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I need your help or advice. I need somehow to make a linear motion with stroke of 50 mm and starting force about 10N, the holding force after pull (stroke of 50mm) should be at least 20N. The holding state should be more then 12 hours continuously.

I was looking for some kind of linear solenoid (AC 230V/50hz), but at these parameters they are either big (overall size and also holding forces are needlessly big) or too expensive.

Do you have any idea or advice, how to solve this?

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    \$\begingroup\$ Have you considered a leadscrew and a simple motor? \$\endgroup\$
    – user16222
    Oct 27, 2013 at 23:11
  • \$\begingroup\$ Do you need to move only from one limit to another, or you need to maintain position in the middle of the range too? \$\endgroup\$ Oct 28, 2013 at 0:38
  • \$\begingroup\$ leadscrew considered, but for this kind of purpose (considering stroke and force) is imho too oversize and complicated solution I only need to move from one end to another. No need to maintain position within the range. \$\endgroup\$
    – user30962
    Oct 28, 2013 at 10:09

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Excellent question: I had the same question a while back and concluded that solenoids aren't the way to go. They generally only have a stroke of a few millimetres, they are expensive, and they require power to hold state.

Instead, what you want is a linear actuator. There are a lot of ways to build a linear actuator.

The simplest to implement is a screw drive, of some kind. An appropriately designed screw drive should be able to support 20 N easily (that's only 2 kg-force.)

enter image description here

Alternately, you can drive a gear rack with a worm gear. The benefit of this approach is that the gear rack is mechanically held in place by the worm gear, which provides your required holding force of 20 N for 12 hours without requiring any power.

enter image description here

The cam drive is OK but you would need to use a stepper motor to provide the required holding torque.

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If your movable element is mounted to a rail or slide you can achieve high force using a small motor with a gear box. On the gearbox you mount a round cam with an offset hinge point that then connects an arm over to your movable element. This scheme can be extended in several ways by introducing additional hinge points in the linkage arm so that the arm acts as a lever.

enter image description here

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