Any rules of thumb for size, radius, material, etc?
For here:
Not planning on building anything big (I'm jey), but something for messing about on.
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Building dirt jumps
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Posted 2 years ago #
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start small and build up
anything less than about 2ft high is pointless (unless your a weekend warrior or stuck in the early 90's, in which case it constitutes rad to the power of sick air)
Start with a tabletop about 2ft high (the height of your wheel), and 4ft (i.e. 1 bikes wheel base) tip-tip, round the top off so there isn't anything to catch a rear wheel on.
Unless you've got a lot of mates dont bother, it takes ages, and barrow loads of dirt just to build one small jump. Doing it on your own will take a day working flat out just to build one small jump properly. And 1 jump is no fun, needs to be part fo a set.
It's easier to learn on someone elses (well built) jumps, that way you get to see what works. Best place is a BMX track, theres nealry always 1 tabletop specificly for this purpous.
Posted 2 years ago # -
whats teh run up/out like?
build one. ride it. if its crap rebuild it better. dont skimp on the downslope.
length /height depends on run in speed and shape of kicker and what you want out of the jump.
material - a sandy clay is easiest to work with and allows quick/easy amendment.
you only really know what works by building it and riding it.
Posted 2 years ago # -
Hmm, my plan was to just stick a log down and build up some dirt next to it.
Posted 2 years ago # -
whats teh run up/out like?
Just what you see in the picture. The start is ten feet or so behind the camera. The end is the gate you can see over my left shoulder - that's a 6 foot high gate.
Dead flat.
Posted 2 years ago # -
is it a public path - looks fairly well used.
my experience is that whilst walkers will generally tolerate cheeky cyclists if stuff tsarts beign built they get all cross and either knock it down or get the authorities in.
Posted 2 years ago # -
is it a public path - looks fairly well used
Nope, it's the bottom of (what is soon to be) my garden. Horses from the paddock next door come in to keep the grass down, hence the path.
Posted 2 years ago # -
A log isnt realy high enough to learn to jump on, given soem height it might make a small dropoff to liven up an otherwise dull bit of trail, but its hard to get any pump (and therefore any height/speed) out of a transition that small.
I learnt on the back straight at bolehills in Sheffield, the first jump is a double about 6ft lip to lip and around the same height. Whilst that would take an unreasnoble time to build on your own, it was much easier to jump than the takeoffs with no landings that most trail centers consist of.
Posted 2 years ago # -
If it were my garden I'd start by building somethign wooden to get me going. Will be built quicker and if I didn't like it I wouldn;t have a ruddy great mound of earth to move to sort it out...
Posted 2 years ago # -
it might be better to build a pump track rather than a jump
whats the area size? if its just the photo area and nothing behind the camera then for defo a pump track.
Posted 2 years ago # -
This isn't dirt, but it still makes me chuckle. Somewhere near Colchester, I've forgotten where. I think it's a good lesson to have a wee bit of a think before you waste anybody's time and money!
Posted 2 years ago # -
Burying a log in the middle of it just means more work later on - they rot like crazy if buried!
Have you thought of looking around some tool hire places to see if you can hire a mini digger for a half day? Fairly easy to use, and quite a lot of fun, but also a great way to get most of the earth moving done.
Alternatively invite some friends 'round with their bikes and buy a load of beer. Pleasant way to spend an afternoon.
Posted 2 years ago # -
that's not a jump, it's a temporary structure for dwarf refugees
Posted 2 years ago # -
I'm interested in having a go at this too. This website is a pretty good summary of the information I've seen on other sites:
http://www.dirt-jumping.com/building_dirt_jumps.html
As far as shaping and size goes, as TINAS says, anything too small is quickly going to seem pointless, so make it a bit bigger than you think. My BMXer housemate told me that they would test their jumps by "ghosting" their bikes over them (i.e. pushing them with no rider on board).
Wwaswas's suggestion of building a wooden ramp is good too if you own a jigsaw and can get some plywood out of a skip. There's an example of one here:
http://www.pinkbike.com/forum/listcomments/?threadid=29852
Make two, and you can put them different distances apart and get a feeling for how fast you need to be going to clear a gap of a given distance. It's quite a buzz!
Posted 2 years ago # -
It's not wide for a pump track - no room to get a turn in at either end.
