Longboards

Mike Jen3/17/2010

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---Audience and Scope---

This article is aimed at informing someone who is interested in buying a new longboard so that they will be well informed about the mechanics involved in each part of it. The audience has a limited amount of knowledge about the basic properties of a longboard and the different techniques and disciplines of longboarding. Reading this paper will help the audience pick the right gear to ride at the next level.

Nowadays, everyone is looking for alternative ways of transportation to cut down on the use gasoline and pollution. A longboard can definitely be a viable method of transportation as well as a fun recreational activity and way to stay active.

---Introduction---

A longboard is a skateboard that is generally longer, sometimes wider, and is used for different purposes. Although the exact time and place of origin of longboarding is not known, longboards arose sometime in the mid 1900’s, primarily as a land-based surfing alternative. They have many different parts, and each part has many different customizable variations.

On the surface, a longboard consists of a deck, trucks, and wheels. However, there are a lot of smaller subparts such as bushings, mounting hardware, kingpins, washers, pivot cups, bearings, speed rings, bearing spacers, and nuts. Variations of all these small parts are important for different intended uses.

---The Deck---

This is what you stand on. Plain and simple. However, a longboard deck is not a simple mass-produced stick of wood the way that traditional skateboards are.

Materials

A longboard deck can be made out of a wide variety of materials. Usually wood is the base material. Large companies tend to use some of the commonly used woods such as Bamboo, Canadian Maple, and Baltic Birch. However, smaller builders sometimes use various other types of hardwood and plywood.

Many decks are built using composite materials in addition to wood. Fiberglass is commonly used to strengthen wood boards. Putting fiberglass on the top of a board increases the torsional stiffness, while putting it on the bottom increases tensional stiffness. It is most commonly used on the bottom. Carbon fiber is sometimes used on boards that have a foam core in a wooden frame. This type of construction reduces weight while retaining strength, as carbon fiber can be quite stiff while light. The carbon fiber’s stiffness makes a full wood board unnecessary, so foam is used as a core.

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Size and Shape

Decks also come in many different shapes and sizes. A typical longboard usually measures roughly 42 inches x ~9 inches. However, it is possible for longboards to be as long as 60 inches

or as short as 22 inches, and as wide as 11 inches or as thin as 7 inches. Of course more extremes do exist, but are rarely seen.

Most boards fit into 3 basic shape classifications: pintails (teardrop shaped), cruisers (similar to a larger shortboard), and cutout decks (sections of the deck near the wheels are removed). Variations of these three basic shapes form the majority of longboard decks, and there are possibly hundreds of different designs in existence. Figure 1 shows 3 examples of different shapes. All three are cutouts, but they all have very different shapes.

Strength

Different decks also have different strengths. That is, some decks are quite stiff, while other decks are quite flexible. Stiff decks are generally preferred for high speed riding, while flexible decks are preferred for lower speed riding, as they are considered by most to be more comfortable and provide a more surf-like feel. Flexible decks have a property called ‘flex,’ which refers to their ability to bend down under compression and spring back into their original shape after the pressure is lifted. Some flexible decks have been known to survive being run over by cars.

Curvature

Different decks have a variety of different curvatures. Some decks have concave, which creates a slight “U” shape when looking straight on at the nose. Concave is used to lock the rider’s feet into the deck better. It also makes the deck stiffer. Camber is when the deck has a bowed up appearance from the side, like a hill. This is used to create more flex, as it allows the deck to be bent back to flat, then further into the negative before springing back. On the other hand, rocker is when the deck starts with a bowed down appearance from the side, like a valley. This is typically only used on stiffer decks and is helpful for locking in a rider’s feet, similar to concave. Riding style and personal preference are the major factors in determining deck curvatures.

Grip

Typically, a deck is covered with some kind of material to increase the grip that the rider’s feet have on the deck. This is accomplished by increasing the friction between the deck and the feet. The most common way of doing this is by using grip tape, a commercially manufactured product that consists of a sheet of rough material with an adhesive backing. However, it is possible to create the same effect by sprinkling a rough material such as sand or ground up glass onto a deck and covering it with a layer of resin, which hardens over the sand. A less commonly used

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Figure 1. A few examples of unique deck shapes

method is to use surfboard wax, which was designed to help surfers keep their feet on their surfboard.

Mounting

There are a few different ways to mount the trucks to the deck. A topmount is the traditional style where the truck is completely underneath the deck. This type of mounting provides the highest riding height. Drop-through mounting is when there is a hole cut through the deck, so part of the truck sits on top of the deck, while the rest hangs underneath. This provides a lower ride. Also, a dropped deck is when the standing platform (middle) of the deck is lower than the ends (on which the trucks are mounted). Figure 2 provides a visual for these different arrangements, as well as the double-drop, which is when the board is a drop-through mount with a dropped deck. The ride height is lowered because a lower center of gravity is more stable and easier to push.

---The Trucks---

The trucks are attached to the deck and hold the wheels. A typical truck basically consists of two parts: the baseplate and the hanger. The baseplate is the part that is attached to the deck, while the hanger is the part that directly holds the wheels.

Baseplate and mounting hardware

A baseplate typically has 4 or 6 holes drilled through it in order to mount it to the board. Mounting hardware is used to attach the baseplate. A set of mounting hardware consists of 8 small bolts and 8 small nuts. The bolts are usually 1 inch to 1.5 inches in length. The baseplate also has a pivot cup and a hole for the kingpin, angled in such a way that different baseplates can have different pivot angles (different angles have different turning radii). These features, as well as the other ones discussed in this section, may be viewed in Figure 3.

