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Thread: Therapy Project

  1. #121
    RVBottomly's Avatar
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    Quote Originally Posted by Cub junkie View Post
    You planning on the "H" or "X" brace in the bay in front of the tail post?
    I'm still trying to figure out what the differences are. I'll use one of them, probably. X intuitively seems better, but I need to read up on them more.

    Another place that looks like it could use bracing is at the stabilizer attachment on the upper longeron. It sits mid span. I've seen references to the longeron being bent there.

  2. #122
    Cub junkie's Avatar
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    I like the X. Easy to do.
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  3. #123

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    I would build the X simply because it is structurally better.
    And I would brace the stab mount area as well, does not need much, maybe a 5/8x.028 or .035 on each side.
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  4. #124
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    Up for air after a couple of weeks. I reached something of a milestone, now having the main fuselage mostly tacked together. There are still a few tubes to put in, but the shape is there. It measures square and pretty close to the numbers on the drawing.

    I weighed the assembly using a moment arm technique I worked up for boat building. No pictures, but the basic idea is to find the center of balance, and then put a fulcrum 10 inches one way or the other from the center of balance. Then go to the up end and add weights at a certain distance. Then calculate the moments. I did it both ends and came up with 54.4 pounds each way.

    Seeing it was pretty light, I hung it from a rafter and weighed it with a fish scale. It came out to 54.7 with that method, but that included the ropes tied to the frame to hang it from.



    Then I rolled the jig table outside.





    The main point to all this moving was to get the assembly lower for work on the superstructure. I hope to build a rotisserie from scraps in the near future.
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  5. #125
    Lowrider
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    Looks like progress to me!!

    I used 2 V-8 engine stands for the fuselage turn around thingy and they worked really well for welding and painting...just a thought.
    Somewhere along the way I have lost the ability to act politically correct. If you should find it, please feel free to keep it.

    There are no new ways to crash an airplane no matter how hard you may try!
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  6. #126
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    Quote Originally Posted by Lowrider View Post
    Looks like progress to me!!

    I used 2 V-8 engine stands for the fuselage turn around thingy and they worked really well for welding and painting...just a thought.
    I've seen something like that, but I don't have any engine stands.

    But what I do have is an extra 22' piece of 7/8" tubing. Seems like that would make fairly decent axle spit with some homemade bushings from leftover 1" tubing.

  7. #127

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    The rotisserie is easy enough to make from wood. A dolly for the base, say 2X3', a braced vertical 2X4 tall enough to allow full swing of the finished structure. At the firewall, it is nice if the pivot point can be changed as the balance of the structure changes such that a piece of plywood bolted to the engine mounts might be right, but just a board across the upper two and the lower two engine mount point with a vertical board with the pivot points drilled in.
    Tail post end can be hose clamped to a bit of angle that has the pivot tube welded to it.

    An issue with most engine stands is their pivot tubes are not level to the ground, they are always twisting about when spinning the structure. This does not allow for stability which is our safety. There is no way I want something to start rolling over when I am half inside the structure leaning on it as I weld.

    I do have a heavy duty rotisserie that I built decades ago for building cars and boats, this is a recent BMW build on the spit.
    IMG_9786.JPG

    And a different one getting the interior painted last summer,
    IMG_0639.JPG

    Rolling a ton of car is a one man task when balanced right and a 100# fuselage can be safe and simple.
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  8. #128
    Cub junkie's Avatar
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    I use ho' made U joints at each end. I was going to use old car U joints but they are bulky and usually greasy. I made up a couple of U joints from floor sweepings. You can cobble anything in framework to work off old saw horses etc. or some type of similar stands. The Harbor Freight cheap auto engine stands with the ubiquitous 20% off coupon are affordable and I never feel guilty chopping on HF stuff, it usually needs it anyway.
    Attached Images Attached Images

  9. #129
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    Wow, three weeks since last update. That's mainly because I had little to show. But I spent a fair amount of time with a tape measure, plumb bob, homemade trammels, etc., tracking down annoying discrepancies.

    I was working on the superstructure and I had the hardest time getting things square. I built a scaffold and measured everything against the datum line. Tacked up some tubes in a perfect square (according to the template), only to find it out of square when I mounted it on the scaffold.

