Date.prototype.getWeek = function() { var onejan = new Date(this.getFullYear(),0,1); return Math.ceil((((this - onejan) / 86400000) + onejan.getDay()+1)/7); } var today = new Date(); var weekno = today.getWeek() % 26; var tips=new Array(); tips[0]='After experimenting with several types of graphite I recommend Max-V-Lube. This graphite lubricant has a very high carbon content and high \ purity, necessary ingredients for top performance.

Avoid coarse ground graphite, synthetic graphite, or liquid graphite products. While these \ products make work well in some applications, pinewood derby racing is not one of them. Above all, do not use \"Dry White\" or similar teflon-based \ powders. These lubes do not work well for pinewood derby cars.'; tips[1]='After the final lube with graphite it is important to run the car on a test track about five to six times (or spin the wheels many times). There \ is a graphite wear-in pattern, as a speed of the car will improve for up to five or six heats, after which the speed stabilizes. After 15 heats (or so) \ the lube will begin to wear off.'; tips[2]='Lifting one front wheel off of the track will provide a speed advantage. Why? A reasonable guess is that raising a wheel reduces friction. \ But actually, the amount of track to wheel friction and axle to hub friction is not reduced by lifting a wheel (rolling friction is based on mass and \ the coefficient of friction, not on the amount of surface area contact). Instead, the friction on the other three wheels increases, compensating for the \ lifted wheel.

The advantage of a lifted wheel is as follows:\

  1. Less energy required to start the car rolling - A small amount of energy is required to start a wheel rolling (wheel inertia). With only \ three wheels on the ground, the wheel inertia is reduced by 1/4.

  2. A bad wheel can be lifted - Test spin all of the wheels to find the poorest \ performing wheel. Then use that wheel as the lifted wheel.

  3. Simplified wheel alignment - Only one front wheel must be aligned.

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  4. Increased stability - This may be the biggest factor. It only takes three points for an object to rest on a flat surface, and it is actually somewhat \ difficult to get all four wheels to evenly touch the ground. Usually the car ends up mostly resting on three wheels, with the fourth wheel barely touching. \ But when in motion, the car will rock back and forth and thus waste energy. By lifting one wheel, the car will be more stable.
'; tips[3]='What is the key speed factor? Well, all the factors interplay, but assuming that all of the areas are reasonably well done, and assuming \ the track has a sloped portion followed by a flat portion, an important factor is the location of the center of gravity. A small movement of the \ center of gravity can have a relatively larger effect on the car.

Why is this? Because the location of the center of gravity directly \ relates to the speed of the car on the flat part of the track. With the center of gravity towards the back of the car, the car will accelerate for a \ longer period of time, resulting in a faster speed on the flat. This speed advantage will cause the car to pull ahead of cars with slower \ speeds.

How can the most speed be achieved? By placing weight in the back of the car, thus moving the center of gravity as far \ back as possible while still maintaining stability. Generally, the best results are achieved by removing as much wood as \ possible, and replacing it with weight at the back of the car.

For normal length tracks (under 45 feet), the center of gravity is best located \ between 1 and 1-1/4 inches in front of the rear axle. For longer tracks, the COG should be moved forward proportionally.'; tips[4]='Last week the speed tip related to the effect of the location of the center of gravity of the car on the speed of the car.

If your race \ allows, moving the axles further towards the front and back of the car (either by cutting new slots or drilling axle holes) allows the center of \ gravity to be moved further back, providing a distinct speed advantage. Scouting wood blocks already have the rear slot offset towards the back \ (as are most hobby store blocks), while Awana blocks have the slots equally spaced. If you are in an Awana race and moving the slots is \ allowed, simply buying a new block with offset slots from Maximum Velocity will allow the center of gravity to be moved backward.'; tips[5]='Last week the speed tip related to the effect of the location of the center of gravity of the car on the speed of the car.

If your race \ allows, moving the axles further towards the front and back of the car (either by cutting new slots or drilling axle holes) allows the center of gravity \ to be moved further back, providing a distinct speed advantage. Scouting wood blocks already have the rear slot offset towards the back (as are most hobby \ store blocks), while Awana blocks have the slots equally spaced. If you are in an Awana race and moving the slots is allowed, simply buying a new block \ with offset slots from Maximum Velocity will allow the center of gravity to be moved backward.'; tips[6]='It is very important that the axles are inserted absolutely straight into the car body, and that they are parallel with each other. To ensure that \ this occurs, use a Pro-Body Tool (available from Maximum Velocity) to either drill axle holes, or drill pilot holes in the axle slots. The Pro-Body Tool line \ consists of drilling guides to ensure straight holes. A version of the Pro-Body Tool is available for most brands of pinewood derby kits.'; tips[7]='The smoothness, roundness, balance, and alignment of the wheels are extremely important speed factors. For the next few weeks, the speed tip of the \ week will focus on the wheels.

