Page 1 of 5 123 ... LastLast
Results 1 to 20 of 87
  1. #1
    Cuda is offline Cast Iron
    Join Date
    May 2005
    Location
    Alabama
    Posts
    492

    Default Electrical runout?

    I'm working on a 97" long 6" dia. shaft made out of 4150 steel for a big electric fan, one of the specs is for the bearing areas to have no more than .00025 Mechanical and Electrical runout, what is electrical runout and how is it measured, some kind of special instrument we don't have I imagine.

  2. #2
    Forestgnome's Avatar
    Forestgnome is offline Stainless
    Join Date
    Aug 2008
    Location
    Californeeeah
    Posts
    1,149

    Default

    Might ask the question on this forum: http://maintenanceforums.com/eve/forums

    These guys know everything about machinery specs (not disrespecting anyone on this forum).

  3. #3
    fusker is offline Cast Iron
    Join Date
    Apr 2006
    Location
    Denmark
    Posts
    276

    Default

    Could they mean axial displacement between fan shaft and motor shaft? Works out to slightly less than one hundreths of a millimeter which I find an exaggerated demand. Is there a coupling of some sort to allow displacement or is it just a very stiff connection? Just my .02 Euros.

    When you find out, please post. I'm intrigued!
    Regards, fusker

  4. #4
    dfw5914's Avatar
    dfw5914 is offline Stainless
    Join Date
    Apr 2006
    Location
    Fort Worth, TX
    Posts
    1,286

    Default

    I think it has something to do with the magnetic properties of the shaft.

  5. #5
    JST's Avatar
    JST
    JST is online now Diamond
    Join Date
    Jun 2001
    Location
    St Louis
    Posts
    12,017

    Default

    I can think of several possible meanings, but none of them apply to the shaft alone. They would only apply to the shaft plus the rotor.

    I am supposing they refer to mechanical and electrical/magnetic balance, not just specifically runout.

  6. #6
    becksmachine is offline Cast Iron
    Join Date
    Aug 2007
    Location
    Spokane
    Posts
    310

    Default

    I suppose it is possible that they don't know what they are talking about. Or don't know how to properly specify what they want. Or is that the same thing??

    Dave
    Last edited by becksmachine; 08-27-2009 at 09:34 PM. Reason: Forgot rest of post!

  7. #7
    Join Date
    Nov 2005
    Location
    Maryland
    Posts
    6,842

    Default

    Quote Originally Posted by Cuda View Post
    what is electrical runout and how is it measured.
    Why don't you ask your customer?

    They're the folks who will test and accept or reject your work.

    - Leigh

  8. #8
    minder is offline Stainless
    Join Date
    Nov 2004
    Location
    Canada
    Posts
    1,765

    Default

    Quote Originally Posted by Cuda View Post
    what is electrical runout and how is it measured, some kind of special instrument we don't have I imagine.
    You need an electronic feeler gauge, but they are hard to come by
    Minder.

  9. #9
    L Vanice is offline Diamond
    Join Date
    Feb 2006
    Location
    Fort Wayne, IN
    Posts
    8,695

    Default

    The first question should be, what are the units? The .00025 could be inches, mm, feet, angstroms, farads, mmg or whatever.

    Larry

  10. #10
    GregSY is online now Diamond
    Join Date
    Jan 2005
    Location
    Houston
    Posts
    4,233

    Default

    I deal with this every day - it sounds like you are looking at an API requirement as that tolerance is common in many of their rotating equipment specs. It's hard to meet. Or rather, it's hard to meet if you have to guarantee it. Sometimes you'll hit it, sometimes you won't.

    Generally the tolerance is applied to the area of the shaft where the Bently Nevada (or other type) proximity probes will read - any imperfections in this area will be picked up as vibration.

    Mechanical runout is just what it sounds like - non-concentricity of the shaft. Electrical runout is caused by irregularities in the shaft steel that will be 'seen' as non-concentricity.

