Wheel gap on RR

[beachnut]

Since this is our first time building a RR I thought I'd ask if others here are running a larger wheel gap with this setup. I've been using the Pro-Axle Guide in the past to insert axles and set the gap. The gap on that tool is reported to be .035, but when I look at the Derby Worx RR video it seems like the gap on their car is almost twice what I've been using.

[batstar70]

beachnut, I've been using the thickness of an old ATM card, with a U-shaped notch cut into it for the axle. batstar70

[DKO]

We used the pro axle tool with a railrider this year (our first one) and were very successful at the pack level (1st). We haven't had our district races yet. I did notice the same thing on the video though. Alignment seems to be a more important factor in my opinion.
Good luck!

[4my4boys]

This year we converted our pack car with all 4 wheels touching (pack rules) over to a 3 wheeling, rail rider for the district race. We used the pro body tool to redrill the axel holes. We didn't want to do any repainting, so instead of narrowing the front on the DFW side, we went with a larger gap for the rear wheel on the DFW side. We just used that $5 dollar plastic multi-tool (at the scout shop) for spacing the DFW and then used the thicker part of the same tool for the rear wheel spacing. On our testing board we were able to keep the rear wheel away from the rail on every pass. The morning of the district race we converted the DFW from a positive cant (the way the directions tell you) to a negative cant which increases the clearance for the rear wheel even more.
All that being said, we went from being the 3rd fastest car in our pack race to the 1st place wolf and 7th fastest car overall at our county (2 districts combined) race, and we blew away the first place car from our pack. We plan to do much better next year at the county race as our pack rules are way more strict than the districts. We will take better advantage of modifications.
Good Luck!

[Stan Pope]

... we went from being the 3rd fastest car in our pack race to the 1st place wolf and 7th fastest car overall at our county (2 districts combined) race, and we blew away the first place car from our pack. We plan to do much better next year at the county race as our pack rules are way more strict than the districts. !

Ooooooh! Nice. And, aren't you glad you don't have to live with rules that require that the cars be impounded between pack and district races?

[quadad]

The morning of the district race we converted the DFW from a positive cant (the way the directions tell you) to a negative cant which increases the clearance for the rear wheel even more.

My remembrance was that the directions suggest a negative cant all around - is that not true ? In our initial RR testing on a wooden home-built track with fairly smooth center guides, there was a very strong benefit to positive cant on the DFW which was steering into the rail (about 0.025 over 32'). I continue to see however opinions on both sides of this and am trying to understand what 'drives' (couldn't resist) people to one opinion or the other.

[davem]

Here's my experience.
Canting the DFW resulted in more rear end instaility.

I actually lost .01 to .02 with the DFW canted.

[beachnut]

Here's my experience.
Canting the DFW resulted in more rear end instaility.

I actually lost .01 to .02 with the DFW canted.

Canting at all, or canting positive vs. negative?

[sdupont1]

Here's my experience.
Canting the DFW resulted in more rear end instaility.

I actually lost .01 to .02 with the DFW canted.

You did something wrong.
Negative cant the rear but positive cant the DFW. Also canting the wheels will make it MORE stable with a aggressive COM.

[davem]

Negative cant on both rears in all tests.

Positive cant on DFW = .01 to .02 slower than no cant on DFW.