Bamboo Racing Car Controllers

2008

Bamboo is one of Thailand's most abundant natural resources. It's actually a fast growing type of grass that is a strong yet flexible, multi-purpose building material which can also be used as a food source. It is also an iconic Asian symbol that has both economic and cultural importance.

A colleague and I in what was then the Computer Information Systems Department (now Information Technology) at Payap University thought it would be fun to take the PVC Racing Car idea to a "tradition meets technology" extreme and so we made some bamboo racing car controllers.

The chassis are modelled after a Formula 1 racing car and wouldn't look out of place on Gilligan's Island. The steering, accelerator, and brake are connected to a computer via a hacked USB joystick and we used them to play EA Sports' F1 Championship Season 2000.

Here's a video of the cars first "test drive" in action. You can read on below for more details on how the controllers were constructed and how they work.

Chassis

We started on a Friday afternoon with some green bamboo poles, pre-cut bamboo slats, and a coil of rope. One group of students worked on the car's chassis while another group hacked the USB joystick that would be used to connect the car's steering and pedals to a computer.

Our original idea was to make something like Fred Flintstone's car but without wheels. However, as the afternoon progressed we only had something that looked like a litter and we were starting to run out of bamboo and rope.

Fortunately, my colleague Dr Ken persevered over the weekend and when I came in to work the following week he had this Formula 1 inspired chassis (see below) to show me. The frame was tied together with rope, the "aerofoils" (or "airfoils") were made from slats which were nailed in place and the seat was two cushions from some old office chairs which were simply propped up inside the frame.

Steering

The steering "wheel" of the bamboo car is actually a T-Piece and in keeping with a real Formula 1 car it is removable to facilitate entry into and exit of the “vehicle”. The shaft of the wheel is inserted into the end of a larger piece of bamboo which acts as the steering column (see the picture below left). A potentiometer with a large volume knob sits on top of the shaft and it turns in response to the turning of the steering wheel shaft. A piece of foam glued around the knob with contact adhesive increases friction and a single bamboo slat secured along the length of the steering column acts as a spring that applies pressure to keep the potentiometer in contact with the steering shaft (below right). The center position of the steering can easily be adjusted by lifting the knob (so it is not in contact with the shaft of the steering wheel) and then centering both the knob and the wheel.

Here is a list of the parts we used to wire up the car and connect it to the computer:

• Analog USB joystick
• 9-pin D-sub miniature male & female connectors + 1 x backshell
• 10K ohm potentiometer with matching large plastic volume knob
• SPDT (single pole, dual throw) switch
• 2 x long arm microswitches
• 7m (approx) of two-strand hook-up wire

With the help of some students we hacked the USB joystick and mounted the female 9-pin D-sub connector underneath the body of the joystick. On the back of the joystick near the USB cable entry/exit point we also cut a small hole and mounted the single pole double throw (SPDT) switch.

We cut the circuit trace from the X-axis of the left analog thumbstick and used a small length of hook-up wire to connect the trace on the thumbstick side of the cut to one side of the SPDT switch. We wired the other side of the cut trace to the center pin of the switch (the common contact) and the other side of the switch to pin 3 on the D-sub connector. Provided this modification is done carefully you can then switch the X-axis of the left thumbstick to choose between the internal potentiometer in the joystick (allowing normal use of the joystick) or you can choose pin 3 on the D-sub connector which is wired to the center wiper of the 10K potentiometer used to steer the bamboo car (the other two pins of the potentiometer are wired to the Vcc and ground connections respectively). The pin-out for the D-sub connector is shown below with pins chosen to keep compatability with the Multiplayer Guitar Hero controllers:

DSUB	Pin	USB Joystick	Bamboo Car
	1	Vcc	Vcc
	2	-	-
	3	Analog 1 X-axis	Steering
	4	-	-
	5	Ground	Ground
	6	Button 5	Accelerate
	7	Button 7	Brake
	8	-	-
	9	-	-

Accelerator and Brake Pedals

The accelerator and brake "pedals" were made by glueing two bamboo slats together which were then cut into two 40cm (approx. 16") lengths. We drilled a hole in each pedal about 7-8cm (approx. 3") from the top and then used some bolts and washers to hinge the pedals on the sides of the chassis (see the picture below left).

Two slats were nailed between the sides of the chassis to use as mounting points for the two long arm microswitches as well as acting as a back-stop for the pedals when they are at rest. The microswitches were carefully nailed in place and rubber bands were used to provide resistance for the driver to push against (see the center picture below). We wired the pedal switches to work in the same way as a light inside a refrigerator or the brake lights found in many passenger cars. With no pressure applied to a pedal the rubber bands hold the top against the switch which is in the open or “off” position. When the pedal is depressed the switch is released and it turns on (see the picture below right). The switches are connected to two of the modified USB joystick's buttons via pins 6 & 7 on the D-sub connector and these two joystick buttons then simply need to be mapped to control acceleration and braking within the computer game. The other connection on each switch is wired to Vcc (which is the common connection no most USB joysticks).

Unlike the smooth analog steering mechanism, the pedals only provide pure digital “on” and “off” functionality. Despite this, many people who have driven the bamboo car have reported experiencing a compelling “illusion” where the felt that depressing the pedal further made the in-game car accelerate more quickly.

Racing

One of our more artistic students painted the two bamboo cars for us which were dubbed "01" and "10". We added a small plank to each of the cars about half-way along the length of the chassis so that we could mount an LCD monitor for the drivers and then it was time to race! We used the cars at Payap University's International Day where drivers raced in a 4-player networked game of F1 Championship Season 2000 alongside two PVC racing cars.

In the first picture below it looks like we might be testing the aerodynamics of the cars but they are actually en-route to the Agape Home for babies with HIV/AIDS. We took the cars, a group of students, and some of my other projects to the orphanage so the kids could play some games. In the picture below on the right you can see that we accidentally left the steering wheels on campus so we had to improvise with some PVC pipe. One of the boys is driving, the little guy peeking around from behind the monitor is wearing the headphones, and the girl is operating the pedals because the drivers legs couldn't reach! The kids had a great time and provided they could be involved somehow they were happy.

Other Projects

You may also be interested in reading about my PVC Racing Car Controllers or some of my other projects: