Okay, I'm just having some fun here, and making up a FAQ for new league racers. If you want to join a League, it's best to have a starting point, and hopefully this thread will be a good start...
Disclaimer: I like using DerbyDad4Hire parts, tools, and supplies to make awesome cars, you can choose the vendor you like. This is just my opinion, and I'm not slamming other vendors parts, I'm sure many of them have good stuff too!
For current Rocky Mountain Derby BASX Rules, check this page: http://www.pinewoodderbyonline.com/threads/rocky-mountain-derby-race-rules.5033/
Best Building Practice: As a general rule, use this guide to first plan your car. If this is your first Pro car, give yourself a month or longer to complete any purchases and your build process. Next, ask an expert any questions you might have about your build. Once you've made all the needed choices, then go ahead and purchase parts, and then when you have all the right parts on hand, begin building your car.
General Plan: You want a basic Pinewood Derby Car, with no fenders or air shields to block the wheel cavities. To be competitive, plan to build a thin low profile car. Always think "thin to win!" You may be able to run your scout's car in this class if you haven't added fenders or air shields, just check to make sure that the wheels you are running meet the requirements, and you are running Nail type axles that meet the rules.
Body: You'll want a quality piece of Pine or Basswood. A standard BSA block can be used, but there are generally better quality blocks available at reasonable prices. Check the DD4H store for the highest quality blocks.
Wheelbase: The standard scout wheelbase is anything but ideal. You'll want to choose a longer wheelbase, but ultimately it's up to you to choose the exact length. The rear wheels should always be positioned as far back as possible, without going past the rear of the block.
Running on 3 or 4 wheels: All pro level racers lift one wheel, and use the DFW or Dominant Front Wheel to steer the car along the center rail. The NDFW or Non-Dominant Front Wheel is lifted just slightly from the track. You can drill your NDFW slightly higher, or even tilt the wheel upwards up to 10 degrees, but most racers using a bent front axle will be able to lift the NDFW about 1/64" simply using the bent axle on the DFW.
Canting the Axle & Wheel: The term "canted" means setting an object at an angle. Thus, "canted axles" are axles which are attached to the car at an angle. Sometimes this is done accidentally, but usually builders cant axles in an attempt to reduce the amount of contact between the wheel and any rubbing surfaces and the track. This can minimize axle to wheel, and wheel to body friction. It's also used to steer the car. A positive cant is set when the running surface of the wheels are angled outward at the tops of the wheels. A negative cant has the wheel tops angled towards each other.
Straight or Bent Axles: For a typical Rail Runner found on Pro Level tracks, One Bent Axle is used for the DFW, and straight axles are found on the rears. Some builders have opted to try and run on bent rear axles, and while you can attempt this, it will be a miracle if you can keep up with the speed of a properly aligned and drilled rear axle car. If you aren't sure what you want to do, plan to drill your rears at 3 degrees and run straight rear axles.
Axle holes or slots: Although you can do either, successful Pro level racers drill their holes, straight for the front axles, and at a 3 degree negative cant for the rears. The alignment is critical for the fastest possible car, use a professional jig like the DD4H Silver Bullet Pro to drill your holes.
Wheel Placement: Consider where the wheels are mounted on the car and how they might touch the center rail of the track. You really only want the DFW to touch the center rail. Do you need to adjust your build to prevent the rear wheels from dragging on the rail and scrubbing off speed for friction? Perhaps you need to narrow the front end on the DFW side by about 1/16 of an inch? Think about this, and ask a League Racer if you aren't sure what to do here...
Chassis Weight Reduction: To maximize your car's weight placement, and get your Center of Mass (COM) as far back as needed to achieve Pro levels of speed, you will want to remove wood from your car body or chassis. You can use anything you like to accomplish this. Aim for a chassis that weighs less than 20 grams, many pro level cars have chassis that weigh less than 8 grams. You may need to design and cut many bodies to learn how to reduce the weight to this level. Don't plan to get that far on your first car!
Stiffness of Chassis: If you remove a lot of wood from the body, you may want to consider the body stiffness. If the wood is very thin you may want to reinforce the wood with a plywood panel or coating the wood with CA glue.
