Anzani Fan Type 1/4 scale model

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Jul 9, 2008
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In this thread I will present a short description of my construction of a 1/4 scale model of the Anzani Fan Type engine of 1909 with images of the build process. I will also provide the working drawings.

Several years ago my neighbor was moving away and I happened to see a Benchmaster mill in the back of his garage. I had never seen such a cute little machine before and decided on the spot that I had to have it. We dragged it up to my house and I was started on the path to being a home shop machinist. Eventually I acquired a 9" Southbend lathe and then a 10" Logan and some used tooling from various swap meets. My first engine project was the Crusader 60 engine from an article by George Genevaro in the Home Shop Machnist magazine from 2005.

After getting the Crusader 60 running I was ready to attack a more ambitious project and I began researching the Anzani Fan type engine on the internet. I found drawings in the Encyclopedia Britannica from 1919 and spent a year or so doing research on the web and developing my drawings from the Brittanica drawing. I first used a tool called scan2cad to convert the image to a dxf file. This needed a lot of hand work to get rid of excessive vectors generated by noise in the raster image. Eventually I turned to Draftsight to trace the Britania drawings. Over time I produced about a dozen pages of drawings of individual parts with 1/4 scale imperial dimensions. I found other cleaner and finer resolution versions of the same drawing in other sources to improve my drawings.

I found a lot of images on the web. One site had photos of all the engine parts and I first thought I might scale these. I found that scaling from photos is more like freehand drawing than drafting. Plus, the images were distorted for some reason so nothing round looked round. Still these images have good information. Other sites had photos people had taken in museums. I contacted everyone I could and they were usually very helpful. One guy in particular, Carl Gootzen, of Antwerp Belgium has actually worked on one of these engines at the Stampe Museum where he volunteers. Carl visited the Paris Air and Space Museum to get more information for me. Another guy in England sent me photos and sketches of the compression release mechanism, the carburetor and the intake valve assembly. I found a guy who wrote a book about finding one of these engines hanging with the harnesses in an old barn in France and he helped with the exhaust tappet dimensions. All together I accumulated about 750 files in a gigabyte of data. Once I learned the name of the carburetor manufacturer, I found the US patent for the carburetor and also drawings and descriptions in some old books.

From the dates on my emails and files I see that I acquired the first web data in June, 2008 and made the first machine cut in November, 2010. At that time, even though the drawings weren't completed, I thought that if I didn't actually buy some material and start cutting, I would never build this engine.

I started work on the engine with the cylinders because they seemed to be the biggest challenge. They have fine fins, integral heads and an angled exhaust port. I thought that if I could make them, the rest of the work would be straight forward. So, I began by roughing out the exterior shape from a bar of 12l14 steel. It was good that I had lots of material since it took seven tries to get the three roughed out cylinders.

The lower portion of the cylinder and the bore were turned on the lathe in a conventional manner. My experience with the Genevro Crusader 60 informed me about useful fixtures to hold the cylinder in the lathe and mill setups. As you will see I made several tools, including a 1/2-40 tap for the exhaust tappet guide. The exhaust port was bored with a D-bit of the correct diameter and the exterior shape of the cylinder was formed by stepping around with a single point tool moving vertically at each step. I wrote a simple program to calculate offsets to step around the circumference of the cylinder shape. The tool cutter radius was set to provide the proper exterior shape for the concave curves.





The combustion chamber was formed and the heads were made to be silver soldered in place later. The heads were held in an aluminum fixture and the exterior top profile turned in the lathe. The opening for the intake valve cage was threaded 1/2"-40 in the lathe and the boss around it and the center access plug was formed.

On the cylinder, the little boss around the exhaust valve guide was formed in the lathe with a throughly disgusting tool that was ground for clearance as the flange rotated around it. This boss centers and retains the exhaust valve spring.

Finally, a fly-cutter was made of the proper thickness to cut the spaces between the fins and the fins were cut by stepping around the cylinders. This cutter was very thin and fortunately I only broke one while cutting the three cylinders. The 12l14 is excellent material for this kind of work and now this began to look like a cylinder.




Thanks Steve.

