Astrokev's Obsy Build

[Astrokev]

Captive mechanism - yep, definitely need this. I was thinking of keeping this simple, using turnbuckles (is that what they're called?) to hold the roof down when closed. When it's open, I'm less worried because I doubt I'll be doing much observing if there's a howling gale blowing .

I'll take a look at your suggested link though - always keen to pinch ideas better than my own!

Thanks

[Astrokev]

Perhaps the inclusion of some kind of captive mechanism to help prevent the roof going airborne if there's a strong gust of wind?

Haha, just checked Mike's thread and realise that I praised his captive mechanism in post #73 (memory like a goldfish - probably an age thing!).

Yep, I'll certainly revisit my design to see whether I can do something along those lines.

Thanks guys for the memory jogger.

[yesyes]

Mike's mechanism has several advantages over turnbuckles

- you can't forget to tie it down

- it doesn't take time to undo

- the roof can easily be motorised and remote controlled

[Astrokev]

Mike's mechanism has several advantages over turnbuckles

- you can't forget to tie it down

With reference to my last post, the evidence would strongly suggest you're right there!

[Gina]

I'm thinking I could do with some other anti-lift mechanism than the peg and hole system I have at present, which requires quite accurate alignment to engage.

[r3i]

It's belts and braces really - I have the turnbuckles as well! It gets quite windy round these parts so wanted all the protection I could get. The 'captive mechanism' is hopefully a good backup - good point about the potential to forget to fit the turnbuckles. It is also there just in case there's a sudden gust of wind from nowhere when you have the roof open. After reading many accounts of roofs taking flight I didn't want to take any chances: when it's forecast to get really windy I strap the roof down as a third level of protection - paranoid? Moi?

[Astrokev]

I think I've finalised my design for the rolling mechanism. Thanks to all for the helpful feedback and ideas (some of which discussed in other threads). Not shown in the diagram is the cladding on the roof end wall, so that the design for the castors and main roof frame can be seen. The vertical studwork hanging off the roof will be attached to each roof joist. The black lines will be rubber roof material.

For the castors, I've decided on 80mm Screwfix nylon wheeled. These will eliminate the risk of rubber tyres developing flat spots. The castors will run on ali U channel. I'll add some form of brush to clear the U channel during opening, and brush strip along the side studwork between the roof and the wall rail.

When I have some time I'll add my roof to a 3D sketch to make it easier to see how this works in 3 dimensions.

The problem I'm now struggling with is how to design the join between the end of the roof and the end outside wall of the scope room (not the join with the warm room). Ideally I want a proper seal to keep the weather out, rather than just a hanging strip of DPC / rubber. I think I can only achieve this by having the top of the scope room wall hinged to form a fold-down panel which could be raised to form a seal on the inside of the scope room when the roof is closed. Saying that, it's still tricky to design a good seal around the end of the rails.

Any ideas of how others have dealt with this would be warmly appreciated!

Thanks

[r3i]

The problem I'm now struggling with is how to design the join between the end of the roof and the end outside wall of the scope room (not the join with the warm room). Ideally I want a proper seal to keep the weather out, rather than just a hanging strip of DPC / rubber. I think I can only achieve this by having the top of the scope room wall hinged to form a fold-down panel which could be raised to form a seal on the inside of the scope room when the roof is closed. Saying that, it's still tricky to design a good seal around the end of the rails.

Actually a strip of EDPM is all I have and it has been surprisingly effective. It was a bit left over from the roof covering, I originally put it on as a stop gap until I could work out something more sophisticated but in the end I've just left it there as it has done the job admirably. Since taking the pic below I've added a couple of extra squares of rubber over where the rails end as I had a little bit of snow blow in there.

[Astrokev]

Floor joists....

I'm planning on using "standard" floor joists. What sort of spacing should I use for a ply boarded floor?

I know I've seen this in other threads, but don't seem to be able to find this at the moment!

Thanks

[malc-c]

Floor joists....

I'm planning on using "standard" floor joists. What sort of spacing should I use for a ply boarded floor?

I know I've seen this in other threads, but don't seem to be able to find this at the moment!

Thanks

My joists were 6" x 2" spaced at 16" centres with staggered cross bracing

[Astrokev]

Thanks Malc.

I've also been looking at timber for a wall plate. Wickes stock 19 x 100 which looks OK, but I'm concerned it may be a bit on the thin side. What size did you use for yours - I'm guessing from the pics that it's about the same? Ideally I want it to be thick enough to take screws from the wall studwork. Alternatively, I could put the ply floor directly onto the wall plate to make the base thick enough to take the studwork screws.

Finally started buying stuff this morning ( :laugh: ). Popped in to Screwfix and picked up a set of 80mm nylon castors to enable me to measure sizes so I can figure out what size channel I need. The castors are actually a llittle bigger than I expected. I think they'll be OK, but wonder whether I should've gone for the 50mm version. Oh well, done now.

Kev

[malc-c]

Kev,

The joists were 6" x 2" (150mm x 50mm) purchased from a local builders merchant and I was pleased with how true and straight they were. These were fixed at 16" centres by hanging then in galvanized joist hangers as per the images. I then used galvanized nails to fix the 18mm external grade ply to frame and joists, once the joists had been given a coat of preservative, and the installation (50mm thick) in the warm room had been installed.

I've looked back at my costings spreadsheet, but didn't list the individual costs, but the joists and flooring (11 x 2.4m joists and 4 x 2.4m x 1.2m sheets of marine ply) came to £190 inc VAT. But the timber was 1st class and far better than wickes

[malc-c]

I too placed the studwork ontop of the floor so the frames could be screwed through the floor and wall plate to give better purchase. At the time it was suggested that fitting the frames to the wall plate and then fitting the floor inside the frames would allow the floor to be replaced without the need to dismantle the building. But to be fair, unless you get it really wrong and the floor is constantly being exposed to rain (which I doubted) then there should be no real reason you would need to replace the floor, at least not for some decades !!

My casters were 50mm rubber from Screwfix ( http://www.screwfix.com/p/rubber-tyres-fixed-50mm-pack-of-4/94751 ) Three packs with 6 wheels either side - no problems with the roof in the past two years - still as good as it was the day it was first put up

[malc-c]

Actually a strip of EDPM is all I have and it has been surprisingly effective. It was a bit left over from the roof covering, I originally put it on as a stop gap until I could work out something more sophisticated but in the end I've just left it there as it has done the job admirably. Since taking the pic below I've added a couple of extra squares of rubber over where the rails end as I had a little bit of snow blow in there.

Mike,

I did the same down the side walls as well as I had a lip above the door which meant I couldn't fix anything solid. Two years on and it's holding up a treat - and the obsy has remained dry. - that DPM has a 1000 and 1 uses