Bearings

Discussion in 'Tube and Fabric' started by Little Scrapper, Feb 26, 2019.

  1. Feb 26, 2019 #1

    Little Scrapper

    Little Scrapper

    Little Scrapper

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    Looking for some general advice on bearings.

    The aileron hinge is a 1/4" aluminum bracket that is 3/4" wide. It attaches to another bracket that has a 3/16" hole.

    The only instructions are "ball bearing pressed in" as per the sheet.

    What kind of options are available that would make sense given the 3/4 width of the hinge arm? If the bearing is too wide on the O.D. it creates a thin wall on the bracket.

    Do aircraft bearings have unique standards vs other types? Back in 1957 I'm not what they did but I'd imagine they used off the shelf type bearings?

    Would it make sense to press a bronze bushing in?
    IMG_20190226_083838316.jpg

    IMG_20190226_083926935.jpg
     
  2. Feb 26, 2019 #2

    Topaz

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    You're sure it's not called out somewhere else in the drawings, perhaps a marginal note or in the bill of materials, if included?

    Clearly there was a "ball bearing" available at the time the plans were drawn, so I wouldn't second-guess about bronze, myself. 1957 wasn't exactly the Dark Ages.
     
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  3. Feb 26, 2019 #3

    Little Scrapper

    Little Scrapper

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    It's not called out anywhere that I found that's why I'm asking.

    What I meant by 1957 was that homebuilt airplanes and this design was just starting, so maybe there's more options? Different options? Have ball bearings changed in 60 years? I don't know.

    I don't know anything about ball bearings used in aircraft.
     
  4. Feb 26, 2019 #4

    Topaz

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    Very likely, Smith used the best bearings that he had available. Not everything was aircraft-quality in 1950's homebuilts. Whether or not to use aircraft-quality (which usually means MIL-SPEC, as far as I understand), is entirely up to the builder.
     
  5. Feb 26, 2019 #5

    Little Scrapper

    Little Scrapper

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    I guess I'm hoping to find more detailed information. What does best mean? AS lists multiple types, like I said, I don't know so I'm trying to learn about bearings.

    There's different widths as well. The arm is only .750" wide and there's different bearing widths so I'm a bit cautious until I learn more. Bearings weren't covered in plumbing school for high school and I'm having a hard time finding information about them.
     
  6. Feb 26, 2019 #6

    Pops

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    I have to agree, If you don't make the arm wider, maybe a bronze shoulder bushing and pressed in the hole with a little JB Weld to keep it tight.


    I'm almost in the middle of nowhere and there is a bearing store about 10 miles away where you can find about anything you want. I use ball bearings for the flap torque tube in the JMR. Also in the aileron bellcranks out in the wings and in the stick torque tube. Same as the Bearhawks.
    Lots of different quality in bearings, also for different speeds, temps, thrust, etc. It can be a whole different field of knowledge. Just like aircraft bolts and hardware.
     
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  7. Feb 26, 2019 #7

    TFF

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    Your standard is going to be the Aircraft Spruce catalog; preferably paper. Start looking at specs. Most are going to look at something like this https://www.aircraftspruce.com/catalog/appages/dpbrng.php There are lots to look at. Old style catalogs are hard to come by where you can just look at tables of parts like the old days. Grainger may have something that will work too. Those parts have been built with anything from direct aluminum, sleeved with bronze, hardware store bearings, real aircraft bearings. I worked on a Mooney once, replaced the trim bearings; the whole tail moves on these bearings. Bearings were from Grainger because that is where Mooney gets them. Correct PN.
     
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  8. Feb 26, 2019 #8

    Pops

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    And the straight tail C-172 used 1956 Chevy Pickup inside door handles, Piper Cherokee's used VW Bug inside door handles. Yep, they just picked out something from a supplier.
     
