Yoke and Yoke Shaft Refinishing

How to keep the Cessna 170 flying and airworthy.

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hilltop170
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Re: Yoke and Yoke Shaft Refinishing

Post by hilltop170 »

n2582d wrote: I soaked my yokes in paint stripper overnight. Cleaned up great.
Gary
Did you soak the yokes in paint thinner to soften up the old plastic coating to make it easier to remove or just to clean them?
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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n2582d
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Re: Yoke and Yoke Shaft Refinishing

Post by n2582d »

To soften the plastic coating. No scrapping needed, the stripper turned the coating into a gel. Rinsing with water and Scotchbrite pad removed the last of the coating.
Last edited by n2582d on Thu Sep 24, 2020 7:33 pm, edited 1 time in total.
Gary
hilltop170
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Re: Yoke and Yoke Shaft Refinishing

Post by hilltop170 »

That is an outstanding discovery!
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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lowNslow
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Re: Yoke and Yoke Shaft Refinishing

Post by lowNslow »

n2582d wrote:To soften the plastic coating. No scrapping needed, the stripper turned the coating into a gel. RinsIng with water and Scotchbrite pad removed the last of the coating.
Gary, what brand of stripper did you use, the real nasty stuff ?
Karl
'53 170B N3158B SN:25400
ASW-20BL
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n2582d
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Re: Yoke and Yoke Shaft Refinishing

Post by n2582d »

Karl,
I used Napier SV-35. I think it's changed names more than once since I bought it.
Gary
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brian.olson
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Re: Yoke and Yoke Shaft Refinishing

Post by brian.olson »

Progress update (summary: we're just getting started):

62C made it out of annual with no great surprises (always a good thing) and it's time to fly for a bit; frankly in no hurry to take her out of service again, so the things we're doing right now are mostly prep in nature.

First off - some good news. I ran a test with some 3M chrome polish and at first glance it appears that I will *not* need to have the yoke shafts re-chromed. There was some surface rust and staining on both shafts but with some time and elbow grease the majority of it came off. When we eventually pull the yokes out I'll spend a little more concentrated time on them to get the rest of the staining off.
Yoke Shaft - pre polish.JPG
(Yoke shaft condition pre-polish)
Yoke Shaft - after polish.JPG
(Yoke shaft post-polish)

I initially ordered four Delrin balls from McMaster-Carr and did some test drilling on them to test out the quality and process. Our drill press is/was an old busted-up-but-functional garage-sale purchase from many, many years ago and it quickly became apparent that the quality of the table-top drill press and it's inability to drill precisely wasn't going to give a successful outcome. We purchased a new drill press from a big-box store (table-top, but of a better quality). I also turned on my engineering brain and created a drilling jig on our 3D printer that enabled me to securely hold the ball and alignment. Worked like a charm.
Drilling Jig.JPG
(3d printed drilling jig)
Drill Press.JPG
(Drilling in progress)

As Bill had previously mentioned, we found that each of the Delrin balls had various amounts of holes/voids within the internal structure and it was hit and miss whether the finished product would be usable. I quickly used up the four balls I had ordered, and ordered ten more. McMaster-Carr had them on my doorstep twenty-four hours later. After drilling eight of them (thus far) I have three reasonably-usable, but I'll make the final judgement call once we are able to perform the test-fits. I will also do a final fitting/sanding once I have the yokes pulled out of the plane.
Delrin Ball with hold.JPG
(Finished product)


Next steps:

1. We are still waiting for the vinyl yoke graphics to arrive (don't get me started on the problems with USPS right now);
2. Unfortunately a late-night, bourbon-influenced troll through these Forums led me to the following post concerning fabrication of new panel overlays (viewtopic.php?f=24&t=11751&hilit=panel+overlay) and I think we've been bitten by that bug, too. With the new drill press and a new router (did I mention that I also bought a hand-held router, too?) I'll start creating a wooden MDF form for the main overlay panel and the two smaller overlays surrounding the yoke shafts. I haven't placed any phone calls to see who can do the vacu-forming but I'm anticipating that shouldn't be a problem. Also, I have this crazy notion that I could 3d print new bezels on my 3d printer and with the proper priming, sanding and finishing come up with something that looks reasonably pleasing to the eye;
3. Still need to do the flying I mentioned earlier in the post. Over the extended Labor Day weekend, with a negative Covid19 test in hand, I felt safe enough to hop in the plane and fly the 1,500nm round-trip from Atlanta to southern Minnesota to visit my dad. With my mother in a nursing home (Alzheimer's) and my father just hitting 80, neither my wife nor I wanted to chance ANY travel - especially commercial - to see them out of the fear of inadvertently carrying something into their household. This was a wonderful trip made possible by a lovely, seventy-year-old airplane that I am head-over-heels in love with. More on that trip in a separate post. But I digress: we still need to fly some more, and we have the itch to go somewhere. Anywhere.
4. Once the yokes come out we need to do the soak-overnight-in-stripper technique suggested earlier in the thread and can hit them with a few new coats of paint and clear coat.
6. Oh, and if the yokes are out, maybe - just maybe -should we replace the plexiglass overlay in the center panel? I hear that a table-top laser cutter would make quick work out of the cutting and reverse-engraving. My wife has been talking about getting one over the past year (she's a costume designer and does a lot of intricate work with expensive leather and other fabrics) and - just maybe - we could come to some type of arrangement?
6. And, finally, I'm carefully formulating an answer to my wife's question, "how much has it cost us thus far to drill a hole in a $3.58 plastic ball? Would it have been cheaper to buy it from Aircraft Spruce?" My initial answer of "you can't buy them anymore" at first seemed sufficient - helped by a suggestion that we're getting a few new tools that she can play with - but upon further reflection I fear that this may be yet another dark, expensive hole that we are going down ...

