My sons are building ladder style cars with balsa bottoms, monokote wrap and carbon sticker tops. This year to try something new they are using Puma weights. It seems it would be possible to get the COM as low -- or even lower -- than 0.5 inches, which begs the question whether that is advisable?
Their cars are standard axle distances, but they did cut some off the back and glue to the front to get the rear wheels as close to the back as possible. They have 10 tungsten cubes behind the axle and need to place 3 more to hit 5 oz, per the picture. They could put those weights just about anywhere, including asymmetrically to one side.
With the weights just in front of the rear axle, the COM is less than the radius of the Puma weights, or less than 0.5 inches, and the weight on the DFW is 0.452 oz.
If they put the 3 cubes in the pocket in front of the axles but more forward in that pocket, as shown in the picture, the weight on the DFW increases to 0.451 oz.
If they put the 3 cubes in the next forward pocket (just visible under the carbon sticker) the weight on the DFW would increase to 0.563 oz.
They do NOT have access to a track to tune. The first run down one will be their first heat. Their pack uses an aluminum track. The question is what COM to go for? Note that the rear axles have been drilled at 2.5 degrees and so they will use straight rear axles. Post drilling they moved away from the body on both forward and rear rolls, though they've yet to install the actual axles and wheels for additional testing. But that testing will be done on a flat surface or homemade ramp, not an actual track.
They've historically done fairly well -- e.g., winning their ranks and placing in the pack -- but thy've never done better than 2nd, so there is some incentive to consider a more aggressive COM in search of faster times, but perhaps that is inadvisable?
Any counsel on COM would be greatly appreciated!
Their cars are standard axle distances, but they did cut some off the back and glue to the front to get the rear wheels as close to the back as possible. They have 10 tungsten cubes behind the axle and need to place 3 more to hit 5 oz, per the picture. They could put those weights just about anywhere, including asymmetrically to one side.
With the weights just in front of the rear axle, the COM is less than the radius of the Puma weights, or less than 0.5 inches, and the weight on the DFW is 0.452 oz.
If they put the 3 cubes in the pocket in front of the axles but more forward in that pocket, as shown in the picture, the weight on the DFW increases to 0.451 oz.
If they put the 3 cubes in the next forward pocket (just visible under the carbon sticker) the weight on the DFW would increase to 0.563 oz.
They do NOT have access to a track to tune. The first run down one will be their first heat. Their pack uses an aluminum track. The question is what COM to go for? Note that the rear axles have been drilled at 2.5 degrees and so they will use straight rear axles. Post drilling they moved away from the body on both forward and rear rolls, though they've yet to install the actual axles and wheels for additional testing. But that testing will be done on a flat surface or homemade ramp, not an actual track.
They've historically done fairly well -- e.g., winning their ranks and placing in the pack -- but thy've never done better than 2nd, so there is some incentive to consider a more aggressive COM in search of faster times, but perhaps that is inadvisable?
Any counsel on COM would be greatly appreciated!
