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Hi guys,
For reasons that must forever remain hidden from my wife I have decided to enlarge my observatory.
I’ve bought a good quality 9 x 8 pent-roof shed and intend to fit a roll-off roof. (It may turn out to be a “fall-off’ roof depending on how the design vis-a-vis “gravity versus a small Geordie” goes!).
The construction of said shed lends itself to easily raising the roof on castors and rails. It will then slide down (and hopefully up) with relative ease. Or with the aid of a simple pulley and spring/brake. From what I’ve seen of other examples, extending the eves and allowing a flap at the opening/closing edge seems an easy weatherproof solution.
I guess the wheels are obtainable from B&Q etc but what have people used for the ‘rails’ and/or guides?
Any other construction suggestions, do’s/don’ts or examples would be most welcome.
I intend to sell my single-bay Skyshed Pod after this is all done and I’ll ‘publish’ the results of the project as a learning exercise – or simply to provide a laugh.
Regards
Tony
Hi Tony,
My observatory is a roughly 6’x4′ run off shed with the entire building rolling off so I guess the overall weight is not wildly different to your run off roof. Also because I have built on a sloping site the rails are supported on short posts not resting on the ground so the rails are taking the weight not the ground. So again there is a similarity to a roll off roof.
For the rails I have used 70mmx45mm pressure treated timber from, I think, B&Q. The wheels run on the 70mm face and the weight is therefore supported by 45mm of timber. There is an important point here however. The shed runs on eight wheels, four on each side, and each rail is supported on eight posts. These posts are arranged such that whenever the shed is fully open or fully closed the wheels sit directly over a post so the load is transferred straight to the ground and there is no opportunity for the rail to sag under the weight of the shed. I would strongly urge you do something similar.
The guides are quite simple. Most DIY superstores sell lengths of 10mm threaded rod and matching nuts and washers. I cut four roughly 25cm lengths of the rod and mounted one at each corner of the shed frame extending down beside the track. From simplybearings.co.uk I obtained four roller bearings. These slide onto the end of each rod, are held in place by nuts and washers and roll against the side of the track.
For what it’s worth the wheels I used for the shed were these.
The observatory has been in use for a couple of years now and so far there have not been any problems.
Regards,
David.
I would add two points. Firstly I only put a guide rail on one side. This avoids binding if they are not exactly parallel.
Secondly, the load is quite high so use wheels with roller bearings.
Good luck Andrew
I covered many possibilities in my book “Setting-up a Small Observatory’, (Patrick Moore’s Practical Astronomy Library), still available from Springer, with descriptions and photos of methods of construction various people have used.
I used treated timber rails and guides and plastic rubber-tyred wheels, and, about 12 years on, this is the one part of my construction that has failed and needs replacing. The problem has been that wear by the wheels (even though there are lots of them, spreading the load widely) caused groove formation on the rails, which allowed water to stand, and the eventual decay of the rails. I build the shed in a modular fashion so it is not that difficult to replace the rails, as I anticipated this might be necessary. I can’t see any ultimate solution, other than using metal. Aluminium of the scale required however would be expensive, and steel is very heavy. I did try just surfacing the rails with aluminium, but that caused a different problem: water got capillarised in through the narrow gap. I intend to replace with new timber, but I may try varnishing with yacht varnish or something hard and hard-wearing, in an attempt to increase durability. But in the end none of these solutions last for ever, and 12 years is not too bad.
I built my current 10ft x 10ft roll-off roof observatory about 12 years ago. This was built from the ground up and not based on an existing shed.
For the runners I used angle iron from a local agricultural blacksmith (I live in a rural village, so easy to obtain). I suggest angle rather than channel to avoid side pinching. For the wheels I used 75mm Non Marking Wheels from B&Q, 4 on each side. These are plastic wheels with a hard rubber tyre and 8mm central hole. I though these might fail under regular use so I bought some spares but have never needed to replace them. Reference numbers on the package (whatever these might mean) are H29566 and 9436701. The biggest problem was transporting 20 foot lengths of angle home on a car roof rack. I’ve been very pleased with the observatory and would do the same again.
Good luck, Stewart
The rails are (obviously) the main addition to the construction.
I’ll take David’s advice and double varnish/cover the rail areas and overlap end covers. I’ve got some liquid rubber that I’ve used previously and this has proved effective. Although, I’m using a pent roof shed so would not expect to suffer from standing water. (Hope not anyway!).
Stewart’s recommendation is along the lines I was thinking. In my case I’ll try angle aluminium. (David’s comment on weight being the factor here). Those wheels sound good. I’d identified some similar but I’ll go with the 75mm recommendation. I intend to try six each side.
Thanks for taking the time to help.
