Bearings

Discussion in 'General Engine Discussion' started by Theunis, Jan 24, 2019.

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  1. Jan 24, 2019 #1

    Theunis

    Theunis

    Theunis

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    Hi im not new to this site but have never posted, however i read all new posts every morning and the information here is priceless.

    My question is whether i would need bearings of any kind if i use brass conrods on a brightsteel crank with oil pressure feed on a beetle engine scale model of 200cc

    Would brass on steel be fine if i use oil under pressure as lube
     
  2. Jan 25, 2019 #2

    kf2qd

    kf2qd

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    How much do you plan on running it?
     
  3. Jan 25, 2019 #3

    Theunis

    Theunis

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    I would love to have a engine that could potentially run many hours
     
  4. Jan 25, 2019 #4

    Richard Carlstedt

    Richard Carlstedt

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    That will work, but what type of brass are you using ?
    That will determine life expectancy. A bronze alloy will wear much better than brass
    Also look at "superfinishing " the steel crank pin surfaces to get greater life.
    I converted an old electric shaver by adding a small stone to do the finishing
    Rich
     
  5. Jan 25, 2019 #5

    Theunis

    Theunis

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    Hi Rich.

    What bronze alloy would be best and would polishing crank journals with diamond paste to get mirror finish be good , also could i make insert bearing halves from bronze and use alluminium as material for conrod

    Regards
    Theunis
     
  6. Jan 25, 2019 #6

    Hopper

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    6061 or similar aluminium rods with bronze inserts would work well too. I would not use brass. Too soft to withstand the pounding a big end cops. A leaded bronze such as SAE 660 should work OK. I would not use phosphor bronze unless the steel shaft is hardened.
     
  7. Jan 25, 2019 #7

    davidyat

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    My interest is "beetle engine". A VW? If so would love to see pictures, plans or anything, if it is a VW model engine. I have a real 1967 VW that is my daily driver. Would also love to make a VW Model engine.
     
  8. Jan 25, 2019 #8

    Richard Carlstedt

    Richard Carlstedt

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    What Hopper said is on the money. 660 is a Bearing Bronze that would work very well and it's new (er) designation is 932 C . There are harder bronzes like Aluminum bronze or Phosphor bronze and they work well with Hardened steel journals, but are really tough for home shop machining. I am not sure of metal numbering systems in Kiwi land ?
    Diamond paste polishing will work, but when most guys polish they use a soft support surface, like a rag and what you want is accomplished by superfinishing which eliminates all the "mountains" on the micro surface of the metal . If you do use Diamond , try using a vary hard piece of wood that is slightly narrower then the journal and shift/oscillate it back and forth. The wood should be hard,smooth and FLAT...or maybe even use a piece of brass
    Rich
     
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  9. Feb 1, 2019 #9

    jagwinn

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    Sounds like a nifty project! Details please?
     
  10. Feb 4, 2019 #10

    Richard Carlstedt

    Richard Carlstedt

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    I wrote it up on another thread/website, but here is a repeat:

    Well My photobucket account is shot so I will try to explain a few things without pictures.
    The Process was invented by Chrysler Automotive back in the 1930" s to improve crankshaft bearing life, and it did dramatically by producing a surface finish far finer than turning and grinding did and reduced wear measurably.
    So much so that is is used throughout the world today. It involves presenting a fine abrasive to a turning surface and oscillating that abrasive cross-wise to the rotating metal. Industrial machines are very expensive and I have given links at the bottom below to show you the commercial machines and some commentary. Basically you have a non repeating oscillating abrasive move irregularly across a rotating workpiece to remove offending surface protrusions created by earlier machining /grinding work. It is not a heavy force application like milling or grinding (!) ( OR Burnishing !). Low forces ( hand pressure) are all thats required to remove the high points and it does not remove "valley" irregularities
    Now let me tell you how to make one at home .
    One of the secrets to Superfinishing is variability. you do not want a oscillation that is controlled time wise ( think metronome ) and the more irregular, the better. While commercial machines use rolls of abrasive or stones , a home machine can use a small stone...like a 600 India stone or finer .
    Let me tell you what I did as I am not sure whats available today. I found a old electric razor at a flea market 20 years ago. This was a Palm unit that is similar to this eBay sales item

    https://www.supfina.com/products/sup...hing-machines/
     
    Last edited: Feb 4, 2019
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  11. Feb 4, 2019 #11

    Richard Carlstedt

    Richard Carlstedt

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    Here is the rest of the posting

    Now let me tell you how to make one at home .
    One of the secrets to Superfinishing is variability. you do not want a oscillation that is controlled time wise ( think metronome ) and the more irregular, the better. While commercial machines use rolls of abrasive or stones , a home machine can use a small stone...like a 600 India stone or finer .
    p important part is that it is not a rotary unit shaver, these old ones oscillate quite fast ( 500 CPS ?) and vary with load as the vibrators are not strong
    Throw the head away and make a adapter to hold a stone ( 1/2 x 1/2 x 4 ?) . My adapter was a small piece of walnut (1 x 2 x 3/8" thick ) that was milled to hold the stone . make the slot about .002 smaller and the wood will hold it. the wood milled so it is retained by the 2 vibrating arms that formerly moved the shaving blades L & R by oscillating them maybe .010-.020 "---perfect for superfinishing
    Now when you have a piece in the lathe , rotate the work piece about 100 RPM and set the stone that is exposed from the end of the shaver head on the surface with a bit of oil and watch the surface get really smooth. The stone moves both forward and backward and also oscillates side to side. this criss-crossing knocks all the irregularities down to give a superior surface . If you find an old electric razor , it can be pretty cheap addition to the shop for journal turning .
    Keep the rotary speed (lathe) down so you don't crash and run the lathe backward, so any force throws the offender upward and not downward into the carriage/ways. Obviously CARE must be used to keep the stone moving left to right and not hitting a crank throw.
    I wrote an article for Model Engine Builder magazine a few years ago about this in magazine issue number 29 which is available pretty cheap on line
    https://www.modelenginebuilder.com/

    Rich


    commercial machines
    https://www.aaabrasives.com/shop-man...superfinishers

    Description of the process
    https://www.supfina.com/products/tec...y/superfinish/
    results
    https://www.supfina.com/products/sup...hing-machines/
     
    Last edited: Feb 4, 2019
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  12. Feb 4, 2019 #12

    stevehuckss396

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    Last time I drove by the Chrysler building was still there but in very bad condition. This is the building where the process was invented according to the Chrysler historians.


    Amplex.jpg
     
  13. Feb 4, 2019 #13

    karlw144

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    Here’s a picture of Rich’s polisher, been meaning to make one since my visit.
    upload_2019-2-4_10-27-44.jpeg
    Rich, hope you don’t mind me posting this.
     
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  14. Feb 4, 2019 #14

    Richard Carlstedt

    Richard Carlstedt

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    Perfect Karl, Thank You !
    A few more words
    The stone in the picture is 3/8" wide--it can be what ever you have. ( 1/4 or even 1/8 )
    Obviously I am NOT touching the crank until it is in the lathe , it was a info pic.
    The wood grips the stone without glue, just make it snug.
    The two splayed pins on the shaver may get loose on the wood piece so I use my middle finger to hold the wood (mandrel) against the pins .
    This is not a "Precision Tool" but a very simple and effective solution .
    Rich
     
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  15. Feb 25, 2019 #15

    jagwinn

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    Thanks, Richard!
     

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