(In all fairness, and to avoid any possible misunderstandings: it's my wife who possesses the majority of the mechanical and artistic aptitude in the family and she plays an equal role in this wonderful experiment)

More to come -
Last edited by brian.olson on Mon Oct 05, 2020 1:59 pm, edited 3 times in total.
Brian
1950 170A
N5762C s/n 19716
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4583C
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Re: Yoke and Yoke Shaft Refinishing

Post by 4583C »

Good job on that jig! 8) Drilling holes on round stuff is always a challenge for me.
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GAHorn
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Re: Yoke and Yoke Shaft Refinishing

Post by GAHorn »

Great Post, Brian! Submit it to headquarters for the 10 News!

The Teflon balls are no longer produced so “Owner Produced Parts” is the answer, IMO. I wonder if McMaster-Carr could provide better quality assurances... Specific Gravity testing using clean water (thank you Archimedes) should tell if a ball has voids in it before drilling. (Or, a sensitive scale and comparative weighing of the balls might suffice.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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Stankasica
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Re: Yoke and Yoke Shaft Refinishing

Post by Stankasica »

Brian, If you decide to make the center panel plastic overlay I would buy one and help offset the cost.

Stan
Stan Kasica N2458D
KSNC. Chester,Ct
hilltop170
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Re: Yoke and Yoke Shaft Refinishing

Post by hilltop170 »

Here is another source of Delrin balls that might be of better quality than McMaster.

Plasticballs.com has many different materials available but Delrin looked best to me.

Click on the pictures to enlarge.
Delrin ball supplier
Delrin ball supplier
Sizes and specs
Sizes and specs
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
User avatar
DuaneShockey
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Re: Yoke and Yoke Shaft Refinishing

Post by DuaneShockey »

Brian, Back in 1988 when I did my yokes, I did powder coat black on he handles and auto chrome shop job on the shafts. I wanted to be legal on attaching them together so I ordered the long rivets from Cessna at $22 each. So $88 spent. The did not seem like anything special but I never did try to see if any rivets that size could be found at an aircraft supply dealer. I'm told that the FAA would not like to see bolts and nuts. DuaneShockey
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GAHorn
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Re: Yoke and Yoke Shaft Refinishing

Post by GAHorn »

DuaneShockey wrote:Brian, Back in 1988 when I did my yokes, I did powder coat black on he handles and auto chrome shop job on the shafts. I wanted to be legal on attaching them together so I ordered the long rivets from Cessna at $22 each. So $88 spent. The did not seem like anything special but I never did try to see if any rivets that size could be found at an aircraft supply dealer. I'm told that the FAA would not like to see bolts and nuts. DuaneShockey
“the FAA” is not a single person with a single opinion, and there are lots of threaded fasteners (nuts and bolts) which are suitable replacements for rivets in this type application. (And the last time someone reported Cessna’s price for those rivets hovered around $100+ for EACH.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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brian.olson
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Re: Yoke and Yoke Shaft Refinishing

Post by brian.olson »

Update on our panel progress:

Unfortunately due to this and that (and a bunch of other excuses) I haven't made any substantial progress on the panel overlay. However, I do have an update on the yokes.

I made the decision to replace the yoke universal joints this past week due to a concern over the amount of "slop" in the yokes. Not bad, mind you, but perhaps 1/4" (and maybe a little more) left and right. A review of the logbooks failed to find reference when they had ever been replaced which added to my concern over a potential future failure. I stopped by Aircraft Spruce and ordered the kit (joints + hardware) this past Thursday and they should be arriving on Monday of this coming week.

In the meantime, I pulled the yokes and decided it was time to strip and paint the yokes and then finish polishing/restoring the yoke shafts as well.

BTW - all of the following was in consultation with my A&P who had confidence in me performing the work, and will be reviewing it upon completion and signing off on the logbooks.

I pulled the yokes on Friday and then early today pulled the wooden yoke bearings and the support brackets from the panel. There was a substantial amount of caked on crud on and in the bearing as well as on the inner surface of the brackets - which explains why the yokes were "grabbing" (no amount of dry lube made any measurable difference). Note that last October (and earlier in this thread) I fabricated replacement bearings out of Delrin balls so that I would be ready for this moment.

