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Making a Powerful Solenoid

Discussion in 'General Electronics Discussion' started by Xyius, Apr 10, 2016.

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  1. Xyius


    Apr 10, 2016
    I am trying to make a solenoid. I would like it to be fairly powerful, and by that I mean, perhaps a couple pounds of force. This is what I have done (and it didn't work so well.)

    1. I bought some nylon rod as well as 34 gauge magnet wire.
    2. I turned the nylon rod to be a spool on my lathe.
    3. While the newly made spool was in the lathe I rigged up something to allow me to wrap the magnet wire around it while it was spinning.
    4. I bought some "soft iron" with supposed permeability of 50,000 and turned a plunger out of it on the lathe.
    5. When I was done wrapping, I measured the resistance to determine the maximum current I could put through it and powered it with enough voltage to be roughly 65% of that (the max current was like 50 mA since the gauge is so small). I also calculated a rough number of turns. It was a little shy of 8000.

    The solenoid was very weak. First I tried it with a bolt, and then with the plunger I made and it performed the same. Where did I go wrong? Was it naive of me to think I could make a powerful solenoid this easily? I once heard you're supposed to wrap the wire very orderly with no overlap over loops. Is this correct? Is it because I need thicker gauge wire? I have used commercial solenoids that pull a couple amps. What gauge is typically used?

    Thanks for any replies!
    Last edited: Apr 10, 2016
  2. Minder


    Apr 24, 2015
    I'm not really surprised, 34g wire and 50ma?
    When talking lb of force pull you will be looking at a number of amps required.
    At least 16g or more IMO.
  3. Colin Mitchell

    Colin Mitchell

    Aug 31, 2014
    Increase the voltage and see what happens.
  4. Bluejets


    Oct 5, 2014
    By my estimation, and I could be a way off here as very little info supplied, you've used about 300 metres of 34 g wire on say a 12 mm spindle.
    8000 turns gives maybe 250R.
    With 50ma that then gives a supply around 12.85v and a total wattage of about 0.65W
    Not a lot of power given 1HP = 746W.
  5. 73's de Edd

    73's de Edd

    Aug 21, 2015

    Sir Xyius. . . . . . .

    I . . . .and others for sure . . . . . .are still looking for a bunch of initial information which was not even touched upon.

    What will the solenoids operating voltage be ?.
    Is the solenoid to be used for just a short pulsed operation or for longer duration or . . .forbid . . . for sustained operation ?
    What are the physical SIZE of construction constraints, if any ?
    Considering the core of the solenoid to be the same length as the coil windings width, how far will the core be pulled out to be in its normal resting
    Give the dia of the core and its length.

    Note that this unit below . . . . optimally has the core coming out about 1/2 length and then pulls in to center within the coil.

    73's de Edd

  6. Xyius


    Apr 10, 2016
    Bluejets: That is a pretty good estimation! All of the numbers are pretty damn close.

    73's de Edd: The solenoid I want to make will have an intermittent duty. It will be used to push open a poppet valve on a small engine I am building. I would like the operating voltage to be 12 volts. The solenoid doesn't have a strict size requirement but I am making it 2 inches long with a plunger that is 1/4 inch in diameter. I would like the core to push out about 3/16", maybe 1/4" max when powered. The resting, unpowered length it sticks out is not strict at all.
  7. duke37


    Jan 9, 2011
    The solenoid in #5 has a steel box to add to the magnetic circuit. If your magnetic circuit is mostly air then it will be very weak. The force will vary with the position of the core.

    I would think you could go up to 10W on this size without too much heating.
  8. Alec_t


    Jul 7, 2015
    To get the force you want over a reasonable distance you'll probably need something about this size, drawing 2A or so.
  9. Xyius


    Apr 10, 2016
    Thank you! I knew I was missing a key piece of information. What you say makes sense to me. I didn't even consider the magnetic circuit of the solenoid.

    My plan now is to get some thicker gauge wire that will allow me to run a couple amps through it, as well as make a housing around it to reduce the reluctance of the magnetic circuit. I will make this out of cast iron since I have some round stock on hand. So instead of a box it will be cylindrical in nature.
  10. Bluejets


    Oct 5, 2014
    In my experience with model engine building ( a bit off topic I know) but , valve opening requirements are approximately 1/8 of the diameter.
    Any more than this is just a waste and in the application it would create problems as the revs increase to have the valve open for so long.
    So, 12mm diameter valve would need approx. 1.5 to 2 mm maximum opening distance.
    There is also a gentleman from the UK if I remember, had made electronic injection (follows the same principal) using solenoids so I'll see if I can find it.
    Was a few years ago now but worked ok.
  11. Xyius


    Apr 10, 2016
    I forgot to mention that the engine I am building is a steam engine, not an internal combustion engine (I am very much a steam enthusiast). However I would still love to see any kind of engine that uses solenoids for valve timing if you can find it!
  12. Bluejets


    Oct 5, 2014
    Found it............
    Mate of mine used the injector solenoids so got a bit confused there as it was a while back.
    Anyhow, the electronic valves engine is here.... .......................

    Cheers....... Jorgo
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