Powerful car jack linear actuator

Creating a powerful linear actuator by attaching a car jack to a motor is nothing new, but a lot of the demonstrations that I've seen neglect the fact that the point where the motor needs to mount to the jack (at the end of the threaded rod), will have movement both vertically and horizontally towards/from the middle of the jack. This makes it difficult to mount the motor in a fixed position.

So while this isn't a project in itself - it's a small part of a bigger project I'm currently working on, I thought I'd share my solution to this problem in case it is of use other others attempting something similar.


I found the best method is to focus on mounting the motor in relation to the threaded rod, rather than the jack, or the other frame/other parts of the project, as this is the only bit where the position remains relative.

The frame supporting the motor in line with the jack
(Jack body not illustrated)

This frame (yellow) goes around the middle of the jack, and hooks at the end over the threaded rod (green).

At the other end, the motor (red) is attached to the rod in order to turn it and mounted securely to the frame, allowing it to move with the rise and fall of the jack.


The downside to this mechanism is that the torque of the motor will cause the whole frame to rotate. This can be overcome by building the frame as close to the jack body as possible, to minimise the amount of rotation.


In addition, springs are mounted from the underside of the elevated surface to the frame, to add additional support and reduce vibration.

Electronically, the motor is driven by a H-bridge controller. Reed switches are mounted to the base - one on the base itself, another positioned in an elevated position to line up with the frame at it's highest point. Corresponding magnets are mounted on the frame, which line up with the reed switches to create a high level limit and low limit.

Control is currently provided by an Arduino with a single button input - each button press will either raise or lower the platform.

Code is below:

#define R_EN 13
#define L_EN 12
#define R_PWM 11
#define L_PWM 10

#define MAIN_SWITCH 4
#define LIMIT_LOW 7
#define LIMIT_HIGH 8


void setup() {
  pinMode(R_EN, OUTPUT);
  pinMode(L_EN, OUTPUT);
  digitalWrite(R_EN, HIGH);
  digitalWrite(L_EN, HIGH);

  pinMode(MAIN_SWITCH, INPUT);
  pinMode(LIMIT_LOW, INPUT);
  pinMode(LIMIT_HIGH, INPUT);


}

void loop() {
  if (digitalRead(MAIN_SWITCH)==HIGH) {
    runProcess();
    
  } 

}
void runProcess() {
  if (digitalRead(LIMIT_LOW) == HIGH) {
    while (digitalRead(LIMIT_HIGH) != HIGH) {
      lift();
    }
    freeze();
    return;
  }
  if (digitalRead(LIMIT_HIGH) == HIGH) {
    while (digitalRead(LIMIT_LOW) != HIGH) {
      lower();
    }
    freeze();
    return;
  }
}
void freeze() {
  analogWrite(L_PWM,0);
  analogWrite(R_PWM,0);
}
void lower() {
  if (digitalRead(LIMIT_LOW) == HIGH) {
    freeze();
  } else {
    analogWrite(R_PWM,0);
    analogWrite(L_PWM,255);
  }
}
void lift() {
  if (digitalRead(LIMIT_HIGH) == HIGH) {
    freeze();
  } else {
    analogWrite(L_PWM,0);
    analogWrite(R_PWM,255);
  }
}

Demo Video 

Mechanical Pencil

About a year ago, at Makers Central, I did a wood-turning tutorial and made my first pen.

Since then, I've added a mini-lathe to the workshop (purely because I lack the room for a full size one).

Just before heading back to Makers Central this year I thought it'd be good to have another go and see my progress.

Being me, I'm not really a fan of just constructing kits, and I always like to try and incorporate elements of upcycling and reclaiming into my projects.
 

I've had this ballpoint and mechanical pencil set for as long as I can remember - it's old to the point where you can see how faded the plastic has become. So there's the upcycling bit of the project sorted, this time I'm going to make a mechanical pencil to re-house the innards of this one.


The pencil is walnut and chrome - I wanted to try and keep the same shape as the pen I made last year, but use contrasting colours to the maple and brass that I used last time.
The metal bits came from a clicky pen kit, but were a good enough fit to work with the pencil mechanism.

So there we go. Making pens is enjoyable, but doesn't make much of a project, and I generally don't make more than one of the same item, so I don't see myself becoming a full-time pen turner any time soon, but I do have some variations of the theme that I might pursue.

View this post on Instagram

A walnut and chrome mechanical pencil, trying to match the shape and style of the pen I made a year ago. #diy #handmade #woodturning #woodworking #hardwood #walnut #maker

A post shared by Anthony (@darkmidnight_diy) on Jun 1, 2019 at 2:35pm PDT