Saturday, December 24, 2011

Cable Splicing Clamp - Complete

This piece is the adjustable part of the clamp to hold the cable secure while the splice is formed.  On Rich's clamp this piece is made from 1/2" round stock.  Rather than buy another 36" piece of steel for a 3/4" long piece I decided to make this from some of the 1" x 1/2" bar stock. The other advantage to this is it will be self aligning while clamping the cable.  The first step was to drill the center hole for the 3/8" bolt and 2 end holes for the 1/4" bolts.  I used the center drill to start the holes then drilled through with a 1/8" drill for a pilot hole.
The 3/8" bolt hole was drilled with a size Q drill for tapping the 3/8-24 threads.  For convenience I used the same size drill for the other 2 holes.  They just need to clear the bolts so the piece slides easily without turning.
The idea was to notch the ends with the band saw to make assembly easier.  What I hadn't thought enough about was that the three holes are not on a line.  That's why I like making drawings before I start cutting metal.  The solution was to cut to the end holes from 2 sides leaving a tab to keep the bar from turning.  In the end it's how I would make another one.  I'd just move the hole over a little so the tab is closer to the bolt.
The next step was to cut the Vee at the top center for the cable loop to set in.  I then removed some of the metal to give the bar a pleasing shape.  OK you could live without that but come on Craftmen take pride in their work.  The shaping was finished with files and the belt sander.

The adjustment bolt was threaded into the bar with the thumb wheel o
installed.  Some Locktite was use as well as tightening the bolt so it bottomed out.
The head of the bolt was cut off.  A thin washer was added as a bearing.
The end of the bushing was flared with the pointy end of a body hammer.  The hole in the base was chamfered  to allow the peened end of the bushing to flare out and lock the base to the block but still pivot.  I found, in use, this didn't hold well and fixed it with a 1/32" deep counter bore in the bar with a 9/16" drill instead of the chamfer.  Then peended the bushing as shown, rotating the pointy (not round) hammer to peen it in multiple spots.  Much better.
When I went to install the holding plate I found I had not tapped the holes squarely.  I didn't want to make another one so I clamped each end in the vise and bent it slightly to get the bolt aligned.  It may be crude but it worked perfect after lots of thinking to make sure I bent the ends the right direction.

Before assembly all the fabricated parts were  grit blasted for a nice finish.  Keep it lightly oiled with Corrosion-X and it should last for years.  The 2 slider bolts were cut to leave no threads sticking out of the plate, and installed with locktite.

I like it!  Thanks for the loan Rich.

Friday, December 23, 2011

The Fun is in the Doin'

If you've read my postings for a while you've probably noticed I'm not very orderly in working through the project from start to finish.   I tend to work on what ever I have parts, materials, tools ,or ideas for at the time.   When I helped my dad build the Fly Baby back in the 60s we were very methodical.  Pete Bowers wrote the plans/manual as a set of step by step instructions.  You start on page one of a chapter and just check off each task as you go.  When every item is checked off you have an airplane, actually a very cool airplane.

As much fun as it was working with my dad on the magic of building that plane you would think I would be more orderly in my current projects.  I'm not because what I learned from that process was that each little item was a project in and of it's self.  Each had it's own knowledge required, it's own materials, tools and methods.  To some extent it didn't matter so much the order things were done as it did that each was done.

By focusing on each small task, enjoying it, and taking pride and satisfaction in it's completion building an airplane is very easy, a lot of fun, and rewarding.  Finishing and flying the airplane was great but just one more little task or adventure just as each flight in it has been since.

By enjoying each saw cut, each hole drilled, each tool made, each little assembly, each flight for all the joy it contains, the Fun really is in the Doin' Not Just in Being Done.

Merry Christmas and a Fun New Year!

Cable Splicing Clamp - Holding Plate

 The presser bar pushes the cable loop and thimble securely into this plate, which does the actual holding while the loose end of the cable is secured.  It is made from a piece of 1/4" x 1" x 3" mild steel bar stock.
 The hole Locations are transferred from the base plate with duplicating punches to assure the bolts will align well.  The center hole is not drilled it is just a reference point.  The 2 bolt holes are drilled with a #3 drill and tapped with a 1/4" - 28 UNF thread to accept the 1/4" bolts.
 The opening in the center is to hold the loop of cable and the thimble so the hole is tapered to match the thimble.  From the AN100 drawing the sides slope 1:3 so rather than move my nice square table, and have to realign it, I made a hardwood block 1" x 3".  The plate is set on top of it and  held with the wrench while drilling.  The bolt is just there as a stop to keep the block of wood from sliding.  Think of it as a bench dog.  The holes are drilled through with a #2 (3/16) center drill.  Before drilling at the angle I drilled with just the tip about 1/32" deep 5/16" apart.  I chose the 3/16" drill because I plan to use this with 1/8" and 5/32" cable but this would allow up to 3/16" cable to set nicely in the round groove.

