Development of a sandcasting process for an Atlantic Marine Engine

Development of a Sandcasting Process for an Atlantic Marine Engine

Kyle Joba-Woodruff

Submitted to the

Department of Mechanical Engineering

in Partial Fulfillment of the Requirements for the Degree of

Bachelor of Science in Mechanical Engineering at the

Massachusetts Institute of Technology

June 2017

C 2017 Massachusetts Institute of Technology. All rights reserved.

Signature redacted

Department of Mechanical Engineering May 23, 2017

Signature redacted

Certified by:

Daniel Braunstein Senior Lecturer

Signature redacted

Accepted by:

Rohit Karnik MASSACHUSETTS INSTITUTE

OF TECHNOLOGY

JUL 2

5

2017

Associate Professor of Mechanical Engineering Undergraduate Officer %Ij J

Development of a Sandcasting Process for an Atlantic Marine Engine

by

Kyle Joba-Woodruff

Submitted to the Department of Mechanical Engineering on May 23, 2017 in Partial Fulfillment of the

Requirements for the Degree of

Bachelor of Science in Mechanical Engineering

ABSTRACT

The Atlantic Marine Engine, designed and manufactured by Lunenburg Foundry of Lunenburg, Nova Scotia, is a historically significant gasoline marine engine from the beginning of the 20'h century. The Atlantic and other similar engines transformed the American and Canadian fishing industries with their power and reliability. A project to recreate a historic J model, single cylinder, two-cycle "make and break" engine is ongoing at MIT's Pappalardo Laboratory by a number of students. This thesis will focus on making progress towards a completed engine with the design and fabrication of the engine base. The fabrication will continue to use a traditional sandcasting process, but will explore the viability of using computer-aided design and manufacturing (CAD/CAM) processes to make high quality patterns out of high-density polyurethane foam.

Thesis Supervisor: Daniel Braunstein Title: Senior Lecturer

Acknowledgements

The author would like to thank the following individuals for their support: Peter Kinley, Lunenburg Foundry

Nick Treadwell, Lunenburg Foundry

Mike Tarkanian, MIT Department of Materials Science Foundry Shaymus Hudson, MIT Department of Materials Science Foundry James Hunter, MIT Department of Materials Science Foundry Daniel Braunstein, MIT Pappalardo Lab

Bill Cormier, MIT Pappalardo Lab James Dudley, MIT Pappalardo Lab Steve Habarek, MIT Pappalardo Lab Tasker Smith, MIT Pappalardo Lab

Table of Contents

Abstract 3

Acknowledgements 4

Table of Contents 5

List of Figures 6

1. A Brief History of the Atlantic Engine 8

1.1 Precedents 9

1.2 Prior Work 9

2. The Atlantic Engine Base 10

2.1 Making a Modern Model 12

3. The Mold Making Process 15

3.1 The CAD-CAM Process 17

3.1.1 Design 17 3.1.2 Manufacturing 17 3.2 Lower Base 19 3.3 Upper Base 21 3.4.1 Patterns 21 3.4.2 Cores 23

3.4 Post Machining and Finishing 24

3.5 Mounting and Flasks 24

4. Process Verification with the Manifold Test Part 24

4.1 Sand Casting Process 24

4.2 Casting Results 24

5. Conclusions and Next Steps 26

List of Figures Figure 1-1: Figure 1-2: Figure 1-3: Figure 2-1: Figure 2-2: Figure 2-3: Figure 2-4: Figure 2-5: Figure 2-6: Figure 3-1: Figure 3-2: Figure 3-3: Figure 3-4: Figure 3-5: Figure 3-6: Figure 3-7: Figure 3-8: Figure 3-9: Figure 3-10: Figure 3-11: Figure 3-12: Figure 3-13: Figure 4-1: Figure 4-2: Figure 4-3:

Cutaway Atlantic engine

Atlantic model J engineering drawing Results of piston casting process One-piece base