I neglected to include an image of the prototype from the Paris Air and Space Museum.
With the fins cut and the heads finished, except their fins, the next step was the inlet valve cages. These are simple tubes threaded 1/2"-40 on the OD to screw into the head. They are drilled and reamed for the valve stem and counterbored on each side with a form tool. Inlet passages were drilled with the cage held in a fixture in the Benchmaster.



A set of locknuts were made to lock the cages to the head and coupling nuts to eventually hold the flared ends of the inlet tubes from the carburetor manifold plenum fabricated. The coupling nuts were made in two parts, the nut itself and an endplate that was bored to the OD of the inlet tube and then silver brazed onto the nut. The inlet tube will have a flanged silver brazed on its end and this with the nut will be like a squared off flared fitting.



The short exhaust ports were turned on the lathe to make a tube with a flange on its end. The flanges were drilled and shaped by a little hand filing. These are a press fit into the cylinders.

The cylinder heads have a little boss on the combustion chamber side, about .020" thick to register into the combustion chamber to position them correctly. The heads were clamped onto the cylinders and the fins are cut into the uppermost part of the cylinder and the head above that. It was important to measure the fin spacing carefully and the juncture of the head and cylinder as that is where the silver braze joint will be. The fins were cleaned up and given a little taper on their edges with needle file work. Except for the brazing, work on the cylinders is finished.

Oh yes, the bosses for the hold down studs at the cylinder flanges were made separately and brazed in place and I took a beauty shot of the three units.



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I didn't take any pictures of the head brazing operation so I'll try to describe it.

The number of fins and their size was carefully copied from the prototype drawings and fortunately the joint between the cylinder and head came to be in a relieved area between two fins. After the final fins were cut with the head clamped in place a narrow band was left around the combustion chamber on the cylinder and a matching narrow band on the head. I needed to get the silver braze to bond those two.

I thought to use a paste silver brazing material that combines flux and alloy filler and simply apply the heat. I've seen Atlas rocket engines made from tubes bonded this way in a furnace when I worked at Rocketdyne years ago. I wonder how they regulated the paste application to make this work?

Anyway, I proceeded with the paste method and when it cooled it was clearly not sealed completely. Maybe I did not use enough paste, or clamped the parts too tightly. I did make prick punch marks around the joint to provide a small gap for the silver braze filler. I changed my method to use thin silver shim stock cut to the shape of the joint and that worked better.

Later, after the engine was assembled and spun in a jig in the lathe I found it was blowing out the head joint in each cylinder. I re-brazed these again and eventually got rid of all these leaks except one. This one was so bad I had to resort to applying filler on the outside down the space between the fins to get a seal.

I wonder now if it might have been better to have not made this space so deep at the joint and to have done all the brazing from the outside and perhaps recut the space again to cleanup excess filler.
The crankcase parts are the front, back and timing gear cover. I made some drawings to determine where the cutter path would be for the external shape of the case halves and again I wrote a simple program to determine the step offsets for the milling operation. Since this is a round part I only needed offsets for one quadrant. I used a step offset of .005" in the X direction and calculated the Z distance at each step. I made a fixture to hold the case and rotated the case to cut the circumference between each set of through bolt bosses. Since the Benchmaster does not have a quill there was going to be a lot of cranking going on.

The first machining steps were to drill and bore all the holes in the crankcase parts - the through bolt holes, the crankshaft hole and the cam shaft axle holes. Then I cut the internal bore in the front and back cases. The junction of the cases has a small register ring and slot to ensure they fit together properly and the fixture has corresponding features.


M. Anzani originally made motorcycle engines and this is just like one. The cases, crank and fork and blade rods are pretty much like an HD with no oil pump.

After the outside shape is finished the cylinder decks were cut and holes bored for the cylinder skirts.


The outside of the front case has four bosses to strengthen the central crankshaft boss and the material was removed from the front face to leave these. I remember that this was kind of free hand milling and caused me some concern.


The back case half and the fixture plate were moved to the rotary table and the timing case carefully roughed out inside and out in the favorite .005" steps. All this looks pretty crude in the photos but it is coming together with very few mistakes, thankfully.
Work continued on the rotary table to define the tappet guide bosses and other features.

The timing gear cover was made in the same way although I don't have any pictures to show it.


