Say goodbye to shift clunking

June 22, 2006
A propeller hub isolator virtually eliminates noise, vibration, and harshness effects perceived as "shift clunk" when boat pilots shift engines into gear.

Mercury Marine manufactures Flo-Torq IV isolators at its plant in St. Cloud, Fla. The isolators currently serve on production models of supercharged four-cylinder, four-stroke outboard engines up to 200 hp but will eventually be added to four-stroke engines, including six-cylinder models with up to 275 hp.


The noise comes at the instant of shifting because the propeller is lazily turning in the water and the engine's drive gears are spinning at 264 rpm.

The isolator, made by over-molding ring-shaped plastic parts onto eight titanium rods, mounts on a sleeve that mates to the propeller shaft. When the engine shifts into gear it absorbs energy as the titanium rods — fixed within the plastic rings — deform with up to a 15° arc as the ring nearest the drive gears turns faster than its counterpart at the propeller end. Mercury Marine R&D materials engineer Scott Olig says the rods act as springs damping transient vibration and high shock loads.

The ring-shaped parts made from Delrin 150 acetal from Du-Pont Engineering Polymers, Wilmington, Del., also give the titanium rods corrosion isolation from other metal elements of the drive system and protect the drivetrain against damage in the case of a severe propeller impact.

Both parts have molded-in races designed to shear under severe loads, helping prevent the transfer of destructive impact forces to pinion gears, drive gears, or other drivetrain components, explains Olig. After an impact, the boater can easily and quickly install a spare isolator hub.

"DuPont also provided key computer-aided finite-element-analysis assistance," points out Olig. "Their analysis gave us crucial data for designing the molded parts and for simulating the non-linear force deflection curves of their interaction with the titanium rods during operation. "Combining Delrin acetal with titanium rods let us design a part that functions in ways neither the plastic nor metal could alone," says Olig. The Delrin-equipped isolator will be on display at DuPont's

MAKE CONTACT
DuPont Engineering Polymers, (800) 441-0575,
plastics.dupont.com

Sponsored Recommendations

March 31, 2025
Unlike passive products - made of simple carbon springs - the bionic prostheses developed by Revival Bionics are propulsive, equipped with a motor and an artificial Achilles tendon...
March 31, 2025
Electric drives are a key technology for the performance of machines, robots, and power tools. Download this guide for an introduction to high-quality mechatronic drive systems...
March 31, 2025
Discover the world of maxon drive technology: motors, gearheads, sensors, controllers, and accessories. Configure your drive system online, including all relevant product and ...
March 31, 2025
Share current page XSun designs and manufactures a drone that is both energy-independent and can make its own decisions, for fully-automated missions. The company needed reliable...

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!