Single Layer Tearoffs

Tearoffs are universally used in motorsports as multi-layered disposable lenses. As the race proceeds, the top layer accumulates mud, rubber, fuel, oil and water, which eventually obscure the rider's vision. The top layer of tearoff is removed by the rider, which reveals the next clean layer. This is repeated through the course of the race until the rider exhausts the supply of tearoffs and is left visually impaired for the balance of the event. An apparent solution to this problem might be to add additional tearoffs to the face shield, but experience shows that six or seven tearoffs reduce visibility to the point where it would be unsafe to enter the track. In simple terms, the rider starts the race blind with too many tearoffs, and ends the race blind with too few. While a single layer tearoff is nothing more than simple thin piece of plastic, the Velocity SpeedStack7™ is a complex optical device, having all the characteristics found in a camera lens or telescope. Most single layer tearoffs use "packaging grade" clear polyester. Velocity Tearoffs starts by using only the highest quality "optical grade" Mylar™, manufactured by DuPont.

Optical Transmission And Reflection Basics

Everything that is transparent to light, everything you can see through, slows down the speed of light. There are all kinds of wacky things that happen when light is slowed down, but one thing we are concerned with is reflection. The more a material slows down the speed of light, the more it reflects off the surface. To compare; air slows light and reflects it the least, water more, glass and plastics more yet, and diamonds the most. Which is why a diamond is so sparkly. For plastics used in tearoffs, about 4% of the light reflects off of the surface as the light passes from air into the plastic. There are two surfaces on each tearoff, one going in and one going out. Thus the reflection is about 8% for every tearoff used. This also means that the transmission is reduced to about 92%.

Looking In The Mirror Is No Way To Win A Race

As successive layers of tearoffs are added, the reflection increases by 8% per tearoff, while the transmission is reduced by 8%. By the time six or seven tearoffs are stacked up, the transmission is reduced to 50%, and the reflection is up to 50%. The loss in transmission would be like putting on sunglasses, and the increase in reflection is like looking in a mirror. The technical measure of this is Visual Acuity. Visual Acuity is the product of contrast ratio and light level. Where a value of ten represents perfect vision in a controlled environment such as a movie theater and a value of one is the equivalent of blindness where objects cannot be identified. So here is a real good picture of what is going on. In order for the rider of a racing motorcycle to prevent mud and debris from building up on his face shield, he has to put on sunglasses at night and look at himself in a mirror while attempting to maneuver a race bike past 20 or so others at death defying speeds.

The SpeedStack7™ Solution

As mentioned earlier, reflection is caused by the speed of light slowing down as it enters a transparent material. When light travels through multiple layers of different materials, and keep the light at the same speed, no new reflections are created. Velocity Tearoffs has created the SpeedStack7™ (U.S. Patent 6,388,813 and 6,536,045) by optically laminating seven layers of tearoffs together. The laminated tearoffs of the SpeedStack7™ displace any air in the Stack. Thus eliminating the reflections between layers. A seven layer SpeedStack7™ has about the same optical characteristics as a single tearoff! SpeedStack7s™ can be layered, giving the rider up to twenty-one or more tearoffs for those long races. This allows the rider to have better visual acuity than ever experienced before from the start of a race to the checkered flag.

Transmission Measurements

In the first bar graph, the light transmission is measured comparing the SpeedStack7™, and a standard 2mil thick tearoff. With only one layer the light transmission of both 2mil tearoff and SpeedStack7™ are the same. As additional layers are added, the standard 2mil tearoffs decrease rapidly to about 50% while the SpeedStack7™ remains almost constant with only about a 10% change in transmission.

Reflection Measurements

In the second bar graph, the reflection is characterized for the SpeedStack7™, and the standard 2mil tearoffs. Again with only one layer the SpeedStack7™ and the standard 2mill tearoff are the same in reflection. As layers are added the reflection increases to over 40% for the standard tearoff, but the SpeedStack7™ remains constantly low in reflection with only a 3% change.

Vision Index

The third bar graph is the Vision Index. It demonstrates the effect of the combination of the transmission values divided by the reflection values. As the reflection on the inside of the face shield increases and reduces contrast ratio, it competes with outside visibility.

Street Applications

We've been pleased with the success of our racing tearoffs the past few years but always felt the application could benefit the average street motorcyclist as well. With that in mind we have created two tearoff systems for street helmet applications. First is our Velocity Street Laminated Tearoff System. This system uses our SpeedStack7™ with our Exclusive Perimeterseel™ Mounting System. This system allows the SpeedStack7™ to be installed on any flat racing shield with no mounting post required. The Perimenterseel™ creates a full seal around the tearoffs that mounts directly onto the helmet shield. The Perimenterseel™ also creates a fully airtight system that allows for riding in the rain with no moisture or dirt allowed to get between the last tearoff and the helmet shield. When the top layer is dirty, simply pull it off to reveal a new clean surface. We have designed the street tearoff to be used only when the motorcycle is stopped. This eliminates the need for taking a hand off the handlebars and prevents the rider from leaving the dirty tearoff on the road. Our other system is the Velocity Helmet Shield Protector. This is a 3 layer, 4 mil thick tearoff. Our SpeedStack7™ is 2 mil thick. The Velocity Helmet Shield Protector is applied on a flat racing shield in the same manner as the Velocity Street Laminated Tearoff System. The difference is the 4 mil thickness allows for the top layer to be cleaned as you would clean your helmet shield. When the top layer becomes too encrusted with bugs and other road grime to clean, simply remove the top layer to reveal a clean, ready to ride tearoff. This system extends the life of your helmet shield while allowing for less frequent tearoff replacement. Both Velocity Street Systems are available to fit most helmet shields currently on the market. Prices and variations are on the attached price sheet.
Distributed By Parts Unlimited. Contact Your Local Motorcycle Dealer.