Advice on choosing the right mounting plate for a distribution box

[Vox45]

Hi all,

I've made several iteration of a power distribution box/hub attached to the side of my SW80Ed like this

 

It has worked fine for long time but now I would like to refine the design and add a couple of items to it.

-> make it smaller and slimmer

-> add an arduino nano board and electronics to operate a "myfocuserPro" focuser control

-> add a RPI4 inside the box (instead of a RP3B+ that hangs outside the box)

-> mount it on the top of my scope so it is easier to balance, is more rigid and has less wind drag (if there is a lot of wind, my current box act as a sail ...)

I see that prima luce Eagle boxes are mounted on top of refractors like this:

 

 That is the basic idea of what I want to build but what kind of plate should I use to mount the box on top of my refractor ? A custome made aluminium plate maybe ? Or do I need to change the holding brackets like they seem to have done in the example above ?

Please let me know if any of you guys or gals have an idea on how to solve this  

[JamesF]

I've been pondering on this myself recently.  I have thought about having something (flat plate, or L-section plate) fixed between the rings and dovetail, but I've come to no conclusions as yet.

James

[michael8554]

If you're going to mount your guidescope on top like the Primaluce then as rigid as possible - don't use the wobbly adjustable rings that they unbelievably use.

If not then nothing special because a few microns of flex won't matter.

Maybe onto the still camera mounting positions on your rings ?

Michael

[Vox45]

43 minutes ago, michael8554 said:

If you're going to mount your guidescope on top like the Primaluce then as rigid as possible - don't use the wobbly adjustable rings that they unbelievably use.

If not then nothing special because a few microns of flex won't matter.

Maybe onto the still camera mounting positions on your rings ?

Michael

No as I will be using an OAG. I would just like to mount the box which will be 3D printed. I guess I could just make holes in the box and secure it to the 2 screws on the scope rings but that would make the box a bit wobbly, I'd rather bolt the box to an aluminium plate and the plate to the rings... A custom made plate then ?

[JamesF]

I assume it won't be too different in France, but as I mentioned earlier I have considered a custom made plate, where "custom made" means buying a piece of aluminium plate off ebay and drilling it to fit over the bolts between the scope rings and the dovetail (sandwiching it between the two).  The plate could then have additional holes drilled to allow kit to be screwed/bolted on.  It would probably act as a nice solid anchor point for cabling too, come to think of it.

James

[Vox45]

I think that changing the rings to ones with a flat surface would do the trick, I could then just bolt the bottom of the box to the ring with 4 anchor points... no need for a plate of any kind then .. It is hard to tell from the picture if the knobs are higher than the top of the ring though... If so, that would mean that I would need some kind of spacer to elevate the box ... introducing potential flexure 😕

https://www.firstlightoptics.com/tube-rings/william-optics-90mm-cnc-tube-rings.html

 

 

 

Edited October 8, 2019 by Vox45

[JamesF]

4 minutes ago, Vox45 said:

I think that changing the rings to ones with a flat surface would do the trick, I could then just bolt the bottom of the box to the ring with 4 anchor points... no need for a plate of any kind then .. 

https://www.firstlightoptics.com/tube-rings/william-optics-90mm-cnc-tube-rings.html

At that price I'd definitely buy the plate and drill it myself :D

James

[Vox45]

10 minutes ago, JamesF said:

At that price I'd definitely buy the plate and drill it myself

James

spoken like a true DIYer   I just don't see how to fit a plate on those round rings that came with my OTA, I think it would be a bit wobbly

[michael8554]

Large diameter washers inside a stiff plastic box should be good enough to prevent it wobbling. 

Or contact adhesive thin ally sheet to the inside. 

Michael

[JAS]

You could 3D print two spacers that are the same width as your rings, both with a flat top to mount your box to and with a radius profile on the bottom to match the outside of the rings. Then just bolt through the box through the spacers into the top of the rings.

Jason.

[Demon Barber]

Or go oldschool and use ally bar and a file to profile as above.

Mike

[Phobos 226]

I just did something similar with my RPI4, USB hub and my in-progress power distribution box. I mounted a long (cheap) 35cm Skywatcher dovetail onto the top of my tube rings and made a platform bolted to it from rigid 5mm thick matte black Perspex which then has my bits mounted using strips of 3M Dual Lock so I can swap parts around if I need them or not/shift the balance etc. Of course you can bolt things to it as well, but it's cheap, lightweight and easy to work with.