I made a 1/2-40 tap to thread the tappet guide holes and centered these on the rotary table to carve the bosses around them. I made some toolmakers buttons to bolt onto various holes to keep from cutting away too much of the boss and to help keep them circular.



The crankcase work took from the end of June until the beginning of October in 2012 and was followed by work with the Dremel, files and emery cloth until the end of November when the last tool marks seem to have disappeared.


Once again I couldn't resist taking a picture. Thanks to members here for their inspiration and example to help me make these parts.

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The fork and blade rods are even now found in motorcycle engines just as in 1909. The rods big ends are all slightly different in shape and I marked them out and roughed them out to the lines on the mill. As usual I made a fixture to hold them. The little end was drilled and fit onto a dowel and the big ends seated against another and then drilled and bored.


I only have photos of the outer rod with the big end that spans the other two. As you see, some holes were drilled through to establish the shape and provide fillets in the corners and the big end roughed out. The round shapes for the each end were done in the lathe. I think I scrapped the first attempt at this outer rod because it looked a little awkward and too spindly. Even though I traced the original drawings I seem to have had a hard time making these rods so they would all fit in the case and rotate properly. Once it was all assembled with the pistons and cylinders I still needed to relieve a little bit of the case.





The crank wheels were turned from 1018 CR and relieved and drilled just as in the prototype to provide counterweights on each side just as the drawings show.


The mainshaft was turned as one long part with the center section that fits in the wheels slightly scored in a thread like pattern to accommodate the silver brazing during assembly. There is a taper and keyway on the front end of the crank to fit the propeller hub.


The rod journal was made from drill rod. The rod journal is to be brazed into one wheel and locked into the other with a tapered pin held in place by a set screw. I made a delicate little tapered reamer for this from drill rod. For the final assembly I locked the set screw tightly to get the tapered section tight and locked another set screw behind the first.

For brazing I turned three spacer rods of the proper diameter to make sure the wheels were evenly spaced apart and added some clamping fixtures. I don't think I left the machinists clamps in place while brazing. After brazing it didn't look very good and needed some cleanup in the corners to remove the silver braze material. Eventually I got it clean and cut out the center section of the main shaft and the ends of the rod journal. I was satisfied with the runout, although now I can't say what it was.

After the assembly was all clean and shiny I couldn't resist sandblasting the relieved area to give it a little more prototypical look.



I have two crusty old 8" chucks that came with a 9" Southbend lathe and this crankshaft cleanup was the only time I have dared to use them even on the 10" Logan. How could anyone go to the trouble to make a backplate to use these on a small 9 or 10 inch lathe?

The next step was to make the timing gears. A friend had loaned me a complete set of Strictly I.C magazines and I read them thoroughly and scanned what I thought were the most important articles. One of these was an article by Pat Loop in the August/September 1994 issue that described a method of simulating the gear hobbing process. The cutter is made in the lathe that looks kind of like a tap with cutting teeth spaced at the proper pitch and with the included angle to match the gear tooth angle. This is kind of like a real gear hob but without an angle. A series of teeth are cut one at a time in the gear blank at a distance apart and depth corresponding to the diametral pitch of the gear. It's kind of like a single point cutter but the tool cuts a little bit of the tooth before and after the one the cutter is centered on. This is meant to simulate how a rack would intersect the gear.

In use the cutter makes several passes over the gear blank. First with the cutter set exactly on the center line of the gear to be cut. Then subsequent passes are made after adjusting the tool height up and down and rotating the gear a little.

The cutter approximates the path of a rack as it might pass over the gear. You only need to make three passes over the gear to get a reasonable approximation of the involute shape. You need to look it up.

Given the method I now needed an indexing head to rotate the gear. I made a simple indexer using a 50:1 gear reducer from a small Bodine motor drive. At first this was fitted with the usual index plates and a hand crank but being a computer guy I put together a stepper motor drive and connected this to the tape drive port on a MAC Classic and wrote a simple program to control it.



The actual gear cutting was the simplest part of this project and I've used the indexer for other things since then. When the gears were all cut I made a jig to hold them and rotated them in the lath with some grinding paste to lap them in. I seem to recall taking some care to get the holes in the crankcase at the proper center distance.


I don't recall how I shaped the cams but it appears from the photo that they were eventually parted off.