Diagram of base kinematics

Engineering drawing of one-piece base Engineering drawing of split base Assembly of the 3D modeled split base

Assembly of the split base, cylinder, crankshaft, and connecting rod Manifold pattern half

Manifold core mold half

CAM simulations of machining a pattern Lower base pattern (bottom half) CAD model Machined lower base (bottom half) pattern Lower base pattern (top half) CAD model Machined lower base (top half) pattern Upper base CAD model showing parting line CAD models of upper base patterns

Assembled foam upper base patterns Core mold creation diagram

Finished upper base core molds Mounting manifold pattern in a flask Sand cores placed inside a sand mold Cast manifold, showing surface finish Cast manifold, showing surface failure

8 9 10 11 12 13 13 14 14 15 16 18 19 19 20 20 21 22 22 23 23 24 24 25 25

1. A Brief History of Marine Engines and the Lunenburg Foundry Atlantic Engine

The turn of the 2 0 h brought the power of gasoline to the marine industry, completely reshaping it

in the short span of a few decades. The 2-cycle, single cylinder engine was the engine that brought this wave of power. The success of the 2-cycle was its inherently simple design, manufacturability, and reliability. Each stroke brilliantly prepares the next stroke, eliminating the need for a valve system.

Thousands of companies sprung up to manufacture these marine engines, but the Lunenburg Foundry is the only company of the original explosion of companies that manufactured two cycle engines that still exists today. They have since moved on to other products -the last Atlantic engine was made in the 1990s, brought back by special request using original wood patterns. [1]

Figure 1-1: Cutaway display Atlantic engine at the Atlantic Fisheries Museum. The cutaways

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Figure 1-2: Engineering drawings of an Atlantic 4.5" x 4.5" J model engine showing the cylinder, piston, one part base and bearing flange, flywheel, hand hole cover, and exhaust and intake manifold [2]

1.1 Precedents

Rebuilding a J model of the Lunenburg Foundry Atlantic Marine Engine has been a multi-team project by several students in the Department of Mechanical Engineering, with prior work done on other systems of the engine. In the spring of 2016, Josh Born and Jarrod Smith built the ignition and cooling system, and machined the crankshaft. Also in the spring of 2016, Samantha Castellanos cast the piston, Meaghan Fitzgerald cast the connecting rod, and Eric Kline made a wooden pattern for the flywheel. An old stock carburetor was donated by the Lunenburg Foundry. The only three remaining major components are the cylinder, exhaust and intake manifold, and the base. This thesis will focus on the construction of the base, an integral part of the engine body which houses the crankshaft, facilitates the flow of intake and exhaust gases, and serves as a mounting point for the engine to a vessel.

1.2 Prior Methods

In the manufacturing process of this engine in the early 20th century, patterns were hand-carved of wood by a skilled pattern-maker. Given the loose tolerances expected of sandcast iron parts, woodcarving is a practical way to make patterns, but has two shortcomings: it requires specific skill and experience, and it is time intensive with complex geometry. Contemporary CAD design and CNC machining provides an opportunity for the quick, easy, and accurate production of patterns.

The pattern making and casting work done by Samantha Castellanos serves as a precedent useful in forming a process for the manufacture of the base. The work done by Samantha involved a traditional

casting process, but focused on innovating a pattern making process using FDM printing in ABS. FDM printing provided rapid pattern and core mold creation, but the low quality surface finish required additional surface preparation processes to yield satisfactory results.

Figure 1-3: From left to right: 3D printed piston pattern, coated and sanded with plaster; cast iron piston, exterior view; cast iron piston, interior view of bore. [31

This work will explore the merits of using high-density polyurethane foam and 3-axis CNC milling as a pattern and core making method. One set of patterns for the exhaust and intake manifold was machined in the fall of 2016 by Daniel Braunstein, to great preliminary success; this work will focus on developing the process further and refining it to a consistent procedure. The Atlantic engine base will be the focus of the design and this work, and the manifold will serve as a simpler test part to evaluate new processes.

