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Old 01-08-2020, 06:30 PM
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Should my son select a heavy or light Hot Wheels for a Hot Wheels race?


Next weekend, my son and I are going to a Father-Son camp and they are having a matchbox car race tournament/competition.

You can see last year's competition here to get the idea. They put the cars on a ramp "pinewood derby" style and race them.

Anyway, I thought he should choose a heavier vehicle, though he thinks lighter ones would be faster. I have a postal scale to weigh them down to the ounce.

When I did pinewood derby as a kid, we always added weights on the bottom to make them heavier(within the weight limits, that is). Same idea? Heavier is better? He'll probably choose a few cars.

Thanks
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Old 01-08-2020, 06:50 PM
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I'm with you. I'm not sure about the physics, but heavier Pinewood cars always seemed to win back when I was a sprout.
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Old 01-08-2020, 07:00 PM
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Total weight doesn't matter that much (within a reasonable range).

The important things to win Pinewood derby are minimizing friction (make sure the wheels spin freely) and getting the weight as far back in the car as you can go. Because the cars start on a slope, weight in the back of the car means more potential energy at the start, which means more speed at the bottom.

The optimal Pinewood derby car is as long as possible (because you win when the front crosses the finish line, but you get potential energy based on the center of mass, which will be higher for a longer car), has most of its weight in the back, and has just three well-lubricated wheels to reduce friction (Seriously: see if you're allowed to break off one of the front wheels).
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Old 01-08-2020, 07:08 PM
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Why don't you and he do some experiments putting cars head to head on a test slope. Doesn't have to be anything fancy. Good way to figure out which of his cars is best, and make some hypotheses, collect some data. . . . It's a much better way to learn than, "I asked the internet; here's what they said."
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Old 01-08-2020, 09:31 PM
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Total weight doesn't matter that much (within a reasonable range).

The important things to win Pinewood derby are minimizing friction (make sure the wheels spin freely) and getting the weight as far back in the car as you can go. Because the cars start on a slope, weight in the back of the car means more potential energy at the start, which means more speed at the bottom.

The optimal Pinewood derby car is as long as possible (because you win when the front crosses the finish line, but you get potential energy based on the center of mass, which will be higher for a longer car), has most of its weight in the back, and has just three well-lubricated wheels to reduce friction (Seriously: see if you're allowed to break off one of the front wheels).
Aren't the weights of pinewood derby cars strictly controlled? Which is why the derby participants try to gain advantage by distributing the weight in different ways?

The car is going to have a fixed amount of wind resistance. Rolling friction will be a function of the weight of the car, as is potential energy. It's possible that a vehicle could have such a poor suspension and wheel setup that friction would rise with weight faster than the gain in potential energy, but for a hot wheels in a reasonable weight range I would bet that heavier is better.
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Old 01-10-2020, 06:08 PM
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Aren't the weights of pinewood derby cars strictly controlled? Which is why the derby participants try to gain advantage by distributing the weight in different ways?
..
No heavier than 4 oz, iirc.
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Old 01-08-2020, 10:02 PM
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I agree that the best thing to do is test all the cars he has.

Weight will make a difference if the wheels have significant friction. If two cars have the same amount of friction, the heavier one will roll better. And friction increases as the cars get older. So try putting some lube on the wheels/axles and see if they roll better.
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Old 01-08-2020, 10:42 PM
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If the only forces involved were gravity, normal force, and dry friction, then the weight of the car would be irrelevant, since all of those forces are proportional to mass.

But those aren't the only forces. Air resistance is also present, and extremely relevant. And it is not proportional to mass. So you want the mass as great as possible, to reduce the relevance of air resistance.

That said, eschrodinger has the best answer: Do the experiment. Learning about how science works is a far more valuable lesson than just learning which car is best. If he wonders why the heavier car wins, that's the time then to explain about air resistance.
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Old 01-09-2020, 12:45 AM
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+1 to doing some testing. Like real cars, how the Hot Wheel (forget Matchbox <grin>) weight distribution may matter more than weight. My 50 year old memories are that even identical cars can differ in speed. As I recall, the original Camaro, on the first to be introduced was amongst the fastest and the Stilletto was among the slowest.

