New Forest Obsy

[rfdesigner]

We bought the house.. we moved in and now an obsy is to be built, a couple of hundred yards north of the New Forest, great position.

so, Step 1, the pier.

First: scope + mount + counterweights = 10stone (~60kg)

Reading around it seems a round 12" or so steel pipe is something close to the way to go. I want this as high as I'm allowed, which means something around 6.5 feet from ground level to the base of the mount, I'll still get a ROR over this within the 4m ridge, 2.5m eves I'm allowed under the planning rules.

I'm planning to concrete the base of the tube directly into the ground, for the top end I'll need some kind of plate welded on, but I have one design problem.

Azimuth alignment.

The mount has no azimuth alignment built in, it expects one to place it correctly in the first place (fullerscope Mk IV.. old, very old)

I'm thinking of slotted holes in the top plate of the pier, but the mounting holes are on a diameter slightly less than 12", so how to fix to a nut/bolt that is inaccesiable from underneath... the more I think about this the more I'm thinking I need a smaller diameter pipe, but I know then it will sway.

So, any ideas?

thanks

Derek

[Photosbykev]

Weld a short thick section pipe with a flange on the top to the top of your pipe. If the short pipe diameter was around 8" but only 2" long you could get to the bolts/nuts set on the right PCD under the flange. You would also be able to add leveling screws if needed. Being very short I wouldn't expect to have any rigidity problems with the reduced diameter over a short distance.

[rfdesigner]

Of course.. yes that's the way to go (or something very similar).

thanks..

next: some proper drawings then off to find someone who can fabricate it.

Derek

[laser_jock99]

so how to fix to a nut/bolt that is inaccesiable from underneath... the more I think about this the more I'm thinking I need a smaller diameter pipe, but I know then it will sway.

So, any ideas?

thanks

Derek

'Owl holes' - holes drilled in steel tube, just big enough to get your hand/spanner in. And also very handy to run cables down the pier. I have two owl holes at the top & one at the bottom for the cable run.

You could make your azimuth adjustment by making a 'puck' that drops in the steel tube, locked off with a bolt through the tube. I managed to polar align on the puck rotation alone. Contary to popular belief no 'leveling' adjustment is necessary on permanent mounts- just good polar alignment.

[AstroMadBloke]

I'm using a brake disc in my design to allow for leveling and will be welding a small lug on for the azimuth adjuster. The Fochabers Observatory

[rfdesigner]

Great, thanks for the puck idea, mulling over drawings next.

I've been diverted by other issues this evening.. such as CS30/31 courses for the chainsaw I'll be needing. Felled one tree last weekend with an experienced neighbour and I'm hooked.

Getting the pier made while I'm learning how to wield a 'wand of doom' seems the way to go.

One bit of excitement.

The land where the obsy will go has some old low brick walls which I've been bashing away at today. Sadly the motar is stronger than the bricks so none of it will be reusable. However on knocking one brick off we found not only a really huge centipede hiding beneath, but also a newt, my daughter was fascinated.

Derek

[laser_jock99]

The land where the obsy will go has some old low brick walls which I've been bashing away at today. Sadly the motar is stronger than the bricks so none of it will be reusable.

Derek

Ideal hardcore for the obsy concrete base!

[earth titan]

found not only a really huge centipede hiding beneath, but also a newt

Derek

Hide it quick. If the tree huggers find you have newts, you could be in a long wait..... specially if its one of those crested critters....

You could always claim you meant an 8" newt......

[yesyes]

I was going to ask what aperture and focal length the newt had...

[rfdesigner]

It's all right folks.. I went and checked, it was just too small and plain to fit in with the endangered lists I could find online.

Looks like a common little so and so.

Derek

[yesyes]

It's all right folks.. I went and checked, it was just too small and plain ....

Might be able to use it as a guide scope then ..

[rfdesigner]

Contemplating the building... Ideally I'd like to roll a double pitched roof off over a double pitched roof warm room come shed (the shed part gets it past my better half.. and we do need it anyway)

I'm anticipating a decent pitch to the roof, maybe 30degrees or more. Clearly the weak point is going to be at the ridge, as without eves level bracing it's going to be weak.

I'm wondering if I might do better rolling the warmroom/shed roof at the same time as the obsy.

I've also realised that keeping the weight of the rolling roof down will keep costs down as everything else needs to be built to cope with the roof.. less roof means less supporting struts, foundations & digging.

(reason for wanting to do this: reduces south view blockage, and keeps a pretty single roof structure, rather than a less pretty two hight/type roof)

Derek

[yesyes]

It might be easier / more stable if the scope room roof is an apex roof that rolls over a flat (at a slight angle) warm room roof. Similar to Gina's and Malc-c's builds.

[rfdesigner]

Well it's been rather a long time, but now the trees are down, most of the wood cleared away and I've got a good load of rubble for foundations.

One question I have outstanding is regarding the rails for the roll off roof.

I'm planning on using oak posts for the main corners to maximise lifetime, but I can't use them for the head height rail suports due to potential warping, What do others use for the rail supports?.. and what problems / solutions have you found?

Derek

[Gina]

My rails are 4 metre 75x47mm timber supported by same size timber framework..

[laser_jock99]

What do others use for the rail supports?.. and what problems / solutions have you found?

Derek

I used pressure treated 4"x4" pine for the entire frame. Doesn't seem to have warped or twisted- but then once it's built into a structure it's kind of self supporting. Make sure you give all your timbers a double dose of creosote- once clad over you won't be able to treat them again easily.

[rfdesigner]

I used pressure treated 4"x4" pine for the entire frame. Doesn't seem to have warped or twisted- but then once it's built into a structure it's kind of self supporting. Make sure you give all your timbers a double dose of creosote- once clad over you won't be able to treat them again easily.

Thanks Laser_Jock and Gina.

The photo looks similar to what I have in mind for my structure.. except I'm thinking of using oak for longevity. I can get 4x4 oak fence posts for about £10 a pop, so for about £300 I get myself a very basic oak frame, it's just warping that worries me.

I'm looking at a brick wall to a damp proof course, then the frame on top of that, that way the whole wood structure is kept clear of the ground thus minimising damp, following building regs for the wall height etc., pine cross members and shiplap to then fill in the sides,

Derek

[laser_jock99]

Depends how well seasoned the oak is I guess. If it's sold as 'green oak' then it still has a good while to before it settles down. I made a fireplace surround from 8"x6" grean oak beams.

I let them season inside the house for a year before final shaping and fitting. They have distorted slightly- so maybe get the most seasoned posts you can find.