DIY 3D printed "horseshoe" style mount for my Turret Triple Imaging Rig.

[Gina]

Following on from the thread about my Turret Triple Imaging Rig, I'm designing a 3D printed "horseshoe" style mount for it that I can take to star parties.  Hopefully, lighter and more compact than the NEQ6 Pro mount that would be the alternative.

[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.

Though this shows the 200mm lenses, I have sets of shorter focal length lenses giving a wider FoV.  Shorter FL lenses would probably be more suitable for use with a 3D printed mount.

This is a CAD model of the rig with 28mm lenses showing the current mounting for use with standard GEM EQ mounts.

Removing the mounting parts gives this.

Ignoring the turret rotation drive and after much thought and playing around in CAD, I came to this arrangement as the simplest implementation for holding the turret.

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.

[Gina]

The rollers can be attached to a ring and that attached to the back bearing with an arc providing the DEC system.

The following CAD assembly screenshots show how the DEC system is built up, complete with worm gear to drive it.  The large white spur gear turns the turret.  The DEC worm wheel is shown in yellow.

 

Edited October 31, 2021 by Gina

[andrew s]

Nice project @Gina I was getting a  bit confused before your last post on how it would work.

Regards Andrew 

Edited October 31, 2021 by andrew s

[Gina]

I should point out that, unlike some of my earlier project threads, I am skipping many "blind alleys".  This is still a Work-in-Progress ATM though.

Next is the RA system for which I'm using a "horseshoe" for compactness.  Like other horseshoe mount designs, this will have a rear gearing and front rollers.

OK so this is how the horseshoe progressed. Starting with the basic shape.

Edited October 31, 2021 by Gina

[Gina]

The "spokes" that connect the horseshoe to the bottom bearing have to be designed so that they miss the worm wheel and don't collide with the DEC arc or anything else.

After a lot of messing about and trial and error, I came up with this.  The turret and several other parts have been hidden for clarity.

Edited October 31, 2021 by Gina

[Swoop1]

Trying to get my head around the spatial coordination of all the bits make my brane hurt!

[rwillett]

Looks good, but I'd worry about flex when you get to something that sort of size.

I'm trying to work out (in what passes for my brain these days), where the max load will be and in which direction. That's my biggest worry in printing anything to do with AP.

I don't know enough about 3d modelling to work out how to do stress calculations or even if my free version of Fusion 360 can even do it.

It does remind me of the Astrotracker that somebody modelled a few months ago.

It looks like it's a hell of a size as well, whats the max dimensions?

Rob

[Stu]

Very interesting project @Gina, looking forward to seeing how it progresses.

I must confess I thought it was a design for a three engined rocket when I first saw it and got quite excited 😆

[happy-kat]

Love seeing the design work drawings even before the printed results, good luck with the build.

[Gina]

On 31/10/2021 at 16:18, rwillett said:

Looks good, but I'd worry about flex when you get to something that sort of size.

I'm trying to work out (in what passes for my brain these days), where the max load will be and in which direction. That's my biggest worry in printing anything to do with AP.

I don't know enough about 3d modelling to work out how to do stress calculations or even if my free version of Fusion 360 can even do it.

It does remind me of the Astrotracker that somebody modelled a few months ago.

It looks like it's a hell of a size as well, whats the max dimensions?

Rob

Looks like being around 400mm - 500mm in all 3 dimensions, but I haven't finished yet, there's still the PA adjustments to add.  That might add a bit to the height.

[Dr_Ju_ju]

Something that big, and depending how many parts it 'breaks' into for printing, I'd personally printing in ABS for the stability & resilience. 

Granted the stuff needs special handling, especially with the higher temperatures needed, and the sometimes reported odour given off, but I've not noticed any & I'm currently printing the parts for a Voron 2.4 upgrade to my core-xy printer....  

[Gina]

I no longer use ABS and mainly use PLA.  Easier to print with and more environmentally friendly.  I used enclosed cabinets with fume exhaustion when I was using ABS - nasty stuff.   I used to think ABS was better but I am having good results with PLA.  When I need a higher temperature product I use PETG.

Edited November 8, 2021 by Gina

[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.

I've been investigating the possibility of running 3 instances of indiserver and the drivers on one RPi 4B and I think this may be possible.  I had thought of Astroberry Server but can't see how ATM.  Currently using a single instance for the ASI 294MM camera plus guider etc.

[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.