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Building Technical Structures:

We at Dieselbikes are in the process of building a (continuing) technical guide to help you, the rider build challenging mountain bike structures to increase your riding skills.  We do not want to limit our objectives by classify this information as “stunts” or “freeriding related”, but rather provide ideas  to help build technical structures for all rider skill levels.

The information listed on this website is for informational purposes only and does not constitute a standard, specification or regulation.   If you download and/or use this information, we at Dieselbikes are not legally responsible for any injury or death.

Three Important Factors to Consider:

#1: Selecting your lumber.

This is one of the most important steps for designing and building your technical structure.  Weather conditions in your area will determine the proper lumber grade and type of wood to choose.  In New England due to our four seasons, typical the use of PT-ACQ pine grade No.3 is used for main structure supports and/or stringers.  Decking can be un-treated wood, but this will be dependent on structure type and intended use.

Un-treated Lumber:

Most lumber supply stores and/or outlets (example: Lowes) carry two basic categories of wood; "Select" or "Common".

"Select" lumber is typically used for finish work and is broken down into the following grades:

- Grade A or B typically have minute or no blemishes.
- Grade C typically has some minor defects such as small knots.
- Grade D typically has larger imperfections.

"Common" Lumber is typically used for general-purpose construction and is broken down into the following grades:

- Grade No.1 contains tight knots and few blemishes.
- Grade No.2 contains larger knots and blemishes.
- Grade No.3 has loose knots, knotholes, and other flaws.
- Grade No.4 is low quality
- Grade No.5 where the appearance is not important.

Pressure Treated Lumber (PT):

Most lumber supply stores and/or outlets (example: Lowes) carry Amine Copper Quat (ACQ) and/or Copper Azone (CA) chemically treated lumber better know as PT.  ACQ-PT is the more typical found here in New England, but this will vary state to state.  PT Lumber is categorized as “Common”, so the same grades No.1 ~ No.5 applies.

Wood Type Selection:

There are two (2) general type categories of wood; Hardwoods and Softwoods.

Hardwoods:

Unless you plan on making your technical element just for show, it will not be outside and have an unlimited amount of money to spend, we suggest you do not use hardwoods.  However, hardwoods such as oak, white oak and cypress are naturally resistant to decay over long periods of time.  Many hardwoods are suitable for exterior structures but cost and fabrication becomes major factors.

Softwoods:

Pine: It has uniform texture, easy to work with and finishes well.  It has a high resistance to shrinkage, swelling and warping.  Can be pricey per linier foot but is a general available off the shelf.  Pine does decay over short periods of time and in some cases may need to be treated.

Hemlock: Light in weight, uniformly textured.  Easy to work with and has low resistance to decay and nonresinous.  Excellent choice for ladder bridge decking.

Fir: Works easy and finishes well.  Uniform in texture and nonresinous, plus has a low resistance to decay.

Redwood: Light in weight, durable and easy to work.  Has a natural resistance to decay.  You can use this wood for anything outdoors, but you better be ready to shell out some cash.

Spruce: Strong, hard and finishes well with low resistance to decay.  Has moderate shrinkage and light in weight.  Good material selection for Sea Saws.

Cedar: Easy to work with and uniform in texture with very high resistance to decay.  Similar to redwood for using it outdoors, but you better be ready to shell out some cash.

#2: Selecting your Hardware

Another important aspect in designing a technical structure is appropriate hardware.  With so many options to choose from, one can be left with questions.  We have listed below some general hardware options to choose from but ultimately it will depend on the type and location of the technical structure you are building.  In short, much of the same hardware required to build your own technical element is much the same as building a wooden deck in your backyard.

Exterior Screws:

Typically exterior screws are either galvanized or chemically treated.  The choice material for exterior screws is steel but there are composite with the same or stronger properties to resist vibration and weather over long periods of time.  A good rule of thumb is to use 2-1/2 inch or longer screws for most technical projects.  Screws that are shorter then 2-1/2 may not have enough “bit” (distance threaded into the wood) and eventually put-out.

Exterior Nails:

Typically exterior nails are either galvanized or chemically treated. The use of “Ring Nails” or “Framing Nails” is recommended.  These nails ensure excellent grip when installed correctly and resist backing out over time as the woods expands and contracts due to changing weather and/or temperature conditions.  A good rule of thumb is to use COMMON 16D SIZE nails or larger.  They will provide excellent support to carry applied loads to the structure.

Lags (Lag Screws):

Typically Lags are available galvanized for exterior use.  Lags provide excellent support and load carrying properties.  When ever using lags to secure two (or more) pieces of wood, you should always place a flat washer between the wood and the lag head to ensure even head pressure is applied as you secure the pieces of wood together.  A good rule of thumb is to use 3/8”x4” Lags (or larger) for any structures that are elevated 4 or more feet off the ground or have moving/pivot points.  Also Lags should be used if you are concerned about the weight or span of the structure you build.

Carriage Bolts:

Typically Carriage Bolts are available galvanized for exterior use.  Carriage Bolts are ideal for securing ladder bridge supports or used on fabricated transitions.  They will provide structural support and absorb enormous loads.  When ever using Carriage Bolts, the use of flat washers for both the bolt head and nut side should be used to ensure even pressure as you secure the wood.  The use of a LOCK NUT is suggested so that the Carriage Bolt assembly is shielded from vibration.

Joist Hangers:

If you plan on build an elevated platform similar to a deck, you should consider using Joist Hangers.  They will provide extra support for your elevated structure and help support stringers during load (weight of you and the bike) transfers.  Also depending on how large your platform is, joist hangers will help reduce structural movement and absorb vibration.

#3: What not to Do

We may be restating the obvious but here are a few things of what not to do when building a wooden mountain bike technical structure.

a.  If you never built a technical structure before, start small, then make the next one bigger.

b.  You should not build your stunt from wood that is rotting and/or decaying

c.  Using shipping pallets as a landing transition, elevated platform or ladder bridge is not advised. Shipping pallets are typically design to carry a static loads (never changes), not dynamic loads (consistently changes).

d.  Never use nails to secure a joint that will carry the weight of your structure. Example is using nails to secure a stringer to the side of a vertical support. No matter how many nails you use, (even if you toe-nail them) they will pull out.

e.  Do not use interior nails/screws.

f.   More to come…