S

Steve Barnes

Well Known Member
After about 500 hours my tail wheel spring bolts are creating bigger holes. Both the one bolt inside the fuselage, and the two bolts holding the tail wheel on. Has anyone had a similar problem and fixed it?

my first idea is to use oversize bolts, however it will weaken the spring.

second idea is to use a brazing process on tail wheel and use existing bolts for safety. concern is heat may weaken spring.
http://www.vansairforce.com/community/images/smilies/mad.gif:mad:
third idea is clean and JB weld and use existing bolts for safety, (tailwheel only)

fourth idea is to use taper pins.

Any thoughts on this?
 
Yes, although not fixed yet.

I noticed this at about 150 hours but only on the two tail wheel bolts. Two local AP's conferred that some certified airplanes glue that joint. There suggestion was to dissassemble, clean, and JB Weld the bolt shafts to take up the space and keep them from working the hole further. I intend to do this soon and will report on if it is a permanent fix.
 
tailwheel spring

thanks JonJay, that idea is sounding better all the time. I'll still explore taper pins, but they may loosen too.
 
I would definitely NOT try brazing it. It will absolutely ruin the heat treatment.

I think the JB weld is probably the best solution to try first. It won't leave any permanent changes if it does not work.

The taper bolts would probably be a good solution also as they can be drawn tight with no clearance and no slop, but since the tailspring is harder than the socket it is mounted into and also the tailwheel weldment, those two pieces may deform again and you will be back in the same place you are now.

Just my thoughts on the subject...
 
Little_Richard said:
I would definitely NOT try brazing it. It will absolutely ruin the heat treatment.

I think the JB weld is probably the best solution to try first. It won't leave any permanent changes if it does not work.

The taper bolts would probably be a good solution also as they can be drawn tight with no clearance and no slop, but since the tailspring is harder than the socket it is mounted into and also the tailwheel weldment, those two pieces may deform again and you will be back in the same place you are now.

Just my thoughts on the subject...
Click to expand...

It is actually the holes in the tailwheel spring that are wearing on mine. The socket and bolts are still in tolerance. That surprised me, but that is the way it is.
 
Ready to fix...

Well, it is conditional time and my tail wheel spring is out of the tail. Indeed, the main bolt of the spring has also worked allowing the spring to twist slightly side to side. No doubt, it will continue to work over time.
This must be a common problem.
Steve - did you ever affect a fix?
 
loose spring

Haven't fixed yet, A machinist friend if mine suggested that we ream holes to tailwheel attachment, and press in roll pins. This remedy will not work inside fuselage, however. I think what I'll do there go with an interferrence fit bolt after I ream it out. He also suggested a metric bolt, because it may only be a small bit bigger. We haven't checked that out yet. Steve
 
Thanks Steve...

I am going the JB Weld route as recommended by a couple AP's. I will let you know how it works out.
 
Fixed, but not with JB weld.

JonJay said:
I am going the JB Weld route as recommended by a couple AP's. I will let you know how it works out.
Click to expand...

Further investigation yielded little hope for the JB weld. The spring to socket tolerance is just too tight. My issue is a rotation, where the spring turns or rotates in the socket, not a loose spring itself.
I was able to press in Close Tolerance Bolts for the two An3's in the tail wheel socket and that took all of the slop away there. A close tolerance 174 in the fuselage took away much of that play as well, but there is still a small amount. I am going to live with it and hopefully it will not work the hole anymore.
There was a thread on here some time ago about a home plating kit. An idea might be to plate an AN4 and build it up beyond what a Close Tolerance bolt is.
Moving on now. Good luck with yours Steve.
 
I had this problem also due to poor workmanship when drilling the hole in the weldment that holds the tailwheel spring. My drilled hole on the bottom of the weldment had some slop and allowed the tailwheel spring to rotate in the socket - my fix:

I had a local machine shop turn a conical washer from 4130 high strength steel. The washer was about .4" thick and the ID bore was a tight fit on the AN 4 bolt. The shoulder of the washer was turned into a cone shape with a 100 degree angle (the same as the angle under the head of a countersink AN screw). I then used a 100 degree countersink as a cutter and cut the 100 degree countersink through the weldment and into the tailspring. The bolt (a slightly longer one than stock, to provide room for the conical washer and to keep the washer on the bolt shoulder) was installed and tightened, and the conical washer was pulled into the countersunk surface (sort of like a valve seating in an angled valve seat).

This whole thing can be done from a 3/4" access hole drilled into the fuse bottom, just below the spring retainer bolt.

I believe that this is a good fix because it actually increases the surface area of contact between all the mechanisms involved. It also pulls the tailspring weldment into tension against this 100 degree seat, while taking out all play. Also you now have some compression holding the assembly together and you are just not relying on the shear of the bolt against the tailwheel weldment to counteract the twist forces of the spring in the weldment.

So far so good. 40+ hours, a few not so pretty landings and my spring remains secure.

If there is judged to be merit in this fix, and interest, I will try to post the sketch I made of the conical washer and the whole fix as it looks assembled.

A peer review discussion is welcome.
 
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Sounds like a decent solution.

gereed75 said:
I had this problem also due to poor workmanship when drilling the hole in the weldment that holds the tailwheel spring. My drilled hole on the bottom of the weldment had some slop and allowed the tailwheel spring to rotate in the socket - my fix:

I had a local machine shop turn a conical washer from 4130 high strength steel. The washer was about .4" thick and the ID bore was a tight fit on the AN 4 bolt. The shoulder of the washer was turned into a cone shape with a 100 degree angle (the same as the angle under the head of a countersink AN screw). I then used a 100 degree countersink as a cutter and cut the 100 degree countersink through the weldment and into the tailspring. The bolt (a slightly longer one than stock, to provide room for the conical washer and to keep the washer on the bolt shoulder) was installed and tightened, and the conical washer was pulled into the countersunk surface (sort of like a valve seating in an angled valve seat).

This whole thing can be done from a 3/4" access hole drilled into the fuse bottom, just below the spring retainer bolt.

I believe that this is a good fix because it actually increases the surface area of contact between all the mechanisms involved. It also pulls the tailspring weldment into tension against this 100 degree seat, while taking out all play. Also you now have some compression holding the assembly together and you are just not relying on the shear of the bolt against the tailwheel weldment to counteract the twist forces of the spring in the weldment.

So far so good. 40+ hours, a few not so pretty landings and my spring remains secure.

If there is judged to be merit in this fix, and interest, I will try to post the sketch I made of the conical washer and the whole fix as it looks assembled.

A peer review discussion is welcome.
Click to expand...

Your description was perfect. I can not comment on the integrity of your fix as I dont know how much side loading there is on the tail wheel that produces the torque on the spring. I suspect your fix is better than the original "hole through the tube" though.
Mine was a QB fuselage and I suspect the factory did not do a good job when drilling those holes. Interestingly enough, my 3 kit has the tailwheel assembly all drilled and bolted together as it came. It is tight, tight, tight.
I will keep your fix in mind if mine should worsen on my 6.
Good thing is, both parts are steel and nothing critical is going to happen even if it is a bit loose. Just something to watch over time. Worse case over time, I could change out the weldment, a bit tight in there, but doable. I would try your fix before I went that far. Thanks.
 
I also looked at removing the weldment - and I also judged it doable but lots of work. If my fix doesnt hold up long term, that is what I will do. But so far so good. I think the fix is pretty robust.

If a new weldment became necessary, I think I would also consider beefing up the wall thickness of the weldment in this location with a doubler welded on to give it all a bit more beef.

Hope it never comes to that.

Fly on. Be safe.
 
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