Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Gina's Observatory


Gina

Recommended Posts

I had thought of that too but I thought the problem with that was that you would have to space the joists too far apart due to the size of the concrete block.
I hadn't intended to have the block between joists and the block is 700mm wide at the western side. Yes, a bit on the wide side, but I've put the pieces of 5x2 at this spacing and the piece of 20mm floor board on top and jumped up and down on it. It moved about a mm or so, which I think would be satisfactory. (Should be a bit less with 25mm floor boards.)

Since I shall be hanging the joists from the beams, the two either side of the block could be deeper than the others - say 6x2.

Link to comment
Share on other sites

  • Replies 1.2k
  • Created
  • Last Reply

Can I throw something in the mix. Try not to think about too many drop down walls as this could lead to a weak structure. These sectional buildings rely on support from adjacent wall sections, and taking some of that away might cause problems later on. This can be compounded when you try to make the roof structure from larger section timber, which thus increases the weight of the ROR section. This is compounded if you opt for a split wall that runs off with the roof over the top of the other section.

One thing I did like with the Alexander design is that the roof was full length, so what was covering the scope when closed ends up covering the warm room. The drawback is that you need an additional 8' to take the rail supports out the back on which to support the other half of the roof when rolled back. If you have room on your plot then maybe this might be worth considering.

I have to disagree with the statement about getting it right 1st time everytime.. whilst you can draw up how you think it would all go together, and have imagined how things work, when you actually start working on that area you sometimes change things on the hoof as you then see a better way of doing it, or you have to compromise to cater for a previous mistake / oversight or accident. This you have already encountered with the pier.

Personally, IMHO, changing the bolts for some longer ones, and raising the base plate for the mount by another 3cm is the simplest and logical amendment to your plans. Changing the whole structure, flooring supports etc is a major and time consuming fix.

Link to comment
Share on other sites

The block in my above post is about 700mm square, you can't see it because its flush with the top of the joists, the bit you can see is added on and a bit smaller.

I had the same problem as you so retro fitted another lump on top of the original block, but the hole cutout and joist layout was to my original plan. With the noggins in place there is no flex in the floor at all.

Link to comment
Share on other sites

Gina I'd be quite happy to do any of the welding, drilling etc for you. Unfortunately, the cost of sending the bits would probably be more than getting it done locally.

I still think altering the pier is the easiest and cheapest. I can see further problems arising from major construction change for a simple problem.

Offer is always there if you want to defer it until later.

Link to comment
Share on other sites

Hi Gina, just a thought, would threaded tube do? (the size of the thread out of the pier) and extend a few inches with more bar - then pour a new cast over this to get the hight needed?

Glen

Link to comment
Share on other sites

Can I throw something in the mix. Try not to think about too many drop down walls as this could lead to a weak structure. These sectional buildings rely on support from adjacent wall sections, and taking some of that away might cause problems later on. This can be compounded when you try to make the roof structure from larger section timber, which thus increases the weight of the ROR section. This is compounded if you opt for a split wall that runs off with the roof over the top of the other section.
I quite agree and have rejected this option for that reason.
One thing I did like with the Alexander design is that the roof was full length, so what was covering the scope when closed ends up covering the warm room. The drawback is that you need an additional 8' to take the rail supports out the back on which to support the other half of the roof when rolled back. If you have room on your plot then maybe this might be worth considering.
One option I know but I don't want a structure sticking out. Hence I have rejected this option.
I have to disagree with the statement about getting it right 1st time everytime.. whilst you can draw up how you think it would all go together, and have imagined how things work, when you actually start working on that area you sometimes change things on the hoof as you then see a better way of doing it, or you have to compromise to cater for a previous mistake / oversight or accident. This you have already encountered with the pier.
Yes, that's true. What I meant was that it's not good to skimp.
Personally, IMHO, changing the bolts for some longer ones, and raising the base plate for the mount by another 3cm is the simplest and logical amendment to your plans. Changing the whole structure, flooring supports etc is a major and time consuming fix.
Since I haven't built the floor yet (only done the beams and their supports) or even ordered the timber, getting joist hangers for hanging the joists and an extra saw cut per length of timber, is no problem. Adding 3x3 to the beams is also no problem - I even have a large number of M10x180mm threaded coach bolts and nuts, so I can easily spare 6 or 8 to attach it. (Or I could bolt the end frames direct to the beams and save the 3x3 timber.)

The benefit is that I can save 5", equivalent to adding that height to the pier adapter and making the bolts/rods 7" high. An extra five inches effective height for the pier saves that much on each side of the roll off section, saving weight and increasing rigidity. It also reduces the obstruction to the westerly view from 30 degrees above horizontal to 20 degrees. This is a case of altering the design as the build progresses to counteract mistakes. In fact two of them. Not securing the threaded rods well enough and miscalculating the best height for the pier. It could have been 6 or 8 inches higher. There would still be plenty of headroom for the scope. I guess I could add to the pier adapter and improve things still further :) I wouldn't like to add too much though and reduce the rigidity.

I much appreciate your opinion but in this case I beg to differ :eek:

Link to comment
Share on other sites

Hi Gina, just a thought, would threaded tube do? (the size of the thread out of the pier) and extend a few inches with more bar - then pour a new cast over this to get the hight needed?

Glen

Thanks for the suggestion but I would prefer no to do this as I'm told a join in the concrete produces a weakness - good thought though :)
Link to comment
Share on other sites

One doesn't make mistakes, one simply changes their mind... :eek:
Nice thought :)

I've realised how I got a bit out with the pier height. Before doing anything I checked how high I wanted the pier and adapter. To do this I set up the mount on its tripod where I was going to use it, at ground level of course. I measured from ground to bottom of mount and designed pier plus adapter to be at this level. That was from the bottom of the lower plant pot to the adapter top. The original plan was to have the bottom of the lower pot at floor level with the floor cut out to miss the pier base block.

