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Thread: Therapy Project

  1. #241

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    Quote Originally Posted by gdafoe View Post
    Sounds like a great idea. Pictures we need pictures.
    This is part of a roller set for 7/8 tube mounted on my older mill.
    IMG_7425.JPG

    The rollers are machined out of HDPE bar.
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  2. #242
    gdafoe's Avatar
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    Very interesting thanks
    Gerald

  3. #243
    RVBottomly's Avatar
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    Fuselage weight so far and jack screw bracket

    I ran out of materials for a while, so, being curious, I decided to weigh the fuselage as it is right now.

    20190521_1917541144114693.jpg

    After I weighed, I noticed that the scale read about 3 pounds heavy with no load. I took it to be 97 pounds in reality.


    20190521_1916571799647123.jpg

    I tested that weight two other ways: one using my so-called balance beam approach where you balance the object, and then move the fulcrum a known distance and add weight on one of the arms to calculate weight on the balance point. That method produced 96.8. The other method was simply a two-point weighing with a digital fish scale, yielding 96.5 pounds.


    So 97 pounds is a fair guestimate. Frankly, I was surprised because the fuselage is almost a foot longer than a PA 18, and I used some .028 stiffing tubes in the tail sections of the fuselage. I was bracing myself for something heavier. This weight includes the turtledeck arches and the superstructure formers, but no tabs to speak of and no channel for doors, etc.


    Then my UPS delivery came. I spent some time pondering how to make the jackscrew bracket assembly. The plans simply said to buy it, but I had trouble finding it online. So I went with trying to fabricate it. I couldn't have even begun without Northland drawings and Christian Sturm's drawing website.


    20190525_141548176782718.jpg

    20190525_143013433263659.jpg


    20190525_144401317177342.jpg


    20190525_145357902776389.jpg

    Jigging the assembly


    20190525_1607361366684421.jpg

    Tacked.


    20190525_163455649228959.jpg


    20190525_1635141803125729.jpg


    I've got some tweaking to do, but I was surprised how it went together after scratching my head over this for days.
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  4. #244
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    Adjusting stabilizers

    After tacking in the jack screw pedestal a couple days ago, it seemed right to put the stabilizers in place to check the alignment.

    20190527_143043355987767.jpg

    I didn't take photos, but I adjusted that jack screw pedestal to align with the center and had to tweak the tail to make it straight.

    Next checked how the stabilizer travel was working. At first it looked like it would bind on the pedestal legs, but I saw that it was out of alignment with the center line. A few adjustments on the rear pivot point allowed it to move up and down more freely.

    2019.05.27-stab-1.jpg


    2019.05.27-stab-2.jpg

    I spent a fair amount of time getting the horizontal reference line leveled again and then measured the up and down travel. It's 2 degrees up and 6 degrees down.

    That's within PA 18 specs according to the erection manual, but I need to find some specs like that for a PA 14. Either that or spend some time noodling the difference in angles of incidence on the fuselage.

    I took some photos front and back just because, and then I dropped my camera and broke the lens. Just another day in the shop....

    20190527_1500571535820479.jpg

    2019.05.27-fuse-2.jpg
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  5. #245
    Gordon Misch's Avatar
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    That jack screw tower can be a stinker. If it's not aligned just right it messes up all sorts of related stuff. Don't ask how I know!
    Gordon

    N4328M KTDO
    My SPOT: tinyurl.com/N4328M (case sensitive)
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  6. #246
    skywagon8a's Avatar
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    Look at page 2: You have slightly more than the spec. Leave it there, more is always better than not quite enough.
    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/fd34b4a887cf0ab786256a61006cac5c/$FILE/a-797.pdf
    N1PA
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  7. #247
    RVBottomly's Avatar
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    Quote Originally Posted by skywagon8a View Post
    Look at page 2: You have slightly more than the spec. Leave it there, more is always better than not quite enough.
    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/fd34b4a887cf0ab786256a61006cac5c/$FILE/a-797.pdf
    That's exactly what I was looking for. Thanks!

    Vic

  8. #248
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    Working on bungee struts

    I'm still pondering suspension, but for the time being I figured I'd build gear struts as shown in the drawings. They are a bit different from the drawing because I extended the gear.

    I learned something, though. I first fabricated bushings to weld onto the end of the struts, welded them on, and put finger straps over them. The plans said "ream (drill) to 3/8" after welding."

    Well, welding that material ended up hardening it, and I wore out drills trying to make a slightly undersized hole for reaming.

    So I started over and drilled the bushing material first on the lathe. It worked out easier.

    20190615_1238381978328976.jpg

    2019.06.15-shock-strut-bushing.jpg

    20190615_1017041360069992.jpg

    Also milled out coves for the bungee attachments

    20190615_1523042026583280.jpg

    20190615_1606511819060306.jpg

    I'm still eyeballing things and am scheming up a dampening device. Meanwhile, I wanted to see how things traveled.

