R help - Oct 2009 - anova interaction contrasts: crossing helmert and linear contrasts

I am new to statistics, R, and this list, so apologies in advance for
the errors etiquette I am certain to make (in spite of reading the
posting guide, help on
various commands, etc.). ?Any help is greatly appreciated.

Here is my data:

fatigue =
c(3,2,2,3,2,3,4,3,2,4,5,3,3,2,4,5,4,5,5,6,4,6,9,8,4,3,5,5,6,6,6,7,9,10,12,9)
n <- 3
train <- gl(3, 4*n, labels=c("6wks", "4wks",
"2wks"))
dist <-
rep(gl(4,n,labels=c("1mi","2mi","3mi","4mi")),3)

What I would like to do is test two interaction contrasts that cross linear
coefficients of the variable "dist" with the two sets of helmert
contrasts of
the variable "train".

I have tried so many things I think are wrong I won't reproduce them all
here.
Here is a representative example:

My code:


contrasts(dist) = c(-3, -1, 1, 3)
contrasts(train) = contr.helmert(3)
aov1 = aov(fatigue~dist*train)
summary(aov1, intercept = T, split=list(train=1:2), expand.split = T)


My output:

? ? ? ? ? ? ? Df Sum Sq Mean Sq ?F value ? ?Pr(>F)
(Intercept) ? ? ? 1 890.03 ?890.03 801.0250 < 2.2e-16 ***
dist ? ? ? ? ? ? ?3 ?85.19 ? 28.40 ?25.5583 1.199e-07 ***
train ? ? ? ? ? ? 2 ?88.39 ? 44.19 ?39.7750 2.403e-08 ***
?train: C1 ? ? ? 1 ?18.38 ? 18.38 ?16.5375 0.0004452 ***
?train: C2 ? ? ? 1 ?70.01 ? 70.01 ?63.0125 3.621e-08 ***
dist:train ? ? ? ?6 ?18.72 ? ?3.12 ? 2.8083 0.0325092 *
?dist:train: C1 ?3 ? 3.46 ? ?1.15 ? 1.0375 0.3938042
?dist:train: C2 ?3 ?15.26 ? ?5.09 ? 4.5792 0.0113201 *
Residuals ? ? ? ?24 ?26.67 ? ?1.11
---
Signif. codes: ?0 ?***? 0.001 ?**? 0.01 ?*? 0.05 ?.? 0.1 ? ? 1

Among the reasons this seems wrong to me is that I want 1 df
interaction contrasts. "dist:train: C1" and "dist:train: C2"
seem (to
my naive eye) to be testing respectively whether my first and second
helmert contrast of train differ significantly across levels of dist.
I want to test the significance of two contrasts of linear trend over
dist--the slope of linear trend at 6wks and  4wks against each other,
and the average of the slopes at 6wks and 4wks against the slope at
2wks.  I don't know how to do this.

Thanks for any help you can offer.