Weeping hub seals are a real nuisance. And if my experience is any indication, you're just as likely to find leaking seals on new trucks as on trucks in service for several hundred thousand miles. It just goes to show that installing and setting wheel seals and bearings requires skill. Careful handling of the seals and then precise setting of the hub bearings to minimum runout is a requirement.
Industry standards set by The Maintenance Council of the American Trucking Associations (ATA) says wheel bearing clearance should be 5/1000 of an inch or less. But even this small amount of runout is not as good as a slight bearing preload. The problem is you can't easily measure the preload.
July 23, 2011
July 22, 2011
Heavy-duty Fuel Efficiency Regs on the Horizon
In case you missed it, the heavy-duty fuel efficiency regulation that the Environmental Protection Agency and the National Highway Traffic Safety Administration announced jointly last October goes into effect in 2014. This set of mpg rules for medium and heavy trucks was crafted in response to President Bush’s 2007 Energy Independence and Security Act and the Obama Administration’s call for greenhouse gas emissions reduction technologies for commercial vehicles.
Never mind that commercial considerations provide a major incentive for engine and truck manufacturers to deliver the best fuel economy at the most affordable price. It’s yet another example of how regulators and lawmakers are out of touch with the real world. The danger is that fuel economy mandates will bring unintended consequences – like additional costs for technology that don’t pay back over the life of the truck.
Never mind that commercial considerations provide a major incentive for engine and truck manufacturers to deliver the best fuel economy at the most affordable price. It’s yet another example of how regulators and lawmakers are out of touch with the real world. The danger is that fuel economy mandates will bring unintended consequences – like additional costs for technology that don’t pay back over the life of the truck.
July 18, 2011
The Why of Variable-speed Fan Drives
A great innovation that is only slowly catching on in North America is the variable-speed cooling fan drive. As innovative as it is, it surprises me that it isn’t being adopted more readily. Today, 85% of drives are still on/off drives instead of the newer two- or three-speed, or ECM-controlled variable-speed viscous drives.
Given the benefits of the new technology, I think anyone specifying machinery that requires a fan and cooling system would benefit from the variable-speed drive. It’s kinder to the drive belts, results in less thermal cycling of the engine, is generally a lot quieter, drags less dirt and other contaminants into the radiator, and is, in the case of the truck driver, kinder to the operator.
Given the benefits of the new technology, I think anyone specifying machinery that requires a fan and cooling system would benefit from the variable-speed drive. It’s kinder to the drive belts, results in less thermal cycling of the engine, is generally a lot quieter, drags less dirt and other contaminants into the radiator, and is, in the case of the truck driver, kinder to the operator.
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