Gallery

The next step is to produce the pattern drawings. The patterns must be larger than the desired casting due to shrinkage when the molten Aluminum cools.

For the sand casting method, wood patterns are the choice and usually made with Mahogany. Poplar or Birch wood. The patterns are 'split', that is, the pattern is made in two halves. The two patterns are held together by two steel 'locating pins' in order to properly register them on both sides of the 'matchplate'.

Pattern making is an art and a profession in itself. The patterns are held to close dimensions and produced with a "Draft", that is, the sides of the pattern must be tapered, usually about 2 degrees, so that the pattern will "pull" from the sand with the least disturbance to the wet sand mould. The patterns are formed by machining, sawing, filing and sanding. The pattern is coated with sanding sealer, fine sanded and I coat the pattern with floor wax and then polish.

Photo No.1 shows the cylinder pattern. The square block attached is called a 'Core Print' and it forms a square cavity in the sand that will later accept a "Core". More on this later. The dark wood in the photo is Mahogany and the lighter wood is Poplar. This particular pattern is a composite, made of several pieces of wood. The white lines are fillets to prevent sharp edges and allow the pattern to 'pull' nicely from the sand. The fillet materiel can be wax, bathroom caulking compound, J-B Weld or many other products.

The Base (or frame, or crankcase) pattern is nearing completion and I should be able to post a photo of it in a few days.

12/8/2002 The photo above shows the base pattern. This split pattern is made up of 16 separate pieces of wood. and held together with 2 steel dowel pins. The dark wood is Mahogany, the crankcase portion is Birch and the legs are Poplar. The large rectangular section will form the 'core print' in the sand mold. Sanding sealer was applied , fine sanded and 2 coats of floor wax was applied and polished. The overall height of the pattern is 2 7/8". The width is 2". Quite a bit of time and labor was spent to produce this pattern.

A 'Sand Core' is required to be placed in the Sand Mold to form the crankcase cavity in the bottom of the Cylinder and Base. To make the 'Sand Core', a 'Core Box' is required. The Core Box is made using 3" wide Poplar wood. The sides are drilled and brass tubing installed as guides for 5/16" OD drill blanks. The Core Box is then sawn into to form two halves that slide together and apart

A 'Core Pattern' is required to form the inside of the Core Box and it is shown here.

The Core Pattern is, again, a split pattern, aligned with steel dowel pins and all sides tapered 2 degrees. The Core Pattern is placed on a smooth surface and half of the Core Box is placed around it. Repro is mixed and poured into the Core Box. Repro is a two part Polyester epoxy, very similar to J-B Weld. Repro solidifies in less than 9 minutes so the mixing, de-bubbling and pouring must be done quickly.

The box is flipped over and a sheet of Saran wrap is stretched over the Repro and embedded pattern. The second half of the pattern is registered on the first half of the pattern with the dowel pins. The second half of the Core Box is slid down the guide rods and the box is filled with Repro. When completely solidified, the Core Box is telescoped apart and the Core Pattern extracted. One end of each box is then removed to allow access to the cavity. The photos below show the Core Box in the closed and open positions. The "ears" on one box makes it very easy to open or close the box.

12/14/2002

Pattern drawings of the 2 1/2" OD flywheel allow .015" per inch shrinkage of the Silicon Bronze. This is a little more allowance than for Almag Aluminum. I allow .013" per inch for Almag. The first part of the flywheel pattern to be made is the rim. Two blocks of Mahogany are sandwiched together with Double stick tape then drilled and fitted with steel dowel pins. The rim is then turned in the lathe with a 3 degree taper on both sides of the ID and OD. The rim is then coated with sanding sealer and fine sanded. The two hubs are also turned in the lathe.

Four identical curved spokes are required for the wheel pattern. To produce the four spokes, a split pattern of one spoke is required. The split spoke pattern is made using two Aluminum plates, joined together and cut to shape using the mill, files and abrasive paper. The edges of the spokes are tapered 2 degrees and chamfered for easy extraction from the mold. The spokes are finished by buffing with Jewelers rouge and separated. Both halves of the finished Aluminum spoke pattern is shown below.

To make identical copies of the Aluminum spoke, a mold is required. The two Aluminum halves are placed on a temperature controlled plate and a brass ring from the scrap box is placed around them. The ring is filled with liquid rubber and cured at 350 degrees for 15 minutes. The photo below shows the two Aluminum halves before extracting them from the rubber mold.

Both Aluminum halves are extracted and the mold is ready for use. The empty mold is shown in the photo below.

Finally,, with the spoke mold in hand, I am ready to cast some spokes to make up the flywheel pattern.

I decided to cast the spokes with JB-Weld as I can mix small batches and it cures slowly, giving me ample time to work with it. Also I thin the JB-Weld mix with a few drops of Denatured Alcohol to enhance flow characteristics and speed up de-bubbling. At a certain time in the curing process, I can screed the top of the mold to remove excess JB-Weld and obtain a flat mating surface. When completely cured, the spoke halves are easily removed from the rubber mold and have the same mirror finish that the Aluminum pattern has.

