Prop Flange Extension

This will be a quick post - as part of my power plant setup, I'll be using a 4" aluminum spacer to help streamline my cowl around the engine. At my place of employment, I've got access to a CNC mill and a larger metal lathe, among other things. I was able to pick up a 5" diameter 6" long piece of 6061 aluminum for about $40 on Ebay, modeled what I wanted in CAD, then went to the manual lathe to turn it. I should have taken more pictures, but I didn't think about it; I do a fair amount of machining at work, and it all feels pretty routine anymore. The first picture I have is after I turned the stock down to final inside and outside dimensions, except for the face that will abut the flywheel. I set it up on a rotary table on the mill to get a bit more precision with the 6 prop-mounting holes, but that was probably overkill.

 

Spot drill, undersize drill, final drill, chamfer the edges. Not exactly rocket science. I intentionally left about an extra half inch on the end that I chucked up for the majority of the turning work, so that the marks left by the chuck wouldn't be on the final part. When I reversed it to turn the remaining face, I used some orange .050" plastic shim stock between the jaws and the part to avoid marring the finished surface. Turning the remaining face was straightforward, though I took light cuts to make sure I wouldn't pull the part out of the chuck. 

After the final lathe operation, I drilled the other 6 holes and cleaned up the part. Nothing left to do but put it away until the engine is ready to run... except test fit it on the flywheel.

More Wood!

Ok, so I got the necessary braces installed. I also set up the seat well enough to take some measurements with a laser level simulating the horizon from my height when seated, and used that to generate templates for the canopy. However, in the meantime, there were a few more pieces of woodworking to attend to. The first is that, because of the way the fuselage is built, the plywood that stretches over the crossmembers behind the seat doesn't have a good way to glue to the longhorns.

The solution the previous builder used was to glue on more spruce to build the sides up to level, and it makes sense to me. So I went ahead and did the same. First I shaped some pieces of wood to follow the contours of the plane:

Then I glued them on, came back a day later, and started planing. I had to build up the center crossmember as well, because of the compound "dip" in the fuselage (Only needed about .02" or so, but it was easier to glue on a much thicker piece and plane it down later.) I used a hand plane held at an angle, so that the center x-member was being cut while the plane used the forward and rear x-members to set the height. Once the x-members were all co-planar, I planed the sides to match.

I didn't get a picture of the finished product, apparently. I was about ready to glue the plywood on, when I realized I'd want all of the gussets in place first; they'd be hard to add later! So I spent some time sanding tiny wood blocks to the right compound angles. It's not very difficult, but it was a little time consuming. I ended up needing 12; I was able to finish and glue 9 before I ran out of time.

The next time I was down, I finished making the gussets I needed and glued them overnight.

After everything had time to set, I planed and sanded everything down and cut the plywood to fit. This is pretty thin stuff, and I've found that by using a utility knife to cut through it, I can usually avoid sanding it except to break the sharp edges.

After several passes with the knife, it usually only needs a touch with sandpaper to get the edges smooth, and as long as you marked it right, it's bound to fit. All that was left was to glue it all together and clamp it down.

Next time I'm down, I'll pull the clamps off and start re-working the fiberglass seat backs. They need to be trimmed a little bit in order to fit the new angle. I'll probably cut the holes for the control sticks too, which will allow me to install those again and start fiddling with their location. I'm gearing up for all of the non-fiberglass things, since winter is almost upon us here. I've been working on designing a prop in CAD, as well as a control stick grip. Unfortunately, it looks like the canopy/aft deck/front deck is going to have to wait another winter... at least I have a plan for that now.

Landing Gear (part 2)

(Continued from Landing Gear - Part One)

My landing gear legs finally showed up, so I took advantage of the last of the warm weather to get some fiberglassing done. I was pretty excited, since the plane has been sitting on jack stands for quite some time now, and I'm always nervous about it falling off when I'm getting in and out to make airplane noises.

Once I had the gear planed to thickness and edges chamfered, (ScotchPly is really hard on planer blades!) I wrapped a couple of layers of bi-directional cloth infused with epoxy around them, as per the instructions. After that cured, I hot-glued a couple of straws to the backs as a housing for the brake lines.