Adding Weights: You spent all that time cutting and sanding your body to get it light and perfect, and now you are going to add all that weight back, and more! 143.0 grams is your goal. First, weigh your 4 wheels and 4 axles together. Then subtract that amount from 143.0 grams. Now you know your total body weight goal. Use Tungsten 1/4" cubes to your body until you can't add another without going over. Use Tungsten Putty to get close to your goal. Use a little more after the car is complete to get exactly to 143.0 grams. You can purchase your weights from DD4H.
Placing the Weights: Generally you want your cubes as far back in the chassis as possible. Many cars use a full 4.0 oz or 24 cubes in the rear to get to their placement. It's also common to fit two rows of 6 cubes behind the rear axle, and just as many cubes placed just in front of the axle. If you aren't sure how to accomplish this, do some homework and check out some of the photos of cars built by other racers.
Center of Mass or COM: You want to get this as close to the rear axle as you can get it without making the car unstable and/or wiggle down the track. The farther back the COM, the higher up the hill the weights are. You may need to experiment on the track by adjusting the weights to see what makes the car the fastest.
Wheels: BASX class wheels are nearly the same as stock BSA wheels, yet they are faster. Plan to purchase Pro Level BASX cut wheels from a well known vendor like DD4H, they will be balanced and lightened to exactly 2.4 grams each and ready to polish.... And polish you must! The Wheel Bore should be polished to a shine and prepared for your lubricant. Pick a proper polishing kit like one sold by DD4H, or order your wheels pre-polished by DD4H! Yes, you can do that!
Axles: Who wants to file and sand and polish the stock BSA Axles? Not me! You shouldn't either, get a better set of Pro Axles from a good vendor like DD4H. They may cost a bit, but they are a much higher quality product, easier to polish, you can order them with one pre-bent axle, with or without grooves, and make sure you get k-house grooves cut in at least the bent axle for easy steering adjustments. If you are feeling lazy, DD4H can polish them all for you for a small fee.
Axle Hole Tightness: Assuming you drilled your axle holes with the right bit you should have a nice tight fit. But is it too tight? Do a test fitting on each axle hole, does the axle sit firm in the hole, but still slide back out without much resistance? If not, you may need to relax the holes so you get a snug, but not too snug fit. Never force your axles into the holes!
Friction Reduction: When possible, plan to use a Delrin Washer on the axle between the body and the wheels of the car to reduce rubbing friction. Yes, this is legal for the BASX class. You can also use a Teflon washer, or some other friction reducing option, but the Delrin Washer is the best option. Attach it to the side of the car so it isn't floating in the wheel gap.
Lubrication: Oil is faster than graphite. You can lubricate your car anyway you like, but nearly all League Racers use a Krytox blend or special oil blend for lubrication. There is an Oil Process for maximum speed, and DD4H can give you some guidance with this as well. With some homework, any racer can use Oil to run at League Racer speeds.
Wheel Gaps: Don't leave a giant gap between the wheel and the body. Push the nail in for a tighter wheel to body gap. If you leave a lot of slop for the wheel to move in you'll end up with a sloppy car.
Airflow: Make sure you cover any holes or cavities in your car body with something like tape, or adhesive vinyl. This goes for the top AND bottom of your car!
Steering: For Rail Running, you want your DFW to just barely steer into the rail using a positive cant. Install your DFW bent axle and wheel with the bend facing down and twist it slightly to adjust the angle until the car begins to steer into the rail. Use a tuning board to measure the turn rate. A good starting point for a car's turn rate is 3 inches of steer over 4 feet of distance. However, track testing may show that more or less steer is needed to find maximum speeds for each car.
Final Thoughts: The ideas above are from my experience building cars. This document is not meant to be the definitive answer to an unbeatable car, you'll need to do your homework and race if you want to be the fastest. Other racers may disagree with me. You may also have your own ideas. Test your ideas. You might be smarter than me! Build a car and get it going fast, then build another car to beat your first car. Repeat. Don't be afraid to ask Pros for help, we might not tell you exactly what we are doing, but we can get you pointed in the right direction. Pros frequently provide some helpful tips, so watch for those!
Have fun racing your toy car! Remember, it is just a TOY CAR!
Click LIKE if you like my thread!
