The first design that I used for steering the modified PowerWheels car worked pretty well.  It had one reliable issue that we fixed, but before I could test it completely I was shown a possible idea with an electric car track for the driver’s seat.  What was depressing was trying to find any details of how to work with the idea that I will show here.  I searched many sites and they talked about some ideas, but then I could not find any details, so I hope to show you what I made; I am not an engineer, not a fabricator, but I have been around computers for a while so  there might be a better way to have done something that you see.  If you do see a way to improve an idea, add a comment and share with all.

This video show me driving the car with the steering that I will be describing.

What i did was use was an old cordless drill, and created a worm gear and attached it to the steering linkage that already was part of the steering assembly for the car.  I saw and read a few posts on Modified PowerWheels forums where a few people had tried servos; and there were many different configurations, but I could not see them as a real solution because it seemed like it did not take much to stall them or break them.  I did try using some strong servos based on some of their ideas, but again I could not get the wheels to move on a constant basis, and it was expensive route. 

See here for a bigger picture pic1 pic2

In addition to the photos I tried the heavier servo and chain connected directly to the linkage on the wheels that also did not work.  So after much trial and error I gave up on servos, and started to experiment.  What I found that really worked was using a cordless drill.  I had a 7.2 volt drill that the batteries were dead.  When I connected it to the 12volt battery it just ran a little faster than normal.  I know it will burn up the gears faster, but it did work.  Why the drill, it offered many advantages.  It had a motor, it had gears and the chuck offered an easy way to connect a shaft to the motor and an easy way to quickly disconnect the shaft.

These are a few pictures of the drill and the worm gear completed.

Larger versions of the pictures. pic1 pic2

What you are seeing in picture1 is a 5/16 threaded rod that I bought from Home Depot.  I also bought the matching nut,4 other little nuts and bolts holding the two pieces of plastic and the aluminum strip that you see from there also.  I used the 5/16 rod as it seemed to give the proper gear ratio and speed of moving the wheels from left to right.  The interesting thing was I only needed to move the strip of aluminum about 2 or so inches to go from one extreme side to the other.  As you can see I sandwich the large nut between the two pieces of plastic  and it is held tight and kept from moving by the 4 other nuts and bolts.  Of course I had to drill a hole large enough that the 5/16 threaded rod could fit through the two pieces of plastic.  From here I fixed the plastic to another piece of aluminum that was shaped in a “U”.  This was in turn attached to the flat aluminum strip.  The aluminum strip if you are wondering replaces the flat strip of steel that is attached to both wheels and also has the steering wheel column attached to it.  The a 5/16 rod will not fit in a 3/8 drill so as you can see I needed to grind down the rod until it would fit in the drill.  This is also where I ran into an issue.  When I ground the rod down I was not getting it perfectly round and the vibrations that happened during operating kept slowly allowing the rod to slip out of the chuck after driving for about 15 minutes. 

To fix this I went to the sears hardware store and bought some gas line hose, you can also find it at some auto parts stores.  I also bought a couple of little clamps that fit the hose.  I worked the rod on one end and put the other end over a bolt that fit in the hose.  I then cut the head off the bolt, so that it fit in the drill chuck.  Now the drill was able to tighten down properly on the bolt.  I did have to make sure the hose was not too long or it would twist; shorter is better.  The hose absorbed the vibration and this seemed to solve the problem.

Then next question someone would have is how did you control the wheels and prevent them from going to far left or right.  A servo has an encoder in it that allows you to tell the servo where to move too.  The drill solution does not.  The way I controlled everything was with limiting switches.  Basically  the electricity flows through the switches and when the worm gear part  moves and touches the switch it kills the power to the motor, stopping it.  The other switch is still active so it can move the wheels the other way.  As soon as it moves away from the switch it is touching that switch now becomes active.  The switches were mounted on the board and their levers would hit some long dry wall screws that I put in to the cars at the points where I wanted the wheels stop going any farther.

The below wiring diagram I created for the article on WiFi Warthog that I did for Coding4Fun, there I used the same wiring schema, but use the electric seat tracks from a car.

Full size picture here.

In the diagram above I am controlling the motor with a Phidgets 004 interface board.  It in turn energizes some automotive relays which act as a Double Pull Double Throw (DPDT) switch.  The Phidgets device can be controlled by many different  programming languages.  I use C# and have this being controlled by a Xbox 360 controller.  The code for the most part was the simple part.  Basically on the Phidgets device there are 4 low amp relays.  two will control the steering for left direction and right.  The other two I used to control the forward and reverse of the PowerWheel car.  The program simply energizes the Phidgets relay which energizes the  automotive higher amp relays.  In my case this is all controlled sub-second and works great. 

To see the code I used and a write up on the whole car that was used at  the PDC, it will be published on the Coding4Fun site in the next few weeks.  I will post a link to it once it is in place.  If you just can not wait, you can ask questions in the comments.

Well the water gun idea worked great for the most part, but now them rabbits are coming down the other side of the house and by passing the gun.  So I had a thought; what about going mobile.  But for this idea we were going to need a great deal more thought.  Well the idea got started and like most ideas it morphed into something that sounded like way to much fun not to build.  So I made the car, and mounted a water gun on it, and even shot water out of it, but in the end it never made it to the battle field.  Instead it was turned into WiFi Warthogs,  a Laser Tag game.  It can be played by a minimum of 2 players (one for each car), but can go to any number of players real quick, it all depends on the number of cars you wish to use.  Here is a video of it in play.

In this video you see two cars and there were only two players.  The players are using XBox 360 controllers to control the cars.  A player can be either the driver or the gunner if there is only one player per car.  If there are two players per car then one is the driver one is the gunner.  When you see the cars stopped, it is because the driver has switched to gunner mode and is in the process of shooting.  Yes if your car gets hit you will get feedback in the form of the controller shaking and lights on the gun.

The cars will be out at the PDC this year if you are going, stop by and try them out…  I will be breaking them down on exactly how I built them on the Coding4Fun site, the site can be found here.   It should appear there some time in December 09. 

To give you some ideas of what will be covered, first think about the big picture.  These are PowerWheels Barbie Jeeps that for the most part are still in their original format.  The steering and transmission robotics were controlled by Phidget’s devices.  I used Windows 7 on an Eee Pc to control everything and of course for the LaserTag game itself I used a standard LaserTag set of guns.  

In the article that will soon appear on Coding4Fun, I will break down the mechanical make up in detail as well as how the different software engines were created.  In addition I will leave you with some food for thought on how you can expand or make some of you own changes.

On this site I will go into some detail on some of the prototyping that was used prior to the finish product, as it has a great deal of merit and would have been used had we not found some some easier ways to do parts.  And of course I will go into the way to make the water gun work…

So stay tuned there will be more to come.