For this week, here is one obvious, but very important rule to follow:

Attach the wheels/axles to the car after \ all body work is complete. This includes drilling, cutting, shaping, sanding, painting, weighting, and decorating. If the wheels are attached earlier, they \ could be damaged or mis-aligned. Note that this is exactly opposite to the tendency of most young builders, who want to get the wheels on the car right away!'; tips[8]='Here is an obvious, but very important tip:

After completing the car, store the car in a safe place. Do not play with the car, or roll it \ around! This could damage the car and/or mis-align the wheels. There will be plenty of time to play with the car after all of the races are complete.'; tips[9]='The first step in preparing the wheels is to remove any obvious molding marks, burrs, etc. Larger flaws can be removed with an exacto knife. Smaller \ flaws can be removed with an emery board or a small piece of sandpaper.'; tips[10]='Most wheels are not perfectly round, and in many cases the wheel bore is not exactly in the center of the wheel. Polishing the wheel does \ little to improve this type of problem. However, the Pro-Wheel Shaver XT from (available from Maximum Velocity) works like a miniature lathe to \ make round and true wheels. Make sure to use the Pro-Wheel Shaver XT before polishing the wheels.'; tips[11]='The inside wheel hub should be square to the wheel bore before performing any other wheel preparation procedure. This step is accomplished with the \ Pro-Hub Tool (available from Maximum Velocity). The Pro-Hub tool will also ream out undersized wheel bores so that the wheels fit on a wheel mandrel.'; tips[12]='All wheels should have the tread smoothed. This is accomplished by placing the wheel in a drill using a Pro-Wheel Mandrel (available from Maximum \ Velocity), and then lightly sanding the tread with fine (600) grit wet/dry sandpaper. Use a small piece of sandpaper, and dip the paper in water before using. \

With the drill running at a medium speed, sand each wheel for about 10 seconds, making sure that the sanding time is the same for all wheels. \ Also make sure you sand on the inside edge of the wheel.

Use a clean soft rag to wipe the wheels clean after sanding. If desired a polish can be \ applied to wheels with a soft rag, or rub some graphite onto the tire tread.

WARNING: A Dremel-type tool spins at a high RPM, even on the lowest \ setting. If you must use a Dremel-type tool, keep the sandpaper very wet and only apply the paper to the wheel for very short periods.'; tips[13]='If allowed in your local race a speed advantage can be attained by reshaping the wheels. Possibilities include narrowing the wheels, \ cutting a wide groove in the center of the tread, or removing all but a small ridge on the tread. All of these methods improve the speed of \ the car by reducing the wheel inertia.

IMPORTANT - WEAR SAFETY GLASSES - Modifications of this type take some practice, so have some extra wheels \ handy. Place the wheel in mandrel, start the drill spinning (drill must be immobilized), and use an exacto knife to slowly cut the wheel. To keep the plastic \ and knife from overheating, continually apply drops of water with an eyedropper.'; tips[14]='The inside of the wheel bore is generally not perfectly smooth, so polishing the wheel bore will reduce friction by lowering the coefficient of \ friction. To polish, pipe cleaner into the chuck of a drill. Apply some Wheel Bore Polish (available from Maximum Velocity) to the pipe cleaner, slip the \ wheel onto the pipe cleaner, and start the drill. Polish for a few seconds. Repeat for each wheel, then flush thoroughly with water, and air or blow dry.'; tips[15]='The inside wheel hub can be slightly beveled (coned) to reduce contact with the car body. This is easily done with a Pro-Hub Tool (available from \ Maximum Velocity). First use the coarse grit sandpaper, and then the fine grit sandpaper to apply the bevel.'; tips[16]='What kind of weight should you use? Lead is the weight of choice by many car builders. Note that the weights sold by PineCar and other derby \ suppliers are not lead (mostly zinc).

