Tuesday, January 20, 2015

Science Olympiad Wheeled Vehicle Advice

In that I have some experience with mousetrap powered cars, a student has asked me for some advice on a similar event in the Science Olympiad competition known as “Wheeled Vehicle”. The model car can be built like a mousetrap powered car but must be powered by a “non-metallic, elastic material (rubber bands, fishing poles bungee cords). I consulted with Al Balmer aka Doc Fizzix and he gave me some advice and sent a rubber band powered car kit that his company sells. Competition requires that a kit cannot be used but as with the mousetrap cars, I learned so much from first building a kit. The kit car also has the adjustable braking that is needed for the competition. 

Long Run of the Day 

Before actually building the kit I was giving the student some advice based on what I knew from trying to get maximum distance from a mousetrap powered car. The challenge for Wheeled Vehicle appears to be more to get the car to move as quickly as possible through a certain distance and then stop accurately on a spot. The car must move very accurately in a straight line also.

Stretching to First Hook Gave Short Runs

With the Doc Fizzix kit car I spent some time running it across the smooth floor in a local mall yesterday and measuring the distance. I had brought some Tan Super Sport rubber strip 3/16” width to try as a replacement for the #64 rubber band included. For rubber model airplane use the Tan Super Sport would be superior but in my trials it didn’t seem to work as well. That could have been because the actual loop of rubber and the length of string were not correct.

Trying Different Loops Sizes with Tan Supper Sport Rubber

For the first runs I only stretched the rubber band to the first hook position, the runs were less than 20 feet. When I stretched the rubber band to the second hook then the distance really increased. On the last run the car went 61 feet which is over 18 meters. For the competition the course is never longer than 12 meters so distance shouldn’t be a problem, more emphasis will have to be placed on speed and accuracy.

Really Stretching Out the Rubber Band

For the competition some type of lever release is needed so that the eraser end of a pencil can start the car and a pole in the front of the car is needed for the laser siting that is used in competition. Some type of adjustable steering might be nice although my kit car appeared to travel very straight without adjustment.

61 Feet Longest Run

1/21/2015 Update

Adjustable Steering Mod

2-18-2015 Update

Lever in Locked Position
Lever in Locked Position

Added a lever device that locks into a wheel on the axle that has a notch in it. The white plastic rigid tubing twists in the holes in the balsa supports, the lever was glued on top of the plastic.

Additional Resources


Video of Long Mall Run


  1. Mr.Scienceguy, how do you put the strings that are attached to the brakes on and what are they attached to. Could you show more pictures or make a video about the process of putting the steering on and the process of attaching the pins and the string together. Do you have any idea how to start the vehicle with the back of a pencil.

    1. That last picture is confusing, there are no strings attached to the brakes. I was thinking of having the wingnut that moves across the threads to stop the car pull a string to pull the steering one way, that didn't work. I would think if you just adjusted the steering with a slight turn it could go around the obstacle.

    2. As far as starting with a pencil, one way is to have a lever that goes into a circle around the rear shaft with a notch in it. There was a Youtube video showing that. It looks really busy for me the next few days but I will try to do something next week.

    3. Is it possible for you to do something before the February 20

  2. I already finished building the vehicle with the adjustable steering. My problem is that the vehicle moves for a while then one wheel would get stuck on the side of the car and the car would stop. When you push the wheel of the side, it would move again before getting stuck again. Could you please help me with this problem.

    1. On my mousetrap car I used short lengths of straw as a spacer between the wheel and the side of the car. On the car in the picture there are two faucet washers over the axle for spacing and a metal washer next to the car. Without seeing your car it is hard to tell what is binding but something must be.

  3. I added a picture of a release lever I quickly made tonight. Built a balsa circle with hole in it, split it in half and glued around axle. There is a notch in the circle that a lever fits in until you push down and then it release the axle.