If you wanted it more rigid then I would get some aluminium plate in place of the acrylic and bolt through as has been suggested, but with no cameras directly coupled to it I see no issues in a little flex for a distribution box on the top of the tube.

P.S The RPI4 4GB is a dream running KStars, I can run everything locally on Pi now and just remote in from my 4K TV at native resolution. Works flawlessly and I'm sure you'll be happy with it too!

[Vox45]

16 minutes ago, Phobos 226 said:

I just did something similar with my RPI4, USB hub and my in-progress power distribution box. I mounted a long (cheap) 35cm Skywatcher dovetail onto the top of my tube rings and made a platform bolted to it from rigid 5mm thick matte black Perspex which then has my bits mounted using strips of 3M Dual Lock so I can swap parts around if I need them or not/shift the balance etc. Of course you can bolt things to it as well, but it's cheap, lightweight and easy to work with.

If you wanted it more rigid then I would get some aluminium plate in place of the acrylic and bolt through as has been suggested, but with no cameras directly coupled to it I see no issues in a little flex for a distribution box on the top of the tube.

P.S The RPI4 4GB is a dream running KStars, I can run everything locally on Pi now and just remote in from my 4K TV at native resolution. Works flawlessly and I'm sure you'll be happy with it too!

Interesting, would you have any picture so I can better visualize what you did ?

I am running Indi/kstars/ekos on an RPI3B+ and I am quite happy with it. I want to go for the extra memory and CPU speed and, of course, the UBS3 ports of the RPI4  I plan to recycle the RPI3 to work with my 3D Printer using OctoPrint

[Phobos 226]

On 10/10/2019 at 01:00, Vox45 said:

Interesting, would you have any picture so I can better visualize what you did ?

Had a busy weekend, here are some quick phone images that I only just got around to! I just got my power distribution box finished and mounted this evening and you can see it underneath the RPI4. I've got the platform mounted in a 'wing' style at the moment as I moved my guidescope back a bit a more. The weight imbalance here is only about 200g which isn't too bad opposed to mounting it directly over the centre axis of the OTA.

The platform has two mounting points with 1/4 inch UNC bolts that thread directly into the 33.5cm dovetail which had those holes pre-tapped. I added my own holes to the dovetail threaded directly into my scope rings using the same UNC threaded bolts. This is on a 130PDS and the rings that came with it as standard from Skywatcher, so they may be smaller on the SW 80ED I'm not sure, but the principle remains the same.

Using an OAG you can mount the plate/platform directly over the centre of the tube so you can be a bit more flexible in your layout than me trying to get around the limited space I've got left on my setup here. Either way I'm happy with my new power box!

[JamesF]

Nicely done

Did you design and print the "string vest" case for the RPi yourself?

James

[Vox45]

Ho I see what you  mean now  thanks for the pictures

[Phobos 226]

16 hours ago, JamesF said:

Did you design and print the "string vest" case for the RPi yourself?

It was one of these by John Sinclair but I bought it direct from his eBay store as I don't have a printer myself. The 4 can get rather hot, especially with the warm nights we had over the summer in the UK South East this year.

[Vox45]

On 15/10/2019 at 17:56, Phobos 226 said:

It was one of these by John Sinclair but I bought it direct from his eBay store as I don't have a printer myself. The 4 can get rather hot, especially with the warm nights we had over the summer in the UK South East this year.

did you apply the new firmware that deals with overheating ?

https://www.techrepublic.com/article/raspberry-pi-4-running-hot-new-update-will-cool-your-board-down/

[Phobos 226]

I didn't, but I've not been running the official Raspbian release for some time as I switched to Ubuntu Mate with Stellarmate OS and then KDE with their latest update.

I never encountered any overheating or throttling problems with this case however and it stays very cool compared to running it with no fan and heatsink out on the bench/desk.

I've seen a lot of recommendations for the FLIRC case though, which has a plastic bottom shield to help out the WiFi and an all aluminium core that acts as one giant heatsink that sits directly on the chip. As it's going to be in the cool night air I imagine this would be perfectly fine as well, as we're not running them stuffed away inside some entertainment centre or under a TV etc. I'll probably switch to a FLIRC case in a little while as I do like the look of the finish and it's not too expensive.