A-1148 "Tailwheel Spring Upper Support"

[Ron Greene]

Re: A-1148 "Tailwheel Spring Upper Support"

Hank,

I think the docs will show that felt was the original material,and as you say, felt will retain moisture.

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Mike,

On the L-2 felt was used between the bracket and the tail spring. The three bumps help to retain the felt. There are three bumps on the bottom tail spring bracket also.

Mystery solved - thanks - Mike

[barnstmr]

Re: A-1148 "Tailwheel Spring Upper Support"

Mike... Here is the longeron tube info I used on the 337 for my repair.

DETERMINATION OF ORIGINAL STRUCTURE MATERIAL:
REFERENCE: TAYLORCRAFT AVIATION CORPORATION INSTRUCTION MANUAL – MODEL B/B12 THIS MANUAL STATES THAT ALL FUSELAGE MEMBERS ARE OF SAE 4130 STEEL. THE BROKEN MEMBERS ARE PART NO. B-1510 FOR MODEL B12 FUSELAGE ASSEMBLY. ORIGINAL LONGERON TUBE MATERIAL IS 3/4 INCH O.D. X .035 INCH WALL.

REPAIR MATERIALS:
2 EA. INNER SLEEVE: SAE 4130N STEEL TUBE 5/8 INCH O.D. X .049 WALL
2 EA. OUTER SECTION: SAE 4130N STEEL TUBE 3/4 INCH O.D. X .035 WALL

[barnstmr]

Re: A-1148 "Tailwheel Spring Upper Support"

Terry - thanks for the pic. Great help. How did you cut out the 3/8" radii?
- Mike

Use a rotary file in a die grinder.

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Use a rotary file in a die grinder.

Oooh. don't think I've seen one in HD Aerospace. Better look that up; sounds useful. - Mike

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Mike... Here is the longeron tube info I used on the 337 for my repair.

DETERMINATION OF ORIGINAL STRUCTURE MATERIAL:
REFERENCE: TAYLORCRAFT AVIATION CORPORATION INSTRUCTION MANUAL – MODEL B/B12 THIS MANUAL STATES THAT ALL FUSELAGE MEMBERS ARE OF SAE 4130 STEEL. THE BROKEN MEMBERS ARE PART NO. B-1510 FOR MODEL B12 FUSELAGE ASSEMBLY. ORIGINAL LONGERON TUBE MATERIAL IS 3/4 INCH O.D. X .035 INCH WALL.

REPAIR MATERIALS:
2 EA. INNER SLEEVE: SAE 4130N STEEL TUBE 5/8 INCH O.D. X .049 WALL
2 EA. OUTER SECTION: SAE 4130N STEEL TUBE 3/4 INCH O.D. X .035 WALL

You raise an interesting point. At what point is a 337 needed for what I'm doing and what I've done? To date an AI has inspected my minor welding and replacement of spars in the ailerons and other work and given an approval to cover, but no mention of a 337. - Mike

[barnstmr]

Re: A-1148 "Tailwheel Spring Upper Support"

You raise an interesting point. At what point is a 337 needed for what I'm doing and what I've done? To date an AI has inspected my minor welding and replacement of spars in the ailerons and other work and given an approval to cover, but no mention of a 337. - Mike

Mike - A 337 is required for all MAJOR repairs and alterations. This is defined in the FAA regs 14 CFR Part 43 appendix A.

go to the following link and read the FAA regulation and it should be clear.....

http://www.risingup.com/fars/info/part43-A-APPX.shtml

Here is an excerpt about major repairs.
b) Major repairs -- (1) Airframe major repairs. Repairs to the following parts of an airframe and repairs of the following types, involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs.

