Thorp Air Command - T18.net

When I first installed my AP twin fork tail wheel , I did not like the cheap ass bearings that came with the wheel , so I bought the "upgraded" bearings from Spruce and installed them . All seemed well with the World ! During the current annual I decided to remove the entire tail wheel assembly and have the rod , fork and bolster fitting powder coated ...got tired of painting the assembly . When I removed the wheel , one bearing was almost frozen and the other showed indications that is was going to fail also...you could feel the bearings rubbing inside the housing . The thru bolt also showed wear on the same side as the failed bearing and the impending bearing was beginning to show wear on the bolt . I have new bearings and plan to install them in a new wheel . Not sure what caused the bearings to fail , but it might have been operator error ? I did not use a press to install them . Any case the newly installed/powder coated unit should look great ! I'll post pics of the final assembly .

Just because the wheel spins freely does not mean the bearings are OK . >:(

RB

These little bearings are pretty stout, but they do get some tremendous loads put on them. When the wheel is turning at 60mph and you step on that rudder pedal it puts tremendous side loads or "thrust" on these little bearings, this will take em out fairly quickly. Just an opinion, for optimum performance they probably would go the distance if they were tapered rollers..or, just more robust so they would go for a longer period of time.........Mine are not smooth as silk either.....Dan

Yep...I think the "original" bearings that came with the wheel were probably made in a back room along with toaster you have on the counter ! The replacement bearings I got from Spruce came from Japan and float like butter ! You are right about the loads on these bearings Dan . They take a beating ! Based upon what I found during this annual I will pull the wheel every annual and at least "spin" the bearings and look at the thru bolt as to condition . A bearing failure on TO or landing would cause me to ship my pants ! No BOOM , just clean drawers !

RB

On one of your old bearings try this exercise,pull the seal of the side of the bearing,the rubber part and take a look at it. If one would pull the inside seal on both bearings, then you could actually get them greased using the grease zert on the wheel, always wondered why they put a zert in a wheel with the bearings sealed. A shot of good grease would surly increase the life of the little devils if you could grease them from time to time you think?? Dan

Get your bearings at the local bearing store. You can get good Timkens for a fraction of the Spruce price.

_________________
Bob Highley
N711SH
SN 835
KLAL

Rich,

What is the bearing number? In many cases it is possible to get deep groove bearings that have higher load capacities. The other alternative is switching to a sintered bronze or solid aluminum bronze bearing setup. Bronze bearings have been around for many years and people tend to forget that they have been used trouble free for many years on machinery. My first homebuilt aircraft had them on the main wheels and I had no issues with them.

Jim

The bearing number on the Spruce package is KSK 499502H . I have found several sites on line that carry them for way less than Spruce .

RB

Dan: Take a look at that "zerk" fitting . It is not a real zerk fitting . It has no ball and spring in it . Just there to plug the hole . Not sure you could keep grease in there anyway as it would probably bleed out around the axel bolt ?

RB

I guess bottom line is , just because the tail wheel spins freely on an annual does not mean the bearings are OK ? Last annual I lifted the tail and spun the wheel and it showed no signs of bearing problems , that's because it was not under a load and just spinning on the axel bolt . It only takes a few minutes to remove the wheel and hand check the bearings ! Believe me you will know right away if the bearings are bad ! Dan is right , those 2 little bearings take a beating and keep on rolling ! I carry 2 spare bearings in my "Fly away kit " ...just in case . BOOM !

RB

Much discussion about the supplied bearings with Aviation Products tailwheels. I too have not been satisfied with the longevity and noise of the bearings. Thought I'd give a try at Timken taper roller bearings. It takes some machining with a lathe and a hydraulic press. The down side is when the rubber is gone you'll have to machine a new wheel. Bearings are reusable. Just finished the project and haven't been able to test it due to other maintenance issues although the assembly certainly feels smooth and free running. Bearings are a little expensive at $93.00 for the set of two bearings and outer races. Available at a bearing business or online thru Mc-Master Carr.

Timken roller bearing part #A4050
Timken outer race part #A4138

Jim Borg

Should have mentioned that the above is for a 1/2 inch shaft.

Jim Borg

Great idea ! Only if the tire would separate from the rim so you could reuse the rim .

RB