Corbin and I have built a number of ladder bridges and such in
preparation for this year's CMW trials comp... see:
http://tinyurl.com/35dpmm
There isn't any hard and fast measurement for the gap between slats,
but a good place to start is to use a slat to measure the gap itself...
that is, if you're using 2x3s for slats, then a 3"ish gap between slats
is fine. You may want to use more of a gap to conserve wood.. it's
still totally rideable, probably up to 5" or so. Above that, your ride
will get bumpier and bumpier.
As for other tips, pay attention to the slope of your "ups" and
"downs". If you make your "ups" too steep you may have a hard time
getting onto your bridge... when in doubt, make it more shallow than
steep. Also, steep "downs" are rideable, but only as long as you
provide a decent transition (to flat) at the end. If you run a steep
down right into the ground (w/o transition) that's a recipe for serious
injury.
We've found that 2x6s make for great bridge supports that don't require
much bracing. 2x4s work well but get wobbly after some distance.
All the logs we've used for supports have been placed into 1-2 ft deep
post holes. After compacting the dirt around the log, it doesn't
require any other bracing to remain upright... which means less work!
Corbin uses a chainsaw to "square off" the top of each log to allow for
attaching the 2x6s.
We've used nails throughout the course, and this allows for a bit of
flex in the obstacles. To be sure, use longer nails than necessary so
that flexing doesn't cause things to fall apart.
As for designing your obstacles, make sure to put some things up that
are a bit too hard for you to ride. As you get better, your course
will get easier, and it's nice to have a few things to challenge
yourself with.
Have fun building and riding! Send us some pictures when you're done.
--
maestro8
Those are my principles. If you don't like those, I have others. --
Groucho Marx
The only way to comprehend what mathematicians mean by Infinity is to
contemplate the extent of human stupidity. -- François-Marie Arouet de
Voltaire
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