Control Wheel Shaft Guides

[Axelrod]

Lookig to replace the original phenolic control wheel guides on my '46 T-Craft. Mine are worn out and looking for a replacement part or alternative material to make new ones. Thanks

[Hank Jarrett]

Re: Control Wheel Shaft Guides

You can sometimes get Phenolic sheet from electronics suppliers (the original material). I have gotten it from Kay Gee plastics and Norfolk Plastics in Norfolk Virginia, but it has been quite a while and I don't know if they still have the thicker material. You CAN epoxy the thinner sheets together to make the thicker. A GREAT substitute material is Teflon sheet but it is expensive and I don't know if it is a legal substitute (safe and would work, but sometimes that doesn't carry any weight with the FAA).
I can get you dimensions if you need it.

Hank

[Axelrod]

Re: Control Wheel Shaft Guides

Thanks Hank. Yes get me the dimensions.. I'll check locally with electronics guys....if not I was thinking teflon would be the way to go!

[PA1195]

Re: Control Wheel Shaft Guides

This has been used in similar applications: https://www.amazon.com/Molecular-Wei.../dp/B00CPRDLAW

This is what I have for my wheel shaft guides. Cut to fit the panel and drill a chamfered hole for the shaft.

Also used for aircraft ski bottoms and as sled runners by Santa Claus.

Gary

[woodmw]

Re: Control Wheel Shaft Guides

Aircraft Spruce sells phenolic.

http://www.aircraftspruce.com/catalog/mepages/phenolic.php?clickkey=3021561

[N96337]

Re: Control Wheel Shaft Guides

There was a guy that had an STC to replace the phenolic with teflon, but I tried repeatedly to get ahold of him at the address and got no response. I contacted the FSDO that he was under and they couldn't get ahold of him either. I don't even see the STC listed anymore.
John

[Ragwing nut]

Re: Control Wheel Shaft Guides

I would consider it a minor alteration to use teflon or delrin would be even better, follows form fit function imo. STC is stupid overkill for that part.

[PA1195]

Re: Control Wheel Shaft Guides

There was talk elsewhere regarding the need to sometimes re-chrome control shafts. Why did they de-chrome to begin with? Was it associated with and in the area of the panel guide, or just corrosion randomly getting under the coating?

Gary

[Hank Jarrett]

Re: Control Wheel Shaft Guides

The shafts aren't "de-chromed", they were originally plated with Nickel which is not as hard as chrome and wears off from rubbing on the guides. Remember NO ONE expected these planes to be still flying after 75 years. Many shafts have been re-plated over the years and unless you were in to plating pretty deep most people can't look at plating and tell Nickel from Chrome. Chrome has a mirror finish when polished (just like an old time bumper when new) while new Nickel has a more "dusky" look. Hard to describe but once you notice the difference you will recognize it.
If you are in to originality you will want Nickel. If you want a plating that is actually better for protection and wear, Chrome is the way to go (just don't say anything because Chrome is NOT on the original drawings and some FAA type could get anal and make a stink about you deviating from "factory specs".
One thing to do for sure if you plate a shaft is INSIST that the plating shop Hydrogen Embrittlement Relieve the shaft after plating. You need to bake the shaft for 23 hours at 375*F +-25* and it must go in the oven within 30 minutes of removal from the plating bath. Pretty good chance the shop will raise a stink but this is your primary flight control shaft, not a 62 Buick bumper. Insist!

Hank

[PA1195]

Re: Control Wheel Shaft Guides

Interesting fill Hank and thanks for the historical background. I have some nickel plated firearms and it is a bit different than shiny or dull finish chrome.

Well if the guides wear the plating then I'd opt for something that doesn't do that as much. Phenolic was their choice but likely dependent upon available material in those early years that wasn't metallic. Pulleys and circuit boards are durable for a good reason, especially when populated with electrical components and solder traces. Pulleys will wear cables as well as themselves.

I chose UHMW-PE because it's softer than some materials, is slippery, available, yet resists wear well and is durable across a wide range of temperatures. As far as self lubrication I think that's a debatable term unless impregnated with a something that is an actual lubricant. Teflon or Delrin may be even better but again it's the potential for wear on both control components that's a consideration. If the bottom of skis, boats, or dog sled runners last with UHMW it'll survive in this application.

As far as the FAA I seriously doubt they have the time these days to worry about the composition of Part 91 control shafts or guides, or are even aware of what was there in the 1940's. If my mechanic is satisfied so am I.

Gary

[NC26528]

Re: Control Wheel Shaft Guides

I made one for the pilot side and used phenolic to a good result. The co side I'm going to try Delrin just to see how they compare.

[Mark Bowden]

Re: Control Wheel Shaft Guides

Hi,

We did an extensive testing for replacing glass or fabric reinforced phenolic used in cable guides, rub blocks, etc... As Gary noted UHMWP became the material of choice, performance better in all aspects and cheaper as well as easier to machine. McMaster has it for example. https://www.mcmaster.com/#uhmw-polyethylene/=16r0u3y

For those not familiar with the material it is basically that white "plastic" cutting board material.

Mark

[Hank Jarrett]

Re: Control Wheel Shaft Guides

I think UHMW-PE is probably an even better choice than Teflon. Teflon is expensive and tends to "Cold Flow". Not that it would matter in OUR life times, but some of our planes could very well still be around in a couple of hundred years. I saw someone use actual cheap cutting boards from Wally-Mart or a grocery store and he said it machined pretty well even with hand tools and stood up well. When you make your own you can also tighten up the gaps a bit and mark the shaft hole with the instrument panel in place so the shaft doesn't rub the aluminum instrument panel. There was a LOT of vertical play in the originals so the shaft could "float" up and down as the control wheel was moved back and forth. SOME is needed, but there was too much on my plane. DON'T make the hole too tight on the shaft! It should be "snug" side to side and have some play up and down, but not touch the panel.

I also agree completely with Gary. The only time you would have trouble with the Feds is if you got caught up with a real A-Hole who was POed at you and wanted to cause you problems. He WOULD have the letter of the rules on his side but MY rule is safety before rule compliance and make sure my IA is fully informed of what I am doing (verbally not in writing) and that he agrees it is a good substitution. I would NEVER leave him holding the bag. If an inspector found something on my plane it was MY choice to do it, not his. It is too hard to fine a good IA any more who can work on our planes!

Hank

[PA1195]

Re: Control Wheel Shaft Guides

One caution my mechanic offered was to not lube the contact areas. He wasn't sure about petroleum or silicone based lube compatibility with UHMW-PE. So we don't. The components have been inspected periodically with the agreement that any binding or excess looseness detected in pre-flight will be addressed immediately. I think the control shaft changes angles as the elevators are activated so there has to be adequate vertical clearance at full fore and aft deflections. Other than that it works better than the worn out whatever was there before on both controls.

Gary

[astjp2]

Re: Control Wheel Shaft Guides

I just had a set of shafts redone for Peter last summer, the shaft surface is probably more important than the phenolic. I have sheets of 1/4 phenolic, when you bore the hole, use a flapper wheel to polish the inside surface. Makes a big difference. I think that Peter really noticed how much smoother the movement was. My prewar shafts you could see the bare steel, then the copper, followed by the nickle....and you felt the differences in friction as the shafts moved back and forth.

I have a plating shop that does my stuff, they are not fast but I love the quality. Tim