More important than weight, make sure the wheels are straight and true in line with each other and put a tiny drop of 3in1 oil or probably better some new lightweight spray lube or even graphite on the axle. The oil/graphite may be viewed a cheating, but aligning the wheels is part of regular tuning. There was/is a tool for for.

Edit: Like pinewood derby, watch the lanes. One will always be faster than the other.

Last edited by lingyi; 01-09-2020 at 12:46 AM.
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Old 01-09-2020, 02:54 AM
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Here's Mark Rober, telling you everything you need to know about what makes for a winning car.

Last edited by Xema; 01-09-2020 at 02:56 AM.
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Old 01-09-2020, 11:54 AM
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Dammit! I was gonna post that exact same video. For those who don't recognize the name, he's the porch pirate glitter bomb guy.
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The optimal Pinewood derby car is as long as possible (because you win when the front crosses the finish line, but you get potential energy based on the center of mass, which will be higher for a longer car), has most of its weight in the back, and has just three well-lubricated wheels to reduce friction (Seriously: see if you're allowed to break off one of the front wheels).
Apparently not. Rober's model in his video has four wheels, but one raised so that it is cosmetic only.
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Old 01-09-2020, 12:03 PM
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Apparently not. Rober's model in his video has four wheels, but one raised so that it is cosmetic only.
Most districts require all four wheels to be present, but not necessarily touching the racing surface.

Here is our rule, as an example: "Each car must include 4 “approved” wheels (wheels that meet the above criteria) and placed in the“normal” wheel position for a car. “Normal” position is 2 mounted on each side of the car and parallel to each other. Wheels may be staggered on each side of the car (See image 9). At least three (3) wheels must remain in contact with the track at all times. Although the 4th wheel does not need to contact the track, it must act as a guide to keep the car on the track against the center rail. Use of any other type of guide pin, fin or any other device is prohibited. No 3-wheeled cars."
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Old 01-10-2020, 06:04 PM
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which was?
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Old 01-09-2020, 09:26 AM
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If the only forces involved were gravity, normal force, and dry friction, then the weight of the car would be irrelevant, since all of those forces are proportional to mass.

But those aren't the only forces. Air resistance is also present, and extremely relevant. And it is not proportional to mass. So you want the mass as great as possible, to reduce the relevance of air resistance.
I think also that the rolling resistance isn't very close to the simple friction model (where the frictional force is directly proportional to the normal force/weight). I strongly suspect there's a pretty big constant term (independent of the normal force), which would also add to the speed-weight dependence.

But again, best way to answer this is the Mythbuster's way: try it out!
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Old 01-10-2020, 06:03 PM
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If the only forces involved were gravity, normal force, and dry friction, then the weight of the car would be irrelevant, since all of those forces are proportional to mass.

But those aren't the only forces. Air resistance is also present, and extremely relevant. And it is not proportional to mass. So you want the mass as great as possible, to reduce the relevance of air resistance.
....
We experimented with Pinewood derby cars. Once you cut down air resistance, the heavier the faster. No doubt.
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Old 01-09-2020, 09:14 AM
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True, there may well be differences in things like wheel alignment that would make one car faster than another, completely independent of weight. Finding those is another advantage to experimental testing.

