Different kind of PWD question

[Scoutfish]

When we do check in for PWD, we of course use a scale, but we also have two boxes .

 

WE use the boxes to check for width and length and bottom clearance.

Used to be that we'd close the lid too to make sure the cars were not too tall, but that was due to a previous timing gate that really did have a limited height to it.

 

Pretty much now, you can have a car that is about 5 inches tall...not that you'd want to - that is....but you could.

 

Now, the rules we follow ( based on district rules are as such:

 

1) Car must not be over 5 ounces

2) Car cannot be over 2 3/4 maw width overall.

3) Must be at least 1 3/4 between wheels in width

4) Axle grooves must be same distance as what they came from box - if you move one, you must move the other the same distance in relationship to each otrher.

5) Car cannot be over 7 inches long

6) Only graphite lube on car

8) Tires can be de burred, but must stay flat and same width as originaly packaged

9) All parts must be offical BSA parts

 

But I've been thinking about the length of the cr having to be 7 inches max.

 

Why? I mean, I don't care that it's 7 inches max, and I do not have a problem with it....just wondering why?

 

I mean, if all cars start equally at the front edge by using a pin starting gate, then the front edge of all cars crossing the finish line will still be reflected by how fast the car ran, and not that it was longer.

Based on all cars starting equally in the front, the only thing you have done is added more length to the back of the car.

 

From a logistics point of view, the longer a car is - and assuming you maintain axle distance - the more unstable it will be and the ability to track straight diminishes.

 

Again, I have no issue with a car haviong a max lentgh of 7 inches...just wondering why.

[rjscout]

With a longer car, you could move the center of mass further back, increasing the time that the potential energy can work on the speed of the car while rolling down the incline.

 

[Eagledad]

Rjscout is correct.

 

How is a car lengthened from the original block of wood?

 

Barry

[Basementdweller]

This is a really simple problem...

 

So you cut a thin wedge which leaves you a lot of extra wood.....Glue it the top and extend it.....

 

or

 

I would take a aluminum strap and then put some tungsten cylinders on the end.......

 

I would worry about getting the Center of Gravity too far back and not being able to keep the car on the track.

 

 

This only works on a track that has a flat run out before the finish line if it is a perfect 30 degrees from start thru the finish line it would not make any difference.

 

 

There is lots of ways to extend the car chassis......

[Scoutfish]

Okay, that makes sense.

 

Barry,

You can add wood to the front or rear just as easy as you add it to the sides or top: glue, nail, screw, etc...

 

My son's last car was a 72 Mustang fastback. We added wood to the sides ( to the max width of 2 3/4 ) and cut out fender wells for the wheels. The body was cut as close tio scale replica as possible including length, then bumpers were added back to the front since they were easier for my son to make as seperate pieces than carving from original block.

 

But some scout's designs have tail pipes, hooks ( was a tow truck..I think) boat with bow mast or whatever it is called Bulldozer with front blade...

[Eagledad]

OK, thanks guys.

 

Barry

[JoeBob]

Take your basic car and add two soda straws to the front, making the overall length 12 inches. Tape the fronts of the straws together so that they engage the starting pin. and you've given yourself five inches up the track, which translates into more potential energy (gravity) in the drop until the track flattens out. All else being equal that car will be moving faster at the bottom of the hill.

 

If your track has enough room behind the starting pins to accoomadate five more inches, if the straws don't bottom out (rub against the track) in the curve where the drop translates to the flat track, and the straws are dark enough to trigger the finish line sensor; you'll win.

[JoeBob]

Take your basic car and add two soda straws to the front, making the overall length 12 inches. Tape the fronts of the straws together so that they engage the starting pin. and you've given yourself five inches up the track, which translates into more potential energy (gravity) in the drop until the track flattens out. All else being equal that car will be moving faster at the bottom of the hill.

 

If your track has enough room behind the starting pins to accoomadate five more inches, if the straws don't bottom out (rub against the track) in the curve where the drop translates to the flat track, and the straws are dark enough to trigger the finish line sensor; you'll win.

[SSScout]

Winningest adult unlimited car:

 

Take standard PWD block, cut diagonal from front bottom edge to top rear edge, making a wedge. Round front corners, sand smooth all around.

Install suitably polished axles and cleaned up "detailed" wheels, graphite/moly disulphided as allowed.

Find a BIG bolt, about 3 or 4 oz. all by itself, and glue it far back on the top rear of the wedge, balanced such that the front wheels barely touch the track surface. Adjust bolt size to weight specs. For appearance sake, one can drill a hole in the rear of the wedge to accomodate the bolt.

Watch it roll.....