Help! Does this solenoid exist?

Discussion in 'General Electronics Chat' started by Desperado213, Jul 14, 2015.

  1. Desperado213

    Thread Starter New Member

    Jul 14, 2015
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    Hello everyone! So I'm working on inventing something and I have slowly figured out that a push solenoid would be best for said invention but I'm not sure if what I need exists or can be made.

    So I need a push solenoid that is:
    1. Tubular not exceeding a diameter of .48in
    2. Has a stroke (I think that's what it is called) of a half inch
    3. Needs to be able to push 5lbs
    4. 12 or 24vdc whichever will work best.

    I don't know if that is possible but I figured I would ask. I am by no means well versed in circuits and solenoid or any small electronics so don't beat up on me too bad. This part would be used to give a very quick momentary pulse extending the full half inch and then retracting back.

    Also if you think a different mechanism could fit the bill then please tell me.

    Thanks for any help!
     
    Last edited: Jul 14, 2015
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
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    That's a hard find.
    Allied search results
    Digikey search results
    Everything I found close to those dimensions (smallest was .75" dia) is a pull-type. Everything that's a push type is in a square frame much larger than .48".
    looks like you'll need to make your own, good luck!

    P.S.
    Your "5 lbs" push might be a problem too. Solenoids are not linear in their force. A solenoid might have 5lbs force at end-of-stroke but not at beginning, or vise versa.
     
  3. MaxHeadRoom

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    Jul 18, 2013
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    A 5lb effort for a solenoid 1/2" in dia is somewhat excessive, if only a low duty cycle, you could look at a small pneumatic cylinder using a air brush compressor etc.
    The other would be a small motor operating a small dia threaded rod.
    Also dependant on the speed of operation required.
    Max.
     
  4. strantor

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    I thought so too, but this one does just over 5Lbs.
    ...BUT that's a .75" dia, AND it's a pull-type, AND the 5Lbs is only good for one end (at the other end it's only 6oz), AND it's only intermittent duty.
    So, totally not what the doctor ordered. But what the doctor wants doesn't exist to my knowledge.
    I agree with your suggestions; something other than a solenoid will be needed.
     
  5. Desperado213

    Thread Starter New Member

    Jul 14, 2015
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    Thanks for the quick responses! I figured that 5lbs would be pushing it and I thought about going the small motor/threaded rod route but I don't think it would be quick enough. Also a pneumatic cylinder is a good idea but this is going somewhere with very very limited space so I may not have room for that.

    Strantor, how would I go about making my own? I'm pretty good at making things and pretty handy so I would be up for giving it a try.
     
  6. MaxHeadRoom

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    Torque is equal to current, so you would need one with sufficient torque for the task, A DC solenoid etc has the most attraction when the armature is fully engaged, you may want to look at an AC version, These have very high initial current before the point of full engagement. They are trickier to make, but the fact that you only need a momentary pulse may exclude the need for a retaining shading ring.
    They are wound with much less copper so the dia can be kept low.
    IOW very high current for a brief time.
    It may be something that would be fairly easy to experiment/try.
    Max.
     
  7. Desperado213

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    Jul 14, 2015
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    That sounds like something that would work perfect unfortunately it has to be battery powered. So I guess choosing the right type of batteries would also be a factor.

    As I think more about the small motor/threaded rod idea, it may be able to work. I would just have to make the thread of the rod longer so that 1 full motor turn extends it the rod the .5in I need. Do they make motors .48 diameter or smaller that are also strong enough?
     
  8. MaxHeadRoom

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    Does both motor And rod have to be 1/2"?
    What speed do you need to operate at? if you can do it with the maximum of turns, the better, (more torque).
    There is also a problem of end of stroke that requires the motor to be turned off, if left on longer than necessary the motor will present almost short to the battery.
    You may want to look at Li-Po for higher power.
    Max.
     