    2019.06.15-gear-in-front.jpg

    2019.06.15-gear-out-front.jpg

    I need to look at my notes in the shop. My recollection is that there is 10 inches of axle travel for 4.5 inches of strut telescoping.

    A movie of it:


  9. #249
    RVBottomly's Avatar
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    More landing gear work

    Time goes by, and I have the occasional hour here and there to work on things. I've sort of entered the drudge zone: fabricating the bungee strut assembly.

    I'm not fully convinced I want to use the as-designed system. But I'm interested enough in getting the fuselage on wheels to go ahead with the materials I have.

    So, a few photos of the drawn out process of making bungee struts.

    First reinforcements welded on.

    20190624_193707885949407.jpg

    Then drilling 1/4 inch holes for bolts to slip through a slider that is supposed to hit stops in inside the inner strut.

    20190621_19145226330577.jpg

    After all this welding, the outer strut no longer accepted the internal 3/4 sliding strut. So I needed to ream it out. I didn't have a 3/4 reamer, but I did have a 3/4 hole saw and an old hole saw chuck that I could weld to drill extension. After going through lots of cutting oil and wearing down the hole saw to .735", I went to lapping compound and more oil. Eventually I had a free-sliding tube. The word of advice here is to order a 3/4" hand reamer. My excuse was that they were backordered.

    20190625_191255701709125.jpg

    Actually, the photo is out of order, but welding on bungee attachments.

    20190625_184227325470394.jpg

    Testing the fit and alignment with Walmart bungees

    20190625_193356663448512.jpg

    The internal strut has a 1/4" slot through which a bolt goes to a slider inside the strut. So time to try to make slots.

    20190626_1908561145010177.jpg

    The slider and stops within the internal strut were specified at a certain diameter. Of course, the inner strut material I had was thicker walled 3/4 tubing, and I didn't have a proper tube to fit the smaller diameter. But I did have some thick walled 5/8 tubing that could be turned down. Here is a testing of the fit.

    20190629_1928511517977895.jpg

    I still need to install the stops and slider, but I wanted to eyeball the travel of the strut.

    20190629_1938531525889115.jpg

    20190629_1939071642019510.jpg

    So, everything seems to be consistent with the plans. I still need to add caps on the bungee attachment ears and also add the internal stops. It seems strong enough, but I'd like to have rubber bumpers in front of the stops. Not enough room to put all this stuff in, though.

    I have some nice new bungees. I'm impressed with how stiff they are. As in, I'll have to review those installation videos a few times to make a decent tool for the task.

    So, I'll use this set up for now, but I still am noodling variations ranging from simple homemade oleos to some of the fancy suspension systems described on the site. I may end up with several different versions to try out. That is what is cool about experimental building. But it is SLOW, sometimes.

  10. #250
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    More landing gear strut fun

    Finally brought this phase more or less to completion.

    First had to clean up the slotted strut and fabricate a slider. I ruined one strut by letting the slot go wild before I caught it while milling.

    20190704_161914392470146.jpg20190704_1621042098846619.jpg

    The it was time to fabricate the internal stops the slide runs into.

    Used a hole saw to get some 5/8 discs.

    20190706_104229417582927.jpg

    20190706_1054361489131134.jpg

    I neglected to get photos for installing the stops and slider. Suffice it to say that a stop goes in first, then the slider (properly aligned to fit the holes in the lower strut), and then the other stop. The stops are welded in place.

    Next I used a 1 3/4 hole saw to cut out 1 1/2 discs for the bungee retainers. The inside diameter of the hole saw I had was exactly the 1 1/2 inch specified.

    Then welded them on.

    20190706_1402181703412477.jpg

    20190706_1432281072325158.jpg

    20190706_153412548118026.jpg

    After some post-welding clean-up and tweaking, the struts move up and down as advertised. I have bungees, but I don't want to put them on until I paint the assembly and...build some kind of bungee installation jig.

    In other news, the wing materials I ordered in April may or may not get shipped next week. It depends on who you talk to at Aircraft Spruce. I'm really looking forward to starting on that portion of the project.
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  11. #251
    RVBottomly's Avatar
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    Heh. Just when I was thinking I was mostly done with the bungee suspension, I ran across Bill Rusk's post on his Javron build.

    And saw this picture:

    P10000611.jpg

    From post 154: https://www.supercub.org/forum/showt...l=1#post525332

    So now I think I need reinforcing gussets too....

    For the sake of curiosity, I jury-rigged up a stretch test bed to see how stiff the bungees I have were. They are stiff. Approximately 100 pounds per inch of stretch. They start out at about 10 inches at resting stretch, and have another 10 inches when installed in the retracted position. Two per side is around a ton total on those little ears. Then when you bounce, even more force. I was nervous about the set up as designed. The Javron arrangement has convinced me to add the gussets.

