Pinewood Derby Car/Physics Question
01-21-2009, 10:38 AM
#16
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I would concentrate on the wheel friction. On my car way, way back when, we shaved the wheels to a point so there was reduced friction. Not sure what the rules say these days.
01-21-2009, 10:42 AM
#17
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Do an internet search on this. There are some crazy websites out there where people have built and tested these things over and over again.
From what I remember the person who has the smallest frontal area with the weight all the way in the back will win.
<------- Thinks there should be a kids division and a dads division at Pinewood derbies.
From what I remember the person who has the smallest frontal area with the weight all the way in the back will win.
<------- Thinks there should be a kids division and a dads division at Pinewood derbies.
01-21-2009, 10:42 AM
#18
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I'm going to take a different approach with this one.
The customer is always right, build it the way your son wants. Remember while it is about learning, if he doesn't have fun then he won't learn, it's his car let him build it his way.
He will see at the races which design may or may not be faster and you can discuss it then. There is always next year to build a faster car.
The customer is always right, build it the way your son wants. Remember while it is about learning, if he doesn't have fun then he won't learn, it's his car let him build it his way.
He will see at the races which design may or may not be faster and you can discuss it then. There is always next year to build a faster car.
The learning comes from the process of building the car, learning how to use tools, father/son bonding, etc.. But make no mistake, the performance of the car and race-day results are all about the father's ego!!
Winning isn't required, but avoiding the embarrassment of last place is an overpowering motivation!John, on race day, spray the axles with a dry lubricant.
The flames, windshield, lego driver, and wrapping the lead ballast with aluminum foil to give it the appearance of an exposed rear engine were all my son's ideas. The flames also served to hold the "engine" in place.
01-21-2009, 10:44 AM
#19
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01-21-2009, 10:51 AM
#20
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No shaving of wheels allowed but we were advised by the troop leader to polish the axles with graphite by placing the axle in a drill and holding a polishing cloth with graphite on the axle.
01-21-2009, 10:54 AM
#21
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Other pics (he took 3rd place, btw)
Note the wheel lift for reduced friction
01-21-2009, 11:09 AM
#22
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Have you guys ever been involved in one of these???
John, on race day, spray the axles with a dry lubricant.
The flames, windshield, lego driver, and wrapping the lead ballast with aluminum foil to give it the appearance of an exposed rear engine were all my son's ideas. The flames also served to hold the "engine" in place.
John, on race day, spray the axles with a dry lubricant.
The flames, windshield, lego driver, and wrapping the lead ballast with aluminum foil to give it the appearance of an exposed rear engine were all my son's ideas. The flames also served to hold the "engine" in place.
01-21-2009, 11:20 AM
#23
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I think I can help here. We never lost a race with the cars we built. There are a few simple things you can do to make your car competitive if not crush the competition. All of the things are within the rules.
Our average victory was by about 10 car lengths. As you can imagine it raised all kinds of accusations. A Dr. whose office was near the church offered to X-ray the car.
Wind resistance is not really a factor. Drag goes up cubed with speed, but the speed thise cars are travelling in is negligible. A block will be competitive with the techniques that follow.
Weight distribution isn’t really a factor either. As long as it is fairly even you're fine.
It’s all about the wheels. There are a couple components to your wheel set up that will make all the difference in the world. First, the axles. They are stamped nails and have a burr on them. The burr needs to be removed and the axles need to be polished. You are going to need a drill press for this and the other operations. Put the axle in the drill press and with a file lightly remove the burr from the shaft and the inside of the head. Then hit it lightly with some emory cloth and then some polishing paste. You are not trying to change the shape of the axle just polish it. I finish up by waxing it with a blend of butchers wax and graphite.
Now you need to clean up the wheels. The hole in the wheel is tapered. This is so it can be removed from the mold. I determined the taper and then put a nail in the drill press and with my file I tapered the nail to match the hole. I then polished the nail. I then pressed the wheel onto the nail and lightly sanded the inside edge of the wheel. You only have to do the inside edge. I then waxed the wheel.
After removing the wheel from the nail I put a piece of tissue on the nail coated with the wax and graphite mixture and waxed the inside of the hole.
Mounting the wheels on the car is probably the most important part. DO NOT use the slots provided. Use the drill press to drill a hole in the side. Use a bit that is the same size or slightly smaller so it will be a tight fit.
The important thing here is to ensure alignment of the wheels. If the wheels are out of alignment you’ll loose a lot of momentum on the guide. The other key thing is to put a camber on the wheels. Two things happen here. With the camber only the inside edge of the wheel is touching the track which reduces the rolling resistance. The 2nd thing is that the wheels move away from the body of the car so they are not rubbing on the body. I made a jig to hold the body of the car at a 4* angle when drilling the holes for the axles.