  9. strantor

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    I seriously doubt it. I'll leave the search up to you this time, but you should recognize that you're asking an awful lot from the physics god.
    Unless you have the ability to make your own threads (a lathe) you're going to be stuck with standard lead screw pitches. The smallest of those that I know of is ACME lead screw 1/4"-16TPI. That means 8 turns for a half inch extension, which should be a lot more doable for the tiny motor anyway. The standard lead screw pitches (like 1/4"-16TPI) are chosen as standard because they are reasonable pitches that reasonable motors are capable of turning. You would need something like a 1/4"-2.0TPI which is neither standard, or reasonable.
     
  10. Alec_t

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    What is the maximum allowed time for the 1/2" movement?
    For a lead screw, would ordinary threaded steel rod, or a bolt, do (e.g. M4)? That has a fine pitch, so even a small motor should have enough grunt if , say, half a second is ok for the movement.
     
  11. Desperado213

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    Jul 14, 2015
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    Alec, it would need to extend the 1/2in and then retract it within a half second max.
     
  12. MaxHeadRoom

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  13. Desperado213

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    Jul 14, 2015
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    That looks perfect! Thank you I'm going to look into that.
     
  14. sirch2

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    Jan 21, 2013
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    I haven't done the maths but I doubt a single turn thread for 1/2" travel on 1/2" dia bar would move at all. All the effort would be trying to rotate the bar not move it forwards
     
  15. MaxHeadRoom

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    The torque required can be calculated, a rotated lead screw is a class 1 lever.
    Max.
     
  16. strantor

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    Here are some google keywords:
    Linear actuator
    Tubular actuator
    * combined with variations of * :
    micro, mini, miniature, etc.

    I didn't find anything that meets your dimensional requirements.
    Everything I found that meets your torque/speed requirements is too large.

    You may be forced (I think you are at this point already) to consider other solutions.
    For example, a pushrod. If in fact, as I strongly suspect, there is simply not any way to cram that much power into the small space, you could utilize a larger linear actuator, affixed to the outside of your top secret apparatus, with a long pushrod extending inside to a plunger which fills the space that your solenoid would have filled.
    Or, a flex-shaft, like a speedometer cable. Same concept, mount a larger motor outside, with a flexible rotating drive shaft/cable going into your enigma machine, where it is coupled to a lead screw. The lead screw fills the solenoid void.

    The maximum push force is 4.2 Newtons.
    OP requires 5Lbs = 22 Newtons.
    So this device would need to be over 5X as powerful to meet that.
     
  17. cmartinez

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  18. MaxHeadRoom

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    The remote wiper motor may be an option where the rotary motion is translated to an oscillating motion of a flexible cable. Fairly high torque and the transition distance could be adjusted.
    Max.
     
  19. Gdrumm

    Distinguished Member

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    If your are just moving something light weight, from point A to point B, then an actuator will do nicely.
    But 5 lbs. is not light weight, when given your parameters of size.

    If you are moving something with a specific heavy mass, then that would need to be added to the calculation.
    The inertia would be the key, and adding mass would either slow you down, or speed you up (depending on the direction of thrust relative to gravity).
    If its a worm gear acutator, there will be stresses at the beginning and end of stroke as well.
    A cam actuated device could mitigate the stresses for stroke (starting and stopping).
    You didn't mention if a dwell time would be required in either direction.

    Without disclosing the heart of your emigma, could you provide more details on exactly what it must do to accomplish the task?
    So far, we only know that it must travel 1/2", in x amount of time, and it must move 5lb.
    What is the repeatability, what is the delivery offload, what is the initial onload, what is the cycle time between deliveries?

    If it is a one time event, like launching a rocket to the moon, then an explosion of some type would achieve that.

    Can you use a pnuematic actuator? Pneumatics on one end, with a heavy duty spring return might do that.
    Mac valves move all kinds of things in industry.

    HTH
    Gary
     
  20. cmartinez

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    I'd definitely also vote for pneumatic, if the TS has compressed air available.
    EDIT: on the other hand, he'd also have to consider deceleration and possible impact and vibration factors.
     
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