Cant and Toe

Secrets, tips, tools, design considerations, materials, the "science" behind it all, and other topics related to building the cars and semi-trucks.
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Curse You Red Baron!
Master Pine Head
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Cant and Toe

Post by Curse You Red Baron! »

I am wondering about alignment vis-a-vis tuning and what it means for cant and toe on a typical rail rider.

To start with, most people cant the back wheels about 2.5 degrees. This means you will always have a trade-off between cant and toe, because for 1/3 to 1/2 of the race your car is on a slope, and for the remainder of the race it is roughly level, on the 'flat'. Therefore if your alignment is perfect on the flat with nuetral toe, the nose will be (let me visualize...) pointed down and therefore the rear wheels slightly toed-in while on the slope. I think the logical outcome of thinking through the variations leaves you with three options:
1) Toe in on slope, nuetral on flat
2) Nuetral on slope, toe out on flat
3) Somewhere in between.. so you have what I'll call a "slight" toe-in on the slope and "slight" toe out on the flat.

I am not sure which conditions might outweigh the others. I would also suspect that the impact of alignment 1, 2 or 3 will vary based on the track slope, transition speed, track length, relative length of slope to flat, track integrity (how smooth it is), your axles, your wheels, not in that particular order and not comprehensive... all variables that for myself and 99.9...% of humanity would be too complex to model, hence the need for tuning on a track to find your sweet spot. I would think #1 would hold it's speed best (good for long flats?). For #2, maximizing the fast start and ultimately the speed of the car at the transition seems like a good thing for most of our relatively short (32') tracks. However, minimizing errors and track imperfections might lead to option 3).

I think Sporty first published the idea of running the car down the slope with only back wheels attached and something slick on the nose with the objective of a running a straight line. Because of the slant of the test slope and the slant of the car on the slope, I suspect this may do a fair job of creating a car that satisfies alignment #2 above for most tracks, before tuning. I haven't even started thinking about the front wheel(s) yet, but does this thought process seem useful? I've seen comments that suggest a strategy behind when a car should have some toe... and what type of toe... and clearly that can be built into the car design, esp. when you talk about where you drill the axle holes front vs back, and also the cant for each - all have the potential to depress or elevate the nose of the car and hence create or moderate Toe. Appreciate folks input, thanks!
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SirStorm
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Re: Cant and Toe

Post by SirStorm »

I'm not sure why the toe would change on the slope vs the flat. The same surface of the wheel is touching the track, and the alignment has not changed.

Your concern is not an issue as far as a "changing toe" goes.

Canting the axle does not introduce toe. It does encourage the wheel to ride on the inner edge and the bore to run against the nailhead. This is generally better than running against the paint or wood of the body.
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Curse You Red Baron!
Master Pine Head
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Joined: Sat Oct 10, 2009 8:35 pm
Location: Superior, Colorado

Re: Cant and Toe

Post by Curse You Red Baron! »

Ah, yes, oops :oops: - I failed to keep my frame of reference. Regardless of slope, the wheel will move to the head and the weight of the car will push the wheel against the track in the proper 'attitude' so that the line between the axle head and the point of the wheel touching the track will always be (virtually) perpendicular to the track, regardless of orientation. I was picturing it from directly overhead relative to the flat, but the proper reference is the track itself. Thanks for the help!
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