Reichert Diastar 420 coarse focus problem

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hans
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Re: Reichert Diastar 420 coarse focus problem

#31 Post by hans » Sat Sep 26, 2020 3:06 am

jjcook wrote:
Fri Sep 25, 2020 11:33 pm
Do I need to grease any of these tension washers as I reassemble both sides?
For coarse focus mine had slippery plastic washers, not shown in the drawing, acting like thrust bearings immediately on either side of the bronze bushings installed in plate 58. I figured those were where relative motion was supposed to be happening, so I only greased them, not the spring washer stack. I don't remember the details for fine focus and I think mine were assembled incorrectly when I got them -- one had the relative motion happening between a curved spring washer and bronze bushing causing excessive wear. I reassembled the fine focus assuming the original intent was similar to the coarse focus with a clear distinction between spring washer stacks for tensioning (always with flat washers at both ends) and plastic thrust bearing washers where the relative motion is supposed to occur.
jjcook wrote:
Fri Sep 25, 2020 11:40 pm
...do I need a more involved procedure to get the coarse/fine focus knob initialized in the correct location?
I don't remember there being anything particularly tricky or subtle about this, I just made sure the total coarse plus fine focus range was reasonably centered and didn't have the follower trying to go past the ends cam. On one of my stands I did shift things a bit, as Pete has suggested before, to avoid a worn-in flat spot at the bottom of the cam.

jjcook
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Re: Reichert Diastar 420 coarse focus problem

#32 Post by jjcook » Sat Sep 26, 2020 5:32 am

I completed reassembly of the entire focus stack (Belleville washers and all -- nice spring action), both the coarse and fine focus move smoothly without any hiccups (or well it does when assembled with the knob 118's finger 124 positioned where I don't get the full range of motion to lock the nosepiece at the top position, perhaps a burr in the channel of 56).

However, sadly, the coarse focus provides no resistance to the nosepiece focus arm -- when I remove my hand from the coarse focus control the focus arm just drops to the bottom of its range (limited by focus cam) without any notable resistance (except for the last bit of travel before the focus cam stop, where it does slow as if dampened). :sad:

Do I simply need to lube the right components with the right damping grease to get enough grab??? If so, where to grease? Just the coarse focus pinion shaft and the bearings (if I replace with proper open face bearings)? Or is there a way to adjust the tension?
- Jeff

hans
Posts: 342
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Re: Reichert Diastar 420 coarse focus problem

#33 Post by hans » Sat Sep 26, 2020 6:57 am

jjcook wrote:
Sat Sep 26, 2020 5:32 am
...when I remove my hand from the coarse focus control the focus arm just drops to the bottom of its range (limited by focus cam) without any notable resistance...
The left knob is turning while this happens, correct? Not sure how much effect type of grease would have, but it sounds like there is just not enough clamping force across the plate 58. I found compressing the large coarse focus Belleville washer awkward since fairly high force is required. Perhaps there was some sort of service tool to make it easier to do in the stand, like something that clamped to the shaft in place of the knob with a screw to apply force to the collar before tightening the set screws? I ended up doing it with the plate and shaft removed, shaft hanging though a hole in my desk, and using a socket to press on the collar comfortably, because I was worried about slipping and damaging something trying to do it in the stand. It took a couple tries to get the friction set reasonably, and I think mine ended up a little stiffer than necessary, but since the coarse control is used infrequently and not for precise adjustments I have not felt like messing with it further.

jjcook
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Location: Portland, OR, USA

Re: Reichert Diastar 420 coarse focus problem

#34 Post by jjcook » Sat Sep 26, 2020 7:17 am

Hans — I re-read your post #27 where you suggest that the coarse tension is set by the Belleville washer between 58 and 138. I presume to “adjust” tension I need to insert additional washers (which will be non-trivial as it was already a tight fit)? Or do I rely on the set screws?

Edit: just saw your reply, I will have to take the left-hand side apart to check but I don’t think the Belleville washer was any larger than the others on the fine focus and it did not require much effort to secure the coarse focus knob (which does turn with the right coarse knob but with a little slip if I try to disengage them).

