Derby Talk is a forum for Pinewood Derby, Awana Grand Prix, Kub Kar Rally, Shape N Race Derby, Space Derby, Raingutter Regatta and other similar races where a child and an adult work together to create a race vehicle and a lot of fun and memories
resullivan wrote:I have a question about a RR. Our rules state: "All four wheels must be intended to ride flat, not angled or altered, on the track." I take this to mean no camber. My car is a 3 wheeled car. My question is should I bring in the DW like is done with a RR? I don't think I can bend the axels based on this rule, but by chance or luck may be able to get some of the effect of a RR. I know without the camber the car will not stay on the rail. It is the DW and you bring it in 1/16th correct?
I disagree with any rule which imposes on the inspector the necessity to gage "intent." But aside from that...
RR does NOT require camber! Those are two totally separate performance concepts which, happily, work well together.
RR works with just DFW toe-in. Adjustment by bending the axle more or less by hand or by twisting a slightly bent axle are fine. The required angle for optimum toe-in is much smaller than many assume ... 2 inches of drift on a 4' test board (41" travel) of a car with stock wheelbase needs only about 0.6 degrees of toe-in! That 2" of drift inflates to 9-1/2" on an 8' board! (Computations per http://www.stanpope.net/driftcomp.htm" target="_blank)
I suspect that a wheel on an axle with 0.6 degrees of camber would lie flat on the inspection table, (although it might lift just a bit once it gets rolling.)
Stan
"If it's not for the boys, it's for the birds!"
So in addition to the DFW having toe-in, it should also be 1/16th inside the wheel behind it? So the DFW will ride on the rail while the back two do not?
resullivan wrote:So in addition to the DFW having toe-in, it should also be 1/16th inside the wheel behind it? So the DFW will ride on the rail while the back two do not?
Right!!!
Stan
"If it's not for the boys, it's for the birds!"
Finished hiding the weights and put the first coat of paint on. Might be in trouble on total weight. Without paint it is at 4.97. Not sure what I am going to do.
resullivan wrote:Finished hiding the weights and put the first coat of paint on. Might be in trouble on total weight. Without paint it is at 4.97. Not sure what I am going to do.
Presume that the 4.97 includes the wheels and axles!
The rails seem kinda thick so you have a few hundredths available there!
Could also trim the tips off the nails, too.
FYI, I tell my pups to aim for a "finished weight" about 4.8 and the glue on a small "trim weight" where it makes the car fastest. It allows a small amount of CM adjustment at the last minute. But that advice appears to be a bit late!
Stan
"If it's not for the boys, it's for the birds!"
We did not even put primer on it. We did paint the bottom, but with only one coat. The second coat was only on the top side. The paint was a really good spray paint from hobby lobby. As much as we would have liked to really make it shine, I can't say I am dissapointed with a .02 - .03 ounce paint job considering we are more worried about speed than looks.
I did think about adding a quick spray of the clear to finish out the last .01, but I am just concerned it would make it overweight as my scale only goes to .01, and I think our pack and district scales go to .001.
In most cases if you are over weight you drill some holes into the wood. But with your car there does not look to be anyplace where you could drill a hole. I guess between the front wheels there might be some wood. The hole does not usually go all the way through and is done from the bottom.
We shoot for being a little underweight and then use some lead putty to get the weight to where we need it. I believe the lead putty is now available as tungsten putty but I don't really think there is any tungsten in it. Maybe tungsten powder? I don't like the the new stuff as much as it is more tacky than the old lead putty. But it is probably safer.
If you want, you can argue significant digits. 5 oz is techincally 5.4 oz or less. 5.0 oz is 5.04 oz or less. So see what the rules say and go from there. Their scale can go to .0000001 oz but if the rules state 5.0 you are good to 5.0499999. Our rules state 5.000 oz. So we have no wiggle room.
