yoke shaft phenolic block maintenance/replacement

[Vance Harral]

In photo 1 below, the red arrow points to the phenolic block which supports the right side yoke shaft, just aft of the panel.  It's mounted to the steel tubing that also holds the instrument panel itself.  Photo 2 is a shot from many moons ago during an avionics upgrade, which shows the block a little more clearly (in the red circle).

Periodically when moving the elevator during preflight inspection, the yoke shaft "chatters" in this block.  It's been doing so for a couple of years now.  When it does, we break out the silicone spray, use it to lubricate the yoke shafts, and the chattering goes away for a while.  But it always comes back.

At one point I took a close look and found what's arguably a little excess play in the block.  As far as I know it's original equipment, and I suspect it's worn a bit over 40 years of service.  This seems to be a likely root cause of the chattering.  So I dutifully ordered a new phenolic block from LASAR to replace it.  But the mechanic and I gave up on the job when we discovered there is (apparently) no way to do so without disassembling the instrument panel, like in photo 2.  If I had a time machine, I'd certainly go back and replace it during the avionics upgrade!

Has anyone figured out a way to replace these things easily?  It's simple enough to unscrew the block from the steel tubing, but then you just have a loose block which you can't slide off the shaft.  It won't slide off the back end due to the control linkage welds.  It won't slide off the front end (after removing the yoke) because it won't fit through the hole in the instrument panel.  I think some year models have a bigger hole in the panel here - maybe ours could be dremeled out as a minor mod?  Or I guess we could just wait for the next avionics upgrade, but that's likely a long time away.  Anyway, this seems like the kind of thing someone has a clever solution for.  Any experts out there?

Alternatively, is there a different cause/fix for the chattering problem?  I was just guessing a new phenolic block would fix it, I don't really know that for certain.  The yoke shaft itself is in good shape (recent inspection per AD 77-17-04), and I'm confident it's binding at the phenolic block, not anywhere else in the linkages.  I suppose it's possible there's just dirt and grime in the block, and the play would otherwise be OK without it.  But I'm not sure how you'd clean it out without causing more problems than you're solving.  Any tips or advice would be appreciated.

[N201MKTurbo]

I don't think it needs replacing it just needs proper lubrication and cleaning. It always seems to be the copilot side, it must be because nobody is leaning on that one. 

I would need to look In the manual to see what the specified lubricant is but I don't think it is silicone spray. My experience with silicone is it doesn't last very long. You want something that will last a long time. I have always used the same stuff I use on the rod ends. I have been using Fluid Film for the last ten years. That stuff seems to last forever. 

Either way I apply a fairly heavy coat both in front and behind the panel then work the yoke in and out and back and forth a bunch of times then wipe the shafts down repeat until the shafts are clean after doing this. If they haven't been properly cleaned and lubed for a while it could take a while. Be sure to remove the carpets or put down a towel so you don't get lube on the carpets.

Properly lubed yoke shafts make your plane fly a lot nicer.

Edited January 8, 2017 by N201MKTurbo

[Guest]

Vance,

I've never changed one, I have seen the shaft with a slight bend which caused binding.  I would think that you'll have to remove the wheels from the shafts and then remove the shafts from the plane in order to replace the guide block.

Clarence

[Marauder]

Vance - you have the new style yokes on your 76. If you are still subject to the AD, then either they replaced the Mongo yokes found on the 75s with the modern style yokes or they did the switch to the newer yokes in the 76 model but kept the prior year's rods and blocks.

I had my 75 F converted to the new style yokes in 1998 when I did my autopilot upgrade. This included new rods not subject to the AD, blocks and the yokes. I notice a lot more play in the newer style yokes/rod than the Mongo yoke/rod combo.

I'm slated for an ADS-B install this winter and was going to have them look at the right side yoke for the excessive play. As far as I know, it is not easily accessible with the panel in place. I am glad to hear there are replacement blocks. If you do replace them, please let us know the process.

As for silicone, Turbo is right, the silicone only lasts for a bit.


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[Vance Harral]

Thanks to all for the replies so far.

I'm open to suggestions on a different lubricant.  The official maintenance manual isn't helpful here, as this is one of those cases where the 1976 F was actually designed with some J-model parts.  The yokes and shafts in our airplane are factory original (as far as I know from the logs).  Hence AD 77-17-04 still technically applies by model and serial number, even if it's arguably unintentional.  The F maintenance manual calls for powdered graphite lubricant on the "control column bearing ball", but our airplane doesn't have a ball at that spot like the older models do.  The J maintenance manual calls for Triflo (teflon) spray, which I'm willing to try.  I confess I assumed there wasn't much difference between Triflo and garden-variety silicone spray, but perhaps I'm mistaken.

As for lubricants that last "a long time", my general rule of thumb is heavier lubricants (more oil/grease content) last longer, but they're also more prone to gathering dirt and dust.  I've considered trying something like LPS-1 or LPS-2 on the yoke shafts, but I just don't want oily stuff around the interior.  Sooner or later it gets on your fingers, then on the upholstery, then on the avionics screens, etc.  But again, I'm no expert here - open to suggestions.  The thing is, we've been using silicone spray on the yoke shafts per mechanic's advice for over a decade, and this problem has only cropped up in the last couple of years.  That's what makes me think the block is wearing.