2. The Atlantic Engine Base

The Atlantic engine base serves several key roles in this design of 2-cycle engine. First, with the large rectangular flange, it provides a rigid mounting base for the engine to the bottom of a boat. The second role the base serves is in the combustion cycle: during the intake cycle, the base pulls in fresh gas and air from the carburetor which is expanded as the piston rises. With combustion, the piston drives the crankshaft, expelling the fresh fuel mixture through the cylinder to above the piston where it will be compressed and combusted with the next stroke. The base is designed to house these gases with two main parameters in consideration: first, the fresh fuel mixture is not at high pressure so sealing is not crucial. Second, the volume of the base is sufficient enough for the crankshaft and connecting rod to move, but otherwise minimizes volume to improve compression [1]. The last function of the base is the bearing support of the crankshaft upon poured in Magnolia babbitt bearings.

The Atlantic base was originally designed as one main piece, with a small flange attaching vertically. This design required inconvenient assembly and disassembly of the crankshaft and flywheel to replace the babbitt on the crankshaft bearings. In the 1930's, the base was redesigned to split horizontally so that assembly and disassembly became much more convenient. The new design allowed the base to be split and the crankshaft removed easily, allowing access to the bearings with reduced risk of damage to the crankshaft and connected components, which was a serious problem with the original base design [1].

Figure 2-1: Original Atlantic engine one-piece base. Casting date unknown, on loan from the Lunenburg Foundry.

The Atlantic bases featured a boss for a petcock to be mounted; theoretically for draining a gas-flooded engine. However, because the magnolia crankshaft bearings did not often provide a watertight seal on the crankshaft and base, fisherman found the petcock useful for draining fully water flooded engines, which occurred when the bilge overfilled during wet weather [1].

A peculiar feature common to both the one-piece and split base is the flat bottom section of the lower base. It would seem to be counterintuitive to have any geometry other than circular for a part housing rotating shaft arms. There was no explanation in literature available, but through the process of modeling the base and creating assemblies for verification, it became apparent the purpose of the flattened bottom. The arms of the crankshaft rotate around the center of the base, but the connecting rod does not. The clamping tabs and bolts at the base of the connecting rod where it attaches to the crankshaft do not rotate around the axis of the crankshaft, they are offset and rotate along a slightly eccentric path. Relative to the fixed engine, the connecting rod does not rotate in a complete orbit, it follows the linear stroke of the piston and the orbit of the end of the crankshaft arm. A sketch of the kinematics illustrates this, and shows the resulting geometry required to contain this assembly, which is in fact a circle with a flattened side.

Figure 2-2: Assembly of the engine base with crankshaft and connecting rod. The path of the

crankshaft arm is in red and the paths of the connecting rod and tabs are in green. The tabs require more horizontal clearance than the crankshaft arm, but less vertical clearance, and so the base is shortened in height.

2.1 Making a Modern Model

Information for this engine is largely taken from historic engineering drawings, circa 1929. Most drawings are based around a single reference sketch of the Atlantic engine series, with parameterized dimensions for the various models of the engine design, the G, J, K, R, and E. Using a CAD program, Solidworks, 3D parametric models were created from the engineering drawings. Key dimensions were taken from the drawing tables, but many dimensions were missing and had to be estimated from drawings and from measurements of an existing one-piece base.

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Figure 2-3: Engineering drawing of J model 'one-piece' base. Though this was not the type of base that this work focuses on, it was used in the modeling of the split base, however, as a reference for several dimensions and geometric features that were ambiguous in the split base drawing. [2] rAOr)r MIS P-04.1i 4. to 44 .LOWCA RASC. ANAWIM& #0. 171.

LP-N-Figure 2-4: Split base engineering drawing. Note that the G and J engines lack the large port 'E' located on the upper base. [2]

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Figure 2-5: CAD assembly of the basic split base geometry. The upper opening allows for movement of the connecting rod and flow of fuel gases. The front opening is for the hand hole cover, which allows access to the connecting rod attachment hardware.

