OX-5 Valve Guides

Since my friend Mark and I like working on old engines, and we were getting a little stir crazy from the Holidays, we decided to see how the valve guides would go.  It went extremely well, but a little background first.

An early method of replacing valve guides

The OX-5 cylinder is one-piece (no separate head) and is made from a single cast iron casting.  The guides are also integral to this casting.  This makes guide replacement more involved than more conventional ones that are removed when worn out and replaced with new.  Early companies like the one shown to the right and others like Miller made replacement guides.  The old ones had to be machined out, the hole threaded and then new ones screwed in.  This required careful fixturing to ensure the new guide was somewhat concentric with the valve seat.

Fortunately, there are better methods available today and the one I chose was to use guide liners.  The challenge, though, with liners is again keeping the lined guide concentric with the seat.

In most automotive applications, the guide can be machined from the seat side to accept the liner.  There are centering tools available to keep everything concentric.  With the OX-5 and other aviation engines, the machining has to be done from the valve spring side.  This is because the head and cylinder are integral and the valves sit at an angle, so the machining can't be done from inside the barrel.

Modified reamer with pilot and centering cone

Here's a picture of what I made to ream the guides to fit the liners and keep them concentric with the seat.  I first obtained a reamer of the proper size to fit the liners.  I had the tip ground to fit a long pilot that was pressed over the end.  I then made a cone with a  bushing pressed in the center. The cone sits in the valve seat and keeps the reamer concentric with the seat as it is being reamed.  Some pictures farther down in this post will make this easier to see.

K-Line valve guide liners

Several companies make liners, and the ones I chose were from K-line.  These liners have a spiral groove machined on the inside for lubrication.  Since the OX-5 valves have to be manually lubricated, this feature is perfect.   The liners have a .015" wall, or in other words, fit in a .030" oversize hole.  The nominal OX-5 valve size is .375", so the holes are reamed to .405"

Tooling required for liner installation

There is some other special tooling required as seen in this picture - probably best to describe them as I go through each step.












Step 1:  Ream the guide

Guide reaming

Here you can see how the reamer is inserted in the guide from the valve spring side, with the pilot going thru the guide and into the centering cone.  

Liner insertion

Step 2:  Insert the liner

A short stroke rivet gun and a special insertion tool is used to press the liner in the reamed guide

Liners after insertion

The liners are longer than needed, so after insertion they have to be cut even with the guide at both ends.

Sizing the liner with a carbide sizing ball

Step 3:  Sizing

The liners then have to be sized.  This does a couple of things:  Allows for proper fit between the valve and liner, prevents the liner from getting loose in the reamed guide, and allows for heat transfer between the liner and guide.  The sizing is done with several sizes of carbide "sizing balls".  Balls of various sizes are pushed thru the liner with a special tool and rivet gun until the proper valve to liner fit is obtained.  The dimensions of my valves required a .375 and .376 carbide sizing ball.  The ball can be run thru multiple times and each time, up to a point, the ID of the liner gets slightly bigger.

The liner is then lightly honed with a honing brush and the valve can then be checked for fit and proper sealing at the seat.

Finished installation showing internal spiral grooves

Now to the valves... As you may recall from my previous posts, this is a very low time engine.  My hope was to use the original valves, but I was unsure until I could get them cleaned up.  Well, they cleaned up great.

Original valve prior to lapping

Hard to believe, but here's a picture of an 86-year old valve that has not even been lapped yet.  Amazing!

Checking valve fit with bluing

Intake and exhaust valves after lapping

Now the moment we've been waiting for - is the liner concentric with the seat???

YES!  This whole process couldn't have worked out any better.  The seats and valves required no grinding, only a light lapping was necessary!

This was a relief, because if you're familiar with stock OX-5 valves, or see in the pictures, there is very little margin to do any valve grinding.

Every once in a while something just seems to come together nicely, and this was one of those times.  Thanks to Mark for all his help on this too.

Cleaned studs

 In a different, but OX-5 related topic, I got the engine studs black-oxided.  I bought a kit to do this myself and it is very easy to do.

The studs first have to be very clean.  I used a wire wheel to remove any corrosion.

Chemicals used for the blackening process

The parts are then put thru a 4-step process.  

1.  A cleaner to remove any grease and contaminates.

2.  A prep to make for a deeper oxide finish.

3.  The blackening process.

4.  A protective coating to improve the corrosion resistance.

Finished studs with black-oxide coating

I made a little basket to put the studs in, and about a 2 minute dip in each solution is all that's required.  Parts come out very nice looking and protected against corrosion.

























Back on to the wings soon, but still waiting on capstrip material.  So, I'm not sure what my next post will be on, so stay tuned!

Upper Wings #6

Well, I got everything done mentioned in my last post.

First, I made all the bracing wires, painted them, installed them and trimmed each wing.

 I then got the nose ribs installed - lots of them!  38 on each wing!  That's Chuck Connors as the Rifleman on the TV in the background.  Chuck often keeps the hangar free of outlaws.













