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Thread: PSFK 4002 meltdown

  1. #1
    Join Date
    Oct 2014
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    51

    PSFK 4002 meltdown

    On a different site the guys are talking about endbells melting down. Since I have seen a few motors have the bushing come lose in the motor, I think it is sliding down onto the brush hoods causing a short and tons of heat.

    They have a theory about small coms and stuff. I believe they are over thinking the problem.

    Sent from my SM-N910V using Tapatalk

  2. #2
    Join Date
    Jun 2002
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    Wellington, New Zealand
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    4,374
    Your theory is impossible. The motor would have to come out of the chassis for that to happen.
    Zippity

    Wellington Slot Car Club's home page

    "Rules are written by FEAR; and that Racers are motivated by the Fear that somebody may have something that gives others an Edge." - Rocky Russo

  3. #3
    Join Date
    Jul 2011
    Posts
    386
    I've never had a 4002 FK apart. Is there phenolic material at the end of the commutator?

  4. #4
    Join Date
    Sep 2014
    Location
    Auckland, New Zealand
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    279
    Quote Originally Posted by lee.palmer.522 View Post
    On a different site the guys are talking about endbells melting down. Since I have seen a few motors have the bushing come lose in the motor, I think it is sliding down onto the brush hoods causing a short and tons of heat.

    They have a theory about small coms and stuff. I believe they are over thinking the problem.

    Sent from my SM-N910V using Tapatalk
    Lee

    Slight problem with your theory, there is a commutator that gets in the way of the bushings journey towards the brush hoods.

    See the below image, I have shoved the end bell bush in as far as it will go but its sitting on the washer on the end of the comm and a long way from having any chance of touching the hardware



    Swodem
    Last edited by swodem; 05-01-2017 at 04:25 AM.
    listen, study, spy, try, research, invent

  5. #5
    Join Date
    Feb 2005
    Location
    Chesapeake, Va.
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    738
    The reason the end bells melt is usually caused by a loose bushing that spins inside its bore creating heat by friction and deforming the end bell. This has happened over the years because the bushing is only press fit into the end bell. If the bushings were epoxied in it wouldn't happen. I glue all my sealed motor bushings in using a new bottle of super glue. It's not the best fix but on a sealed motor there's not much more you can do. I use a new bottle of super glue because that is when it's at the thinnest and strongest, it flow better around the bushing before it sets. Then I place a bead of Gorilla super glue, it's a thicker super glue, around the edge of the bushing to help bond it to the end bell.

    The arm in the motor in post #3 is sitting high in the can. You can tell by the space above the brush path. I've had motors where the arm was sitting so low in the can that there was no discernable space above the brush path, the top of the brush was actually riding at the top of the comm. Although this doesn't confirm the theory that the bushing could make contact with the hardware it does bring it closer.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  6. #6
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    Sep 2014
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    Auckland, New Zealand
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    Guys prob the best thing you could do is read the thread mentioned and look at the pics posted.

    1. Then you would see that there is no problem with the bushing having either fallen in deep or being so wobbly it causes heat - remember these cars melt down at standstill, when power is applied after stopping



    2. The arm shows it has not been running high or low



    It's good you're thinking and coming up with ideas though.


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  7. #7
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    Feb 2005
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    Chesapeake, Va.
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    738
    Look very close at the brush path on that arm in post #6 and you can see it was riding very high in the can, so high that the bottom of the brush may have even touched the cut stop on the comm. If that is the case then this arm was putting a lot of pressure on the end bell bushing and could have caused it to spin. That doesn't account for the spring post screw bore melting. I've never had that happen on any motor.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  8. #8
    Join Date
    Sep 2014
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    Auckland, New Zealand
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    This whole thread and the one on slotblog is about endbells melting and hardware falling out because of the heated screws....not about spinning bushes


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  9. #9
    Join Date
    Oct 2014
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    51
    Quote Originally Posted by swodem View Post
    Lee

    Slight problem with your theory, there is a commutator that gets in the way of the bushings journey towards the brush hoods.