Figure 2-6: Assemblies of the models were used to verify geometry by looking for correct alignment of the crankshaft and the piston with intake and exhaust ports through a full engine cycle.

3. The Mold-Making Process: Taking Parts to Patterns and Cores

Once an accurate model of the engine base was completed, it was translated through several levels of positive and negative abstraction into useful patterns and core molds. For positive bodies, patterns were used to create negative space in the sand, and for cavities inside the bodies, positive sand cores were made from molds.

The first step in translating from a part model to patterns and cores is the selection of a parting line; the ideal parting line choice is one which simplifies the entire process but preserves complete accuracy. A suitable parting line avoids undercuts, minimizes pattern machining complexity, and reduces the size of flask and amount of sand required. Generally, parts that have a large flat surface are parted along that surface, while parts without are parted along planes of symmetry.

Figure 3-1: Manifold pattern half; the parting was chosen along the vertical plane of symmetry of this part. There are three prints: at left through the exhaust flange cap, at bottom through the intake port, and at right through the exhaust port.

After a parting line is selected, the external geometry of the model is split across the parting plane, making one or two solid bodies which will form the basic geometry of the patterns. Next, cores are created, and from these positive cores a mold system. By using a boolean CAD feature, positive cores can be created from the cavities inside the model. These positive core models lack attachment features, so it is necessary to create core prints. Core prints are placed where support is needed, and where ports in the model are available. For example, in the manifold, the large exhaust port is useful for a print because of

its large size and its placement next to the bulk of the body of the core. However, not all core prints have ideal locations, and so they can be fragile and require reinforcement, as in the case of the prints for the water jacket core on the manifold.

Figure 3-2: Manifold core mold; note the large prints on the left and right side available for supporting the central exhaust core. In comparison, the upper core, for water cooling, limited base for a strong print connection, so it would have to be reinforced using wire.

Once core positives and necessary prints are complete, core prints are added to the patterns in corresponding locations. These prints on the patterns leave negative spaces in the sand upon which the cores rest. Next, core molds are made; this requires selection of a parting line with the same criteria as the main parting line. Using a boolean CAD feature, the positive cores and prints are used to create cavities in a solid block; this block is then split along the parting line to form two mold halves. A final CAD assembly ensures the mating of all components and reduces the potential for errors to appear later in the process.

This process is both iterative and flexible; for a complex part, the best process generally comes from ideating several solutions and combining the best features of each. Referencing traditional casting work of others is valuable, as the sand casting process is a craft that benefits from artfulness and experience.

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3.1 The CAD-CAM Process

3.1.1 Design

After pattern and core schemes were chosen and designed on paper, part CAD models can be manipulated into patterns and cores. Core molds are then made from the core models. Boolean and splitting features are useful in the reconfiguring process. Considering material cost and machine run time, many parts were split into smaller sections to more efficiently use foam stock and cutting time. After these parts are created, there are three steps of operations that must be completed. First, the model must be scaled to account for shrinkage of the cast part upon cooling. Empirically, a shrinkage of 1% was measured and averaged from several other cast parts. Casting of the manifold verified this further. Once the model is scaled, it is convenient to then make further modifications such as adding core prints with round, unscaled dimensions. Scaling from the centroid of the model, as opposed to an origin, gives a close match to the dynamics of the scaling that occurs with shrinkage.

A draft angle of 2 degrees was tested in the patterns and core molds of the manifold and proved to be sufficient for easy release from sand. For simplicity and consistency, 2 degree drafts were used throughout on all vertical surfaces. To make drafts, some extruded features can be reconfigured to include a draft, while more difficult features such as revolved or swept features require careful cuts to produce a specific draft.

