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A flathead V-8 engine

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gbritnell

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Gentlemen,
I thank you for the gracious responses. One of my enjoyments is designing and building engines. The other is sharing it with builders and modelers like you.
That being said here is the next installment in the build.

The bellhousing was quite a piece of machining. I start with drawing and metal in hand but have no way of knowing what the time involved will be. I know what my general plan of attack will be but naturally things change as the process gets going.
In this case I started with a piece of 6061 aluminum round bar 5.75 inches by 2.25 long. The first step in machining elaborate parts like this or any other is to start with the inside shapes. The reason for this is quite simple. If you machine the outside there is generally no place to chuck or locate to because of the shapes of the surfaces. Once the inside is done you can use a vise, clamps or fixture to do all the outside machining.
I gave myself some layout lines and chucked the blank in the 4 jaw chuck. Once centered on the layout lines I bored the center hole and then roughed out the extra stock with a heavy boring bar.

The part was then moved to the rotary table to finish the inside. As with all my contoured parts I make up a step-off chart to form the radii. The rotary table was centered, the zeros set then the part was mounted, centered and clamped. I went in with a .50 diameter ball mill and started stepping off the shape. Once complete I switched over to long 2 flute end mills to cut the inside shape of the clutch area.

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gbritnell

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I forgot to mention. While doing the inside shape I drilled all the mounting holes, some for the screw clearance and some for tapping. The tapped holes would be used to mount the housing to the fixture plate for all the outside machining.

With the part screwed to the fixture plate the rotary table was put back on center and the previously bored center hole was indicated true. I had given myself some rough layout lines as a guide but this is just for roughing the heavy material off.

I had to make two step-off charts for the outside radial shape. The first cuts were for the radius on the top of the two ribs that are cast into the full sized bellhousing. These go from the transmission flange to the top outer mounting flange. Once the first cuts were made the part was removed from the table and the steps blended smooth so that layout lines could be applied as a guide for cutting the second radius. There is no easy mathematical way of doing it because as you work your way down the radius the contact point with the layout line changes.

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gbritnell

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One of the nice thing about machining with a part on the rotary table is that you can dial up all the different angles without having to move and reclamp the part like you would normally do if it was just clamped to the mill table. The piece was slowly whittled away, stepping into corners and working down the previously roughed shapes. An endmill with a small radius was then used to clean up around the mounting flange and provide clearance for the mounting bolts.

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gbritnell

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The area for the starter needed a boss added so this was turned and threaded then lightly pressed into the housing. From the inside I securely fastened it with a special made aluminum screw.
The other area that needed finished is where the clutch throwout arm enters the housing. I set the bellhousing in the mill vise and cut out that window. All that remains is filing, burring and polishing.
Here are some pictures with it mounted to the rear of the block.
gbritnell

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Tony Wells

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I admire your patience in the step-over work. I never developed the knack for it for some reason. I think it would be nice if you'd elaborate just a little so some who may not really understand how that's done. I'd say they would gain new appreciation for your already outstanding work.

I know I appreciate you showing your work, and so does the rest of the group.
 

gbritnell

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In response to Tony's question about how I step off a shape I will try to explain it as simply as possible.

When I served my apprenticeship as a metal patternmaker, late 60's, our shop did a lot of repair work on patterns and coreboxes. We had some duplicating machines that would be set up for doing large areas but when a small area needed to have the weld brought back to the original surface or a small patch needed to be machined they were all done by the step off method.

Each of the old timers on the mills had their own little reference books that had standard radii calculated using standard ball end mills. These books were very valuable considering all the math (trigonometry) had to be done by long hand. There were no calculators at that time.

The process went like this. You take a given radius that needs to be cut and add the radius of the desired cutter. You then calculate the distance of the step that will give you the desired cusp (height of material between cuts). Once you have that then you continue with that same angle of step to give you the numerical coordinates (X or Y and Z) you need.

You might think, "why step something off when you could just tilt the mill head or put the part on a sine table and cut it?" Well sometimes the area in question is a pocket that has no angular access, meaning you have to go in from the top so stepping is the only way.

I have attached a document showing both internal and external calculations.

With today's technology and CAD programs it makes it fairly simple. Take you part curvature, add the radius of your cutter, set up your step spacing, do an array of the radian and then add coordinate dimensions.
The hardest part is paying attention to where you are on you chart. Over, down, over, down, over, now where was I?

gbritnell
 

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Dataporter

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This is amazing!

My first experience with auto mechanics was when I was about 8-10 years old and my Dad had a 1950 Ford Coupe with a flat head. This was circa 1960 or so. My Dad, one of his good friends, and I replaced the engine with a new short block. I'm not saying I did much except hand them tools and maybe turned a few wrenches. But, I remember, for me, it was so much FUN!! So this thread is really brings back fond memories of those days!!

Dave
 
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George, your work continues to leave me in awe. Keep the pics coming, I am thoroughly intrigued!
 

gbritnell

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And I thought the bellhousing made a lot of chips! It was nothing like this next part. The oil pan.

I started with a large rectangular piece of 6061 aluminum. There is no easy way to rough it out and within the limits of my machine the following steps were the only ones I thought were feasible to get to where I wanted.

As with any part the first thing to do was to square up the stock. This was followed by center drilling and successive drilling with larger drills, first a .25 to serve as a pilot, next a .50, then a .625 and finally a .75.
The drills went to a safe depth for each level of the pan. I really didn't want to drill through a $50.00 piece of aluminum.

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gbritnell

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Once the holes were drilled I used a couple of .50 dia. ball nosed mills. I used a short one to get most of the hogging done with the rigidity of the cutter. This was followed with the longest one I had to get down to the bottom of the lowest cavity. I had cutting dimensions to work to and stayed about .04 away from them, just in case.