And as an added bonus, it gives you an excuse to play with Hot Wheels with your kid.
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Old 01-09-2020, 09:41 AM
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There's other kinds of friction than dry friction and air resistance. The axle may be corroded or there may be dirt in the axle-wheel interface. Older cars will have greater amounts, as a general rule. Lube will help but not completely eliminate them.
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Old 01-09-2020, 09:44 AM
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Rolling resistance might not be proportional to weight, either, but I'm pretty sure that it goes the other way, such that it'd be totally insignificant for a toy car. Rolling resistance comes from changing deformation of the wheels, and I highly doubt that the deformation of a Hot Wheels car's wheels under its weight is even measurable.
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Old 01-09-2020, 04:18 PM
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Rolling resistance might not be proportional to weight, either, but I'm pretty sure that it goes the other way, such that it'd be totally insignificant for a toy car. Rolling resistance comes from changing deformation of the wheels, and I highly doubt that the deformation of a Hot Wheels car's wheels under its weight is even measurable.
But also from misalignment of the wheels, and alignment does change with the weight of the cars -- at least it does on corners and at run-outs.
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Old 01-09-2020, 10:27 AM
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Next weekend, my son and I are going to a Father-Son camp and they are having a matchbox car race tournament/competition.

You can see last year's competition here to get the idea. They put the cars on a ramp "pinewood derby" style and race them.

Anyway, I thought he should choose a heavier vehicle, though he thinks lighter ones would be faster. I have a postal scale to weigh them down to the ounce.
Is he allowed to build his own vehicle, or is this a race of Matchbox and/or Hot Wheels cars?
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Old 01-09-2020, 10:32 AM
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I always thought that the old-style Hot Wheels cars with spring suspension were the best. Each wheel spun independently of the other, and any Hot Wheels car could beat any Matchbox car.
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Old 01-09-2020, 10:40 AM
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Oh, one other point that could theoretically be relevant (but probably isn't very): You want as low a proportion as possible of the weight to be in the wheels. Weight in the wheels will result in some energy being wasted in rotational kinetic energy, instead of translational kinetic energy. To see this effect most clearly, roll four objects down a ramp: A ring or hollow cylinder, a solid cylinder (like a hockey puck), a hollow sphere (like a basketball), and a solid sphere (like a super-bounce ball). Size and density don't even matter. The solid ball will always win the race, followed by the solid cylinder, the hollow ball, and in last place the ring, because the solid ball has most of its mass close to the axis of rotation, while the ring has all of its mass far from the axis.
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Old 01-09-2020, 10:46 AM
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I know it is pricey, but consider adding nitrous oxide to your system.
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Old 01-09-2020, 10:51 AM
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I know it is pricey, but consider adding nitrous oxide to your system.
They are racing toy cars.
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Old 01-09-2020, 11:02 AM
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They are racing toy cars.
Which is why NOS is pricey, since it has to be scaled down.
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Old 01-09-2020, 11:12 AM
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Which is why NOS is pricey, since it has to be scaled down.
There would be no way to hide such a setup, and I'm pretty sure such a device would disqualify the car.
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Old 01-09-2020, 12:33 PM
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There would be no way to hide such a setup, and I'm pretty sure such a device would disqualify the car.
Miniature warp drive, then. See if you can punch holes in that suggestion.
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Old 01-09-2020, 09:16 PM
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There would be no way to hide such a setup, and I'm pretty sure such a device would disqualify the car.
I used to have a nitrous oxide-equipped car. The nitrous system can be hidden. The internal combustion engine that burns the nitrous would be hard to hide, especially on a little pinewood derby car.
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Old 01-10-2020, 01:40 AM
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There would be no way to hide such a setup, and I'm pretty sure such a device would disqualify the car.
Imagine being this person.
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Old 01-10-2020, 04:19 PM
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There would be no way to hide such a setup, and I'm pretty sure such a device would disqualify the car.
That is the main reason such a setup would be so pricey. Hard enough to scale a Nitrous Oxide system to that size, but masking it so the judges won't notice is VERY pricey!
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Old 01-10-2020, 06:06 PM
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Which is why NOS is pricey, since it has to be scaled down.
They have no engine. It's just gravity.
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Old 01-09-2020, 09:43 PM
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I know it is pricey, but consider adding nitrous oxide to your system.
That would certainly make the race more fun, but getting stoned would not improve the performance of your car.
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Old 01-09-2020, 11:25 PM
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That would certainly make the race more fun, but getting stoned would not improve the performance of your car.
You won't care.
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Old 01-10-2020, 12:48 AM
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For once, a general question that I am a semi-expert at. As a Dad, I am a successful veteran of 5 Pinewood Derbies and one Lego Derby. I also run dozens of Hot Wheel races per week as part of my job.