(i) Box beams.
(ii) Monocoque or semimonocoque wings or control surfaces.
(iii) Wing stringers or chord members.
(iv) Spars.
(v) Spar flanges.
(vi) Members of truss-type beams.
(vii) Thin sheet webs of beams.
(viii) Keel and chine members of boat hulls or floats.
(ix) Corrugated sheet compression members which act as flange material of wings or tail surfaces.
(x) Wing main ribs and compression members.
(xi) Wing or tail surface brace struts.
(xii) Engine mounts.
(xiii) Fuselage longerons.
(xiv) Members of the side truss, horizontal truss, or bulkheads.
(xv) Main seat support braces and brackets.
(xvi) Landing gear brace struts.
(xvii) Axles.
(xviii) Wheels.
(xix) Skis, and ski pedestals.
(xx) Parts of the control system such as control columns, pedals, shafts, brackets, or horns.
(xxi) Repairs involving the substitution of material.
(xxii) The repair of damaged areas in metal or plywood stressed covering exceeding six inches in any direction.
(xxiii) The repair of portions of skin sheets by making additional seams.
(xxiv) The splicing of skin sheets.
(xxv) The repair of three or more adjacent wing or control surface ribs or the leading edge of wings and control surfaces, between such adjacent ribs.
(xxvi) Repair of fabric covering involving an area greater than that required to repair two adjacent ribs.
(xxvii) Replacement of fabric on fabric covered parts such as wings, fuselages, stabilizers, and control surfaces.
(xxviii) Repairing, including rebottoming, of removable or integral fuel tanks and oil tanks.

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Here's the parts that went into the longeron repair on my airplane.... and the section that we replaced.

Terry – This exercise is instructive on multiple levels.

1. I can’t tell for sure, but it appears you did what I plan to do; start with rectangular tubing and avoid the bending.

2. The A-1148 drawing and your “as built” differ a bit, but apparently that isn’t going to cause a problem. Could you have cut the trailing side of the stock to stand 9/16” tall, but not sloped the edges? Or, is the slope required to spread forces?

3. The drawing shows the ends with a 13/32” radius. Is there an engineering reason to round those ends or may I leave them square?

4. As usual, I get focused and don’t see easier solutions. Or maybe it’s an experience thing. I saw myself disassembling the lower cluster on the fuselage, replacing parts, then standing on my head to weld them into place. You (and Capt Jon) simply disconnected the tailpost from the fuselage, re-build it at your ease on your work bench, and spliced it back into place. I need to see how this can be applied to that rotting cluster I discussed in an earlier thread.

5. Die-grinder - I was confusing die grinder and angle grinder. I do have an air driven die grinder with an appropriate burr. I’ll see if I can scoop out the metal with it (after I mow the lawn).

6. And apparently I can – see attached. This one is made of unknown metal; just practicing for the big event.

- Mike

[barnstmr]

Re: A-1148 "Tailwheel Spring Upper Support"

Terry – This exercise is instructive on multiple levels.
1. I can’t tell for sure, but it appears you did what I plan to do; start with rectangular tubing and avoid the bending.
2. The A-1148 drawing and your “as built” differ a bit, but apparently that isn’t going to cause a problem. Could you have cut the trailing side of the stock to stand 9/16” tall, but not sloped the edges? Or, is the slope required to spread forces?
3. The drawing shows the ends with a 13/32” radius. Is there an engineering reason to round those ends or may I leave them square?
4. As usual, I get focused and don’t see easier solutions. Or maybe it’s an experience thing. I saw myself disassembling the lower cluster on the fuselage, replacing parts, then standing on my head to weld them into place. You (and Capt Jon) simply disconnected the tailpost from the fuselage, re-build it at your ease on your work bench, and spliced it back into place. I need to see how this can be applied to that rotting cluster I discussed in an earlier thread.
5. Die-grinder - I was confusing die grinder and angle grinder. I do have an air driven die grinder with an appropriate burr. I’ll see if I can scoop out the metal with it (after I mow the lawn).
6. And apparently I can – see attached. This one is made of unknown metal; just practicing for the big event.
- Mike

Hey Mike... honestly, your attention to detail is more than mine. Although a lot of the things I do come from being around airplanes so long. I will try to answer your questions if I can