The car below are two of the four undefeated cars. The blue open wheel was the first one we made. I told my son to pick his fastest hot wheels car and we’d copy that. It was a great exercise in having him figure out how to make that out of a block of wood. The 2nd was the last car we made and was because of the adopt a salmon program from the NH salmon hatchery our Trout unlimited chapter was participating in and that our fish can beat your car.
Our average victory was by about 10 car lengths. As you can imagine it raised all kinds of accusations. A Dr. whose office was near the church offered to X-ray the car.
Wind resistance is not really a factor. Drag goes up cubed with speed, but the speed thise cars are travelling in is negligible. A block will be competitive with the techniques that follow.
Weight distribution isn’t really a factor either. As long as it is fairly even you're fine.
It’s all about the wheels. There are a couple components to your wheel set up that will make all the difference in the world. First, the axles. They are stamped nails and have a burr on them. The burr needs to be removed and the axles need to be polished. You are going to need a drill press for this and the other operations. Put the axle in the drill press and with a file lightly remove the burr from the shaft and the inside of the head. Then hit it lightly with some emory cloth and then some polishing paste. You are not trying to change the shape of the axle just polish it. I finish up by waxing it with a blend of butchers wax and graphite.
Now you need to clean up the wheels. The hole in the wheel is tapered. This is so it can be removed from the mold. I determined the taper and then put a nail in the drill press and with my file I tapered the nail to match the hole. I then polished the nail. I then pressed the wheel onto the nail and lightly sanded the inside edge of the wheel. You only have to do the inside edge. I then waxed the wheel.
After removing the wheel from the nail I put a piece of tissue on the nail coated with the wax and graphite mixture and waxed the inside of the hole.
Mounting the wheels on the car is probably the most important part. DO NOT use the slots provided. Use the drill press to drill a hole in the side. Use a bit that is the same size or slightly smaller so it will be a tight fit.
The important thing here is to ensure alignment of the wheels. If the wheels are out of alignment you’ll loose a lot of momentum on the guide. The other key thing is to put a camber on the wheels. Two things happen here. With the camber only the inside edge of the wheel is touching the track which reduces the rolling resistance. The 2nd thing is that the wheels move away from the body of the car so they are not rubbing on the body. I made a jig to hold the body of the car at a 4* angle when drilling the holes for the axles.
The car below are two of the four undefeated cars. The blue open wheel was the first one we made. I told my son to pick his fastest hot wheels car and we’d copy that. It was a great exercise in having him figure out how to make that out of a block of wood. The 2nd was the last car we made and was because of the adopt a salmon program from the NH salmon hatchery our Trout unlimited chapter was participating in and that our fish can beat your car.
01-21-2009, 12:23 PM
#24
^^^
That's great advise!
A couple of years ago my son and I built one in his cub scout program and we darn near came in last. Then I found out that the kids (read dad's) who won were using drill presses, polishers etc at their machine shop.
We didn't stands a chance !
Porsche GbH would have a hard time competing against these guys !
That's great advise!
A couple of years ago my son and I built one in his cub scout program and we darn near came in last. Then I found out that the kids (read dad's) who won were using drill presses, polishers etc at their machine shop.
We didn't stands a chance !
Porsche GbH would have a hard time competing against these guys !
01-21-2009, 03:36 PM
#25
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I think I can help here. We never lost a race with the cars we built. There are a few simple things you can do to make your car competitive if not crush the competition. All of the things are within the rules.
Our average victory was by about 10 car lengths. As you can imagine it raised all kinds of accusations. A Dr. whose office was near the church offered to X-ray the car.
Wind resistance is not really a factor. Drag goes up cubed with speed, but the speed thise cars are travelling in is negligible. A block will be competitive with the techniques that follow.
Weight distribution isn’t really a factor either. As long as it is fairly even you're fine.
It’s all about the wheels. There are a couple components to your wheel set up that will make all the difference in the world. First, the axles. They are stamped nails and have a burr on them. The burr needs to be removed and the axles need to be polished. You are going to need a drill press for this and the other operations. Put the axle in the drill press and with a file lightly remove the burr from the shaft and the inside of the head. Then hit it lightly with some emory cloth and then some polishing paste. You are not trying to change the shape of the axle just polish it. I finish up by waxing it with a blend of butchers wax and graphite.
Now you need to clean up the wheels. The hole in the wheel is tapered. This is so it can be removed from the mold. I determined the taper and then put a nail in the drill press and with my file I tapered the nail to match the hole. I then polished the nail. I then pressed the wheel onto the nail and lightly sanded the inside edge of the wheel. You only have to do the inside edge. I then waxed the wheel.
After removing the wheel from the nail I put a piece of tissue on the nail coated with the wax and graphite mixture and waxed the inside of the hole.
