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  1. #1

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    Boca bearings for OS .35 AX

    Looking to replace bearings in my OS 35 AX. I'm running over 15,000 RPM on the stock bearings. Thinking they are not meant for this and looking at ceramic bearings or stainless from Boca.

    Possibly these ?

    http://www.bocabearings.com/productd...SubGroupID=110

    I'm somewhat new to extreme rpms and planes.


  2. #2

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    RE: Boca bearings for OS .35 AX

    The stock bearings should be fine.
    These engines are designed to turn around 17k or so.

  3. #3

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    RE: Boca bearings for OS .35 AX

    stainless may not rust but my experience has been that stainless alloys used arent hard enough, so i go back to steel, the ax bearings should be fine into the low 20k rpm until worn out

  4. #4
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    RE: Boca bearings for OS .35 AX

    I went with the Boca stainless steel bearings for my Rossi .61 and have been very happy. One thing I noticed is that the fit of the Boca units were better then the stock Rossi bearings. The engine runs even better then when new. I attribute this to the better seal between crankshaft and crankcase that the better bearings provide.

  5. #5

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    RE: Boca bearings for OS .35 AX

    Thanks for the replys guys:

    I didn't know the stock bearings could be run up to 20 K rpm. I running 10% nitro 18% oil content for engine protection. I'm getting a good smoke trail out of the muffler at full throttle, so am running slightly rick. Thanks again

  6. #6

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    RE: Boca bearings for OS .35 AX

    I have been running (abusing) an OS 32 for years. The thing was black from carb fuel spray cooked on and running a tad too lean but having too much fun to land and richen. The thing was fugly so I covered the holes, bead blasted and put it back in service. The engine is constantly screaming it's heart out and eating dust, yet the bearings are amazingly still good. Longest lasting bearings of any engine I've ever had!

    I'd just run the crud out it and not worry too much on this one. If you worry, pull the prop while turning, listening and feeling every once and a while.

    I have done a lot of bearing changes and tried a lot of steel, hybrid ceramic and stainless in different engines (sports to ducted fan). From what I've observed, I've come up with my own set of rules:

    #1 Ceramic was a tad faster, but lasted half as long as stock before feeling gritty, even if the bearings were broke-in rich.
    #2 Even tho stainless is a few points softer Rc than bearing steel, stainless lasted longest in glow engine when nitro was in the fuel, but only if the bearings had non-metallic cages (especially not stainless cages[:'(]).
    #3 The only real advantage to stainless is when it's used primarily for the rear bearing,(except high nitro marine F&R).
    #4 The only steel bearings that last are those that have non-metallic retainers (ploymite).
    #5 You can leave both seals on the front bearing, excess grease will sling past the seals when it gets to temperature . Fuel/oil will still enter and lube the bearing eventually, front seal will help keep dirt out and rear seal may help boost case pressure.
    #6 Remove both seals/shields from rear (big) bearing.
    #7 Boca and RC bearings sell great bearings. RC's are inexpensive and most of their stainless types feature non-metallic retainers, check the other guy's!

    RC doesn't offer stainless for the 32, so see my rule #4, 5, 6, and 8 $$$
    http://www.rcbearings.com/os-32-sx-bearings/
    Oooh eee oooh ah ah(the crowd) ting tang walla walla bing bang!(the plane crash)

  7. #7

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    RE: Boca bearings for OS .35 AX

    Thanks freakingfast for taking the time to explain this to me. I don't want to sound like a "Nervous-Nellie", but this is my 2nd OS .35 AX.

    On the first one, the ball bearings actually left the housing and destroyed the engine. As long as you can see a smoke trail coming out of the muffler while running, does this show that you are not running too lean and that oil is passing out of the engine-lubricating the moving parts ?

  8. #8

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    RE: Boca bearings for OS .35 AX

    My bad, I need to put my glasses on, I saw 32 when your talking 35AX. Change the bearings to be safe if you killed one.
    Oooh eee oooh ah ah(the crowd) ting tang walla walla bing bang!(the plane crash)

  9. #9

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    RE: Boca bearings for OS .35 AX

    The 32 was a screamer and the 35 is lower rever and puts out about the same net useable net power but you need to prop them differently to get the best of both.
    Running lean can hurt the bearings, but most likely I'd blame the current supplied bearings, good luck getting them to admit it. Usually running lean causes the sleeve to peel, piston to scuff or loose pinch. Lean conditions can also cause pre-ignition that pulls out elements in the plug, hurts rod ends, peens the bearing races (soon grenades) and snaps cranks at port or pin.
    Oooh eee oooh ah ah(the crowd) ting tang walla walla bing bang!(the plane crash)

  10. #10

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    RE: Boca bearings for OS .35 AX

    I run a lot of OS engines, and I have a habit of running them pretty hard. Change the bearings to good aftermarket ones. Listen to what freakingfast has to say. I stay away from ceramic because they are too brittle. Ever nick a prop?? That can shatter a ceramic bearing, not worth the extra couple hundred rpm for me.I seem to be landing challenged sometimes.

