Because Rubber Wears Out
BUGPACK'S Urethane Components
By Ryan Lee Price
For the several hundred products offered in BUGPACK's line of urethane components, these are the silicone molds into which the injection molding goes and the boxes in which they are kept.
|
What is the first thing you noticed when you pulled apart your suspension? Did the rubber tear away and crumble into a hundred pieces? Are you wondering how long your suspension would have lasted if you had kept driving under these conditions? If you're doing a car with safety and longevity in mind (over Concourse-correct restoration, of course), the only pieces on your VW that should remain rubber are the tires (and even they aren't real rubber anymore) and the windshield wiper blades. Bushings for control arms, strut towers, body mounts, trans mounts, sway bars and shocks should be updated to urethane and BUGPACK's distributors are the places to get them.
Since BUGPACK's inception in 1968, when at the time it only sold approximately 50 products from its catalog, it has been joined by over 20 different companies under the banner Dee Engineering, providing the VW world (as well as a host of different car enthusiast groups) quality products for most any automotive buildup. One of their premiere lines of product is their variety of urethane components, designed, tested and built to replace most all rubber suspension and mounting points in any year VW.
The RIM process is done on a rotating table such as this; it rotates through the oven at the rear of the table. These are the silicone molds (and inserts). In the center of the platform are a few mistakes.
|
We had the chance to visit the BUGPACK facilities in Ontario, Calif., to see how they make the myriad VW parts that have been so popular in not only the performance segment of our hobby but the serious restorers as well.
First off, what exactly is this mysterious urethane? For you technical lot out there, urethane (also referred to as polyurethane with very little difference) is the name given to a class of NCO (isocyanate) terminated resins with cross-linking or chain-extension intermediates called curing agents. Okay, for the rest of us, urethane is a chemically produced synthetic material used to replace the usual rubber parts of a car (in our case, a Volkswagen).
One of the benefits of RIM is that each piece is an exact duplicate of the original mold.
|
Oil, water and weather resistance, ozone and oxidation resistance, and resistance to many chemicals, urethane is the perfect substitute to fight the normally harsh environments most of the car's parts are subjected to. Some types of urethane materials are radiation, fungus and bacteria resistant--in case you ever run over a radio-active bacteria-infected chuck of cheese on the road, you're protected.
Some of urethane's other benefits include: high tensile and tear strength, outstanding abrasion resistance (compared to rubber and plastics), higher load-bearing capacity, higher impact resistance and resilience, excellent retention of properties at both very low and very high temperatures.
These are rear shock tower bushings for Golfs and Jettas, 1985-'98, showing that they not only make products for older VWs, but for the newer ones as well.
|
The process to produce it is decidedly simple. Invented in the '60s, reaction injection molding (RIM) is a process by which two liquid components--a polymer resin blend and a modified disocynate--are mixed together under high pressure and flowed into a mold as a low-viscosity liquid. Once mild heat is applied and the reaction is complete, the mold is split away and the final product is a urethane that takes on the details of the mold cavity with high degrees of accuracy and repeatability.
Some Common FAQs
What is polyurethane?
Polyurethane is a flexible plastic called an elastomer. A scientifically accurate answer is that it is a polymer (a material made up of many repeating chemical units) which has urethane as a repeating unit.
This is an example of the original mold (left), the aluminum piece the mold was cast from and the final product (right). This is a spring plate grommet, which is made of a softer urethane compound for swing axle and IRS applications.
|
What is urethane?
Urethane is a collection of five specific atoms arranged in a very specific way. The atoms are nitrogen, carbon, two oxygens and one hydrogen. This arrangement is created when an isocyanate (a chemical group of atoms with a nitrogen, carbon and oxygen atom) reacts with a hydroxyl (oxygen and hydrogen) group.
What is the difference between polyurethane and urethane?
Usually they refer to the same thing. Very technically, urethane is a specifically arranged group of atoms and polyurethane is a material which contains lots of urethane groups.
What does "durometer hardness" mean?
There is an instrument called a durometer which has a spring-loaded feeler gauge that pushes into the surface of a flexible material like a urethane bushing. It measures the amount of penetration for a given force; this is called the durometer hardness of the material. The A scale durometer (as well as B, C and D) goes from zero to 100. A measurement of 100 means that the feeler did not penetrate the material at all, whereas a measurement of zero means that the material offered no resistance at all. As an example, car tires and running shoe soles tend to be about 75A, inline skating wheels are about 78A to 82A. Though the hardness of BUGPACK's products vary from application to application, some of their softer products range from 52 to 90 A but some are as hard as 60 to 80 D.
Is urethane toxic?
Some of the liquid raw materials that go into making urethane are indeed toxic, and must be handled with caution. However, once the urethane reaction is completed, the solid material is safe to use as intended. Of course, never burn urethane as the fumes are toxic, and the dust created when urethane is sanded can be toxic as well.
Videos
|
© 1998 - 2008
