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Motor Meltdown! WARNING: EXPLICIT IMAGES

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  • Motor Meltdown! WARNING: EXPLICIT IMAGES

    I have one of the Harbor Freight 6x12 surface grinders that come up around here every so often. I've had very good luck with it so far, I've owned it abotu 3 years, give or take.

    It's set up out in my barn, which is unheated. It's 25-30 degrees in there.

    So I'm out there grinding a thin steel ring down to thickness. The ring is about 1 3/4 OD with a 3/16 wall. The ring is .218 and I was bring it down to .210 (not in one pass!)

    About five or six minutes into the job the capacitor on the side of the motor lets out a little 'POP' and then starts to sizzle and smoke. I shut down the grinder as quickly as I could, and then I noticed the sexy little appendage growing out the side of the cap housing ...





    So my question is this... Do you think the cap crapped (sorry, couldn't help it) because of the cold weather, because I haven't used it in six months, or because it was just a crappy chinese capacitor and was bound to go sooner or later? You may not be able to see in the pictures, but it was literally wrapped in cut up newspaper! The NINGBO DAILY from May 4th 2007.

    The grinder has fewer than 10 hours of actual run time on it. The cap itself is rated at 40uf +- 5%, 370V, 50/60Hz. Manufactured by Kaihong Capacitor Company.

    Lastly, is there an alternate capacitor type (not electrolytic maybe?) that would be more reliable or suitable in this application (infrequent use, run in the cold)?

  • #2
    Almost any motor shop can supply you with a replacement. It's hard to tell what caused it to fail, just replace it.
    It's only ink and paper

    Comment


    • #3
      It's the papers fault.
      May the 4th be with you.
      .

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



      Comment


      • #4
        Originally posted by RobbieKnobbie
        I have one of the Harbor Freight 6x12 surface grinders that come up around here every so often. I've had very good luck with it so far, I've owned it abotu 3 years, give or take.

        It's set up out in my barn, which is unheated. It's 25-30 degrees in there.

        So I'm out there grinding a thin steel ring down to thickness. The ring is about 1 3/4 OD with a 3/16 wall. The ring is .218 and I was bring it down to .210 (not in one pass!)

        About five or six minutes into the job the capacitor on the side of the motor lets out a little 'POP' and then starts to sizzle and smoke. I shut down the grinder as quickly as I could, and then I noticed the sexy little appendage growing out the side of the cap housing ...





        So my question is this... Do you think the cap crapped (sorry, couldn't help it) because of the cold weather, because I haven't used it in six months, or because it was just a crappy chinese capacitor and was bound to go sooner or later? You may not be able to see in the pictures, but it was literally wrapped in cut up newspaper! The NINGBO DAILY from May 4th 2007.

        The grinder has fewer than 10 hours of actual run time on it. The cap itself is rated at 40uf +- 5%, 370V, 50/60Hz. Manufactured by Kaihong Capacitor Company.

        Lastly, is there an alternate capacitor type (not electrolytic maybe?) that would be more reliable or suitable in this application (infrequent use, run in the cold)?
        I'm not the motor expert here but it's likely that you just got a bum capacitor. It could have something to do with the low temperature, but I sorta doubt it since high temps are generally more damaging to electrical components.

        I don't know whether your motor has a centrifugal start switch inside. I'm just guessing that the cap simply gave out.

        If you can get a US made one in the same size, you would probably be better off. I recently bought a pair of Mars brand for start caps for my new RPC. They were advertised as Made in US but when I got them, they said Made in Mexico. What a nice surprise!

        The great preponderance of capacitors sold on eBay are made by Packard n China. They are OK but they have certainly flooded the market.

        You need to determine whether your cap is a start cap or a run cap. After that, just get the right physical size and capacitance. Might even take it to a motor shop and let them install the caps and test the motor.

        It just occurred to me that it was wrapped in newspaper since it was built only for "periodical" use. (pun intended).

        Comment


        • #5
          Carl: I plan to replace it... I'd just like to upgrade it to something a little more reliable, if possible.

          GNM: I'm assuming it's a start cap, it's the only one. Most motors with run caps that I've dealt with have 2 caps: one start and one run(not that I'm an expert - obviously)

          Thanks for the replies, guys. (except you, Mr Stevenson)
          Last edited by RobbieKnobbie; 12-15-2010, 06:10 PM.

          Comment


          • #6
            You may not be able to see in the pictures, but it was literally wrapped in cut up newspaper! The NINGBO DAILY from May 4th 2007.

            Lastly, is there an alternate capacitor type (not electrolytic maybe?) that would be more reliable or suitable in this application (infrequent use, run in the cold)?
            You need to make sure the new cap is wrapped in one of these LINK

            john
            John

            I used to be indecisive. Now I'm not so sure , but I'm not a complete idiot - some bits are still missing

            Comment


            • #7
              Originally posted by John Stevenson
              It's the papers fault.
              May the 4th be with you.
              HaHa,
              Yes, the Ningbo Daily is not a quality rag!

              Seriously:
              It must be a run cap because you were in 'run', not 'start' mode.
              One advantage of electrolytics is small size. You could replace it with polypropylene but it worked for 3 years so why not buy another one that fits in the same place and go from there.
              I'd go to an electric motor shop and pay what they want as long as they say they have good luck with the brand.
              Mike

              My Dad always said, "If you want people to do things for you on the farm, you have to buy a machine they can sit on that does most of the work."

              Comment


              • #8
                I just did some googling and found this: Start caps are typically in the 100's of uf while run caps are typically in the to's of uf. So that, plus the 370volt rating suggest it's a run cap.

                Live and Learn!

                Looking for a motor shop now; failing that I see Digikey has a few Run Caps with matching, or higher, specifications in stock. Gotta love the internet-age!

                Comment


                • #9
                  Can we assume for 100% sure the motor wasn't still in start mode?

                  Cold plus not running it for 6 months, maybe the grease had solidified and it never got up to speed in run mode?

                  Comment


                  • #10
                    I'm fairly confident that it was up to speed when it pooped... but you're right insomuch as Who's to say the centrifugal switch (if it has one) ever dropped out? it may be crudded up with frozen gooped up grease and kept the start circuit active!

                    I can say that I tried to start it up again (knowing that to be a bad idea) and even after I gave it a nudge by hand it just sat there and ran at about 10 or 20 rpm

                    Comment


                    • #11
                      You might be able to put that slag in your molding machine and make something useful out of it.
                      This product has been determined by the state of California to cause permanent irreversible death. This statement may or may not be recognized as valid by all states.
                      Heirs of an old war/that's what we've become Inheriting troubles I'm mentally numb
                      Plastic Operators Dot Com

                      Comment


                      • #12
                        Not to hijack this thread but there's two differnt comments on this thread that I thought were as good or better than the best standup comedy I ever heard. "May the 4th be with you" and "not a quality rag" Simply awesome.

                        Pete
                        Last edited by uncle pete; 12-15-2010, 07:00 PM.

                        Comment


                        • #13
                          duplicate post

                          Comment


                          • #14
                            So the chinese crap cap crapped. What else is news?
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                            Comment


                            • #15
                              Originally posted by darryl
                              So the chinese crap cap crapped. What else is news?

                              The real news is that you will have a difficult time finding any start or run capacitors that were not built in China.

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