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Thread: Angles - help!

  1. #1
    Albany West Oz
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    Angles - help!

    My club is planning an urban downhill with built ramps, was trying to find some info on relationship between jump angle and height and downramp angle?

    Specifics or general rules?

    If fast then long gradual downramp?
    High and slow then steep short?

    As it will be a race was thinking no kicker on jumps, more of a wedge, so downramp in that case just a mirror image?

    Links, advice, abuse

  2. #2
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    This ought to help some.

    Projectile motion - Wikipedia, the free encyclopedia

    If you think about it, once the bike leaves a ramp, it's more or less following typical projectile motion. Departure speed and angle will govern what you do with the landing area.

  3. #3
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    Quote Originally Posted by Freediver View Post
    My club is planning an urban downhill with built ramps, was trying to find some info on relationship between jump angle and height and downramp angle?

    Specifics or general rules?

    If fast then long gradual downramp?
    High and slow then steep short?

    As it will be a race was thinking no kicker on jumps, more of a wedge, so downramp in that case just a mirror image?

    Links, advice, abuse
    I have a huge thread called DJ, Pump Track Plans over in the DJ/Urban forum:
    DJ , Pump Track plans

    But, I understand your question is more narrow to wedge style jumps. Who is going to be jumping these? Downhill riders on DH bikes? Or XC/AM riders who typically don't jump a lot? It matters a lot. There are ways to design jumps for nearly every type of rider and they should always be integrated well to the terrain and consistent with the speed of the trail.

    To answer your basic question though, always err on the side of mellowness. The most common beginner mistake in jump building is building things that are too abrupt or steep.

    This type of launch ramp may be typical in skateboarding and bmx:


    But this type is much more typical for mtb:


    My personal opinion is that beginners should be able to get at least a full wheelbase onto the surface of the launch. So the surface is an absolute minimum of 6'. 8' is better. 10-14 for more high speed stuff.

    The distance you clear is way more a function of your speed than of the angle of the launch. Therefore, a mellow jump like this--even though it is 10'-ish feet peak to peak, will be very easy for people to clear, with just some practice. Short gap get old really quickly.


    20 degree triangle:


    Even a 15 degree triangle would be good for beginner or non-jumping XC/AM riders. Like 8 feet of surface and 2 feet of height.
    Right Triangle Angle And Side Calculator

    here's a version with a little bit of transition (curve):


    this shape is only for boosting high and/or doing tricks and is more suitable for slopestyle and DJ hard tail bikes. you would not use this shape as part of a DH race....




    I used to ride this style of wedge ramp in my friend's driveway back in the day. They were usually 3-4 feet tall and 1 sheet of 4 X 8' ply as the surface. For actually jumping this to flat ground though, 4' is too tall. 2'6" or 3' would be more appropriate for an urban DH race, unless there's a pretty seriously huge grass slope landing....


    I helped design this for the local MTB club. A true DJ/DH rider who is hauling ass and will overclear the landing almost to flat, but I designed it for "everybody else" and they had a blast. The A Bomb on Vimeo


    Peanut Butter

    in terms of landings.... gradual/mellow and really long is always better than tall and steep, if your goal is versatility. a long mellow landing can be jumped at slow speeds or at fast speeds. a short steep landing can really only be hit at one exact speed. if you're going too fast for it, then it becomes totally useless. in your urban environment, look out for natural slants that can be used as landings, then set the launch 10-14 feet back from that.

    here's a good example of finding a grass slant landing. this is really common in BMX street riding. you try to find some huge drop that has a nice long slant landing .... grass,


    or not grass:

    Last edited by cmc4130; 09-24-2013 at 06:10 PM.

  4. #4
    Albany West Oz
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    Awesome post, thanks. The jumps are in the context of a DH race, We are planning something like this But we would like the ramps and berms prefabricated with steel frames. We will make a range of sizes but the angles will probably be the same.

  5. #5
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    Quote Originally Posted by Freediver View Post
    Awesome post, thanks. The jumps are in the context of a DH race, We are planning something like this But we would like the ramps and berms prefabricated with steel frames. We will make a range of sizes but the angles will probably be the same.
    okay, I get it. I've seen quite a few of those videos....



    It kinda sounds like you need to work with some downhill riders and maybe a pro course designer/pro ramp builder. there's a lot of planning in terms of how the course is going to feel, the size of jumps for speed etc. Both the angles and sizes of the jumps and landings should vary depending on the particular jump and part of the course. Certain parts of the course should have mellow angles for high speed, but other parts might be deliberately designed for more air/style/tricks.

    steel frame ramps are expensive. in the bmx world and mtb-DJ/slopestyle world, they are usually only used for touring bmx shows and permanent bike parks, not for one-time events. but if you plan on keeping all these ramps somewhere, i suppose it could be worth it to do steel.

    something like Colorado Freeride Festival builds the whole course from wood and dirt:




    yours truly, at a spot I've been helping at (but primarily designed by Abel Jaramillo):

    Twin Parks, Dripping Springs, Texas

  6. #6
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    Jimmy Levan knows how to use angles!

  7. #7
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    All good ideas and images to inspire. A few nights up way too late and the grant application is finally in. Now we wait on money and I can start to hand out some work to the downhill guys and they can get some designs happening! Cheers. Will keep you posted on progress.

    Ps steel framed ramps as we hope to make it an annual event and build on it each year.

  8. #8
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    Quote Originally Posted by Freediver View Post
    All good ideas and images to inspire. A few nights up way too late and the grant application is finally in. Now we wait on money and I can start to hand out some work to the downhill guys and they can get some designs happening! Cheers. Will keep you posted on progress.

    Ps steel framed ramps as we hope to make it an annual event and build on it each year.
    Any news ?!

  9. #9
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    Hey,

    Grant is announced at end of this month but we are pretty confident. Have had a good group pick up different responsibilities and there has been some detailed planning of the route and features, they are working on ramp sizes, gap distances and the best spot/size for berms.

    Next problem is getting enough time with the roads closed to have sufficient practice and race runs before we cut to a top 30 for a final. If we attract over 100 riders, and we will, at 30 sec intervals, 2 practice 2 race runs. At 50 minutes each run minimum plus breaks for traffic flow. The track is 2.7km (1.8 mile).

    Thanks for interest, I'll update as we go.

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