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  9. Feb 26, 2019 #9

    ScaleBirdsScott

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    Fun fact but since I happen to be staring at a poster here at work with the lineup, the SSN575 Seawolf, the second ever nuclear sub, was commissioned in 1957. (Nautilus was 1954)

    It's all "ancient" history as far as I'm concerned, having grown up in the 90s and all; but fun to keep those things in parallel. I'd imagine "aircraft" grade bearings date back to, say, the 30s?
     
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  10. Feb 26, 2019 #10

    Pops

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    For a shoulder bronze bushing look at Aircraft Spruce P/N 05-03569.
    Bearing I used in the aileron bellcranks were $12 each for the local supplier.
     
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  11. Feb 26, 2019 #11

    Little Scrapper

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    Those are some funny facts. Thanks guys.

    My biggest concern is the wall thickness. Looks like a 3/16" bearing is .500" or larger so on a 3/4 aluminum arm that's only a 1/8" maximum wall thickness. Not much considering the arm is made on a table with hand tools. I'm fussy with accuracy and somewhat of a perfectionist but man, that's a close fit.

    A bushing with a reamer seems right but again, I'm a bit out of my depth on the subject of bearings/bushings.

    I reached out to some Smith guys trying to see some actual examples.
     
  12. Feb 26, 2019 #12

    Topaz

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    Depends on the loading. But yeah, it must be a pretty light load.

    Smart.
     
  13. Feb 26, 2019 #13

    BJC

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  14. Feb 26, 2019 #14

    Armilite

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    ====================================================

    For the Cheapest Prices, Go on eBay, Type in Small Bearings and look for one that meets your Size. You going to want to use a Standard Sealed Bearing. All Bearings have an ID x OD x Width Spec usually in mm. Some of these Old Designs leave a lot to be desired, they used what was at hand for the Time, many parts from Go Carts & Mini Bikes, Local Hardware Stores.

    Like a 6305 Crank Bearing is 25mm x 62mm x 17mm.
    25mm ID
    62mm OD
    17mm WIDTH

    Aircraft Spruce carries many Bearings also, but High Priced.
    https://www.aircraftspruce.com/categories/aircraft_parts/ap/menus/ap/bearings.html
     

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  15. Feb 26, 2019 #15

    Toobuilder

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    The RV series uses a .250 thick aileron bracket with a press fit ball bearing. I had to build a new one for the Rocket in fact. Not sure what the ED is offhand but I can check tonight. In any case, absent any data from the Smith community, it seems like .125 ED on your bracket is plenty stout considering the probable loads. Do the math and see if it works.

    Also, I have buckets full of these small bearings from 1950's era surplus autopilot gyroscopes. The nominal dimensions of 3/16 x 1/4 x 1/2 seem pretty common. I use them for all kinds of stuff. Probably why they were selected on the Smith.
     
  16. Feb 26, 2019 #16

    BoKu

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    In a 3/16" bore you're kind of limited. Most of the little metric bearings around that size will be designed for high speed and low radial load, and won't last long in a low speed high radial load application. My suspicion is that the best bet is the KP3A, which has a 5/8" OD and gets you way more radial capacity than that thin little arm will react. Still, you probably want to bulb the end of that arm a bit so that you have at least 1/8" of meat around the bearing.

    --Bob K.
     
  17. Feb 26, 2019 #17

    Little Scrapper

    Little Scrapper

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    I feel like Pops is right, insert a bushing.

    Any drawbacks or issues with a bronze bushing/bearing?
     
  18. Feb 26, 2019 #18

    Pops

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    Bronze bushing are used on the elevator and rudder hinges of the Cessna 150/172's. One time I had to replace a center bronze bushing on the rudder of a straight tail C-172 were it was frozen to the bolt and turning in the aluminum at the OD. Not easy. Local old time IA got me going in the right direction.

    On the SSSC I used bronze bushing on the aluminum control horns for the aileron, rudder. Never any problems.
     
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  19. Feb 26, 2019 #19

    Pops

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    Had a family member on the Nautilus. At the same time my brother on a destroyer chasing Russian Subs.
     
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  20. Feb 27, 2019 #20

    proppastie

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