    Heh. CharleyN and Marty said there'd be days like this. I had about 6 (partial) of them--tacking and then going back and grinding away tacks--measuring, fitting, rejecting, re-profiling, clamping, measuring, etc. On and on. Finally it came together. The only way I could really line things up was to fasten a swiveling wire on the tail post and measure everything from there.

    So, finally a step forward:





    It's still pleasant therapy for me, despite the back-eddies. My great plans at freeing more time got derailed by a bunch of new cases assigned to me. On the upside, it looks like I'll hit my court-mandated limit in August instead of next January. Maybe that will free up some time.
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  10. #130

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    I am happy I bench made my cabin top since it is square. I have since welded too it and it has yet to move and with the X brace it may well have some pent up loads in it but it remains accurate.
    With it being square this reduces your workload when getting it in place on the rest of the fuselage.
    Basically you are not trying to keep it square as well as level and lined up all at the same time.

  11. #131
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    Another installment. I need to add up my hours in my handwritten log.

    I opted for simplicity regarding a rotisserie. A couple of 2X4s clamping the front tubes with bolts, and a 1/2 carriage bolt running through a 1X4 triangle.

    The tail region rests on a fairly sturdy platform. I can rotate the fuselage easily by lifting the tail section and twisting. Because of a notch in the rear platform, I have 8 positions of rotation without even trying.

    I still need a few more tubes tacked in, but today I was rotating, checking, and refitting a few joints that didn't line up well on my first go. At least the shape still seems straight.






    But, of course, life has other draws, too. There was the call of fishing on the Snake River to attend to as well:


  12. #132
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    2 weeks go by and you'd think nothing happened. And, as far as apparent progress goes, you'd be right.

    But a lot of wheel spinning went on.

    I decided to really check every dimension one last time before starting the finish welds. I leveled up the horizontal reference line and started trying to level the fuselage on its long axis. I was alarmed to find the next to last aft station was not level with all the other points. Plus, the tail post was off from vertical by a degree.

    I thought about denial. What's a degree here or there? So what if the center of the next to last station is off by 1/4"?

    So the therapy project opened up a new line of inquiry: what kind of builder do I plan to be? A night passed, and then out came the grinder, homemade clamps, triple-checking of connections, and spatial visualization near the edge of my capacity. I also laid out and leveled some 4X4s on the uneven concrete shop floor for reference points. In the end, now I can say that every tacked joint and station is plumb and straight. The wing attach points are on spec within 1/32" (which is as good as I can read on my tape measure).

    And I'm back to where I thought I was 2 weeks ago. I also finally added up my shop time on the log: 133 hours since mid November 2017. I hope I can step up the pace this summer.
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  13. #133
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    Good for you. Do the very best that you can or in the end you will not be satisfied. I once had a carpenter doing some work for me who had an expression which he kept repeating "Good enough for this shack". Well as you may expect, that was the quality of his work. Certainly nowhere near aircraft tolerances. If you don't strive to do the best, you will never achieve the objective.
    N1PA
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  14. #134

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    Quality Control is the most important part when striving to achieve good quality. One Rutan designed plane I built with a partner back in the early 80s had a larger pile of scrap foam and glass than what is in the finished plane. In the end the quality was superb but getting there was wasteful.
    A few days ago the treasurer for my chapter was over, he commented on all the incomplete weld joints on my plane, hard to explain why it is way too early to finish weld the joints. But as you found, one does not want to weld everything too early.
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  15. #135
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    I haven't posted much here lately, because the picture doesn't obviously change. But still plugging away at welding the frame.

    I straightened some slight twists that showed up.



    When the boat was still out after a July 4 fishing trip, I got a better view of the fuselage:



    And the whole point of a major project is to have an excuse to buy tools. I ordered a modest 750 pound mill drill.
    The freight company promised me a week's notice. So I got a call today just before some hearings that the guy would be in town at 3PM. We arranged drop off at a local depot and I picked it up there.

    I wasn't ready for it, but improvised with a sturdy work bench, some pipes, and a come-a-long:







    So now I have another diversion, but I'm looking forward to what this RF-30 knockoff can do.
    Last edited by RVBottomly; 07-11-2018 at 08:10 AM. Reason: corrected typo
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  16. #136

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    That should be a handy tool.