To ease dis/assembly, what is the proper tool to remove and install this piece?
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- Jeff

BramHuntingNematodes
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Re: Reichert Diastar 420 coarse focus problem

#35 Post by BramHuntingNematodes » Sat Sep 26, 2020 11:45 am

Gonna want a "e clip" tool for your e clips
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

jjcook
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Location: Portland, OR, USA

Re: Reichert Diastar 420 coarse focus problem

#36 Post by jjcook » Sat Sep 26, 2020 4:42 pm

Here is the stack up on the left hand side as it originally came, it seems the Belleville was in the wrong location sandwiched between the set screw collar and it’s tab washer. Overall the stack up between the coarse focus knob and the frame doesn’t provide any spring tension. I will try placing the Belleville between the set screw collar and the coarse knob, but I’ll have to add a washer so that the knob does not drag on the frame... stay tuned.

Edit: or should I place the Belleville between 58-nylon washer and the collar assembly (so it’s the collar that creates tension not the knob)?
  • e-clip
  • washer
  • fine focus knob
  • washer
  • curved washer (concave out)
  • washer
  • curved washer (concave in)
  • washer
  • e-clip
  • washer
  • curved washer (smaller)
  • coarse focus knob
  • set screw collar
  • Belleville washer (concave out)
  • tab washer (why tab?)
  • nylon washer
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- Jeff

hans
Posts: 342
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Location: Southern California

Re: Reichert Diastar 420 coarse focus problem

#37 Post by hans » Sat Sep 26, 2020 5:46 pm

BramHuntingNematodes wrote:
Sat Sep 26, 2020 11:45 am
Gonna want a "e clip" tool for your e clips
Wait, there's an alternative to prying awkwardly with a screwdriver until you eject the clip across the room while stabbing yourself in the hand???
jjcook wrote:
Sat Sep 26, 2020 4:42 pm
Here is the stack up on the left hand side as it originally came...
Ignoring the fine focus stuff (as I mentioned earlier I'm not sure what the original design was and every one I disassembled was put together differently) that looks correct and refreshes my memory a bit. So the main differences from the patent drawing are:
  • The one-piece knob shown in the drawing is two parts, the collar which actually retains the friction stuff, and the knob which just gives the user something to grip.
  • The metal flat washer closer to the frame has the tab that reaches over the Belleville washer and forces the relative motion to happens between the bushing, plastic washer, and tabbed washer.
  • The drawing omits the part on the other side of the plate that retains the friction stuff in the other direction: "auto-focus" gear on the earlier versions or just a plain collar on the later versions.
On all mine there is an E-clip on the inside setting the position of the gear/collar but nothing setting the position of the outer collar. So yeah, as far as I understand, you have to somehow squeeze the inner gear/collar and outer collar together, compressing the Belleville washer in between, while tightening the set screws in the outer collar. That is the part I was saying I found awkward and did with the plate and shaft removed from the stand. I don't think the left knob should be involved in setting the friction, and I think you could reassemble everything with only the collar leaving out the left knob and it would work the same, just hard to get a grip to turn the shaft.

hans
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Re: Reichert Diastar 420 coarse focus problem

#38 Post by hans » Sat Sep 26, 2020 5:53 pm

hans wrote:
Sat Sep 26, 2020 3:06 am
I don't remember the details for fine focus and I think mine were assembled incorrectly when I got them -- one had the relative motion happening between a curved spring washer and bronze bushing causing excessive wear.
It looks like yours was put together this way also (the spring washer I was referring to is the one just above the coarse knob in your photo) so maybe this really is how they came originally?

hans
Posts: 342
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Re: Reichert Diastar 420 coarse focus problem

#39 Post by hans » Sat Sep 26, 2020 6:13 pm

One thought regarding where, if anywhere, to put damping grease -- in the newer versions without the spring-loaded parallel fine focus gear train I think good fine focus response is relying on the weight of the focus arm taking up any play/backlash in the chain going coarse shaft -> FF gear train -> cam -> follower -> arm. So that whole chain of stuff needs to move freely with low friction, I think.

jjcook
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Location: Portland, OR, USA

Re: Reichert Diastar 420 coarse focus problem

#40 Post by jjcook » Sat Sep 26, 2020 6:26 pm

:) :) :)

Got it — thanks hans! I was able to tension the Belleville washer by placing several hand weights on the other side of the scope (including one to keep the right side fully engaged), then using a socket to apply firm but even pressure on the collar I then secured the set screws of the collar.

A quick test with nosepiece and four objectives, it does not appear to be creeping and appears to hold at any position along its range — although I have not checked through the eyepieces yet to detect minor creep.

I may yet disassemble the focus again to apply damping grease in select areas before I button it up for good but I’m happy to know the unit is a keeper.

