March 8, 2011

Shop Talk: Disc Brakes

Everywhere we go, folks have a lot of questions about the mechanics behind our trikes. This month, we are happy to bring you the first of a series of guest blogs from our mechanic extraordinaire, Bill Murdock. Bill is the man behind our machines, and is something of a superhero to the B-Line team, especially when he comes to rescue our broken down trikes mid-route in the pouring rain. And now, over to Bill, on brakes....

Although the electric-assist motor gets most of the attention, there is another critical component of our trikes that is often overlooked: the brakes. Without a brake system capable of heroic levels of deceleration in all conditions we would surely commit random acts of property destruction and personal injury. Luckily our vehicles are equipped with powerful hydraulic disc brakes that are able to bring the trike to a screeching halt.

There are five parts to a disc brake system:

  • rotor: the disc itself, in our case 230mm in diameter and 4mm thick. These are the only custom component in our system, as they are of a proprietary design. They are CNC water-jet cut from 410 stainless steel, Blanchard-ground to within 0.0005 parallelism, with chamfered 5mm cross-drilling. 400-series stainless offers a good compromise of heat dissipation, machinaility, low-cost, and is highly corrosion-resistant.
  • caliper: the part that acts on the rotor, composed of one or more slave cylinders. Our calipers are made by AP Racing, a premium aftermarket outfitter based in Great Britain. They are machined from high quality aluminum castings, have twin opposed 25mm aluminum pistons, radial mounting, and a hard anodized surface treatment.
  • pads: the friction material that contacts the rotor. We use an AP organic compound, a better match for the rotor material than a sintered metallic pad, giving long pad life and excellent modulation.
  • master cylinder: the brake lever and fluid reservoir. Our trikes use an Italian-made, aluminum Grimeca master with a 14mm piston operating all four slaves with DOT 3 hydraulic fluid, giving a very firm lever feel with maximum power.
  • lines: the hose that links each component. Typically fiber-reinforced rubber hose, we use heavy-duty clear-coated, teflon-lined, braided stainless steel hoses made by Goodridge. These offer a substantial improvement over standard rubber in terms of rigidity and service life.

With a brake system like this, every ounce of our 800-pound capacity can be easily tamed, not to mention the nearly 750lbs of vehicle weight plus rider weight. Heroic indeed...

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1140 SE 7th Ave, Ste. 190, Portland, OR 97214
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