  17. #137
    www.SkupTech.com mike mcs repair's Avatar
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    I like that All thread push tool. Will have to remember that. Would be good for taking on ferry jobs.


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  18. #138
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    Quote Originally Posted by mike mcs repair View Post
    I like that All thread push tool. Will have to remember that. Would be good for taking on ferry jobs.

    Yeah. It took more time finding a couple of washers than it did putting it together. I've got 1/2 inch and 3/8 inch models.

  19. #139
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    Moving right along....

    I haven't posted for a month and a half, but not because nothing was happening. It's just that nothing obvious was happening.

    It's the finish welding process that doesn't show much. I took to heart Dr. Randy's water thread when we had a stretch of 114 degree days. It's amazing how quickly sweat forms and evaporates when you add some hot metal a few inches away. I could only get in a few half hour stretches before going off to do something cooling and relaxing, like weed wacking or setting fence posts.

    Plus, best laid plans regarding work were completely derailed. My firm commitment to a leisurely pace was overridden by zealous prosecutors and an impatient judge. Nevertheless, I'm persisting....

    Closing in on finish welding the basic frame and I detoured for some playing with my milling machine.





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  20. #140
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by RVBottomly View Post
    Moving right along....

    I haven't posted for a month and a half, but not because nothing was happening. It's just that nothing obvious was happening.
    It gets less obvious the closer to the end you get!!! Keep plugging away. Looking great!


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  21. #141

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    Thank you for posting the pictures of your progress. I'm living vicariously...can't wait to get home to my shop.


    stan
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  22. #142
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    Looking for an education on engines

    I'm close to finishing up welding the basic frame. I'll start working on landing gear fittings and then start looking at my wing options.

    But, I think I need to start looking down the road at engines.

    When I started the project, I had some partially formed idea that I'd find a used O-320 and work with that. Now that I've been around for a while and having looked at other builds, plus I'm pretty committed to adding floats, etc., I'm seeing that I really ought to go with around 180 hp.

    And, since I'm saving so much money scratch building (Ha!), I'm thinking of getting a new engine.

    One thing I think I'd like is the option to fuel with nonethanol premium, which is abundant in my area. I'm starting to think I might want a constant speed prop, but I'm not convinced of that yet.

    So I've looked at the Titans; the x-340 looks interesting, the x-360 looks more familiar. I know there are other options, but I'm not even up to speed enough to know what I ought to be looking for.

    Any input?

    Thanks,
    Vic

  23. #143
    brown bear's Avatar
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    You may want to give Superior a call . 2 years ago I price a Exp. 0360 kit engine from the for 21300 , I think that was with a carb. and mags.
    Doug
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  24. #144

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    Similar thought for me, but being at the other end of the income scale it will be a used 360. By keeping the compression below 8.7 will easily allow Mogas. By not running standard mags will take the shake out of the engine as well as offer more lower rpm power. Call that cruse power.
    The trick there is having a proper timing advance to suit the power loading at various RPM.
    I will run an electronic fuel injection as well, many here will say this is a stupid thing to do but my past 25 years experience teaches me otherwise.
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  25. #145
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    Quote Originally Posted by CharlieN View Post
    Similar thought for me, but being at the other end of the income scale it will be a used 360. By keeping the compression below 8.7 will easily allow Mogas. By not running standard mags will take the shake out of the engine as well as offer more lower rpm power. Call that cruse power.
    The trick there is having a proper timing advance to suit the power loading at various RPM.
    I will run an electronic fuel injection as well, many here will say this is a stupid thing to do but my past 25 years experience teaches me otherwise.
    I'd forgotten that I already was attracted to low compression for that reason.

    I don't know enough to understand why someone would think EFI would be stupid... I've read all sorts of things and I've hit a wall on trying to figure that aspect out. I guess part of it is fuel system simplicity. I like simplicity, to a point. But my 2015 F 150 has all sorts of magic stuff in it and it's the best truck I've ever owned.

    I pretty much decided on modern magnetos, though.
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  26. #146

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    The modern magnetos as in with having an advance cure are probably the best way to go.
    Myself, I will be running either a Denso or a Mitsubishi alternator utilizing an internal regulator. These are about the most reliable form of power generation to run the electrics. With them and using very good wire for everything under to cowl I am not worried about needing to trust an electrical system be it ignition or injection. Kind of need both to keep a smile.