Regards
Tony
Hi Tony,
Two of my friends have built run off rooof observatories and they are happy with the outcomes. Here are some details of the rollers and rails they used.
http://www.rollingcenter.co.uk/
The rail for these wheels are the “Angula Z3”. They come in 3 metre length
The wheels were £4.44 each – I got 6
the rails cost £22.64 for a 3metre lengtH
The ‘V’ groove wheels & rails are superb – it really is possible to push it with one finger.Denis Buczynski
Denis,
that’s a useful link. I’m in the process of building a 4.2m x 3.6m roll of roof so getting suitable wheels and track will be necessary.
Accessories to large gates seem to be one way to go. Besides wheels and track electric gates also supply electric motors and teethed track that allow electrification. Some builders have also used up and over garage doors electric motors and track.
Those wishing track angled or otherwise may like to consider metal stockbrokers. They have very long lengths and various shapes and sizes cut to length and deliver. They are much cheaper that off the shelf DIY
Regards
Eric
Many thanks. Had considered toothed track, etc but had fallen at the first hurdle with regards availability.
Regards
Tony
Hi Tony,
one (of the many) mistakes I made when constructing my roll-off roof observatory I embedded the exteriors supports for the exterior rails (where the roof rides over onto when open) within the building, so when the eventually rotted, it was a particularly difficult job to replace them.
So, I’d suggest thinking about how you might replace them when that needs to be done. Unlike the main building the exterior rails will be subject to all the weather…
Look forward to hearing how the project goes.
Clear skies
Callum
I’d thought about ’embedded’ rails to ensure they’re in line and make the opening/closing as smooth as poss.
Have to rethink.
Regards
T
Hi Dennis,
just following up on your recommendation on wheels and track.
I’ve looked at the site the wheels come in three sizes and at the price you quote I would think these are the 50mm diameter V wheels. The other diameters being 60mm and 78 mm se
My Observatory is 3.6 x 4.2 m. with a Pent roof which is felted. Based on your experience which sized wheel would you recommend.
The track you mentioned has a round rather than inverted V guide. Does this except the V groove wheels.
Many thanks,
Eric
Hi Tony,
I used a design similar to that Stewart recommended. My roll-off observatory is 8’x10’. Due to rules stipulated by a higher power that you met at the BAA meeting, I had to split the roof into two halves each moving off in opposite directions. I purchases (2) 20’ pieces of angle iron. I was able to arrange free delivery as I was nearby to where they were making another delivery. Of course a bicycle could be a funny option depending on how far you would have to go:) I went with (8) 4” cast iron v-groove wheels with ball bearings. I cleaned up the angle iron and applied two coats of a Derusto brand paint. It is wearing off a bit but no problem so far after 3 years. I might reapply at some point with a brush. The wheels are rated at 800 pounds each. One wheel has a bit of rust but cosmetic only. I put a wood block at each track end as a stopper. I used some stainless steel cap screws every couple of feet to hold the rails in place on treated 4”x4” wood support beams, which on the outrigger ends are supported by treated 4”x4” treated posts set on concrete blocks with adjustable steel screw brackets. Of course as you know I live in the desert and you might encounter a wee bit more moisture. Each roof section rolls very easily.
Cheers!
Woody
I’m not surprised the roll-off design is so popular. Incredibly adaptable.
So far my “many small wheels” design has held up although I’ll probably go with larger wheels as you suggest when a refit becomes necessary.
The lightweight covering has held up after a dozen storms and it’s still completely dry. I think I’ll put another layer over the top before winter just in case. An entire covering only weights a couple of pounds.
The only issue has been with a slight sag of an inch or so, in the actual roof front due to the natural ‘give’ in the timber. Once the roof rolls off there’s minimal support at that point. I have a 2.5m 2″ x 2″ angle iron lintel which should cure it buts its minor.
Regards
T
Because of myself being a sheet metal worker I set about building my own roll off roof observatory from metal. Lack of space for the roll off caused me to make the roof in two halves. The outer half rolls onto the lower half and they both roll away. I felt that using castors, for example, on both halves would produce excessive gaps. So to keep the roof sections as low profile as possible I made two channels from 2mm thick galvanised steel, the sides about 12mm high and the inside width about 25mm. I then made eight blocks of metal that would run in the channel. They were drilled with a hole which would accept a steel ball bearing. The blocks were fixed to the corners of each roof. So basically the roof runs on captured steel ball bearings which produces minimal gap. Because the roof is an apex style and I have two runners on each side it can bind a little bit but a touch of grease can help. So far it has served me for many years without trouble. The channel shows little sign of wear but I recently changed the ball bearings which helped it run smoother.
Do you mean the weight of the roof? If so, the two halves are not too heavy, they are constructed from folded angle iron and covered with thin plastic coated steel cladding sheet. When we moved into our house there was a ready made concrete base. The previous owner took the original shed with him. So I basically started building a new shed entirely out of metal.
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