Shed obs

[baileys2611]

I'm starting out on what will no doubt be a long and expensive journey, but I'm hoping the end cost will be less that a dome purchase - which can start out at around $5k for something decent.

So, budget requirements led me to plan a skillion roof shed and have the roof "flip" on a simple hinged arrangement. I've obtained a bollard which will form the base of my pier and have to find someone that can machine and weld a steel plate on to that, then an aluminium plate separated by threaded rod for levelling.

I'm a little worried about flexure in the metal, but will just have to leave those worries alone for the time being and get the shed up in the first place, then bolt the pier in place on the slab - which is actually the top of my in-ground water tank.

Some pictures of how it looks now. In a few weeks I'll start to mark out the shed spot and get the family over for a good shed building and bonding experience :rofl:

[niko]

Good luck with the project and while I don't want to rain on the parade it seems to me the inground water tank "roof" might not be the ideal foundation for your pier.

I'm not expert and maybe others can comment but most choose a substantial concrete foorting on which to mount the pier. I think the top of the tank, which I presume is less than 200mm thick will be prone to flexure.

Is there a reason why you wouldn't just dig a hole and fill that with reinforced concrete?

In relation to the bollard - apart from being a bit low is it concrete filled? If not I would suggest filling it with concrete - that will reduce flexure.

As I say - don't want to dampen the spirits but would hate to see you go to great effort for an avergae result.

Hasten to add again - I'm no expert!

cheers

niko

[pmrid]

SImon, since you'll be bolting the pier to a slab you can use nuts above and below the pier base as a levelling mechanism instead of having a separate adjustment plate made for the top. Just be sure the bolts in the concrete are long enough. I use 1/2" threaded rod and it works fine. I have this arrangement on one of my piers - with appropriate mounting holes drilled/tapped into the top plate on the pier and a small window cut into the side of the pier just below the top plate so I can get a spanner inside to tighten down the centre bolt that your mount will certainly have. I can draw it up if that would help.
Peter

[baileys2611]

Thanks Niko

I'm hampered unfortunately by geography and err...I think I'll call it aesthetics for now (what can I say, other than my overriding instruction has been "If you get in the way of my nice view I will make you invent a cloaking device" :eyepop:). My property has a gully running right through the middle of it, which is basically a moisture trap so I can't go further down the property or I'll end up being a participant in that Monty-Python sketch where they build the castle in the swamp, can't build off to the side or in front (driveway in front, large shed to one side, house to the other). The options are not good :shrug:

You are right of course, the top of the tank is going to give some vibration. My only hope is to mount the pier in a way that dampens it all, which I have some flexible tile glue and a piece of marine rubber matt. I'll make a sandwich of that in between the tile adhesive and hope that does the trick (along with bolting it in to the slab which is only 200mm thick - you are correct there). The pier is concrete filled, which will reduce vibrations to some extent.

Peter I appreciate the offer of diagrams, I admit I am struggling with the best way to set this up - but cannot actually get in to the middle of the pier to fix a centre bolt.

I thought that something like this might work?

[niko]

Cheers Simon,

appreciate your constraints, particularly the non-physical ones!

Will you have a raised floor? I think if you are able a floor that is not tied to the tank top would really help unless you are planning totally remote imaging? Maybe bearers that run from stumps either side of the tank and floor on that?

niko

[baileys2611]

Yes! That's a good idea. I'll look at what I can gather that will do just that. This way I could put the remaining Insulshed in between the bearers and the floor, giving a good barrier for whatever moisture forms under the floor to condense on and 'drip' off again before it gets inside the shed. :thanx:

[ZeroID]

My tinshed OBs, SkySlab has a floating floor. The 4 x 4 meter slab of concrete it sits on tends to puddle when it rains. The floor sits about 300 mm above on bearers and blocks with a plastic damp proof membrane beneath. Isolates from the pier which is secured to the slab and keeps it all dry above. No problems so far at all.

[baileys2611]

Thanks Brent,

I am curious - how do you get the waterproof membrane to stay waterproof around the pier? Is the membrane underneath the pier or do you cut around it?

[ZeroID]

I just cut it so it was a tight slide fit then a bit of Duct tape. Fortunately water doesn't climb upwards very well, it obeys the law of gravity and stays down below. My Ob has lots of airgap holes at the wall base and roof line, corners etc so stays quite dry.

[Tandum]

I normally get mine aligned and guiding from the dome, then kick off the image capture remotely from inside the house. No vibration problems when your not there :)

[baileys2611]

Coming together in bits and pieces. Two pictures, the shed being constructed - still have to put it together which is not actually as easy as the instructions all say. Ever tried to use self-tapping screws to drill into a flexible very thin sheet of zincalume? Sufficed to say that pilot holes make it all easier. The second picture is my home made pier in the middle of a coat of gloss black. This beauty has cost me about $100 so far.

