Yoke sticky , hanging up

[carusoam]

From the Nylatron description... Nylon with some form of Molybdenum... or other lubricant depending on the grade selected...

https://www.alro.com/divplastics/PlasticsProduct_NylatronFamily.aspx

-a-

[PT20J]

On 3/9/2021 at 5:23 PM, PT20J said:

According to Kevin Kammer at the factory, the eyeballs are made of Nylatron. I checked the chemical compatibility and it is impervious to most solvents. Kevin says they are supposed to be self lubricating, but he didn't see why Tri-flow couldn't be used.

I've been trying to chase down a little "shudder" in my trim mechanism ever since I bought the airplane a 2-1/2 years ago. It only happens when trimming nose down manually on the ground. I cannot notice it in the air. I finally figured out that the cause was some minor friction in these ball joints. I took them loose from their mounting (but did not take them off the shaft which is a major operation) and cleaned them off. I noticed that the ball feels a little rough in it's motion in the race. I lubed it with some silicone plumber's grease which seemed to help. I also ordered a couple of new ones in case I decide to replace them. I received them today and noticed that the new ones, although smoother, still have a noticeable breakout force if loaded. There are very fine machining marks on the ball and race that increase the friction. You can only see them with magnification, but you can hear them singing if you work the two parts together or run your fingernail across the surface. Polishing the old ones smooth is probably just as good -- perhaps better -- than replacing them.

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UPDATE

Since I’m having the panel redone and access is easy, I had the the eyeball assemblies replaced with the new ones previously ordered. Even though the control column felt pretty smooth after cleaning and lubricating the original ones, the new ones are MUCH better. The reduced friction, and especially breakout force which is the most important parameter in a control system, in the new ones is really noticeable compared to the old ones when manipulating them uninstalled.

Mooney’s recommendation used to be to lubricate them with Tri-Flow but that has changed to a recommendation to keep them dry. Tri-Flow contains a light oil. What I think may happen is that the oil attracts dirt which embeds in the Nylatron and increases friction. The fact that the ball and socket have residual machining marks would make dirt entrapment more likely.

Since Nylatron is impervious to most solvents, the best way to improve existing parts might be to flush with solvent to try to clean them rather than lubricating them, but I haven’t tried that.

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[PT20J]

53 minutes ago, bluehighwayflyer said:

Thanks for this.  I have been wiping my yoke shafts down with Tri-Flow for years and it seemed to help them operate more smoothly.  It’s good to know Mooney’s new guidance.  

I don's see how lubricating the shafts would hurt anything, but I's use silicone spray just because it is a dry lubricant. It's the interface between the ball and it's socket that seems to get rough, so I would not lubricate that. The early M20Js and maybe some others had a swiveling block that the shaft went through rather than the eyeballs and perhaps that's where the lubrication recommendation in the service manual applies.

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[Danb]

4 hours ago, PT20J said:

UPDATE

Since I’m having the panel redone and access is easy, I had the the eyeball assemblies replaced with the new ones previously ordered. Even though the control column felt pretty smooth after cleaning and lubricating the original ones, the new ones are MUCH better. The reduced friction, and especially breakout force which is the most important parameter in a control system, in the new ones is really noticeable compared to the old ones when manipulating them uninstalled.

Mooney’s recommendation used to be to lubricate them with Tri-Flow but that has changed to a recommendation to keep them dry. Tri-Flow contains a light oil. What I think may happen is that the oil attracts dirt which embeds in the Nylatron and increases friction. The fact that the ball and socket have residual machining marks would make dirt entrapment more likely.

Since Nylatron is impervious to most solvents, the best way to improve existing parts might be to flush with solvent to try to clean them rather than lubricating them, but I haven’t tried that.

Skip

 

Great move..