Yokes & Control Rod Help

[M Towsley]

Ever since picking up 'Scarlett' I wanted to put a set of pretzel yokes in her like I had in my original BC-12D.

John at Skyport Services is assisting me in doing so and asked that I pull the current yokes and rods out to see how everything was attached and what kind of mounting holes were present. My late, late model yokes were bolted on and i know the pretzel yokes utilize a tapered drive pin.

I think my current control rods have been sawn off already as the yokes were resting up against the instrument panel. One is 17 13/16" long and the other 17 5/8" long. (One also has some rusting so I would like to replace them).

-Does anyone have a stock one around to measure or know the stock length?

-These are 3/4" diameter rods, does anyone have a recommended source for this material? This appears chromed, does it come that way or do you have it chromed? (I believe Rob Lees utilized polished stainless??)

Thanks for any help you can provide!

[Larry Lyons]

Re: Yokes & Control Rod Help

My 41 BC-12 has 18 1/4" over all length tubes. 18" to the face of the mounting plate. 17" from plate face to bolt hole center. My banjo yokes are mounted with three 1/4" cap screws through the plate and in to the yoke. On mine the plating was wore almost completely off so I had them replated. If you go replated make sure it is a good plating company as you need the under plating of copper and I believe brass to make the chrome stick and not peel off after just a few years. Larry

[M Towsley]

Re: Yokes & Control Rod Help

Larry,

Thanks for the reply. My control shafts are just that, tubing with no plates. Do yours have some kind of plate the yoke mounts to? Mine are just rods, nothing else.

I am going to have to replace these as one isn't bad but the other has rust. I would like to use polished stainless like Rob Lees did if I can find a source.

[Hank Jarrett]

Re: Yokes & Control Rod Help

What you want is STRUCTURAL Chrome, NOT "flash" or decorative Chrome. To do it right they will put the Chrome on much thicker and then grind it back down on a centerless grinder. They also did a lot of Nickel plate before the war and the control shafts and the trim handle on both my 41 and 45 were originally Nickel plated, not Chrome. It looks a lot like Chrome but has a slightly "duller" shine and Nickel is softer and wears.

I didn't re-plate the shafts on the 41 after the shock of the cost for the 45. I will do it when I do the recover sometime in the future. I also did NOT use Nickel on the 45 shafts, I used Chrome. The original plating was worn through in large areas and Nickel just isn't tough enough for a running surface, even one that rubs as little as a control shaft on phenolic bushings.

I am pretty sure you can have them grind the surface to a slightly rougher RMS and make the Chrome look more like Nickel, but so few people could even see the difference between a Chrome and a Nickel trim handle I didn't bother.


You don't actually need Brass to plate Chrome on steel. You use Copper on steel to fill in damage and then repair the running surface with Nickel-Tungsten in a select plate process but it is functional, not cosmetic. It looks like a coffee stain on the surface. We used it a lot to repair damaged pistons on navy landing gear that had been damaged from impact (usually a tie down chain hitting the piston and spider web cracking the chrome). When you put Chrome or Nickel over Aluminum you need to plate it with Brass prior to Chrome. You can't get Chrome to stick well directly to aluminum.

Now for the IMPORTANT PART! If you don't care a whit for all of the above, READ THIS!!!

YOU MUST HYDROGEN EMBRITTILEMENT RELIEVE THE STEEL SHAFT AFTER PLATING IT!! Electroplating steel forces Hydrogen into the steel that pushes the grain of the steel apart and cracks it. Lots of "Bumper Plating" shops will try to tell you you don't need it. RUN AWAY! Bumpers are made from some of the crappiest mild steel known to man. The steel tube in your control wheel is 4130 and the fastener holes will crack if you don't relieve it.

It isn't hard to do, but the times ARE CRITICAL. The plated shafts have to be put in an oven at 375*F plus or minus 25* withing 20 minutes of removal from the plating solution (that 20 min INCLUDES the rinse time!) Bake it for 23 hours minimum then let it cool before you touch it. It won't crack if you touch it, but it's hard to get the fried skin off the Chrome and it takes a while to cool off.


If you don't want to be incredibly frustrated make sure the plating shop knows you will be putting fasteners through the cross holes and the ends of the shafts. The plating will make the holes smaller and if you drill out the holes you will damage the Chrome and it will slowly peel of as corrosion runs under the Chrome. They can mask the holes to stop that, just remember to seal the bare steel with primer and paint when you assemble the controls. It might be a good idea to clean the ID of the tubes with a rifle or shot gun wire brush and slosh them with primer, then paint. The wet assembly of the parts will make it REALLY hard to take apart the next time so make sure you don't need to take it apart again.


If you don't mind redoing the Chrome ever couple of decades the decorative Chrome would probably work pretty good and for the cost it might be cheaper to use decorative plating rather than ground plating in the long run, but I tend to get anal since I was a plating engineer many years ago.


I am NOT being anal about the embrittlement relief. We had an F-14 piston the came out of the plate solution right at break time. They didn't get to the oven in time and the piston split up it's length. It sounded like a 12 Gauge shot gun going off and soiled a lot of underwear. The F-14 used a MUCH higher strength steel and was a LOT bigger in diameter and thickness so it was even more critical, but it sure made the workers take the time limits seriously. Damned thing jumped right off the bull dog wagon when it let loose. When a tube the size of ours breaks it usually makes a loud PLINK! like a stemmed wine glass breaking.