Now the only other significant issue is that the eyepieces are both delaminated and I’ll need to find replacement 181’s, perhaps part of a binocular head to switch out the slightly delaminated prism as well in the trinocular. At this point I can finish engaging with the seller for a partial refund which he originally proposed due to the coarse focus issue.
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- Jeff

hans
Posts: 342
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Location: Southern California

Re: Reichert Diastar 420 coarse focus problem

#41 Post by hans » Sat Sep 26, 2020 6:56 pm

Glad to hear it is working. I have one eyepiece looking exactly like yours on the right, so I guess it is not an uncommon problem.

hans
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Re: Reichert Diastar 420 coarse focus problem

#42 Post by hans » Sat Sep 26, 2020 7:17 pm

Do you remember if your plastic coarse focus friction washers has any grease on them initially? I'm pretty sure mine did, and I regreased them, but I am wondering if maybe they could be some special pre-lubricated plastic that is intended to be used without additional grease, and greasing them is why I need such high clamping force?

PeteM
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Re: Reichert Diastar 420 coarse focus problem

#43 Post by PeteM » Sat Sep 26, 2020 7:29 pm

Just in case others have the problem tensioning the Belleville washes, a 12" "Quick grip" clamp with it's soft padded jaws and hand grip can reach from knob to knob and apply light pressure on the washers. Handy for their original woodworking purpose as well.

https://www.amazon.com/IRWINQUICK-GRIPO ... 614&sr=8-6

hans
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Re: Reichert Diastar 420 coarse focus problem

#44 Post by hans » Sat Sep 26, 2020 8:13 pm

What would be really nice is an adjustable way to temporarily compress the friction stack without interfering with focus operation, so that friction could be adjusted while running the focus up and down and checking for feel and slipping. Like maybe if the shaft is a standard size you could drill/tap two or three holes axially in an off-the-shelf shaft collar, then with the collar clamped where the coarse knob would normally go use screws through the temporary collar to apply force to the real collar and get the friction correct before tightening the set screws?

jjcook
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Re: Reichert Diastar 420 coarse focus problem

#45 Post by jjcook » Sat Sep 26, 2020 8:28 pm

hans wrote:
Sat Sep 26, 2020 7:17 pm
Do you remember if your plastic coarse focus friction washers has any grease on them initially? I'm pretty sure mine did, and I regreased them, but I am wondering if maybe they could be some special pre-lubricated plastic that is intended to be used without additional grease, and greasing them is why I need such high clamping force?
My plastic washer had a light amount of black discoloration on the surface (don’t have a photo) but it wasn’t at all gummy.
- Jeff

jjcook
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Re: Reichert Diastar 420 coarse focus problem

#46 Post by jjcook » Sat Sep 26, 2020 8:30 pm

PeteM wrote:
Sat Sep 26, 2020 7:29 pm
Just in case others have the problem tensioning the Belleville washes, a 12" "Quick grip" clamp with it's soft padded jaws and hand grip can reach from knob to knob and apply light pressure on the washers. Handy for their original woodworking purpose as well.
Thanks for the tip — I’ll try that when I go to add grease.
- Jeff

jjcook
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Re: Reichert Diastar 420 coarse focus problem

#47 Post by jjcook » Sat Sep 26, 2020 8:46 pm

hans wrote:
Sat Sep 26, 2020 8:13 pm
What would be really nice is an adjustable way to temporarily compress the friction stack without interfering with focus operation, so that friction could be adjusted while running the focus up and down and checking for feel and slipping. Like maybe if the shaft is a standard size you could drill/tap two or three holes axially in an off-the-shelf shaft collar, then with the collar clamped where the coarse knob would normally go use screws through the temporary collar to apply force to the real collar and get the friction correct before tightening the set screws?
Without disturbing the focus mechanics, another similar idea would be to attach the temporary set screw plate to the frame after drilling a few holes... but I might first just try a screw clamp with socket inspired in part by Pete
- Jeff

jjcook
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Re: Reichert Diastar 420 coarse focus problem

#48 Post by jjcook » Thu Oct 01, 2020 11:05 pm

I'm getting a reasonable refund from the seller due to the focus and the need for replacement eyepieces. Any recommendations if I should look for something other than 181 eyepieces? Also since I'm missing a 20x, I picked up one of those cheap Nikon 20x PlanApos but have yet to order an M25 to RMS adapter to try it out (and later related parfocality adapters for the other objectives if it works out). Anyone try one of these on the 410/420? If so, how is it and the parcentricity?
- Jeff

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