Offroad Bumper: Mulligan

        I've decided to restart the bumper I'm building for my truck. The main reason for this is that I've found a much better design online, which looks much better:

        

        I can build this new bumper with metal twice as thin, but It will be even stronger, as the metal has a much stronger structure. I didn't really have a clear idea of what I was doing when I was building my first bumper attempt, and the fact that I had to build it at school meant that I didn't have a way of checking if the pieces I made fit properly.

        The bumper will fit onto my truck by simply sliding onto the frame ends, and bolting in.

        I'll be able to start building version 2 of my bumper once I get a working arc welder, and build a welding table. I've also made a 3d rendering of what my overall plans are for the truck.

Physics Projectile Motion Video

        For a recent physics assignment about projectile motion, we were given 2 choices: we could build some kind of projectile launcher, or we could film an example of projectile motion, such as a soccer ball being kicked. In either case, we had to do a report. Originally, I felt like building something, but then I got the idea of filming a snowmobile jump. Not only was it fun for me to do, but it also gave me the chance to play around with movie editing, which I thoroughly enjoyed.

Here's the product of my work:
(You may want to skip the calculations, that part is somewhat dreary) 

ODSS Electric Car Build Part 1

         For the next couple of months, I will be documenting the progress of the ODSS electric car team as we build a new car. Our goal is to go from the simple frame that we have now, to a fully built car by the May 24 weekend, the date of the competition. 

          So far, we took an old aluminum frame that we had from a previous car, and trimmed off several pieces of it to give us a nice simple chassis to build off of. The plan for this car is to have a simple set-up, but with as little wasted space as possible. This was one of the main drawbacks of our previous cars.

        After the chassis was modified, we cut out a panel of sheet metal for the floor. We haven't used sheet metal as a floor before, but this time we're trying it instead of plywood to help conserve weight. This will also help if we drive in wet conditions, as plywood would act like a sponge, soaking up water and adding massive weight to the car. 

Coilguns 101

        Over the past few months, I've been doing quite a bit of research into coilguns and how the work, so I thought I'd do a write-up on them.

      When a conductive wire, such as copper wire, is rolled up into a coil, and an electric charge is applied to it, it creates an electromagnetic field. The higher voltage applied to it, the larger the field. This means that a metal object will be pulled towards the coil with more force if more voltage is put through the coil.

       

        A coilgun operates with this basic principle. The copper coil is wrapped around a plastic barrel(it doesn't have to be plastic, just a material that doesn't conduct electricity). Then, a very large charge is released into the barrel over a very short period of time, creating a quick but extremely powerful magnetic field. When a bullet is placed in the barrel, a short length behind the coil, the magnetic field pulls it towards the coil with great force, causing the bullet to fly down the barrel with great speed. 

        The large burst of energy required for the coil is generated with the use of a capacitor. a capacitor is much like a battery, in that it stores energy. However, a capacitor can release it's energy much faster than a battery. So if a high voltage capacitor fully charged, then connected to a coil, it will release all the energy into the coil very quickly. 

        When talking about coilguns, you may hear the term 3 stage, or sometimes 3 phase. This simply means that multiple coils are used to keep the bullet at constant acceleration down the barrel.       

Testing the Analog Inputs

        The 4 inputs on the SSC-32 card can be used in 2 different ways: Digital and Analog. We have already used the first in the last post and now we will try using them in Analog mode.

       To do this, we need a Potentiometer (or “Pot”) as shown in the diagram from the SSC-32 manual.

        A potentiometer is basically an adjustable resistor, so the as you turn the dial on it, the resistance acting on the electricity moving through it increases or decreases.

        We used the ohmeter to check the resistance of the pot by measuring across the two outside connectors. The meter showed that this was a 25K ohm pot and when we adjusted it, the reading didn't change, confirming we had the correct leads.

        We then tried reading the resistance across the center and outside leads and found it varied as we turned the handle.

        We then connected up the three leads of the pot to the “+” (5 volts), “-” (ground) and “A” (the first analog input) pins of the SSC-32 card using the breadboard. We also connected leads to the “A” and “-” pins so that we could monitor the voltage being given to the “A” input as we adjusted the potentiometer. The connections are shown below:

        With the pot adjusted to 5 Volts we used the terminal program to send a “VA” command to check the value of the “A” input which came back with “FF” or 255 in decimal. Note that the first 3 bytes (56 41 0D) are the “V”, “A” and carriage return we typed in.

        Note that the initial “VA” command did not give the correct value because one dummy command at the beginning is required to change the input from digital to analog mode. We then adjusted the pot to 0 Volts and tried the command again:

        This time the response was “00” or 0 decimal.

        We then calculated what the response should be if the voltage was set to 3 volts:

        If measuring the value correctly, the response to the “VA” command should be 3 volt/ 5 volt * 255 or 153 decimal which is “99” in hex. When we tried it we got the correct result!

        We also tested the other 4 inputs pins by tying them to either Ground or 5V. They can all be queried at the same time using the “VA VB VC VD” command which returns 4 bytes instead of 1.

                   Now that we know they work, we can connect the compound eye to these inputs. The eye is actually connects to 4 input pins, one for each direction around it(up, down, left, right). It also has two other pins, one to power the receivers, and one to power the emitters. 

New Parts

        After a bit of a delay, the parts we ordered from Robot Shop have finally arrived! We received a new servo motor for the grabber on the arm to replace the old one that is not working correctly (the internal gears are worn and it has a greatly reduced range of movement), a collection of wires to connect the SSC-32 inputs and the Raspberry Pi to the breadboard, and two circuit boards so we can connect them together and to the sensors.

        The circuit on the left is a Logic Level converter. The main purpose of it is to take signals from one voltage, and convert them to another. This is vital, as the infra-red sensor operates at a different voltage than the SSC-32 and Raspberry Pi.

        The board on the right is Dagu Compound Infrared Sensor. The bulbs in the middle emit rays of infra-red light, and the black sensors measure the response time.  If something is in front of the sensor, the rays will reflect off of it, and the response time will be quicker. This allows the sensor to detect objects up to 20cm away. We can use this on our robot to follow a person, detect obstacles, or help to position the arm when picking up an object.

Lift kits 101

      Currently, I've been doing some research into buying a lift kit for my truck, and I've noticed a lot of confusion among people in the same situation. I'd thought I'd help by writing down everything I've learned so far.

      First and foremost, there are two basic types of mainstream lift kits:

Body Lifts

      Body lifts lift up a vehicle by simply using blocks to lift the body of the vehicle off the frame. This makes body lifts incredibly cheap, simple, and easy to install. However, they offer almost no performance improvements.

This means that body lifts are really designed for people looking to get a slightly lifted look, or to make room for bigger tires, without spending lots of money. It would be extremely uncommon to find a body lift kit bigger than 3 or 4 inches.

An example of a body lift kit.

Suspension lifts

      Suspension lifts are the real deal. Anyone serious about off road performance should get a suspension lift. They lift a vehicle by replacing and adding key parts of a vehicles factory suspension system. These new parts lower down the wheels from the frame, and allow bigger shocks. This allows the addition of bigger tires, and more wheel travel, which is how much the wheel can move up and down.

An example of a suspension lift kit. Note the bigger shocks.

       The suspension lift kit that I am planning to buy is produced by a company called Race Car Dynamics, and offers 5" of lift. The main reason I'm interested in it is that it has received extremely positive reviews from many people, and it adds additional equipment that other kits don't, such as traction bars, which act as a brace between the rear axle and the frame, and high quality Bilstein shocks. 

What the RCD 5" Lift looks like installed.