DIY Linear Actuator for opening and closing 150kg Swing Gate

I’m in the process of making an automatic Gate Open/Close mechanism that can be operated through Home Assistant.

I’m stuck in the hardware part since I don’t know much about mechanics (yet). But I’m very interested and learning as I develop.

I found out that the best way to automate a heavy swing gate is using a ‘Linear Actuator’ however the cost of a single Linear Actuator is so high that I initially wrote off this project. However, recently it has become a necessity for me.

I tried to find articles on how to make a Linear Actuator and although they explain the construction part of it, none of these articles and videos explain how to choose a ‘Motor’ based on

  1. The weight it needs to push/pull
  2. The speed at which it needs to push/pull
    (I know it’s a rotary action but I don’t know the right terms so please correct me if the terms are wrong)

Ideally I would like the linear actuator to open the gate in around 10 seconds.

Would a NEMA23 30.61 kg-cm Single Shaft 1.8 Degree Hybrid Stepper Motor with a Shaft diameter of 8mm work?

Some additional information:
The stroke length is around 41.5cm (I’m using a 16mm thick threaded Rod mounted directly on the motor shaft)
It takes 83 revolutions for the threaded Rod to move a metal pipe (with a 16mm bolt welded on each end) from one end to the other

So I need the motor to move at 8.3 revolutions per second or 500 RPM

Would the stepper motor mentioned above be able to push 150kg at 500 RPM?

Or should I look at a servo motor or a stepper motor with other specification? I’m a noob when it comes to motors

what if you use a motor and a counter weight?
Then you wouldn’t need the motor to be very powerful :thinking:

So the counterweight reduces the stress on the motor when the gate swings one way but won’t the motor have to push the additional load of the counterweight when swinging the other way?

I might be wrong :sweat_smile:

the counterweight functions as a balance, so no…

I think you are confusing between a motor and a linear actuator. In simple terms, a linear actuator pushes & pulls while a motor turns something. There are three key parameters in selecting a linear actuator - stroke length, force, and speed. My basic guess would be that you will need a larger stroke length. You’ve already decided on the time to open - so the speed gets determined by that. The force required would be dependent on the lubrication of the gate so you’ll have to figure that out based on your requirement.

Ah Okay. I’ll look into this. Thanks :slight_smile:

Thanks for the information :slight_smile:

Actually what I mentioned initially was that I am making my own Linear Actuator since the cost of a prebuilt Linear Actuator is more than twice the cost of making it myself even if I overdo it with the motor.

The stroke length I need is around 41.5cm for which I am using a 16mm thick threaded Rod through a bolt welded in a metal tube. The threaded Rod will be attached directly to the motor shaft and as the motor shaft rotates, the metal tube will move forward/backward and in return pushing/pulling the gate.

My doubt was actually which type of motor and what specs should I look at to make a linear actuator that can open and close my 150kg gate in around 10 to 15 seconds :slight_smile:

I know that a stepper motor will do the job of pushing and pulling the 150kg gate but I’m not sure about the speed (rpm). According to my calculations, it will take 83 turns of the threaded Rod to Max out the stroke length. So for the gate to open in 10 seconds, the motor has to spin at around 8 revolutions per second or around 500 RPM.

Would the Stepper motor that I mentioned initially be able to push 150kg at 500 RPM? Or should I be looking at a different type of motor like Servo motors? (I’m not very knowledgable about motors)

Ah got it.

I don’t think the stepper motor will maintain its torque at 500rpm. You can also go with a regular motor with end stops which may give you better rpm-torque balance. You will lose the ability to open/ close the gate to a degree (you can always run the motor for partial time) but if you don’t need that anyway then a regular motor should do well (it may also be cheaper).

Thanks. That makes sense. I’ll try it out :slight_smile:

By ‘regular motor’ do you mean a ‘servo motor’?

Also what are the specifications I should look at when choosing a ‘regular motor’?

Amazon only mentions RPM values

I meant a AC/ DC motor w/o angle control. Typically servos that do full rotations are much more expensive. A good place to start would be to look into the e-bike DC motors - they have high rpm and also have good torque.

All the best for your project!

1 Like

Thank you so much.

Just one more thing. What should the torque value be? :sweat_smile:

Unfortunately I cannot help with that. It will depend on a lot of things - pitch of the screw threads, location where the actuator pushes the gate, amount of lubrication, etc. You should get the highest torque motor that your budget allows and test to see see if it meets your requirements.