Quality Made in Canada Shooting Star Technology


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Shooting Star Technology is happy to provide this brief report for those who were unable to attend P.R.I.M.E. in person.

This report is not meant to be comprehensive and show every engine and model at P.R.I.M.E. Instead, it is intended to give an overview of the show, with a few representative engines. Some even have sound files. I hope this report will whet the model appetite enough to draw you down to the show next year. What this report can't show you is all the fun and comraderie people have when they get together to discuss their hobby with others, and to share ideas. At any one time at the show you can see several groups of two or three people sketching out plans on scraps of paper or waving hands in the air to show shapes and mechanism arrangements. It is truly a fun time.

The sound files have proven to be popular. I must appologize to the steam enthusiasts. The steam engines are, in general, so quiet that I had a tough time getting quality sounds recorded. I'll work on this for next year. I thank everyone who let me feature their models and tooling in this report. Also thanks to Joe Lawton for the interesting casting demonstrations.

Lee R. always drew a crowd when he fired up his V8 . (sounds) . Nostalgic folks loved it when Lee ran his Model A . (sounds) When folks wanted a higher RPM engine, Lee ran his DOHC engine . (sounds) . He points out that he uses all manual equipment to build his engines- no CNC.

Hit-n-Miss engine lovers will appreciate Harold B.'s engine . (sounds) .

Randall C. showed a lot of talent with his self-designed Harley look-alike . (sounds) . Randall built his own pressure aluminum die casting machine that produced this professional-looking part. It has valve guides, seats, and a cast iron cylinder sleeve cast in place. He modestly declined to show any photos of his casting machine, saying it had 'evolved' through many steps to get to its present state, and looked a little rough. You're always your own worst critic, and I think the beautiful castings demonstrate that his reticence is unjustified.

Up from the Bay Area, Ken H. brought this 4 cylinder Wall Engine . (sounds). Ken also brought his cam grinding machine he built from plans in Strictly IC magazine. He put on a micrometer adjust with a roller follower, then had to add a flat follower anyways because his master profiles were intended for a flat tappet, not a roller tappet. Another grinding machine was displayed (whose owner I regrettably didn't record) along with a very nice looking cast iron crank.

Some engines are constantly under improvement. Jim M's little jewel (sounds) is no exception, sporting a new radiator. Notice the piston,spark plug, con rod, and valve in Jim's hand. Jim also displayed the tooling used to make the rad out of sheet brass and tubes.

Jeff M. showed off this horizontally opposed steam engine. . (sounds)

An incredible example of a "Harris's Steam Roller" . (sounds) was shown by John B.

Ronald S. brought this very Victorian-looking steam engine . (sounds)

Bob H brought several engines with him. One was this Challenger V-8 . (sounds). Another IC engine of Bob's is this familiar-sounding . Volkswagen engine. In the steam category, there were several examples of the Corliss engine. Here is Bob's Corliss engine . (sounds)

Even models of the same type have their own unique sounds. Compare this Corliss . (sounds) built by Dario M. with Bob H's, above. It may be that they're just running at different pressures - or maybe the valving is adjusted differently.

This nicely finished steam launch engine . (sounds) was displayed by Hal M.

Bob Shore sells plans and casting kits. Two of his engines are the Silver Angel and the Silver Bullet . The Bullet sports a hand-crank start. Bob's engines were all running, but unfortunately my video camera was damaged just previously to visiting Bob's booth, so I can offer no sound files of his engines. Bob also had a circus-type multipipe organ playing, with the tune being generated from a continuous loop paper tape, like a player piano.

This Stuart Turner steam engine was built by Mike H. Another steam engine was displayed by George D. (sorry, no sound files)

Steven M's display featured a Panther Pup on a stand complete with a drawer full of spare part samples.

Marlyn Hadley made this oval nut and bolt with both external and internal threads. Maybe not useful, but a pretty good head scratcher!

These tiny CO2 motors were on display. The airplane flys, but did not at this show due to all the people in the way. This is a radial CO2 engine. . Believe it or not this is a complete 4 channel radio receiver and two servos! These tiny airplanes are not really scale models of larger planes: the key goal is to make it small and lightweight. (I'll leave it to the purists to argue whether this "belongs" at PRIME- I vote yes) The servos use an ingenious mechanism to make the parts compact. A motor drives the screw of a multiturn trim potentiometer. The pot not only provides electrical position feedback for the servo circuit, but provides the motion by using its screw as a leadscrew in a linear drive. I was also shown a dual axis proportional servo that was even tinier. It used voice coils as a operation principle.

Sand Casting Demonstrated at P.R.I.M.E.

Most people would not try casting metal without prior instruction. Although there are many books out there intended for the beginner, books can only take you so far. The next step is to find someone who is already doing casting and just watch and listen. Fortunately, PRIME is the place to watch and listen to Joe Lawton of Springfield, Oregon. Joe gave sand casting demonstrations several times per day thoughout the weekend of PRIME. He is a real personable fellow, and gave a running commentary on all aspects of sand casting. Everyone who watched his demonstrations came away a little richer in knowledge.

The basic idea of the sand casting process is to (1) make a mold out of sand, and (2) pour metal into it and let it cool. From this basic start, some very spohistcated items can be made. I suppose it would be possible to carve out a cavity in packed sand with a spoon to make your mold, but this is not the usual way to do it. A much better way is to make a pattern the same shape as you want the metal part to be. You press sand in around the pattern (or "ram it up" as it is known in casting parlance). This way you can use the same pattern over and over to make multiple, and importantly, identical sand molds.