Mounting the wheels on the car is probably the most important part. DO NOT use the slots provided. Use the drill press to drill a hole in the side. Use a bit that is the same size or slightly smaller so it will be a tight fit.
The important thing here is to ensure alignment of the wheels. If the wheels are out of alignment you’ll loose a lot of momentum on the guide. The other key thing is to put a camber on the wheels. Two things happen here. With the camber only the inside edge of the wheel is touching the track which reduces the rolling resistance. The 2nd thing is that the wheels move away from the body of the car so they are not rubbing on the body. I made a jig to hold the body of the car at a 4* angle when drilling the holes for the axles.
The car below are two of the four undefeated cars. The blue open wheel was the first one we made. I told my son to pick his fastest hot wheels car and we’d copy that. It was a great exercise in having him figure out how to make that out of a block of wood. The 2nd was the last car we made and was because of the adopt a salmon program from the NH salmon hatchery our Trout unlimited chapter was participating in and that our fish can beat your car.
Our average victory was by about 10 car lengths. As you can imagine it raised all kinds of accusations. A Dr. whose office was near the church offered to X-ray the car.
Wind resistance is not really a factor. Drag goes up cubed with speed, but the speed thise cars are travelling in is negligible. A block will be competitive with the techniques that follow.
Weight distribution isn’t really a factor either. As long as it is fairly even you're fine.
It’s all about the wheels. There are a couple components to your wheel set up that will make all the difference in the world. First, the axles. They are stamped nails and have a burr on them. The burr needs to be removed and the axles need to be polished. You are going to need a drill press for this and the other operations. Put the axle in the drill press and with a file lightly remove the burr from the shaft and the inside of the head. Then hit it lightly with some emory cloth and then some polishing paste. You are not trying to change the shape of the axle just polish it. I finish up by waxing it with a blend of butchers wax and graphite.
Now you need to clean up the wheels. The hole in the wheel is tapered. This is so it can be removed from the mold. I determined the taper and then put a nail in the drill press and with my file I tapered the nail to match the hole. I then polished the nail. I then pressed the wheel onto the nail and lightly sanded the inside edge of the wheel. You only have to do the inside edge. I then waxed the wheel.
After removing the wheel from the nail I put a piece of tissue on the nail coated with the wax and graphite mixture and waxed the inside of the hole.
Mounting the wheels on the car is probably the most important part. DO NOT use the slots provided. Use the drill press to drill a hole in the side. Use a bit that is the same size or slightly smaller so it will be a tight fit.
The important thing here is to ensure alignment of the wheels. If the wheels are out of alignment you’ll loose a lot of momentum on the guide. The other key thing is to put a camber on the wheels. Two things happen here. With the camber only the inside edge of the wheel is touching the track which reduces the rolling resistance. The 2nd thing is that the wheels move away from the body of the car so they are not rubbing on the body. I made a jig to hold the body of the car at a 4* angle when drilling the holes for the axles.
The car below are two of the four undefeated cars. The blue open wheel was the first one we made. I told my son to pick his fastest hot wheels car and we’d copy that. It was a great exercise in having him figure out how to make that out of a block of wood. The 2nd was the last car we made and was because of the adopt a salmon program from the NH salmon hatchery our Trout unlimited chapter was participating in and that our fish can beat your car.
I LOVE it!
01-21-2009, 04:33 PM
#26
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Guilty. I did most of the power tools. He was only 9.
He did learn how to use the tools and how to take a complex shape. break it down in to workable portions and then assemble them into the final car. He's crediting that experience to his decision to major in mechanical engineering.
The fish he did all on his own when he was 11.
He did learn how to use the tools and how to take a complex shape. break it down in to workable portions and then assemble them into the final car. He's crediting that experience to his decision to major in mechanical engineering.
The fish he did all on his own when he was 11.
01-21-2009, 04:39 PM
#27
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Great tips guys ! I do my first Pinewood Derby this Sunday with Indian Guides (YMCA). I'll get to polishing those axles and wheels.. Have no drill press, but the removal of the axle burr and polishing/waxing the wheels will help.
01-21-2009, 04:52 PM
#28
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Can you clamp a regular drill in a bench vise to pretend it's a drill press. Guess the hard thing would be securing the work object firmly in relation to the drill.
So no molybdehum di-sulfide allowed for lube.
So no molybdehum di-sulfide allowed for lube.
01-21-2009, 05:04 PM
#29
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You can de-burr and polish by holding or clamping the drill in a vise. It's drilling the holes for the axles that requires the drill press.
01-21-2009, 07:23 PM
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Get this book, learn it, live it love it and win BIG. Very easy for a young builder to read and follow directions. My Grandson won his division and no one was even close. I would sell you my copy but I have another grandson who will be building one in a few years.
http://www.amazon.com/Pinewood-Derby.../dp/0756627338
http://www.amazon.com/Pinewood-Derby.../dp/0756627338