Astrokev

Why does everything always take 3 times as long as you expect? I did spend an age deciding what size screws, bolts etc I needed, and then visiting Toolstation, so that dragged things out a bit. In the end I opted for stainless coach screws for the track, since these will be exposed to the elements. It also took me a while to figure out the best way of cutting out the holes for the wheels. Could really have done with a router but had to make do with the cordless drill, rasp and chisel.

Anyway, managed to finish the East rolling rail. The track isn't screwed down yet; I'll do this when both rails are complete and I've aligned the tracks to ensure they're parallel and square to the north dividing beam. Recommendations from other builders say to spend time getting the alignment as good as possible, so intend to do just that ? 

Have to say that the rail rolls so easily and smoothly! I hope it's the same when it's taking the weight of the roof and EPDM!

In the first pic the rail is upside down!

Well, not a huge amount to show today but at least I've restarted construction, and significant in that I've finally started the rolling roof!

Spent the morning playing with my little grandson ?, then in the PM I searched through over 30 lengths of timber and finally managed to find 2 that were not twisted, bent, damaged or split, to use for the wheel beams. I love Wickes!

So didn't have much time to start sawing, but did manage to cut one hole for the first of the 6 V-wheels, 3 per side. Although not yet fixed to the beam, the pics below show the design I'm using. The last image is upside-down to show the wheel design for anyone unfamiliar with such things. I must say I like this wheel design, the weight of the beam and roof acting vertically on the fixings which feels very secure. My plan is to cut the 3 holes I need with a small amount of lateral play, and drill the bolt holes with similar lateral play (effectively short slots rather than round holes), to allow me to adjust the alignment as best I can before tightening the nuts on the bolts. Well, that's the theory, I suspect it won't go as smoothly as that!

With good weather forecast for tomorrow, hopefully I'll get a few more holes cut ? 

Not much to show over the last few days but I've been busy re-designing the ROR, when time allows. This is to increase the clearance above the warm room dividing beam. 

Hoping to start more construction this week ?

Your obsy's been up for several years now so clout nails clearly work just fine!

Just checked out guttering. I think the mini-guttering should work fine. The full scale stuff looks huge and seems over the top for my little obsy!

56 minutes ago, Gina said:

I didn't use contact adhesive on my roof.  I was surprised how easy it was to use the EPDM rubber roofing.  I used clout nails to hold the edge down up under.

That clearly works well and I guess I could've done similar. Rubber4roofs recommend using the adhesive though, so thought I'd follow their guidance to avoid risk of problems down the road - this roof is designed to outlast me and require zero maintenance!

I seem to have loads of useful large offcuts already (I may have added too much size contingency!) so need to think of creative ways of putting it to good use. I'll probably end up putting it with all the other "useful" bits n bobs that I've collected over the years ?

Having done both I agree. The contact adhesive is a pain around the edges but getting the EPDM down and flat is fairly straight forward and easier than felt. 

6 minutes ago, JamesF said:

I swear I have no idea where they've all come from.

James

Collecting scopes is a competition between astronomers. The one who has the most when you die is the winner ?

9 hours ago, JamesF said:

I was tempted by a C11 for sale near here recently, and there's still a 12" Meade SCT not far away too.  I have promised myself no further telescope purchases until the obsy is weathertight though (at which point I probably won't be able to afford any more anyhow

James

Yeah, from your profile I can see that you are clearly a bit short in the scope department ?

Well I had to have a quick play with the C11 didn't I? And yes, it's lovely.

Then I squeezed in an hour on the obsy. Finished sticking down the EPDM over the beam which means I can now start work on the rolling roof!

Still a few bits to finish off on the warm room roof, but these can be done anytime - making holes in the EPDM on the beam facing the scope room to re-open the ventilation of the roof space; stick down the EPDM on the edges of the rails; fit battens at the rear and on the rail edges; trimming excess EPDM; fit guttering.

Haha. 

Sorry Neil, I didn't realise I had to complete the build in under 10 pages. I must try harder ?.

I seem to recall Gina's build back in 2011 was over 45 pages ? so I have a bit to go yet ?.

In a bit of a dilemma.

Just picked up a nice shiny second hand C11 and Moonlite focusser. ?

So, do I do some more work on the observatory while the weather's nice, or play with the new toy ?

5 hours ago, Markh68 said:

Great build so far Kev been following it keenly since the start. Cannot wait until you build your rolling roof.

Planning to do a build myself very soon 

Thanks Mark. Yes really looking forward to starting the rolling roof too!

Good luck with your build - be sure to post lots of pictures!

5 minutes ago, JamesF said:

Steady on.  If you make it look any nicer you won't want to put up a ceiling.

James

Haha ?

Couldn't face doing any more EPDM work this evening, so decided to nibble away at a few jobs inside the observatory instead.

One satisfying job was to seal the warm room roof insulation with foil tape. Looks a lot tidier -  it's a bit of a shame that it will get covered up when I fix the ply sheet to the ceiling! Here's a before and after shot....

2 hours ago, yesyes said:

This would probably be good to use the contact adhesive for.

 

Thanks Chris. Yes, I've used contact adhesive to stick ~100mm around the edges of the "flat" section of the roof, and also for the track rails. It sticks instantly, so you have to be really careful when mating 2 surfaces. Get it wrong and your stuffed! It therefore doesn't need clamping. I've found that finger pressure and then using a small roller does the job nicely. I intend to use it for the fixed beam also, as you suggest.