Then later I changed my mind and decided to have the base top just below the joists so that I could have the joists closer together and have a smaller, round hole in the floor. But I didn't increase the pier height to compensate. That's why the pier worked out lower than initially intended.

So to put things right I could/should go back to my original design to have the pier base as near floor level as possible/reasonable. It was also in line with the original plan that I dug the area out to the depth I did - it was designed to clear the bottom of the joists by a couple of inches. Then deeper troughs for the beams and deeper holes for the beam supports and pier base. It also explains why the beam supports seemed so deep - I had intended the beams to be 4.5" lower in my original plans (4x2 joists and half inch plywood).

Thus the ground level within the outline of the shed is already well deep enough to have the top of the joists and beams at the same level. There is nothing stopping me going back to my original plan of pier base near floor level by simply hanging the joists from the beams rather than sitting them on top. As I said in an earlier post, the various snags were addressed and solved with suggestions from others on here.

Link to comment
Share on other sites

Been working everything out and have the design changes worked out. At the same time I've sorted out how the roll off section ends fit with the rest of the structure.

Having checked prices and amount of work involved in using galvanised steel hangers I have decided to use 47mm square timber attached to the sides of the beams to support the joists. Screws through the beams into the ends of the joists will hold the joists in position before fitting the floor boards (I was originally going to use long wood screws down through the joists into the beams). This method is both cheaper and less effort than hangers.

I am also going to raise the upper pier adapter plate by about an inch (25-30mm) using longer bolts and extra washers. This shouldn't affect the rigidity much and apart from saving height of the roll off section and increasing westerly view, makes for easier access to the centre bolt.

I'm also considering dispensing with 5 degrees of northerly viewing angle - going from 15 degrees above horizontal to 20. This would save another 5" and reduce the northern roll off height to around a foot. With 122x38mm wide uprights and 100x38mm end members of the roof frame bolted together I think I should get enough rigidity. The south side would be around 30". With the north side providing the main sideways stability (running in aluminium channel), the high south side should be OK with similar ali channel providing additional security at the bottom.

Here's a rough sketch of the cross-section through the pier, walls and roll off part which I hope will make this clearer :-

post-25795-133877639524_thumb.png

Link to comment
Share on other sites

Its rock solid when in place and has the ends designed to fit into the same contours as the top of the tripod and base of the mount.

PM me your address and ill send it your way, if it does work for you, we can sort something out. :)

Link to comment
Share on other sites

Its rock solid when in place and has the ends designed to fit into the same contours as the top of the tripod and base of the mount.

PM me your address and ill send it your way, if it does work for you, we can sort something out. :)

Thank you very much :eek: PM sent.
Link to comment
Share on other sites

Now have the extension tube from Earl and looking at how to get over the lack of the attaching bolt. I'll post more about it later.

Link to comment
Share on other sites

I think if you turn the lower plate which should go into the tripod upside down and attach into it from the underside of your pier it should be fine.
The lower plate will fit in the hole in the adapter plate as it is.

The problem is not attaching all the bits together but to find a way of releasing the top bolt to allow polar alignment. It's inside the extension tube.

Link to comment
Share on other sites

Isn't it a simple case of getting a longer bolt. Just a thought.
Yes, I think it is, except that the holes in the extension tube top and bottom plates are threaded and the same size as the mount.

I'm attaching a rough sketch of the tube cross-section. The strange thing is that both top and bottom plates have threaded holes. The top plate is very similar to the plate on the tripod and that also has a threaded hole. The supplied tripod attaching bolt has a reduced cross-section to clear the thread. I imagine the supplied attaching bolt for the extension tube has two reduced sections too clear the threads in the same way. If so I wonder why the bottom plate (which seems to be designed only for the extension tube) has a threaded rather than a clearance hole. Maybe Earl or someone else who has one of these bolts can confirm this or tell me how it works, please.

My first thought is to drill out these threads to clear a long bolt. Then mount, tube and adapter can be held together with one bolt, with the bolt thread going into the threaded hole in the mount.

Attached sketches :-

1. Extension Tube X-section,

2. Using one long bolt to attach mount, tube and pier adapter.

post-25795-133877640097_thumb.jpg

post-25795-133877640101_thumb.png

Link to comment
Share on other sites

The lower plate will fit in the hole in the adapter plate as it is.

The problem is not attaching all the bits together but to find a way of releasing the top bolt to allow polar alignment. It's inside the extension tube.

You dont need to adjust the bolt to get alignment, the adjust should work with the bolt done up firm, if they really dont want to move a thin sheet of teflon between the mount and the plate it rests on wil help (this is what i have done)

Link to comment
Share on other sites

The original Tripod bolt is used to attach the Base of the extension to the tripod, inside at the top there is a smaller version which you have to attach to the mount. that's the bit i used to attach my mount to my pillar.

Link to comment
Share on other sites

Thinking about it I would recomend you use two bolts.

One to attach the top base of the pillar to the underside of the mount, as you can see from the 3 hex bolts its easy to take off the ends, and then attach the bottom plate in the same way.

Link to comment
Share on other sites

Gina,

The bottom threaded hole I guess takes a standard bolt - the top looks as if it takes a bolt with the thread removed near the bolt's head to form a captured bolt so it doesn't fall out as you struggle with the mount and try to do up a bolt from underneath...

Once you've screwed the bolt through the threaded hole, the bolt's plain shank will allow the bolt to be easily handled to 'find' the thread in the mounts base and will then tighten as a normal bolt...

Just a thought - Francis

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.