Post by vaderracer on Jan 31, 2016 19:05:41 GMT -6
We had a lot of fun building our first derby car this year! My son is a Bear in his first year of Cub Scouts.
I think we did ok because our car was a contender. Our pack champion's average "speed" was a converted 191 mph. Our car ran faster than that at least once but ran inconsistent speeds on the different tracks and suffered from too much "wobble".
I think we did well on aerodynamics. Weight-wise, the CM or COG is aggressive at .75 inches (actually 13/16") in front of the rear axle. (see red mark on the profile photo) This probably contributed to the wobble problem. The car weighed exactly 5 oz with six 1/2 oz tungsten weights in the rear and a little bit of tungsten puddy added at the end. I think I cantered the wheels too aggressively and unevenly. It tracked well on my little test track at home but the higher speeds on the "real" track induced a lot of wobble. This was supposed to be a rail rider LOL.
Video: Our car is 2nd from the left in lane "B" - The wobble cost us much faster speeds. Vader Racer in slo-mo
All comments and criticism is welcome. I am a noob! I have a great book: Pinewood Derby Speed Secrets which helped me with other things. But...it didn't encourage the axle canting.
For next year I was thinking of:
1. Lowering the car to exactly 3/8" clearance (about 1/16" lower) This will still be within our local rules.
2. I'm thinking about moving the wheelbase rearward. Our rules require standard wheelbase but doesn't say you can't move the wheelbase rearward. Thoughts? I'm thinking of a dozen other things too and I guess that's what makes this fun!
Thanks for this forum!