# Future pump track specs/dirt composition



## kristenHS2 (Apr 2, 2013)

Hey All,

I am designing a public pump track (within a larger dirt park) in Colorado, and I am trying to get some info on dirt compositions (engineering design project). I know the ideal is the highest clay content/loam mixture, but what exactly would that be? 90/10 clay/loam? more or less? Thanks! the area is very dry, so rain isnt much of a problem besides a few weeks in the year. Attached is the design that I have thrown together from online research (I have zero experience with pump tracks), and just wondering what you guys think. The height is 55 ft, bottom length 80 ft, and top 20ft. Each side length is about 63 ft. I have a rough estimate of about 5000 cubic feet or 185 yards. Does that seem reasonable? The track is designed for intermediate/expert riders, as there will also be a beginner pump track across the street.

Thanks!
Kristen


----------



## slocaus (Jul 21, 2005)

We have not seen an exact percentage breakdown. IMBA has a good test:
18 Steps to Building a Dirt Jump or Freeride Park | International Mountain Bicycling Association


> 14. Get Good Dirt
> 
> The best soil for the surface of dirt jumps is screened loam with a fairly high clay content. Loam is ideal because it packs firmly and is easy to shape. You should be able form a ball by squeezing a handful of moist dirt. Clods that are difficult to break indicate too much clay content. Depending on the amount of rainfall in your area, the foundation for the jumps may need to be built from a more porous dirt that allows water to drain through, such as gravel or sandy loam. High-quality dirt can be reserved for takeoffs and landings.


Here is a simple way to analyze what you have.
DIY Soil Texture Test for Your Yard | Today's Homeowner

Investigate rammed earth construction for good info as well.


----------



## cjohnson (Jul 14, 2004)

cool design. I like the options and the size. 

To consider, the "S" curves may kill speed. Consider having the middle curve in each "S" be a roller, or least have a roller there be an option. The table top may be a bit big too. 

But, that is a very cool design.
Charlie


----------



## cmc4130 (Jan 30, 2008)

kristenHS2 said:


> Hey All,
> 
> I am designing a public pump track (within a larger dirt park) in Colorado, and I am trying to get some info on dirt compositions (engineering design project). I know the ideal is the highest clay content/loam mixture, but what exactly would that be? 90/10 clay/loam? more or less? Thanks! the area is very dry, so rain isnt much of a problem besides a few weeks in the year. Attached is the design that I have thrown together from online research (I have zero experience with pump tracks), and just wondering what you guys think. The height is 55 ft, bottom length 80 ft, and top 20ft. Each side length is about 63 ft. I have a rough estimate of about 5000 cubic feet or 185 yards. Does that seem reasonable? The track is designed for intermediate/expert riders, as there will also be a beginner pump track across the street.
> 
> ...


I've posted a ton of info over on this thread, so if you haven't already seen it, please read through the whole thing:

http://forums.mtbr.com/urban-dj-park/dj-pump-track-plans-402237.html

A few observations:
* 7 foot spacing and 18" tall is too high/close for rollers. I recommend 10 foot spaced rollers as a minimum. The 1:10 rule works pretty well. 1 foot tall, 10 feet peak to peak. 18" tall would be more like 15 feet peak to peak.
* The S lines may be a little too complicated. The best pump track is also a relatively simple one that allows for a lot of speed. I know from experience that S and M turns can be done, but they often require a lot of adjustment.
* Remember that paper/Internet plans should only be a guideline. Pump tracks are an art more than a science. Even small gradients can throw off a cookie-cutter design.
* Dirt has to be tested to determine if it will work. No matter what you ask for, you will not get consistent dirt. I have had many experiences with varying quality levels of dirt. "Baseball pitcher's mound"dirt is sometimes a good way to ask for dirt. 
* I think for intermediate/expert, your track is too small. If you're in a big park, make a big track ! Increase it to 120 feet on each side of the triangle.
* Intermediate/expert pump track riders are going to want to jump, and they're going to want tabletops, rollable doubles, roller-tables, monster rollers etc., possibly even a wood slant wall and drop-in ramp. The cutting edge of intermediate/expert pump track design is, in my opinion, the blended "jump track" or bmx-style pump track. 
* The best tracks are custom built to the landscape. Rather than saying the track has to be on flat ground because of the paper plans.... look around and see if there is interesting terrain to use and build accordingly. In the long run, it is a lot more fun to ride something custom that integrates with terrain features.
* You're going to need a water source to water the track regularly. Ongoing maintenance will be a fact of life. Will you have people to do this?


----------



## kristenHS2 (Apr 2, 2013)

cjohnson,

Thanks! I have definitely put some time into it. There is supposed to be rollers between each of the S turns, do you think that would be too scrunched? Supposed to have a down angle into the turn and up coming out of it. Could possibly combine and make the two lower S turns into one path for slightly larger S turns. I want the option there, as you can see the straight away option is on both sides as well.


----------



## kristenHS2 (Apr 2, 2013)

cmc4130 said:


> I've posted a ton of info over on this thread, so if you haven't already seen it, please read through the whole thing:
> 
> http://forums.mtbr.com/urban-dj-park/dj-pump-track-plans-402237.html
> 
> ...