 All of the cutting and drilling is done with the bottom side of the plate up (visible).  The edge of all the cuts are more sharply visible on this side and the saw work is all being done by eye.
 The entrance slot and the relief for the thimble are cut next without ant taper.  This is just to get the shape.  From the top side you can see the angle of the drilled holes better.

 The band saw was used with the same 1:3 block to taper the thimble relief by placing the block next to the blade for good support.  The saw is being used more like a powered file than as a saw.  You just gently saw into the plate until the blade just kissed the cut edge.

I also tapered the entrance hole by turning the block 90 degrees to the blade and sawing along the edge of the cut.  Again you could tilt the table but that would have taken longer then making the cuts.  This came out really good and the cable fits perfectly.

The two 1/4" bolts were threaded down to 2-5/8" from the head.  It doesn't show here but they were cut off to leave 1/4" of good threads to screw into the plate.  The center bolt was threaded to give 1-1/2" of threads.  The head will get cut off from it later.

Thursday, December 22, 2011

Cable Splicing Clamp - Clamp Base

 This part is made from a piece of 1/2" x 1" x 3" mild steel bar stock from Tractor Supply.  The 1/2" pivot hole is centered 3/8" from the edge.  The two 1/4" holes for the slider bolts are 7/32" from the ends and 1/4" from the same side as the pivot hole.

 To make sure the bolt heads don't catch on the vise in use the bolt heads are recessed into the base.  An easy job with a milling machine.  I created the same result with the band saw.  You need a sharp blade and a guide to control the location of the cut and the keep the bar parallel to the blade.  Just put on a noise cancelling head set and a good book because this needs to be done slowly.  Forcing the bandsaw will cause the blade to wander.  A careful cross cut and the ends are done.

  The ends have a 1/4" radius and the big curve is just tangent to both ends and the middle of the bar.  The shape was rough cut with the band saw.  The final shaping was done with the belt sander and and a mill file.  All the corners were softened.  I think I'll grit blast all the parts when I'm done just to even up the finish.  I don't think it will make sense to paint such a tool. I'll just need to keep it lightly oiled.

Wednesday, December 21, 2011

Splice Clamp Support Block

 When I grind with the belt sander I am careful to set the table and miter fence as square as I can get them.  Then to minimize uneven grinding I make a couple passes and then rotate the part 180 degrees and make a couple passes.  If you use light pressure you can do a very good job of it.  The center for the pivot hole was then located on one end of the blocks.
 Before drilling the hole down the split between the blocks I used the bandsaw to create a guide hole to help the drill go straight down the center.  The saw cut was made about 1/32" deep.
 The centers for the screw holes were laid out 1/4" from the ends and 3/16" from the sides.  The blocks were then clamped together and the screw holes drilled with a #26 drill (tap drill size for 10-24 UNC threads).  To control the drill better I like to mark the hole with a spring loaded prick punch and then improve the mark with a center punch (fits the drill better), and start the hole with a center drill.  In this case I used a #2 (3/16) center drill.  Once the holes were drilled through I drilled a clearance hole from the screw head side 9/16" into the block, a little past the center split.
 The holes were tapped for 10-24 threads.  By working in the same direction that the screws go, the clearance hole helps keep the tap going straight in.  With the holes tapped the blocks were separated and the screw holes countersunk for the flat head set screws.  I used stainless Allen head screws so I could torque them easier than Phillips or slotted screws.  The screws are arranged so 2 install in opposite corners on each side.

 With the blocks screwed together, the pivot hole was drilled.  The hole was started with a #3 center drill ( 1/4") until it the hole edge was about 1/32" deep.  It was then drilled through with a 1/4" drill following the saw cuts.  Unless you own a drill vise or finger wrestle regularly with Superman, the wrench lets you get a good grip on the part being drilled.
 The hole was then increased at the start with a #4 1/2 center drill (3/8") about 1/16" deep at the hole edge.  The shape and short length of center drills minimize how much they can wander. The hole was then finished with a 25/64" drill to give clearance for the 3/8" bolt.  The steel bushing from Lowe's is 3/8" ID x 1/2" OD x 1-1/2" long.I need 9/16" sticking out the end for the 1/2" support piece and washer between the parts.
 The 1/2" hole for the bushing was drilled 15/16" deep after opening the start of the hole a little more with a #5 center drill (7/16").
 To get this block to clamp the bushing the mating faces of the blocks were ground down until there was about .002" gap with the bushing installed in clean parts.
 The screw holes and the busing interfere so a notch was filed in each side of the bushing the allow the screws to clear it.
The parts were then cleaned in MEK to get rid of cutting oil, etc. A little Krazy Glue was used on the bushing to secure it to the blocks.  The screws were secured with Threadlocker and tightened to squeeze out the gap between the blocks.  The edges of the block were then ground to remove the little bit of the screw heads sticking out past the edges.

