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Offy – Ring Stress Relief Fixture I use George Trimble’s formulas for the dimensions of my rings and the stress relief fixture. I have a print for this fixture that is parametric, that is I update the dimension of my cylinder bore and the rings and the CAD program does the rest of the...

Good start on the crank, This what i use https://littlemachineshop.com/products/product_view.php?ProductID=4464

If you are looking at V8s, how about one of George Britnell's, I don't know if he has plans available for both his Ford Flathead V-8 in 1/3 Scale and the 1/3 scale Ford 302 V-8. If you would like to make a 289, you might be able to use George's 302 plans if they exist. The 302 was basically...

Terry, This might be a simple, inexpense, non-invasive way to measure RPM. The long black wire picks up the ignition signal inductively through the spark plug lead. The tach is programmable for many different engine cylinder configurations. Even if it is just used as a diagnostic tool, it is...

Terry, Thanks, that is a lot of help. My spindle speed is too fast and my first attempt was WAY too fast. I will give your speeds and feeds a try. The cutter has a lot of cutting edges per revolution so 250 RPM for a gear cutter is not the same as say a 3 flute end mill. I have been using...

Offy – Camshaft Gear Caps The Caps that cover the Camshaft Gears are small parts, but pretty complicated to fabricate because of all the small features on all sides. It is challenging to maintain registration of the features on the four sides needing machining. The caps are shown on an engine...

I used aluminum conrods on my Wallaby and did some calculations to determine the proper weight of the counter weights. Since the pistons do move in unison the engine can be modeled as a single cylinder engine with twice the mass of one of the con rods, pistons, rings and wrist pins. The formula...

Gaskets - Part 2 Below is a complete set of Gaskets for the Offy. To get a hard flat surface I started with a block of wood clamped in the vise. A wood router bit was used to level the surface of the block. A slab of Corian was screwed to the wooden block to provide a hard flat work...

Jerry, a good buddy of mine, just completed his first IC engine build, and it's a runner! Jerry has a complete machine shop with every tool a machinist could desire and has been building experimental aircraft as a hobby for many years. Like many, he chose the Webster as his first IC engine and...

Offy - Gaskets Part 1 Gail (@GailInNM) was kind enough to cut gaskets for me on my last engine. This time around I decided to develop the capability myself. It is something I want to be able to do going forward. My first task was to procure PTFE film in .005", .010" and .020" thicknesses...

Yep, I have done the same thing (actually ruined a part that way), that is why I touch off the vise, write the z height down, instead of touching off on the part again. Because I might have machined off the top! But watch those minus signs, I set a Z height one time and forgot the minus...

Bob, It is looking really good. What is your concern with changing end mills? The X and Y should remain dead on and the Z height needs to be changed to account for any difference in height between the two end mills. I will machine with the first size end mill, then bring the end mill down...

There is a well-known expression known as "Paschen's Law" relating spark gap to pressure and potential. Performing a little tweaking on the constants there is a linear model. The relation for gas composition air is: V = 4.3 + 136 × (p / T) + 324 × (p / T) × Dg V = voltage potential (kV) p...

Go Bob Go...... One thing I do to insure the hold down screws are in the exact center, is to drill the holes with the CNC mill set to 0,0, then tap them in the vice. It is a little akward, but insures the center of the conrod holes are exactly where your CNC program thinks they are in both...

Looking good Ray, I will take a look at your circuit. I agree with your statement about lots of filtering on power as close to the part as you can get it. I think 12,000 RPM is plenty fast enough ;) . I have about 9 degrees of sweep given the radius of the magnet on the flywheel, close to...

Offy – Cambox Covers Cambox Covers The cambox covers mount to the top of the camboxes and enclose the camshafts. They are often polished aluminum and are a distinctive feature of the Offenhauser engines. In my scale they are sections of a .67″ tube–a non standard dimension. I thought of...

My vote is to chock it up to the learning experience and make another one. Like I tell my wife, the garbage man could make three engines for every one I do.

When using the G02 code don't you need an I and J term specifying the center of the arc?

Sorry, I meant CAM, not CAD. As long as the program cuts from top to bottom, it shouldn't matter where you set Z=0. For example, would it be easier to set Z=.25 at the top of the part given the part is .25" tall? I have used the epoxy potting technique to good effect. I feel for you...

Cambox and Camshaft Bearings The Cambox houses the overhead camshaft, its bearings and the cam followers. Since I have completed my first camshaft, I will move on to the first Cambox. I start with an oversized work piece, fly cut the top and square off the front end. On the second cambox I...