I've had the tank 'tested' for vibration - sort of jumped up and down on it and used an accelerometer a friend had - no it wasn't my iPhone. Yes, it's a drum. It picks up vibration quite nicely and distributes it across the whole surface with surprising clarity! So, mounting the pier will require some flexible tile glue, a piece of thermally treated (exterior) rubber and some dynabolts. The glue and rubber will absorb vibration to some extent, the dynabolts hold it all in place and the pier is actually 165mm diameter, 6mm steel filled with concrete so the vibrations will be dampened significantly.

I've managed to land a 20mm piece of 256mm aluminium from a supplier in Sydney for about $35 (shipping was a bit more - but still cheaper than getting it from anywhere in Canberra!). I purchased a mini pier from ioptron for about $100 for the ieq45, again shipping was a bit more from America but it beats $500 for a plate designed from Dan's plates in America. I'm going to tap some threaded holes into the aluminium plate, mount to top part of the mini-pier (it comes off! Gives me a nice template and mounting block) directly to the aluminium plate and that way I can take it off and tap some new holes when I upgrade (or just get a new aluminium plate, not expensive).

So far, have got away with it for under $900. The wood for a floating floor will be a little expensive as I'm not going to get that second hand. I expect all up it might be about $1500 when finished.

You'll see in the picture I have some SW pipe and some black...err...other...pipe. I'm going to attach the SW pipe to the top of my inspection valve from the outflow of the water tank - water does not come up the inspection valve as it's higher than the overflow outlet. I've purchased 1kg of activated charcoal which I will hold inside the pipe with some stockings stretched over the air outlet. This will provide water cooled air into the shed. The air outlet will be a twin chimney system (yet to be fully designed by me) consisting of the black pipe, rising up from the top of one of the sides and capped (with a u-bend at the top and a mozzie-proof open air outlet). What I plan on doing is using the vacuum that the heated air in the chimney will create to draw cool air in from the air inlet (described above). It's only good for cooling down the shed when I'm not using it - as the roof will hinge off when I'm using it. But I hope that will make the whole thing a little more thermally sensible. I've got some insulshed that will line the whole thing. Best to jump in and experiment I say.

[baileys2611]

Some shots of the shed going up and how the pier is looking.

Shed took some pounding on the weekend with very strong winds. It wasn't easy putting this thing up in those winds - but once all four sides were in place it's very stable.

[ZeroID]

Looking good so far. My roof rotates sideway 90* to open. Much easier than having to balance a flipped over roof with rods or ropes etc. I just unclip the restraints, lift it gently with my hands and walk it around. Had to strengthen the upper wall top 'rail' to stop flxure but that was just some 6 x 1 (150 x 25) timber secured and braced in the corners.

[baileys2611]

Getting there. Here are some pictures of the shed with insulation, pier preparation and pier mounted with MDF on the walls.

[scagman]

Hi Simon,

Its coming on really well. How did you compensate for the curvature of the tank. The peir looks really good too.

Cheers

[baileys2611]

Thanks John,

The tank is actually quite flat, there are points where it dips and rises but in general no more than 2 or 3mm at any point. It was poured when the house was first built - so it has an 11m diameter on the top, goes down 3.5m and is currently about 3/4 full of water. We use a fair amount being a family of 4 (3 females and me) but the rainfall here is pretty good.

Any dips or rises were taken care of by putting some aluminium angle down first, then attaching the shed sides to the up-right part of the angle. This had the effect of levelling out any bumps without needing to pour concrete.

Silicone helped a bit too...

Here's a shot of the aluminium going down first, you can see the upright part of the angle? That's what the shed was riveted on to. I added more angle the create a box frame first, then put the shed on to that frame.

[baileys2611]

Passive cooling using a solar extractor fan on the top of a tall chimney, air intake off the overflow from the water tank: Water cooled air coming in, hot air being taken out.

The effect is variable depending upon conditions, the hotter it gets outside the more effective it is but on average I get a 2 degree temp below ambient temperature.

Insulation and wall coverings help.

It's ready for a lick of paint and some very thin ply on the roof and doors.

[baileys2611]

I've yet to get some plywood for the doors and roof, but the rest is finished. Now, time to put the scope in place and get some viewing time!

[ZeroID]

Looking good !
Fortunately we don't get the big temp swings you guys seem to get and my tinshed is in a protected enclosure out of the worst of the sun so no requirement for insul or vents. Leaks enough air to stay about ambient and not need serious venting.
Won't the chimney get in the way of viewing somewhat or are you blocked on that horizon anyway ?

