On the HWC site someone ask why would cars perform differently at different track heights. KIR track owner and long time Hot Wheels racer Rick Ways posted an amazing answer that I thought might be beneficial to all that are building cars or might in the future.
Here is Ricks reply and a follow-up (used with permission):
Tips from Rick Ways, Part 1
I'll put both responses in one PM, you will have to cut and paste some info from one to the other for it all to make sense. Or just post all of both replies
Believe it or not, there is a lot more to building a custom car and having it run good than meets the eye, or you would believe.
I having been doing these custom race builds for several years now and I have test built all types of Hot Wheel castings, Some make good race cars and some don't, it is all a matter of time, patients and LOTS of testing Big Grin
Now there are always exceptions to rules but in general, you want to start with a casting that has a wide and long footprint, ie the Lamborghini Estoque, Cadillac V-16, Unobtainium etc. You want this type of casting because weight placement in all castings is important. Some like the weight more forward, some like it centered and some like more weight in the back and with these wide and long type casting, the base provides a lot of room to achieve the optimal placement(again, LOTS of testing or trial and error).
Axles and wheels are the key component to any build and again there are always exceptions to the rules. Generally, you want to stay away from small diameter wheels, they just have to work harder(make more revolutions) to achieve speeds and they tend to not like the added weight. I tend to find that medium/medium, medium/large or large/large wheel combinations work the best, just depends on the casting(again, LOTS of testing). Now just using a stock set of axles and wheels does not always cut it, you have to do some work on both to achieve the best speeds/results. Most axles, reguardless of whether they are FTE/nickel type or just regular mainline usually require some filing/sanding to remove burrs/imperfections at the penned end of the axle. You can tell this by just spinning the wheel by hand, some spin freely and for a long time, while others are bumpy/rough and do not spin very well or for very long, hence, these require some tuning. Almost every wheel has a mold injection spot on it and you can feel this by slowly spinning the wheel while placing you finger or finger nail on the wheel. In addition, almost all wheels are not perfectly round and or smooth. You most do some tuning to the wheel to achieve the round/smooth variable so the car goes down the track as smoothly as possible. I have my way of doing this while others have there way but in the end, if you do not perform this action, cars that do have tuned wheels, will blow right by you on the track.
There are several other things to do and check and I could probably wright a book on this but I'm not gonna go into all the other stuff at this time, again, its a matter of time, patients and testing.
Once you have the desired casting, weight placement for desired class and your axle/wheels tuned, it's time to go testing. You may not hit the nail on the head the first time out and most do not, this is why I say, testing, testing and more testing as you will probably have to shift your weight placement several times to get it right and you may even have to go thru several sets of axle/wheel combos to see what works and what doesn't, again, getting the concept, LOTS of testing Big Grin
Now you finally have your build together and running at its best, so lets go racing. The car shows up at a meet with many other builds and this is where you really get to see how you did, which leads into the racing series events I host on this site. It takes some builds several tries/events to get the perfect build, some it take many events but the key is not to give up trying as it takes LOTS of testing Big Grin to build a car or team of cars that consistantly run in the tops of the classes and yes, in most cases, there is always someone out there that has abetter car than you but again, keep at it and LOTS of testing and you will one day end up with a winning car!!! I've had several builds that started out on the bottom of pile but after a while and LOTS of testing, they are now some of the better builders with some of the fastest cars!!!!
Okay, enough of that, now lets try and answer your original question. In most cases, most cars do hold to aperformance increase as the angle changes but this increase is also relative to what and how you built your casting. This is were the 2 different series I run come into play, are you going for the win in side by side action or are you building for pure speed, there is a difference!!! This is where all the factors I rambled on about earlier come into play. Building side by side racers generally require a good mix of castings, axle/wheel combinations and different weight placements so they can handle the change in track angles in each round(now not everyone changes the track height but I do). All these factors are keys to having a good fast car at all track angles but once again, LOTS of testing is the key to obtaining a great running car. Building for speed or in our case, track record ET's and speeds, only one track angle is used, thus the build is different from side by side racing with the most notable difference being wheel size. Medium or large wheel combinations just have to work less and obtain better results than small wheels, simple math to determine this as the med/large wheels handle weight distribution better and again have to work a whole lot less than small wheels.
In short, most cars do better and have a consistent performance gain as the track angle changes but there are some that do not gain as much or as consistantly as others, remember, these are just toy cars and there is only so much you can do but if you do it right, they can go really fast!!!! One other thing, there is a certain point or track height at which all or most cars no longer get or gain performance increases and I have tested in a huge range of heights from floor level to 10 feet off the floor. Some cars just do not like heights above 5 to 6 feet and some do, again and for the last time, LOTS of testing is the key.