Then, the trailing edge ribs.  These go a lot quicker, not as many since this is a 4 aileron airplane.  

The upper wings are notched above the rear cockpit to make getting in and out easier.  That is why the 4 ribs at the root of the wing are shorter than the rest.

Next, I have to install the capstrips.  I had to order the 3/16" by 5/8" spruce material.  I doubt it will be here before Christmas, but that's OK.  Our Son is coming home from the Army, and there will be lots of family events going on.  I brought a couple of projects home to keep plugging away as time permits:  I'm restoring the ignition harness (I'll create a post on it) and I pulled all the studs from the OX-5 crankcase and applying new black oxide for corrosion protection.

Merry Christmas everyone - hope you all have a blessed holiday season!

Upper Wings #5

OX-5 cylinders with fresh nickel plating

To start things out, I got all the cylinders back from the plater.  Now all of them have a nice covering of nickel plating.  You can refer to a post I did this past October that explains the Watts nickel plating process used on these.

Next on the OX-5, while I'm waiting on the babbitt work, is to finish up the cylinders.  They don't need much.  The guides are a little sloppier than I like and will be sleeving those.  Stay tuned for a post on that.

Rib glue blocks installed - 1/4" triangular spruce.  The shiney spots
is varnish that has been applied that will be underneath the fittings.

Mostly it's been lots of wing work.  The pictures pretty much tell the story...

All the ribs glued in place

Varnish applied and all the fittings installed

I can already tell that doing both wings at the same time will be a big time saver.  I'll be adding the drag/anti-drag wires next, then the trailing edge and leading edge ribs.  Stay tuned to the same "Bat Channel" for an update in a week or so!

Magneto Magnet Charger

Mark and I finished our magneto magnet charger (magnetizer) this week, and it is a thing of beauty!  I need to point out, though, that Mark did most the work.  He had the last couple of weeks off, did all the machining, and he and a neighbor made the beautiful oak cabinet.  It looks like a vintage piece of equipment, and with both of us liking old things - it's perfect!

This was not our invention.  In fact there are numerous specs on the Internet for devices like this.  Even old Dyke's automotive manuals from the early 1900's have plans.  We did have certain criteria:  we wanted a magnet charger that would generate about 12,000 ampere-turns - enough to saturate the magnets on just about any magneto magnet.

Our design has two 6 lb. coils of 18 ga. copper magnet wire wound on 2" steel cores.  The coils are mounted on a steel base that allows the flux to flow un-inhibited between the two.  Adjustable pole shoes at the top contact the magnets that are being re-magnetized.

Electrically, this unit runs on 115V AC (another reason we chose this design).  DC current has to flow through the coils, so a full wave bridge rectifier is used.  We installed a line fuse, added a light to know when the unit is energized, and an ammeter.  When energized, it draws about 10 amps.

Here's a picture of one of the Berling magnets being charged.  We couldn't have been more pleased with the results.  The magnet initially had a pull force of 6 lbs.  after charging, it had a pull force over 30 lbs.!  We got the same results when charging both magnets simultaneously, indicating we are getting adequate saturation.  The unit was only energized for 5-10 seconds.

An important thing to know, a keeper has to be used when the magnet is transferred from the charger to the magneto.  A keeper is just a steel bar, about the same cross-sectional area of the magnet, placed across the poles.  This allows for a highly-conductive path for the flux to flow.  If it has to jump an air gap, even for just a second, the strength of the magnet is compromised.  We tested this several times - a charged magnet would again pull about 6 lbs. after the keeper was removed.  

A better way to re-charge the magnets, and not mess with a keeper (which can be a challenge on the Berling because of how the magnets mount) is to re-charge the magnets on the magneto.  That way there is no transfer from the charger to the magneto and the keeper is not necessary.  The pole shoes on our unit allow for this, and can be changed if I'm doing a different shaped magnet.

So with this done, I can finish up the Berling overhaul.  I had it mostly complete, but came across a problem.  When I assembled the armature, I noticed it had a slight wobble to it.  I put it between centers in my lathe, and it had about .010" runout at the bearings!  I suspect it may have been like that all along.  My main disappointment, though, was this was an armature I had rewound.  I've got several Berling spares, so I grabbed another armature, put it between centers, and it was perfect.  The coil looked good and checked out fine, but I refuse to use an armature with 100-year old magnet wire on an engine that only has one magneto!  I have lots of coil winding experience in my previous work as an engineer and am aware that the polyester and other insulating materials used on modern magnet wire is far superior to what was used originally.  So, I sent it off for re-winding.  When it comes back, I'll finish up the magneto and put in a post on the overhaul.

I'm also making great progress on the upper wings and will update everyone on those soon.  I'm giving final exams Monday and Tuesday next week to our future A&P Mechanics and will then have a month off over Christmas break.  Unless we get bitterly cold like last winter, I should be able to get a lot done!

Until next time...