Thursday, July 5, 2018

Head Games

I walnut blasted my heads a few months ago, and I didn't oil the valve seats well enough to keep them from corroding a little. Nothing major, but enough that I needed to do more than lap the valves in. What follows is a good example of wasted time, wasted money, and a whole lot of frustration. In short, if you're looking to do valve seat work, skip the next two miserable paragraphs.

I looked into getting a valve seat grinding setup, and wow, are they pricey! So I found a site that sells just the stones for about $14 bucks apiece and set about making my own self-centering stone holder. I cut the head off of an old exhaust valve to use as a pilot, drilled a hole in a chunk of aluminum, which I then heated up with a propane torch and dropped the aluminum onto the exhaust valve/pilot. After it cooled, I used a collet to hold the assembly in the lathe and turned threads on the aluminum portion to match the grinding stones I'd purchased. I then took the 45° stone for the intake seat, screwed it onto my new tool, and placed the tool back in the collet, set up my top slide to the right angle, and used a diamond-tipped dressing tool to grind the stone perfectly concentric. I wanted to make sure I didn't impart any weird tilt to the tool while I was using my drill to spin it, so I pushed a piece of 1/4" fuel line over the end of the tool and connected the other end to the drill. This seemed to work ok, except that the rubber hose allowed the tool to vibrate and caused some chatter unless I was careful not to apply very much pressure.

I worked through all three stones, re-angling them with a diamond stone on the lathe between valve seats to make sure the angle stayed true. Once I got to the 45s, I started checking the seat width. It wasn't until then that I realized I was grinding non-concentric valves. Whoops. I took a break to do some research, and came across a company called Neway. It took me some time to build up the nerve to pay for the tooling needed, but in the end I caved and picked up the stuff. After cutting a couple of the seats, I can say with confidence that was the right decision. Here's a picture of a valve seat that's had the 15 and 75 degree angles cut in it with their cutters.



It's a little tough to see, but the red line is what hasn't yet been touched. At its thickest, it's about .053, and at it's thinnest, it's around .018. That's pretty bad! The good news is, with the Neway system, I've been able to recut the seats concentric with the valve guides, and I'll be moving on to CCing the heads shortly.

This is what all of my valve seats look like now:



That's an exhaust valve seat, so the width is about .01" wider than the intake seats. They all look a lot more concentric now, though, so it's time to put new Dykem on the valves and seats and try to fit them together. I wanted to check for even contact between all the valves and seats, but I didn't want to remove any material. I decided to use toothpaste instead of lapping compound, because it's still abrasive enough to remove the Dykem but not enough to carve material away from the seats.




With all the valves and seats marked up, I put toothpaste around the contact area of the valves, placed them in their respective guides, applied a little pressure and rotated them 90 degrees back and forth a few times. I was really impressed; every single one of my seats showed clean, even lines around the entire 45 degree face, and every single one of my valves showed even contact around the mating surface. Consider me sold - Neway cutters are the way to go!

The last thing I did was clean up the toothpaste as best as I could and hose down the valves and seats with WD-40. Tomorrow I'll bring the heads to work and clean them up again in the parts washer, and then I can assemble the valves and springs into the heads for good.





Saturday, June 30, 2018

One step forward....

Actually, no steps forward for a long time. It's been pretty quiet on here for a while now. I finished assembling the short block on the engine by adding the flywheel seal, oil pump, etc. and bagged the whole thing to keep humidity out while I worked on the heads. I took a break to work on some Christmas presents on the lathe, and then I broke the lathe, so that needed repair... after that I started trying to recondition the heads myself. I don't think that was a mistake; the way I went about it was a little less than ideal, which caused more problems than it solved. That's all for another post though; this weekend I'm back at the fuselage, and making some serious progress... backwards!

Two years ago, I received the canopy I ordered. There's a long story of assumptions, misinformation, betrayal, and pretty poor customer service, but the bottom line is I've spent the last two years trying to figure out if I can even use the canopy or if I need to buy another one. It's a Dragonfly canopy, but the folks who made it insisted on molding it out of thicker acrylic than the design calls for. As a result, it bends a lot less than I anticipated, and trying to force it to fit has been difficult. Along the way, I realized how uncomfortable the seat is, because of the angle the seat back rests at. All it needs is to lean a few inches back to be much better.

So the plan was to cut out and replace the existing crossmember and seat braces, leaving the plywood shelf in place.


Here I've got the line marked, and just in case the sides got any squirrelly ideas, I put a clamp around the old crossmember to keep the dimensions stable. I clamped a straightedge on my line and used a utility knife to score through the plywood. I removed a chunk from my new line forward to the old crossmember. 


Looking good so far. The next step is to cut and fit the new crossmember and glue it in place. I just need to look underneath to mark the angles, and...


Whoops. There's an unexpected turn of events! The longeron doubler doesn't go quite as far as I thought it did. This just became a much bigger project.......

