Designing and 3D printing a horseshoe mount for my turret tripple widefield imaging rig.

[Gina]

I'm looking to make a 3D printed mount for my turret imaging rig.  This would be much easier if the turret were modified to use a different mounting.

Edited October 26, 2021 by Gina

[Gina]

This is the turret imaging rig with 200mm lenses mounted on my EQ8.  The mounting method here would be totally unsuitable for a lightweight and compact DIY mount.  I'm thinking of a "horseshoe" type mount.

 

This is a CAD screenshot of the bones of the current mounting system, designed to use a standard ADM dovetail bar.

 

This is it without the mounting.

Edited October 28, 2021 by Gina

[Gina]

After much thought and playing around in CAD, I came to this arrangement as the simplest implementation.

 

Applying mathematics or physics to the situation, any object in space has 6 parameters or co-ordinates.  3 spacial axes and 3 rotational co-ordinates.  The central bearing takes care of the X, Y, Z co-ordinates.  The rollers cover 2 of the 3 rotational values and the final one is the turret rotation about its axis which will be controlled by gearing and stepper motor.

 

Rotation drive could be either the same as now with a large spur gear ring attached to the back plate or maybe turn the front plate and wheels into gears.

Edited October 28, 2021 by Gina

[Gina]

3 rollers restraining the front turret plate.

 

Wheels attached to a ring.

 

Then this ring could be connected to the axle tube to form a complete assembly.

 

 

The colours are to make the model clear only - won't be printing in those colours.

 

ATM I'm just playing with the principles, probably need some adjusting and additions.

Edited October 28, 2021 by Gina

[Gina]

DEC worm gear added.  Looks a bit on the small side (about 200mm) but we'll see how it goes in the horseshoe mount.

 

 

[Gina]

Now looking at the "horseshoe".

[Gina]

Next was trying to arrange spokes to connect the horseshoe to a bottom bearing without interference with the DEC worm wheel.  It needed a considerable modification to the horseshoe design.

 

 

 

 

Edited October 28, 2021 by Gina

[Gina]

Reworked the horseshoe a bit to make the spokes easier to design.  Holes for attaching the spokes at sensible distances from the centre point of the outer arc and also set at 120 degrees to each other so the spokes could meet neatly where the bottom bearing mounting plate will be attached.

 

 

 

 

[Gina]

I've created a new assembly with the horseshoe RA section of the mount separated from the DEC etc. to show that part more clearly.

 

Bottom bearing arrangement consists of a 10mm OD SS rod that will be attached to a swivel bracket for PA Altitude.  Or it might be a bolt and nut.  Shown above is ball bearing and bearing plate attached to spokes with bolts.

 

 

 

[Gina]

To get an idea of scale, the diameter of the outer running surface of the horseshoe is 400mm.  The thickness of the horseshoe is 30mm.  It's a fairly substantial structure.

[Gina]

Was having problems with the CAD and decided to start again with the RA assembly and carefully check things as I went along.  I was also getting conflicts between parts so went for a redesign of the horseshoe and spokes to make sure of clearance for the DEC worm wheel and the DEC arc.  I'll just post the result and not all the "blind alleys".

 

 

[Gina]

A few more screenshots of the CAD assembly.

 

 

[MarkAR]

Looks good. Horse shoe is a great design.

[Gina]

The design so far has one serious deficiency!  Communications and power cables.  Even if I could arrange all the electronics on the turret and use WiFi there is still the need for power.  So arrangements have to be made for cables to connect from the outside world to the turret.

 

 

[Gina]

The design needs modifying to include a path for cables via the rotation axes viz. turret, DEC and RA.

 

This shows a new design of the horseshoe to provide a gap between that and the DEC arc  where cables might pass.

 

 

 

Now if the smaller hole in the horseshoe is changed to a larger one with a slimline ball bearing the cables have a possible path.

 

The "axle" can be printed as part of the DEC arc.