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Do raised front ends (cheater bars) work?

February 27th, 2012 · 10 Comments

Will adding a raised front end to your car help it get a head start?

3387137478_cde7a8c4d0.pngOne of the pieces of misguided advice I often see is to install a raised front end (often called a “cheater bar”) in the car. The theory behind the cheater bar is that when the gate drops, the top moves before the bottom, so if your car has a high front, it’s able to start moving before the other cars do.

It won’t help on any track that uses a spring-loaded starting gate.

While a raised front might be of some minimal benefit on a manually-operated gate that’s released slowly enough, on any gate that drops quickly, the entire gate will be clear the car before it is able to overcome inertia and start rolling. You might get a paper’s thickness of a head start, but not enough to make any real difference at the finish line.

Photo from Flickr user corben23

Comments

10 comments so far ↓

  • Mike // Feb 27, 2012 at 12:37 pm

    This is pretty funny to read. Most of the timers on the tracks read out x.xx, cars are weighed to the .1 of an oz. Axles are polished with 3000 grit sand paper and wheels are meticulously shaped. But here you are saying that a car having a .004-.008 inch advantages is pointless. It is not one thing that makes a winning car it a whole bunch of little things that add up together to make a winning car. That .004 head start could be the difference between winning and losing a race. But neither really matters all that matters is the look in my 7yr old sons face when he understood the physics behind why we were using the raised nose. So I can honestly say we have already won the race.

  • Adam Kalsey // Feb 27, 2012 at 5:25 pm

    Unless you’re on track in which starting gates and finish line timers are precision-machined and laser-aligned, chances are that the cars on the track already have total race distances that vary much more than the narrow tolerances you’re talking about.

    Subtracting a thousandth of an inch off your run time doesn’t matter if your track is banged around, stored poorly, and assembled in a hurry using hand tools. Like most tracks.

    With a spring-loaded gate, the gate almost vanishes like magic. The length of time between when the top of the gate moves and the bottom of the gate moves is miniscule.

    Unless you have something sticky on the nose to cause the falling gate to propel the car forward (which is of course illegal), you’re gaining no race advantage from that raised nose on a track with a spring loaded gate. In fact, Maximum Velocity did extensive testing and found that the cheater bar car was no faster than the exact same car without the bar.

    I’d encourage you to take the testing a step further with your son. Use this to teach the scientific method. You have a hypothesis: that a raised nose car is faster. Create a test car with a variable-height nose and a test track that can be started with a manual or a spring gate. Find out if your theory is right, and under which conditions the car is faster.

    Teach your son the value of verifying your ideas instead of just believing what you read on the internet. That will be of more value than the physics lesson.

  • Bill Klingler // Mar 1, 2012 at 2:51 am

    The car pictured was built using the wrong end for the front. Between two “Perfect” cars, the car pictured would lose every race. The 2 cars would look exactly the same but the CG on the car he was racing would be higher up the arc. This would give the advantage of higher velocity and more on the “Front End Extension” effect when the car goes through the curve. That is why we cut off 5/16″ from the back and move it to the front. It is also another reason we use Tungsten so we can position our CG where we want it. Don’t use the picture of the car on the BSA box as an example. It is wrong.

  • Bill Klingler // Mar 1, 2012 at 3:06 am

    Mr. Adam Kalsey, you are a very kind man. I know this to be true by the way you answered this gentleman. Thank you.

  • Mike // Mar 1, 2012 at 8:42 am

    Having just read the maximum velocity article it still does not prove that the raised front end does aid in getting a head start. The test they did was not done scientifically; it had too many variables, mainly 32 feet of track. In order to do a controlled test of the starting advantage you only need to a few millimeters of track. The extra 32 feet have too many variables that will influence the car, remember this method is only to get you a head start. It is just a small piece of the pie.
    Drawing a free body diagram for a spring loaded pin start it is easy to see the starting advantage. The advantage will be the difference in heights between your car and a lower car divided by the speed at which the pin drops. So let’s say the pins speed is 60 in/sec (I am just guessing here) and the height difference is 1 inch so in this example the advantage would be 1/60 seconds or .0166 seconds. I will agree that it is not much and there are more things to spend our time on for a faster car, but it is an advantage.
    I do agree with you, never read something on the internet and take it for fact, to include your website. (PS I did not learn about the raised front end on the internet) Publish an article in a scientific journal on the science of the pinewood derby and then I might not second guess you .
    I think it is honorable of you to share your knowledge of the pinewood derby.

  • Dave // Jan 5, 2013 at 9:05 am

    raising the front end, I do not understand. But for a track with cylindrical pins to hold the cars at the gate, a nose-notch will essentially put your car ahead of the other cars from the get-go. So if it is legal, I always do this.

  • Bill Klingler // Jan 12, 2013 at 5:35 pm

    Dave, It’s not legal. No part of the car may extend past the starting pin. The car shown has a wing up front that will keep the car behind the start pin. . If a “cheater bar” was any value all the Pros would use it. As far as I know, none of them do.

  • Adam Kalsey // Jan 24, 2013 at 8:45 pm

    Also, if your finish line is the type with an overhead electric eye and the eye is centered on the track then it’s likely you’re not getting any benefit from the notched nose.

    Assuming the electric eye is reasonably aligned right to left with the starting pin, the winning car is the one that travels the distance between the back of the starting pin to the front of the electric eye in the least time.

    In other words, if your front end wraps around the starting pin, it probably wraps around the finish trigger, too. You won’t trigger the finish line until that notch crosses the finish.

    That’s why the car pictured above has a tape flag wrapped around the bar - to give it enough of a surface to trigger the eye.

    And if your local race includes additional races that might run on different tracks later on, you might even be hurting yourself. I once saw a track that had a starting pin as wide as the center guide rail, but used an overhead laser finish that watched the center of the track. If you had a once-inch notch, you might as well have been starting your car 1 inch further back than the rest of the cars.

  • Bill Klingler // Dec 20, 2013 at 3:26 am

    Just for fun, let’s take the pictured car and build it a different way. We will have to do away with the notch.
    1. Cut the shape to 1/4″ thick.
    2. Cut 5/16″ off back (short end) and move it to the Front
    3. Epoxy 2 rows of 6, 1/4″ tungsten cubes behind rear axle slot.
    4. Epoxy 2 rows of 6, 1/4″ tungsten cubes in front of rear axle slot to achieve a 3/4″ COM (Center of Mass-point where car will balance)
    5. Raise left front wheel off ground
    6. Set rear wheels with 2 1/2 degrees of NEGATIVE camber
    7. Set right front wheel with 1 1/2 degrees POSITIVE camber and adjust toe-in so car will drift to left, 2″ in 4′.
    8. Paint and decorate the car so it looks like the car pictured.
    That’s the way I would build this car. Wheel and axle prep, checking rear wheel alignment without front wheels on car, final tuning, are all separate subjects.
    If speed is your goal, would anyone build the car differently?

  • Bill Klingler // Dec 20, 2013 at 3:44 am

    Sorry, I forgot something.
    The body of the car should be narrowed 1/16″ at the right front wheel.

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