So I'll be replacing the plywood after all. I don't have any pieces that size left, but I can still cut the new crossmember and put it a little further forward. I had hoped to gain 3.5", but I ended up settling for 2.75". It didn't take long to fit the new member, which installed quite nicely.


With that in place, I cut out the old crossmember and seat supports, sanded and planed the remaining bits of wood away. 

I cut and fit new seat members, glued them in place, and left them to cure. 


This was enough for now. I'll still need to add all of the gusset blocks, but my goal this weekend was to get the plane to a point where I could sit inside and take measurements on total height required above my head as well as instrument panel height. I'll do that tomorrow when the glue's had more time to set up. Once I get those numbers I can finish the templates for the canopy frame, which I'l work on when I come back down in a few weeks. In the meantime, I'll keep working on the valve seats.

Saturday, October 21, 2017

No turning back now...

Got my LocTite, and had a few free hours tonight, so I finished the crankshaft buildup by torquing the connecting rods to spec. Then I gooped up all of the head studs with Permatex Aviation 3H and installed those in the case halves. 




I got everything covered in moly grease, dropped in the cam lifters, crankshaft, camshaft, cam plug, and stud seals, then put the case together and torqued everything down just as if I was sealing up the case for real. 



I checked free rotation the whole way through, and man, is it nice and smooth. All the gears mesh up just fine, no weird noises or rough spots. With that, there was nothing left to do but tear it all down so I could add grease and sealer and put it back together one final time!



Got moly grease on the cam lifters, which in my case are hydraulic. Using moly on them really helped them stay in place; a big plus on aircooled VWs, since they want to fall out when you try to put the case halves together. Dropped in the crank and camshaft, then gooped up the cam plug with 3H and stuck that in its place. (Apparently this picture was actually before the cam plug was installed.)


Next came the excitement - spread 3H on the other case half, mate them together, and put all the nuts and bolts in.



I gave it one more free rotation check once everything was torqued and ready to leave, and sure enough - smooth as you please. I'm gonna have to find something else to complain about now that the crankshaft is doing what it's supposed to do. One final thing I did before I sealed the case up was check my end play at the flywheel. I've got three shims in between the first bearing and the crankshaft to act as a thrust bearing, and the remaining end play is shown below. I think I'm supposed to have it at around 0.005", but I'll have to check on that. I'll order a shim to put between the flywheel and the first bearing and call it good.


Wednesday, October 18, 2017

Crank Buildup... Again.


So, when I said earlier that the case was "torqued to spec" and that the crankshaft "didn't bind...." Turns out I lied. I didn't have two nuts on... and it turns out that those two little nuts caused a big problem.  Once I had *all* of the hardware on and torqued, the crankshaft stuck... pretty bad! I ended up doing a lot of digging, and it turns out that the piece that used to be the prop hub, which still provides a bearing surface, was the problem.

I started by trying different clocking orientations - pulling the hub, heating it up, rotating it slightly, and putting it back on - and I did find one position that was very close to perfect. However, it still had a sticking spot, and when I put a dial indicator on it, I could see why - while the hub was only out of concentric by about .0003, there was a single spot, like a lobe, that was more than a thousandth of an inch high. Now, I have a lathe, but I'm not confident enough in my abilities to do serious engine work. Nevertheless, I'm not willing to pay a machine shop another hundred to polish a single bearing surface into spec. 

So I chucked the crank into the lathe and set up to knock the lobe down with some emery cloth held in my tool holder, so I could just hit the high spot.


Once I thought I'd gotten close, I used some medium and then fine emery cloth to get all of the tooling marks off. Then I pulled the whole thing off the lathe and assembled and torqued the engine to spec again.



..........??????!!!!!!!!!!!!!!!!!!!!!!!

Rotates freely. Smooth as can be. I was pretty excited! It's still got contact across the whole bearing, too, so I didn't just turn it down so far it doesn't touch anything. (To give you an idea, I think I took about half a thou off of the bearing before I started with the emery cloth... so really, very long process for a very small amount of material.)

I cleaned the crankshaft up, re-lubed the connecting rods, and started to assemble them. Unfortunately, I can't find my LocTite to save my life. I think I left it in PA when I used it on my landing gear.


Yes, the connecting rods are pointing in wrong directions - that's just so the nuts are easy to get to. I couldn't just leave it all like that, so I went ahead and worked on setting up the distributor assembly. Because of the type of distributor I have, I don't think the orientation of the distributor drive shaft matters in the least. However, just in case I'm wrong, I oriented everything the way the book says to, marked it with red dykem, and put a holding screw in place to keep the distributor aligned correctly. I've gotta get a couple of new screws for that, though... these two are looking pretty buggered up.


I intend to assemble the crankshaft, then install it and the camshaft into the case, along with the correct end play shims on the flywheel, torque the case to spec and check free rotation one more time before the final assembly. If it all checks out, then I'll install the lifters, cam plug, and whatever else I'm forgetting, then put sealant on the case and bolt it all up for good. There's still a lot left to do, but this feels like a big turning point in this whole process.