There are several considerations to take into account when you make your pattern. Different metals shrink different amounts as they solidify and cool, so in general, you wouldn't use the same pattern for aluminum and cast iron if you were real concerned about the final part dimensions. Another factor in pattern making is the section thickness- too thin and the metal will cool too much as it flows through, and may not flow through the whole mold before it starts to solidify. Joe has taken care of these details so we'll continue.

The pattern is sawn in half, and half is rammed up into each half of the rectangular frame, which is called a flask. Usually, the pattern is mounted to a match plate on each side and is keyed to the flask so the pattern halves line up when the match plate is removed. Joe has found that match plates are often not required, and he just puts index pins right into the pattern halves without a match plate. One less thing to missalign, after all. Also, its a lot easier to store patterns without match plates. Joe sets the pattern half onto a base, and sets the flask around it loosely. A powder parting agent is sprinkled onto the pattern and base plate. It is inside the bag and sprinkles out through the fabric when the bag is flexed. Joe used ordinary flour for many years until he was informed by an expert at a commercial foundry that flour would not work as a parting agent. One of Joe's customers then bought a large sack of "proper" parting agent for use on his patterns. Joe estimates that at his present rate of consumption, he has enough to last about 200 years.

The next step is to cover the pattern and base plate with uniform sand. The way to do this is to press it through a screen to break up the lumps. If the sand had lumps (or small rocks, or metal chunks from a previous use), the sand would not reproduce the detail of the pattern.

Once the fine sand is covering the pattern and base plate, you can get a bit rougher and scoop in more sand and ram it up. The sand has motor oil mixed in so that when squeezed, it holds its shape. Also, the sand is mechanically produced so it has sharp corners which help it bond together. Note that beach sand has its corners eroded off, and does not work well for sand casting. (not knowing any better, I've tried it) Joe uses a commercially available sand called Petrobond.

Let the sand hump up above the edge of the flask, then strike it off with a sawing motion with a flat board or piece of metal.

Flip over the flask and and you'll see the exposed pattern. Install the index pins, and place the other half of the pattern in place. Sprinkle the parting agent over the pattern, and ram up the sand again in the other side of the flask. Now you're using the first mold you made as a base instead of the base plate you used before.

You have now produced a sand mold (but of course, the pattern is still inside). You need a place to pour the metal into so Joe uses a tube to core out a hole in the sand. Make sure you push it in at least as far as the parting line of the sand halves. You can use a spoon to flare the hole. This serves to both act as a resevoir for metal as the metal below it solidifies, and to act as a funnel so you can hit the hole (called a sprue) with the molten metal when you pour it in. Cut another hole (a riser) at the othe end of the pattern to allow the metal to flow throught the pattern and push the air out, and to let you know when the mold is full.

Flip over top of the flask and pull out the patterns. See why the pattern is in halves now? Joe puts a couple screws into the exposed side of the pattern to use as handles, and also serve as a place to tap the pattern in the cardinal directions to loosen it from the sand and let him lift it out.

Now is the time to cut the runners that lead the metal from the sprue (where you pour it in) to the mold cavity, and from the mold cavity to the riser (where the excess metal rises after it flows through the cavity). Also, now you can carefully remove any bits of sand that has fallen into the mold cavity.

This pattern has a core. Cores are used to reduce machining time later, and to prevent sink holes that occur when large sections of metal shrink when they solidify. Basically, cores are used where you want a hole in your casting . It is sometimes possible to arrange a pattern to cast a hole without using a core, but in parts with holes in different planes, it is not possible. The core is made beforehand in a mold of its own using a mixture of sodium silicate (waterglass) and silica sand. It is solidified by passing carbon dioxide through it. There are other ways of making cores as well but they all involve ways of making sand stick together, but not so well that it can't be removed later: a core made of concrete would not be much good! The cores are made of sand so they can be chipped out of the cavity they produce after the part is cast.

With the core in place, and the two pieces of pattern removed, the two halves of the mold are put together. The crucible with the molten aluminum is removed from the furnace . After the dross (oxidized layer) is skimmed off, the mold is poured. It is crucial that the metal is poured into the mold in one smooth motion, with no hesitations. If it is not poured evenly, it is almost certain to not fill the mold properly. The part is let to cool for about 20 minutes before the sand is knocked off the part. The really scorched sand that was right against the aluminum is thrown away, but the rest can be put back into the bin to be reused.

A Complex Pattern

Now that we've seen the basics of casting with a core, lets look at a more complex example. Joe Lawton teamed up with Eugene C. to give this one-off demo on Sunday afternoon. By looking at his work, you'd think Eugene was a pattern maker by trade, but his V-8 casting project is a hobby, and his pattern making skills are entirely self-taught! Eugene has made a complete set of patterns for a 1/4 scale Chevy V-8. For the demonstration, he came prepared to cast an aluminum intake manifold. I say 'came prepared' because significant work was required to build the multiple cores and assemble them into a complete unit. I neglected to photograph all the core molds, but here is the finished core. To me, the cores looked nothing like any intake manifold I've seen, until I realized that I had never seen the INSIDE of a manifold before - the air and water passages. Notice how complex the cores are. The air intake runners cross over without touching. The pattern for the top of the mold is shown here. This pattern is used to form (in sand) the cavity which sits down over the cores. The aluminum fills the space formed by this cavity, and is excluded from the air and water passages by the cores.

Here is the intake manifold (upside down) after the sand mold is partially removed. In this view, the sprue and riser extend downwards. The scorched sand is kept seperate from rest when the part is cleaned. Here Joe is sawing off the runners. The cores will be removed by poking and chipping at them with screwdriver or something similar.

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