DIY backyard obs

[Benklerk]

Hi all

I'm in the design stages for my backyard obs.

I'm going to go with a timber shed with a colour bond roof. It will be 3m x 3m internally.

I have attached a diagram which is almost finished of my shed and the diagram of my mount.

The idea is to have the pier 700mm high off the floor and with a wall height at 1.6m and peak inside roof height at either 2m or 2.2m.

At this stage I'm still deciding on going with a automated roof or push the roof, it has to move a 3mx3m timber roof. For the wheels would ball bearings be better and what sizes should I be looking at?

Does anyone of any ideas what to go with? I would like to keep the motor inside if possible. The motor doesn't need computer control, I'm happy to push a button to open the roof.

 

Ben

[Miguel1983]

Hi,

i've used these wheels, and i'm quite happy with them, the roof is 2,5 by 2,5m and i'm sliding it open with one hand.

you can check out more pictures in my building topic : 

 

[JamesF]

They're very similar to the wheels I used, though mine are V-groove rather than round in section.  They're 80mm diameter as far as I recall.  My roof is a pitched roof about 2.5m by 3.6m with sides around 600mm high and weighing somewhere around 150kg, perhaps a little more.  Four wheels are sufficient for me to be able to open and close it one-handed.

This is how the main structure looks:

And in it's "getting towards finished" state:

My original thoughts on automating the roof were to have a motor driving a "drum" fixed in the centre of the internal wall with a cable running around the drum, each end of the cable being fixed to one end of the roof.  Turning the drum would then pull on one end whilst paying out the cable to the other, if that makes sense.

However, our builder has delivered me two gear racks from some stair lifts he removed from a house he was working on, together with the motor units and pinion gears for each, so I may now fix the rack to the roof and use those.  Or I might just use one of the motors from the stair lift and go with my original plan.  In either case it means the motor can stay inside the observatory.

James

Edited June 6, 2019 by JamesF

[JamesF]

Oh, I should have added...

The wheels and rails came from FH Brundle, a UK supplier of fittings for electric gates.  They seem to be quite popular as a source for such things here.  I assume there will be similar vendors in Australia.  Checking through my emails, these were the wheels I used:

https://www.fhbrundle.co.uk/products/0586604000__80mm_Dia_V_Groove_Wheel_One_Ball_Bearing_Internal_Support

James

[Benklerk]

Thanks for the responses.

Spent the last few days going though tons of website. Looks like V groove tracks is the why to go. I can get 75mm, 100mm or 150mm wheel size. How much of a difference would there be in ball bearing wheels compared to plain ones? 

https://www.richmondau.com/wp-content/uploads/2017/05/Track-Wheels-V-Groove.pdf?fbclid=IwAR2DuIo9luUpH32faTf5W9cDmrhruL2_fQ_3pTYvpWD6Pm7pV1nv6GQcbGI

[JamesF]

In real terms (ie pushing the roof back and forth) I'm not sure what difference the bearing type makes.  I'd assume a plain bearing would have more friction, but whether it would be sufficient to be noticeable I have no idea.

James

[Gina]

I think it would make a lot of difference.

[Bukko]

If you consider the total cost of the build project, would the cost difference between the plain and roller type of bearing be noticable?

Gordon.

[JamesF]

1 hour ago, Bukko said:

If you consider the total cost of the build project, would the cost difference between the plain and roller type of bearing be noticable?

Gordon.

A good point

James

[saac]

Ben, roller bearings are generally specified when the load on the bearing surface would be excessive for ball bearings; most standard applications will use ball bearings.  Our obsy roofs, while they may appear heavy to us, are generally well below any design consideration for bearing specification.  While either roller, or ball bearing would work well for your design you may experience a little addition rolling resistance with roller bearings, whether you would actually notice it is mute.  As for load capacity, remember that your car wheels, each typically supporting anything from 250 - 500 kg plus dynamic loading cope admirably using ball bearings.  I personally would go with the ball bearing wheel assuming cost and availability is not an issue.   Good luck with your build, a permanent observatory makes such a difference.  

Jim