As you may have noticed from some of my other pages I have sampled a number of the unique books that Lindsay Books, Inc. offers. One of those that I purchased was Simple Electrical Working Models: How to Make and Use Them. There are many interesting projects in this book; however, the one that captured my imagination was the electric beam engine. This model appears to be an electro-magnetic version of the beam steam engines that were common at the turn of the century.
The following page documents my attempt to produce a version of this model. The design that I ended up using closely follows the details provided in the book; however, I tried for a greater level of refinement than the book called for. An example of the refinements that I included was the flywheel. In the book the flywheel is cut from wood and encased in a coffee can tin. Brass tacks are used to balance the roughly made flywheel. I decided to cast the flywheel in aluminum and true it up on a small lathe.
I began working on the beam engine today. I started by making a pattern for the flywheel. I rough cut out a piece of basswood about 4 1/2 inches square. Using a forstner bit in the drill press I planed the piece down to a 1/2 inch thick. Using a compass I drew a 4" diameter circle and cut it out. I drilled a 3/4" hole into the center and glued a small piece of dowel to function as an arbor. I sanded this piece and used wood putty to repair all surface defects. I bored a 1/4" axle and inserted a dowel in this. Using this dowel I mounted the piece into the drill press and turned the piece concentric. After additional finishing the final pattern is shown below.
I made my first attempt at casting the flywheel using the pattern that I had previously created. The casting didn't turn out very well. It could probably have been trued up, except for the failure to form a suitable arbor. This is clear in the image below.
I made another attempt to cast the flywheel. While the result wasn't perfect it is suitable to be machined into a good flywheel. The casting with the sprue and riser removed is shown below.
I started today by creating the yoke and poles for the horseshoe magnet. I used 3/8" mild steel rod for the poles and 1/4" x 1" mild steel bar stock for the yoke. I drilled and tapped the rod to accept 8-32 machine screw and drilled the yoke to allow for the poles to be secured to it. I also drilled the yoke to allow it to be screwed to the base. The resulting magnet core is shown in the left picture below. The middle picture shows two spools that I manufactured to serve as coil forms.
The next thing I did was to start cutting the parts to form the base for the engine. I cut these parts from a 3/8" thick piece of birds eye maple that I purchased from Woodcraft. These parts are dry fit in the right most photo below. I decided to use maple for the wood. I haven't decided yet how I will finish this.
I received a Taig Micro Lathe today. I used this to clean up the flywheel, drill the center axis, and to tap it for the linkage pin. I had to go out of town so I wasn't able to finish cleaning up the flywheel.
I finished machining the flywheel. A picture of the finished flywheel is shown below. After machining the flywheel I finished assembling the base. I cut the slot in the top and rear for the flywheel. I mitered the sides and rear. The top was glued together, along with supporting pieces under the centerline of the flywheel and where the uprights will be secured. I secured the base to the top assembly with #6-5/8 flathead brass wood screws. These were countersunk to allow the base to sit flush. After this assembly the entire base was sanded with 100, 150, and 220 grit sand paper. Using the sand paper the edges were relieved slightly. The assembled base is shown in the photo below.
Now that I have a lathe I decided to replace the coil forms that I had previously made. My first thought was to turn them from dowel stock that I had on hand. I made several attempts at this but ultimately gave up because the thin ends kept breaking. My next thought was to turn the forms from a solid rod of aluminum. I didn't have any 1 1/4" aluminum round stock so I rammed up a 1 1/4" dowel in a bucket with some moulding sand and poured aluminum into the mold. I ended up with two rough rounds that I trued up on the lathe. These ended up being about 1 1/8" in diameter. I machined one coil form from the rod. It fit the steel core; however, I am unhappy with how they turned out. They are too bulky and I don't think that they leave enough room for the wire--I cut the inner part to 1/2" diameter. I am thinking that I can take some brass stock; 3/8" thin wall tube and some 1/32" sheet and turn and solder the forms from these.
I picked up some brass from the hardware store at lunch and used it to machine brass spools. The first turned out great and is shown in the photo below. The second was mangled on the lathe. The brass tubing is very thin and I was taking too heavy a cut.