    I have a personal rule for any OS engine - 20% oil. 25%castor and 75% synthetic. I have never peeled a nickel liner with the extra oil I run. The bearings still wear out eventually, so keep an eye on them.

    Good luck.
    Scott
    Revver Brother #260

  11. #11

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    RE: Boca bearings for OS .35 AX

    I'm running a 10 X 6 MS for prop, Mousse can muffler with header, turning a little over 15 K on ground.

    Thanks again

  12. #12

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    RE: Boca bearings for OS .35 AX

    OS 32 on tuned pipe 10X4 black master Airscrew. Mounted on a PBF (corroplast board,not a speed plane). Unloads like crazy and pulls like crazy back to speed after a direction change.
    Oooh eee oooh ah ah(the crowd) ting tang walla walla bing bang!(the plane crash)

  13. #13

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    RE: Boca bearings for OS .35 AX

    I'm running a OS .25 FX on my PBF with mousse can muffler. These things are a blast to fly.....if you want to call it flying !!!!

    http://davenixphotography.smugmug.com/Other/Spadfest-2012/23480363_WV76Kp#!i=1905384390&k=qChMsqV

  14. #14

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    RE: Boca bearings for OS .35 AX

    Almost as much rush as a speed delta, but lot different.

    Shown with an APC, broke the other.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Oooh eee oooh ah ah(the crowd) ting tang walla walla bing bang!(the plane crash)

  15. #15

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    RE: Boca bearings for OS .35 AX

    many sport engines run ABEC 2-3 bearings, going to a ABEC 7 bearing will give rpm gain too, the higher the number the greater the clearance, check out what nelson,jett, Mb and others use..often ABEC 7 spec ....FWIW

  16. #16
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    RE: Boca bearings for OS .35 AX

    Where do you get these bearings? Most of what I see on the Boca site are C3

  17. #17

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    RE: Boca bearings for OS .35 AX

    King bearing likely, or simply call boca or any reputable bearing house, my novarossi engines use them, they are very free and run cooler along with living longer too, they feel loose i can easily detect endplay when cold, not a bunch but some.. i have a set in in a rossi 45 FIRE, but dont remember which place i ordered them from. i will look and see if i have the source still

  18. #18

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    RE: Boca bearings for OS .35 AX


    ORIGINAL: lfinney

    many sport engines run ABEC 2-3 bearings, going to a ABEC 7 bearing will give rpm gain too, the higher the number the greater the clearance, check out what nelson,jett, Mb and others use..often ABEC 7 spec ....FWIW
    I think you may be confusing ABEC with the clearance spec. Nearly all engine bearings are ABEC 1-3. A few are ABEC 5. None will be ABEC 7 as there is no advantage to those and the cost is significantly higher. Clearance for 99% of engines will be CN (between C2 and C3). High performance engines will normally have C3 or sometimes C4 clearance.
    Steel and Ceramic bearings for model engines
    5% discount for RCU members. Code: rcu

  19. #19

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    RE: Boca bearings for OS .35 AX


    ORIGINAL: RC-Bearings


    ORIGINAL: lfinney

    many sport engines run ABEC 2-3 bearings, going to a ABEC 7 bearing will give rpm gain too, the higher the number the greater the clearance, check out what nelson,jett, Mb and others use..often ABEC 7 spec ....FWIW
    I think you may be confusing ABEC with the clearance spec. Nearly all engine bearings are ABEC 1-3. A few are ABEC 5. None will be ABEC 7 as there is no advantage to those and the cost is significantly higher. Clearance for 99% of engines will be CN (between C2 and C3). High performance engines will normally have C3 or sometimes C4 clearance.

    +1

    I am going to buy bearing from RCbearings.com from now on. 1/4th the price of boca and better bearings. They have the Nonmetal retainers. I have tried the super expensive Ceramic also and what a waste of 100 dollors.

    I love how guys read about bearings and want abec 7 bearings lol no clue on them. All the skate board and skate shops try to sell the ABEC 7's. all they are doing is getting those kids to buy good bearings only to wear them out on the street because of all the dirt lol ABEC 3 is best for the street where ABEC can be used on cleaned everyday outdoor skating surfaces. ABEC for indoor use only and cleaned often. Not good in RC planes as the other guy stated...
    AMA # 126183
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  20. #20
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    RE: Boca bearings for OS .35 AX

    I buy stainless balls in bulk and build retainerless bearings for engines I plan on keeping around.
    I usually fill up the bearing until there is only room for 2 more balls, then call it good.
    You can do a "flick test" with just the bottom end assembled to see what the difference is.

    WHO GUNNA FEED MAW KEEEIDS..???


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