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Babbit for crank bearings and its use today

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  • Babbit for crank bearings and its use today

    Hi all, I know how babbit bearings used to be used extensively for crank bearings up to the 50's, and nowadays its common to use a thinwall steel backed shell, with a bronze plating then a bearing material final layer.
    My question is, if I made a dam up to surround a crankpin in situ, and made a shim with a thin gap between it and the bearing surface, and poured babbit into this void, would I end up with something equivalent in terms of wear/ability to handle high loadings? If so, any suggestions on the size of void to leave?
    In short did we move away from poured in situ bearings to save labor, or because they are technologically superior. And do modern shell bearings still use tin babbett as their final surface layer?

    I have a engine, its currently running a roller bearing crank, but I can get a crankshaft from a different engine with the same spacing, and make some steel adaptors up to fit the casing and pour in situ. There is no shells available which will fit this combo, and it would seem doing it in place and hand scraping the babbit would lead to a more precise location using home shop methods than trying to adapt the shells from the donor motor.

    The reason to want to change crank bearing material, is at very high hp levels, the roller bearings brinnell the crank surfaces and destroy the crank. There are people offering conversion crankcases and crankshafts for this motor to do the same, but at $20,000 for the pair. I'm a tinkerer in my shed building a drag bike for fun, thats completely outside my budget and just buying in something to go fast is outside the entire ethos of why I want to race.

  • #2
    Insert bearings allow for a more controlled process
    of manufacturing. Easier to control all the variables.
    Also allows the process to be taken off-line, even
    outsourced of needed.

    --Doozer
    DZER

    Comment


    • #3
      Given the parameters as you have described, I think for me it would come down to a decision whether a more modern material would be superior to the babbett.

      What I am thinking about specifically is trying to modify the closest size of shells might leave you with such a thin layer or no layer for the crank to ride on (based on limited knowledge but some of the layers making up those shells are really, really thin to start with, aren't they?).
      But at the same time, there might be better "solid" material that what that poured babbett would be which you could modify without that issue.

      Some of the calculations as to load that I suspect are needed to make an informed decision are well beyond me. Agree with your thought a 100% that the hand scraping maybe exactly what is needed for level of precision.

      Comment


      • #4
        You would not use a shim when pouring the bearing. The proper clearance would be obtained by honing and/or scraping after the pour. If the rods have to be split to get get them off the crank, you will have to come up with some way of pouring a split in the babbit while keepimg the rod end centered on the crank. And to pour these the clearance between the rod and crank will have to be much larger than for a shell bearing.

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        • #5
          My very limited babbit bearing experience was re-pouring a wood lathe bearing. Put oakum or rope at the shaft ends and poured the melted babbit in the pour hole. Lasted for years and years.
          Retired - Journeyman Refrigeration Pipefitter - Master Electrician - Fine Line Automation CNC 4x4 Router

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          • #6
            From what I have read, engineering for performance at the extreme limits of materials requires a great deal of try-fail-change-repeat. Not much fun to be had there.

            Comment


            • #7
              My concern would be the differences in lubrication requirements. I have no idea which requires more lube but if the original lubrication method doesn't suit the babbit needs it would wipe out the bearing pretty quickly. Don't know if you've seen this but Keith Fenner has a Youtube vid of pouring babbit here: http://www.youtube.com/watch?v=wZh2VZbqQiI

              Comment


              • #8
                My experience with babbitt pours was to assist on a Little Giant power hammer re-babbitting. The bearings thickness is much greater than what I think that you are talking about. Ours were about 5/16" thick.


                The bearing outer surface (the housing) was preheated and a heated dummy shaft was installed to form the bearing area. In our case we used an undersized shaft and scrapped the bearing to fit after it was cast. After the lower shells were poured, the dummy shaft went back into the lower bearings and the caps were installed and the upper shells were cast through the 'oil' holes on the top. After the top bearing cooled it too was scraped to fit the main shaft. I have heard of using the exact shaft diameter for a dummy shaft and just removing shims between the upper and lower caps to obtain clearance, but I was told the scrapping is was a better path to take.

                Without a preheat and sufficient thickness, which both help to allow the hot babbitt to retain enough heat to fill the void, I don't think that it would be possible.

                If this is for a modern day engine, I doubt that the bearing performance would exceed the factory bearings. Might be fun to try though

                paul
                paul
                ARS W9PCS

                Esto Vigilans

                Remember, just because you can doesn't mean you should...
                but you may have to

                Comment


                • #9
                  My Moto Morinis use Babbit or White metaled shell bearings, but their crank loads are light.

                  Vandevell heavy duty bearings of Lead/Tin/Indium used to be option of choice in tuned Ford engines from the pre X-flow on up to the Cosworth BDA/FVA.

                  I believe the modern material of choice is Aluminium.

                  Bearing shells can be modified. Narrowing them is fairly easy and locating tangs can be filed off an re-punched. I think that's got to be your best bet.
                  Paul Compton
                  www.morini-mania.co.uk
                  http://www.youtube.com/user/EVguru

                  Comment


                  • #10
                    We use Babbit for propeller shaft bearings and do approx 6 a year. We add nickel to increase the wear. The amount depends on how much the owner wants to spend. The shafts are heavy but slow turning <1000 rpm. The bigger the shaft the slower it goes. A lot of engines run around 2000 rpm and 4.5 is a pretty common reduction. I don't think it would work good for a quick turning shaft. These shafts get one shot of grease a day if they are lucky nothing else.
                    Bill

                    Comment


                    • #11
                      I've witnessed a blown ford flat head set a record at the Salt Flats at over 212 mph with poured babbit bearings.

                      Steve

                      Comment


                      • #12
                        I have done poured white metal big ends for diesel engines, among other things, but wouldn't dream of trying it in situ. Apart from anything else the finish won't be good.
                        The usual way is to make an undersize former and cast around that, & bore out afterwards with final scraping if needed. Be aware that whatever you're metalling needs to be properly tinned beforehand, & that's a harder job with ferrous metals than with bronzes, cast iron is the worst.
                        I think you'll need tin-based rather than lead-based metal.

                        Tim

                        Comment


                        • #13
                          Originally posted by Timleech View Post
                          <<snip>>
                          I think you'll need tin-based rather than lead-based metal.
                          Tim
                          If you are referring to the use of tin based babbitt instead of lead based, I think that if you 'tinned' the bearing housing with tin based solder and then use a lead alloy babbitt you would have an excellent bond.

                          Here is a good source for some info on babbitt metals:

                          http://www.rotometals.com/Babbit-Bearing-Alloys-s/2.htm

                          I think that automotive applications are more likely to use the bonded babbitt that Tim referenced. The Little Giants babbitt bearings were more mechanically restrained.

                          Here is a neat thread on the process:

                          http://www.mtfca.com/discus/messages...tml?1387126616

                          and:

                          http://theoldmotor.com/?p=109413

                          paul
                          paul
                          ARS W9PCS

                          Esto Vigilans

                          Remember, just because you can doesn't mean you should...
                          but you may have to

                          Comment


                          • #14
                            Since the bearing material does not touch the
                            journal 99% of the time because of the lubricant
                            film, all the reasons for using it that cite material
                            and bond and horsepower are largely irrelivent.

                            -Doozer
                            DZER

                            Comment


                            • #15
                              Originally posted by ironmonger View Post
                              If you are referring to the use of tin based babbitt instead of lead based, I think that if you 'tinned' the bearing housing with tin based solder and then use a lead alloy babbitt you would have an excellent bond.


                              paul
                              The tin based bearing alloy is generally preferred for heavier duty applications (such as diesel engines).

                              Tim

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