Astrokev

Neat idea. It will transform your life! And ain't Sketchup great?

Yep, Sketchup is wonderful to help visualise ideas. I still need to get my head around animations though!

Seriously - they're fine.

Looking great Malcolm. Like the green, the same colour as my old DIY scope tubes! To be picky though, the walls do clash a bit with the floor; "blue and green should never be seen....", but I suppose your not planning on wearing it, so let's not quibble, eh! ;-)

Coming along nicely Malcolm I shan't be painting mine black either. Light green sounds nice.

Pleased to hear it Gina, though you probably don't need to decide the final colour just yet!

LOL - now there's a thought... we have some deep lilac left over from when we decorated the girls room

Well there you go! All in perfect harmony. Sorted!

Ta for the scroll bars, I'll have another butchers.

Hi Kevin,

I'm off to wickes tomorrow to get some paint... I know that most people pain their rooms black, but I want something a bit lighter, probably a pale green or something similar

Sounds like great progress. It'll be a shame when the project ends in a way, as it's been great watching it evolve.

re: Paint colour. I remember seeing Paul-C's obsy (the thread seems to have vanished these days) but that was painted in a mid-blue. That looked really cool. I hate black as an obsy colour so pleased you're not choosing that.

You could always try Purple, to match the mount!

Hi Kevin,

I'll take a look at the site to see why there is no scroll bar. What screen res are you running at??

1366 x 768 (on my lappy. Haven't tried it on my big monitor desktop).

Just had a peek at your hobby website Malc. 3 points -

1. The menus at the sides go below my screen and I don't seem able to navigate to them. Probably something up with my set-up?

2. Very impressed with the quality of the 1/12 scale houses. They could benefit from a 1/12 scale observatory to compliment them though !

3. How the heck d'you cram everything in to a normal 24/7 week ? !!

It's the heavy rain that's stopping me - apart from lack of funds. My site is waterlogged I might have to provide ground drainage.

You should move to Bedfordshire. We're suffering a drought over here but, sadly, enjoying lots of cloud to go with it. Saying that, it's sunny at the moment....but then the sun hasn't set yet!

Fantastic build so far Malcolm. Really looking forward to seeing how you fit-out the interior. I'm filled with a mix of high admiration and envy!

I think it's very clever to run the roof along the top of the fold-down side. Usually there's a fixed running rail to take the roof that would get in the way of viewing. This has got me thinking

Oh dear, I can see another re-design coming along!

Excellent Malcolm. I'm very impressed!

Great pictures but is it possible to also show a few pics of the join/seal between obsy and warm room please? I can't quite make out how you've done this. Thanks.

Looking forward to the next stage and internal fit-out.

Nice job Shane. Well done.

I've just got back from the woodyard and tried marking the sides up like they said and while I admit I might be doing it wrong I can't see how the teflon would be at a right angle to the bearing if the v isn't 90 degrees. I asked my Dad how he'd do it too, he designs jet engines for Rolls Royce so I think he knows a thing or two about bearings, weight distribution etc., and he said the best way to do it would be to make the cut out 90 degrees. He also thinks a V would be better than a circle because it's only got 2 very slim points of contact and they'd be much bigger, in comparison, if you used a circle.

TBH I've not decided whether to make the cut out circular or a v shape yet so I'm going to do both and see which one I like best. I was going to try building it today but, typically, it's started to rain here.

For a V cut-out, the cut-out forms a tangent at the point of contact with the bearing. Therefore, if you want the teflon pads to be spaced at an angle of 90' on the bearing, the cut-out logically needs to be cut at 90' also. It's basic trigonometry if you think about it. Think of it as a quadrilateral, with the points of contact always being at 90' (tangents). The V angle and the angle between the pads as measured from the centre of the alt axis must always add up to 180'.

As Shane previously suggested, if you want the pads to be at 70', then the V cut out needs to be at 110'.

(2 x 90' + 70' + 110' = 360').

Again, whether you choose a V or a circle cut-out doesn't make any difference regarding the amount of support given, providing the points of contact are tangents to the bearing.

hope this makes sense.