Did I ramble on about a lot of nothing or did this make any since???? I could probably explain a lot better in person but for now, the keyboard will have to do but if you have any questions, call or PM me or just ask some of the builders/racers that run in these events, they can tell you a thing or two also Big Grin
Tips from Rick Ways, Part 2
Hello - I need to move this to a PM to try and better answer your questions.
"What I failed to get in your message was some kind of explanation as to why a car might win at one incline but lose at another.
Let's say there are 20 cars. And at a 20% incline, mine wins. But when moved to a 30% incline, it comes in 10th. What would be the suspected reasons that the car would not do as well at a higher incline?"
In a perfect world and given that all things are equal, a car at one incline would and could win at all levels of incline. However, things are not always perfect or equal. You have to remember, we are dealing with Hot Wheels, not real cars.
As I explained in the reply, there are many factors that could lead to winning at one level but not at another. One factor is what size wheels are used. The same physics apply to diecast as they do to real life. Small wheels are good for fast starts but have lower top speed while medium/large wheels have a slower start but better top speed so depending on what you use, it does make a difference. So lets say you build car #1 with all small wheels and car #2 has all large wheels. In most cases, car #1 will get the advantage off the starting line and lets say for example that by 2 feet out on the track, car #1 has a 2 car length lead, now depending on how long the track is and lets use a few examples, track #1 is 20 feet long and track #2 is 40 feet long. on track #1, car #1 has a much better chance of winning because car #2 cannot get up to top speed in time so on track #1, car #1 wins by 1 car length, car #2 did close the gap but not in time to win. Now on track #2, car #1 had a 2 car length but because of the added length of the track, car #2 was able to catch and pass car #1 because car #2 has larger wheels and by the 40 foot mark, it can and has achieved a better top speed.
Car weight also plays in as a factor when using different size wheels. Small wheeled cars have less surface area to distribute the weight and or support the weight. By adding weight to a stock out of the package car, you are applying pressure to the axles. The smaller wheeled car has more pressure being applied to a less supporting surface area, thus causing more friction between the wheel and axle so it causes the wheel to work harder to obtain the same speed as a larger wheel, again, it is a friction thing and the larger wheel just has to work less to gain the same or more speed than a smaller wheel.
Now lets move to the actual incline change part. Given what I stated above, at a starting line height of 50 inches and a track distance of 40 feet, the weight and wheel size have a lower or smaller friction ratio because lets say the top speed is 40mph at the 40 foot mark but when you move the starting line height up to 60 inches the friction ration increases because the wheel is turning faster and the top speed is now 50mph. The friction ratio on a small wheeled car is now at 100% because it can only go this fast, no matter how high or at what incline the track is. On a large wheeled car the friction ration is only at 70% because it has a larger surface area and has to make less revolutions, thus providing a higher top speed. All cars max out on top speed at different height levels or inclines and track distances.
Now there are always exceptions to the rules but in most cases, the following applies. Shorter track and smaller wheels will generally win, longer tracks and larger wheels, the larger wheels will win. This is why weight placement and axle/wheel tuning as I stated in the reply are key factors in making a fast car. So in short, one car may be good or win on one track incline and distance but not do good on another track incline or distance. It comes back to a testing thing.
"The added question due to your explanation is what is the difference between side-by-side racing and racing for time? To put it another way... If my car is the fastest of 20 cars, the way I see it, it will be the fastest whether it runs at the same time another car is beside it or whether it runs alone. Perhaps I don't understand side-by-side racing."
Because I use a single laser starting beam type gate on my track, the times are different between side by side racing and running just for time. In real life racing, there is a beam for each lane but because this is not possible with a single laser beam start gate, in side by side racing, the timer starts with which ever car breaks the beam first to start the timer so there is no 'reaction time' for each lane as there is in real life. Actually because of the way these laser beam starts work, the end result ET are some what skeewed because one car breaks the beam to start the timer but at the finish each car has to break its own beam to stop the timer so the car that does not break the beam at the start is working or running off the initial 'start time' of the car that did break the beam. Generally, the times are a little slower because of this. Running just single runs or runs for time, because there is only one car to break the beam or start the timer and one car to stop the timer, the timers are faster because the one car is getting more of a true reading because it started and stopped the timer. It's kind of hard to explain this really, you really have to see this in person to get a better understanding but this is why I do 2 series of racing, side by side and record runs.