I mixed up some really thick micro and filled in all around the straws to help the next layers of fiberglass lay smoother.

Once that cured, I sanded it all smooth and wrapped the next layers of fiberglass cloth and epoxy around the back. Nothing to it, really.

The next step was to use some more micro and just squeegee it over the sides of the leg, so I could sand them nice and smooth (without adding much extra weight.) I also used a high-speed rotary tool to open up holes to the straws and sanded everything smooth.

Before I got to the fiberglassing stage, I had gotten the brackets all drilled and prepped. Because of the shape of the brackets, I had to get a little creative with the hole placement for the axles.

The next step was a little scary - the geometry of the axles and landing gear is sort of important, and I only got one shot at drilling holes into the fiberglass legs. I took my time and re-verified a couple times, and I still ended up with one axle not quite pointing the right direction - but I can machine a nice aluminum shim to fix it, since it's off by only a couple degrees. 

Once my holes were all drilled, I mixed up some flox, spread it on the brackets, and bolted the legs to the brackets for good.

While I waited for that to cure, I got my new rims and tires out, packed the bearings with grease, assembled them onto the axles, and the axles onto the brackets. It's starting to look serious now!

As soon as the epoxy showed the slightest indication of curing, I couldn't help but drag the whole assembly out to the garage and bolt it onto the plane. It's not a great picture, and there's a ton of crap in and around the plane, but it still looks a heck of a lot better with landing gear than it did on jack stands!

I haven't been idle with the engine - just frustrated, and lots of work for very slow progress. It was really good to get this out of the way, just to feel like i'm getting *something* done.

Dowels are hard, PlastiGauge is soft.

It took a lot of work, but I got all four dowel pins out without damaging the crank. The two I put in came out easily enough with some vise grips and a bit of twisting and pulling... the two that were in from before were another story entirely. Nothing would touch them, including the hardened jaws of a *nice* set of vise grips. (Those are no longer a nice set of vise grips, by the way.) In the end, I discovered why machinists have drill bit sets up to half an inch with just a couple thou of difference all the way up...

...It's because hardened steel pins can't be drilled out with big steps between bit sizes! It took me a solid hour and a half to drill each pin out. However, both of them twisted out right before I broke through the wall of the pin (after a couple good taps with a hammer on the side of the pin to break it up a bit.)

I checked the face on a dial indicator, and at most it's out a single thousandth at the edge. That's about an inch from center, which means that might account for about 5 thousandths at the edge of the flywheel.... which means something else is amiss. I checked the flywheel by placing it on an indexer, supported by placing a tight tolerance block between the indexer and the mating face on the flywheel. Spin the indexer, check for runout.... I forget what I got, but it was insignificant (which is why I forgot it. :D) I was pretty puzzled at that point. However, since the pins were out of the crank, I was able to rotate the flywheel on the crank. How does that help us? Well, before I pulled the dowels, I'd marked on the flywheel exactly *where* the runout was, as well as *how much.* When I put the flywheel back on after the pins were out, I lined it up pretty close to where it was originally... and got pretty much the same results. (I didn't use an indicator, as I was less interested in how much it was out as *where* it was out.... and it was wobbling pretty obviously.) Ok, repeatability, that's good. So I rotated the flywheel 180 degrees and tried again. If it was the flywheel, that should've made no difference; the marks on the flywheel still should have been correct. If it was the crank face that was out, then the marks on the flywheel should have been exactly (or close to) opposite what the flywheel was showing the second time around.

So what did I find? Well.... actually, it was about 70 degrees off from where it was originally. I didn't know what to make of that, until I started taking careful measurements of everything. What I found was that the flywheel had a bit of a radius where it mated with the crankshaft, and the crankshaft did not have that radius. I think what's happening is that there's a tiny bit of play between the *side walls* of the flywheel and the crankshaft, and the radius causes the face of the flywheel to be tighter than the crankshaft can fit into. Add the radius and a little bit of slop and, unless the radius on the flywheel and the edge on the crankshaft are perfectly uniform and smooth, odds are the flywheel just isn't seating fully and is staying at a bit of an angle. The fix is simple; just cut a matching radius (or, much easier, a slightly relieved chamfer) on the crankshaft. The side walls and dowel pins will still locate the flywheel, and the face where the two meet won't lose much area. I like that idea better than cutting a sharp corner into the flywheel. 

