Olympus CH & step motor

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Adalbert
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Olympus CH & step motor

Post by Adalbert »

Hello everyone,
1.) what is the easiest way to attach a Raynox to the revolver?
2.) what is the easiest way to remove the knob from the fine drive?
Thank you in advance.
Best,
ADi
Last edited by Adalbert on Sat Nov 06, 2021 5:32 am, edited 1 time in total.

rjlittlefield
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Re: 2 Questions regarding Olympus CH

Post by rjlittlefield »


Adalbert
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Re: 2 Questions regarding Olympus CH

Post by Adalbert »

Hello Rik,
Many thanks for the links!
Best, ADi

Adalbert
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Re: Olympus CH & step motor

Post by Adalbert »

Hello everybody,
Can the black block be removed or will the alignment be lost?
black_block.jpg
Best, ADi

rjlittlefield
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Re: Olympus CH & step motor

Post by rjlittlefield »

I cannot tell exactly how your block is constructed.

Take a look at viewtopic.php?t=26731 for some discussion of alternatives.

On the CHT that I used, the block could not be removed. That's why I used the wooden filler block that I described at viewtopic.php?t=26997 .

--Rik

Adalbert
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Re: Olympus CH & step motor

Post by Adalbert »

Hello Rik,
Unfortunately I don't know the exact name of my OLy
but the attachment is a little different than yours.
It is mounted with 3 screws only:
3.jpg
Best, ADi

rjlittlefield
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Re: Olympus CH & step motor

Post by rjlittlefield »

I cannot tell for sure from your image, but when I study the image very closely, I think that the big black block and one side of the linear bearing are formed as a single piece of metal

That is, it looks to me like your unit has the same structure as the part that I colored blue at viewtopic.php?t=26731 .

If that is the structure, then you cannot remove the big black block except by cutting it off. Removing the bolts will take apart the linear bearing.

Look closely at both ends of that block to determine the structure. You may have to scrape off some paint to be sure.

--Rik

Adalbert
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Re: Olympus CH & step motor

Post by Adalbert »

Hello Rik,
Unfortunately I have a "cheap" version where the thing can not be removed :-(
In the meantime, I have separated the whole focusing block :-)
cut.JPG
Best, ADi

rjlittlefield
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Re: Olympus CH & step motor

Post by rjlittlefield »

OK, then I see two main ways forward:

1. Leave the focusing block the way it is, and make a filler block like my wood at viewtopic.php?t=26997.

2. Cut off most of the black block, and machine what is left to attach an Arca clamp or some other camera/lens mount.

It looks to me like your black block is mostly hollow. If that is correct, then for method 2 you might cut off all but about 15 mm of the black block, cut a filler block that fits mostly inside the black block, and fasten it with bolts through holes drilled in the sides. This could be done without disassembling the focus block, taking care not to stress the linear bearing enough to damage it. Some people would suggest to attach the filler block and/or Arca clamp with epoxy. I would not do that because I do not trust epoxy in weight-bearing applications, but reasonable people can differ on this matter.

--Rik

Adalbert
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Re: Olympus CH & step motor

Post by Adalbert »

Hello Rik,

Many thanks for the hints!

I will follow point 1 and build an adapter out of wood.
In my case this will not be an Arca clamp but a holder of the XY-stage.

I want this to fit my macro-slat. So, instead of the gearbox and linear stage,
the focus block from Oly CH would come with a belt drive.
viewtopic.php?p=199042#p199042
This solution is for very high NA's and it moves the object, not the camera.

For small to medium NA's I have a rail based on the THK KR2001A.
https://www.facebook.com/photo/?fbid=29 ... 0269581589

Best, ADi

Chris S.
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Re: Olympus CH & step motor

Post by Chris S. »

ADi,

I’d go with Rik’s approach number two. That black metal should be very easy to cut. With my electric metal saw, it would take about three seconds. With a hand powered hack saw, it would probably take a number of minutes. Before cutting, I’d wrap the block in stretch wrap (aka “movers wrap”) to help keep metal dust out of it. (Some kitchen plastic wraps would likely work, too.)

For reasons I don’t understand, many of us seem to have a strange aversion to cutting, drilling, and tapping metal. Once this aversion is overcome, metal seems much easier and more predictable to work with than the irregular cellulose composite we call “wood.”

BTW, this particular focus block seemed so familiar that I thought I must have one on my shelves of many focus blocks. But no, while there are a selection of Olympus blocks on these shelves, this particular sort was not among them. Why, then, had I such a sense that I’d seen this mechanism? Re-reading Rik’s post, Anatomy of an Olympus CHT focus/condenser block, provided the answer--this familiarity actually came second-hand. What power well-done documentary photography (and explanation) has!

--Chris S.

Adalbert
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Joined: Mon Nov 30, 2015 1:09 pm

Re: Olympus CH & step motor

Post by Adalbert »

Hello Chris,

Thanks a lot for the hints!

My intention was to compare my already existing gearbox with the belt drive.
I have already ordered some aluminum parts, but still have to wait for them.

In the meantime, I built a prototype out of wood.
step2.jpg
Planned are the pulleys with 80 and 16 teeth.
I had a simple stepper motor NEMA 17 with 1.8 degrees,
if all goes well, one with 0.9 degrees will come instead .

Best, ADi

rjlittlefield
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Re: Olympus CH & step motor

Post by rjlittlefield »

This looks excellent.

One thing: remember to include some spring or elastic to keep the stage pushed against the gears. These focus blocks are not designed to operate horizontal.

--Rik

Adalbert
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Joined: Mon Nov 30, 2015 1:09 pm

Re: Olympus CH & step motor

Post by Adalbert »

Hello Rik,
yes, of course, I do that with my geared rail too.
But really, this is something that should not be missing from any horizontal rail.
Best, ADi

Adalbert
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Joined: Mon Nov 30, 2015 1:09 pm

Re: Olympus CH & step motor

Post by Adalbert »

Hello everybody,

Actually I wanted to make everything out of aluminium
and have already collected some parts but couldn't get some things,
so I made a prototype out of the parts I already had.

I removed the motor with 1.8 degrees from an old rail.

The motor with 1.8 degrees needs 200 full steps for one rotation.
Since I use a TMC controller with 256 microsteps, 200*256 = 51200 microsteps
are needed for one turn.

The gear wheel on the motor has 16 teeth and on the focus block of the Oly has 80 teeth.
So the gear ratio is 5:1 (80:16).

So, for one full rotation of the fine drive of the Oly CH , the motor has to do 51200*5= 256000 microsteps.

Since the fine drive moves the block by 0.2mm for one full turn,
one microstep gives a movement of 0.2mm/256000=0.00000078125mm.
That should be the smallest step of the rail.

That is the theory. In reality, the step size differs slightly from the calculated value :-)

Attached are two photos of the prototype:

Image

Image


video: https://drive.google.com/file/d/1mLNA2l ... sp=sharing

Best,
ADi

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