Now there is also a difference in the side by side vs the record runs in that in the side by side racing, the first round starting line height is set a certain height from the floor and as we move thru the rounds, I move the starting line height up by 2 inches for each round so if there are 32 cars in the race, to get down to the final 2 cars, there are 5 rounds of racing so the starting line goes from 58 inches to start to a final round height of 68 inches. Where as the Record Runs are all done from the final round height of 68 inches.
Now to go back a little to the first part of the question, when the starting line height is raised for each round, not all cars gain speed or have better ET at the same rate so again a car that wins or does good at one height may not do good or be the fastest at another height and again, car weight and wheels play a large part in this. Another factor is how much wiggle the car has going down the track. If a car has a good set of wheels/axles that allow it to run true and straight, it may only bump the track rails once or twice the entire run but if your axles/wheels are not true, it may bump the side rails 6 or 8 times on the run and this causes the car to slow down. Because of this 'wiggle factor' your car may not run good at the lower height because it cannot get up to speed to compensate for the wiggles, where as at a higher height the weight of the car can compensate for the wiggles because the weight of the car can somewhat control how straight the car runs.
You really have to setup a track and do your own testing to see what I am talking about and some of the folks that build and send cars to car do not have a track to test on so it puts them at a huge disadvantage over those that do. Now not all track are or will be the same even if you set them up at the same incline and distance but by at least having some kinda track setup, you get a feel for what the car should do on another track.
I've been building and testing cars for about 10 years now and have probably built and tested over a 1000 custom cars for racing, it is just a matter of preference, time, patience and testing to see what works and what doesn't. You really just have to 'do it' to get or see the answers to your questions. I like many other of the builds can provide tips and insight as to what to build and how to build it but in the end, it is up to you to build it, test it then go race it against another car. I specialize in axle/wheel tuning as this to me is the most important thing about racing these cars. If your axle/wheel combo doesn't spin freely and smoothly, you will have virtually no chance of winning or being the fastest. I do a lot of the axle/wheel work for most of the builders that run in my events because they can see the difference of what I do on there times and speeds after I tune them vs what they send in originally. A typical test session for me or you, when you send me a car consists of giving the car one test run to break everything in, then I give the car 2 runs in each lane and provide the builder with the times and or in some cases the speeds, then I go to work on the car by sometimes having to take it apart to work on the axles, then tuning the wheels and by tuning the wheels I mean, making them round and smooth so the car glids down the track. Then I work on weight and weight placement, this sometimes takes several tries before finding the optimal weight and placement for the wheels the builder wants to use. Once I have things set or built to my liking, I give the car another break-in run, then do 2 more runs in each lane and send the builder back the new times and or speeds and in most cases, with the work I do I gain give a car anywhere from .020 to .100 difference. So if the car initially runs a time of 3.500 on what you built I can make it generally run 3.480 or 3.400 which is a big gain when we come to talking about a 32 car field and could be the difference between qualifying #1 or #32.
Like I mentioned in the previous response, I could probably write a book on all this. There are a lot of other things to consider as well such as a dry lube vs a wet lube when doing the axles/wheels and there is a lot of debate amongest the builds as to which is better but once again, it is a testing thing and up to you decide which work better on your build. There is the casting decision also, I prefer a longer and wider casting as they are easier to work with but I can build any casting and make it go fast. How much weight is another factor, do you want to go the allowed weight limits for a 2 or 4 oz class or does the car run better with a little less than the max weight allowed, again its a testing thing. For example and to kind of go back to your question, a while back, I built a wedge dragster that weighed in at 72.1 grams, now I strictly built this car for speed and time, I set and held the track ET and speed records for over 2 years with this car. Because it weighed in at 72.1 grams, when it came to the side by side racing, it had to run in the 4oz class, which is and was a huge disadvantage because the heavier cars could get off the starting line faster and gained to much of a lead for my car to make up. So you see, it was the fastest as far as running for records but not the fastest when racing against another car of greater weight. So how much weight plays a factor in side by side racing vs record runs as a car does not always have to weigh a lot go fast but helps when running against another car.
Okay, Ive rambled enough but feel free to PM me any time with any questions and I will try and answer or provide input as best I can.
Feel free to build some cars and send them in for the race events or give them a try at the records. you can always send them in for testing if nothing else and see how they do and I can provide insight on what you need to do to make it better or you can let me tune them and show you the difference, then you can apply this to your next build and see the difference.
One thing I did not talk about or mention is the 'just because factor' some things cannot be simply answered and they happen 'just because', these are diecast cars that are under gravities control, not a human factor control and they happen 'just because'.