Frame mechanical assembly

Now everything is painted and cleaned it's ready to go together.
I don't yet have the motor mounting plate or shaft adapter but the frame can go together and I'll find out how much space there really is for the motor.

This is the lower arm assembly, just the hinging arm sitting on the coils. 

I decided to make up a timber stand to hold the upper frame off the floor. This has made things a lot easier to work on. So now the gearbox is in place held by just one mount on the left hand side, the drive shafts aren't in properly yet as I've just remembered that I need to buy new oil seals so the drive shafts are just hanging in place for now. With the motor spaced as intended with the proposed mount plate it really does only just fit, this is purely a stroke of luck as it didn't occur to me that the motor was going to be longer than the original engine, fortunately the CAD model came out just about right which is useful to know. 

So now I know it's all fitting I need to make up the motor-spline connection and wait for the motor mount to be machined. I've ordered the seals, didn't seem any point in ordering smart ones so I've ordered standard 40ID x 60OD x 10 wide R23 seals which are identical but only £3 each. 

Now I can work out how to mount the motor to the two engine mount points, looking forward to wiring the motor now for the first test run. 

Converting the sub frame from a Fortwo 450 to a Roadster 452 frame

One of the early things I checked on was is a 450 frame suitable to use for a roadster.. and it was apart from two things;

• The handbrake cable points forwards to connect the the handbrake in the Roadster whereas it points up on a fortwo. 
• The Roadster doesn't use the anti-roll bar that normally comes with the fortwo frame. 

So the anti-roll bar job was very easy and just involved cutting off the brackets..

The handbrake cable mod meant cutting off the old bracket and making a new one that points forwards, I knew what it should look like from my exiting Roadster so I managed to make a new bracket from the old bracket with a bit of cutting and folding and then welded it on. Susequently I have for the handbrake cables seem a bit short but if I don't clip it to the normal clip points then it works fine.

the old position

 the new bracket

 the new bracket welded on and painted

Frame CAD assembly

Having all the parts cleaned an painted seemed like a good opportunity to measure them up and model them in CAD. So now all the major parts are drawn and it looks like the motor is only just going to fit, it did come with a back plate to create a ventilation space and also protect the encoder on the back of the motor. However there is definitely no space for that so I've assumed it can't be fitted.

Chassis CAD stp file

This view shows the motor and motor mount sectioned and the motor shaft mount and clutch spline. 

I've bought a taperlock bush and flange plate to lock onto the motor shaft. The taper lock is a 1610 size with a 1 1/8" bore, the plate is a BF16 plate which is 120mm diameter with 6 x 8mm mounting holes at 110mm PCD. 

Instead of buying a whole Smart clutch plate which normally comes as a complete assembly I've found that a Ford fiesta MK1 1.0 clutch plate fits the 19mm 17 spline shaft perfectly, just a few £s from ebay. So the plan is to cut off the clutch friction plate and use the inner plate and probably keep the springs as they will act as a bit of a shock absorber which might be useful. 

Gear selection control

I've had a go at controlling the gear selection motor and it seems to broadly work now. I've done a quick video to explain. 

This is a better video with the voltage now running at 12v, motor takes around 5A on a move and has a bit of a kick to it.

I've had some requests for the Arduino code I used, this was based on some stuff I found on the web, (sorry but i can't remember the source) and my rather limited abilities with Arduino. I then connected this to Makerplot which is a serial port plotter capable of sending and reading some simple commands. It works in a rather odd way as the GUI is a macro you load up, but it's a great program once you're used to it.
So the Arduino code is shown below..
This is a link to the Makerplot software - http://www.makerplot.com/
and the is the macro for the Makerplot as shown on the vid.


This is the photo I found which shows the connection onto the Smart gear selection motor

also a handy schematic of the pins and encoders

----------------------------------- Code to drive motor as shown in the youtube video ------------------
please note, this is note code written spacifically for this project so there is some stuff in here which is not really needed... but it worked for me. You'll probably need to tweak around with the PID settings.