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gbritnell

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With the roughing out of the way it was time to start picking away at the internal radii. The hardest area was at the front of the pan where I had 3 surfaces coming together, the angular bottom, the angular sides and the side walls of the pan. Once all these shapes were cut close everything would need 2 degrees draft so all of the stepping would be repeated once again.

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gbritnell

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The inside machining was finished so it was time to start on the outside. The first area which needed the most work was the front so I gave myself a layout line and bandsawed a big chunk of metal away. The piece was then clamped to an angle plate and with the angle set I cut to my layout line leaving a blob where the front radial shape was. Although I could have cut a little closer I didn't want to take a chance of undercutting anything. At this point it was no longer about money but the hours of drilling, roughing and step milling involved.

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Whew!!!! The front was done so the part was turned around to do the rear area. This had it's own set of issues due to the oil pump bulge. Once again after everything was roughed the mill head would have to be cocked over on 2 degrees to match all the outer surfaces to the inside shapes.

All of this 2 degree business wasn't really necessary but the full sized pan has draft on it and so will this one.

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gbritnell

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The pan has 3 different depths. With the front and rear machined I carefully sawed the remaining two pieces from the bottom. The part was mounted to a fixture plate so I had some way to hold it. The bottom sets were milled, the radii stepped off and the side walls cut to 2 degrees. I then knocked down the large radii on the corners with a radiusing cutter getting as close to the angular surfaces as possible. This gave me a head start although there would still be a lot of material to remove to finish the radii.
I have some aggressive carbide burrs but was very careful not to undercut any of the features. One I got close it was all hand filing from that point.
I haven't decide whether I'm going to finish the inside. I have plenty of time for that.
gbritnell

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gbritnell

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Here's a bit of information on the pan. Except for the very deepest pocket all of the other walls are .06 thick. The bottom is .110 because it needs threads for the drain plug.
As I have mentioned along the way, when making parts from bar stock the inside always needs to be done first. With most of the parts I'm making a fixture plate is also needed. At this point I have three, 2 of them serving double duty for other parts. It seems like a waste of material but some times there's no other way to hold a part for machining. Usually if a part has clearance holes for mounting screws I'll drill and tap them for mounting to the fixture plate and then go back and clearance drill them when I'm all finished machining the part.
gbritnell
 

gbritnell

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It's time for an update on the engine. The plan is to make all of the big pieces which would represent the major castings and then go back and start making valves, sleeves, crankshaft etc.

I have just finished the water pump bodies. On a flathead engine there are two, one on each side of the front of the block. To get a water passage inside the pumps would have to be made in two pieces, the main outer part and a cover plate for the rear. The water pumps also have the front motor mounts cast into them so to replicate these I had to step the shape out on the backside of the main body to make the rib thick enough for strength.

I started with the back plates. These were roughed out, drilled and tapped then mounted on the rotary table to turn the boss and use the rotary table to cut all the angular edges. The tapped holes (2-56) are also for mounting to the fixture plate.

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gbritnell

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The pump main body was next. As with the back covers the stock was cut to size leaving .02 for a safety margin. These are quite complex parts and would need multiple setups over the course of machining.

The eventual mounting holes were all tapped rather than drilled, this way they could be used for mounting to the fixture plate. The impeller shaft hole and the water inlet hole were also put in while the block was in the vise. The vise was then removed and the rotary table once again set up. The water cavity was lightly sketched onto the block and it was then indicated and clamped. You can see the offset motor mount rib sitting higher than the main surface.

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gbritnell

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From the mill the parts went to the lathe. The four jaw chuck was set up and the fixture plate with the body mounted to it was indicated both for concentricity and parallelism. This operation would be to turn the conical hub boss and bore for the O ring seal and ball bearings.

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gbritnell

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From the lathe it was back to the mill and rotary table to spin the water inlet tube.

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gbritnell

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With both water inlets done, to this point, the part was then moved to the center of the conical boss, indicated and clamped. It would be in this position for all the remaining machining except for machining and drilling the angular rib that supports the motor mount. The same profile drawing that was used for the back cover would also be used to do the outside shape of the body, except for the area around the support rib.
The hardest part is keeping track of all the steps and dimensions.

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gbritnell

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Up next were 8, 2-56 flat head screws for mounting the back plate to the main body. The covers were installed and the screw heads brought down flush with the rear surface. With the parts assembled the remaining stock on the corners and around the inlet boss were burred, stoned and filed.
As can be seen on the one pump body there is a small nick at the base of the angular rib. I was using a .187 end mill with a .031 radius on the corners and was sneaking up to the main surface using a piece of paper as my gauge and went a tad too far. Oh well, 2 machines, multiple tooling changes, 200 cuts and 1 nick.

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gbritnell

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Here's several shots of the pumps sitting on the front of the block.
gbritnell

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Absolutely AMAZING!!!!!!!!!:man:
 

gbritnell

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Gentlemen,
Time for an update.
The intake manifold is progressing well.
As with all these parts cut from solid I start from the inside. That means cutting the port runners. On this engine I decided on using 2 carbs, first of all for the aesthetics and second to shorten the length of travel for the intake charge. Each carb will feed 4 cylinders.
I squared up the block in the vise and then switched over to the angle table to put the ports in. The angle at the ends will match the entry angle into the block. I gave myself some layout lines but verified them with the edge finder. The dimensions were set and the table was tilted to the proper angle. I first went down with an end mill to establish a flat at the layout line. From here I could touch of the ball nosed mill and plunge down to the proper depth.

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gbritnell

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The angle table was removed and the vise set back up. The block was mounted and the edges once again picked up. Zeros were set and the runners were milled. At this point I also put the mounting holes in.
Once the runners were finished I turned the block 90 degrees and cut the area out between the runners.

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