Thanks for the feedback and info,

The pump track cannot be enlarged more because of the space allotted to the whole park is only ~400 x 85 ft, and all features must be 15 ft from the surrounding fence. The rest of the space is allotted to 3-4 track lines with several jumps and wooden features incorporated into it. The community already has a set up budget for the start ramps, wooden features, dirt, labor, water system, etc., to be ~$150,000. They are hiring people as well as building a strong support with the locals. It is a very flat section of land, and in the central part of a small city, right next to a skate park.

From my research online, I saw quite a few recommendations for 17 ft spacing and 1.5 ft tall, which brought me to that decision. The only part of the track that is a "jump" unless riders want to double up on rollers was the table top, as this is supposed to be more of a rhythm pump track vs. jumping pump track. All our plans are expected to be modified when the team of more experienced riders bring in the dirt and build it to what they thinks will work the best.

From research on baseball pitcher's mound dirt, it it was recommended to have 40%clay, 40% sand, and 20%silt, while IMBA recommends loam with fairly high clay content. I don't have the option to test out the dirt as I will not be on site. Do you think 50/50 clay and loam would work well? I am truly at a loss for the dirt composition.

Thanks for all your help,

Kristen


----------



## cmc4130 (Jan 30, 2008)

kristenHS2 said:


> From my research online, I saw quite a few recommendations for 17 ft spacing and 1.5 ft tall, which brought me to that decision. ....


17 ft. spacing? your drawing says 7', 8' and 10'. . . . . 10' is good. 7' is too close together unless they are a paired up set meant to be gapped.

even though they weren't intended as such. . . .these are a good example of pump track rollers

Jaguar Pump track 0001 - YouTube

if you pause the video several times and take note that his bike is about 5'6" from back of rear tire to front of front tire (whereas wheelbase is axle to axle).... then you'll note that the peak-to-peak distance is around 2 bike lengths, or 11 feet.

I've built a lot of rollers. the 10 to 13 foot range is excellent spacing.

Why will you not be out there when it's being built !?!?


----------



## kristenHS2 (Apr 2, 2013)

cmc4130 said:


> 17 ft. spacing? your drawing says 7', 8' and 10'. are those the peak to peak measurements?


Yes 7', sorry for the typo. I have no reference for that data as most of my research has come from forums and whatever people have posted on the internet. Yes those are peak to peak.


----------



## cmc4130 (Jan 30, 2008)

kristenHS2 said:


> Yes 7', sorry for the typo. I have no reference for that data as most of my research has come from forums and whatever people have posted on the internet. Yes those are peak to peak.


7' spacing and 18" high still is not ideal. have you read the Lee Likes Bikes "Welcome to Pump Track Nation" e-book? He's the one that talked about 1:10 ratio spacing. that means 1 foot tall and 10 feet apart, or 18" tall and 15 feet apart.....

so, have you read through this thread yet? 
http://forums.mtbr.com/urban-dj-park/dj-pump-track-plans-402237.html


----------



## cmc4130 (Jan 30, 2008)

also, check out this pump track. it has several of the features I was talking about for interemediate/advanced pump tracks. it has a roll-in area, it has tables with rounded corners, rollable doubles (aka camelbacks)...

Dirtworks - BMX pump track - Nottingham - YouTube

also, check this video on the roller-spacing.

First ride Eurobike 2011 - Demoday Bikeparkitect Pumptrack - YouTube
I would estimate these to be over 2 bike lengths peak to peak. probably 14' or so. look how mellow the shape is too. this is good.


----------



## jackbombay (Nov 15, 2010)

I have ordered, moved, and compacted a lot of dirt/gravel in my life and it will compact notably, I typically take my finished volumes and multiply by 1.3 and order that. For your track you should order 240 yards. I think you lose closer to %25 to compaction than the %30 I add, but you will always find a way to use any extra you may have, and its pretty rare you have enough extra for it to be an issue.


----------



## kristenHS2 (Apr 2, 2013)

jackbombay said:


> I have ordered, moved, and compacted a lot of dirt/gravel in my life and it will compact notably, I typically take my finished volumes and multiply by 1.3 and order that. For your track you should order 240 yards. I think you lose closer to %25 to compaction than the %30 I add, but you will always find a way to use any extra you may have, and its pretty rare you have enough extra for it to be an issue.


Thanks Jack! My volumes actually were calculated to about 150 yards, and then I scaled up a bit to the 185. It was a very rough estimate though, so I might order a bit more (if it's not used in the pump track, it can be used for the rest of the jump lines in the park).


----------



## kristenHS2 (Apr 2, 2013)

cmc, 

No I have not read the e-book, as this is my college engineering project and the funds aren't going towards us designing the project. I will certainly take that data into consideration for the final design submitted. I did briefly run through the whole thread and there is some great info there thanks! I believe some of my group members have gotten info from that thread for the track lines and jumps as well.


----------



## cmc4130 (Jan 30, 2008)

how did y'all come up with 240 yards and 150 yards ?

