Episode 27 || Oil Sump and Filter
I made quick work of the oil dry sump and oil filter assembly, which is bolted to the underside of the crankcase. Oil drips down through the cam housing and crank case into the oil sump, is filtered through a brass mesh filter screen, then gets pumped back to the reserve tank by the oil pump I discussed in the last post. Oil drips down on the ‘front half’ and gets sucked out on the ‘back half.’
I didn’t model the filter in Fusion, but it lives right in the middle. The drawings call for a bit of brass mesh filter fabric to just be epoxied in place. That seems like a bit of a clumsy solution, so I opted to make a little removable/cleanable filter cartridge instead. It didn't turn out great, as you'll see. But it's probably good enough.
Oil Sump Body
Pretty straightforward part here. I started by squaring a piece of 6061 aluminum up on the Bridgeport, then ‘drilled’ a couple holes using a ball end mill which will accommodate the sides of the filter cartridge.
Then I roughed out the main pocked by plunging with a 1/4” two-flute flat-bottom end mill.
Instead of using a boring head or bolting it up to my rotary table, I used the very modest early-1980s-vintage two-axis CNC capabilities of my Bridgeport to complete the circular pocket. Turned out great.
Then I used the same 1/8” ball end mill from before to complete the bottom of the filter cartridge pocket.
A couple bolt holes through the top and one hole in the side for a bit of brass tube and she’s good to go. Same as before, I used a dab of Loctite 603 to help hold the tube in place. (
NOTE: After bolting this to the motor, I realize that the brass tube is too close to the base of one of the jugs to get a bit of tube on there. I'll have to replace this piece with one that's got a 90* bend in it. I'll do that some other time.)
Oil Filter Cartridge
As stated in the beginning of this post, the drawings call for the brass filter mesh to just be epoxied in place. I think that’s dumb. So here’s my take on a removable filter cartridge. It looked a lot better in my brain; you'll see.
I started off with four bits of the same 1/8” OD brass tube I’ve been using everywhere else, and a bit of #100 mesh (0.006” openings) brass filter fabric I scored from McMaster. Everything is well oversized here; the filter cartridge ends up being pretty darn tiny in the end.
I then trimmed the four tubes to the correct length on the lathe. Then while being held in a little Starrett pin vise, I used a hand file to chamfer each end at about 45 degrees. A Dremel with a 0.025”-wide slitting blade worked great to make a length-wise slot in each of the tubes.
I wasn’t sure what to use to join everything together --- epoxy, CA glue, solder, etc. I opted for silver solder, as I had it on hand.
After cleaning things up best I could and adding a bit of flux to the insides of the tubes, I soldered one side on at a time until I got all 4 on there. It ain’t pretty, that’s for sure. Maybe epoxy would have been better? Anyway, this is how it’s going to be, getting too close to the end to get bogged down in remaking parts like these.
If I were to do it again, in addition to trying something other than solder, I think I’d try to use 1/16” OD tube instead of 1/8” OD and modify the pocket in the sump body accordingly. While the 1/8” tube is indeed pretty tiny on a regular human being scale, it seems a bit too bulky with the cartridge complete.
Anyway, it’s good enough. Let’s just move on.
TIME ON OIL SUMP AND FILTER: 4.0 hours
CUMULATIVE TIME: 424 hours