All Sky Camera Revisited

[Gina]

It will need both shafts driving though, otherwise you can get this.

[Gina]

Cut the hole where the dome goes with a trepanning tool (aka tank cutter) by hand.  Too big for electric drill.  Good exercise 🤣

[Gina]

I need to make some small alterations to my designs as the box isn't as big as advertised.  It's 190mm x 140mm outside not inside.  With walls 3mm thick the inside is 184mm x 134mm.  That's the lid  - I haven't measured the bottom part.

The dome clamp ring is 150mm diameter and that was supposed to be the width of the box outside.  Now I shall have to adjust it.

Underside view of new dome clamp ring with groove for flange.

Edited September 16, 2020 by Gina

[Gina]

I've measured the bottom of the box and that is as advertised.  Fitted the dome on temporarily with the new dome ring and camera casing, with M3 bolts and nuts.

Edited September 16, 2020 by Gina

[Gina]

The design still isn't settled!  I realised that I shall want to take the dome off (or not put it on) while having all the rest assembled so that I can rough focus the lens with the motor focussing half way.  The lens focus ring is not so tight in the focus lever ring that it can't be turned by hand.  The current design has the camera housing attached to the box top by the same bolts that hold the dome clamping ring.

[Gina]

Decided to fasten the camera housing outside the dome clamp ring so the two are independent.  This is the new camera casing.  The previous one inherited so much unwanted code from previous versions that I decided to start again.  The result is a tidier looking model with strength just where needed combined with thermal insulation.

[Gina]

I can team this up with an 8 hole dome clamping ring with the ring rotated 22.5° so as not to clash with the arms of the camera casing.

 

Edited September 17, 2020 by Gina

[DaveL59]

I was tempted to suggest having extra wings on the camera housing, with threaded holes or captive nuts to allow you to secure the camera separately and allow removal of the dome but figured that'd add a complication and perhaps less secure dome clamping in terms of load on the o-ring. Looks like you figured a solution tho which should work fine 🙂 

[Gina]

I've designed and now printing a template for drilling the holes in the box top - 12 of them.  The circular part fits in the hole in the lid and the two straight bits fit the edges.

Edited September 17, 2020 by Gina

[DaveL59]

planning a production line for other members? 😉 

[Gina]

To answer you question.... no.

It's much easier to use a template for drilling holes than ultra careful marking out and very careful drilling.  Designing and printing a template is much easier and almost guarantees getting the holes in the right places.

[davefi]

5 hours ago, Gina said:

I've designed and now printing a template for drilling the holes in the box top - 12 of them.  The circular part fits in the hole in the lid and the two straight bits fit the edges.

Thats exactly the kind of thing I really want a 3D printer for! One day I might eventually find space to set one up 🙄

[Gina]

Looking again at the dome cover linkages and control.  There wasn't room for the axles in/on the lid so moved them down.  The first 3 screenshots show the operation.  The 4th shows what can happen if the axles aren't coupled.  The cover just clears the dome and with 180° rotation of the axles, nicely clears the FoV.  Next problem is driving the axles.  They need coupling so that they revolve together.  I've thought of 3 possibilities.

1. Timing belt and pulleys
2. Spur gears with pinion in between.
3. Linkage.

One needs turning from a motor, of course, and that can be the one that runs through the box, so can be driven from inside.

[Gina]

To test my theory that the two axles for the cover motion want to be coupled and keep the same relative angle, as the cover opens, I applied a constraint to the difference angle.  Then the cover wouldn't move so I removed the constraint and instead measured the angle difference as the cover was moved and found a tiny variation of <0.1° so the theory is right but the modelling is not perfectly accurate.

Edited September 19, 2020 by Gina

[Gina]

I've come to the conclusion that dual linkages are too complicated and difficult to arrange and with the change of enclosure to a rectangular box the situation has changed.  It now favours a single pair of levers to open/close the dome cover.  The box is narrower than the printed casing was and the cover levers can go outside the box.

 

Edited September 21, 2020 by Gina

[Gina]

[Gina]

[Gina]

[DaveL59]

looks good Gina, tho you'll miss views of the flies and eight-legged beasties like this 😄 

[Gina]

Haven't decided yet whether to use timing pulleys and belt or 3D printed spur gears.  ATM I think I favour timing belt.

[Gina]

With 3D printed gears.

Closed.

Open.

And the internals.

[DaveL59]

is the drive motor going to fit OK given you're planning motorised focus too?

[Gina]

Yes, a motor each side of the box near the top and attached to the lid.

[Gina]

New design.

[Gina]