[baileys2611]

Yes it will a little bit - but that's ok, the mount will be high enough that it will 'see' over the sides of the shed, the chimney however is going to block some sky if I want to look that way.

It's something I'll need to put up with...:shrug:

However you are right, the temperature gets high for a small amount of time during the year, but I wanted to make sure that my equipment suffers as little stress as possible during those times.

[ZeroID]

Does it need to be so high then ?
Or can you outrigger it a bit further away from the wall ? Longer horizontal pipe.
Lean it away at 45* maybe?
Or you could even set it up so it swivels down out of the way when required ... pinned to hold position when vertical.

We're full of ideas !! :thumbsup:

( I like the swivel idea actually )

[baileys2611]

:lol: Yes, many ideas!

It doesn't need to be so high - but the idea is that it creates a vacuum with the hot air rising, I wanted as much vacuum as possible so straight up seemed the best option. The solar extractor was an afterthought to assist...

Yes, it could definitely lean, that wouldn't change the air flow much I suspect but would likely have the same effect of limiting views at that point. It's 90mm wide (might look wider) which equates to about 10 arc degrees at the point where the scope is mounted. I've been observing on that spot for about two years now and notice I'm pointed up or to the South or West mostly. I figured 10 arc degrees to the North would be ok.

Swivelling is a good idea! BUT, one of the other concerns was making sure that no moisture came in via the hole in the wall on the other side. Any break would lower the vacuum but also be a potential point for water to enter...one day when I sell the gear and upgrade I wanted to make sure it was stored in something that was safe for the optics, a little moisture is ok but too much and I would risk the humidity going up too much inside. I had to put a filter of activated carbon stuffed inside a stocking and wadded with some fish tank filter foam to make sure that I removed the moisture from the air intake.

It's a compromise for me. If I had my druthers I'd be buying that nice home dome Rob has on sale here, or better yet buying a larger one for double the price! Budget reality check though :sadeyes:

[ZeroID]

My Ob leaks air in all over the place, roof edge\seal, wall bottoms, corners, door 'seals'. As long as water doesn't leak in it allows the gear to stay dry. Guess I'm lucky in that we don't have too many nasties to cause other issues But I don't think I'd be worrying about drying the air with activated carbon etc. I'd be going for volume of air through to shift any residual dew etc from the previous night. The carbon won't dry air, it's for filtering fine particles out. Dessicant is the drying agent but no good for large volumes of air flow at all. You'd need a dehumidifier to fix that.
Pull the air from down low, fine mesh filter to keep the nasties out, ditto for the top vent, get some serious airflow going. Your carbon won't do anything except block the air flow.
Use a vertical slip joint on the vent, just drops down onto the elbow and can be removed when necessary.

[baileys2611]

Hmm...very good advice. Yes - I think I'll follow it...I'll remove the carbon and go with air flow instead. Must do some research on the vertical slip you mention and see how that works. I've got a small 12 volt fan I was planning on placing over the air intake (which is down low) which would be powered from the solar cell and battery to assist air intake - but when I'm viewing I don't need the chimney.

It's secured with some bolts that go all the way through to the inside as we get pretty high winds - how would it be secured when I'm not using the obs do you think?

[ZeroID]

You will probably find that the vertical pipe slips down over the upward facing opening of the elbow, instant slip joint, no leaks. Pretty stable.
If you going to get plenty of heat I doubt you'll need the fan. The airflow could probably run a generator in fact !
Keep it simple, you can always make improvements later if required. The 'Critter mesh' is probably your most important fix.

[baileys2611]

Thanks to Logan for some good advice and for those that helped me with a wise decision. I've put up some pictures of my new mount and the set up I have inside my obs. :thumbsup:

[ZeroID]

Geez, it's a home away from home !! Makes mine look like a .... tin shed !
I like the red 'decorations', particularly the one in the middle of the room. :thumbsup:
Have you tested to see how well the shed floor is isolated from the pier ?
You will now find you'll start to get your moneys worth from the setup now.
How does your roof system work ?

[baileys2611]

Thanks, I had some fun with the decorations :rofl:

I have tested, the pier is mounted on a raised slab which does not come in contact with the floating floor, so as long as I don't jump up and down with excitement then there's no vibration at all. The whole thing is on my in ground water tank though, so if I jump up and down anywhere on the tank then the vibration comes through - however just being 'normal' and moving around does nothing. I can move in and out of the obs and around the tank without a problem.

The roof is just a set of shower screen rollers screwed into the side of the shed roof, which rolls on and off some aluminium t frame that I out on top of the walls as a guide track. Manual on and off but it leaves room for automation some time later on :D Got to have room for improvement somewhere :P

I've got some shots of my equipment actually on the mount now, they're on the twitter page - or will be soon when twitter decides to come back!