Thursday, June 23, 2016

VINTAGE WHEELS - How long will they last?

On April 23, 2016, My beloved Taylorcraft turned 70 years old.  Looking at the log books, It has accumulated 4,335 hours total time since new. For its entire life, the airplane has resided with various owners in Central Texas.  I have known of the airplane since the mid 1970's.  And so I am aware that most of the years since, it has been continually hangared.... about half that time in an insulated hangar, about 20% of that time tied down outside on an airport tarmac, and the other 30% of the time in a sheltered open air T-hangar.

I am not absolutely certain that the Shinn wheels are the original ones on my plane, but I have no reason to believe that the wheels on this airplane have ever been changed.... until last annual.  I have no idea how many landings they have had over all these years, but it must be a lot.  And hard landings.... groundloops.... well I am responsible for quite a few since this is the airplane in which I first learned tailwheel flying as a teenager.

So how old are your wheels? Do you know their history?  How many hours or, more importantly, how  many landings have they had?  How close have you been looking at them on your annual inspections?  Or, does your I.A. look at them closely?  How about the wheel bearings?  Have you ever found them worn or with signs they've been chattering or grinding?  And when you replaced those hardened steel bearing races, how did you get them out of their aluminum (or magnesium) boss?  Thinking back, I went a lot of years as a rather inexperienced mechanic in training and it is entirely possible, although I don't recall for sure, that I might have used screwdrivers, hammers, and other less-than-proper tools for the job.

What I am getting at is this.  Our old vintage wheels have likely had a pretty rough life.  If it weren't bad enough that they have probably been subject to poor and corrosive environmental conditions, hard landings, blown tires, side loads (groundloops), numerous cycles of bearing spin-up loads; it is entirely possible that they've been abused by green-mechanics or well-meaning owners.  And that's not to mention they're all subject the natural process of Age-Hardening that occurs over time to cause aluminum (or magnesium) to become brittle with age.

I heard about a Luscombe awhile back that rolled up due to a wheel problem.  Also an Aeronca owned by one of my friends had a wheel let go.  I don't know the cause of the Luscombe issue, but my friend says his wheel had some casting flaws (voids) from which cracks propagated until the eventual failure which occurred on the runway (on landing roll-out I think).  He's had plenty of damage occur and he's lucky he was not hurt himself.

The following are photos of the Left wheel from my Taylorcraft.  Upon removal to re-pack the bearings at my last owner-assisted annual, my good friend and I.A. called me over to take a look.  Lo and behold!!!! He'd found a crack.  The photos show the story.


So to get my plane back into the air, another Taylorcraft owner (My good Friend Greg House) came to my rescue with a used Shinn wheel that he had bought at a fly/flea market or ebay or somewhere.  I received it in the "as removed" condition with absolutely no record of what it came off of, let alone how many hours/landings it had.

So I cleaned 'er up via media blast and set out to inspect, alodine treat, and zinc chromate primer paint the two halves.   Once I got to inspecting it, guess what!?!?!  Well it had some imperfections of its own.  I am unsure whether I am seeing corrosion or casting anomalies.  I am more leaning toward declaring it casting voids.  But either way, these imperfections are cause for concern.  Let us know what you think.

 Have you inspected your Vintage Wheels lately?

Finally - It needs to be said.... This is not just a Taylorcraft / Shinn Wheel issue.  It goes for Aeroncas, Luscombes, Wacos, and all.  Here is a photo recently shared on the Luscombe Facebook page.  The submitter says it is a Cleveland DMB wheel, which is found on many light airplanes.  Don't wait for an AD.  We highly recommend you check your wheels with increasing frequency as time goes on.

Be safe!!! 

And...... Keep the Antiques Flying!

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