Finally, after scaling and drafting, fillets can be added. Fillets are practical to add after scaling because they can be dimensioned with thought to exact tool sizes. Fillets on the cast parts do not need to be accurate and scaled for shrinkage, for they serve only a rough smoothing purpose, and are not involved in alignment of components. Referencing images of historic parts and available tools, three fillet sizes were used consistently. The available 3/8" ball end mill featured a long shoulder and good general compromise of speed and detail, so nearly all interior fillets were made to a radius of 3/16" to accommodate this tool. For small exterior corner such as those in cavities, fillets of 1/16" radius were used to lightly round edges. For large exterior fillets on heavy bosses, 1/8" radius fillets were used.

3.1.2 Manufacturing

The machining material used was a high density polyurethane foam, approximately 15 lb/cubic ft. density. Through the machining of more than a dozen parts it proved to possess the ability to hold excellent surface finish, adequate stiffness when being cut, and extremely high machinability. The machine used was a Prototrak 3-axis CNC mill. Stock foam blocks were mounted on sheets of marine plywood, which has very good flatness tolerance. Wood screws, carefully located, provided adequate force to hold large pieces of stock, and with smaller pieces, small dabs of CA adhesive provided semi-permanent mounting. The plywood with stock was then clamped directly onto the mill bed. High cutting speeds and tool feed rates were used, and with the low mass and high relative stiffness of the foam and plywood, high frequency vibration was an issue initially with clamping directly in a small vice. Clamping directly to the bed reduced vibration and significantly increased quality and finish tolerance.

A library of high-speed steel flat and ball end mills, diameter 1/8" to 3/4" were used, with a 3/4" flat being most useful for facing and rapid clearing operations, a 3/4" ball end mill being useful for 3D roughing operations, and a 3/8" ball end mill being excellent at nearly all finishing operations. A tool feed rate of 150 in/min and spindle speed of 4000 RPM (the upper machine limits) was used at all times, and satisfactorily matched the machinability of the foam. Cutting depths of up to 1 tool diameter were used with good success.

The CAM program used was HSMworks, an integrated Solidworks CAM package. The typical tool operations used were as follows:

1. Facing - a large diameter flat end mill was used (3/4").

2. Pocket Clearing - for rough removal of the majority of stock with a large diameter flat end mill (3/4"). Stock left on horizontal and vertical surfaces was typically set to 0.10"

thick.

3. Contour - for efficient removal of stock on steep faces with slopes greater than 60 degrees with a large diameter ball end mill (3/4"). Stepdowns of 3/16" struck a good balance between speed and finish.

4. Parallel - for efficient removal of stock on shallow surfaces less than 60 degrees in slope with a large diameter ball end mill (3/4"). Stepovers of 3/16" struck a good balance between speed and finish.

5. Pencil/Scallop - for finishing, these operations provided intelligent toolpaths that blend parallel and contour movements for efficient and consisted stock removal with a medium diameter ball end mill (3/8"). A stepover of 0.07" provided a good final balance between speed and finish, though stepovers between 0.12" and 0.04" were tried. With hand sanding providing an excellent finish, smaller stepovers provided no significant advantage.

6. Contour - a final contour was used to trim the final small layer of stock left around the boundary at the base of the part, typically with a 1/2" diameter flat end mill.

Figure 3-3: Toolpath (left) and stock (right) simulation of operations performed on an upper base pattern to verify complete machining and absence of collision errors.

Tool operations groups were stored as templates, and could easily be reapplied to new parts to save programming time. Different part geometries suited different operation types and settings, and the basic templates were tuned to each part to reduce machine time and increase finish quality.

With the large flat area of the base mounting boss, a natural choice for parting line was on the upper base mating surface, requiring one lower positive pattern and one upper negative pattern in place of a core. However, this presented an undercut which would make pattern removal impossible. The first of two other possibilities was to place the parting line along the vertical plane of symmetry, but this would require two patterns and a detached core with prints. The second solution was to modify the horizontal parting line, lowering it to the surface of the base mounting boss. The only modification required was to make a shallow positive feature on the upper negative pattern, so this process was selected for its simplicity.

Figure 3-4: CAD of lower base pattern, reoriented upside down for ease of view.