1. You can bend plate in a hydraulic press if you don't have square tube
2. Hmm... honestly, without a factory print, we just did our best to match the part being replaced.
3. rounded edges are found everywhere in aviation. It is a habit of mine that comes from my mentors and A&P school. 3/32 is pretty small. Just a touch with a grinder and/or a file should make a nice smooth edge.
4. no, we cut out the assembled piece you see in the photo, but did no welding until everything was aligned and clamped in place on the airframe. I don't recommend welding anything separate... in fact, because of the angularity it would be impossible to do it that way... if you spend any effort on details, spend extra time in checking and re-checking alignment, squareness, plumbness, straightness, etc... you'll pay later if things don't line up. Tack everything little by little and keep checking, because things tend to warp as you weld. take your time... and yes, stand on your head if you need to.
5. hand-held air tools are awesome!
6. your practice part looks great. You are doing better than you give yourself credit for.... go for it... and buy a goat for the grass... you'll get the airplane done faster that way.

[barnstmr]

Re: A-1148 "Tailwheel Spring Upper Support"

Mike...
It occurs to me that all this time I assume you have an A&P or IA overseeing your work. If not, please do. And I assume you are doing a "sleeved splice" as shown in the FAA Advisory Circular AC43.13-1B. The AC is great general advice, but does not cover every conceivable situation. In our case, the break was not exactly like anything shown in the AC. So I did the attached sketch for the 337 repair.

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Mike...
It occurs to me that all this time I assume you have an A&P or IA overseeing your work. If not, please do. And I assume you are doing a "sleeved splice" as shown in the FAA Advisory Circular AC43.13-1B. The AC is great general advice, but does not cover every conceivable situation. In our case, the break was not exactly like anything shown in the AC. So I did the attached sketch for the 337 repair.

Terry - I have an IA who I call in when I need something inspected. Last time around I asked him to examine the fuselage and point out area I might not have spotted that need to be addressed. My tailpost is fine except for some heavy pitting about an inch above the bushing. I tried to get him to allow me to replace the metal with an internal sleeve splice, but he asked me to replace the tailpost. Actually, what he said was "If it were me, I'd replace the tailpost" and when he repeated that the SECOND time I interpreted that as "Shut up and color". So here I am .

The picture you provided is what I got out of 43.13 and have been practicing as a splice by internal sleeve, but what is that area represented by a "~" in one drawing and cross hatching in another? - Mike

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Hey Mike... . 3/32 is pretty small. .

but the ends of the bracket are a 13/32 radius. Am I correct that you are saying "round it smooth and forgetaboutit" ? - Mike

[mhorowit]

Re: A-1148 "Tailwheel Spring Upper Support"

Hey Mike... honestly, your attention to detail is more than mine. .

Yeah - I call it "getting wrapped around the axle"; it's not necessarily a good thing because it can cause me to cavitate for months before doing anything.

In this case I'm recalling a (much) earlier discussion on "stress risers", and the importance of smooth transitions, and a discussion I had with Bob when I was doing my aileron spar. I asked him why I had to taper the reinforcement plate (the plate the hardware attaches to) and he described how if I used a square-ended reinforcement piece, any bending would be focused on the edge of that reinforcement piece, but if I tapered it, any force would be gradually applied to the aileron. I likened it to the reinforcement at the hand grip of an archery bow.

Likewise, I can see how the trailing edge of the bracket could fall in this catagory and that's why it has sloping sides. I'm glad to hear I'm being overly cautious - of course, I'd make a lousy mechanic, since time is money .

Well, if the rain has stopped, I'm going to see if I can make that joint with the bracket and discover more things I don't know. Oh, major item I discovered with this exercise: You can't build on previous measurements because you get a cumulative error, and you should square off the end of the tubing before attempting to measure from it. Oh, and you can't locate precisely the center of a hole (after the hole has been drilled) - Mike

[barnstmr]

Re: A-1148 "Tailwheel Spring Upper Support"

Mike...
The area on my drawing labeled as "~" is a section I replaced in order to have a proper scarf. Since the tube break was straight across, I had to cut the angle from the top and from the bottom of the break... look at page 2 for the area removed.

[Carl E. Carson]

Re: A-1148 "Tailwheel Spring Upper Support"

My tailwheel didn't have felt between the springs but it did have webbing
material the width of the springs. That too would hold moisture just as felt would except the weave is more open which "might" allow a quicker drying time and hold less moisture. Seems to have worked since 1940's.

Carl