Here's the progress from yesterday - and a bit of tidying up today.

All surfaces glued down except for the fixed beam separating the warm & scope room (I'll do this tomorrow), sticking the EPDM to the sides of the rails, and then trimming the excess. I'm quite pleased with how the corner pleats turned out. Acid test will be to pour a bucket of water over it to check no water can get in.

Haven't decided what to do about battening yet. The more I think about it, a piece of aluminium bar across the rear of the roof would act as a good drip-bar and would outlast a wooden batten, so may go this route. Also need to erect some guttering. I didn't think of this when I was designing my build, which focussed mainly on the woodwork, so I may need to be creative as I haven't got a vertical surface to attach the gutter brackets where I need them. I'll need to fabricate something suitable.

10 hours ago, yesyes said:

There is no noticeable deformation. Most of the weight of the roof isn't in the middle of that beam. It's more spread out.

I do notice a bit of give and take in the timber depending on the weather (humidity mostly, I think).

 

That's a good point Chris. The total weight will be taken by the 3 cross-beams, each of which will be supported at the ends. Some of the load will therefore be directed down through the walls of the main structure, reducing the load in the middle span of the cross-beams. There's probably an engineering formula to calculate the load in the middle but that's a bit beyond my knowledge. I used the same technique with a garden shed rebuild a few years ago and the apex beam can easily take my full body weight. I'm probably worrying unduly, but may redesign anyway just to be sure. Overengineering - I love it!

5 minutes ago, JamesF said:

A 280mm diameter tube 1.3m tall, Kev?  I reckon that's only about 160kg

James

Speaking metaphorically of course ?

1 minute ago, Gina said:

I might go for this if I decide to build another pier for telescopes.  Much cheaper than a Skywatcher Pillar mount at over £200!

...and an air-con tube filled with a ton of concrete. My back is still aching!

22 minutes ago, JamesF said:

The plan is to use gorilla glue between the mating faces combined with lengths of M10 studding.  If it doesn't work then it's a £40 experiment that failed.  If it does work then it saves me a huge amount more.

 

Sounds like a plan. I guess the only risk is that the blocks may crack when drilling, but sounds workable.

Well, the planets finally aligned and I laid the EPDM today. With hindsight I think it may have been better to choose a cloudy day. I initially took my shoes off to walk on the roof and when the sun came out the rubber was almost too hot to stand on (brought back childhood memories walking across boiling sand on the beach!).

The water based adhesive was fairly easy to work with, although it was a little too quick to dry in the mid-day heat. The contact adhesive was horrid, drying almost before I could get it off the roller or brush. Once I got used to how it handled I managed OK though.

First job was to fix the corner pieces (see several posts ago for images and logic for this). A bit tricky to slide the rubber between the roof and the side rails without the 2 adhesive coated surfaces touching until I was ready (manoeuvring 1.2mm rubber in a 2mm gap was a bit tight ?), but was surprised that I managed to get them fixed first time without problem. Images below. Once dry I trimmed the top edges then cut and stuck down the main sheet. The lower corners proved as tricky as I suspected and it took ages. By the time I'd finished in the early evening I was too shattered to remember to take pictures so will post these tomorrow.

Just a bit of tidying up to do and put up some kind of barge board along the rear edge. For the sides of the track rails, rather than use clout nails, I'm wondering whether to use an aluminium strip which would be thinner (than a timber batten) and may look more attractive than nails. Clout nails would work fine I guess so I must think about that one ? 

37 minutes ago, yesyes said:

I've not had anything fall in from the roof (maybe the odd tiny leaf that I didn't notice) and I don't open it when it rains or just after rain when it's still wet. I've not seen a problem with this yet. But it may be different in different surroundings.

The alternative is to have the apex rotated 90 degrees, parallel to the roll-off direction. But in my case this would have made the building too high for the 2.5m limit. And I think the captive mechanism on the sides would look weirder ?

 

Thanks Chris.  Have you noticed any deformation of the apex beam across the obsy due to the weight of the roof? I'm wondering whether I need to strengthen my beam and increase the clearance of this over the fixed beam separating the warm room and scope room. My current design has a clearance of around 30mm.

Looking good. Interested in seeing how you will join these together.

7 minutes ago, JamesF said:

Good point.  Increasing thickness doesn't increase rigidity anywhere near as much as increasing depth.  However, you could perhaps use some steel or aluminium bracing?  Perhaps a piece of angle iron or similar screwed or bolted to the inside of the timber?

James

Yes that's a thought. I did that many years ago to increase the rigidity of a kitchen worktop that spanned a washing machine and tumble drier! Worked quite well as I recall.

10 minutes ago, Gina said:

I have a similar design but with a higher apex and have had no problem of that sort.  What could be on the roof and fall off into the scope room anyway?  Mind you, mine has a gutter on the end away from the warm room roof.  Water from the sloping part over the warm room simply deposits rainwater onto the warm room roof and into the warm room gutter.  There are ridges on the sides of both roofs to stop water running off the sides.  Actually, because the ROR is wider than the warm room roof, there are short pieces of guttering to collect water from the ROR not over the warm room and deposit it onto the warm room roof.

Thanks Gina. Yes, mine will have a gutter on the south end which will hopefully prevent water getting in when I open it, and may also catch other bits of debris. I must give this some more thought though to make sure I position the gutter correctly to act as a trap.

Regarding the risk of the apex beam deforming, I'll relook at the clearance. I may be able to increase this slightly, although I think I'm pretty close to the 2.5m limit ?