Kutter binoculars 120/f31

[Chriske]

Final assembly, optics not finshed yet.

[Ben the Ignorant]

Impressive!

[Gina]

Sure is!!

[Chriske]

Oops...!
Forgot to turn one primary cell 90°. silly me...🙄  Will correct that tomorrow.
That 90° rotation has to do with last minor corrections to images overlapping 100%.
This minor correction is absolutely necessary to avoid strain in the eyes/brain during observing.

As a matter of fact the brain does correct very small misalignments of both tubes during observing trough a binocular.
On the other hand it's in fact  amazing how much the brain is able to compensate misalignments. Done some tests in the past how far  I and other people can go while turning one bolt, left or right of my binoculars. You actually can feel the moment the brain 'gives up' while turning that bolt. When it happens the images pops out of alignment in a split-second. When that happened the images are very far apart. Very strange.
You can only do this ones or twice because if you do this trick to often you end up with a splitting headache.

Talking here about misalignment I'm talking telescopes not exactly parallel, not misalignment of the scope(s) optics itself.

 

[Chriske]

Change of concept.
The first tripod I designed was a bit flimsy. It was perfectly ok to hold a smaller scope. As a matter of fact it would have been overkill for a smaller scope I think.
That bino as it is now weigh 10kg (about 20lbs) and I still need to add optics and worm/wormwheel unit. The main pier of that new mount is 270mm in diameter. I added two somewhat thinner branches to make a sturdy triangular construction.
Weight of that tripod 35kg (about 70lbs) It is not only heavy but sturdy and very stiff as well..!
Busy painting that base-platform now.

Next step is add a drive system to the mount. I was planning to install steppers and OnStep software, but I might go for a simple azimuth mount + equatorial platform

[Chriske]

Started drawing a smaller version of what I called, a very, very long time ago, my 'Boxmount'.
The first one I ever made in the early '80 was a very large mount. In fact way to large for it's purpose. After that first one I made it much smaller and ended up with a equatorial mount just over 6" high to be used for scopes up to 20".  Sky&Telescope did published it in one of it's 1983(if I'm not mistaken) issues.
This 'Box-mount' is nothing more then, a wooden plywood box. At the west side is a large and very strong hinge. Alongside that hinge the box is sawn in two parts. So that box can be opened end closed again because of that hinge. At the opposite side is a threaded rod. That rod is there to slowly opening or closing the 'lid' of the box. On top of the box stands a telescope, any scope. Needles to say the hinge is in fact the polar axis. In my case that hinge is mounted at 51°. Rotating the threaded rod opens and closes the box and moving the telescope with it. That's all there is to. My first version I made was 20"x20"x20"(about).
In the years I've built several of these Box-mounts, and made them always less high of course.

I was planning to build a equatorial platform, but decided now to make me another Box-Mount.
In the drawing the threaded rod is not installed yet. But there are, as I always do, a few planes to guide the upper part of that mount over these planes. These planes are absolutely necessary to stabilize the scope during action. Without these planes this mount will not function at all..!

Anyway, this is how my newest Box-Mount will looks like. It doesn’t look like a box anymore, still I call it Box-Mount.
First drawing : looking east.
Height of this mount 170mm.

 

Looking east
In this case I did not use a hinge but a 12mm thick axis(at 51°) running through printed parts(centre).

 

Looking north
Neutral position

 

Looking south.
mount is almost completely closed and ready to start tracking
Tracking is done by pushing the box to it's open position.

 

Still looking south
Box is opened almost completely so the scope has reached the end here

 

In this drawing the Box-Mount is completely opened to have good look 'under the 'hood'.
it's actually very simple.
With this mount I can track up to 2 hours and more. But I will not do that because that will result in tracking errors due to the straight threaded rod. I could install a curved threaded rod but I'm not planning to because this mount and telescope is for visual observing only.

The small white parts are all Teflon, this is to have a smooth ride during action.

I hope it's clear...

