Tailspring bolt

[jimboflying]

What causes tailspring bolts to break?
Attachment 66731

[stewartb]

When the leaves flex the bolt holes must shift and try to tilt the bolt. It can only take that for so long.

[guanaco]

fatigue

[bob turner]

Surprising that it doesn't happen more often. I had a leftover MS bolt (167,000 psi) and installed that. Be a while before it breaks.

[sixmile]

tried one of those solid robber tires for tailwheel every small rock would vibrate the fuselage feel it in the pedals. didn't take more than a few landings to change back. probably wouldn't be long for bolts to break

[stewartb]

I have a single bolt head on my shelf. Have for 15 years. I have a 2-bolt head on the airplane.

[jrussl]

My opinion…..it is from the side to side loading on the tail spring when the tailwheel is out to either side. I broke one a few years ago and it had fatigue cracks initiated from both sides of the bolt. The above bolt picture shows similar fatigue cracks. It was clearly loaded in bending and I can only see that happening from twisting loads. Twisting loads on such a narrow spring create some large bending loads on the bolt. I now replace all gear, bolts including tailwheel bolts, every two years.

[jrussl]

January 20th, 2018. I was very lucky as the spring strap kept the tailwheel from contacting the rudder and a friend was carrying a spare bolt. Replaced it out on the ice that day.

[BC12D-4-85]

I'd try to see if the bolt is shearing at the threads or at the soild shank portion. Then find a way to reduce the failure if at the threads. A&P's might know and I'd ask.

Gary

[bob turner]

I have only had one break - in six thousand hours. Mostly solid tailwheels. Last quarter century it is 90% touch and goes, lots of student work. But no rough terrain.

[akavidflyer]

I'd try to see if the bolt is shearing at the threads or at the soild shank portion. Then find a way to reduce the failure if at the threads. A&P's might know and I'd ask.

Gary

Both of the pictures show it breaking at the threads. The OP looks like it was cracked for some time, on 2 sides and it finally gave it up. As was previously mentioned, might consider it a wear item and replace every annual, or couple of annuals if you are beating it hard. Small tail wheels and solid rubber types are BRUTAL on an airframe.

[cubdrvr]

They do take a beating. Mine is also 2 bolt, but check yearly and change when needed.

[BC12D-4-85]

I'll ask this....would a longer bolt with washers that avoids contact stress on the threads work better? Or is stress/breakage regardless of bolt length inevitable?

Gary

[texmex]

From memory, somewhere on SuperCub.org, the recommendation from Steve Pierce was to change them out annually on the Cub. Preventative maintenance.

Having typed that, I'm wondering why I don't change them out on the C180.

Edit: Disregard the last line (it's very early here). I realise the hub is actually epoxied on and the two bolts are totally different.

[tempdoug]

https://www.supercub.org/forum/showt...el+bolt+breaks

[tempdoug]

dont know what size your bolt is but dont some change from a an7 to a an8??

[jrussl]

My bolt is from the tail spring to the airframe and I think the OP’s bolt is as well. No option for two bolts or a larger bolt without welding in a different cross piece.


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[BC12D-4-85]

https://www.supercub.org/forum/showt...el+bolt+breaks

Painful but worth it, I need air. Worth a read. I liked #107, 136, and 172.

Gary

[hotrod180]

My bolt is from the tail spring to the airframe and I think the OP’s bolt is as well. No option for two bolts or a larger bolt without welding in a different cross piece.

I assumed the bolt being discussed was the one holding the tailwheel head to the spring.

I cut off the bottom leaf even with the second leaf on my old C150TD,
and bolted the t/w through 2 leafs, just like a supercub, to get more AOA on the ground.
It got me that, but I ended up replacing the bolt a couple times due to it being deformed.
Bolting through 2 spring leafs doesn't seem like a good idea,
given the fact that the two leafs are flexing & working somewhat independently.
IMHO a better idea would be to bolt it through a single, heavier-duty leaf.

