Scott 3200 Tailwheel Spindle Failure

[jrenwick]

TIC170A member Dennis Hoffman asked me to post about an incident that happened to him last weekend. Fortunately it happened on the ground at our home airport, just as he began to taxi out of parking, and there was plenty of help around to get the airplane back to his hangar. He had spare parts available to get the problem fixed the same afternoon.

The failure was in the spindle part of the Scott 3200 Bracket Assembly:

Bracket_Assembly.JPG

The spindle cracked in half, which allowed most of the tailwheel to become detached from the airplane:

IMG_2059.JPG

IMG_2062.JPG

This part has a grease fitting on the wide end, which has been removed. It's drilled axially down from the fitting, and transversely where the crack occurred. It also had a groove machined around its circumference, to help distribute grease to the working parts located between the bracked assembly and the fork:

IMG_2064.JPG

The transverse passage and the circumferential groove seem to have created a weak area in the spindle where the crack occurred. Dennis noticed that the spare part he had did not have the groove, and the transverse passage was smaller in diameter than on the part that broke. We guessed that his replacement part might have been a later revision than the one that broke, engineered to prevent this problem.

This might be something to be sure to inspect the next time you disassemble your tailwheel.

Best Regards,

John

[parksjm]

RE: This happened to me about 20 years ago (3100TT). Luckily I was just pulling the plane out of the hanger. I called the Scott Co., as they were not far away, & they were very defensive about it. They told me that my tailwheel was an old design which was defective & the new one did not have a hole thru the spindle halfway from the end. I ended up buying a new upper assembly from Univair (#045-3216).

[Brad Brady]

Yep.....That's where they always break....Dad left here in '82 for Oskash and landed there without a tail wheel. I found it on the airstrip where he broke ground.......Brad

[johneeb]

John, did Dennis have a spare "Spindle bolt" and if so where did he get it? I have tailwheel assembly that suffered the same fate and would like to rebuild it for a spare however the parts drawings do delineate the "Spindle bolt" as a separate part.

[Bruce Fenstermacher]

John,

The spindle is not suppose to be removable from the upper casting. It is a press fit. That is why there is no part number for just the spindle I'll bet.

[jrenwick]

Bruce is right, it's not a separate part. It is pressed into an aluminum assembly. Dennis had a spare bracket assembly in which the casting was cracked and unuseable, so he pressed the spindle out of one and into the other. You just need a small hydraulic press like they sell at the Chinese tool store. (E.g. http://www.harborfreight.com/cpi/ctaf/d ... mber=33497.)

John

[johneeb]

John and Bruce,
I have the press all I need is cracked upper casting that I can press the Spindle out of.

[jrenwick]

John and Bruce,
I have the press all I need is cracked upper casting that I can press the Spindle out of.

Yeah, I guess I should have just said you have to buy a whole new bracket assembly....

John

[johneeb]

John,
Maybe there is a market for rebuiding these upper castings, in this string we have heard of three that all broke the same way and could be repaired by pressing in a new spindle. Of course the economics would not work out if the lower part of the swivel, fork and wheel were not recovered.

[jrenwick]

John,
Maybe there is a market for rebuiding these upper castings, in this string we have heard of three that all broke the same way and could be repaired by pressing in a new spindle. Of course the economics would not work out if the lower part of the swivel, fork and wheel were not recovered.

Of course, you'd have to have a source of the spindles, and Scott doesn't sell them except as part of a new bracket assembly.

Also, it sounds to me as if the spindles that break are old ones, and the new ones you get today aren't subject to this failure. Hopefully it's a vanishing problem.

John