 

[Chriske]

Done inserting threaded rod to the Box-Mount. It'll be a thick M16.
Motor will be done later. With this setup I already can, be it manually, track the Moon and planets. The last think I need to do now is to add a few springs or even an 'airpump'. These devices need to be installed between the two major parts of the tracking-unit. Purpose is to release some friction on that M16 nut while tracking. I also could use some counterweight mounted at the polar-axis side but that is not the most 'elegant' solution.
I also redrew a few parts. The initial idea was to push the Box-Mount open to track the stars. I reversed the system. In this new setup I need to lower the top-part instead pushing it open while tracking the stars..

Still a few holes to draw here and there and I'll soon be printing these parts.

In the drawing below the tracking-system is in its open position, ready to start tracking.

Here in its open position, tracking can begin...

 

And here it is almost closed, so the end of the 'ride', after about 2 hours...
Yet again, I will not be using the full length of the rod, because of that tracking error I mentioned earlier. The most accurate 'tracking part' of that rod is the centre part of that threaded rod.

 

 

 

[Chriske]

Busy printing and assembling fork and Box-Mount.

This fork is reinforced with threaded rods. 4 rods vertically and two horizontally for each fork. All that metalwork is well hidden except for the nuts of the horizontally placed rods(visible in the first picture). These four horizontal rods are for more strength to support the scope.

[Chriske]

Two other platforms and tracking-device parts for these platform.

The cardan/gimbal coupling is there for minor alignment errors of the threaded rod. minor misalignment errors of that threaded rod has no ill effect on the tracking speed at all.

Both clamps are reinforced with 12mm brass rods

[Chriske]

And after a few hours in my workshop ....
Between the polar blocks I've put a Teflon ring. On top of the lower guiding-blocks there's also Teflon and on the upper-guidingblocks I've glued formica.
Need to correct a few minor things to have this mount work absolutely perfectly. And I also will, a last time, disassemble the mount to paint it.
I'm very happy with it.
Still, I never used this Box-Mount using a scope with a FL of 2.7 meter as this one is. These mounts I've made in the past were always mounted under a Newt/Dob, rather short FL, like 1.5 meter or so. There were no issues at all, but now with that long FL, will this mount be stable enough...?  I'll soon know, when the optics are ready and mounted.

[Robert72]

The project is coming along very nicely Chriske

[Chriske]

Thanks Robert.
Need to speed up things a bit. Mid Sept. is our open door at the observatory.

This is how far I got today. Tomorrow I'll take it all apart again and paint it all(except for the 'tripod' of course).
A few things need to be done before I hang the scope in it's fork.

Under the central teflon pad is a bolt. Using that bolt I can adjust friction on the outer teflon pads.

[Michele Scotti]

19 hours ago, Chriske said:

Thanks Robert.
Need to speed up things a bit. Mid Sept. is our open door at the observatory.

This is how far I got today. Tomorrow I'll take it all apart again and paint it all(except for the 'tripod' of course).
A few things need to be done before I hang the scope in it's fork.

This is just awesome!

[Chriske]

Thanks Michele..!

Just reassembled the unit after painting. Looks good but the perimeters need some more paint I think.
I also added a large knob for tracking. Eventually that knob will be replaced by a stepper.
It works amazingly well.

Still a bit of work to do on the bino itself, almost done.

 

[Chriske]

First time complete assembly..!

Only the optics and the left-rear cover to add. But I first need to draw all the holes for the switches before printing that cover.
Working now on balancing the scope. Inventors COG indication was not even close.

[Chriske]

So here's that last thing I did before I could have my Kutter-Bino safely mounted it in it's fork. Balancing that thing.
As I said before the COG for these instruments (especially if you build a new one) is never to be predicted.
Just did some tests and yes as I suspected Autodesk-Inventor got it all wrong. No hard feelings toward AI of course. AI does not take into account the different materials I'm using to build this bino.