I should mention, the reason that this is an easy fix is because I recently picked up a Jet 9x20 metal lathe. Just as soon as I finish getting that set up in the basement, this will be a pretty straightforward job. I'll be spending my evenings this week cleaning it up and, as soon as my insert tooling shows up next week, I'll be making chips and breaking tools. Also touching up airplane engine parts. 

I also got my oil galley plugs straked in place so they can't rotate out. I found one of my case savers was loose, so I used some red LocTite, filed a notch in it, and straked that in place as well. 

The last thing I wanted to do today was check my connecting rod bearing clearance. If you've never heard of PlastiGauge, you're in good company; none of the auto parts stores I went to had ever heard of it either. I ended up at a local NAPA, a company I spent 6 years working as a counterman for, and gave the kid at the counter the part number I remembered as being correct. "Huh, it says we've got 12 in stock. What is it again?" It comes from the warehouse packaged as a dozen, so I guess it shouldn't surprise me he'd never heard of it; he'd never sold any of it. Anyways, PlastiGauge is a kind of plastic-y wax string that's very precisely formed. A strip of it is placed between two surfaces you want to check clearance on, and those two surfaces are brought together however they will be brought together during final assembly. In this case, those surfaces are the connecting rods with bearings installed, and the crankshaft. Blurry picture, but the green little stripe in the middle of the white grease is the PlastiGauge before the con rod is tightened....

...And after:

The lighting was pretty awful. However, I can tell you that the strip of green that's *not* a weird reflection is the one above the .0015" mark. Basically, that wax gets squished to different widths based on how much clearance is available, and the package the wax comes in has a gauge on the side to check it with. All four journals had *exactly* the same width as the .0015" mark, and they were all very even stripes from one side of the journal to the other. (If the journals or the con rods had any taper, that would've shown up as a tapered stripe.) The specs for this engine are 0.0008-0.0025, so I'm smack in the middle of where I want to be. Any wear is going to cause that clearance to open up, and I've got a solid thousandth of an inch for it to open up before I make it out of the range I want to be in.

I'll putz around with little things here and there, but mainly I'll be setting up that lathe and taking some test cuts to get to know it. I've got to do my touch up on the crankshaft, and a couple other things, and then I can start test assembling everything. 

MORE Case and Crank prep...

It's been slow going lately, but progress seems to be taking place. I got lost in a lot of thought experiments and what-ifs, and (as is usually the case,) ended up right back where I started. So I cut the top off of the flywheel flange on the case, did a little bit of clearing on the inside of the case (some spots didn't seem to have more than a few thou of room for rotating parts), and used a Dremel to carve away a couple of channels for the engine mount in the back.

I also pulled all the aluminum plugs to get an idea of how much stuff was trapped in the case...

...And there was a lot! Much of that was from walnut blasting the case, but I found a good number of metal shavings as well. I'm glad I pulled the plugs... Next I tapped the holes for various pipe thread plugs, ranging from 1/16" NPT up to 3/8" NPT. I used a 1/2" NPT to tap a larger hole in the front for an oil temp sensor, because I've read bad things about the current temp sensor location (near the flywheel end of the case) actually reading quite a bit lower as a result of not being in a high-flow area. The new place is directly in the oil flow as it enters the oil pump, so it'd be hard to get a better reading than that!

Drilling and tapping the magnesium was quite easy, actually... in that the magnesium tapped without much force. There were a few places that I had to tap a few threads, then grind the tap down, then tap a few more, then grind, back and forth a few more times until the plug fit the way I wanted it to. There's one hole that I may have tapped just a little too hard and began to mess up the threads, but the plug threads in just fine and seems to have full contact along the entire length and circumference of the plug, so I'm going to leave it.

Now that all of the holes are prepped, I'll pull all the plugs out for another cleaning session. The last step will be to file a notch in each of the plugs so I can swage the case metal into those notches as a final insurance against the plugs working their way back out.

