Pinewood Freak

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Sometimes, weight goes in front

December 20th, 2005 · 3 Comments

Most pinewood tracks are shaped something like this:

\
 \
  \
   \_____________

But every once in a while you’ll see a track shaped like this:

___
   \
    \
     \
      \_____________

The first track has a starting gate where every car starts out pointing down a hill. The second track has a flat starting gate. All the cars start out sitting mostly flat and then head down the hill.

Usually you get better speed by putting your weight in the back because you get more potential energy from having the weight starting higher above the ground. With a flat starting gate, you can put the weight in the back, middle or front — you don’t get any more potential energy. Since the car is flat, no part of it is any higher above the ground than any other part of it.

So does it matter at all where your weight is at on a flat-gated track? Yes it does.

Your car will start off with the front heading down the slope, then the middle ends up on the slope, and finally the back makes it onto the slope. If you put the weight in front of the car, the potential energy of your car will start getting converted to kinetic energy as soon as the front of the car makes it onto the slope. If your weight is on the back of the car, then you have to wait for the back of the car to get on the slope before the weight starts helping out.

On this type of track, put your weight to the front and your call will pull get a little head start on the others. How far up front? About an inch to an inch and a half behind the front axle is good. Read about rear-weighted cars for an explanation of the science involved and why you don’t want your weight too close to either end of the car.

Comments

3 comments so far ↓

  • Bill Klingler // Feb 14, 2012 at 9:06 am

    If the start is flat why would the cars start rolling in the 1st place? The rear weighted car would still be faster. A Lot Faster. The track can’t be as pictured with that drastic angle so it must be very different so the bottom of the cars wouldn’t hit the track. The front weighted car would lose all the advantages of the “Front End Extension” effect and higher velocity when the Center of Mass of each car reached the Horizontal run. There is such a drastic difference in distance between these two cars at the finish that the front weighted car would have no chance. Anytime a front weighted car wins a race it is because of something other than weight placement. It is impossible for a front weighted car to beat a rear weighted car between 2 perfect cars. The Cycloid of Constant time is involved even on this track. I think this would come into play even on the area you call the “Flat Area” because that area can’t be Flat. That means the rear weighted car is going to have an advantage on this section also because gravity will be helping the rear weighted car longer than the front weighted car. It doesn’t matter who starts down the hill first unless you end the race at the bottom of the hill and you are not doing that.

  • Bill Klingler // Feb 14, 2012 at 7:09 pm

    A bit more of my opinion.
    Let’s say you put the COG 1 1/2″ behind the front axle slot as you suggest and you put the rear COG 1 1/2″ in front of the rear axle slot. You now have only 1 3/8″ between the two COG’s. The two COG’s
    will go over the top hill nearly the same time since the cars started out with their front ends even. They will both race down the incline plane, assuming it’s an incline plane and not a circular arc, but when the COG’s reach the bottom curve the rear weighted car will pick up a tremendous advantage consisting of the “Front End Extension” effect and the higher velocity. If the track is a Circular Arc, the rear weighted car will pick up an even greater
    advantage. I don’t see how a front weighted car would have a chance.

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