I made another spool using the same material as yesterday. This time I cut the disk much closer to size before placing it on the arbor and turning it to size. This cut the time to make the disk to only a few minutes, rather than the hour it took me yesterday. The image below shows the two spools that I have made. They still need some polishing to clean up the discoloration from the silver soldering.
After making the second spool I created a pattern for the upright support. It is also shown in the photo below. I made the pattern from 1/4" poplar stock. After allowing the glue to dry I sanded the piece and applied the first coat of primer. It still needs one or two more coats and then a coat of wax to keep it from sticking to the form.
I finished winding the coils. A picture of the procedures that I used for the winding is shown above I also cast the first of the uprights for the engine. A description of the procedure that I used can be found here. A photo of the finished product is shown below.
In addition to the above I also cut the pieces for a electromagnet. Since the inside diameter of the brass tubing is 0.032" smaller than the steel rod I need to turn it down a tad. While I was at it I cut another piece for the yoke as well. I will turn threads on the end of the rods and tap the yoke instead of using the screws I had been planning on. I placed all three pieces in the furnace and brought them to a red heat and allowed them to cool in the ashes overnight. This should anneal them and prevent them from becoming permanently magnatized by the coils. I took some commercial 1/2" aluminum rod and have begun turning the two binding posts for the electrical connection. Finally I put two coats of MinWax Antique Maple Gel Stain on the base to begin the finishing process.
I finished machining the binding posts for the motor. They turned out fairly well. A picture of the posts is shown below. The two-piece posts are about one-inch tall with the widest parts about one-half inch in diameter and the thinner parts about three-eights inch in diameter. These pieces will be used to connect the motor to a source of electrical power.
Last night I poured the first half of a silicon rubber mold of the repaired upright pattern. My thought is to make a wax original and cast the part again. If it doesn't match the previous one very well I can always make another wax master and cast a third piece. I cast the second half of the mold this evening. The silicone rubber takes about twenty-four hours to cure so I should be able to take some photos of the mold tommorro night.
Well the silicon rubber mold of the upright cured. The mold had some defects caused by air bubbles; however, I don't think that they will interfere with the final casting--they can be removed in finishing. I tried to pour two wax masters. The first didn't fill the mold. The second was removed a little to early and craked. Even though the casting didn't work it is clear that I can get useful masters with this mold. Now I just have to produce some lost-wax castings in aluminum. On a more successful note I managed to machine the first of the poles for the horseshoe magnet. It cleaned up nicely and I was able to produce a 1/4-20 threading on the bottom 1/4-inch of the piece. It fits the wire spoool, though it is a tad looser than I would have liked. It was snug when I tested it; however, I think it shrunk a little when it cooled.
I finished the second pole of the electromagnet. It mounted to the yoke and fit very well. The photos below show the magnetic core as well as the finished electro-magnet. I tried several more wax castings of the upright. None of them came out right. I poured one more before bed. I'm going to let the wax set in the mold for a couple of days and see if that improves the product.
Letting the wax harden in the mold for a couple of days appears to have helped tremendously. I attached a wax sprue to the pattern and placed it into a tube form and covered with my homemade investment plaster. Photos of the first couple of stages are shown below.
In addition to the wax master of the upright I made a wax master of my beam pattern. They came out fine with only a few surface defects. I used my plaster/pumice investment and baked them in a home made burnout oven for about eight hours. The burn-out oven consisted of a small electric hotplate, a stainless steel camping plate and an inverted clay pot. This procedure worked well. The mold poured with out any problems and the investment withstood the heat very well. It actually was a little tough to remove. That was the good news. The bad news is that the beam pattern deformed slightly when the investment was poured in the mold and was unusable because of this (other than that it was a great piece). To date I have destroyed about six uprights while trying to machine them. Attempts continue and I will post more.
Progress on the beam engine has slowed; however, I did spend some time this weekend finishing the base and beginning to attach the parts to the base. I stained the base using an antique maple stain and sealed it with three coats of varnish. A photo of the engine as it currently stands is shown below.
I tried another lost wax casting of the beam and again the thin sections of the beam were bent. I gave up on casting the beam and machined it from a solid piece of 6061-T6 aluminum 5/8" square by 6" long. The resulting beam is shown in the photo below.
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by Walter Anderson
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