Did I mess up or forget something? Do you think I'm off my rocker? Leave me a comment! I love comments of all sorts....
Thanks!
Disclaimer: I like using DerbyDad4Hire parts, tools, and supplies to make awesome cars, you can choose the vendor you like. This is just my opinion, and I'm not slamming other vendors parts, I'm sure many of them have good stuff too!
For current Rocky Mountain Derby BASX Rules, check this page: http://www.pinewoodderbyonline.com/threads/rocky-mountain-derby-race-rules.5033/
Best Building Practice: As a general rule, use this guide to first plan your car. If this is your first Pro car, give yourself a month or longer to complete any purchases and your build process. Next, ask an expert any questions you might have about your build. Once you've made all the needed choices, then go ahead and purchase parts, and then when you have all the right parts on hand, begin building your car.
General Plan: You want a basic Pinewood Derby Car, with no fenders or air shields to block the wheel cavities. To be competitive, plan to build a thin low profile car. Always think "thin to win!" You may be able to run your scout's car in this class if you haven't added fenders or air shields, just check to make sure that the wheels you are running meet the requirements, and you are running Nail type axles that meet the rules.
Body: You'll want a quality piece of Pine or Basswood. A standard BSA block can be used, but there are generally better quality blocks available at reasonable prices. Check the DD4H store for the highest quality blocks.
Wheelbase: The standard scout wheelbase is anything but ideal. You'll want to choose a longer wheelbase, but ultimately it's up to you to choose the exact length. The rear wheels should always be positioned as far back as possible, without going past the rear of the block.
Running on 3 or 4 wheels: All pro level racers lift one wheel, and use the DFW or Dominant Front Wheel to steer the car along the center rail. The NDFW or Non-Dominant Front Wheel is lifted just slightly from the track. You can drill your NDFW slightly higher, or even tilt the wheel upwards up to 10 degrees, but most racers using a bent front axle will be able to lift the NDFW about 1/64" simply using the bent axle on the DFW.
Canting the Axle & Wheel: The term "canted" means setting an object at an angle. Thus, "canted axles" are axles which are attached to the car at an angle. Sometimes this is done accidentally, but usually builders cant axles in an attempt to reduce the amount of contact between the wheel and any rubbing surfaces and the track. This can minimize axle to wheel, and wheel to body friction. It's also used to steer the car. A positive cant is set when the running surface of the wheels are angled outward at the tops of the wheels. A negative cant has the wheel tops angled towards each other.
Straight or Bent Axles: For a typical Rail Runner found on Pro Level tracks, One Bent Axle is used for the DFW, and straight axles are found on the rears. Some builders have opted to try and run on bent rear axles, and while you can attempt this, it will be a miracle if you can keep up with the speed of a properly aligned and drilled rear axle car. If you aren't sure what you want to do, plan to drill your rears at 3 degrees and run straight rear axles.
Axle holes or slots: Although you can do either, successful Pro level racers drill their holes, straight for the front axles, and at a 3 degree negative cant for the rears. The alignment is critical for the fastest possible car, use a professional jig like the DD4H Silver Bullet Pro to drill your holes.
Wheel Placement: Consider where the wheels are mounted on the car and how they might touch the center rail of the track. You really only want the DFW to touch the center rail. Do you need to adjust your build to prevent the rear wheels from dragging on the rail and scrubbing off speed for friction? Perhaps you need to narrow the front end on the DFW side by about 1/16 of an inch? Think about this, and ask a League Racer if you aren't sure what to do here...
Chassis Weight Reduction: To maximize your car's weight placement, and get your Center of Mass (COM) as far back as needed to achieve Pro levels of speed, you will want to remove wood from your car body or chassis. You can use anything you like to accomplish this. Aim for a chassis that weighs less than 20 grams, many pro level cars have chassis that weigh less than 8 grams. You may need to design and cut many bodies to learn how to reduce the weight to this level. Don't plan to get that far on your first car!
Stiffness of Chassis: If you remove a lot of wood from the body, you may want to consider the body stiffness. If the wood is very thin you may want to reinforce the wood with a plywood panel or coating the wood with CA glue.