With Pinewood Derby/Lego Derby races, the Mark Rober model works (as heavy as allowed, low profile, weight in the back, sanded axles with graphite). I had three kids go through Cubbies and we got a few trophies, always in the top 5.

I work with kids. When they do well, they can play in my office with a toy of their choosing. I have a Hot Wheels track that unfolds to make a four lane race track. I have a bin full of cars. Kids bring in their own cars to challenge my cars. I race a lot.

My observations: In general, cars that say “Made for track” or mention that they are meant for usage on a track are going to win. In general, these cars follow the Mark Rober model- heavy, low, with weight on the back. Look at the cars that are included with race tracks to get a general feel of what track cars look like.

That being said, not all these cars are always the fastest. There are some cars that are consistently fast that don’t follow the above model at all. In general, cars get slower the more you use them. Not all cars are consistent day to day. On some days they run fast, and on some days they are a step slower. However, in general, your top five cars stay your top five cars.

My recommendation is to buy 10 cars, test them out, and see which one wins the most.

Last edited by Mesquite-oh; 01-10-2020 at 12:48 AM.
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Old 01-09-2020, 01:27 PM
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Hijack but is a race between Hot Wheels/Matchbox cars a replacement for the old pinewood derby race held by the Boy Scouts? Because as I remember, building a pinewood derby car required the kid or parent to do some carpentry and lots of families aren't set up to do that stuff.
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Old 01-09-2020, 02:11 PM
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It may be worth doing trial runs on a bare slope, not an actual track. That would make it obvious if the wheels are misaligned (i.e. car won't go perfectly straight).
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Old 01-09-2020, 04:07 PM
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Hijack but is a race between Hot Wheels/Matchbox cars a replacement for the old pinewood derby race held by the Boy Scouts? Because as I remember, building a pinewood derby car required the kid or parent to do some carpentry and lots of families aren't set up to do that stuff.
I don't think so. Pinewood derby races are still pretty big. I figured this was just something they had at the camp we're going to.


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Also consider the long-term social status benefit of having the coolest car going down the track, rather than the fastest.
The plan I have is to have one fast one and one that we just pick because it's cool.
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Old 01-09-2020, 07:19 PM
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I think we have just seen the elusive double Whoosh with Czarcasm's responses to Kayaker
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Old 01-10-2020, 02:26 AM
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Back on topic. Hot Wheels and Matchbox!

This is definitely cheating! https://www.racehotwheels.com/2017/0...ar-faster.html

As I posted earlier, the easiest and quickest way to make your Hot Wheel faster is to align the tires. If you look at the car from below, even right out of the package, the tires aren't perfectly in line with each other and straight. Just like your real car, misaligned tires will cause it to drift right or left. This is critical for Hot Wheels because every time they touch the side of the track they slow down. Johnny Lightning cars were touted to be faster than Hot Wheels and most of them were. However, a least one model had little plastic headers that would touch the sides of the track and was slower than the Hot Wheels.

Proof that weight isn't everything is that early Matchbox cars were generally heavier than Hot Wheels, but because of the different types of axles were slower than them. After all, that's what Hot Wheels were all about, being faster than other diecast cars. The same marketing done for Johnny Lightning, faster than Hot Wheels.

