ...
[Re: Guy Noir]
#4888343 - 10/30/11 10:47 AM
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Just to try it and see if I got acceptable results, I bolted my pier to my 4" thick garage floor slab. My pier is a 14" steel tube welded to a 24" by 24" 3/8" steel plate. I used 8 - 1/2" concrete anchors to hold the plate to the floor and bedded the base plate for 100% contact with the floor. I do 20 minute subs from the top of the 7' tall pier. It also has a 16" pier extension on top of the 7' pier. Couldn't ask for a better pier for AP. I attribute most of the stability to the diameter of the main tube (14") and bedding the plate to the floor (slab) with bedding grout. If I jump on the slab near the pier, I can produce a slight jiggle. Walking nearby does not effect it noticably.
Roy
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: astroRoy]
#4888356 - 10/30/11 10:57 AM
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Roy - thanks for the info. I think I will go the same route then ... also sounds to me, by what you mentioned, that I might not need a floating floor for vibration isolation if the pier is in proper full contact with the floor and grouted to it ... this will make things a lot easier.
Michael
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Lenbo
member
Reged: 04/08/09
Loc: Cochranville, Pa.
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Re: Pier question ...
[Re: Bob Griffiths]
#4888367 - 10/30/11 11:04 AM
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Michael. I built a 10x12 rolloff on an old 6" concrete slab that I setup many years ago for a storage shed. The shed was torn down a few years back due to neglect and the fact it was replaced by a larger barn. Decided to build a rolloff last year using the old slab. No pier because I was primarily visual. After tripping over the tripod enough times knocking out my polar alignment I decided I needed a pier for my Atlas mount. I decided to use concrete blocks mortared up and filled with concrete. I drilled some holes in the slab and epoxied some rebar in place. I then cut some standard 8x16 concrete blocks into 8x8 squares and mortared them in place. After the mortar set I then filled the blocks with concrete. I made up 1 1/4 inch plywood top plate and adapter with all the bolts and hardware. I used 1/2x12" bolts set in the concrete to secure the top plate. The mount adapter is an 8" circle. I turned it on my woodlathe to the dimensions needed for the mount. My intention was to get it all working together and then take the plywood components to a machine shop and have them duplicated in metal. I found that the setup has worked so well for me I haven't bothered to replace them. I now have a Mallincam and its still working pretty good. I'm not up jumping around when using the Mallincam so the floor isn't an issue for me. I found if I give the pier a hard whack with my hand I get some brief vibration. I suppose I may need to tweak the polar alignment occasionally if I get frost heave. I'm not really doing anything more than a few minutes with the Mallincam and it seems to be doing a pretty good job so far. It frees up room in the ob, I don't bump into it and it was cheap. Good luck with whatever you decide.
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Lorence
professor emeritus
Reged: 09/15/08
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Re: Pier question ...
[Re: Guy Noir]
#4888566 - 10/30/11 01:07 PM
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Your idea will probably work well enough. If not you can still dig things up and install another pier later. Just keep that in mind when you are putting in the wood floor. Use screws to assemble it and it will be easy to take enough of it apart to dig if you have to.
Rather than using 2 x 12's joists, look at these. They can easily span 14 feet without support in the middle.
http://www.kentinternational.ca/brochures/Timberframe_System/TJI.pdf
If you are in a badly light polluted area and still want to see deep sky then look at this camera.
http://mallincam.tripod.com/index.html
You can see live broadcasts by people using those types of cameras here.
http://www.nightskiesnetwork.com.
I haven't used an eyepiece since getting my first camera.
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Tom and Beth
Carpal Tunnel
Reged: 01/08/07
Loc: Tucson, AZ
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Re: Pier question ...
[Re: Guy Noir]
#4888619 - 10/30/11 01:56 PM
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Quote:
Re.: "IMO, as light polution will limit you, I'd take advantage of the dome or ROR to hide the street lights and concentrate on the THOUSANDS of double stars, as well as the Planets and Asteroids. You might consider Solar Observation as well."