I forgot to take pictures, but I drilled the crankshaft for a couple more dowel pins. When I received it, it only had two, which was probably fine running the prop off the other end, but I'm not comfortable only using two running it with the prop hanging off the flywheel. So I drilled two more holes, reamed them, and tried to put the dowels in.... oops! One of the holes is *way* too loose! So I ordered a 11/32" drill bit blank, cut it down to the right length to be a dowel pin, and re-reamed the hole to be a press fit. This really isn't a bad plan anyway, as it keeps my flywheel aligned the same way every time it's reassembled, and the only extra work I'd have to do on a new flywheel is drill one hole slightly larger.

Upon reassembly of the flywheel and crank, I realized the flywheel is running about 60 thousandths out of true at the outermost edge. Not cool at all. So my next step is to remove the dowels and see if the crank face is out, but my bet is that somewhere along the way some burrs crept up and are keeping the crank from seating correctly. At least, I hope that's what happened... otherwise it's back to the machine shop.

Starting to prep for assembly.... sort of.

With my crankshaft back and polished, I was able to begin reassembling the gears onto the nose.  First the key:

Heat up the cam drive gear, and slip it on:

Next the spacer and the new brass distributor gear.

I'm working out the best way to attach the prop hub - I know what orientation, but if I want it repeatable to exactly the same spot, I'll need to build some kind of jig that locates off of the cam drive gear. I'm not sure how much that will matter at this point.

In the meantime, I finished walnut blasting the case, and decided to try it on the heads as well. They were somewhat improved, but I'll still try soaking them in carb cleaner to try and get rid of more of the carbon that's built up. Ignore the ape blocking part of the picture...

And below, a chamber in progress to show my future self that it was, in fact, having an effect:

Once everything was sufficiently blasted, I used Simple Green to clean the case as best I could. I'll admit, I focused a little more on the outside than the inside, but I think it's pretty clean all the way through.

Once clean and dry, I cleaned the outside with solvent and got ready to paint. Bob Hoover says three things about painting the case: Do it, do it black, and do it thin. When I got the case, it was painted a dark gray... over top of a dark blue. Two layers of paint, the outer one fairly thick, were definitely not going to help much with thermal transfer, and yet it still flew that way. In light of that fact, I took Bob Hoover's advice on two of the points: I painted it, and I painted it thin.... and I painted it red.

I figure the color is less important than the paint thickness, so I cut the paint with Naptha and brushed it on, making sure to run the brush over any areas that looked like they had extra paint. The end result is definitely brush-textured, and not exactly what I had envisioned, but it looks pretty nifty all the same... and more importantly, it's protected from corrosion and it's not likely to overheat from the paint. I'll put this in the oven like I did the cylinders to get the paint nice and hard... it makes a big difference!

Rust removal sucks, Cleaning sucks, Painting sucks...

....but they're all pretty necessary if this engine is going to last. So I've been doing due diligence to remove corrosion, clean up, prep, paint, and heat treat all my engine components according to best practices as instructed by Bob Hoover and Tom Wilson. There's a fantastic resource online at http://www.eaa691.net/images/pdf/VW%20aircraft%20engine%20building.pdf , which is a hundred some pages on what to do, why to do it, and what happens when you don't. I've been just collecting parts and trying to get everything ready for the first trial assembly. Tomorrow I'm taking my crankshaft in to have it magnafluxed, and if it comes back ok I'll start putting stuff back on it. First the woodruff key and the gears, then the prop hub. The next step will be installing the bearings in the crank case, and dropping crank and camshaft, along with some associated hardware, inside and making sure it all turns the way I want it to. 

I got new cylinders and pistons, measured them, weighed them, cleaned them *very* well, and painted them black to prevent corrosion and encourage heat transfer. 

The cylinder on the left has wet paint on it, the cylinder on the right has been cleaned but not painted yet. I made sure to keep track of the cylinders, and marked them after they were painted so I could keep track of them.

As it turns out, the cylinders I designated as "A" and "D" were both 4.490" between the two sealing surfaces, whereas cylinders "B" and "C" were slightly shorter at 4.487". That's right on the edge of too much difference, but because I've got less than a half a thousandth of difference between matching cylinders, I'm not going to send them out to have them machined. Instead, I'll put both of the "long" cylinders on one side, so the heads will be able to seal correctly, and either make up the difference between the two sides with a .003 shim, or just not worry about it.... for all I know, once it's assembled, other tolerances may stack up and either make it a larger difference or even it out. That's why I'm calling this a "trial" assembly, because there may be adjustments to make after it's all together. 