Posted 2 years ago # -
Pump track. Pump track. Pump track. Pump track. Pump track. Pump track.Pump track. Pump track.
Everything you need to know from the man himself:
http://www.leelikesbikes.com/ebook-welcome-to-pump-track-nation
Posted 2 years ago # -
I would think which way you want to be riding them (obviously you only have two options) if it's flat thats good I would find out where the sun is going to be at the time you would ride them and go the opposite way to that so your not riding into it. Work out how long you want the run in for the first jump, then you can either get the dirt from somewhere and build a jump if the land collects water or you can dig a hole/dip before the take off of the first jump and use the dirt extracted from that to make the take off. Ride the take off and see how far you go before making the landing then make the landing. Doubles will take a lot less time to make than tabletops which unless you can get a digger will take forever. WHen you have one jump built you should already know you can clear it as you built the landing according to how far you went on the test run, jump it and get comfortable nosing into the landing then repeat the process of digging a dip after the landing and building the next take off (so from one landing to the next take off there is a semi circle shape.) The second jump can be bigger than the first as you should have gained speed on the first if you have a good technique then the third can be bigger still etc. you will want to be confidant of riding the first one before building more as one small double isn't too intimidating but lots in a row and you worry how you are going to stop if you mess one up.
Iain
Posted 2 years ago # -
anything less than about 2ft high is pointless (unless your a weekend warrior or stuck in the early 90's, in which case it constitutes rad to the power of sick air)
This could well apply to me
I should probably asked about building jumps from dirt, rather than building dirt jumps. I'm not going to be practising superman front-flips or anything.
Posted 2 years ago # -
build a 4ft high table with 5ft deck to 4ft transition.ride over it,jump across it,learn to shape it and what that does to the way the jump works.in time you'll be sailing it safely and controlled enough to build another or enlarge the one you have
Posted 2 years ago # -
As Jedi says, build something like that. I.e a glentress tabletop size jump.
Nice and wide, not too steep but a big enough deck to land on. You can also boost the jumps at glentress reasonably well so tricking them isnt too much of a problem.
Very easy to learn on
Posted 2 years ago # -
there is easily enough room for a couple of turns and a few rollers.
you could always build a wallride to turn on if space on the ground is short.
it will be less work overall and more long term fun.
get your pump on baby!
Posted 2 years ago # -
If your going to build proper dirt jumps, the knack is to dig the bombholes and use that dirt to build the jump.
That way you have to shift less dirt to build the same effective height of jump.
Make sure you think very carefully about drainage other wise you'll end up with trails that wont ride ass soon as it gets slightly damp.
Whats the soil like? Your looking for a very sandy clay / very clayey sand, preferably with a low gravel and cobble component for best results. Have a dig down first and have a look at the soil - its most likely that the top soil will have lots of roots and organics in so is best used for the core of the jumps, the underlying soil is likely to be cleaner and have less junk in it and should be used for facing. Good jumps need good soil. You can always get a load of good topsoil off a builder doing a site strip - just check what its like before hand as 5ton of pure sand is **** all use.
The best way to start is to mark it all out first, make sure the distance between the jumps is right, not too short that you dont have time to set up for the next jump and not too long that you lose too much speed. Prob 2 - 3 bike lengths max, a lot depends on the slope of the land. By the looks of it you have so slope so it'll help maintain speed. If you leave a larger initial gap between jumps you can then enlarge them as your jumping skills progress without having to rebuild the whole line.
The first jump should be a fairly easy jump or roller/pump bump which is your 'set up jump' then in to the line. They should gradually increase in size as you go down the line too, i.e. 1st 4' gap, 2nd 5', 3rd 6' etc.
Once youve marked it out, cut and lift all the turf. Pile the sods up to form the core of your first jump then dig the bombhole in front of it shaping it in to the take off and using the dirt from the bombhole to face the jump.
You will want to test this one first to see how it jumps so you know how big to build the 2nd one, etc etc.
Posted 2 years ago # -
P.s. If your anywhere near the Midlands and have land - ive got a shovel and im quite happy to build jumps if i can ride them
Posted 2 years ago # -
In the "Mastering Mountain Bike Skills" book it describes a beginers jump as being 2-3ft high with a 1 to 3 height-to-length ratio.
It's a book I'd recommend to anyone.
Posted 2 years ago #
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