lightest DFW weight possible?

[txchemist]

Another area of consideration when we look at how light can the front wheel get, is that the friction between the wheel and the rail, the friction between the wheel and wood or Delrin or whatever, is NOT a constant, and it does NOT go the way you might think. The lighter the force between the polystyrene and the object, the higher the friction. There is a zone where increased steer drops friction but then is reversed when more of the wheel rubs over a longer path on the rail so it is not just "stability" changing with steer. Some builders find increased angle of bend on DFW gives higher speed. That can be due to more pressure (weight) against the body which reduces friction depending on how you treat the side of your car. So moving a tuning weight around on your car can be doing a number of interesting things that will not be the same on every car. Many have tested Delrin and said- no good, others are very happy with it. Here is a look at 13 different Delrins. The two best ones match graphite, and some are way worse than monokote.

 

[3phase]

Is that why dog poo is so slippery when you unknowingly step on it at full force?

 

[txchemist]

YES! after a few falls, you learn to.....
http://youtu.be/zcSlcNfThUA

 

[B_Regal Racing]

From what I found-
1. boron, aluminium and magnesium (BAM) .02
2. PTFE .05
3. UHMW.12
4. Delrin .2

Is there a way to test the friction coefficient of a product at home without a ridiculaously over-priced specialized tool? Right now, I am trying different substances as friction plates and recording the times to see which is best. I looked at the chart above and disagree with it (with the exception BAM, as it is not available for use in a simple derby car). Or is this type of testing (e.g. installing different friction plates on the same car without changing weighting or steer) skewed based on the weight on the FDW?

 

[txchemist]

It is not found often in the published data, but the polystyrene wheel has a big change in friction with weight. Normally, friction does not change, but with BSA wheels, heavier is LOWER friction. Many others have mentioned low cost ways to measure friction. I am deep into looking at the friction plate and also wheel against aluminum and use a cheap mirror from Lowes. It is 20x 24 but you need to measure what one you get. All you do is put down a strip of what you are testing, wood, Al tape, Teflon Tuff, Monokote, UHMW, Teflon Tape, Nylon, Delrin etc. Use BSA wheels and let them sit on each strip. Slowly lift the edge and the first wheel to move is the lowest friction. Repeat a few times to confirm. Now to actually get an estimate- freeze your mirror when the wheel starts to slide, and measure the height of that edge- then figure out the Tan of the angle, and that is the COF. Then polish the edge and start looking at wax, and then start to add wax or sprays to the strips and work on a process.

By heavier- I mean increased pressure at contact between plastic and body, or plastic and axle- so a grooved axle has increased pressure on a smaller bearing surface, and lower friction.
This measures the static friction- but will screen to just a few good ones to try. Once you start adding a spray or oil to a surface, they all will improve dramatically.