Adding Weights: You spent all that time cutting and sanding your body to get it light and perfect, and now you are going to add all that weight back, and more! 143.0 grams is your goal. First, weigh your 4 wheels and 4 axles together. Then subtract that amount from 143.0 grams. Now you know your total body weight goal. Use Tungsten 1/4" cubes to your body until you can't add another without going over. Use Tungsten Putty to get close to your goal. Use a little more after the car is complete to get exactly to 143.0 grams. You can purchase your weights from DD4H.
Placing the Weights: Generally you want your cubes as far back in the chassis as possible. Many cars use a full 4.0 oz or 24 cubes in the rear to get to their placement. It's also common to fit two rows of 6 cubes behind the rear axle, and just as many cubes placed just in front of the axle. If you aren't sure how to accomplish this, do some homework and check out some of the photos of cars built by other racers.
Center of Mass or COM: You want to get this as close to the rear axle as you can get it without making the car unstable and/or wiggle down the track. The farther back the COM, the higher up the hill the weights are. You may need to experiment on the track by adjusting the weights to see what makes the car the fastest.
Wheels: BASX class wheels are nearly the same as stock BSA wheels, yet they are faster. Plan to purchase Pro Level BASX cut wheels from a well known vendor like DD4H, they will be balanced and lightened to exactly 2.4 grams each and ready to polish.... And polish you must! The Wheel Bore should be polished to a shine and prepared for your lubricant. Pick a proper polishing kit like one sold by DD4H, or order your wheels pre-polished by DD4H! Yes, you can do that!
Axles: Who wants to file and sand and polish the stock BSA Axles? Not me! You shouldn't either, get a better set of Pro Axles from a good vendor like DD4H. They may cost a bit, but they are a much higher quality product, easier to polish, you can order them with one pre-bent axle, with or without grooves, and make sure you get k-house grooves cut in at least the bent axle for easy steering adjustments. If you are feeling lazy, DD4H can polish them all for you for a small fee.
Axle Hole Tightness: Assuming you drilled your axle holes with the right bit you should have a nice tight fit. But is it too tight? Do a test fitting on each axle hole, does the axle sit firm in the hole, but still slide back out without much resistance? If not, you may need to relax the holes so you get a snug, but not too snug fit. Never force your axles into the holes!
Friction Reduction: When possible, plan to use a Delrin Washer on the axle between the body and the wheels of the car to reduce rubbing friction. Yes, this is legal for the BASX class. You can also use a Teflon washer, or some other friction reducing option, but the Delrin Washer is the best option. Attach it to the side of the car so it isn't floating in the wheel gap.
Lubrication: Oil is faster than graphite. You can lubricate your car anyway you like, but nearly all League Racers use a Krytox blend or special oil blend for lubrication. There is an Oil Process for maximum speed, and DD4H can give you some guidance with this as well. With some homework, any racer can use Oil to run at League Racer speeds.
Wheel Gaps: Don't leave a giant gap between the wheel and the body. Push the nail in for a tighter wheel to body gap. If you leave a lot of slop for the wheel to move in you'll end up with a sloppy car.
Airflow: Make sure you cover any holes or cavities in your car body with something like tape, or adhesive vinyl. This goes for the top AND bottom of your car!
Steering: For Rail Running, you want your DFW to just barely steer into the rail using a positive cant. Install your DFW bent axle and wheel with the bend facing down and twist it slightly to adjust the angle until the car begins to steer into the rail. Use a tuning board to measure the turn rate. A good starting point for a car's turn rate is 3 inches of steer over 4 feet of distance. However, track testing may show that more or less steer is needed to find maximum speeds for each car.
Final Thoughts: The ideas above are from my experience building cars. This document is not meant to be the definitive answer to an unbeatable car, you'll need to do your homework and race if you want to be the fastest. Other racers may disagree with me. You may also have your own ideas. Test your ideas. You might be smarter than me! Build a car and get it going fast, then build another car to beat your first car. Repeat. Don't be afraid to ask Pros for help, we might not tell you exactly what we are doing, but we can get you pointed in the right direction. Pros frequently provide some helpful tips, so watch for those!
Have fun racing your toy car! Remember, it is just a TOY CAR!
Click LIKE if you like my thread!
Did I mess up or forget something? Do you think I'm off my rocker? Leave me a comment! I love comments of all sorts....
Thanks!
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