Product category:
Springs, dampers, latches, locks and small components
News Release from: Rencol Tolerance Rings | Subject: Mack Trucks
Edited by the Engineeringtalk Editorial
Team on 10 April 2002
Ring holds key to truck diesel pump
protection
The narrowest tolerance ring ever made by Rencol is at the heart of a Bosch diesel fuel supply pump developed for Mack in the USA.
The narrowest tolerance ring ever made by Rencol is at the heart of a Bosch diesel fuel supply pump developed for Mack in the USA Mack is one of North America's largest producers of heavy-duty trucks and since January 2001 part of Volvo Global Trucks
This article was originally published on Engineeringtalk on 18 Aug 2008 at 8.00am (UK)
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Many trucks from Mack travel around 100,000 miles and more a year across America.
Rencol Tolerance Rings has designed a ring which is just 3mm wide and 14mm in diameter.
This annular spring steel fastener is used to assemble the primary pumping gear onto the driveshaft inside the Bosch diesel supply pump.
As well as mounting the gear and transmitting the drive torque its principal function is to provide overload protection to the supply pump's driveshaft and therefore as well to the engine gear train that drives the supply pump.
In normal operation the waves around the ring's circumference provide an efficient interference fit between the 30mm diameter, 14mm wide gear and the 12mm supply pump shaft on which it is mounted.
Whereas tolerance rings are often designed to accommodate repeated overload cycles, the ring in the diesel supply pump is specifically engineered to self-destruct in the event of a serious overload.
Once the load reaches seven times the normal drive torque the ring first allows slippage between the gear wheel and the shaft.
The supply pump speed (around 3600rev/min) then causes the tiny ring to disintegrate so that the supply pump driveshaft can rotate freely.
As the delivery of fuel to the engine reduces, the vehicle slows down and stops safely.
The damage is limited to the fuel supply pump which can be replaced easily without impacting on the much more costly engine assembly. Request a free brochure from Rencol Tolerance Rings ...
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