Monday, October 16, 2017

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.

Sunday, August 27, 2017

Fit so nice, I made it twice....

Actually, it was the wrong material, so I kicked myself a few times and bought a new flywheel. This time, a *forged* flywheel, not a *cast* flywheel. Had I the sense to do more research ahead of time, I'd have only made it once. Nonetheless, the new version is around 300% *less* likely to break apart during flight.

That's version 2. Same dimensions, but machines a lot more like 4130 than the first one.


In this blurry picture I'm pointing out the locating step for the flexplate. That way I know it's concentric. I did the same on the inside for the prop extension:


Now that this is finished, I was able to start test assembling the crankcase. First, the connecting rods on the crankshaft:


Drop the crank assembly into the case and add some nuts, torqued to spec:


It still rotated freely after it was torqued, so that was a good sign. No rubbing or clearance issues so far. The next step was to add the head studs and check the piston deck height. I painted my head studs to help avoid corrosion:


And then I added them to the pile.


I added a cylinder and piston, and started taking measurements. I used a .030" shim under the cylinder, which is how the engine came to me. I set up my dial indicator and rotated the crank to TDC for that cylinder.


Zero'd up the dial indicator (though the photo makes it look off);


Using a piece of steel rod I had laying around as a straightedge, I measure deck clearance + rod width at 0.428" or so.


The rod I used measured 0.314", which means my clearance distance is 0.114". That's a lot more than I want! VW specs are between 0.040" and 0.080". I went back and checked, and the old pistons are the same as the new ones, and the old cylinders were within a couple thousandths of the new ones. That means that this engine was assembled wildly out of spec.... which shouldn't be a surprise, but it was. And means more work; removing the shims brings me down to 0.084", which is out of spec (and 0.024" more than I really want.) That means I'll have to chuck each cylinder up on the lathe and turn it down to what I want. 

Unless...

...unless the heads are also anomalies, and have a much smaller chamber than normal heads, in which case the cylinders need to be extra long.... Bottom line, the new priority is get the heads reconditioned and blueprinted so I know what kind of setup I need.

There has been nothing straightforward about this engine. Armed with the knowledge I've gained from this process, I believe the next engine I assemble will be from brand new parts that I know the details on.

Monday, August 7, 2017

...And flywheel solutions!

I removed all the dowel pins from the crankshaft, which wasn't super difficult this time around... I think my holes are a light press fit, rather than the super-tight holes that were there originally. I'm not sure if that'll cause problems down the road or not; they are still a press fit, so load should (theoretically?) be transferred just as effectively.

The flywheel face on the crankshaft seemed to have zero runout when sitting in the crankcase, but there were a few problems with how I was taking that measurement that could have absorbed imperfections... so I decided to throw it at the lathe and check runout by painting the face with red dykem and scraping a tool along the face. The goal was to avoid removing any material, just rub the dykem off, and see if it was a gnarly edge on a dowel hole that was causing issues, or if the face itself was not perpendicular to the axis of rotation. I thought I took a picture of the result, but apparently this was another instance where my phone shut off instead of taking a picture... that's been happening a lot recently.

Anyways, the dykem was scraped off of about half the face, and the other half the dykem was still there; it made almost a perfect half circle of red and a half circle of steel. Now, the crankshaft was out about .0005 on each end, and I failed to document whether it was out the same direction at the same point in rotation; so when I did the math, I had to assume worst-case of the crankshaft being out a full thousandth of an inch. Even so, the pattern was much too extreme to blame it on a misalignment of that magnitude, so I turned a couple thousandths off the entire face. When I re-attached the flywheel, it was only out about 1 thousandth of an inch as opposed to the 8 I had before, so I put the dowels back in and put the flywheel back on. I put the whole thing on the lathe as an assembly, because I have to do a little more work on the flywheel.

Now to the part I have pictures of! The final flywheel is going to be two parts riveted together. The inside part will be turned from the original flywheel, and the outside is from a much lighter flexplate (which basically just positions the ring gear and transfers the load from the starter.) I cut the inside out of the flexplate on a CNC mill at work, since it was too big to turn on the lathe.



I also cut the outside off of the flywheel on the mill, but left it oversize so I could finish it on the lathe.




I could have programmed the mill to cut a circle, but I wanted to use a rotary table to get a true circle on the flexplate, since I can't touch that up on the lathe. Once I was set up to do that, it was just easier to do the same with the flywheel.

Once the flywheel and crankshaft assembly were on the lathe together, I started working towards the final shape. There's a step on the outside of the flywheel that needed to be turned flat with the rest of the face, and then a new step needed to be cut out from 5" diameter outwards to accept the flexplate. I've got the whole thing turned flat, and I used some red dykem to help me visualize where that 5" diameter will be.




It's been a little tough to find time to work on this stuff, but I think I see the light at the end of the tunnel. I have a few more parts on order, and once they get here I should be able to begin the reassembly process... which should be a pretty quick process, given how much documenting and adjusting and tweaking I've done *before* started to put it all together.