  27. #147
    skywagon8a's Avatar
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    Quote Originally Posted by RVBottomly View Post
    I'm starting to think I might want a constant speed prop, but I'm not convinced of that yet.
    Study the engine data sheets.
    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/299fa3d6aef0ba048625821e0072188a/$FILE/1E10_Rev_28.pdf

    Look at NOTE 8 for the description of each model. Some models have provisions for a constant speed prop and some do not. Those that do use a governor which can be mounted at one of two places. The accessory case or the left front of the crankcase. When mounted on the accessory case you will need to cut a hole in the firewall to make room for the governor. This makes for tight quarters for all purposes. You also will need to be certain that there is not any tubing in the fuselage at this location which is in the way. I strongly recommend that you choose an engine model which has provisions to mount the governor on the left forward portion of the crankcase. You do not need to use a constant speed prop, but you will have the capability when you find that you should have.
    N1PA
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  28. #148
    RVBottomly's Avatar
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    Thanks for that insight and info. On my own I never would have thought to look for that difference.

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  29. #149
    skywagon8a's Avatar
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    Quote Originally Posted by RVBottomly View Post
    I pretty much decided on modern magnetos, though.
    Quote Originally Posted by CharlieN View Post
    The modern magnetos as in with having an advance cure are probably the best way to go.
    I've apparently missed something. What do you mean by "modern magnetos"? Are there some magnetos which have changing timing other than with impulse couplings? Magnetos which will retard their spark at low rpm and idle? Retarded spark for low RPMs on O-360 engines eliminates the rough shakes.
    N1PA

  30. #150

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    Quote Originally Posted by skywagon8a View Post
    I've apparently missed something. What do you mean by "modern magnetos"? Are there some magnetos which have changing timing other than with impulse couplings? Magnetos which will retard their spark at low rpm and idle? Retarded spark for low RPMs on O-360 engines eliminates the rough shakes.
    It would be me who has this described wrong, If I am correct we have self powered ignitions available? By ignitions I mean electronic triggers and timing processors.
    Myself, I will more than likely run what I am used too and that is a system we run in race cars. As stated, not what anyone else here would use.

  31. #151
    skywagon8a's Avatar
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    That makes sense Charlie. Automotive ignition systems have improved tremendously over the years to a point where they are virtually fool proof. I don't know what is used in race cars, however I do believe that the P-mags are the closest ignition system available which has the attributes of both the automotive and self powering of the magneto. The P-mags only need a small outside voltage input for operating at low RPMs.
    N1PA

  32. #152
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    Question about front gear fittings

    I've been whirling around in circles making and remaking gear fittings. I finally have some put together.

    But a gnawing question keeps coming back to me: I keep reading about welds cracking on a washer at the cabane attach point on PA 18s. Here is what my drawing says to do:

    front gear fitting washer side.jpg

    Two questions:

    1. The bolt hole size is 1/4 inch. Seems like I've seen it larger for heavy duty gear installations.
    2. Is the weld-on washer (red arrow) going to present a problem? I've been contemplating using a doubler that crosses both holes.

    The plans have a gross wt of 2200. I might be second guessing things, but as designed it seems kind of light.

    Vic

  33. #153
    skywagon8a's Avatar
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    I'll let others speak to the size of the 1/4" bolt. I agree it seems to be too small. Perhaps for a lower gross weight?

    The reason for the AN970-4 washer is to increase the bearing strength of the fitting in order to prevent the bolt from pulling out the end of the fitting. The increased thickness increases the bearing strength. The drawing indicates that the washer is welded completely around to the fitting except along the edge. This concentrates the loads on the weld thus when over loaded it will break along the weld.

    You could increase the thickness of the fitting to equal that of the original fitting plus the thickness of the washer, leaving off the washer. This will give the same strength without the stress concentration at the weld.

    Lacking the availability of the thicker materiel just make two fittings, edge welding them together. Blend the edge along the cross tube to distribute the weld loads.