Figure 3-5: Machined lower base pattern, reoriented upside down for ease of view.

The positive lower pattern was machined in one piece. The upper negative pattern was decomposed into three pieces to efficiently use material. The main cavity was machined in a 13"x15.5"

block. A lip was made to allow for a 1/2" thick sheet of marine plywood to extend the surface of the pattern and the mounting surface was laser cut from 3/8" thick acrylic sheet. The use of flat stock reduced machine time and waste material. Additionally, this surface is later required to be machine finished, an extra 0.125" was added to the model with the acrylic sheet. The vertical walls and the ends of the crankshaft housing were drafted to 2 degrees. An assembly of the two patterns was made and examined in section to verify the accuracy of the cast component.

Figure 3-6: CAD assembly of the upper pattern, which features a pocket to form the cavity of the lower base, and a thin laser cut boss to form the mounting boss for the upper base to connect to the lower base.

Figure 3-7: Machined foam piece of the upper pattern, with lip for the plywood plate to rest upon.

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The upper base presented less flexibility than the lower base. The flanged upper mounting surface overhangs the rest of the upper base and creates numerous challenges. Not only would a horizontal parting line make release impossible because of undercutting under the flange, it would also be impossible to machine underneath the flange on a 3-axis mill with standard straight end mills. The only feasible parting line is on the vertical plane of symmetry, creating a casting situation with two tall patterns standing vertical on their longest dimension in the flask. The one-piece J base also used this strategy, as is evident from the edge left from casting which show the parting line. By splitting the pattern and orienting it vertically, it also made machining under the flange possible with a 3-axis mill.

Figure 3-8: Upper base CAD model showing the parting line used. This parting line maximized access when machining and ease of removal from sand.

3.3.1 Patterns

Pattern design had to involve foresight to supports for core prints, as this process required separate cores. Core prints were required to support cores through the cylinder opening, hand hole opening, base opening, and shaft bearing ends. These pattern had a central, relatively cubic section, and a wide flat section. It was required to machine the patterns on their side to access underneath the cylinder flange, however this would place the shaft bearing and lower flange delicately upright, blocking tool access to the lower regions of the pattern. The patterns were then split into two sections, separating the lower shaft and flange from the main base body. This allowed each part to be machined in a more ideal orientation and with reduced stock. After, these two parts were glued back together using CA adhesive.

a.

b.

Figure 3-9: a: Combined central pieces of the upper base patterns. They were split along the central parting line and machined with the parting surface down to allow tool access to machine the underside of the upper flange. b: Horizontally machined inserts for the upper base pattern. This machining strategy saved material and machining time. These pieces were machined separately and split along the central parting line, perpendicular to the axis of the crankshaft bearing housing.

Figure 3-10: Assembled foam pattern. The holes on the shaft bearing flange are from mounting and will be filled.

3.3.2 Cores and Mold

It was sensible to divide the cores in the same ways as the patterns, as they have similar geometric features. The main body of the base core was made into a cavity inside a solid block. The cores for the shaft bearings are simply half cylinders, so the molds were made out of a PVC pipe split in half. Prints were added through the cylinder opening, lower base opening, hand hole cover, and shaft bearing ends, all 1" in length. The patterns were then modified to accommodate the core prints. All vertical surfaces were drafted, and finish surfaces were extended by 0.125" to allow for finish machining of the cast part.

Figure 3-11: The method for creating core molds involves subtracting the mock core models from a block, splitting it.

Figure 3-12: Finished upper base core molds. They were machined out of one piece of stock for efficiency of set-up, and cut into separate pieces after. The semicircular bosses at the bottom of the molds will create cavities for the crankshaft cores to connect.

- - .~-.~---. - -- I

3.4 Post-machining and Finishing

Though surface finish of parts off of the mill was high quality, it was still necessary to perform trimming and sanding to ensure smooth release of sand, especially from steep surfaces and tight geometry. To test, an early manifold pattern was sanded to a fine finish and half coated with natural shellac; the other half was left uncoated. The uncoated pattern released consistently better than the coated pattern, and because of its process simplicity was applied to all of the patterns and core molds. A quick schedule of hand sanding from grits 220 to 400 to 600 produced a smooth surface with relative ease. The evenly spaced ridges left by the finish pencil or scallop operations provided a consistent base for easy

sanding.