Friday afternoon I took 62C's cigarette lighter to one of the local custom auto paint stores to try to match the color of the Cessna red "clay" color, which was the original yoke color when the plane left the factory. Unfortunately the lighter was too small for their scanner, so I perused their many color sample books and found a color match that was almost an exact match. I left the store with some epoxy primer, the color coat, and clear coat.

Here is the "before" photo of the yoke. You can see the amount of paint that has chipped off over time. You can also note that faint specks of the original "clay" were coming through. As best I can tell, the yoke left the factory with the clay color and had been repainted twice with different versions of black.
IMG_6873.JPG
I used just a few ounces out of a one-gallon container of stripper to successfully remove the paint down to the aluminum. This process took me a couple hours from start to finish. After this photo was taken I spent a little more time with some fine-tuning, freshening the surface with 220-grit sandpaper, and then cleaning.
IMG_6876.JPG
Two coats of an epoxy primer were applied and then three coats of the color coat were applied per manufacturer's instructions. You can see the close match of the colors between the new color and the cigarette lighter. It's not exact, but in my opinion a good approximation taking into account the seventy years of fading that has gone on.
IMG_6889.JPG
For future reference, the color was custom blended by the auto shop and is available as "GM Spiced Red".

I still have the vinyl graphics I had custom-ordered last October but after further reflection decided I did not want them in white. While the third color coat was curing I fired up the vinyl cutter and printed two copies of the Cessna logo (I supplied a copy of it earlier in the thread) and cut it out of a tan vinyl that matched the interior "sand" color we selected when we remodeled the interior a couple years ago. I applied the logo - carefully as I didn't want to screw up this important step. In hindsight, I'm glad I chose to use the tan copy and it looks significantly more pleasing.
IMG_6891.JPG
IMG_6893.JPG
Shortly thereafter, I applied three coats of clear coat to the yokes. They will be curing overnight in the garage. I am really loving the new color of the yokes and can't wait to see them in the plane. When I finally get around to making the new panel overlays I think I'll paint them the red color as well.

Tomorrow, I'll pull the throttle knob and paint that as well. I'll then re-polish the yoke shafts to remove some surface rust and staining as well as fine-tune the fit of the Delrin bearings, which I'll fit into the panel with the support brackets. When the new universal joints arrive on Monday I'll be able to button up this portion of the project and - with a quick sign-off from the A&P - be back in the air soon.

Still have my sights on the new overlay ... so stay tuned for more.
Brian
1950 170A
N5762C s/n 19716
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GAHorn
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Re: Yoke and Yoke Shaft Refinishing

Post by GAHorn »

OK, Brian.. NOW YOU’VE DONE IT!

Now that you’ve displayed your capabilities... You are now going to have to offer those Cessna logos/bird to the rest of us. I have a ‘62 Skyhawk that needs one of those about 3” wide and 1” tall. :twisted:

(I’m actually looking to “dress up” that Skyhawk a bit with something for its glovebox and was looking around the ‘net and found :
https://www.stickermule.com/uses/custom ... x0EALw_wcB
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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brian.olson
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Re: Yoke and Yoke Shaft Refinishing

Post by brian.olson »

George - last fall, when I was trying to find a source to print the vinyl stickers, I actually looked at that vendor as an option. There are a number of sites like that - all super-easy to use: just upload an image, play with the size, choose a color, and hit "order". Most of the sites had a minimum sticker size of 2" but unfortunately I needed one that measured exactly 1.25" horizontally. I finally found and used a company called "stickylife.com" which allowed a minimum size of 1.25" and had ten of the white stickers printed for somewhere between twenty and thirty bucks total, pretty reasonable all things considered, and they did a great job. I wouldn't hesitate to use one of those sites again in the future, the quality is excellent.

It was only after I had received the completed order that my wife and I decided to purchase a vinyl cutter (funny story here: based on a possible need for more graphics for the plane, and some for a new camper we had ordered, I went ahead an bought a vinyl cutter. When my wife came home from work that evening, she said "oh, I see we decided to buy a vinyl cutter". So from that perspective, I like to think that it was more or less a joint decision). I've messed up more stickers than I've had success with, but I hope that with more practice and experience I can improve the ratio a little. Most of my water bottles and one coffee cup have practice "170" logos all over them. I'm surprise the cats don't have them stuck to their fur.

Getting to the point of this, however: I'm happy to help you with a graphic. Your guidance and feedback over the past couple of years has been most appreciated, and it would be my pleasure to help you out to the best of my abilities. Note that the cutter does not like to do anything small nor extremely detailed (my logo was about as fine as I could go before the cuts wouldn't separate cleanly and I started unleashing a torrent of colorful phrases that will never appear in a children's book) - but it does great with that size and larger, up to about 12" square, which is the size of a standard vinyl sheet. Send me a PM with your email address, I'll respond and you can send over an image and detail of what you are thinking.
Brian
1950 170A
N5762C s/n 19716
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