Grease for ball planetary reduction drives

Joined
Aug 14, 2019
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Bologna, Italy
Hello. I have an old problem, only partially solved, and I am asking advice to solve it completely. Old electronic instruments (also old radios) often had knobs equipped with a reduction drive. We are speaking of very low speed and low torque miniature planetary drives, built like a ball bearing with the ball cage connected to the output shaft. After many years of service, the grease inside tend to leak out and the drive start to slip, in the beginning in some positions, then everywhere. Inspection don't show any evidence of wear, so, fill it again with the proper grease will almost surely result in a complete recovery. ...but this is "the problem". Which grease? I tried four kind of greases with bad results (green lithium soap NLGI 3 for automotive bearings, black lithium soap and molybdenum disulfide NLGI 2 for homokinetic joints, white lithium and zinc oxide NLGI 2 for gearshift control linkages, brown copper NLGI 2 "antigrip"). They make the ball slip better, instead of have the right friction to move the output shaft. Finally I had some success with a chinese XY-2, transparent silicone based damping grease (no data on viscosity)... drive work, but not "like new", and the damping grease, while it's sticky almost like the original grease, flows (albeit slowly) outside the drive through spaces while the original didn't at all. What was inside there originally? Residuals of the grease are brown caramel color, or brown/dark green, and so sticky that you may think it's glue... Thank you for your help and best regards, Andrea.
 

Kestas

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Your post lists many individual applications, each of which would require a separate and unique discussion. The grease in many of the listed applications in your post suffer either from oxidation due to age (old radios) or washout from road wash. I use silicone based grease in both applications. Otherwise you may be overthinking it. Why are you using Grade 3 for wheel bearings? It is too thick. It will be pushed aside and not reflow to where it is needed.
 

Ermione

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Hello. Sorry if my post wasn't clear. I need the grease for only one application, the ball planetary reduction. I listed the grease I had handy, the ones I tried without success. Andrea.
 

Kestas

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For hand operated equipment use a light grease, no more than Grade 2. Again, I use silicone in these applications.
 
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I formulated a silicone-based semi-fluid with a gelling agent for a potentiometer years ago. It was very high vis and tacky. The object of using it was smooth tuning and holding a set position without wondering. Nye Lubricants makes such products based on esters, PFPE and possibly silicone.
 

Kestas

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That would be Nyogel. I have 7 pounds of that stuff. It's good for optical equipment where you need to lube the screw adjustments, but want the adjustments to hold position without drifting. I guess that would make it a shear-thinning fluid. It is not silicone. It cleans easily with mineral spirits.
 

Ermione

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Aug 14, 2019
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Hello! Thank you for the answers. About John Deere Corn Head grease, I read about it, probably here. I should try it, but it should be very tacky. Is it? About Nyogel, I had the idea of trying the PG-44A, but I got a suggestion from one maker of such planetary drives, that PG-44A and the other Nyogel, like 774 and 868 aren't the right product. He didn't want to tell me more, as it's a trade secret, but at least, he told me they aren't using Nyogel. I need something that will not drip out even after long time... Andrea.
 
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It makes sense that the Nyogel that Kestas has is mineral spirits soluble. There are seven or eight Nyogels and I think they are all silica gels based on synthetic hydrocarbons. This would probably be PAO and polybutene, both of which are soluble in that solvent. The idea of shear thinning is also correct. The shear thinning gives smooth operation and the rapid return to its viscous state prevents drift. The product that I developed was silicone-based for a Japanese electronics company. The main requirements were meeting torque values under various conditions.
 
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