Printed Focusers.

[Chriske]

A while ago I started making printed focusers.
My goal was to make, every time I designed a new one, try and make something completely different. Planning to make some more. I have a few more ideas, but these new designs are not labelled 'urgent'.
To be clear some of these are not my design, most of them are.

This is what I got so far. I know, some have been posted already here on this forum, but I wanted to have them posted all  together in one single thread.
I hope you enjoy this thread.

1- Collapsible focuser.
This one can handle very heavy eyepieces and camera's. Due to its design there's no way it will slip. It also have the ability to push the eyepiece very deep, even a bit in the scope's main-tube. Completely collapsed the focuser is only 28mm high. It's action is very smooth and there's no play at all.
Disadvantage of this one is it's size. And one more thing it needs  secondary hole in the main tube to allow passage of the threaded rod. I usually use a M16 rod, hollow out.
It also has a dual speed unit on board.
I designed this one to discover only a few weeks later that someone made this type of focuser before me. But the (US)guy made it completely in aluminium(very nice one btw)

 

2. Rack and pinion

This is an old design. Not mine of course. Need to work on this one. It's action is way to fast due to too large teeth.

 

3. Helical focuser

Again an old design, not mine either.
I could not have it working without play or smoothly. Maybe it needs some more 'tuning'.

 

4. Helical Focuser BB

That threaded Helical focuser gave me an idea. Instead of threads to do the focusing action why not use ball bearings instead.
The ball bearings in the unit are all tilted at a 4° angle. It works very smooth, there's no play at all and I can adjust the pressure on the eyepiece barrel.

 

5. Helical Focuser BB dual speed

Almost exactly the same as the one here above. But this one I added a dual speed unit. I can rotate the barrel just the same as the one above or use the dual speed knob.

 

6. Crayford focuser.

Not mine but this one is own design. I have two versions. The second version has a very small stepper inside. Working on that one.
Here too, play can be eliminated completely. I also decided not to add a plane onto the focusing barrel to run along.  Works just fine. Also dual speed.

 

7. Inversed focuser

Not my idea either, but I redesigned it.
The focusing barrel is pulled toward the observer. Pressure is controlled by springs in this case. This version has no aluminium barrel. The ball bearings are pushed against two thin strips of brass.

 

8. Crayford (Printed barrel)

The inversed Crayford does not need a aluminium eyepiece barrel, this one does not either.
Both Crayfords here above do have aluminium to run smoothly. The first one has a aluminium barrel for the ball bearings to do the guiding and the Inversed one has a external aluminium plane.
This one has very large pieces of tie-wrap instead of a aluminium plane. There's a rubber O-ring around focusing rod running against a third tie-wrap. It works surprisingly well.

 

9. Timing belt driven focuser.

What I used for this one is a timing belt, a few pulleys and also 2 LMUU8 linear bearings to do the guiding work.
Works perfect and also very smooth action. In this case I used a somewhat larger knob instead of a dual speed unit. Tension on the belt is adjustable.

 

10. Reversed Crayford

Instead of a fixed focuser and the eyepiece barrel going up and down together with the eyepieces, this one works the other way around.
The complete focuser is moving up and down along with the eyepiece around a tube.

More to come...

[markse68]

13 hours ago, Chriske said:

5. Helical Focuser BB dual speed

Almost exactly the same as the one here above. But this one I added a dual speed unit. I can rotate the barrel just the same as the one above or use the dual speed knob.

Wow you keep yourself very busy Chriske!  Awesome work! 😊

on this helical Crayford how does the dual speed knob work? It looks like there’s a ra gearbox going to a wheel pressed against the tube. So is it a geared down method to turn the tube slower? And the wheel just slips when you turn the tube manually?

Edited September 27, 2019 by markse68

[Chriske]

I removed all parts in the drawing leaving only the reduction system. This is how the inside looks like, the red wheels are in fact all gears. I was to lazy to draw the teeth...😊
The black friction-wheel is a rubber O-ring.

Working with the dual speed knob(left) I first push the knob toward the focuser, so the two conical gears do connect. When I only use the eyepiece-barrel I first retract that same axis. That is btw why that dual speed knob-axis is so long. But in fact there's no need to retract the dual speed unit. When I leave it in place during 1:1 speed the reduction system runs at high speed and makes a funny noise

[markse68]

That’s very cool- thanks for showing me 😊

I saw another implementation that used a long roller that contacted the focuser tube with a screw thread that pulled it laterally to finely rotate the tube but thinking about it I think I must be mistaken as it would have to slide when you just turn the tube 🤔 Maybe it was a ptfe pad- I’ll have to see if I can find it again. Your solution avoids that problem- just backdriving the gears like a normal Crayford with geared knob 👍

[Chriske]

Some guy added a stepper to my focuser nr.1
Nicely done..!
He should have installed that stepper at the top side, because now he need to make a rather big hole to allow passage through the telescope tube.