[stewartb]

If the airframe bolt is breaking the spring clamp a few inches in front of it must be allowing movement. I checked mine and it was loose. Those bolts take a beating, too.

[mit greb]

I think almost everything is caused by global warming now!

[Chip D]

I check the tightness as part of my prefilght. I think once it is loose it shears the bolt off.

[BC12D-4-85]

One of my preflight moves is to unload the assembly by slightly lifting and dropping the tail wheel. Looking for any looseness and movement between parts, and listening for clunks. Up, down, and sideways. Not perfect but better than an eyeball walk-by.

Gary

[frequent_flyer]

One of my preflight moves is to unload the assembly by slightly lifting and dropping the tail wheel. Looking for any looseness and movement between parts, and listening for clunks. Up, down, and sideways. Not perfect but better than an eyeball walk-by.

I have found rocking the tail side to side is a good way of checking the tail spring attachment to the fuselage. I have used that technique on most of the different tailwheel types I have flown.

[Richgj3]

Timely thread. Mine on the C170 broke last night. I have no idea how old it is. Ordered new parts today, including the bushing. It is shot too. The color is off because of the lighting.

[BC12D-4-85]

^^^^Threads disappeared with the fastener and washer. Lots of us up here are paying attention now to this advice. I put new in mine last year.

Gary

[hotrod180]

Timely thread. Mine on the C170 broke last night. I have no idea how old it is. Ordered new parts today, including the bushing. It is shot too. The color is off because of the lighting.

Interesting that bolt failed, because the tailwheel bolts through a single leaf on a 170.
More common is the main leaf breaking right at the end of the second leaf,
maybe due to the edge of the second leaf wearing a groove in the main spring.
Hopefully you didn't have the tailwheel flail around & beat up the rudder--
you'll see a lot of 170's with a repair at the bottom of the rudder because of this happening.

[Richgj3]

Interesting that bolt failed, because the tailwheel bolts through a single leaf on a 170.
More common is the main leaf breaking right at the end of the second leaf,
maybe due to the edge of the second leaf wearing a groove in the main spring.
Hopefully you didn't have the tailwheel flail around & beat up the rudder--
you'll see a lot of 170's with a repair at the bottom of the rudder because of this happening.

I got lucky. Just the tiniest of tiny dings on the bottom of the rudder. Already polished out. I admit I never paid any attention to that bolt. I got the airplane three years ago and have no idea how old it was. Nothing in the logs. This is the third airplane I have owned with the Scott 3200 tail when and never even thought this could happen. Thanks to this thread I know it can and why.

I had a 58 172 with the Ralph Bolen TW STC. I had it for seven years or so with no issues with the same 3200 TW. I had no indication how old that bolt was. Then I had a Great Lakes 2T1A-2 with the same 3200 tailwheel. Probably on there since new in the mid seventies. No indication in the logs about replacement although the entire airplane was rebuilt by Jim Kimball in the 90’s.

Guess I just got lucky. You can be sure I’ll pay more attention now.

Rich

[JP]

Saw a guy leave a 3200 behind once. He wondered why the airplane steered poorly when he landed. Bolt broke on takeoff or landing. We stole another 3200 to complete the fly in weekend and rebuilt the broken 3200. Oh, well.

[Bill.Brine]

Saw a guy leave a 3200 behind once. He wondered why the airplane steered poorly when he landed. Bolt broke on takeoff or landing. We stole another 3200 to complete the fly in weekend and rebuilt the broken 3200. Oh, well.

Was that at Plymouth, NH with a John Meade spare 3200 fix?


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[tedwaltman1]

Now this is a "slightly" deformed front tailspring bolt. From many years ago when the bolt was --very-- loose which I never (shame on me) noticed during pre-flight inspections. Now I have bright orange Torque Seal 83314 on the bolt which I look at very carefully before each flight!

[jimboflying]

Maybe the bolt is actually made for misaligned holes


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[jrussl]

Maybe the bolt is actually made for misaligned holes


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Here are a few more useful bolts.