Kingpins and nuts

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Figure 2. Different mounting stylesMounting styles - Randal.com

Randal Anatomy - Randal.comFigure 3. Labeled diagram of a typical truck

A kingpin, which is a large threaded bolt, is used to secure the hanger to the baseplate. These are typically made out of steel (although some are titanium for extra strength), and range in length from 2.5 inches to 3.5 inches. The kingpin can be tightened to reduce the turning capacity of the truck or loosened to increase it.

Trucks house three different nut sizes. There are the small nuts that are used to hold the mounting hardware, medium sized nuts which hold the wheels on (axle nuts), and large nuts that secure and tighten the kingpin (kingpin nuts).

Bushings

Bushings are small pieces of urethane that fit on the kingpin on either side of the hanger. They come in a variety of shapes: cones, barrels, and pumpkins. Cones are obviously shaped as cones, barrels are cylinders, and pumpkins are shorter and wider in their rounded middle. Figure 4 shows examples of all three bushing shapes. Bushings have different hardnesses, similar to the way that wheels have different hardnesses (described below). Harder bushings provide more resistance to turning, softer provide less. Cones provide the least resistance/spring back, barrels provide more,

and pumpkins provide the most. Washers are placed on outer sides of the bushings to prevent them from being damaged. Cupped washers and flat washers are used – cupped washers restrict the compression of the bushings more.

Hanger

The hanger attaches into the baseplate by the pivot, which should fit snugly into the pivot cup. It is a T-shaped piece of metal, with thinner axles protruding from the ends that do not have the pivot. Axles in popular production are either 8mm wide or 10mm in diameter. Hangers vary in width, ranging anywhere from 125 mm to 205 mm easily. Wheels are mounted onto the axles.

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Venom bushings - Muirskate.comFigure 4. A pile of Venom bushings

---The Wheels---

No reinvention has been done here – the wheel is still a wheel. At high speeds, it is possible for these colorful parts to reach over 6000 RPM!

Shape and Size

Made of urethane, longboard wheels are generally larger and softer than normal skateboard wheels. They are cylindrically shaped, with sizes ranging from 65-80 mm in diameter, although there are some smaller and some larger. Widths are also variable, ranging from around 45-55 mm, although there can also be some thinner or wider types. Some wheels have a large ‘lip’ that protrudes from the edges and increases the wheel’s width. Wheels with large lips have more grip, while wheels without lips have less grip and are more geared towards sliding. In Figure 5, the wheels in the leftmost stack do not have lips.

Hardness

The hardness of the wheel is assessed based on a numerical scale called durometer. A lower number durometer means a softer wheel, while a higher number means a harder wheel. Typical durometer ratings range from 65a-88a, again with exceptions. Softer wheels grip the pavement better and ride smoother, while harder wheels slide easier and create a bumpier ride. Also, a wider wheel grips more while a thinner wheel slides easier. As such, wheel choice is important depending on the intention of the rider.

There is a large opening in the middle of the wheel which houses the bearings. This hole can be set in the center of the wheel, to the far side of the wheel, or in between. These different settings are known as center set, side set, and offset respectively. Center set wheels tend to slide more while side set wheels tend to grip more, with offset in between.

Bearings

Each wheel holds two bearings. In between the two bearings there is an open space in which a bearing spacer can be placed. Bearing spacers are used to prevent the bearings from deforming due to the stress of some types of riding. Sliding, which is when the wheels are forced to slide sideways along the ground, will eventually deform bearings without spacers.

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Figure 5. A few examples of different wheels

Bearings are donut shaped, with the inner race fitting snugly around the axle, and the outer race fitting snugly into the middle of the wheel. The bearing houses several ball bearings, which are small balls that are usually made of steel, but can also be made of ceramic. The ball bearings sit around the donut-shaped bearing, housed in a retainer. Figure 6 is a good diagram of the anatomy of a bearing.

It is very important to keep the bearings clean, because if dirt or other particulates clog the track, the bearing can seize up and stop spinning. Either grease or a lubricant is used to prevent the ball bearings from running dry, as

the balls are more susceptible to damage when dry. Steel bearings can rust and seize if they are exposed to water without grease. If any one of the 8 bearings seizes, the entire board will stop, and the rider will likely fall off. With 6 or 7 ball bearings per bearing, there are 48 to 56 opportunities for a ball bearing to become damaged and potentially end up causing injury.

Wheel Mounting

When the wheel is mounted onto the axle, small thin washers called speed rings are placed on either side of the outer edges of the bearings. They are just large enough to fit on the axle and just wide enough to cover the inside rim of the bearing. Using speed rings allows the axle nut to be tightened snugly without restricting the spin of the bearing.

---Conclusion---

Almost every part of a longboard is customizable. Once a person develops their own style, it is easy to pick and choose exactly what parts they want. Hopefully you have gained some insight into the subparts of a longboard after reading this paper. It is important to understand how every little thing will affect the way it rides if you truly want to optimize your longboard.

For example, a good speedboard setup could be:Deck: Stiff, ~40 inches x ~10 inches, heavy concave, topmount droppedTrucks: Wide hanger, 90a barrel bushings, low pivot angle, tight kingpinWheels: 70 mm diameter, ~50 mm wide with lip, 80a durometer, spacers, speedringsThis setup focuses on stability, which is essential for high speed riding.

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Bonesbearings.comFigure 6. Diagram of a disassembled bearing

Works Cited

"Bearing Maintenance". Bones Bearings. 7 March 2010 <http://bonesbearings.com/support/maintenance/>.

"Muir Skate". Muir Surf and Sport. 3 March 2010 <http://www.muirskate.com/>.

"Randal Skateboard Trucks - General Truck FAQ". Randal Truck Co.. <http://www.randal.com/guides_faq.html>.

"Silverfish Longboarding - The Longboard Skateboard Community". Silverfish Longboarding. 1 March 2010 <http://www.silverfishlongboarding.com/>.

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