/*
   This program uses an Arduino for a closed-loop control of a DC-motor.
   Motor motion is detected by a quadrature encoder.
   Two inputs named STEP and DIR allow changing the target position.
   Serial port prints current position and target position every second.
   Serial input can be used to feed a new location for the servo (no CR LF).
 
   Pins used:
   Digital inputs 2 & 8 are connected to the two encoder signals (AB).
   Digital input 3 is the STEP input.
   Analog input 0 is the DIR input.
   Digital outputs 5 & 6 control the PWM outputs for the motor (I am using half L298 here).


   Please note PID gains kp, ki, kd need to be tuned to each different setup.
*/
#include <SPI.h>
#include <PID_v1.h>
#define encoder0PinA  2 // PD2;
#define encoder0PinB  8  // PB0;
#define  IS_1  0
#define  IS_2  1
#define  IN_1  3
#define  IN_2  11
#define  INH_1 12
#define  INH_2 13

double kp=300,ki=0,kd=0.5;
double input=80, output=0, setpoint=180;
PID myPID(&input, &output, &setpoint,kp,ki,kd, DIRECT);

volatile long encoder0Pos = 0;
long previousMillis = 0;        // will store last time LED was updated
long target1=0;  // destination location at any moment
int countStep;

//for motor control ramps 1.4
bool newStep = false;
bool oldStep = false;
bool dir = false;


void setup() {
  pinMode(encoder0PinA, INPUT);
  pinMode(encoder0PinB, INPUT);

  pinMode(IN_1,OUTPUT);
  pinMode(IN_2,OUTPUT);
  pinMode(INH_1,OUTPUT);
  pinMode(INH_2,OUTPUT);

  reset_ports();

  digitalWrite(INH_1,1);
  digitalWrite(INH_2,1);

  attachInterrupt(0, doEncoderMotor0, CHANGE);  // encoder pin on interrupt 0 - pin 2
  //attachInterrupt(1, countStep, RISING);  //on pin 3

  Serial.begin (115200);

  //Setup the pid
  myPID.SetMode(AUTOMATIC);
  myPID.SetSampleTime(1);
  myPID.SetOutputLimits(-255,255);
}

void reset_ports()
{
  digitalWrite(INH_1,0);
  digitalWrite(INH_2,0);
}

void loop(){
    input = encoder0Pos;
    setpoint=target1;
    myPID.Compute();
    pwmOut(output);
   // print encoder and target every second throgh the serial port
    if(millis() > previousMillis+200 )  {Serial.print(encoder0Pos); Serial.print(","); Serial.println(target1);     previousMillis=millis(); //}
    // interpret received data as an integer (no CR LR)

   // if(Serial.available()) {
    Serial.print("!O H1Read=");
    Serial.println(encoder0Pos);
    Serial.println("!READ(H1Set)");
    target1=Serial.parseInt();
    }
}

void pwmOut(int out) {
   if(out<0) { analogWrite(IN_1,0); analogWrite(IN_2,abs(out)); }
   else { analogWrite(IN_2,0); analogWrite(IN_1,abs(out)); }
  }


void doEncoderMotor0(){
  if (((PIND&B0000100)>>2) == HIGH) {   // found a low-to-high on channel A; if(digitalRead(encoderPinA)==HIGH){.... read PB0
    if ((PINB&B0000001) == LOW) {  // check channel B to see which way; if(digitalRead(encoderPinB)==LOW){.... read PB0
      encoder0Pos-- ;         // CCW
    }
    else {
      encoder0Pos++ ;         // CW
    }
  }
  else                                        // found a high-to-low on channel A
  {
    if ((PINB&B0000001) == LOW) {   // check channel B to see which way; if(digitalRead(encoderPinB)==LOW){.... read PB0
                                              // encoder is turning
      encoder0Pos++ ;          // CW
    }
    else {
      encoder0Pos-- ;          // CCW
    }
  }
}