Derby Talk

I believe I read somewhere that powdered Tungsten is dangerous/hazardous somehow. Please be careful. Don't assume Tungsten powder is safer.

Kids should all have a equal and fair chance at PWD. I'm curious, how far do you think you should take something like that? How do you decide where to draw the line? Should all the blocks be pre-shaped, and pre-weighted, and perfectly aligned? Then the kids could paint them any color they want, and...

Next step is to compute the differences and find the transfer point. But that would not be possible, unless you knew how many bumps the car will hit on any particular run down the track. I suppose you could come up with a statistical average, possibly based on empirical (measured) data. I think you...

The problem lies not so much in my ability to digging out the appropriate equations But in the application of these equations to the physics of PWD cars. The KE lost during the rotation would be = 1/2mr2w2. The 1/2 and m (5oz) are fixed. The w (angular velocity) would be the speed of rotation, and w...

if your dad works for NASA

Thanks! (not offended, just kidding around)
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One of my own pet peeves.
I strongly feel that the rules whatever they may be, are ones that can be enforced.
They should be distributed before, or at the same time as the kits.
And finally they should be enforced on race day.
Anything else just isn't fair.

if your dad works for Nassa Did you mean NASA (National Aeronautics and Space Adminsitration)? My dad (retired) and father-in-law (still going) worked for NASA. Real rocket scientists, both of them. Helping their grandkids to win Derbies. Sorry, a little touchy about that down here on the space coa...

I still feel like I have no answer to one of my original questions. We've established that it is possible to get the COM below the axles. Stan has stated that this increases the PE slightly, which I agree with. The bottom back corner of the car will drop the furthest distance. One of my original con...

While sorting through my nails the other night, I noticed some had 2 stripes, and some 3. I found that odd.
Nothing like you described tho.
(I don't bother to remove them, just orient them so they are up, the wheels touch the bottom of the nail, on the other side.)

Thanks. Wow. COM 1/8" below the axle plane. I think I drill the axles 1/8" above the bottom of the block to give 1/8" all around the axle holes (and maintain 3/8" required clearance). You must have got your COM right on the bottom of the car. Thin plate maybe? Screwed to the bott...

There have been so many posts on this, I thought I had the physics understood, but a recent post by Stan seemed to contradict what I thought I knew. I understand that there are lots of forces acting on a PWD car as it rolls down the track, and it is hard to change one thing without affecting somethi...

Not to argue too much, but you missed my whole point. I think I understand the concept. I can see how talking about front/back of the car with a reference to the car on a level surface will make it easier for everyone to understand, sorry I deviated from that, and caused confusion. In my original po...

Ahh, the complicated Trigonometry I was referring to. Notice in the diagram, the low CM is much closer to the back of the car, as it sits on the incline (not necessarily the back when level). Assuming the CM was the same distance front to back (as the car sits on the incline), the change in height w...

Looks promising, but I only need about 4 oz now. I've still got about 5 lbs of birdshot left. (I've given lots away, and took my older son from Tigers to Webelos, and did 6 years of Indian Guides Chule Car races) I don't know what I'd do with 22 lbs of Tungsten powder. We've already raced this year,...

Recheck this assertion ... Correct, the change in height is where the Potential Energy comes from. On a standard track, the back of the car starts higher than the front, and finishes level. Therefore, the back of the car changes height more than the front. Therefore more weight in the back will cre...