_"Length X Width X Average Height / 27 = cubic yards. Multiply by 1.3 to account for soil compaction. To get the average height, figure half the height of your rollers and berms."_

This is from Lee Likes Bikes.

Sometimes looking at wood and concrete designs can help you think about dirt. . . . 









Note the transitioned-face bowl corner style berms. These are extremely effective because the rider gets to "pick their line" around the turn. If you're going slow, you ride it low. If you're going fast you rail it higher (and more sideways). 









Are your 5 foot tall berms doing a low-high-low pattern like this?








I discussed that over here: https://forums.mtbr.com/urban-dj-park/dj-pump-track-plans-402237-8.html#post9936476

They don't have to. They can also be the low-riding-line style berm like this one at Mark Weir's:









Also, I kind of doubt your 4 foot tall 8 foot deck table top is going to work in the spot that you have it.. It'll be rideable, but I forsee people just rolling it or manualing it... There may or may not be enough speed to actually jump it. 
I suggest a version of a roller-table that is more like 2'6"-ish tall....









This is a spot in Colorado, from LeeLikesBikes.com. I think the rollable doubles (aka camel back tables) in an outer-perimeter loop are an excellent idea. . . .


----------



## jackbombay (Nov 15, 2010)

cmc4130 said:


> how did y'all come up with 240 yards and 150 yards ?
> 
> _"Length X Width X Average Height / 27 = cubic yards. Multiply by 1.3 to account for soil compaction. To get the average height, figure half the height of your rollers and berms."_


 I didn't do any volume calculations, they are easy enough with a basic understanding of geometry so I figure an engineering student shouldn't have any problem with them thus no need to double check the numbers.

Its cool to see that others have arrived at the same %30 number I did.


----------



## cmc4130 (Jan 30, 2008)

jackbombay said:


> I didn't do any volume calculations, they are easy enough with a basic understanding of geometry so I figure an engineering student shouldn't have any problem with them thus no need to double check the numbers.
> 
> Its cool to see that others have arrived at the same %30 number I did.


right on. . . . I agree on the estimates...


----------



## kristenHS2 (Apr 2, 2013)

cmc4130 said:


> 17 ft. spacing? your drawing says 7', 8' and 10'. . . . . 10' is good. 7' is too close together unless they are a paired up set meant to be gapped.
> 
> even though they weren't intended as such. . . .these are a good example of pump track rollers
> 
> ...


Just realized the last part about not being there. My team of engineering students is actually in a different state from the site, and I have never seen the place (one of my group members is from there). The city contacted him through some means and it is now our junior design project for an engineering class. We're doing this for a grade, and the city will use our project to help push forward their plans for a new bike park (cutting out some of the typical wait periods and costs). All of our plans are a rough sketch and design of the area, while professionals will actually be building the jumps and editing them on site as they see fit.


----------



## cmc4130 (Jan 30, 2008)

kristenHS2 said:


> Just realized the last part about not being there. My team of engineering students is actually in a different state from the site, and I have never seen the place (one of my group members is from there). The city contacted him through some means and it is now our junior design project for an engineering class. We're doing this for a grade, and the city will use our project to help push forward their plans for a new bike park (cutting out some of the typical wait periods and costs). All of our plans are a rough sketch and design of the area, while professionals will actually be building the jumps and editing them on site as they see fit.


right on ! that would have been fun to do in college.

btw, the triangle aspect of your track design reminds me a little of this one:

Stowe Bike Park Pump Track - YouTube
what i like about the Stowe track is that there appear to be 4 rollable tables... the rollers are also big and spaced out for full bike pumping. (think: wheelbase up, wheelbase over, wheelbase down).... it's a more surf / wave style.

this one also has cool stuff going on:








Johnson Pumptrack and Dirtjumps - YouTube

once again, note the longer roller spacing and the rollable tables. also note the starting platform. it is much more fun to start from a higher point and "drop in" to a track. the idea of starting anywhere in the track and taking a few cranks to get going is fine.... but things really have evolved from that. if you want this track to be "cool"... tell your teacher that the experts have advised a starting-and-hanging-out platform....

i was asked to help tune this pump track that was already built... 
Reveille Peak Ranch-pumptrack-oct 2011 | Flickr - Photo Sharing!
note how the riders are all using the deck as a starting platform. that wasn't the landowners original intention. he thought it was going to be for spectators. also note how because the rollers are smaller and closer together, it's more of a hamsterish effort to pump, rather than the surfy style at Stowe.

just a few things to think about... i know this is just for a class grade... i'm pointing these out for everyone else on the forum as well.


----------



## kristenHS2 (Apr 2, 2013)

Im sorry there's so much information for me to reply to everything haha, just know I am taking everything into account. Also, even though its just my class grade it IS a future bike park, and the city has already approved the cost and such. They are hoping to have it up and running ~ a year or year in a half. The really large roller at the top of the triangle I was thinking would be more of the starting jump, and could be worked with to get some decent speed. Maybe slightly higher on one end than the other.


----------



## cmc4130 (Jan 30, 2008)

:thumbsup:


----------



## cmc4130 (Jan 30, 2008)

I wonder what happened with this?!


----------

