Time for some Lathe work (or should I say fun
)
The bearing holders are fairly straight forward jobs on the lathe. I need to fabricate two main crankshaft bearing holders and two camshaft bearing holders. Here I have the start on one of the Crankshaft main bearing holders and I am test fitting the crankshaft bearing. I used sealed bearing, as opposed to open or shielded bearings. I have used open ball bearings in the past, but used a rifled bronze bushing out board the bearing for an oil seal. At the speeds and temps that this engine will run, the sealed bearings should give good performance and provide a good oil seal. The bearing holder has an oil seal O-ring to seal it to the crankcase as shown below.
The photo above shows the main features of the main bearing holder: a groove for an oil seal O-ring, a .010″ relief to clear the ring of the inner race. I first faced the blank, turned the outside diameter, drilled and reamed the through hole to clear the crankshaft. I then used a boring bar to create the features on the inside of the bearing holder. A round tool with the same profile as the O-ring was brought to bear to create the groove.
The holes for the mounting screws in the main bearing holders were drilled on the mill. The inside diameter of the main bearings is .5″ and so I used the 1/2 inch dummy crankshaft clamped in the chuck on the mill to align the bearing holder in the mill vise. I then centered the mill DRO at this point and used the bolt circle feature to layout the six mounting holes on each bearing holder. I am using 6-32 socket head cap screws to secure the bearing holders to the crankcase. I first use a .113″ drill, the size for the tap, not the clearance hole for a 6-32 screw. I then remove the bearing holder from the mill vise, install it on the crankcase and match drill the holes for the 6-32 threads in the crankcase. Finally, I return the bearing holder to the mill and drill the .113″ holes out to .140″ in the bearing holder; the clearance hole size for the 6-32 screws.
Now to turn my attention to the camshaft bearing holders.
The camshaft bearing holders were fabricated using the same work flow as the main bearing holders. The primary difference was in the fabrication of the rear camshaft bearing holder. It has an additional feature that routes oil from an oil gallery to the center of the camshaft where oil will travel to the cam lobes.
There is an additional step in the fabrication of the rear camshaft bearing holder, the CNC router was used to create the profile of the flange.
The rear camshaft bearing holder was then mounted in the mill vise and the oil hole was drilled. This hole routes oil to the center of the cam shaft. A hole is drilled down the length of the camshaft to deliver oil to the cam lobes.
The timing cover was machined by the CNC router. Here it is mounted to a block of MDF with 5 minute epoxy. I have had trouble with this technique in the past as the MDF will absorb coolant and swell. Here the technique worked fine as the timing plate is just a 2 dimensional profile and a slight variance in the Z axis will not materially affect the resultant part.
The timing plate is responsible for aligning the bearings for the timing gears as shown in the photo above. There will be a timing cover that holds the mating bearings and encloses the timing gears
I am working on a base for the engine that will also hold the other components required to run: radiator and fan, fuel tank, timing electronics, etc. I also fabricated some engine mounts along with the display pillars and decorative washers.
The engine so far.