 

[Chriske]

NOT PRINTED.

But I like to show what we did in the past, when printers weren't around yet.

Good focusers were very expensive in those days so we were always trying to make our own. This is one of the focusers we made during course.
To begin with I made one prototype out of aluminium. From that 'master' I made a negative in silicone. Our course-members had to fill that negative with resin, wait to 24hours to demold and this is(was) the result. We made lots of these focusers in those days.

This is nostalgia to me, looking and posting these old pictures here...😊

We even made a dual speed focuser..! Can't find a picture right now, but I'm searching...
That dual speed unit was not as fancy and good looking as the modern versions, but it worked very well.
And yes, the knobs and gears were all resin casted.

 

 

 

Edited September 29, 2019 by Chriske

[markse68]

They're really cool looking too- where did you get the tubes- not turned surely?

 

[Chriske]

1 minute ago, markse68 said:

They're really cool looking too- where did you get the tubes- not turned surely?

 

I have a very large lathe...😉
That was the only disadvantage, lots of work to make these. I never added planes to these tubes, there's in fact no need to.

[Chriske]

One more focuser, but this one has nothing to do with printers or plastic at all.
I'm going back to early '80, to the very start of our telescopemaking course. Goal was to make a telescope as cheap as possible. One of the items to work on was the focuser.
The focuser I came up with back then was nothing more then a long spring loaded wooden plank. It was about 1 meter long. this plank was secured at the lower end of the the scope. At the upper end there was also a small piece of wood.  Purpose of that (dark wood in the drawing) part was to keep the eyepiece in line with the optical axis while focusing.  Focusing was done with the red knob, the yellow knob was to secure the eyepiece in that hole.
At the time we didn't care very much about the small tilting error of the eyepiece. But we never used it on a short telescope.
But hey, it worked..!

[Chriske]

Yet another printed focuser.
Except for a few small bolts and two nuts there's no metal or aluminium involved at all in this Helix variant.
The metal(aluminium) focuser-barrel is replaced by a printed one. The metal ball-bearings are replaced by rubber O-rings.
Bolts and nuts not in the drawing yet.
I'll also print two flanges to put in the focuser barrel at each side. Through these flanges I'll insert a threaded rod(M6 or so) Running the focuser barrel in a powerdrill I will sand the barrel. Purpose is to partially remove the irregularities of the perimeter's printed layers. The eyepieces action will get lots smoother. And if I print that barrel with a very small layer height and sand a bit it will most likely run as smooth as any metal version...I hope...
This time I did choose a 3° angle instead of 4° for the (rubber)guiding wheel.

Testprint on it's way...

 

[Chriske]

Found a few old pictures of that high tech focuser...🤭

[DanyalAG]

Hey Chriske, really love your focusers, especially the crayford and the bearing-helical. I'm looking to mod my scope (smaller secondary+low-profile focuser), and looking online, I quickly found out that low-profile focusers cost a lot. Now I am trying to find resources on any good crayford focuser design (low-profile). The profile I want is between 1.5 to 2 inches racked-in height (1.6 inches would be ideal).

Now I don't really have access to a 3D printer or a lathe, The only tools I have are hand-tools, and some basic power-tools(drill, hole-saw). 

I just wanted to ask if it is possible to build a decent low-profile crayford focuser out of some wood,PVC pipe and ball bearings...You look like you have a lot of experience regarding focuser-making, so any advice or help? Thanks.

[Chriske]

I think you should try a combination of wood and this focuser.
I used printed wheels and O-rings to do the friction on that printed eyepiece-barrel.
If you have no lathe, printers or other machines at your disposal you could make the main body out of wood. The rubber wheels, you can cannibalise them from old copier(zerox) or printers.

You also could make a Crayford. The ball bearings can be replaced by small, thin strips of teflon.
In both cases you could use a PVC pipe as eyepiece-barrel.

So many possibilities, I'd ask Mr Google, just type 'Wooden focusers' or 'Homemade focusers'. Tons of homemade stuff.

[Chriske]

While doing a surge on the net I found this one.
I made it many many years ago, I completely forgot about it...
Teflon strips to guide the focuser barrel. And If you look closely, around the focusing rod is a very thin shim of teflon too.

[Chriske]

Looking for a self-made (very) low profile focuser I didn't found any, except for the one I made.
But there's a printer involved.
Anyway, completely focused 'inward' it's only 28mm high.

[DanyalAG]

Thanks a lot, I really appreciate all the help. That low-profile focuser surely is a thing of beauty.

[Cycliste737]

Hey, Chriske - thanks for your incredible work on all of these innovative designs. I have interest in printing and modifying the helical BB single-speed focuser for 1.25" eyepieces. Any chance I might be able to snag the original CAD files from you for tweaking in Fusion 360? Much thanks!