    If I were to use a washer as shown in the drawing, I would edge weld it to the base fitting leaving off the weld extending from the 10 o'clock to 5 o'clock location with the exception of placing a tack at about the 2 o'clock location. Or one at 12 & another at 3 o'clock.
    N1PA
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  34. #154
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    The 1/4" bolt is for the 1500 lb gross weight. That is upped to a 5/16" bolt for the 1750 and 2000 lb gross weight. Airframes makes a thicker fitting where they doubled up the material thickness between the cabane fitting bolt hole and gear fitting bolt hole. All depends on you mission and amount of abuse you intend to inflict.
    Steve Pierce

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  35. #155
    RVBottomly's Avatar
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    Quote Originally Posted by skywagon8a View Post
    ...


    Lacking the availability of the thicker materiel just make two fittings, edge welding them together. Blend the edge along the cross tube to distribute the weld loads.


    That's exactly what I was contemplating. I appreciate what you said about weld stresses. I seem to remember repeated references to the joint breaking at the weld of the washer.


    Quote Originally Posted by Steve Pierce View Post
    The 1/4" bolt is for the 1500 lb gross weight. That is upped to a 5/16" bolt for the 1750 and 2000 lb gross weight. Airframes makes a thicker fitting where they doubled up the material thickness between the cabane fitting bolt hole and gear fitting bolt hole. All depends on you mission and amount of abuse you intend to inflict.

    Thanks, that is what was causing the gnawing in my head. I must have been thinking of the beef-ups for the gross weight increases.


    It seems like a good idea now to fabricate them with 5/16 in mind and the doubler.


    Of course, my full intent is to baby this project, operating only from golf-course-style grass runways with obstructionless approaches, etc., but... I can't help but notice the gravel river beds on the nearby rivers, or the notable airstrips just across the WA/ID border from me. I'd like the structure to be up to the task.

  36. #156
    Gordon Misch's Avatar
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    Increased thickness would be best. But doubled is better than single. Think about load path - with severe loading the bolt bends some (probably elastically) , primarily loading the inner layers of the fitting. That transfers to the outer layers of the fitting via the welds or deformation of the holes. Given your 2300 lb gross weight, I'd suggest going to the trouble of making the fittings out of heavier material if that isn't too big a pain in the rear.

    Also, maybe consider longer "fingers" where the gear fittings weld onto the fuselage tubes, to distribute the load.

    Opinion - - -
    Last edited by Gordon Misch; 10-28-2018 at 09:27 PM.
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  37. #157
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    Quote Originally Posted by Gordon Misch View Post
    Increased thickness would be best. But doubled is better than single. Think about load path - with severe loading the bolt bends some (probably elastically) , primarily loading the inner layers of the fitting. That transfers to the outer layers of the fitting via the welds or deformation of the holes. Given your 2300 lb gross weight, I'd suggest going to the trouble of making the fittings out of heavier material if that isn't too big a pain in the rear.

    Also, maybe consider longer "fingers" where the gear fittings weld onto the fuselage tubes, to distribute the load.

    Opinion - - -
    Right now the fitting is spec'ed from .090 4130 sheet. The only bend is the 90 degree bend at the top to reach the cross tube. I see Wicks has .190 sheet available, but it's pricey! I suppose the bend could be made with a suitable radius.

    I took a look at Airframes' heavy duty gear fitting. I see it has doubled pieces, and I noticed the internal washer is only edge welded on the outside. I assume that is to prevent the cracking I've heard about.

    https://www.airframesalaska.com/Fron.../af21272-4.htm

  38. #158
    Gordon Misch's Avatar
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    Yup, as Sky mentioned that weld on the outboard (away from centerline of the fuselage) edge of the washer could present a stress riser. And absence of the weld could present a crevice corrosion opportunity.
    Last edited by Gordon Misch; 10-28-2018 at 09:50 PM.
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  39. #159
    www.SkupTech.com mike mcs repair's Avatar
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    your fitting in drawing is already beefed up style , should be good

    heres what the originals look like that crack at the washer: not how its unsupported at washer.
    https://www.univair.com/piper/piper-...front-fitting/

    5/16 bolt

  40. #160
    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    Yup, as Sky mentioned that weld on the outboard (away from centerline of the fuselage) edge of the washer could present a stress riser. And absence of the weld could present a crevice corrosion opportunity.
    the original washers are only partially welded(edge welded, and its at the end of that weld where they crack)

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