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  • Warped crankshaft

    Myth or Fact?

    Local machine shop always had automotive crankshafts standing around on end on the floor. Like dominos. The "experts" claimed they would warp if not standing or hung from the end. I never believed it. Do you?

  • #2
    We need Myth Buster's..

    I think it is BS also. Probably better chance of hurting them when they fall over.

    [This message has been edited by cliff69 (edited 01-13-2005).]

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    • #3
      Total BS. Look up the elastic limit for steel/cast iron etc per square inch.
      Free software for calculating bolt circles and similar: Click Here

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      • #4
        Not sure about crankshaft but on large turbine rotor they are hung or they will warp.

        Joe

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        • #5
          Bar steel has been replacing cast iron, which had a good portion of the market until several years ago. If a cast iron lathe bed can warp measurably left on an unstable floor, why not a crankshaft on its side with no support for the journals? Den

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          • #6
            The Navy ship that I was on kept the prop shaft turning very slowly for that reason to prevent the shaft from warping.
            Charlie
            Don\'t ask me to do a dam thing, I\'m retired.
            http://home.earthlink.net/~kcprecision/

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            • #7
              I don't know how long I'd like to leave the cranks I use standing on the floor. These are big block 4 1/2 inch stroke forged cranks. They have gundrilled pins and knife edged arms to lighten them but they still weigh around 80 pounds...at $3500 a pop, I keep them in a crank box or in a block if they have to sit for a time. 80 pounds pressing on a bottom arm could make it set after awhile...or not. A buddy of mine is an engine builder. He thinks he has it figured out. He built a rack that he slides the cranks into. They hang off the flange...not a bit different than sitting on the floor weight wise. But you can't knock them over. I had an 8ft long jointer in my cabinet shop. Was packing up tools etc. to take on an out of town job for three weeks and put a big stack of oak pieces on one end but forgot to take them off. When I got back the table had warped quite a bit.
              Russ
              I have tools I don't even know I own...

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              • #8
                I'm going along with Evan on this one.Any automotive crank that's limber enough to warp under it's own wieght can't be worth a damn in an engine.
                I just need one more tool,just one!

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                • #9
                  Yes,a crank will warp laying on its side.Had it happen to a 340 mopar steel forging. Not uncommon to see it on new replacement cranks right out the box. Cranks must be stood on end or hung.

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                  • #10
                    the cranks are fine on end but we know cranks are soft as butter, dont use them as jack stands.

                    lol

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                    • #11
                      I dunno but i call bs on this this one...The only way they would warp is if there are stresses in the steel...Properly forged crankshafts should not have stresses in them...

                      Thats my uninformed opinion..
                      Precision takes time.

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                      • #12
                        This is a total machinist urban legend.

                        <font face="Verdana, Arial" size="2">Robert Hooke (1635 - 1703), a great English scientist, experimented with springs, clocks and watches. During his investigation of the spring he discovered that in elastic materials, stress and strain are proportional. He first presented this in a lecture in 1678 and it is known today simply as Hooke's Law.

                        Hooke's Law applies as long as the material stress does not pass a certain point known as its proportional limit. This is the point at which the physical properties of the material actually change. Any time an elastic material is loaded between zero and the proportional limit, the stress and strain are directly proportional and if the load is released the material will regain its initial dimensions. If the stress is doubled the strain is doubled; if the stress is tripled the deformation is three times as great, etc.
                        </font>
                        See here

                        The Modulus of Elasticity for steel is 29,000 KSI.

                        If we have a steel crank with journals that have a diameter that makes them exactly 1 square inch in area then we will have to exceed 29,000 lbs of applied force divided by the length in inches to exceed the elastic limit in order to produce a permanent deformation. Even if suspended on the ends horizontally with no support in the middle this isn't going to happen. Steel and cast iron are elastic materials. As long as the elastic limit is not exceeded they act as a spring and return to their original shape. They do not take a "set".

                        A lathe sitting on an uneven floor will warp most certainly but it is elastic deformation, not permanent. When properly supported evenly it will return to its correct shape.

                        Any permanent warping that may take place is reflecting built in stresses from machining/heating or other processes, especially ones that involve material removal that change the inbuilt stress distribution. Standing it on end won't change this. It is just this reason that cranks may be shot peened.

                        [This message has been edited by Evan (edited 01-14-2005).]
                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          Interesting topic! I was told to store my cranks(note...this is LONG term storage) the way I do by Ron Derry. He's an old engine balancer in Alberta who originally came from the US. He's a very interesting fellow who is involved in some leading edge technology in the performance world. He is the first (or was) to bring in Formula One metal treatments (vibratory stabilization?) to Canada. So I figured if it's good enough for him... He did say that the "set" wasn't permanent but may be enough to wipe something out. Crankshafts bend easier than you think. I ruined a small block Chevy once after hammering on the harmonic balancer. I know...your not supposed to but I had no installer at the time and thought a few blows wouldn't hurt. It bent the crank enough to rub on the block and the iron dust took out the bearings. Anyway, I sent an email to Bruce Crower(Crower crankshaft division) last night to see what he has to say. I also have a ruined 572 crank standing on the floor (for two years now) and I think for fun I'll measure it up, then lay it down for awhile and see if anything changes. Urban legend? Could very well be....or not.
                          Russ
                          I have tools I don't even know I own...

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                          • #14
                            I know for a fact the Bridgport tables bend due to the unsupported ends as do othe knee mills with long tables.

                            As regards a crank I can't see this being a problem as you don't support just one end and let the other hang.
                            Laid on the floor it will be supported on at least two webs with very little overhanging weight to cause a problem.

                            Once it's in the engine there are enough bearings to allow any mis alignment to be overcome.
                            After all we are talking about just a frew pounds static weight here. What about the crank under load inside an engine.
                            Does that bend due to combustion forces.

                            I'll lay a pound to a pinch of $hit that if you take any high milage working engine and put the block on a line boring machine it will be bent.
                            so why was it still running fine ?

                            John S.
                            .

                            Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                            • #15
                              Crankshafts are flexable. Take the harmonic balancer off an engine and start it up.

                              Every engine shop I've been into either stands them on end, hang them from one end, or when laying flat on the floor, supported on thier mains with blocks.

                              Urban legend? I don't think so. My $.02

                              ------------------
                              Gene
                              Gene

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