Tail Wheel Fork Repair

blueldr · Post by **blueldr** » Fri Apr 23, 2004 3:04 am

Can anyone tell me a method to remove and replace the steel pin in the Scott 3200 tailwheel fork. This is the pin that precludes rotation of the bronze washer on the aluminum casting of the forks rotating surface.

Post by **GAHorn** » Fri Apr 23, 2004 6:03 pm

Dick, are you referring to pn 3257, item 21 in the exploded Scott dwg? (The pin which locates the pawl spring?) This pin can be removed with a pin vise, or with vise grips clamped onto it and tapped/twisted. Mildly heating the forks can assist. (less than 250 F in the oven).

zero.one.victor · Post by **zero.one.victor** » Fri Apr 23, 2004 6:25 pm

George,I've had that pin out that you describe. As I recall,I drifted out the bushing that's in the fork that accepts the "kingpin",then I drifted the pin inward to free it. Reassembled in reverse.
I think Dick is talking about another pin that is vertical (not horizontal like the above pin), it keeps the "bronze washer" (thrust washer) and I believe the pawl itself aligned with the fork. I think Dick is referring to item # 27 : "pin", p/n 3226.
It's been quite a while since I had mine all apart, I can't recall just how all that stuff fits together in there. Dick,is there a way to drift the pin out from below?

Eric

N1478D · Post by **N1478D** » Fri Apr 23, 2004 7:13 pm

Don't remember seeing a way to drive the vertical pin out. There's not much sticking up to grab onto either, that would be a tough one to remove. You might have to use an easy out if you had a replacement.

Dave Clark · Post by **Dave Clark** » Fri Apr 23, 2004 7:28 pm

I've got the same problem as it's getting bad. I'm thinking it might be possible to drill and tap into it to put a #4 or 6 Machine screw in then grab that. Most probably you wouldn't get that far... it would come out with the tap. heating to 250 degrees would help a lot. Keep me posted.

Indopilot · Post by **Indopilot** » Fri Apr 23, 2004 11:54 pm

Another way I have heard about is to drill through the pin so a 1/8th pin punch can slid through, fill the hole with thick grease, then use the pin punch as a piston. When you tap on the punch the hydralic pressure of the grease being forced into the cavity under the pin will push it out. Will probablyget a chance to try this again, have a Cub around that is about due to replace the pin. Helps to have the new pin so you know how far you will have to drill to get through the old one.

blueldr · Post by **blueldr** » Sat Apr 24, 2004 4:24 am

Eric, you're correct. My problem pin is the vertical pin,about 1/4" in diameter, that keeps the bronze washer from rotating on the fork. There is not enough material above the surface to grip it with any kind of a tool to pull it out.
I believe I'll try to drill through the fork casting from the back side and try to knock it out with a pin punch. I'll probably have to start with an end cutter to get a flat surface to start the drill bit alligned with the pin. The fork casting has a lot of angle behind the pin location.
George, I hope you wont loose a lot of sleep over it, but $21 for a tie down ring seems better spent on beer, what with summer coming on. I have, again, welded the ring off of a $2 ring bolt on the spring mounting bolt. I drink a pretty cheap brand of beer, so $19 goes pretty far!

zero.one.victor · Post by **zero.one.victor** » Sat Apr 24, 2004 6:19 am

Dick,that type of ringbolt has occurred to me moe than once,but I didn't want to risk a chewing-out by bringing it up.

Seriously though,--does the AN7-20 bolt that holds the t/w assembly on have some kind of heat-treating that would be affected by the welding?

Eric

Post by **GAHorn** » Sat Apr 24, 2004 7:39 am

According to the resident aeronautical engineer, Cleo Bickford, AN hardware is heat treated. That's the problem with simply welding a ring onto a bolt. (That bolt is already under considerable stress, and if it lets go, it does the well-known damage to the rudder.)

R COLLINS · Post by **R COLLINS** » Sun Apr 25, 2004 1:36 am

George how is the ring attached to the store bought variety? Would welding a ring on a thick washer and placing it under the AN bolt head be sufficient? Would probably have to get a longer bolt though.

Dave Clark · Post by **Dave Clark** » Sun Apr 25, 2004 3:46 pm

As a substitute you might make a fitting from an angle iron similar to the tow lug fittings and use that in place of the washer.

Post by **GAHorn** » Mon Apr 26, 2004 5:09 pm

The common opinion is that the ring is welded onto the bolt head, then the part is re-heat treated and cadmium plated.
The washer/ring and bracket idea sort of solutions are exactly the type that are frequently discussed in this matter. The problem is the level of approval one needs to satisfy your IA.
The installation of a genuine, purpose-mfr'd Cessna part onto an identical tailwheel landing gear of an airplane of lesser gross weight is viewed as a "minor" alteration requiring only a logbook entry and sign off.
Is the installation of a homemade product, not previously approved for use on any airplane a concern for your mechanic/inspector? Or do you intend to obtain field approval or STC for it?