Pushing/Pulling the X/Y Table?

[josmann]

Hey folks - one thing I find myself doing pretty much by reflex when microbe hunting is holding just the bottom knob of the X/Y manipulator and only twisting to move the slide side to side. I just pull and push back and forth to pan in Y if I'm tracking a motile bug.

Would you say this is generally alright to do or will it kill the mechanism if performed too much? I'm specifically wondering about the stages commonly found on lower end Chinese microscopes. I feel like it's probably fine for the more premium stages which glide very easily when properly maintained.

[BramHuntingNematodes]

If you break a cheap Chinese stage buy another one that's how they are intended to be used

[josmann]

If you break a cheap Chinese stage buy another one that's how they are intended to be used

Haha, not sure if you mean another stage or another scope!

[Charles]

What you need is a rotating gliding stage. You can push, pull and turn all in one motion.

[PeteM]

+1 on the gliding stage. Nikon made a nice one for their old black S series microscopes that might be adapted to other scopes.

Many of the newer scopes -- and even Olympus BH2 series -- went to plastic gear racks for the stage. It's quite common to see these with cracks - and then eventual failure. If you really want to glide in one direction, you might remove the rack and relube with a slightly damping grease and adjust the stage so it feels about right. Stages are cheap enough to buy used and easy enough to swap on many microscopes, you might just want to turn one into a glider and use that one while directing and filming cantankerous protist actors?

That said, a proper gliding stage will have a better feel.

[josmann]

A gliding stage definitely sounds nice! If you have any recommendations for one that may be BH2 compatible/moddable, I'd appreciate it.

Many of the newer scopes -- and even Olympus BH2 series -- went to plastic gear racks for the stage. It's quite common to see these with cracks - and then eventual failure.

I think it's not so bad to do this on the BH2 or similar quality scopes, though, so long as the bearing and housing of the drive shaft are robust and keep the pinion oriented the same regardless of the moment force. I think so long as the pinion runs parallel to the rack gear, it's mechanically equivalent to push/pull or turn the knob. The risk, perhaps, is in wearing down the bearing itself - so it would be wise to only do it for a stage that moves very freely. Do you have recommendations for greases that can be used to fine tune motion? Right now I just slather Krytox on anything that's sticky.

[BramHuntingNematodes]

They make a silicone differential fluid for remote control airplanes that has varying degrees of viscosity. I have some of the 500,000 cst stuff which is very viscous and specced for turntable needle drop damping. It also works nicely as damping grease-- although you may tone it down a bit for the gliding stage which should move pretty freely.

[josmann]

They make a silicone differential fluid for remote control airplanes that has varying degrees of viscosity. I have some of the 500,000 cst stuff which is very viscous and specced for turntable needle drop damping. It also works nicely as damping grease-- although you may tone it down a bit for the gliding stage which should move pretty freely.

Interesting, thanks! Definitely not something I would’ve thought to buy.

[PeteM]

I'd be a bit cautious pushing a BH2 stage around and hoping for long life. The force of the plastic rack being shoved around is running up against a tiny steel pinion gear. The mechanical advantage is, in a sense, going the wrong way. I'd think most of the wear is going to be that small steel gear digging in against the plastic - eventually leading to wear, cracks, and breakage (as I've seen in several BH2 stages). Not a huge deal perhaps, if the plastic racks are still available. As noted before, you could just unscrew the rack, set it aside, and have no concerns about any wear from the pinion through the shaft to the knobs. But it would only be push-pull for whatever axis had the rack removed.

Lube wise, I'd think you'd want the lightest possible grease - oil-like - so the pinion spins freely and the knobs adjusted for low tension if you keep the rack(s) in place. Then put the damping in the ball bearing slides and the clearance adjustment. A light damping grease - a bit more viscous than normally used - might be about right to drive the stage around by pushing and pulling.

The Nikon stage mentioned earlier has a wonderful feel - the equivalent of a fluid head in cinematography. You'd have to be careful, though, in adapting it to a BH2 that the total thickness of that stage (reasonably thin) and any adapter didn't put the stage too high for the condenser to focus properly.

It may well be that Olympus made a gliding stage for the BH2. If so, they're likely rare - haven't seen one yet. They do make them for the BX scopes.

[josmann]

The force of the plastic rack being shoved around is running up against a tiny steel pinion gear. The mechanical advantage is, in a sense, going the wrong way.

I think it's a little more complicated than that - I could just as easily say that the steel gear is being shoved up against the plastic rack in the opposite case! There's a nuance here:

Imagine if the rails were really sticky and gummy while the shaft holding the pinion was exceptionally well lubricated. Turning the shaft, all the force to break the stiction of the rails would be applied at the gear interface. If, however, you pull directly on the stage, then the force to break the stiction comes from wherever you're pulling and the force at the gear interface is practically zero (assuming exceptional lubrication means zero force is needed to turn shaft). In this case it is better to pull the stage directly than use the shaft.

If the rails slide really nicely but the shaft lube is sticky, then everything is opposite and it's better to use the shaft because you break the stiction directly rather than using the gears.

So the answer to safely pulling and pushing the stage is to have a really nicely lubed Y translation shaft! (Or, like you said, pull the gear entirely)

I'll keep an eye out for gliding stages - they don't seem to be highly available at reasonable prices although I'm sure they're often inadvertently included in many surplus sales. At the very least, the metal toothed stage from the Labophot 2 is compatible with the BH2 so that's a source of inexpensive spares if the plastic gears give out.

[PeteM]

The suggested lube case was if you choose to become a devoted push-puller. As you say and we agree, it doesn't work so well if you drive a sticky stage with the tiny pinion. And also why just detaching the plastic rack could be the safest bet (and maybe having one gliding stage for following pond critters and another for x-y translation a twist of a knob at a time).

[josmann]

Okay well after that enlightening discourse and disassembling my 380B manipulator, I think the answer for my Chinese scopes is clear. One of them (the Swift 380B) uses an extremely tacky grease for the rack and pinion. It crackles and pops as the teeth engage and disengage and generally feels awful to use. The tension adjustment has almost no effect because the grease practically glues everything together. The other is definitely using a different grease despite the components being identical and feels nicer to use, though still a bit stiff for my preferences.

I think I will try my hand at degreasing the 380B and using something a bit less tacky to improve the feel.

[MichaelG.]

A gliding stage definitely sounds nice! If you have any recommendations for one that may be BH2 compatible/moddable, I'd appreciate it.

.
The one for the little Wild M11 is delightful

MichaelG.

Ref. http://www.science-info.net/docs/wild/m11-catalog.pdf