Anyway, I need to hang about 3kg of weight at a distance of 200mm away from rotation axis I'm using now. All the Kutters I've built in the past the COG was somewhere between the primary and secondary tube. But because I built it completely different now I get this strange result.
For the weights I used sheets of lead, cut to the size so I can swing it between both forks of the mount. Going to print me a nice cover to hide these ugly looking sheets of lead.
In total the scope weight is now nearly 14kg.

After open door 14/15 sept I'm going to relocate that rotation axis, so I can dump the lead. I'll need to redraw and print a few new parts.
The mirrors will be finished and mounted after open door.
Normally this bino would have been completely finished for this year's open door, but my dear friend Marc is very ill. We would have worked together on this bino, especially the electronics is Marc's 'department'. But as he's so ill now, Im not even shure he'll be capable even attending this year's open door.

One more thing, the 'optics' you see in the instrument are merely simple mirrors. Without them that instrument looked a bit weird. So I cut a few disks out of a large sheet. So for this occasion magnification will be zero...😁

[Chriske]

During my balancing procedure I had to stabilize the scope to test different weights/materials.
I first removed the ball bearings because the scope violently turned upside down when I released it. Then I used the 'naked' fork hoping it would give me enough friction to do some further testing but that also didn't work. So I decided to put something in between the fork and 'bearing'. The first thing that came in site was a piece of felt. And did the trick. It not only gave me the needed friction during testing but in the end I left these pieces of felt altogether.

Made a few and helped making an estimate 250 telescopes (during course) sinds 1981, most of the time it were Dobs. We did lots of testing to find better alt-bearings. We mostly used(as most amateurs do) Formica and teflon, good combination indeed. Very often used combination of both Formica/teflon and ball bearings. Lots of other combinations/materials were tested.
Anyway we never thought of using felt between fork and bearing-disks, until now...

I can only say this : Felt works just perfect. It even works just as smooth then all other things we ever tested in the past, including the classic formica/teflon combination. To be clear on the matter, I'm not talking about a very light scope, like a small refractor or a small dob. This bino weigh nearly 14kg..! That would be about the same as a somewhat larger Dob. I do not even have to glue the felt to its fork, it stays in place while rotating the scope in alt. Going to test some more in the future.

I drew the gap between fork and alt-bearing 1.5mm wide. The felt I used was nearly 4mm thick. This seems to be a good combination. But in the end it all has to do how dense that felt is.
Has someone done this before, using a sheet of felt in a alt-bearing..?

 

[Gina]

Would the felt compress with continuing pressure on it?

[Chriske]

I suppose so, but eventually it'll stop compressing. That's why I used rather thicker felt.(Out of my wife's stock).
And when it does and compresses to much I'll add a new layer.(not replace)

[Ben the Ignorant]

58 minutes ago, Chriske said:

Has someone done this before, using a sheet of felt in a alt-bearing..?

Yes, I did that in a homemade dob, in the alt and az bearings. It worked fine for a while then it lost its ideal slickness; I had to use the traditional materials instead. Before replacing it I tried spraying it with silicone lube, worked for a period of time and then lost its properties the same.

[Chriske]

Good to know and also what to expect.
Thanks Ben..!

[markse68]

Can’t you tell inventor what materials each part is and specify density for cog calculation? I know you can in solidworks but no idea how accurate it is- should be accurate though

[Chriske]

18 hours ago, markse68 said:

Can’t you tell inventor what materials each part is and specify density for cog calculation? I know you can in solidworks but no idea how accurate it is- should be accurate though

I suppose so, but I never used that option in the past. As my version is an old one(2008) maybe it is not included. Need to look it up and try it out.

[Peter Drew]

I use ballraces as DEC supports on my 20" and 30" Dobs, they are too heavy for the traditional Teflon support. To control the movement "sticktion" I use adjustable Teflon brake pads bearing against the O/D of the bearings. It's possible to dial up the required amount of friction without losing the inherent smoothness.    😃

[Chriske]

Hey Peter,

Could you please post an image..?