And finally, what may be the definitive answer. Note that weight isn't the only factor. http://www.racehotwheels.com/2016/02...-you-need.html

My memory is strong and my Google Fu even stronger!
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Old 01-10-2020, 10:00 AM
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Well obviously weight and alignment aren't the ONLY factors. You also need flame decals on the sides. Everyone knows those make a car go faster.
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Old 01-10-2020, 06:06 PM
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Well obviously weight and alignment aren't the ONLY factors. You also need flame decals on the sides. Everyone knows those make a car go faster.
Don't forget the speed holes.
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Old 01-11-2020, 12:59 AM
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Well obviously weight and alignment aren't the ONLY factors. You also need flame decals on the sides. Everyone knows those make a car go faster.
Of course! That's why Hot Wheels are faster than Matchbox. The name is IN a flame decal!
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Old 01-10-2020, 09:26 PM
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Heavier builds more momentum. Once off the slope, rolling friction provides a constant drag, fairly speed independent. With more momentum, the heavier vehicle will resist that drag longer,
You will not get anywhere near speeds where wind speed will be a major, and mass independent factor.
When I raced them, the heavier cars always won, barring cruddy bearings etc.

Last edited by Squink; 01-10-2020 at 09:27 PM.
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Old 01-11-2020, 01:05 AM
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The Mythbusters talked about and tested the physics of Hot Wheels...err Johnny Lightning cars on a Hot Wheels type track in Toy Car vs Real Car. https://is.nisd.us/apps/video/watch.jsp?v=72436
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Old 01-11-2020, 11:53 AM
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Quoth Squink:

Heavier builds more momentum. Once off the slope, rolling friction provides a constant drag, fairly speed independent. With more momentum, the heavier vehicle will resist that drag longer,
You will not get anywhere near speeds where wind speed will be a major, and mass independent factor.
When I raced them, the heavier cars always won, barring cruddy bearings etc.
A lot to unpack, here. First, rolling resistance is proportional to speed. Second, it's not a big factor here, because it's based on the deformation of the wheels. What you're probably thinking of is friction with the axle, which would behave as dry friction. Third, the relevant question is not whether it depends on speed, but whether it's proportional to the mass, which both rolling resistance and dry friction are, so if that were all that were relevant, the heavier car would have more momentum but also more resistive force, and end up with the same acceleration and hence same speed at every moment. Fourth, such cars are absolutely at a speed where air resistance is relevant, for them. Air resistance at that speed would be negligible for a real car, but that's because real cars have much more mass. The more mass you have, the less relevant the air resistance is, which is why we want more mass.
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Old 01-11-2020, 01:13 PM
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rolling resistance is proportional to speed. Second, it's not a big factor here, because it's based on the deformation of the wheels.
Some of it is not from wheel deformation, but simply from two surfaces, not perfectly smooth, moving past each each other. A hair on the track, or similar, or just track roughness, has its own speed dependent cost. Wood and rubber, or hard plastic, do not slide past each other with zero friction, even with no significant deformation. I may very well have wind resistance wrong, as I'm thinking of cars massing half a kilo. It will be an issue for say 100 gram cars,
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Old 01-11-2020, 01:40 PM
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Imagine being this person.
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They have no engine. It's just gravity.
Demonstrably, there are worse fates.
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Old 01-11-2020, 03:32 PM
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Demonstrably, there are worse fates.
Sometimes the best answer to a bad whoosh is a deadpan correct answer.
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Old 01-11-2020, 12:49 PM
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We tested all of my son's cars down in the basement, using a table as a long ramp. Not idea and not identical to the final races, but enough to get a feel for which cars were fastest. We picked the top two fastest.

Then today, I took him to the store and said if we can find any FTE cars or anyting specific for racing, I'll buy it for him and we can take those.

We picked two cars at the store that were, by complete coincidence, almost identical to the used ones we found to be fast yesterday. They are labeled "best for track racing" on the box and we're hopeful they will work well since they are new in the box.

I can report back with how it goes after next weekend!
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Old 01-11-2020, 04:25 PM
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Another factor for Hot Wheels is that the early production tires have a lip on the inner edge, reducing surface contact which may increase or reduce speed. https://onlineredlineguide.com/wheels/wheels.html

In the tweaks link I gave above, the first tip is sanding the tires, which I assume is to increase the tires grip, but also would reduce of remove the lip.
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