Yes, I agree ... also, giving our long summer with almost no night, a Hydrogen alpha etalon for the 120 ST is already being considered ... in addition to lunar, planetary observations ...
Regarding the floor, this being Sweden (meaning everything is done really well, AND everything works, well, almost ), according to the house plans, the concrete floor in the shed is 30 cm thick (about 11.8 inches) ... so would this be thick enough to bolt a steel pier to it? I am familiar with the tools you mention, being an American and all plus being a hard core physics nerd, with machining experience, I even own a modest size "hammer drill" or Schlagbohrmaschine as its called in Germany, the land of my mother ... soooo, do you think this floor will do the trick thickness-wise, in which case I can drill the holes for the anchor bolts, and get the machine shop to weld and machine me the steel pier, or should I reconsider the plan???
Happy Halloween ...
Michael
Wow, as somebody above said "30CM / 11 inches thick?". IF you have any doubt as to the tensile strength your "Schlagbohrmaschine" will likely remove any doubt as you punch the anchor holes  I guess you could do a core sample of the tensile strength but heck, you'll know the answer very quickly.
Let's see; 14 feet square by 11 inches thick slab of concrete. Yeah, my guess is that you'll be fine (Assuming you find that concrete was a good solid mix).
BTW, my Maternal Grandfather immigrated from Germany, and my Cousin finished in the top 5 of the last several Tour de France.
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astroRoy
professor emeritus
Reged: 07/09/11
Loc: Southern Oregon
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Re: Pier question ...
[Re: Tom and Beth]
#4888639 - 10/30/11 02:11 PM
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Michael, a couple extra notes on my pier. Since my scope mount is almost nine feet above the floor, I have a raised wood floor (4' above the slab) so I have easy access to the equipment. That solves another problem as well. My warm room sits adjacent to the pier and platform, so it is easy to route cables through the wall, under the raised floor and up the pier to the telescope. Even a wood floor on top of the slab would be good for that purpose - no more tripping on cables. With your very thick slab, I would bet good money that a passing bulldozer wouldn't jiggle your scope. But if you do construct a floor, do as you originally planned and isolate it from the pier.
Roy
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: astroRoy]
#4888861 - 10/30/11 04:13 PM
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As I don't know the true quality of the concrete, I will do some test drilling when I'm there again in a few weeks (have to work in Canada, so I oscillate every 5 -6 weeks or so ...), but given what I have learned about how well Swedes* seem to make stuff at home, I am hopeful that it will pass muster.
(*of course I mean the people, not the root veggie )
For the wooden floor, I like the idea of joists, and I am sure they have stuff like that at the local "Bauhaus". The ceiling of the (very solid btw) shed is about 2.2 m (7.2 feet), so for the scope to reach into a dome (bought or home made, not decided yet) the pier needs to be high enough, and I would need to have a raised floor to get at the EP, and all cables shall be hidden under the floor. Since the house is close enough (i.e. it can be my warm room), I can connect the pc in the observatory to our wireless network (which is hooked to the net via fiber to the home) ...
Actually, I was thinking that just in case the tensile strength of the concrete slab is not good enough, I can construct the steel pier with three large steel feet (like the small piers one can buy), that sit on the concrete floor and are blocked in place so they won't move, but are underneath the wooden floor, so no tripping on them in the dark ... that way the pier is also removable in case one sells the house ...
Oh, I forgot to mention that there is an extra stand up fridge and a stand up freezer in the shed, which will have to stay (so sayeth SWMBO)... we don't use them unless we have a party, so they will be off, and not create thermal problems ... however I wouldn't mind the fridge being on, what with some liquid refreshments being handy sometimes anybody know if a running fridge would create noticable air currents ?
The shed seems well insulated also, since in the summer I noticed how cool it was inside, even with a dark roof ... maybe its that slab of concrete so I won't have to do anything fancy to the roof for cooling ... well heck, Sweden does not get high temps anyway (at least not now ...)
Anyway, thanks for all the great ideas, keep 'em coming.
