Drilling Angled Holes in the Original Slots?

[exoray]

Over the years I have noticed that weight placement and the resulting center of gravity is the primary reason for most of the wobbly cars... The ones that wobble the most are almost all back-heavy with the center of gravity over or behind the rear axle instead of in front...

[FatSebastian]

The ones that wobble the most are almost all back-heavy with the center of gravity over or behind the rear axle instead of in front...

Tail-heavy (aft-weighted), yes. But CoM behind the rear axle... wouldn't that wheelie?

[exoray]

Tail-heavy (aft-weighted), yes. But CoM behind the rear axle... wouldn't that wheelie?

Yeah, that happens as well once you get rearward of the axle, especially on the flat stretch, and if they jump track or not due to wheeling that seems to depend on bottom clearance that sometimes can create a built-in wheelie bar that limits the wheelie, especially on center rail tracks where the car bottom clearance is smaller... Either way too much weight in the back is bad...

[philm63]

I do shoot for a CoG at 3/4" to 7/8" in front of the rear axle and our two cars this year really did not have discernable wobble like many of the competing cars. But they are still a little slower and upon observing how my boys' cars ran against the competition, it was evident the biggest offender was friction on the flat and, compared to at least two other cars, ours wasn't the fastest to the bottom of the incline so that is another area I plan to focus on for next year's builds. (extended wheelbase and more aggressive CoG, perhaps?)

[Loud2ns]

Oh, and we did our weigh-in tonight - race is tomorrow morning -

How did your kid turn out at his race?

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[philm63]

I had both of my boys in the race - each took 2nd in their respective dens, and placed 7th and 8th overall in the finals.

The 1st place finisher clocked a 3.5668 and my boys clocked 3.6801 and 3.6852. All in all their cars were pretty much dead even with each other, and the competition was pretty tight with only a little more than 0.11 seconds separating my boys from the big trophy!

Worthy of note - we really didn't go hog-wild this year with our builds - basic wedge with a lower profile from the previous year, and I did a little prep work on the hubs and tread surfaces of the wheels, and polished the axles a little bit. Honestly, I think I either took too much material off or started with a not-so-good set of wheels on their cars - when assembly was done, the wheels seems to wobble on the axles quite a bit when manipulated by hand as if there was too much play. The cars tracked well and did not fishtail, but I also was not rail-riding nor did the cars have a cant to any of the wheels - and all 4 were on the track.

I think I can find that missing 0.11+ seconds (and then some!) for next year's race by lifting a wheel, canting the rears, and steering into the rail, no?

[FatSebastian]

...ours wasn't the fastest to the bottom of the incline...

I think I can find that missing 0.11+ seconds (and then some!) for next year's race by lifting a wheel, canting the rears, and steering into the rail, no?

And simply lifting one of the front wheels from touching the track will probably give the most speed increase at the bottom of the incline for the least amount of effort.