Monday, December 19, 2011

Cable Splicing Clamp

 To form the looped end on the control cables using a 5 or 7 tuck splice method, or on bracing cables using the solder wrap method, the cable end must be held firmly while doing the work.  To hold the cable end you need a Cable Splicing Clamp.  The clamp is held in a vise while the other end of the cable is pulled snug during the splicing operations.  The clamp at right is from a 1930s Nicholas-Beazley catalog K.  The tab on the right is clamped in the vise and the wing nut on it is tightened to keep the clamp from rotating.  The wing nut at the top is used to move the center slider to clamp the cable securely in the curved jaws.  Back then a gallon of clear dope sold for $1.85.

 This picture from "Aviation Mechanics Made Easy" Vol. 4 pg. 526 (c1942) shows a clamp in use  on a control cable.  It also shows the other tools needed to form the splice, a marlin spike, rawhide mallet, and wire cutters.  You also need a hardwood block to pound against when tightening up the tucks.
 This clamp is from a 1944 Supply Division catalog pg. 75.  That same gallon of Berryloid dope was then $2.65 although a new Sensenich prop. for a J-3 was only $35.
 The one I've decided to use as a model to make my own is one I borrowed from Rich Wilbur who is restoring 2 WACO NINEs.  He made this one in A&P School so it seemed like something I should be able to copy.  I've had this for a year but couldn't find a piece of 1" steel to make the holding block on the vise end.  While making some tools for the Cessna 140 project I realized this block could be made from 1/2" x 1" mild steel like the clamp base piece.  All I need to do is screw 2 pieces together to make a 1" block.  In the end this is probably a better idea since it solves the problem of how to install the bushing which holds the block and clamp base together.
The 2 block halves were cut 1-1/2" long, ground smooth on one side, and squared up on the ends.  The Base piece is also cut from 1/2" x 1" mild steel 3" long.  The Jaw piece at the end is the same size but cut from 1/4" thick mild steel.  The pivot bolt is 3/8" - 24 UNF x 3" long.  The 2 Slider bolts are 1/4"-28 UNF with a grip length of 2-5/8".  The threads need to bottom out in the Jaw plate.  The ends get ground off smooth and staked in place.
The first part is the Knob for tightening the clamp to hold the cable.  It's a round disc of steel 1/4" thick, 1" in diameter, with a 3/8" - 24 UNF threaded hole for the bolt, and knurled on the edge for a better grip.  I started by drilling and tapping the hole in the end of a piece of 1/4" x 1" mild steel bar stock from Tractor Supply.  It's easier to drill and tap the bar than the finished disk.
A 3/8" hole was drilled in a piece of oak to use as a pivot to grind a nice round end on the bar.  The 1" end was then cut off the bar.  By making 2 45 degree cuts and then a square cut across the bar the piece is close to the desired finished (round) shape.
By using the same process but with the board clamped in place and moved closer to the belt in small increments the knob was turned to a nice round shape.  I have no way to knurl the knob so instead I used the band saw to cut into the edge of the knob about 1/32'' deep. Cuts were made dividing the edge into quarters, then eighths, and then 16ths.  It makes a nice grip surface.  The top and bottom edges were filed to soften the corners.

After using the Splicing Clamp to make about 10 cables, for my Fly Baby, I decided I needed to stop and make a larger, easier to grip, tightening wheel.  I originally made the wheel from the same 1/4" x 1" bar stock used for some of the parts.  It seemed clever and would work fine with flexible cable.  With the non-flexible 1x19 cable it was just too hard to get the cable tightened against the thimble.  You could do it but it took a lot of wiggling the cable while turning the wheel.

I decided I needed a wheel closer to 2" in diameter with nice big knurls for a good grip.  I also wanted to keep it 1/4" thick to have a reasonable number of threads.  If it wears out I may need to make one from 3/8" thick steel.
 The only piece of 1/4" steel I had was on some tools for making wire ferrules for the WACO internal bracing wires.  I decided it would be fine with a 2" hole in the base since I just clamp the base to my work bench.

I located a pilot hole for the 2" hole saw then used the saw to draw a centerline to layout a pattern of holes for the knurls.  It certainly took the guesswork out of where the center of the holes should be.

 I center punched a pattern of 12 holes, pilot drilled them with a 3/16" drill and finished them with a 5/16" drill.

 To round the edges of the holes, it makes more comfortable knurls, I countersunk the holes with a 1/2" center drill, steeper flutes.  Then I lightly countersunk then with a 1/2" twist drill.  It really makes a nicely rounded edge to the holes.

 Back to the 2" hole saw to cut out the wheel. I cut half way from each side and when it got close just pounded it out with a light hammer blow.  I didn't want to risk this 1/4" slug flying around.

It's looking like a thumb wheel.

 I cleaned up the outside radius with the belt sander and the chamfered the edge at 2 angles, sort of like with the hole edges.

 The remaining burs were cleaned up with the small sanding drum on the Dremel tool.  It needs to feel good in your hand and no sharp edges.
 The hole was tapped with a 3/8" fine thread to spin on the center bolt.
I had a little trouble getting the 3 bolts apart since I had put Loctite on the threads and cut off the head of the 3/8" both after tightening it in the clamping bar.  A little heat took care of the Loctite.  I greased the threads and the pivot with Molykote to keep the friction low.

A much nicer wheel.