No name ebay focusing block

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ray_parkhurst
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Post by ray_parkhurst »

Hmm, not a good review at all. I am glad both my attempted orders were successfully canceled and refunded. Seems Peter has saved us all a bit of headache.

I had intended to use the stand in vertical mode, and apply what I learned building the stand I am using now, mostly in terms of getting extreme stability, but more simply. More work ahead.

rjlittlefield
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Post by rjlittlefield »

Certainly not a good review. But noticing the uneven knob, I wonder if the unit was simply damaged in shipping and has a bent shaft. That could go a long way toward explaining rough feel and slipping gears.

--Rik

ray_parkhurst
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Post by ray_parkhurst »

Peter, can you remove the shaft and determine if it is bent, or if the knob has been improperly installed? If it was damaged during shipment, I'm hoping you can get a replacement and it doesn't have these problems.

mjkzz
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Post by mjkzz »

OK, it is not intended as review, just some hands on experience of it.

The "uneven" knob seems to be sloppy craftsmanship , if I turn the fine tune knob on the other side, it is smooth and light, no rattling sound at all, does not feel like the shaft is bent.

Rik, after the clicking sound when I pushed the focus block, it still works and seemingly fine -- I can still move it, fine tune it and everything seem to work. So I do not know if it is bad design or a "protective" design. The sound is like as if the gears have very short teeth and when force is applied, something give in and the teeth of gear just disengage and slip.

Ray, NO, this is definitely NOT for vertical mount, but maybe a horizontal one. I have not tested wobbling yet. I tried to open up the plastic cover of the knobs, but I do not see any screws, tried to hold one end still and turn the other end, nothing is loose. Maybe eventually when I am done with "abusing" it, I will just cut the knob open :-)

ChrisR
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Post by ChrisR »

It looks simply damaged to me - can you return it?
Chris R

mjkzz
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Post by mjkzz »

Chris, both you and Rik were right, I damaged it by pushing it manually :oops: It looks like the teeth on the gear is short and it is made up of aluminum.

I do not think it is bent however. Bottom line is, I do not think it is worth it as I really did not use much force to move it, initially, the knobs turned, then the slipping sound. Oh well, one day, I will disassemble it, just to learn how the fine tune knob works.

Image

rjlittlefield
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Post by rjlittlefield »

Oh dear... :(

An aluminum rack, loosely engaged with the pinion, leading to slippage with obvious removal of metal.

I can no longer think of any situation for which I would consider using this rail.

--Rik

mjkzz
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Post by mjkzz »

rjlittlefield wrote:Oh dear... :(

An aluminum rack, loosely engaged with the pinion, leading to slippage with obvious removal of metal.

I can no longer think of any situation for which I would consider using this rail.

--Rik
can't help laughing . . . one situation though, rip it apart and learn how it is constructed, still puzzled how the fine tune knob work FOR ME.

rjlittlefield
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Post by rjlittlefield »

My guess is that the fine focus mechanism is just a gear train very much like the one shown at http://www.photomacrography.net/forum/v ... hp?t=27549 and discussed at http://www.photomacrography.net/forum/v ... 1807#71807 (which has a link to the repair manual).

If that's not the case, I would be interested to know how it does work.
still puzzled how the fine tune knob work FOR ME.
From the words, I'm not sure what aspect(s) you're puzzled about. The earlier description and the current photo is consistent with a mechanism that has enough flexibility for the rack and pinion to be forced apart under pressure, allowing some slippage and shaving metal off the tops of the teeth. Then when the pressure is released, I imagine the parts flexing back so the teeth engage again, at least well enough to move smoothly with little force applied.

--Rik

mjkzz
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Post by mjkzz »

Thanks Rik, I think I have read those posts, just was not paying attention as it was "irrelevant" -- mechanism of microscope focusing block was not my interest back then. OK that is what I am trying to learn and curious about -- how two coaxial knobs can have different effects, now I understand. I think this one has the same structure (or maybe even less)

On the other hand, it might be good if we put subject on it, use fine tune knob for focus while fixing camera some where. Thanks I will keep it intact instead of cutting it up :D

[Added] FWIW, at the position shown in above picture, neither knobs work, they simply spin around. And like Rik said, with a little push and the gears got engaged again, both knobs work. I do suspect that the damaged gear will cause it to be less precise.[/Add]

AlxndrBrg
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Post by AlxndrBrg »

I would be a bit careful with these products, although I might just have been unlucky when it comes to mine. I dont actually have the fine focus block version, but the coarse one that shipped together with a Olympus stereomicroscope I got on Ebay. The white stand and the moving aluminium focus block are identical, so I assume its from the same factory.

There's no clicking or unevenness, but the focusing knobs continually loosen with use till the point of the microscope descending the rail due to its own weight. The left knob is worse than the right one, when using it on its own it simply loosens the mechanism instead of raising the aluminium focus block. So every now and then I have to tighten up the resistance by turning the knobs in opposite direction... in other words, rather bad quality.

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