With the main journals rough turned, I left .008 for the inevitable, the blank went back to the mill to rough out the crankpin areas. This was done in three steps, the deepest cut and then the two side cuts leaving a somewhat square area to be turned.
Two fixture blocks were machined from aluminum. The one for the chuck end has a large diameter to accommodate the flywheel flange and the one for the tailstock has a smaller bored hole to fit over the front diameter on the shaft. The tailstock fixture also has a center drilled hole to locate the live center Both blocks are drilled and tapped for set screws that are used to locate on the flats milled on the ends of the crank. The set screws (grub screws) are ground flat to more accurately locate on the flats.
The headstock end was mounted in the four jaw chuck and indicated to get the proper offset for turning the crankpins. (1.125) The blank was then inserted and tightened, rocking back and forth as the screw was tightened to centrally locate the stock. The tailstock fixture was then slid on and tightened in the same manner. The live center was then inserted and tightened just enough to hole the blank in place.
The crank was then mounted between centers and the remaining stock was cut from the main journals. The front diameters were finished as was the flywheel flange. For most of my engines I have used a key and set screw to hold the flywheels in place but for this engine I thought a bolt flange would present less loosening problems while running
Hi Eddy,
I have no particular use in mind. Every year I come up with a project to get me through the winter. This year it's this flathead engine. I enjoy machining and building things whether engines or other mechanical items.
I have a 302 V-8 along with a T-5 transmission and 9" Ford differential. The plan was to build a complete chassis but that's been put aside for the time being.
gbritnell
Ok, we left off with the turning complete on the crank so the next step was to start cutting the extra stock away from the counterweights. For this a fixture would be needed. I already had a flat fixture plate that had been used for machining the block so I made up 5 pedestals to hold the crank. These were milled to size, tapped and drilled then they got a .751 hole bored in them to fit the main journals, after which they were just split open on the bandsaw.
The fixture plate was clamped to the mill table and indicated parallel with the X axis. The crank was then clamped in place. To simplify setup for each throw I set up an adjustable parallel to go under the horizontal throw journals. This put the other throw in the vertical position to cut the counterweight.
After all the the counterweights were cut I tilted the mill head on 15 degrees to cut the extra stock from the top of each throw at the crank pin.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.