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Homemade starter relay sticks

Discussion in 'General Electronics Discussion' started by swagguy8, Feb 12, 2015.

  1. swagguy8

    swagguy8

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    Dec 10, 2014
    Hey guys, I made a starter solenoid for my boat cuz im a cheapo. i made it from a push-pull solenoid, and couple brackets and screws. when i start the boat, the 90A of current tack the starter uses welds the cast iron contact points together, making me have to pull the plug on the starter. is there some better material i could use that has a higher melting point?

    thanks
     
  2. shrtrnd

    shrtrnd

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    What do they use on an automobile starter relay? Can you salvage those contacts from a junked automobile starter?
     
    KrisBlueNZ likes this.
  3. swagguy8

    swagguy8

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    Dec 10, 2014
    i don't really know, and where i live, theres next to no junkyards (seattle area washington)
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Starter motors pull hundreds of amps I believe, and they're inductive. A normal relay won't cut it. You need something called a contactor, I think, which is just a big relay with contacts that are strongly forced together and pulled apart. That's all I know (or think I know), sorry. Other members will probably have suggestions; just wait 12~24 hours.
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    You will never replicate the material required for this.
    Just buy a starter solenoid.
    Your 90 amps would be a rather conservative estimate, try perhaps 3 or 4 times more.
     
  6. swagguy8

    swagguy8

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    Dec 10, 2014
    i'm using an industrial solenoid, the same ones they use to control flow in pipes. i believe that those are way stronger than the ones they use in starter solenoids. my boat's motor isn't anything big, just a 600cc outboard. according to here: http://www.garelicksteel.com/pdfs/Melting_Points_of_Common_Metals.pdf
    would carbon contacts salvaged from a motor work?
     
  7. Bluejets

    Bluejets

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    Copper can be used but it will also stick unless coated with, for example, silver.
    The contacts must be arranged as a wiping motion to remove oxidation deposits which can cause arcing and eventual sticking also.
    Some materials you may consider for the coatings of the contacts.....

    Silver, Fine grained silver, Silver-Nickel, Silver-Iron, Silver-Graphite,Silver-Cadmium Oxide,Silver-Tin Oxide, Gold or Platinum
     
  8. duke37

    duke37

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    Jan 9, 2011
    The starter solenoids that I have seen have two copper bolts side by side. The cables are connected to the bolts and there is a copper disc which is forced against the heads of the bolts to connect them together. A strong spring separates the contacts so the solenoid needs a lot of current to operate.

    A used solenoid will have eroded contacts indicating the heavy duty. Surely you must have scrap yards in your location, what do you do with scrap cars or lorries? You could also go to a auto repair company which may have a solenoid from a burnt out motor.
     
    KrisBlueNZ likes this.
  9. swagguy8

    swagguy8

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    Dec 10, 2014
    nah, there aren't any scrap yards within 50 miles of my location because most people who can afford to live in my area sell their car before it gets too old, so not many cars make it to scrap yards. There are some in seattle, but they're import cars and i don't want to spend time in trying to find the solenoid.
    i kinda figured out the problem, the contact points are ring crimp terminals, and im pretty sure those are made from lead or cheap iron. so i relocated the ring terminal, and now the contact points are hex nuts and a construction bracket.
     
  10. shrtrnd

    shrtrnd

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    OK, I guess. Take a look at them after a few uses. Fastening hardware (hex nuts) can be made from, or coated with, a wide variety of metals. You may have installed a type that'll work well for you, or you may have
    installed a nut made of an alloy that will not last. Good luck with the project.
     
  11. 12vdc

    12vdc

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    Apr 13, 2011
    IF you decide to get a factory solenoid a generic Ford replacement (1965-1985) should sell at parts stores for $6 -$10. (and yes the Ford version uses the 2 copper "T" head bolts connected by a large copper washer and rated for 300 and more amps)
     
  12. Tha fios agaibh

    Tha fios agaibh

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    You could go into an Auto parts store and ask if they would sell you scrap bendex contacts from their starter core pile. They'd probably say help yourself but don't make a mess.
     
  13. 12vdc

    12vdc

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    Apr 13, 2011
    A starter Bendix(brand name) for a "starter drive". It consist of a drive gear attached to a sprague (one way clutch) which rides on the motor's main shaft. There are no electrical contacts. You must mean "solenoid" which on most newer cars is the combination solenoid (to engage starter drive with the flywheel or flexplate) and the relay which completes the electrical connection between the battery and the starter motor. It has the contacts, the washer and 2 contact bolts.
     
  14. Tha fios agaibh

    Tha fios agaibh

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    You'r right. I know the solinoid is the coil part, but I always generically called the rest of the guts the bendix. I was referring to the contacts the solinoid engages.
     
  15. Kiwi

    Kiwi

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    Why mess around trying to build something that might work, when eBay has heaps of suitable solenoids that are dirt cheap?

    Safety on the water is important, so don't risk your, or your family's, safety by taking cheap shortcuts.
     
    swagguy8 likes this.
  16. swagguy8

    swagguy8

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    Dec 10, 2014
    i'm literally a full on mechanic/electronic person, and solenoids aren't really hard to hot wire. i'll probably find something on ebay soon enough. in the meantime i'm gonna use the DIY one that i made :D
     
  17. davenn

    davenn Moderator

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    Sep 5, 2009
    with your responses so far, I find that extremely hard to believe :)

    D
     
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