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Dirt Jump Building - Techniques and Tips

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Feb 5, 2010
67
0
Westminster, CO
After hundreds of hours of building dirt jumps, I have learned a lot of little things the hard way: through trial and error. I'm starting this thread as a place to post all of the little building tips and tricks you've learned along the way so new builders and diggers can learn to do things right the first time.

I'll be posting little tricks I use in my ongoing mission to rehabilitate the Lake Arbor Dirt Jumps in Arvada, Colorado (NW suburb of Denver), but all of you veteran diggers are encouraged to share the little pieces of knowledge you've learned along the way.
 
Feb 5, 2010
67
0
Westminster, CO
We've had a lot of rain recently in Denver, and my jumps have been super muddy for days. They're just now starting to dry up, with the exception of the pits between the landings and lips. The dirt ends up completely saturated with water and forms this skin on the top of it like chocolate pudding (the first picture)

This type of mud takes FOREVER to dry, as the skin locks in the moisture. BUT... there is a way to speed up the drying process. Take your rake and break up the muck (like the second picture). This increases surface area and causes the mud to dry out much faster. When it get to 'damp,' just rake it smooth and pack it out with your tool of choice (mine is the 8"x8" hand tamper).
 

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TortugaTonta

Monkey
Aug 27, 2008
540
0
Flat ground right up to a jump sucks.

Bowl everything.

If you have a flat stretch add rollers so you have a nice bowl to pump into the lip.
 
Feb 5, 2010
67
0
Westminster, CO
Flat ground right up to a jump sucks.

Bowl everything.

If you have a flat stretch add rollers so you have a nice bowl to pump into the lip.
True that. I like having a bowl dug into the ground prior to the first lip, and a mini (like 6" tall) kicker so I can air into it. Something about landing from an air (no matter how small) just sets my stance up for a good jump. If it's flat before a jump I'll just be all stiff in the air.
 

cmc

Turbo Monkey
Nov 17, 2006
2,061
6
austin
. . . They're just now starting to dry up, with the exception of the pits between the landings and lips. . . . .
The best thing I found is to not let water accumulate there to start with.

Because the pit is the riding line, it gets to be super-packed clay. Packed clay is frequently used as a liner (like in environmental engineering) so by its nature it won't let water through.

Even without doing a full-on "french drain" I've found that if you dig a hole in the side of the pit that is like 18" deeper than the riding line, it allows the water to soak downwards. As long as we keep these holes clear, we don't have to bail, ever! I didn't expect the water to drop down, I was thinking it would have nowhere to go, so it would just sit there. But, it has worked awesomely.


Milk Crate Drainage
http://www.ridemonkey.com/forums/showthread.php?t=240110



i started this thread back when we used to bail the pits all the time. now we don't do that at all. at most we sweep the little bit of accumulated water out into the lateral drainage trenches or the vertical french-style drains.

bailing out pits with bilge pump
http://www.ridemonkey.com/forums/showthread.php?t=218740
 
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cmc

Turbo Monkey
Nov 17, 2006
2,061
6
austin
I've discovered that the caliche in the Central Texas/hill country area can make surprisingly durable jumps, berms, and rollers. The stuff is horrible while you're trying to shape it, but once it is packed and dried, it stays solid and does not get very muddy either. Although I prefer clay mixes to ride on, this stuff is worth considering if it's available.. and you have a spot that you know is not going to get maintained.

http://en.wikipedia.org/wiki/Caliche

Caliche (the calcium carbonate mineral) is used in construction worldwide. The caliche reserves in the Llano Estacado in Texas can be used in the manufacture of Portland cement; the caliche meets the chemical composition requirements and has been used as a principal raw material in Portland cement production in at least one Texas plant. Where the calcium carbonate content is over 80 %, caliche can also be fired and used as a source of lime in areas, which can then be used for soil stabilization.


Caliche berm surrounding a stock tank in central TexasWhen mixed with small amounts of either pozzolan or Portland cement, caliche can also be used as a building material that will exceed the building code requirements for unfired masonry materials. For example, caliche was used to build some of the Mayan buildings in the Yucatán Peninsula in Mexico. A dormitory in Ingram, Texas and a demonstration building in Carrizo Springs, Texas for the United States Department of Energy were also built using caliche as part of studies by the Center for Maximum Potential Building Systems.

In many areas, caliche is also used for road construction, either as a surfacing material or, more commonly, as a base material. It is one of the most common road materials used in Southern Africa. Caliche is widely used as a base material when it is locally available and cheap. However it does not hold up to moisture, (rain), and is never used if a hard rock base material such as limestone is available.