Helix

She who must be obeyed has decreed that the layout extension "must be
high enough that I can easily duck underneath it".
This is a not unreasonable request, when you consider that quite often
it is I who have to duck under the layout for various purposes
unconnected with the railway.
There is one small problem, and that is that the garden slopes away from
the house, and in order to gain sufficient height I would need to
install a gradient of much greater than 2%. For various reasons this is
undesirable, and could be avoided if the length of run were much greater
and the line were to loop back on itself while climbing. So therefore I
propose to build a "rectangular helix" of size approx. 16 feet by 8 feet
(two 4-ft radius semicircles joined by 8-ft straights) which should gain
1 foot of height in 2 turns at 1.25% (1 in 80), which is about the same
as the maximum gradient on the existing part of the layout.
My question is, has anybody on the list done this sort of thing before?
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