My Son Defended His District Championship!!!

[PWD_addict]

Sorry I haven't posted much this year. Ever since taking on Cubmaster, and starting a new business, I have less time than ever. I hope I haven't missed much new developments in PWD world!

Anyway, my son defended his District Derby Championship this year (Webelos I). Being a Webelos, he did almost the entire car by himself. I was particularly proud.

At our Pack races in January, he took first place by 0.0026 secs (avg time with slowest of 8 races dropped). We figured Districts would be very tight as they usually are so we decided on a last minute adjustment (I usually hate them but it worked this year). We figured that #2 in Pack would make some changes before Districts so we had to try something. We decided to adjust amount of drift from 4.5 to about 3 inches. It seemed to make a big difference. We also didn't break-in the graphite too much knowing that he only had to qualify in the Top 3 in rank (8 races total) to make it into the Grand Finals for Districts. He ended up winning the District Webelos I rank with an avg time of 4.1156s. The top Bear ran 4.1174s avg so we expected the Grand Finals to be close.

They ended up not being too close because the graphite had broken in for my son's car and his car was much faster than it had been earlier in the day. In one of his races, he broke the track record by 0.0001s that had stood for a couple of years (his cousin) and on his last run, soundly broke it by 0.0158s (4.0516s). His average in the Grand Finals was 4.0974s. That's a pretty significant improvement from rank to Grand Finals that I can only attribute to graphite break-in.

One of the Wolves at the District race from another Pack (he's a great kid) was excited that my son was crossing over this year. When I told him he had one more year to race, he was bummed. Then, I told him that his younger brother will be a Tiger the year that he crosses over, he was even more bummed. But, he did better than anyone else in his Pack and came in 5th overall so he and his Dad were pleased with that. I had given my tutorial at one of his Pack meetings and their Cubmaster said that everyone's cars were much faster this year. Yet another victory!!!

[FatSebastian]

Neat story!

We decided to adjust amount of drift from 4.5 to about 3 inches.

Over what run distance?

[PWD_addict]

Neat story!

We decided to adjust amount of drift from 4.5 to about 3 inches.

Over what run distance?

Sorry. I should have stated that. It was over 45 feet.




JUST KIDDING! It was 3 inches in 4 feet.

Fairly rough, aged Challenger track with homemade frame.

[FatSebastian]

JUST KIDDING! It was 3 inches in 4 feet. Fairly rough, aged Challenger track with homemade frame.

Thanks - obviously the steer was strong initially because of Pack track conditions (likely because you were running a fairly aggressive CoM). As point of reference, may we also ask the locations of the CoM and axles?

And congratulations on securing the District title again. Defending a title can be a lot of pressure on a Webelos (whether he admits it or not).

[PWD_addict]

JUST KIDDING! It was 3 inches in 4 feet. Fairly rough, aged Challenger track with homemade frame.

Thanks - obviously the steer was strong initially because of Pack track conditions (likely because you were running a fairly aggressive CoM). As point of reference, may we also ask the locations of the CoM and axles?

And congratulations on securing the District title again. Defending a title can be a lot of pressure on a Webelos (whether he admits it or not).

He was cool as a cucumber. My heart was pounding the first Grand Finals race. I was trying not to pay attention to the races (I am the District Chair) but when they called out the order of finish, and my son wasn't in the Top Three, my heart skipped a beat. But then I remembered that there are 15 racers in the Grand Finals and only 8 lanes so he hadn't raced the first heat!

Axle location was drilled holes, extended as far apart as possible with the fronts about 3/16" from the car front to protect from the stop section. Three wheel RR with COM about 1 1/8" from rear axles. The larger COM a result of the need to maintain 4:1 rear:front weight ratio on our rough track. We learned that 2 years ago when daughter's car and nephew's car were faster than my son's car. Primary difference was that the first two had 4:1 (or less aggressive f:r ratio) and son's was about 4.6:0.4. So, for us, weight ratio (more front weight) seems to be more important than more aggressive rail drift. Although #2 in Pack races seemed to have a very light front (Max V's Predator kit with extended wheelbase: http://www.maximum-velocity.com/predatorkit.htm) and was only 0.0026s behind.

[FatSebastian]

Three wheel RR with COM about 1 1/8" from rear axles. The larger COM a result of the need to maintain 4:1 rear:front weight ratio on our rough track. We learned that 2 years ago when daughter's car and nephew's car were faster than my son's car. Primary difference was that the first two had 4:1 (or less aggressive f:r ratio) and son's was about 4.6:0.4. So, for us, weight ratio (more front weight) seems to be more important than more aggressive rail drift.

Thanks for these details, PWD_addict. By my estimate, a 4.6:0.4 ratio puts the CoM within less than 1/2" of the rear-axle line on an extended wheelbase! IIRC, what you say seems perfectly consistent with experiences / advice recorded elsewhere on DT... that control of such an aggressive CoM placement often requires such strong steer-in that a point of diminishing return is crossed (except for possibly a nearly flawless track?). So your observations add another insightful comparison point for helping to define "overly aggressive".

With a 4:1 ratio, I wonder if you could have gotten away with even less steer-in on the district track (say, ~2" in 4 feet)? Did you have a test track available before the race to determine that 3" was better than 4.5", or were you just "rolling the dice"?

[PWD_addict]

With a 4:1 ratio, I wonder if you could have gotten away with even less steer-in on the district track (say, ~2" in 4 feet)? Did you have a test track available before the race to determine that 3" was better than 4.5", or were you just "rolling the dice"?

No test track available. It was a (lucky) roll of the dice. I know that last year's second place District car was about 1.5" in 4' while son's was 4" in 4' and they were extremely close. Seems like the 3" in 4' may be the sweet spot for this track.