Tuesday, May 28, 2013

OX-5 Exhaust Manifold

 I've been working on making exhaust manifolds for the OX-5.  I don't need them for a long time but John Gaertner needs a set for the Jenny project, so they moved to the front of a long line of tasks.

The whole story is on my OX-5 blog.

 I finally have the first shell half successfully formed.  It came out very well.  Check it out in my latest OX-5 posting.

Wednesday, April 24, 2013

Fin Forward Brace Wire Fitting

 The brace wires on the stabilizer cross.  The wires at the front of the fin and fuselage go to the rear spar on the stabilizer.  The wires at the rear of the fin and fuselage go to the front spar on the stabilizer.  The fittings for the wires on the lower fuselage longeron are welded to the longeron. The fittings for the stabilizer and rear of the fin are bent tabs bolted to the structure.  We'll get to them in another posting. The fitting at the top front of the fin sets on the top tube and is held in place by the clevis pin welded into the front spar.  The brace wire angles back 15 degrees and down 23 degrees.  I used the string to double check my math for the angles.

 The fitting is made from .095" steel.  It can't just be bent in place because bending it would damage the tubes.  Instead I bent it around a 3/8" pipe nipple.  I used the nipple because I'm going to use a piece of it for a spacer under the fitting.  The spacer is needed because of the weld bead where the pin stick through the top tube.

The fitting was bent cold with a hammer until it matched the paper gauge I made to check the angles.

 The ends of the nipple were cut of and the cuts cleaned up on the belt sander.  The tube was split by slipping it over a piece of dowel to make it easier to hold.  Again the cut surfaces were cleaned up on the belt sander.
A 5/16" hole was drilled to fit the pin and the underside was ground out to provide clearance for the weld.

 The spacer fits nicely over the tube providing a nice mount for the without grinding out the fitting to fit over the weld.

The pin was left long so it could be cut to fit all of this.  A new cotter pin hole was drilled and the end of the pin cut off to a nice length.

I need to make up all the brace wires.

Tuesday, April 23, 2013

Tail Surface Welding is Finished

 The last parts to weld to the stabilizer are the fittings which hold the front spar of the fin to the front spar (or as WACO called it, the Front Beam) of the stabilizer.  The rear spar goes into the tail post of the fuselage.  The bolt which holds that together also holds the rear of the stabilizer.  When it's done there is no adjustment to the fin for rudder trim or to the stabilizer for elevator trim.  They solved those short comings on the Model TEN (GXE).
A fitting is welded to the stabilizer spar 7/8" apart  on each side of the fin and a bolt passes though it all to hold it together.  The fittings are 3/4" wide made from .0125" steel.  The 1/4" bolt hole is 15/16" above the top of the stabilizer spar.  It's taken some research and the help of Frank and Rich to find all these dimensions since most are missing from the factory drawing of the tail surfaces.
 To carry the loads better and to prevent distortion to the fin front spar I welded a piece of 5/16" x .028" tube into the bolt hole.  The rear spar mounts in a way that a bushing would not help and welding it in would just cause more problems than it's worth.
The rear bolt was installed and some string used to hold the fin in positions to tack weld the fittings.  I tacked them at each end, and in the middle.  With the fittings tacked I bolted a 7/8" spacer tube between them to help assure the spacing didn't change during welding.  It worked great.

 Welding was easier with the stabilizer tipped by setting it on some bricks.  Welding these on warped the spar a little.  It shrunk on the fitting side.  The trick of heating the back side of the spar and letting it cool took out the warp.
It all fits perfect.  With the bolts in the fin is square to the stabilizer.

My first tail surface is sand blasted, ready for priming.  This is so cool to finally have the tail surfaces made.

I've go some modifications to make to my blast cabinet to do the other parts and the prime them.

Tuesday, April 16, 2013

Wing Strut Attachment Fittings Finished

 When I made the fittings I used 3/16" pilot holes for the 5/16" bolt holes at the ends where the wing flying and landing wires attach, as well as for the 3/8" spar bolt holes at the other ends.  I didn't drill them to finished size at that point because I didn't want to buy large bolts to ruin during welding and I wanted to use small cheap pieces of tubing for the spacers.  The drilling was no more difficult after welding then before.  I drilled them out with center drills because the steep angle on the cutting edge helps them center better on the pilot hole.  The 3/8" hole was then drilled slightly (.002") larger with a letter V drill.

 I've decided to go back to using Zinc Chromate for primer except where I need to protect the finish for applying fabric.  There are wood blocks around these fittings for attaching the fabric so they're well protected.  The epoxy primer is much more easily scratched than Zinc Chromate.

I finished them with Black enamel, for the same reason, and then baked them in the sun.  I still need to paint all the small fittings and form the drag and  anti-drag wires.

