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Roll-off observatory runners/wheels.

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Anthony Rodda's picture
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Joined: 01/09/2014 - 14:15
Roll-off observatory runners/wheels.

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

David Basey's picture
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Rails and bearings

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.

 

andrew.j.smith1905's picture
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Joined: 02/12/2016 - 12:22
Guide rail

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

Anthony Rodda's picture
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Thanks David and Andrew

Points noted. Very useful.

Regards Tony

David Arditti's picture
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Observatory designs

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.

Stewart Moore's picture
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Roll off roof

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

Anthony Rodda's picture
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David and Stewart, thank you.

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

Denis Buczynski's picture
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Joined: 05/03/2014 - 13:04
Roll off roof

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

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roll off roof

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

Anthony Rodda's picture
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Denis and Eric.

Many thanks.  Had considered toothed track, etc but had fallen at the first hurdle with regards availability.

Regards

Tony

callump's picture
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Replacing the rail supports

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

Anthony Rodda's picture
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Callum, good point.

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