  11. #11
    Cuda is offline Cast Iron
    Join Date
    May 2005
    Location
    Alabama
    Posts
    492

    Default

    Quote Originally Posted by GregSY View Post
    Mechanical runout is just what it sounds like - non-concentricity of the shaft. Electrical runout is caused by irregularities in the shaft steel that will be 'seen' as non-concentricity.
    Thank you, that's the answer I needed, so in other words there isn't really anything I can do about it, the print did show the areas where it would be checked and it said something about burnishing it there, would that improve the electrical run out? We have no burnishing tools. But then again this is an emergency replacement shaft, so they may not be so picky about it!!!

  12. #12
    Carl Darnell is offline Titanium
    Join Date
    Jun 2006
    Location
    Taylorsville Ky
    Posts
    3,122

    Default

    Who in the world dreams up these outlandist terms? Other than to drive you nuts figuring it out, does it really mean anything different than the normal terms of trueness or tolerance would mean?

    The term "Electrical Runout" for machining sounds ridiculous to me and after gregsy's explanation it still sounds ridiculous.

  13. #13
    kenh is offline Titanium
    Join Date
    Oct 2003
    Location
    Bonners Ferry, Id
    Posts
    2,528

    Default

    To eliminate guessing,GOOGLE IT.

  14. #14
    Join Date
    Nov 2005
    Location
    Maryland
    Posts
    6,842

    Lightbulb

    One possibility is that they're referring to use of an electrical (electronic) profiling system.

    A device that measures capacitance can perform dimensional measurements with extremely high resolution and accuracy. The probe is placed very close to the work being measured, then the work is rotated on axis.

    Any change in the distance between the probe and the work is easily measured.

    - Leigh

  15. #15
    Toms Wheels's Avatar
    Toms Wheels is offline Titanium
    Join Date
    Dec 2005
    Location
    Jersey Shore
    Posts
    3,237

    Default

    Could them be a translation problem, as eliptical rather than electrical?

  16. #16
    3t3d is offline Titanium
    Join Date
    Nov 2004
    Location
    WI
    Posts
    3,855

    Default

    Quote Originally Posted by GregSY View Post
    Electrical runout is caused by irregularities in the shaft steel that will be 'seen' as non-concentricity.
    After reading that, it made perfect sense to me, and why the terminology is used.
    I'm interpreting it that the part may be subject to an electrical measurement for run-out/vibration. If the steel is non-uniform ( electrically) then the gauge will not readout correctly, and will not indicate run-out correctly.

    If the steel had various inconsistencies floating in it, it might be mechanically true, but will not readout correctly when measured electrically.

    But then again, I could be wrong.

  17. #17
    Join Date
    Nov 2005
    Location
    Maryland
    Posts
    6,842

    Default

    Quote Originally Posted by 3t3d View Post
    If the steel is non-uniform ( electrically) then the gauge will not readout correctly, and will not indicate run-out correctly.
    If the steel had various inconsistencies floating in it, it might be mechanically true, but will not readout correctly when measured electrically.
    Sorry... not true.

    The capacitance between two conductive plates is solely a function of the overlapping area divided by the separation. No other factors are involved.

    In particular, the composition and homogeneity of the materials do not enter into the calculation, provided of course that they can conduct electricity.

    - Leigh

  18. #18
    3t3d is offline Titanium
    Join Date
    Nov 2004
    Location
    WI
    Posts
    3,855

    Default

    Even for a magnetic probe?

  19. #19
    Carl Darnell is offline Titanium
    Join Date
    Jun 2006
    Location
    Taylorsville Ky
    Posts
    3,122

    Default

    Yep, google it here www.freepatentsonline.com/3986380.html

    After reading the whole looooong page I still don't know what purpose or effect electrical runout does or has but I know how it's found and corrected.

    I guess instead of the electric pencil you could use a chisel and hammer

    After reading the article it sounds like something Rube Goldberg would come up with.

  20. #20
    cnctoolcat's Avatar
    cnctoolcat is offline Titanium
    Join Date
    Sep 2006
    Location
    Abingdon, VA
    Posts
    2,173

    Default

    bearing areas to have no more than .00025 Mechanical and Electrical runout
    Wow! Good luck on holding that kind of runout on a 97" long shaft.

Page 1 of 5 123 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •