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Thread: Spring tension on the brushes

  1. #1
    Join Date
    Jun 2011
    Location
    Rotterdam, The Netherlands
    Posts
    64

    Question Spring tension on the brushes

    HI all,

    I have a question about motor springs. I have tried to to search for my answer but I'm still not satisfied.... My question is the following.

    When I free run a motor at 4 volts on my test bench and start fiddeling with the spring tension by for example using a needle lessening the tension on the brush the motor runs faster or at least I think that becasue the pitch is higher.

    I replaced the box spring with champion light springs but it seems like they have even more pressure to the brushes causing my motor to heat up.

    Is there a way to fine tune the springs? so that they apply the right amount of pressure?

    Motors I tried are Hawk and Proslot MK1.

    Thank you for your advise it is highly appreciated!

    Robin

    The Netherlands

  2. #2
    Join Date
    Mar 2009
    Location
    Everett, Wa.
    Posts
    537
    If you tune the springs at the tension at 4 Volts and run at 12 volts the brushes will float/bounce, arcing and accelerating the wear rate.
    What you did was find the optimum for a free running motor at 4 volts. To run at higher RPM (higher voltage) you need more spring pressure.
    So you would need to run your experiment at 12 volts/race voltage, which is not advised usually due to destruction of the windings or Comm.

    Hence it is best to track tune with various spring pressures which give you the best lap times or best life etc.
    Guy Middleton
    Everything I was taught in Engineering school I had already learned from slot cars....

  3. #3
    Join Date
    Feb 2005
    Location
    Chesapeake, Va.
    Posts
    597
    Do you run the Champion springs as they come out of the bag? If so you may have to tune them. I'm guessing that your using a Fiddlestick to set equal spring pressure. Try this. Take 3 sets of springs and bend them to look like the hands of a clock. One set at 3:30, one set at 2:30 and one set at 1:30. See which set produces the least amount of heat. You may have to bend the short leg to get the settings. Here's one more thing you can try. Cut the short leg of the positive or front spring so that it only catches half or a little less than half of the brush. Then take the negative or rear spring and bend the short leg (do not cut this one) so that it makes most of it's contact with the far side of the brush. This seems to reduce arching and heat. See if that helps any.
    I've done so much with so little for so long it seems like I can do anything with nothing at all.

  4. #4
    Join Date
    Jun 2002
    Location
    Fall City, WA
    Posts
    1,465
    The most accurate way to tell the tension on a spring is to use the Xipp Motor Spring Dyno. It very accurately shows the tension of each spring allowing you to tell when you have them even. HOWEVER, IMHO as soon as you put it on the motor, you are changing the tension you have set. Nice catch 22 there!

    If your springs are close, they should work "good enough"
    Gary Johnson

  5. #5
    Join Date
    Jun 2002
    Location
    NorthWesterner now in Philippines
    Posts
    7,798
    Copied from Sonic's web site:

    http://www.sonic-products.com/tools/

    The Fiddlestick





    One of the most important areas of race preparation is checking your brush spring tension. We’ve found that all brush springs vary in strength, even from the same batch, and a major source of armature failure is weak or uneven brush springs. The Fiddlestick will help prevent these disasters.

    A Fiddlestick will improve your results and help protect your motors. It’s made from anodized aluminum so it’s tough enough to take the abuse it will get in your pit box, and then we laser mark it with crisp, clear numbering for easy reading.

    A Fiddlestick is very easy to use, just put the plunger notch against the end of the spring you want to check and push until you just lift the spring off the stop, (in an assembled brush/spring setup) and then take a reading on the Fiddlestick scale.

    If the reading is what you want-fine you’re set. If not, bend the spring and recheck. Repeat as necessary until you get the desired reading.

    (TIP: Once you find what spring tension works on your setup make up some extra sets at the same Fiddlestick reading and keep them in your slot spares box in case you need to rebuild a motor at the track.)

    #50-1 The Fiddlestick $17.50 / ea. *DISCONTINUED – LIMITED TO STOCK ON HAND


    If you don't have a Fiddlestick - best to get one now, as they may be getting hard to find.
    - - - - - - - - - - - - - - - - - - -
    Paul Kassens
    OWH Slot Car Talk "Mom"
    The Old Weird Herald
    email: paulk@oldweirdherald.com

    - - - - - - - - - - - - - - - - - - -

  6. #6
    Join Date
    Nov 2003
    Location
    Koria Finland
    Posts
    235
    It's a cheap substitute for this which I have because of my job....

    Well, have fiddlestick, too - think it's nearly 40 years old?
    zipper

  7. #7
    Join Date
    Jun 2011
    Location
    Rotterdam, The Netherlands
    Posts
    64
    Thank you all for replying. I will buy some new springs and go with Fast Freddie's advise for now and maybe later will go the fiddle stick way.
    Slot Race Club Midden Nederland
    http://www.scmn.nl/

  8. #8
    Join Date
    Dec 2007
    Location
    NH.
    Posts
    1,381
    Robin,
    If you stick with the Champion light springs you'll find that they are very close/matched tention right out of the package.
    Very seldom do I need to do much adjusting on them. I also use a fiddle stick for checking my tentions.

    Guy is right, if you tune your springs for 4volts things can and most likely will change at higher voltage. However I've very seldom ever had any
    problems with Champ springs. I,ve also had good luck with Camen springs in the past.

    Vic
    Keep your finger on the trigger ,and your eye on the slot

  9. #9
    Join Date
    Jun 2002
    Posts
    553
    Here is something I used to make and have not made in a couple of years. You'll need a Fiddle Stick, but it's much easier to do on a fixture than on the motor.
    Why make it tougher than it really is?
    e-mail: scrgeo@comcast.net

  10. #10
    Join Date
    Jun 2011
    Location
    Rotterdam, The Netherlands
    Posts
    64
    Very nice setup RickB thanks for sharing.
    @trickyvic3 I will keep that in mind.

    thanks
    Slot Race Club Midden Nederland
    http://www.scmn.nl/

  11. #11
    Join Date
    Jun 2009
    Location
    New Jersey
    Posts
    1,389
    I have a fiddle stick for a lot of years now never really like it I use a xipp spring dyno that I got from proformance racing 2 years ago and love it you can get your spring to match extactly and also ajust tension and match them with no trouble.
    Motors By Mic B
    Balance By Bill Bugenis
    A Clean Slot Car is a Happy Slot Car
    Garden State ISRA Club Home of the Anaconda
    Tires by the Hermanator
    www.TheISrausa.com

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