My goal today was to get the crankcase vent tube installed to allow me to press forward with other engine installation tasks.  And I almost made it, except on the last bend of the crankcase vent tube it cracked… with enough force that when it let go it popped me on the forehead, leaving a nice little knot.

But that was later in the evening, and I’ll get to that in a bit.  Let’s start at the beginning with making the crankcase vent tube cradles and saddle (AKA “Batman Parts”) to allow securing the aluminum vent tube to the exhaust pipes with hose clamps without crushing the tube.

First, I spent a good little bit doing some research since I’ve never milled multiple parts before.  It’s not overly difficult, but there is a bit to learn in how to set the files up in Fusion 360 to be able to combine all the respective parts and set them up to post process them in CAM.

Moreover, these parts are only 0.58″ wide, where the only stock I had on hand was 0.75″ thick.  I grabbed the best piece for the job and clamped it up in the milling machine vise.  I then probed the stock to zero out the coordinates.

And then did about 5 passes with my Superfly facing tool to bring down the thickness of the stock to just a few thou off: 0.576″ thick.

Since I’m cutting the parts out of the entire thickness of the 6061 stock, I used my tried and true blue painters tape and super glue method to secure it onto a sacrificial wood plywood base.  Moreover, once I drilled the holes in each part (pic 1), I then drove a pair of wood screws into each hole to help secure these smaller parts in place (pic 2… I honestly don’t think they needed it, just insurance).

I can’t take really big cuts on material on my mill due to the TTS quick swap tooling system.  The downside to this system is that without enough clamping force, too big of cuts at the 3000 rpm I have available will pull the tool out of the spindle.  So what I’m saying is that it took a good little bit of time to mill these parts.  Here they are fresh off the mill (pic 1), and cleaned up a bit with their 3D-printed ABS prototypes (pic 2).

After deburring the holes and hitting the corner edges with a file, I test fitted all the crankcase vent tube inserts.  Here is the aft one in place… looking pretty good!

And the middle and forward inserts as well.  Again, they fit really well.

I hadn’t yet bent the 6061 tubing, so I tried out test-fitting the aft 2 inserts with the straight tube.  Still looking good.

I’ll note that I spent a good while working the position of the forward black rubber crankcase vent hose since it was a little close to the “shark fin” rudder cable bracket. In fact, I installed the right rudder cable going up to the nose to get a clearer idea of exactly how much space I had to cram all this stuff into the engine compartment.  As par usual, it’s all very tight in there.

I then used a scrap piece of softer 1/2″ diameter aluminum to get the angles dialed in to allow the aluminum crankcase vent tube to flow with the exhaust pipes.

Again, I did a good bit of research earlier in the day, to include bending 6061 tubing.  What I learned is that bending 6061 can be tricky, but this tubing here is fairly thin-walled at 0.035″ thick, and with the tube filled with sand I thought I’d be good. Especially since the first bend went just fine.  So after playing the 30 minute game of “find me if you can” I located my 5/8″ spring specifically for bending metal tubing… since my tubing bender tool only goes up to 1/2″.  I then got to work.

However, as I regaled you at the start of this blog post the forward bend, which would allow attaching the black rubber hose to the vent tube, let go and snapped as I was applying a good deal of pressure on it to bend.  I had a very thick-walled piece of PVC pipe clamped in my bench vise vertically, and had slid this aluminum tube down into the PVC pipe.  I had the bend at the opening of the PVC pipe, which was about eye level with me.  When it snapped it popped me right on the forehead… so, the ‘ol blood, sweat and tears is real on this build! (actually there was no blood… this time!).

Note the cracked tube in the upper right corner.

The good news as you can see in the pics above and below is that these milled cradles and saddle are functioning exactly as I designed, and fill around the tubing under the hose clamps very well.  Ironically, I may just end up switching to stainless steel since I have that original crankcase vent tubing stock on hand as well.

Tomorrow I’ll try cutting, welding and reinforcing the failed tube to see if I can salvage it. If not, I’ll probably have to order a no-kidding tube bender and either another aluminum tube, or press forward with the stainless steel vent tube.