12/22/2002

The flywheel rims are formed by mating two blocks of Mahogany with double stick tape then drilling and installing two dowel pins. The rims are then turned out in the lathe. The hubs are produced in a similar manner with one dowel pin. The flywheel pattern, like the previous ones, is a split pattern, and, since everything must have a name, both sides of the flywheel pattern have a name. The upper (or top) half, is the "Cope" half. The bottom (or lower) half is called the "Drag".

The Cope side rim and hub are placed on a flat surface and the Cope side of the four spokes are carefully fixed in place with Cyan acrylic glue. The Cope is then flipped over and a sheet of Saran Wrap is stretched over it. The Dowel pins are installed and the Drag rim and Hub are registered. The Drag Spokes are located on the Cope spokes and glued in place. The two halves are then separated. The spokes are filleted where they meet the rim and hub. JB Weld is used for fillet materiel . After sanding and polishing, the flywheel split pattern is complete, it is composed of 15 individual pieces and shown in the photo below.

It is not economically feasible to cast just one flywheel with each pour of the Bronze, therefore, four identical patterns are required. A box is made from 1" X 3" Poplar then sawn into to yield two boxes about 1.250" deep. Each half of the flywheel pattern is coated with a Silicon release agent and placed on a flat surface with a box around it. Each box is filled with Silicon rubber. The rubber sets quickly so everything must be in place, the mixing, de-bubbling and pouring must done quickly.

The photo above is a close-up of the rubber mold for the Cope side of the flywheel with the wood pattern extracted. At this point, you are probably questioning the cost of the Silicon rubber. I paid $42.00 per gallon with a pint of hardener, $40.00 UPS Ground shipping with a $20.00 surcharge for Hazardous materiel handling. At $100.00 per gallon ---- I don't waste any. More to follow as work progresses.

The MATCHPLATE is a 14" X 24" sheet of plywood, grade A both sides. The plate is painted with Sanding Sealer and sanded for a sealed, hard surface. Two 1/4" holes are drilled through the plate and one half of a flywheel pattern is glued in place with it's dowel pins through the holes. The second half is registered on the dowel pins and glued in place. All sixteen halves are fixed in this manner. The dowel pins are then replaced with wood screws for security.

The photo above shows the DRAG side of the matchplate. A long RUNNER, drafted at 5 degrees, is fixed in place with glue and nails. The GATES, properly drafted, are installed to each pattern.

The photo above shows the COPE side of the matchplate. The RISERS, with their gates, are installed to act as reservoirs for molten Bronze to prevent shrinkage inside the flywheel cavity. The patterns, runner, gates and risers are filleted where they meet the matchplate for easy removal from the sand. Fillet materiel is usually concave strips of wax, applied with a hot steel ball. The fillet materiel can also be window caulk, J-B weld or Spackling compound. A 2" hole is drilled at opposite ends of the matchplate to accept a pair of metal guides that register the matchplate within the moulding frames.

The matchplate is waxed with hard floor wax and buffed. Some pattern makers prefer to spray the matchplate with clear automotive lacquer rather than wax it. Finally, the Matchplate is ready for use.

The frames are telescoped apart and the matchplate removed. A Filter is placed at the bottom of the Sprue. The filter can be Fiberglass or Steel Screen. The frames are then telescoped back together. The frames are then removed from around the sand and the sand mold is ready to receive the molten Bronze. A Gas Furnace is used to melt the Bronze in a Crucible. The molten Bronze, at 2200 degrees, is poured in the Sprue, flows through the Runner and Gates to the flywheel cavities.

The photo above shows the casting as removed from the sand, with the Matchplate in the background. The Steel filter can be seen in the center of the casting. Also, one can see that two of the flywheel patterns were improperly registered. That mistake has now been corrected. Each flywheel casting is sawn off at it's Gate. Before machining, the flashing is removed from the inside of the flywheel with files and abrasive paper. A 1/4" OD stone in a Dremel tool is handy to polish the inside of the flywheel.

1/9/2003 Casting only one Base and Cylinder per pour is not economically feasible. The same procedure to duplicate the Flywheel pattern was used to produce four Base and Cylinder patterns.

The photo above shows the rubber mold made from the wood Cylinder pattern. A rubber mold was also made from the Base pattern.

The photos above show the Base and Cylinder Repro patterns. Four of each was made. These patterns were installed on a Matchplate.

The photo above shows the Drag side of the Matchplate with the runner and gates installed.

The photo above shows the Cope side with the risers installed. The patterns are filleted at the Matchplate, sealed and waxed. The Matchplate is now ready to use.

1/12/2003 The Matchplate for the base and cylinder was placed in the casting frames, packed with moist sand and poured with Almag Aluminum. Finally, after all the work and expense,, a set of castings.

The photo above shows the Cylinder and Base castings after sawing them off from the gates. At this point, I can see that the engine can be built as a water cooled engine with a domed head, or, the water spigots can be removed and fins cut for an air cooled engine with a fined, flat head. It is also apparent that only one flywheel can be used if the engine is to be installed in a Tug boat or other slow moving vehicle where a very reliable, long running engine is desired.

The above photo gives an idea of the future engine. Perhaps I can do a bit of machining and take the castings to Cabin Fever. More after Cabin Fever. Hope to see all you guys there, especially the ones with beer and hot dogs.