[Marauder]

Thanks to all for the replies so far.
I'm open to suggestions on a different lubricant.  The official maintenance manual isn't helpful here, as this is one of those cases where the 1976 F was actually designed with some J-model parts.  The yokes and shafts in our airplane are factory original (as far as I know from the logs).  Hence AD 77-17-04 still technically applies by model and serial number, even if it's arguably unintentional.  The F maintenance manual calls for powdered graphite lubricant on the "control column bearing ball", but our airplane doesn't have a ball at that spot like the older models do.  The J maintenance manual calls for Triflo (teflon) spray, which I'm willing to try.  I confess I assumed there wasn't much difference between Triflo and garden-variety silicone spray, but perhaps I'm mistaken.
As for lubricants that last "a long time", my general rule of thumb is heavier lubricants (more oil/grease content) last longer, but they're also more prone to gathering dirt and dust.  I've considered trying something like LPS-1 or LPS-2 on the yoke shafts, but I just don't want oily stuff around the interior.  Sooner or later it gets on your fingers, then on the upholstery, then on the avionics screens, etc.  But again, I'm no expert here - open to suggestions.  The thing is, we've been using silicone spray on the yoke shafts per mechanic's advice for over a decade, and this problem has only cropped up in the last couple of years.  That's what makes me think the block is wearing.

I used silicon for a number of years and it really never made that much of an improvement. Tri-flow is a petroleum distillant like many of these lubricants. I used Tri-flow on the Heim joints of the control surfaces for years. Again, works but nothing noteworthy.

I had this French door lock on my house that was a bear to open and the key never went in smoothly. I tried silicon, Wd-40 and even Tri-flow without any real improvement. Then I came upon Deep Creep from Sea Foam. What a difference that made. I became a believer when my starter kept acting up. I had been spraying it for years with silicon and the bendix periodically would hang. I tried Deep Creep on it over a year ago and not issues since. I haven't tried it on the yokes, but I am tempted.

If you elect to use Tri-flow, they make a pin point applicator.
http://www.triflowlubricants.com/product/pin-point-lubricator



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[N201MKTurbo]

A greasy Mooney is a happy Mooney....

[Will.iam]

On 1/8/2017 at 8:24 PM, Marauder said:

 

 

I used silicon for a number of years and it really never made that much of an improvement. Tri-flow is a petroleum distillant like many of these lubricants. I used Tri-flow on the Heim joints of the control surfaces for years. Again, works but nothing noteworthy.

I had this French door lock on my house that was a bear to open and the key never went in smoothly. I tried silicon, Wd-40 and even Tri-flow without any real improvement. Then I came upon Deep Creep from Sea Foam. What a difference that made. I became a believer when my starter kept acting up. I had been spraying it for years with silicon and the bendix periodically would hang. I tried Deep Creep on it over a year ago and not issues since. I haven't tried it on the yokes, but I am tempted.

If you elect to use Tri-flow, they make a pin point applicator.
http://www.triflowlubricants.com/product/pin-point-lubricator



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Did you ever try the deep creep from sea foam? PIREP?

[Marauder]

Did you ever try the deep creep from sea foam? PIREP?

No, other than the one time on the starter bendix (which is still working great without any further lubrication).

I was always concerned the Deep Creep would mess up the phenolic block. Still using silicone.


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[M20F-1968]

On 1/8/2017 at 3:03 AM, Vance Harral said:

In photo 1 below, the red arrow points to the phenolic block which supports the right side yoke shaft, just aft of the panel.  It's mounted to the steel tubing that also holds the instrument panel itself.  Photo 2 is a shot from many moons ago during an avionics upgrade, which shows the block a little more clearly (in the red circle).

Periodically when moving the elevator during preflight inspection, the yoke shaft "chatters" in this block.  It's been doing so for a couple of years now.  When it does, we break out the silicone spray, use it to lubricate the yoke shafts, and the chattering goes away for a while.  But it always comes back.

At one point I took a close look and found what's arguably a little excess play in the block.  As far as I know it's original equipment, and I suspect it's worn a bit over 40 years of service.  This seems to be a likely root cause of the chattering.  So I dutifully ordered a new phenolic block from LASAR to replace it.  But the mechanic and I gave up on the job when we discovered there is (apparently) no way to do so without disassembling the instrument panel, like in photo 2.  If I had a time machine, I'd certainly go back and replace it during the avionics upgrade!

Has anyone figured out a way to replace these things easily?  It's simple enough to unscrew the block from the steel tubing, but then you just have a loose block which you can't slide off the shaft.  It won't slide off the back end due to the control linkage welds.  It won't slide off the front end (after removing the yoke) because it won't fit through the hole in the instrument panel.  I think some year models have a bigger hole in the panel here - maybe ours could be dremeled out as a minor mod?  Or I guess we could just wait for the next avionics upgrade, but that's likely a long time away.  Anyway, this seems like the kind of thing someone has a clever solution for.  Any experts out there?

Alternatively, is there a different cause/fix for the chattering problem?  I was just guessing a new phenolic block would fix it, I don't really know that for certain.  The yoke shaft itself is in good shape (recent inspection per AD 77-17-04), and I'm confident it's binding at the phenolic block, not anywhere else in the linkages.  I suppose it's possible there's just dirt and grime in the block, and the play would otherwise be OK without it.  But I'm not sure how you'd clean it out without causing more problems than you're solving.  Any tips or advice would be appreciated.

When I did my rebuild,  I replace the phenolic blocks  in the belly which are meant to protect the  pushrods with nylon blocks.   My DER  approved the replacement.   The phenolic material  is abrasive  and the nylon seems to work much better.   Perhaps a similar exchange  can be done with the yoke shafts.   I don't have a problem with the yoke shafts in my plane  as my parts are out of innovation  and the the parts are made differently.

John Breda