Hope you can see what you're doing under there. Looking great!

this is certainly possible. I think it's due to the relationship between the depth of your curve and the diameter of the bearing. according to Kriege and Berry the optimum spread is 65-70 degrees although this assumes a shallow section of the curve.

In my view, the decision on where to place the teflon supports is independant of the curve depth and diameter of bearing. I think it's angular position that is important. The decision is, I believe, driven by the following considerations -

1. the material used to make the bearings and the structural integrity of the circularity (ie. is the bearing a solid circular piece, or a hollow ring such as a section of pipe or similar). A ring would be more prone to deformation (ie. losing its circularity) than a solid piece.

2. the weight of the OTA being supported. Heavier = more likelihood of deforming the bearing, depending on the answer to point 1 above.

I guess the overall aim is to use contact points that provide the lowest pressure at the point of contact, without deforming the bearing. The position obviously needs to be wide enough so that the OTA doesn't "roll off" the supports when the altitude is adjusted.

For my next 6" Dob (currently being planned) I was intending using 110mm drain pipe end caps for the bearings (larger ones are available on-line so may consider these instead). Couple of quid each and would not require any fabrication on my part.

Mmm, interesting idea using a drill as a lathe. A couple of points spring to mind though -

1. Challange #1. Make sure the drill is well fixed to prevent any movement during working on the piece.

2. If the diameter of the piece being lathed is large, this is likely to put a huge strain on the drill motor at start-up due to the large inertia. (the drill is designed to turn relatively small diameter tools with low inertia).

3. Getting the piece to be completely square wrt the drill axis of rotation is difficult, and becomes more so as diameter increases.

Not saying it's impossible, but I once tried to lathe circular plastic sheet material using a drill and all the above created challenges/difficulties.

Oh, and wear goggles !! I recall an incident at school woodwork class once where a schoolmate failed to attach the cherished wooden bowl he was making onto the lathe correctly. Next thing, the bowl was through the window and ended up 20 yards across the field. Not pretty.

Shane

An interesting design point you mention above regarding the circular cut-outs on the rocker box.

Since the alt bearings only touch the rocker box teflon pads at 2 points, is there any reason why the cut-outs couldn't be simple right-angled "V" cut-outs. Although circular cut-outs do look more pleasing to the eye, from a functional viewpoint I guess they don't have to be. The teflon pads would need to be placed at the points of contact (which with a right-angled "V" would be 90' apart). Does this make sense and would you agree?

Years ago, I made a dob in this way, and it worked fine.

I've not searched yet, so may be readily available, but where did you get your teflon?

Sorry to hear about the redundancy Shane. I have been out of work for a while now but like you my wife has a good job with a good company so in the end we decided it would be best if I looked after the kids. I won't lie I'd much rather be back in work, for one it would be easier than having to look after two energetic children all day . I'm sure you and Kevin will find some thing soon.

Cheers Spaceboy. Much appreciated. Meanwhile, I continue to plan, draw ideas, research, plan, dream.....

same here mate so thanks for the tip! and here it is - 12" version of 'Good Life' by Inner City - not seen the light of day for about 20 years!

Excellent choice!

quite positive and actively applying for jobs etc - want a new career so in seek and justify all my skills mode currently. got a decent package though so have some time and it may even work out well. my wife has a good job too and I think will be the main breadwinner for a long time to come!

you're a genius mate with the LP. I do actually have some still in the loft so bonus!!

this will enable me to get it finished while Russ and I work on a joint purchase of some laminate/formica.

Good luck with the career change! I'm in the same boat, actively applying for new "opportunities" and hoping for the best. Living off my package so don't really want to blow any of it on the long list of projects I've got lined up....just in case! Well, not yet anyway!

(redundancy has it's benefits sometimes.....).

That's you and me both, mate!

Regarding the formica for the base, I've read of someone who used an old vinyl LP. Worth considering if you have any old disks lying around. Certainly cheaper than buying formica.....

.....and if you stick a needle in the rocker box, you could listen to some music at the same time!

Be sure to post lots of pics. I may copy your design and methods!

I was just going to ask - what have you used for the azimuth bearing? It's a while since I made a dob, but is still "traditional" to use formica and teflon pads, or is that old school nowadays?