Recent content by CFD Engineer

As everyone has said, don't mix the two, it will be slow. Oil and graphite work on two completely different principles, and do not work together at all. Graphite is a surface treatment, where friction is reduced as the layers of carbon molecules in between the two surfaces slide over each...

If you bend the axle by holding it on the end where it goes into the car, then pushing on the other end I wouldn't worry if I scratched the axle, as the wheel will ride on the other side of the axle, and not touch the scratched side. (for front bent axle)

I would only buy wheels from the scout shop, with axles, for $1.99. There are places online which sell bulk wheels. But some also sell "hand picked premium wheels" and "modified wheels". So when you get the standard wheels, It is very possible they are all picked over, with all the best ones...

Zero Experience Here, just my understanding of physics, but I'm assuming: - Narrow the rear wheel on the DFW side. Lets assume that is your right wheel for this example. - DFW on right side should steer to the right (outwards) instead of to the center like normal rail riders with a center rail...

That track looks very nice! Turned out well, good job! Thanks for sharing the experience. Nice smooth polyurethane finished wood, with an aluminum center rail sounds like a very good way to do it. I may copy you.

No experience here, but you could just do a small little test piece first to see how it goes, and what grades of sandpaper you would use. The besttrack is not anodized, so you don't need anodizing, bare aluminum should be fine. I'm guessing you may have to do some sanding at the joints to get...

Same amount of force further out radially, yes. But Energy = Force * distance, and while touching further out radially, this is a longer distance the friction point moves in each revolution, hence more lost energy. Put another way, further out is a larger torque, just like having a longer...

Wow, a 2 story track! That is very interesting. The COM being in the back will not help nearly as much on this track since the increase in potential energy would now be a much, much, smaller fraction of the total energy of the car. More stability would be more important, and aerodynamics...

Yes, a tapered back end would help reduce drag. The effect is inversely proportional to the length of the body cross section, so it doesn't make a huge difference for a full 7" body length. It does not have to come to a point, even just a partial taper at a slight angle to a flat back would...

No track test, CFD simulations using validated commercial code (ANSYS CFX) to calculate body drag. Used virtual race code I wrote to calculate race times, changing only a single variable "body drag coefficient". Upwards taper does produce some lift (~10 mN) which would reduce some wheel/axle...

Yes, it definitely does matter, good question Duck. I saw increase in drag of over 50% between different nose tapers. This translates to over 4ms time difference on a 42' besttrack. e/o is correct, very nice job there! The optimal front tip location is dependent on ride height. It is slightly...

Thank you very much for running this real world test Bubblegum. That concurs very well with my prediction of 23 ms faster for the 7oz vs 5oz car. It's good to know that math and the laws of physics are still valid:)

Math states that the maximum weight would be best. (with all other variables being constant) This lowers the fraction of energy that must go into spinning the wheels. It also means aerodynamic drag would have less effect at slowing the car down. The difference between 5oz and 7oz is only 23...

I don't know what plank fenders would look like in traffic. I wouldn't use them just cuz they are ugly, and probably heavy. I'm lazy so I don't build balsa fenders, I just 3D print them, so they are more dense than balsa. I thought you guys already had simulator software available? Doesn't...

I had not realized how close these cars are together, less than an inch of space between them (3.5" pitch). With cars on both sides, (mathematically, infinite cars side by side) the total drag force increases by 14% vs. the car being all alone. Using a race calculation script I wrote, I...