3.5 Mounting and Flasks

Two pattern molds require specific mounting for alignment. Because both the upper and lower halves of the flask, the cope and drag, respectively, have detail in sand, these details need to be aligned such that when the flask is closed the parts come together to form a continuous body. To accommodate for these large parts, a custom wood flask will be made with halves of dimensions 18" x 22" x 7".

Figure 3-13: Manifold pattern mounted on a board, placed in the bottom of a flask in preparation for packing sand. All surfaces are coated with talcum (baby) powder to aid release.

4. Process Verification with the Manifold Test Part

The exhaust and intake manifold, with patterns and cores designed by Mechanical Engineering student Moseley Andrews, was used as a small scale test part for verification of the foam pattern process.

4.1 Sand Casting Process

Once patterns are mounted and core molds assembled, the traditional sand casting process begins. Resin bonded sand was used with success for the delicate manifold cores, to provide strength and a finer surface finish. Resin bonded sand was also used on the surface of the patterns, for finish, but the bulk of the patterns were packed with greensand. After flasks were packed, runners were cut for iron flow and entry, a riser for pouring was placed, and vents holes were made to allow the molten iron to off-gas. Approximately 150% of the estimate weight of the manifold was melted to allow for enough surplus to sit in the riser and provide hydrostatic pressure to fill the mold during pouring.

Figure 4-1: Manifold cores placed inside the packed drag of a flask. The cores are made with a high strength, fine grain resin bonded sand, and the surface of the drag mold is as well, with the bulk of the drag filled with greensand. Note the smooth integration of the core prints into the matching prints left by the pattern.

4.2 Casting Results -Success of Foam, Conclusions, and Next Steps

The first casting of the manifold in iron proved to be a huge initial success, though it was in fact a failed casting. The surface finish created by the resin-bonded sand packed on foam was excellent quality on the exterior of the manifold and in the interior cavities. The casting failed due to a leaky core print seal, a fault which occurred in the assembly of the sand molds. This error is not a fault of the foam and can be easily corrected.

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Figure 4-2: Manifold first casting, note the flash which highlights the parting tine. The surface finish was excellent, and the feature were measured to have good accuracy.

Figure 4-3: Failed manifold first casting. A core print was not properly sealed and leaked, allowing iron to flood the hollow core and prevent complete fill to the upper surface. This is a

simple failure of mold assembly that can be easily corrected.

5. Conclusions and Next Steps

A complete set of patterns and core molds were fabricated, and will be used to make sand molds for casting a base for the Atlantic marine engine. The design and fabrication of the patterns and core molds for the base demonstrated the viability and success of this new process; in particular, high-density polyurethane foam shows fantastic promise as a pattern material, with clear advantages in machinability, relative cost, and quality of finish. The finish quality that can be easily achieved is a huge advantage of the material and the process compared with 3D printing. The computer-aided design and manufacturing process allows rapid and flexible design of models, patterns, and core molds, with high quality. The next steps of this project will be to gain experience in the casting process by recasting the manifold until a successful part is complete. After a sandcasting procedure is established, the base and remaining parts will be cast and machined, eventually creating a reborn, working Atlantic marine engine.

6. References

[1] Grayson, Stan,1982, Old Marine Engines. International Marine Publishing Company, Camden Maine [2] Young, Charles and Young, Daniel, 1929, Atlantic One-Lunger Engineering Drawings. Lunenburg Foundry & Engineering Limited, Lunenburg, Nova Scotia.

[3] Castellanos, Samantha, 2016, "Casting a one-lunger Atlantic marine engine" S.B. thesis, Department of Mechanical Engineering, Massachusettts Institute of Technology.