Minn Kota Parts

Minn Kota Parts

ENGINEERING Plastics AND Motorboatenginesalready gotogether like ducks and water. Because of their corrosionresistance and ever-improving structural capabilities, plasticshave taken the place of metal in components both in and out of themotor compartment. Just consider the newest minnkota fromMercury Marine for a lesson in most that plastics can do. Thecompany's 225 to 275 horsepower, six-cylinder Verado motors, thefirst supercharged four-stroke models with their class, utilize

polymers for their air-intake manifolds, cam covers, motor control unit housings, resonators,plenums that will help reduce powerplant noises during idle, and the majority of in their fuel units.

Three is preferable to One

Maritime powerplant covers long ago went into plastics, mostly single-piece models produced fromsheet molding compound (SMC) or thermoformed sheet. Verado's new powerplant enclosure, bycontrast, contains three injection-molded plastic cowls. The topmost cowl sticks out for the sheersize. Made from a 33-percent glass-filled nylon 66, this part measures 33.5 X 22.9 X 16.4 minn kota65 parts inches and weighs 11.3 lbs. Mercury plastic materials engineer Mitesh Sheth calls it the"largest injection-molded cosmetic nylon part on the planet," claims that DuPont EngineeringPolymers, the material supplier, confirms. A structural rear cowl made from the identical nylonmates with the top cowl along a diagonal split line and attaches with an aluminum structuralmember that joins the powerplant to the boat. A lesser front cowl molded from two items of glass-and mineral-filled DuPont Minlon nylon completes top of the powerplant housing.

A few other molded plastic parts enter in the cowl assembly. A PC/PBT air dam cap, which channelsair to the motor, attaches to the top cowl. And the rear cowl includes a separately molded nylon 66structural rib that Mercury attaches using a urethane adhesive. Finally, the Verado sports a cheapercowl to pay the drive shaft housing. Though it's mostly conventional within its style, Mercuryengineers made a decision to mold this lower cowl from a DuPont Sorlyn ionomer, a type ofthermoplastic noted for its ability to support high-gloss, molded-colored.

The entire assembly might seem somewhat complex initially. After all, marine motor top cowlings

have so far had simple, single-piece shapes. John Zebley, Mercury's director of design, goes up tonow with regards to describe these earlier designs as "inverted trash cans with a seal." Yet usinginjection molded splitting and plastic materials the cowl into pieces worked to Mercury's advantagein a number of ways.

Reducing cost is an important one. Sheth explains how the nylon components can reach a Class Afinish with less paint compared to the SMC parts. "They likewise have fewer defects, like orangepeel, which increases our yields," he said. As well as the lower cowls, with their molded-colored,don't need any paint in any way. Sheth estimates these paint line savings play a role in a roughly 46-percent decline in piece-part costs in comparison with SMC.

Weightloss can be another advantage. Tom Walczak, cowling project engineer, reports thattraditional SMC cowling represents just as much as 20 % of the entire powerplant weight. At 35 lbs,Verado's cowling weighs 30 percent less than SMC. Which savings makes a major difference withinan industry that equates performance with power density.

Some of that weight-loss comes from the thermoplastic's specific gravity advantage versus SMC.Although the style freedom from molded plastics contributed for this score as well. Sheth notes thatplastic parts have relatively thin nominal wall thicknesses whilst the SMC parts might have required"bulked up" regions to mold properly. Along with the injection-molded parts allowed molded-infeatures impossible inside a compression-molded part. Walczak cites the Verado cowling's patentedintegrated latching system--where formerly separate hinge mounting points, cable guides, andbrackets have been molded right into the most notable cowl, as one example. This style, integrationsaves some weight by eliminating bolted-on latches. Additionally, it plays a role in a reduction inassembly costs in addition to the 46 percent savings in the paint line.

The multi-piece nature from the cowl like-wise furthered some important style goals--ones linked topackaging the motor and sprucing up its visual appearance. Make the particular water thepermanent address. Anyone understand that which you want from a trolling motor. Minn Kota is aworkhorse that will dives to the thick involving it along with functions right after ...The Verado'sstraight-six supercharger and configuration together resulted in a tall engine. Zebley says thediagonal split line and overall styling of the cowling combine to "help mask that height." In balancingthis industrial modelobjective against engineering needs, Mercury's engineers and makers workedtogether right away of the project and quite often was required to make some compromises. By wayof example, the engineers planned to leave some clearance inside the powerplant compartment forair flow. In addition they planned to leave some wiggle room to enable relative movement betweenyour powerplant block, on its mounts, plus a cowling that rigidly attaches towards the Verado'saluminum mounting structure. Walczak says that industrial design wound up "tweaking their stylinglines a little bit" to offer engineering very much-needed clearance.

Breaking apart the cowling also solved a traditional draft angle problem. Receiving atall and thin,bucket-shaped cowl out of a mold might have been extremely hard without adequate draft. Even atiny bit of draft will have flared out the foot of the cowl. Which width could have interfered using the26-inch spacing required to put multiple motor with a boat. "Splitting the cowl made the draft anglein the individual parts a smaller amount of an issue," Walczak says.

Finally, the split cowling added an essential ease-of-use feature. As opposed to struggling to lift off aheavy, single-piece cowl from outside the motorboat, boaters may now reach throughout the topcowl, unlatch it, and remove it from inside of the motorboat.

