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Gina's Mini Widefield Imaging Observatory

Gina

By Gina
in DIY Observatories

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Tinker1947

Tinker1947

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Have you got the right link there?  That takes me to a circular saw for £217 :grin:

Its the right link due to that Skillsaw being discontinued it gets the manufactures price not the discount which brought it down to £69.99 in Dec 2013.....

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Gina

Gina

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Been looking into the motor drive for the roof.

A number of things come to mind :-

  1. Bicycle chain and sprockets.
  2. Timing belt and pulleys.
  3. Large V pulley with cord attached and wrapped round a drum on the motor

The angle of rotation for the roof drive is about 180 degrees.  So the large pulley for use with timing belt or cord could have the belt or cord attached at one point and wouldn't need teeth.

Then there's the choice of motor.  I don't think a stepper motor would be powerful enough so I'm going for a 12v DC motor with reduction gearbox.

I don't know yet whether the roof structure will prove stiff enough to just drive one end.  I might have to drive both ends synchronously.  I won't know until I've built it.

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Gina

Gina

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Calculations...  Suppose the roof takes 10s to open or close, that's 180 degrees in 10s = 3 RPM.  Motor o/p shaft is 15RPM so 5:1 reduction required.  OR if roof open/close is 20s reduction ratio is 10:1.  That would still be satisfactory I think.  Motor torque is 250N.cm equivalent to IKg weight at 25mm and with 5:1 reduction gives about 4Kg @ 300mm.  By my calculations the roof weight will be well under that.

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Gina

Gina

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The 1/2" cutter has arrived so I can set about sorting out getting ready for routing.  Not feeling up to much ATM though so I'll be taking it easy may not be routing today unless I feel better later.  This sort of thing needs a lot of care - power tools are dangerous so I'm erring on the safe side.

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Davey-T

Davey-T

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I don't have yet, and don't plan on getting any,,,touches a  piece of wood.... :)

That's because you're in that nice cosy workshop, knocking stuff up on site is not ideal, when I started it was all done by hand, not a power tool in sight let alone battery powered :eek:  kids today aye don't know they're born. :grin:

Dave

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Tinker1947

Tinker1947

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That's because you're in that nice cosy workshop, knocking stuff up on site is not ideal, when I started it was all done by hand, not a power tool in sight let alone battery powered :eek:  kids today aye don't know they're born. :grin:

Dave

If it doesn't have a plug on it i don't touch it... :grin:  :grin:  :grin:

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Gina

Gina

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Done my first trim with the router - makes a pretty nice job even on end grain.  Did it in three cuts, roughly thirds. 

A few comments on the router :-

  1. Found the fence needed to be quite thin to clear the dust extractor so had to add a piece of 6mm plywood under the 95mm x 20mm piece of wood I was using, clamped to the table.
  2. Found fitting the cutter in the collet and tightening up was awkward - difficult to hold the button in and tighten the collet with the spanner supplied.  A two spanner system would have been much better.
  3. The dust extractor is very inefficient - a lot of dust comes out the front all over everywhere :(  I put my Henry on boost but still got dust everywhere.  I'll look at adding a printed plastic extra cover because this just isn't good enough :(

Plus points :-

  1. Comfortable to hold
  2. Lightweight
  3. Decent edge on the plywood
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Gina

Gina

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Two quadrant pieces done :)  Some more bits arrived today, the other two aluminium sheets (0.5mm thick) which I think will be alright, and the polyether foam though they sent 1/2" thick rather than 1/4" so I need to separate the layers more.  Fortunately, this was before I cut the plywood so I was able to modify the design.  The 12v DC motor came today too :)  In sorting out the roof ends, I decided to up the boss area from 80mm diameter to 120mm.

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Gina

Gina

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Funny you should say that :D  I've just taken one...  and I'll take some more :)

Routing a pair of quadrants using the supplied trammel and centre point.

post-13131-0-72070900-1421182861_thumb.j

post-13131-0-67271100-1421183689_thumb.j

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