What shape weights do the pros prefer out there - cylinder, small squares, Jerke's sweet spot, etc. I can see where the Steet Spot has its advantages for fine tuning but it does seem to extend the weight distribution further forward and increase the moment of inertia due to its length when compared to the round, stout 4oz cylinder. What are you guys using out there? Your thoughts.
Tungsten Weight Selection
- Thread starter Falcon777
- Start date
I have been told by many Tungsten cubes ... This is the advice from the Pro's. That is in my car now...
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I am just trying to wrap my head around the concepts and variables. The cubes forward and aft of the axle will give a relatively long moment arm and create more inertia which slows cars down. The compact size of a heavy vertical cylinder concentrates all of the weight in a very small area which has yields less inertia, in theory, more speed. However, the cylinder places a little less weight aft and forward and will need to be fared slightly since a portion will protrude out the bottom of a thin wedge with perhaps a slight aerodynamic penalty. The Sweet Spot is interesting because it can be adjusted on the fly, gives a low profile, and has the advantage of changing the COM in a finished car. So the Car can be tested to see what com gives the best speed while reducing inertia with its small size. So it is really a balancing act between inertia, com, weight placement, aerodynamics, etc. It is said that COM should very with track conditions - more weight up front with bumpier tracks. Since all major races are using Best Tracks, it is fair to assume all Best Tracks are smooth and clean at professional races and therefore, running a com of 1/2 inch forward of the rear axle is ideal?
People tend to say that any less than 1/2 inch causes the car to wiggle. The problem with cylinders is that they are round and thick. The cubes give you greater flexibility in where and how they are placed. A big reason for tungsten is so that you can get that 1/2 inch COM with an extended wheel base.
The sweet spot might be the worst form I have used along with the big rounds. You need the weight all the way to the back of the body.
The worry about the car moment of inertia is a total waste of time.
IC - THE MOMENT OF INERTIA OF THE CAR
This value is only used if the car is running on an inclined plane ramp
where the ramp makes a definite and abrupt angle where it meets the
horizontal run part of the track.
On all Best tracks, this is not the case- same as typical wood track
Now, if it were a track with a very sharp transition- what are we looking at?
Track Car
best42track SS jb07 2.9508
Fake Track SS jb07 with lead 2.9531
Fake Track SS jb07 with tungsten cubes 2.9516
Fake Track SS jb07 with tungsten lump 2.9512 IF you could keep car 5/16 thin which you can not
When you add a bit more area to cover the lump, you drop any gain.
IC - THE MOMENT OF INERTIA OF THE CAR
This value is only used if the car is running on an inclined plane ramp
where the ramp makes a definite and abrupt angle where it meets the
horizontal run part of the track.
On all Best tracks, this is not the case- same as typical wood track
Now, if it were a track with a very sharp transition- what are we looking at?
Track Car
best42track SS jb07 2.9508
Fake Track SS jb07 with lead 2.9531
Fake Track SS jb07 with tungsten cubes 2.9516
Fake Track SS jb07 with tungsten lump 2.9512 IF you could keep car 5/16 thin which you can not
When you add a bit more area to cover the lump, you drop any gain.
I think we might be mixing two ideas at once. We have COM, and we have the car moment of inertia.
I am saying you could put a bit of gold on the very back of the car, and then a bit of lead way up near the nose, and mess around until you got the COM that was best for no wiggles, high speed, [ let's just say 5/8" in front of back axle] and the high moment of inertia because the weights are spread out is of no consequence compared to using a cylinder of equal mass to get the same COM, but a super low moment of inertia. I am also suggesting that the air friction loss buy needing a thicker car for a perfect sphere or cylinder of weight would then make a slower car.
Now in getting a com of 5/8", most cars are going to be hollowed out and then cubes put in all surrounding the back axle, and any way you want to do it to get the com you like is just fine. You might read where some racers start with a certain COM, and then move a small bit of weight around to fine tune the car. Many will improve the car speed with such adjustments. Do they care that they moved the COM up to 7/8"?, or that they have now increased the car moment of inertia?
Not if the car runs faster.
I am saying you could put a bit of gold on the very back of the car, and then a bit of lead way up near the nose, and mess around until you got the COM that was best for no wiggles, high speed, [ let's just say 5/8" in front of back axle] and the high moment of inertia because the weights are spread out is of no consequence compared to using a cylinder of equal mass to get the same COM, but a super low moment of inertia. I am also suggesting that the air friction loss buy needing a thicker car for a perfect sphere or cylinder of weight would then make a slower car.
Now in getting a com of 5/8", most cars are going to be hollowed out and then cubes put in all surrounding the back axle, and any way you want to do it to get the com you like is just fine. You might read where some racers start with a certain COM, and then move a small bit of weight around to fine tune the car. Many will improve the car speed with such adjustments. Do they care that they moved the COM up to 7/8"?, or that they have now increased the car moment of inertia?
Not if the car runs faster.
