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Which aluminum alloy for a bushing

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  • Which aluminum alloy for a bushing

    Which AL alloy is most suitable as a bearing surface? I need to make and fit a liner into a galled bearing bore. Hard polished steel camshaft bearing runs in plain aluminum engine case. I will machine out and press fit a new AL liner bushing. Alloys on hand... common 6016 , Zinc based 7075 and copper based 2024 ? Going in, I'm thinking the 2024 would be best... any thoughts in this? I figure any of them would be better that the original engine crankcase casting material.

    Joe B

  • #2
    Are you sure the engine case is "plain aluminium" and not AL-Mag?

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    • #3
      Originally posted by lakeside53 View Post
      Are you sure the engine case is "plain aluminium" and not AL-Mag?
      1950's vintage British motorcycle... pretty sure regular sand case aluminum of unknown alloy.

      Joe B

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      • #4
        Aluminum bronze.
        Kansas City area

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        • #5
          I'm not an engine guy, but I can't imagine any of them holding up to real use as a bearing. 2024 is strong but not really that much harder than 6061. I've seen plenty of ovaled holes in AL where people thought they could get by without a bearing in a prop. I look forward to hearing what the real experts say.
          Location: Jersey City NJ USA

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          • #6
            Originally posted by JoeCB View Post
            1950's vintage British motorcycle... pretty sure regular sand case aluminum of unknown alloy.

            Joe B
            Unknown is a problem but that doesn't necessarily mean random or poor quality Al. Mag Alloys were used extensively in WW2 aircraft engines, VW engines, etc etc. It has characteristics that make for good plain bearing surface.

            Alloys (many types) are still used extensively today. Take a look (for one example) Honda lawn mowers, Subaru (another one example) heads, etc - there are no "inserts" - just parent materiel bore for the crank and cams. But this isn't your run-of-the-mill plain AL.
            Last edited by lakeside53; 01-27-2019, 10:08 PM.

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            • #7
              Believe it or not, Zamac is a very good bearing material. Hard, low coefficient of friction, and low material loss over time.

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              • #8
                I believe that at present the 3XX series of aluminum is thee choice for automotive engine blocks and cylinder heads due to it's good casting characteristics and wear properties.

                I think A360, A319, and B319 are the ones used for the vast majority of engine castings with alloys of the other 3xx family being used a lot for other applications like intake manifolds and suspension components. With proper clean pressurized oiling these alloys last hundreds of thousands of miles. I've also serviced large pump and fuel metering chambers with lots of hours on them that were cast of A356 that showed excellent service life.

                Not sure how they compare to the alloys you have on hand. I personally would probably go with the 2024 as my first choice if I could not obtain a piece of a known good candidate from a scraped automotive engine block, head, or transmission case. Knowing the what heat treatment condition is of the 2024 you have may also have a bearing on it's suitability.
                Home, down in the valley behind the Red Angus
                Bad Decisions Make Good Stories​

                Location: British Columbia

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                • #9
                  Without knowing the alloy it's hard to say what will work, or better, what will last. I wouldn't expect much from
                  plain 6061, 2024 or 7075 (which would be my last choice). I'd just play it safe and use aluminum bronze, then
                  you know it's going to last...
                  Keith
                  __________________________
                  Just one project too many--that's what finally got him...

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                  • #10
                    I have used 6061 and it worked. .. i know by Machining on such parts that it is likely harder than original material.
                    I on a split case, had put a dowel in to prevent the round bushing from turning, it had an oil hole into it..to oil the camshaft.

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                    • #11
                      What brand and era of engine is it? Most Brit bikes have been rebuilt by many folks and they've run across ALL the problem spots and found fixes for them.

                      Not just Brit bikes though. A riding buddy many years back had a Yamaha 650 twin and it had issues with galled and worn bearing journals in the head when the oil supply gallery got plugged. Apparently it was a common thing for that particular Yamaha engine. So checking on the procedure for fixing that one would likely provide you with some good information as well.

                      Bottom line though is that I can't think of any aluminium alloys that by themselves are good bearing options. They all rely on a steady flow of high pressure oil if there's much load on them.

                      The modern overhead cam inline 4's are like that tool The cams just sit directly in journals of the head alloy and rely on the high pressure oil supply same as the engine bearings.
                      Chilliwack BC, Canada

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                      • #12
                        Originally posted by Toolguy View Post
                        Aluminum bronze.
                        this thread is finished.

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                        • #13
                          Why not just an all bronze bushing?
                          Andy

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                          • #14
                            Originally posted by BCRider View Post
                            What brand and era of engine is it? Most Brit bikes have been rebuilt by many folks and they've run across ALL the problem spots and found fixes for them.

                            Not just Brit bikes though. A riding buddy many years back had a Yamaha 650 twin and it had issues with galled and worn bearing journals in the head when the oil supply gallery got plugged. Apparently it was a common thing for that particular Yamaha engine. So checking on the procedure for fixing that one would likely provide you with some good information as well.

                            Bottom line though is that I can't think of any aluminium alloys that by themselves are good bearing options. They all rely on a steady flow of high pressure oil if there's much load on them.

                            The modern overhead cam inline 4's are like that tool The cams just sit directly in journals of the head alloy and rely on the high pressure oil supply same as the engine bearings.
                            Yep' that is pretty much the situation... A plugged or obstructed oil port /dirt galled the bearing surface. I'm pretty much in agreement with what "754" said..."I have used 6061 and it worked. .. i know by Machining on such parts that it is likely harder than original material.
                            I on a split case, had put a dowel in to prevent the round bushing from turning, it had an oil hole into it..to oil the camshaft".

                            and thanks to "Wily" for the good info.. I'll look for some of that alloy

                            Joe B
                            Last edited by JoeCB; 01-28-2019, 10:06 PM.

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