Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/307497
30 Vol.3 No.5 / May 2014 UNDER THE COWL are a novice, don't just paint it yourself; modern two- and three-part systems may require professional intervention." Comparing apples to apples, Rémi Beringer, chief engi- neer at Beringer Wheels & Brakes, noted that, in aluminum, "the breaking load of a cast wheel could be 25 kpsi; 61 kpsi for machined. Machining has a higher cost than casting but can be worth it." Matco mfg, which provides parts to a myriad of original equipment manufacturer (OEM) kit builders and a large portion of LSA manufacturers, said that its products speak for themselves. With a wide range of master cylinders, wheels, and brakes in many sizes and capacities, the Matco line, backed up by its information-rich website, continues to dominate its segments. Robbie Grove of Grove Aircraft Landing Gear Systems Inc. makes both tubeless and tube-type wheels and said, "Tubeless tires can lose a pound of pressure a day; corrosion is always a problem." On lightweight airplanes, slightly low pressure in tires usually results only in sloppy handling, but that's not good when everything else is against you. But on heavier air- planes, where the tire's rating is closer to the actual load, even extended taxiing can fail an underinflated tire. Typical modular designs add options for sizing; precision machining and nonporous material encourage tubeless ap- plications, saving weight. Goodyear notes that both tubeless and tube-type tires can lose a pound a day from normal infla- tion and remain within spec. But that does not mean that your air pressure is in spec; check it every day. Cheaper tubes, especially non-aircraft tubes, can lose a lot of pressure quickly. Though they may be lighter and are almost always less expensive, resist the temptation. Use the right components. BE A RINGS Robbie Grove said, "The nose wheel has about twice the [side stress] requirement as the mains; we use tapered roller bearings in nose wheels." Rémi Beringer countered, "Due to its conical configuration, the tapered roller bearing pre- stresses the wheel and the axle; the ball bearing does not create an axial load when we apply a vertical load on it." And George Happ, president of Matco mfg, noted that the axle tension required when using tapered rollers contributes only a miniscule amount to rolling resistance. There is less disagreement about sealed versus open-race bearings: The big advantage of sealed bearings is that sealed ball bearings don't need periodic repacking, as do open ball or roller bearings, and their seals are more resistant to the entry of water. Though sealed bearings, in fact, cannot be re- packed, that has not been a problem for most users. Beringer (which uses sealed bearings exclusively) noted that it has never sold a replacement bearing. That does not mean that Beringer never will, but it speaks well of the sealed design, popular across wheel manufacturers. When well-protected and where fl exibility is not critical, clear brake lines can save ounces. For fast-landing or heavy airplanes, or an aircraft with tundra tires, one caliper may not be enough. Photography courtesy of Tim Kern E A A E X P _ M a y 1 4 . i n d d 3 0 EAAEXP_May14.indd 30 5 / 5 / 1 4 3 : 1 9 P M 5/5/14 3:19 PM