    All of this is connected to the self-education aspect of experimental. I had a 4 hour road trip today and spent most of the time noodling in my head acceleration rates with changing bungee forces over distance. Blah! But fun.

  12. #252
    RVBottomly's Avatar
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    Gussets, now a question

    I added gussets to the bungee struts. Then, of course, had to ream out the slag again so the tubes would telescope. I feel better about it all.

    20190713_1547001988260132.jpg

    But now a question.The old farmer in me wants to know why there are no grease fittings on the hinge points? I've looked several places and have not seen anything like that. I've seen them added to elevator hinge points, etc. Why not landing gear?

  13. #253

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    My guess would be petroleum based grease and natural rubber are not that compatible. The other reason is the old "we don't do it that way".
    DENNY
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  14. #254

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    There are plenty of lubricants available today that would not harm the rubber.

    When I make a pivoting joint, the bushing material will be an engineering plastic, Teflon, Delrin, UHPDE or such.
    The inner sleeve would be Stainless steel, chrome plated shafting, or hard anodized aluminum.

    These all make build and forget assemblies.

    Back in the mid 70s I started using chrome shafts from old shock absorbers from cars bikes or whatever, machined as needed. These were mounted around the bolt they ride on and fitted snug inside a Delrin bush. As of today every one of these joints are still in service without any need for maintenance.

    I still build this way, I have not used a bronze or any metal bushing in my life.

  15. #255
    Cub junkie's Avatar
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    Extra grease finds its way all over your aircraft courtesy of the slipstream. Non commercial airplane will be fine with a light lube each condition inspection.
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  16. #256
    RVBottomly's Avatar
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    Quote Originally Posted by Cub junkie View Post
    Extra grease finds its way all over your aircraft courtesy of the slipstream. Non commercial airplane will be fine with a light lube each condition inspection.
    I was thinking along these lines after I posted the question. It's not like your average square baler is going over 12 mph ever.

    CharlieN, your approach is light-years ahead of what I've done. I like it, but felt like doing it as drawn for the first iteration. But it's not even bronze bushings here. Steel on steel.

    All the steel on steel pivots or hinges I've seen (other than, say, door hinges)--like on swather casters or irrigation hose reels--had nice grease fittings. So I started wondering.

    That and reading about the occasional problem I've read about with landing gear suspension frozen from sitting out in the elements too long.

    So the key, as drawn, is lubrication. It just seemed grease would be convenient, instead of disassembly and lube say every annual.

  17. #257
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    Christmas in July

    Two deliveries arrived today.

    First, I got some tires:

    20190719_1949591495890351.jpg

    Basic 8.50 X 6

    BTW, one tire has a sticker saying "First Tire." Anybody know what that means?


    Then, after waiting since early April, my spruce spars and related materials showed up:

    20190718_154154-1421928220.jpg

    20190718_160115319448709.jpg

    So I'll put wheels on so I can wheel the fuselage around, and then set up for building wooden ribs. I felt like a kid at Christmas, even if I had to use a sharp Buck knife to open up the presents.
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  18. #258
    skywagon8a's Avatar
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    Quote Originally Posted by RVBottomly View Post
    All the steel on steel pivots or hinges I've seen (other than, say, door hinges)--like on swather casters or irrigation hose reels--had nice grease fittings. So I started wondering.

    That and reading about the occasional problem I've read about with landing gear suspension frozen from sitting out in the elements too long.

    So the key, as drawn, is lubrication. It just seemed grease would be convenient, instead of disassembly and lube say every annual.
    Vic,
    Originally the stabilizer pivot tube passed through another steel tube welded to the tail in the fuselage (still does). The outer tube had a hole drilled into it in order to make it easy to squirt oil. How often do you think this got done on airplanes which were stored outside and not flown much? As a result there were a lot of "frozen" stabilizer hinge tubes. The trim still worked because the tube was twisted a little. The angular change for full trim travel is very small so the build up of rust didn't get noticed. This was usually found when a mechanic attempted to remove the stabilizers for periodic recovering. Now with lifetime fabrics even this doesn't get done very often. As a result some of us mechanics began welding a small tube over the oil hole in order to screw in a grease fitting positioned so as to not interfere with the control horn. I see no reason not to do the same thing for the gear fittings. No one will fault you for deviating from the plans for this.
    N1PA
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  19. #259
    RVBottomly's Avatar
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    Just for fun, I put the wheels on and rolled the fuselage out into the sun.

    2019.07.20-fuse-outside.jpg

    2019.07.20-fuse-c-outside.jpg

    Actually, the prosaic reason was that I wanted the shop empty so I could rearrange things for rib making. Plus a little spring cleaning that was put off until July.
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