The Crosshead Trunk Base
It's the weekend and time for the shop! The crosshead trunk I've constructed so far will need lugs for bolting the engine to the floor, so to speak. The article suggests either milling these from the block that forms the trunk, or alternatively machine grooves at front/back of the trunk and attach square bars extending beyond the width of the trunk to form the lugs. I took a third approach because I didn't have material tall enough for the trunk, so my lugs are really part of a baseplate under the trunk. I'll show that today.
I started by screwing a sketchy looking piece of 1/4" thick 1018 steel to the crosshead trunk I made. Recall I already had threaded holes in the trunk that were used for screws to hold it to a mandrel. I thought this was a fine re-use of these holes.
Next, I machined the base to size. I decided it would be best to do this while it is attached to the trunk. You can see I slopped on some dykem dye so I could see when the ends were flush with the trunk, and I used a depth gauge when working the long dimension until they were 1/4" offset. That's the allowance for the lugs.
I skimmed it with a facing mill to make sure it sits perfectly flat. The finish of my cut is getting real lousy so I'm assuming the inserts are getting dull. My lighting is rather harsh and makes it look worse than it is. But it's still not great...but not visible on the finished engine either.
Now it was a matter of hogging out material leaving the lugs behind. Note again that I added dye so I can see when I touch the side of the trunk. This worked really well on this side, but I overshot a bit on the other side
. But nothing a file can't fix. I was just trying to avoid file work as much as possible.
Here's the cleanup pass. The dye worked well. I'm just starting to smudge it around.
Then it was simply a matter of drilling the four holes into the lugs. This was easy to do from the underside.
The crosshead trunk is now almost done. I need to make front/rear plates for it and turn down the ends to form bosses for fitting into these plates. When I do that turning I'll do a final touchup so the ends are perfectly flush. The plates, in theory, will be silver soldered in place.
Next, I need to make those front/rear plates. Hopefully I'll get that much done this weekend. Stay tuned!