Hard Material

To be able to protect the powerplant, in addition toits role in dressing up the Verado visually, thecowling also offers to try out a structural role.MercuryMaritimedesigns the cowlings to face up todeflection under static loads corresponding to a 200-lb person with size 10 shoes standing in addition tothe engine cover. They actually do," Walczak says,although "People shouldn't be in the boat doing this.Along with the cowling must endure to impact loadson all sides in the outboard--both below and abovethe waterline. One of Mercury's tests involves smashing a quick-moving fake log to the leading edgeof the submerged gearbox, which forces the powerplant to pivot violently from the water. This testmay result in 300G impact loads, which ultimately transfer through the cowling components, inaccordance with Walczak. So, rigorous could this be test that this makes a number of the company'sother impact tests almost a formality. "When the cowling survives the log test, it survives everythingelse we throw at it," says Walczak. Ensuring the cowling did survive called for many modelintervention because the cowling matured. For instance, Sheth and Walczak added a structural ribfor the within the rear cowl to help tie it to the powerplant structure. Mercury glues within the ribemploying a structural urethane adhesive that gives them a joint with a lap shear strength of morethan 500 psi. Molding inside the rib will not have worked in such a case as the rib's stiffness couldhave interfered with all the unique ejection system utilized to get this horseshoe shaped part from itsmold--a proprietary "floating island" design from CDM Tool & Manufacturing Company. "The cowlneeds to flex from the tool allowing ejection from your mold," Sheth says.

The Right Material

A good understanding of material properties also helped the parts fulfill the structural needs insidethe face of environmental and thermal factors that frequently reduce plastics' working mechanicalproperties. Sheth was required to account for a variety of these factors in selecting the correctmaterial to do the job: The cowling parts experience temperatures around 230F as well as contactwith UV light, salt water,snow and rain, and chemicals starting from fuel to suntan lotion. Thedemand for a Class A surface further complicated the choice. "Glass-filled nylon 66 was the veryleast costly material which had been both structural enough and aesthetic enough." Sheth says.

But even picking the right nylon wasn't straightforward considering the conditions when the cowlsoperate. Mercury engineers performed extensive finite-element-analysis work with the cowl usingANSYS software, before deciding on a material. And that work told Sheth that he or shehttp://www.animatedknots.com/indexfishing.php needed a material with a flexural modulus of aminimum of 700 kpsi. That figure does fall well inside the capabilities of reinforced nylon 66. Inreality, the grade that Mercury uses has flexural modulus of roughly 1,300 kpsi. Yet Sheth'sknowledge of plastic materials told him that this material wouldn't perform anywhere near that wellwithin the field. "We needed something with 700 kpsi after comprising the impact ofmoisture andheat, and chemicals," according to him. "And that's not something which FEA can tell you." It tookextensive material testing to tell him what he did have to know--that the 1,300-kpsi grade underconsideration would have a flex mod even closer 800 kpsi inside the engine's actual operatingconditions. "Which had been still adequate for our own application," he states.

Sheth also put quite a lot of effort into controlling and predicting glass fiber orientation in the cowlparts. Orientation obviously matters for structural reasons, but it really additionally influencesshrinkage and warpage which could have hurt the fit of your cowl components. "The shrink on thetop and bottom needed to be the identical," Sheth says. In case the fibers go through the resinsurface, What's more, the location of the fibers in accordance with the top of the part can hamperthe opportunity to get Class A surface--.

In the style stage, DuPont performed a mold-filling analysis to find out the way the fibers lined upfrom the part under different gating scenarios and molding conditions. At a later time, he workedwith experts from Mercury's molder, Bemis Manufacturing Inc., and from DuPont to fine-tune themolding conditions and techniques influencing fiber orientation. They decided, as an example, tomold the very best cowl inside a sequentially valve-gated tool, which assists manage fiber orientationby controlling filling patterns.

Keeping Noiseless

Another important role for that Verado's cowling involved its contribution to reducedvibration andnoise, and harshness (NVH). Not every the engine's hushed sound is dependant on the cowling. "Alot of things have been done correctly to produce this engine quiet," says Tim Reid, director of motorstyle for Mercury R & D. He cites a shorter list for the Verado that includes improved gear qualitywithin the drive train, a highly-tuned air intake system, the plenum that tunes the idle exhaust, and aresonator that cancels out a few of the rotor noise in the supercharger.

But the cowling undeniably helped quiet things down and offset several of the noise added throughthe supercharger. "Before designing the cowling, noise measurements obtained from early engineprototypes gave us some concern," Walczak recalls. "Initial noise measurements in the uncowledVerado arrived in more than the noise measurements of a lot of our uncowled competitors."

Yet the design crew didn't just be happy with a noisy powerplant. Walczak reports which they putextra effort into optimizing the atmosphere intake system, like the geometry in the air dam on thetop cowl as well as the intake-manifold passages. Noise considerations also informed the fabricselection process. Sheth states that he sifted through dynamic mechanical analysis data and askedfor sound transmission tests on the panel samples before selecting the information for that cowlings.Their efforts have paid off. "We feel we currently hold the quietest engine in the class," saysWalczak.

RELATED Document: As Well As The WINNER IS ...

Mercury's cowling model for your Verado took homea pair of design awards in the 2004 Structural Plasticmaterials Conference. Its top cowl won theConference Award for the most innovative entrywithin the conference's model competition. As wellas the cowl assembly won the People's Choice Awardsponsored by the Industrial Designers Society ofPlastics and America News. To learn more aboutStructural