Need help for PWD Ultimate race

[speed]

Rules: BSA block, any wheels as long as plastic/delrin, axles must be metal. No bearings. Car can weight up to 12oz.

What I am thinking:

I am planning on using about 7ozs with derbyworx s and needle axles. What do people think?

What I am not sure about is canting. Is there any benefit in canting when using s?

I was planning on RR. Thoughts? This is the first time we have had such a race and I am completely inexperienced.

Is 7ozs on needle axles better than 7ozs using s but regular axles?

Thanks for any help in advance.

[Go Bubba Go]

Assuming the cars have to be "gravity powered only" (worth checking to be certain for an "Ultimate" race), I have two opinions floating through my head, both involving DerbyWorx RSN wheels (raz or wheels, needle axles).

1) A 3 wheel rail rider, 7 oz., weight largely concentrated in the rear.

2) A 4 wheel rail rider, 12 oz., similar to the above but with the remaining 5 oz. located near the front.

My built-in assumption is that I don't want to put more than about 6 oz. or so on one pair of wheels and axles.

The advantages of the first build are that you don't have to "spin up" the 4th wheel and there is very little weight on the single front wheel touching the rail, therefore reduced friction loss against the rail. However, the second build would have an extra 5 oz. on board to get that 4th wheel going and build some momentum to help overcome deficiencies in alignment, etc.

For a more experienced builder, my suggestion would be to go for option 1). You can put together a sleeker looking build with minimal material up front, and there is some extra fun in a watching a lighter weight car best any "heavyweights".

For a genuine newby who might end up with both front wheels touching the rail at differing points along the way, the "brute force" option 2) might be more appropriate.

Either way, forget the cant with the RSNs. They have a nice bevel built into them to minimize the surface riding against the rail and the tread surface is very thin.

And don't forget to narrow the front end slightly either way to help keep the rear wheels off the rail.

Bubba

p.s. Here's a pic of a 7 oz. 3 wheel build I did for a recent "Adult" race. In that case we had to use BSA wheels (we could modify to our hearts content) and full size axles.

[JustaDad]

Bubba, I sent you a PM

[speed]

Thanks Bubba.

The reason I was considering canting is to keep the wheel from the side of the car. I would think this is still an issue with s and needle axles.

It would seem like a slight cant would be beneficial for this. Thoughts?

[khouse]

Any time you can keep the wheel from rubbing the body is a good thing. Just make sure you cone the inside wheel hub and rub some graphite on the body just in case.

[Go Bubba Go]

Feb 26, 2009 16:22:59 GMT -6 speed said:

Thanks Bubba.

The reason I was considering canting is to keep the wheel from the side of the car. I would think this is still an issue with s and needle axles.

It would seem like a slight cant would be beneficial for this. Thoughts?

If you're gonna run homemade big axle wheels then cant the rear wheels (and cone the hubs for insurance ).

If you're gonna go with the RSNs, run them straight i.e. no cant. Make sure the body is nice and smooth (we sand up to 2500 grit whether we painted / coated the area or not) and rub some graphite in hard, but IIRC the inside of the wheels is nicely rounded already.

Bubba

[Mr. Slick]

For what it is worth, Weight is not everything.

"Old Woody" lost to a 16 ounce car with big axles by .02 seconds on the long track. Old Woody weighs 3 oz. and runs with the RSN wheels/axles. The heavy car didn't lose as much speed on the run out. Old Woody was way ahead at the bottom of the slope and would have won if it was a 42 ft track.

[derbydominator]

An additional tip if it is within your rules and you decide not to cant the axles is to use a thin strip of tape over the axle hole and then just punch your axle through. We use a High molecular weight polyethylene very low friction tape which takes graphite really well. Most PD races would consider it illegal but should be ok for open races. I get it from a local R S Hughes store, but here is a website that sells it.

www.leevalley.com/wood/page.aspx?c=2&cat=1,110,43466,32182&p=32182

You are better off with canted wheels and a rail rider set up, but this can help if you choose not to go that route.

Darryl
www.DerbyDominator.com

[roosclan]

Bubba, I just sent you a PM. I gots questions!