Hank

[rammon3]

Re: Yokes & Control Rod Help

I totally agree with Hank on his assessment. (I, too have some experience with plating.) We would typically increase hole sizes by 1 drill size in order to get the correct final size hole after plating. That won't necessarilly work in this case. It depends on the plating thickness. Hank, do you know how thick the plating is before grinding?

[M Towsley]

Re: Yokes & Control Rod Help

Ok, now you both have me scared because this sounds like I am going to have to trust someone I don't know to do it right.

What about the polished stainelss idea???? I still need a set of control shafts or at least their correct length, etc., one or the other...

[Larry Lyons]

Re: Yokes & Control Rod Help

Yep Hank is right, mine did not get the stress relief, however they are hanging in my shop and will for several years yet before use. So if they want to crack, they can, but having plated the old style flat plate shock absorbers many many moons ago with no problems I will take this gamble, as the yoke will never see more then the strain I can push or pull. However, as to the hole shrinkage, you bet. My banjos have all the little spokes and everyone had to be reamed to be reassembled. The bolt holes were large enough to not bother. Still looking for that errant yoke hub cap though!!!!!
Larry

[NY86]

Re: Yokes & Control Rod Help

If you don't want to be incredibly frustrated make sure the plating shop knows you will be putting fasteners through the cross holes and the ends of the shafts. The plating will make the holes smaller and if you drill out the holes you will damage the Chrome and it will slowly peel of as corrosion runs under the Chrome. They can mask the holes to stop that, just remember to seal the bare steel with primer and paint when you assemble the controls.

Part of the process when installing the taper pins is to ream the holes in the two parts to match. Plus, it's tapered, so the two holes (sides) are not the same size. I suppose you could mask them off a little over sized so the reaming didn't get into the plating. More likely, though, at least in this case, the plating will happen before the holes are drilled. Maybe that's why the originals were nickle ???

[Hank Jarrett]

Re: Yokes & Control Rod Help

First, sorry to drop off line. I was in the middle of responding when my computer had a MAJOR crash. I have to make a recommendation concerning that. Don’t skip the message, the next part is back to plate problems but I have Avast antivirus (which has always worked great) but I got nailed by a brand new malware. I called the Avast help number and got the best computer support I have ever had. It was out of India, but all of the people actually spoke English that was understandable and they used testing to resolve the problem. Turns out I had antivirus protection (computer was totally clean of any virus) but I did NOT have anything for spyware, Trojans, or a list of other nasties. Avast has FREE products for home use and they WORK. The support does cost but they will help you set up ANYTHING on your computer. It was GREAT and they cleaned my whole computer up over 3 hours with a significant speed-up. Anyway, back to plating and if you need computer security software check out Avast.

Roscoe
Plating thickness is related to current density, time in the solution, voltage potential, anode proximity…… Plating is still as much black art as science. Slight set-up mistake and you can get ¼” to 3/8” “Christmas Trees” of all the corners of the base material. If the anode is right and the power is set correct you can pretty much get whatever thickness you want, but it is a real art.

Marty,
I would NOT use polished stainless for the shaft. Stainless is a lot weaker in bending than 4130 unless you are going for something a LOT more expensive than I think you have access to. It is also VERY illegal to start substituting materials, ESPECIALLY in the control system or primary structure load paths. Don’t do it. If you get caught you will have a BIG lawn ornament because the feds will want proof you haven’t done it on other parts. There ARE good plating shops around, just ask about their process and watch for the guy with a bathtub and a car battery. ;-)

Larry,
Inspect them REALLY CAREFULLY! Look around all of the holes. Steel WILL naturally loose the Hydrogen over long times. If it doesn’t crack early, the longer it sits the more Hydrogen will come out and the less likely it ever will. I have NO idea if enough has “gassed off” since this is something we NEVER did, but I know there were “loot jobs” that didn’t make the oven and didn’t crack (we caught one guy who Chrome plated a whole Schwinn one part at a time. Wonder if he is out yet? They let him finish the whole bike before they arrested him. No idea if baking it years later would help.
One thing to remember is that those shafts WILL see high loads in an “arrival”. We found the control stick in an A-6 that was BENT by the pilot. We also found the throttle still in his hand, unfortunately his hand wasn’t on his arm any more. You would be amazed how strong you get when you are looking at Cumulo-granitus close up.

Be careful with plating guys, especially on load bearing parts.

Hank

[M Towsley]

Re: Yokes & Control Rod Help

Hank,

As always, thanks for the tips.

That puts me back to my main problem, I need a set of control shafts or figure out how to make new ones. What is the bottom line, anyone????

[Forrest Barber]

Re: Yokes & Control Rod Help

What do you need , I think you want straight shafts ; they are 17 13/16th end to end ??? OR do you need the pretzel wheels and shafts ??
e-mail back direct

[M Towsley]

Re: Yokes & Control Rod Help

I would like pretzel wheels and shafts. If you don't have that I could use just the shafts. I will also e-mail you with some other wants. Thanks, Forrest.