I'm working on removing some surface rust on my prop hub with vinegar. Most of it came off after soaking for about two hours, but I'll give it another shot tomorrow after work. I still have a fair amount of cleaning to do on the engine case, which is about the last thing I want to do... but it's going to be the thing that's holding me up in just a few days, I think. By next week, I hope to be posting pictures of a freshly painted, partially assembled engine.

Slow progress, but promising results!

A few months ago, my wife and I relocated to Rochester, NY for work, and to be closer to her family.

A small part of my new job is machining odd parts on a Tormach 1100, a 2.5 axis CNC mill. As a result, I'm now able to make *much* nicer and more complex parts than I could on my drill press in my shop back in PA. Which is really handy, since I ruined a couple of custom pieces taking this engine apart.

This is a two-piece housing that holds an oil seal. All of the information I could gather said that this should be attached in a way that prying and application of heat would allow its removal. All of that information was incorrect, as it turns out. Several #6 screws, hidden by RTV sealant and covered with paint, held this assembly on. I managed to bend it during my first failed attempt at removal, but even worse, I scraped the sealing face pretty bad with the screwdriver I was using to pry it off. As a result, I needed to replace both pieces.... and it just so happens I now have the tools to do so.

I didn't take a lot of pictures, but here's a shot of an aluminum blank next to one of the (almost) finished pieces:

I think the originals were turned on a lathe, based on the finish on the old parts vs the finish on the new parts. (Admittedly, I am not what most would call a competent machinist, so maybe I just failed to produce a quality part.) However, I think the new pieces will work out just fine.

According to the book I'm reading, "How to Rebuild your Volkswagen Aircooled Engine," Tom Wilson says the best way to clean the aluminum/magnesium engine case is with regular old soap.... with phosphate. Probably wasn't hard to come by when the book was written, but now it seems nobody sells it. I'm going to try regular old soap without phosphate, and see what happens. I'll be taking my crankshaft in next week to have it magnafluxed, and if it passes I'll be placing my big order for engine parts. My hope is that the engine will go back together pretty quickly, since there was no apparent damage and it ran ok before. 

As explanation for my apparent lack of significant progress, allow me to placate you with a picture of my son, who was born a few weeks ago, and has been eating up all of my time. Strangely, I don't mind....

Outer Wings (Part 4)

Continued from Outer Wings (Part 3)
With the plane upside down and wing reattached, I began by cutting the rest of my foam pieces to shape. It was during this process I realized that, during my fuel tank construction, I glued the bottom center section of foam incorrectly. By incorrectly, I mean that the foam was actually recessed below the airfoil shape for about half a square foot. I had problems fixing similar trouble spots before, but I've decided to try a different method with this area. I didn't take a before pic, but the after pic gives the general idea. The darker area is the low spot.

I decided to go ahead and sand the center section to the airfoil shape so I would have a solid understanding of where the foam was low. After that was accomplished, I traced and cut out a piece of foam 3/8" thick that was 3" smaller around the edges than the space that was low, and I glued that on. My next step will be to sand that to shape, then use micro to fill the outer band of the low spot, utilizing a straightedge while the micro is still wet to get a nice flat surface. This should work much better than my previous attempts, which were to glue foam over all of the low spot and sand it away. The problem was that the micro didn't sand as readily as the foam, and created high spots. 

With that figured out, I turned my attention back to adding foam over the rest of the bottom of the wing. Pretty straightforward, just make sure there's enough foam sticking up to sand away, and enough foam left after sanding that it won't flex after fiberglassing.

I came up with a simple (sort of) way to help hold long pieces of foam in place when they want to sag. First I cut off a piece of string about twice the length of the foam. Next I poked holes every foot or so in the foam I want to attach. The string gets secured at each end, by whatever means necessary. Finally, the string gets pushed up through each of the holes, then pulled until there's no slack. When you're finished, you've got plenty of string loops to help rearrange or secure your foam. I didn't end up using them to hold the foam in place, but they were very helpful for making small adjustments while the micro cured.

Top side:

Bottom side:

Continued in Outer Wings (Part 5)