    See the below image, I have shoved the end bell bush in as far as it will go but its sitting on the washer on the end of the comm and a long way from having any chance of touching the hardware



    Swodem
    Mine touched the brush hoods. Straight short.

    I did take one apart that had a significant arc spot on the Com. Where one pole was engaged by both brushes.

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  10. #10
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    Feb 2005
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    Chesapeake, Va.
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    The main problem is the arm positioning in the can and that is mostly dictated by the magnet location. If the arm rides high in the can there is no chance a loose bushing will touch the hardware. The only problem that could happen is that the bushing will have too much pressure on it and if it does get too loose it could spin in its bore. While this can cause excess friction and can cause the bushing bore to melt it wouldn't cause the screws to get so hot that they would come out of their threaded bores. However, if the arm is riding so low in the can that the top of the brush is above the top of the comm. then it's possible that a loose bushing could make contact with the brush hardware and cause a direct short. With respect to the arm in post #6 I would say that the arm was riding excessively high in the can causing too much pressure on the bushing and maybe even making contact with the comm. cut stop. That could cause the arm to overheat, and looking at the comm. it did, but it wouldn't cause the problem with the hardware. We all know how to fix the brush overlap problem but if local rules don't allow cut brushes you just have to make sure the brush hardware is aligned properly and hope for the best. These are very low cost motors so why have high dollar expectations? Unless local rules allow blueprinting of these motors you'll have to live with what you get.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  11. #11
    Join Date
    Jun 2002
    Location
    St Charles, Illinois, USA
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    2,234
    My own experience indicates that the magnet placement has better quality control than where the commutator is placed on the shaft. I have had several puppy dogs bushing failures and the FK has the same problems. Gluing the bushing is a good move to avoid in-race failures. I had many motors that have had way too much endplay that could allow the bushing to pop out of the endbell. This usually leads to massive meltdowns of the hardware area when the armature rubs on the magnets.
    l.d. kelley, M.A. Ramcatlarry@aol.com

    50 year pin 1959-2009
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  12. #12
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    Dec 2009
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    Philly
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    Wow just had a brand new one almost melt down. I took it out of the bag and put it on the power supply at 3V. Switched to Amps to see what it was drawing and gasp, it's was 8A!! Started to smell and see smoke, shut it down and burnt my fingers unhooking the leads. Houston/ProSlot we have a problem. Anyone have any luck with returns to ProSlot?
    [SIGPIC][/SIGPIC]
    My other car is a Manta Ray

  13. #13
    Join Date
    Dec 2009
    Location
    Philly
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    206

    Meltdown avoided

    Wow just had a brand new one almost melt down. I took it out of the bag and put it on the power supply at 3V. Switched to Amps to see what it was drawing and gasp, it's was 8A!! Started to smell and see smoke, shut it down and burnt my fingers unhooking the leads. After it cooled I took a close look at the brush hoods. Seems to be lip on the top of the hoods on the inside. Maybe when the arm spun up they touched the bushing and started shorting?

    Houston/ProSlot we have a problem. Anyone have any luck with returns to ProSlot?
    Last edited by fatbear; 06-23-2017 at 06:56 AM.
    [SIGPIC][/SIGPIC]
    My other car is a Manta Ray

  14. #14
    Join Date
    Jun 2002
    Location
    St Charles, Illinois, USA
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    always check rotation direction when running in a fresh motor. There IS enough timing advance to generate excess heat if you run it backwards instead of forward.
    l.d. kelley, M.A. Ramcatlarry@aol.com

    50 year pin 1959-2009
    Racing slot cars in America
    USRA 2009 member 0028, 2017 #404
    IRRA, ISRA/USA, Hardbodies 1/24 & 1/32
    retired raceway owner(for now)
    Omni/Cidex service center

  15. #15
    Join Date
    Sep 2014
    Location
    Auckland, New Zealand
    Posts
    279
    Yep and these connect up OPPOSITE to many other motors...FK have positive to the rear (axle side) of the can


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