Wednesday, March 13, 2013

Wing Fittings Welded

 I finally got a warm day with no wind so I could set up my tent to weld the fittings.  The fixturing worked great.  I tacked the strut fitting to each of the spar fittings and then did each weld.  I welded from one edge of the spar fitting, around the end of the strut fitting back the the edge of the spar fitting.  It took a while to get the 3/16" strut fitting hot enough to start the weld and then when I got about 1/3 of the way on the second side I really slowed down to get enough heat into the weld.

Before welding the first side I used a square to make sure the strut fitting was square to the spar fitting.  The fixture plate holds it square in the other plane.  They didn't move once I started welding.

They came out great and fit the spars with no distortion from welding so all the little tubes worked to hold the spacing

Tuesday, February 5, 2013

Aileron Pulley Bracket P/Ns 7033 - 7035

The ailerons on the NINE are cable operated.  This bracket holds the bracket with the aileron pulleys in the lower wing.  The pulley holder pivots on this bracket.  The cables run along the front side of the rear spar from the control stick to the pulleys and from there up to the aileron.  The bracket mounts on the front face of the spar.  The pulleys are mounted above this and parallel to the spar.
The plate # 7035 goes on the aft side of the spar because the lower bolt is actually below the spar.  The factory glued on a little block of wood but the load is carried through this plate.  Because of the odd shape and lack of a flat layout on the drawing I suspect this is another part they bought as war surplus and modified to fit by grinding off one side.  You can see the 2 bolt holes in the rear spar just to the left (inboard) of the strut fitting.

Like all the steel parts I make, I start with a galvanized template.  The material is cheap and if you mess up just bin it and make another one.  To make the actual parts I start by using the template to center punch and drill the holes in the sheet of steel, then scribe the cut lines when I'm sure the holes match the template.  If the finished holes don't match the template I can often use the steel for some smaller part if the lines haven't been scribed or cut. This method is of locating the holes is so accurate I can usually stack up a half dozen or more parts and put bolts through all the holes. The parts are cut out on the band saw and the edges ground to the line with the belt sander and drum sanders.  I always round corners and deburr every edge.  Sharp corners add weight, sharp edges don't hold paint and they draw blood.

I need a form block to bend the part into a U-shape.  I'm cutting it from 1/2" thick bar stock with  a 5 degree angle to allow for spring back.  For steel this thick (.090") the block needs to be 11/16" wide to get a part with 3/4" between the legs.  The block is 4" long so cutting oil is important to protect the blade from overheating.  It also cuts faster with the oil.  I had just brazed up a new blade so the cuts were done before the Patsy Cline album album on my i-pod.  Noise cancelling earphones are a must.

With the sides cut to a fairly straight line at 5 degrees, the next step is to grind the sides smooth with the belt sander.  The part quickly gets too hot to hold so I cool it regularly by setting it on the end of my vacuum cleaner hose.  The fast moving air cools it nicely.  If you cup your hand over it to form a tunnel it cools even faster.

After grinding it smooth, if you very lightly grind perpendicular to the grinding you leave a very smooth finish.
Next the first hole is located and drilled.  In thick metal I start the hole with a center drill and finish drilling through with a regular twist drill.  The hole location is much easier to control with the center drill.  The other trick is to mark the hole location with a prick punch and then improve it with a center center punch so the drill centers in it better.
The second hole is duplicate punched using the part template to assure the holes line up with the parts when clamping everything with bolts.

The holes are drilled and the sides ground.  The drawing doesn't specify a bend radius so I used a 1/16" radius on the 2 corners.  I ground and filed the corners until they nicely fit my 1/6" radius gauge.
I made the backing block slightly off center so I could hammer close to the bend because of the .090"steel I'm bending.

I made the backing block slightly off center so I could hammer close to the bend because of the .090"steel I'm bending.

It all seemed like a good idea but I couldn't keep it in the vise when I pounded on the part to bend it.  It worked fine when I clamped it in the side of the vice, but there was no way to clamp it and bend the second side.

Back to the drawing board.  I made a longer backing block from 2 pieces of 3/16" steel left over from making the form tool for the false nose ribs.  I probably could have used one piece of steel but you have to pound so hard on such a wide bend that I felt better with 2 pieces.  I didn't want it to bend instead of the part.  The part and blocks are assembled the same as the first one.

It all clamps in the vice much better and it was easier to hammer on the top of the vice.  There is a work piece protector on the jaw of the vice to keep the bracket from getting scratched.

The part is now re-clamped in the blocks to form the second bend.  Which now can be easily done on the top of the vice just like the first bend.

It came out great.  Because there is a right and a left part you just have to pay attention to reverse the blank before making the first bend.

With the part bent the hole in the second leg can be drilled.  Because the legs are close enough together I started the hole with a center drill.  It doesn't accidentally enlarge the first hole.  The center drill is too short to make it all the way through so I finished it with a regular twist drill.

The parts are ready to paint.  I probably should make the pulley holder while my brain is on the subject.