Lead is very dense and pliable, allowing more flexibility in the design and simplifying cutting and shaping. \ Fishing weights are also a good choice as you can buy them in various sizes. Note however, that many fishing weights are now no longer made of lead. \

Since lead is poisonous if taken internally, wash your hands thoroughly after use, keep the lead away from food and water, and reuse or recycle \ lead fragments. Also, do not melt lead as the fumes are toxic.

Many serious car builders use tungsten. Tungsten is a very dense metal that weighs \ the same as pure gold (but not quite as expensive!). Tungsten is about 1.7 times heavier than lead, thus it allows a tremendous amount of freedom in the \ car design. Another advantage is that unlike lead, tungsten is non-toxic and environmentally friendly.

Both lead and tungsten are available from \ Maximum Velocity'; tips[17]='Most scales used at weigh-ins are accurate to 1/10th of an ounce with rounding. Thus, if a car weighs between 5.01 and 5.04, it will register as \ 5.0 ounces, and if the car weighs between 5.05 and 5.09, it will register as 5.1 ounces. Thus, when building a car add enough weight so that it weighs at \ least 5.1 ounces. Then at the weigh-in, remove a small amount of weight at a time until the car registers as 5.0 ounces.'; tips[18]='How important is aerodynamics? Aerodynamics do have an effect, so a low-profile car will outperform a block-shaped car. To ensure that aerodynamics \ have a minimal effect, keep the profile low, avoid a square, "blocky" front end, and avoid the use of streamers, flags, or any other material that could act \ to catch air. Also, round off the back of the car so that when viewed from the side, the rear profile is shaped like a semi-circle.'; tips[19]='Many kits come with axles which are actually nails. These nails have a pair of barbs under the head of the nail which must be removed. To do \ so, mount an axle in the chuck of a drill, start the drill, and use a small file (triangular or rectangular) to grind away the barb. It is also advantageous \ to make a slight bevel on the head of the nail with the flat part of the file. This will minimize the contact between the head of the nail and the wheel hub.'; tips[20]='Nail axles are notorious for being slightly bent. To make sure your axles are absolutely straight and round, use the Pro-Axle Press (available from \ Maximum Velocity). The Pro-Axle Press also makes sure the axle head is square with the axle shaft, and can start the head beveling process if desired.'; tips[21]='Axles need to be polished to a high shine. This is accomplished by mounting an axle in the chuck of a grind, starting the drill, and then \ applying several grades of polishing material. A foolproof way to polish axles is to use an Axle Polishing Kit from Maximum Velocity.'; tips[22]='The clearance between the wheel hubs and the sides of the car should about 30 thousands (0.03) of an inch (essentially the thickness of a credit \ card). Too wide of a clearance will allow the car to zig-zag down the track, while too narrow of a clearance will cause the wheels to constantly rub against \ the car. Use the Pro-Axle Guide (available from Maximum Velocity) to help insert your axles and set the proper gap (of course, you can also just use a credit \ card).'; tips[23]='The first step in aligning the wheels is to make sure that the wheels are placed properly in the vertical direction. Start by placing the \ axle/wheels into the axle slots. Place the car on a level and flat surface such as a kitchen countertop. Use a ruler to measure the distance from the \ countertop to the bottom edge of each corner of the car. Adjust each axle up or down in the axle slot until the four corners of the car are the same height \ above the counter top and all four wheels touch the surface at the same time. If one of the front wheels has been purposely raised, then of course only three \ wheels will touch the surface. Using a Pro-Axle Guide (available from Maximum Velocity) will simplify this process.'; tips[24]='The next step in aligning the wheels is to make sure the wheels are not tilted. Adjust each wheel until the wheels all touch the surface evenly from \ the outside of the tire to the inside of the tire. To ensure that the axles/wheels sit flat, the Pro-Body Tool II (available from Maximum Velocity) can be \ used to create accurate pilot holes in the axle slots.

Some people tilt (cant) axles. This can have a very small benefit in some cases. If you choose \ to tilt the axles, make sure they are tilted evenly.'; tips[25]='The final step in aligning the wheels is to check for toe-in and toe-out. Start by attaching a piece of masking tape (6 to 8 feet long) to a smooth \ surface and level surface. Use a straightedge to make sure the tape is straight. Roll the car on the surface using the tape as a guide. The car should be \ able to roll 6 feet without veering off more than 1". If the car turns within that distance, a correction can be made by either:

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