I made a couple of attempts at the ignition plate that holds the three sets of points. First fabricating one by silver brazing the point mounts. This was not accurate and I next made the plate with the point mounts in one piece on the mill. The points themselves are made from shim stock in two pieces. One piece has a piece of brass wire soldered across it to bear on the point cam. The second piece has not been heated and provides the spring and contact with the fixed point.




By this time I had also made most of the other stuff you need to make an engine go. The valves are stainless steel. The valve springs were made on the lathe. The nuts were made from commercial nuts with flats milled to the appropriate dimension.


A stand was made from 1/2" square tube and the motor mounts milled to look like the channel iron used to mount the engine on the Bleriot.

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The next parts are the intake tubes and the plenum. The intake tubes are bent in a couple of planes and with fairly small radius bends relative to the tube diameter. I did some research on the web and coincidently our club, the Southern California Home Shop Machinists (SCHSM) was invited to tour the Phi-Tulip Company factory that manufacturs tube bending equipment. The company is an outgrowth of the Leonard Precision Products company of Pasadena that was started by Leonard Zerlaut back in the 30's. Leonard made a small bench mounted tube bender and an example was tucked away in an unused bench at the back of the factory. I took some pictures and came up with an approximation to use in my shop. This tool incorporates a bullet shaped mandrel to support the tube being bent but I could not get my scaled down version to work with that so I dispensed with it.


I bought some DOM steel tubing with the closest ID I could find and turned it to the required OD on the Logan. I used a sheer bit which gave a very fine finish on the tubes. In lieu of a mandrel, I filled the tubes with sand and soldered plugs in the ends. One end has a screwin plunger to get the sand packed very tightly. This bent up easily and after removing the plugs I trimmed them to length and they buffed up to a chrome like finish. I silver brazed the flanges on the engine end to fit the intake valve cage.



The intake plenum was carved out of a block of aluminum with some drill rod cutters made to get into the tight corners of the W shaped part. Eventually this was all rounded off with the Dremel and files to approximate the prototype. I don't have any dimensions from the prototype - just lots of photos.


To get the tubes to fit right I assembled them and heated them with the torch and adjusted them. You need to assemble the three tubes and plenum loosely at all the joints and shake it a little, and eventually it will tighten properly with every joint seated as it should be.


Some time at this point I made the compression release that is used to lift the exhaust valves on the prototype. I haven't actually got this to fit right so it sits in a box somewhere. I also made three spark plugs with Corian insulators as described other places on the internet.

I also had made the pistons, rings and wrist pins. These were all straight forward parts made as described lots of places on the internet.

The last image below shows how I resized the various nuts using the indexer with an arbor and an adjustable parallel for support. This was a little tedious as there are lots of nuts to do.

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The carburetor on the Anzani was made by the firm of Arquembourg and Grouvelle which was more known for radiators in 1909. However, many aero engines of the time used their carburetor. I found a US patent for the carburetor, 932860 patented Aug. 31, 1909. The carburetor is fitted with a device called the Dosair which is a ring of various sized balls laying in a set of corresponding holes. Intake vacuum will lift the balls to allow air into the intake to lean the mixture when the vacuum increases. This is a little brass fitting I simulated on the model. My model also simulates a float and is really just a needle valve system as found on model 2 stroke engines. No float, just a bowl.

I sawed a block of aluminum to the shape of the carburetor and drilled all the holes. The simulated float bowl is bored on the lathe to get access to where the intake fuel passage will be. The external bottom of the float bowl was turned to provide the boss for the inlet banjo fitting.

The fuel passage enters at the bottom of the float bowl and intersects a passage that goes up to the needle valve. The passage is drilled from the outboard side of the float bowl and blocked off with a plug that is blended into the bowl and is not too obvious.

The exterior of the float bowl was chucked on a mandrel in the lathe. It was not rotated but shaped with a flat spade tool run in and out as a shaper would do while rotated by hand.


finally the part was chucked in the indexing head on the mill and brought to its final shape.



To hide the crudeness of the carburetor body I sand blasted it.


You might notice that about this time I acquired a very nice Clausing mill and passed the little Benchmaster on to my son. Now that all the carving is finished I finally have a quill.

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