Michael
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astroRoy
professor emeritus
Reged: 07/09/11
Loc: Southern Oregon
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Re: Pier question ...
[Re: Guy Noir]
#4889275 - 10/30/11 08:33 PM
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Michael, in my mind, I wouldn't worry about the concrete. You'll know the quality soon enough when you hammer drill the holes. I'd worry more about hitting rebar. Do yourself a favor and buy two-part epoxy purposed for anchor bolts in concrete and glue the bolts in the holes. It helpts to get them tight without pulling them halfway out of the concrete.
Roy
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roscoe
curmudgeon
Reged: 02/04/09
Loc: NW Mass, inches from VT
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Re: Pier question ...
[Re: astroRoy]
#4889978 - 10/31/11 09:43 AM
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Michael,
I'd also vote for bolting a pier right to the floor (or building one from blocks) and not even putting a wood floor in in unless you want it for foot comfort, or need it to gain height. Unless the concrete's obviously crumbling, I bet it's fine, and plenty stable enough for any but the most demanding photography work.
You could perhaps put a switch with a pilot light on your refrigerator circuit, so you could shut it off, and have the pilot remind you it's off....
I'd vote for a dome over a roll-off, just because of the additional light-shielding it offers.
Russ
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Guy Noir
sage
Reged: 04/27/05
Loc: Stockholm Suburb - Sweden
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Re: Pier question ...
[Re: roscoe]
#4890182 - 10/31/11 12:05 PM
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I also tend towards a dome (home made most likely) because there are 2 street lights that are not far enough away as I would like ... The concrete is in excellent shape, but I will need something for the height since the head of the mount will have to be at around 6 1/2 - 7 feet. Maybe a floor, or just a platform around the pier ... as soon as I'm home again, I will make up some plans ... about hitting rebar, very good point ... I will check if there is any info on that in the house plans we got ... these crafty Swedes might just have written down at what spacing the rebar is ... ya never know ...
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gavinm
Carpal Tunnel
Reged: 08/26/05
Loc: Auckland New Zealand
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Re: Pier question ...
[Re: Guy Noir]
#4896097 - 11/03/11 06:00 PM
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Remember the height of the dome slit can be pretty tall, needing a ladder to open and close. Also strength isn't as important as vibration - the pier won't be under any major lateral forces (you're not going to be pushing the pier or doing slews at 30 degrees/sec). Steel piers can be really cheap - Someone made one for me for free....Just bolt it down and isolate the building. The floor should be at a height that allows comfortable access to the scope and dome.
My floor was initially too low, so either I got a shorter pier or lifted the floor - Eventually I lifted the whole observatory 2 feet - easy
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Samir Kharusi
Carpal Tunnel
Reged: 06/14/05
Loc: Oman
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Re: Pier question ...
[Re: Guy Noir]
#4898247 - 11/05/11 12:05 AM
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A "reasonable height" pier on concrete will be fine, even for imaging. I have been using one for a few years, and the concrete is a roof slab 8m above ground. Visual observing is very forgiving. Your own breathing will be a greater nuisance for hi-magnification observing than walking around. For imaging, you set up for a few hours and then go watch TV while the thing takes DSO subexposures. So what if the first subexposure shows shake. Just discard it. Unless a dome is really, really necessary, I would keep away from it. Every time you slew, the dome has to slew too. That's a major annoyance for my style of visual observing, no more than a few minutes max on any object. Imaging requires far fewer slews, of course.
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Peter9
Post Laureate
Reged: 10/30/08
Loc: Yorkshire - Born & Bred
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Re: Pier question ...
[Re: Samir Kharusi]
#4898452 - 11/05/11 08:19 AM
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Unless a dome is really, really necessary, I would keep away from it. Every time you slew, the dome has to slew too. That's a major annoyance for my style of visual observing, no more than a few minutes max on any object. Imaging requires far fewer slews, of course.
Not with a SkyShed P.O.D. you don't.
Regards. Peter.
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