Tuesday, April 26, 2011

Tail Wheel Spring Back On

The spring parts have all been grit blasted, primed, and painted.  Along with new hardware I fabricated new rubber pads for the spring mounts.  I used 1/16" sheet to cut pieces and laminate pads to fit.  I'm not sure I have the correct durometer rubber since I've found nothing on what rubber was used to make the originals, long since gone from this plane.  We'll see how they last in service and get harder rubber if needed.  By laminating them with contact cement I was able to make them fit around rivets and things like that better than using solid pieces.  The aft spring clamp uses a "U" shaped piece of rubber 1/4" thick.  By laminating it I was able to glue the pieces together to form the "U" to fit very well.  I'm still waiting on a couple parts to assemble the tail wheel.

Monday, April 25, 2011

Tailwheel Parts

All the parts for the tailwheel are cleaned, inspected and painted. The tailwheel spring mounting bracket at the tail of the fuselage is cleaned up and painted. Once I have the rest of the new parts needed, all this can go back together. The tailwheel steering arm and cam assembly is one of the parts for which there seems to be no information on repairing it. The Scott factory riveted it together, so no internal parts are available. Once you un-rivet it, it's a very simple design. I'll write a short explanation before putting all this back together.

 There are 2 bushings which act as stops for the arms and prevent the covers from being crushed when the assembly is riveted together.  I could have drilled out the rivets, but it seemed easier to make new bushings.  The bushings are 3/8" long, 1/4" outside and 3/16" inside diameter.  I have some 1/4" x .028" wall 4130 tubing for the Waco project so I clamped a piece of it between some wood blocks and carefully drilled the ID to 3/16".  To cut off a short piece I used the end of the 3/16" drill to hold the end being cut off.

To square the ends of the bushing I ground one end before each cut was made by holding it against the miter gauge and spinning it while gently pushing it against the belt.  After cutting the bushings slip each one on the drill bit to hold the drill level. Use a gentle finger pressure to push the cut end against the belt while spinning it on the drill shank.  Spinning evens out any slight alignment error and a light pressure allows you to take off less than .oo1" in a cut.  With a little care the 2 bushings can be made within .0005" of the 3/8".
A light deburing after grinding and the bushings are ready to rivet in.

Saturday, April 23, 2011


 It's been raining so I can't paint the tailwheel parts.  Instead I've selected the windshield from the never ending pile of parts needing some work.  The Skylight windows and the Windshield were sealed in with RTV at some point, what a mess.  The window frames were easy to clean up because they're aluminum and stronger solvents like MEK can be used to clean off any residue.  The plastic windows can not be cleaned this way.  The Internet was useless for finding a solution.  Nothing out there seems to be safe for plastics.
 I finally realized I'll just scrape off the RTV with a razor blade and pocket knife and then polish the areas to remove as much of the RTV as possible.  The correct way to mount the windshield is to glue a 2-3/4" wide strip of 1/16" thick SAE F-55 Felt to the edge of the windshield and push the windshield into the retainers.  I still don't know what glue to use to hold the felt to the plastic.  All this allows the windshield to move as the plane flexes, which all structures do under load.
Along with RTV some of the edges had residue from friction tape as well as the original glue used to hold the felt.  The important thing is all this is hidden in the retaining strips so it doesn't have to look perfect. By holding the razor blade or knife at a shallow angle so it shears off the RTV without cutting into the plastic it works fine.  You don't want to cut the plastic in a way that might cause a future crack so you don't want any sharp edge scratching the plastic.  Using the curved area of the pocket knife blade solves this problem.
With the razor blade you need to hold it between thumb and fore fingers to give it a slight bend and then work in the middle of that bend.  That way the sharp corners can't scratch the plastic.  The razor blade works fine on flat or convex (outside) areas.  I use the knife in other areas.  The razor is nice because instead of re-sharpening it you just throw it away and get a fresh one.  The important lesson is never use RTV.  Clearly I could buy a new windshield for $250 and skylight windows for $35 each.  It's nice to be able to use parts which are perfectly functional instead of replacing them.

Thursday, April 21, 2011

Tail Wheel in Pieces

I've removed the tail wheel now that the plane is back on the mains.  I think I'm shocked at the neglect.  It has been so long since being greased that the grease had dried out back to paraffin.  Grease is made by melting paraffin wax and adding #30 oil to the mix and letting it cool.  It takes a very long time to dry out this bad in a closed space like the wheel or arm and cam assembly.  Fortunately the plane came with 2 tail wheel assemblies.  Like all steel parts the springs were rusty but they cleaned up fine.  One tire is dead and the other is serviceable.  The wheel bearings are all shot.  I'll save one set as an example of just how bad bearings can get.  The inner races on one wheel are like furrows in a plowed field.  I've found new Timken A4050 bearings on e-bay for about $55 shipped so hopefully they really are new as advertised.  The rest should be a matter of cleaning, painting, greasing, and new hardware.  I'll have to fabricate new rubber pads for the springs.  I have some 70 durometer rubber which should work fine.  The tubular rubber piece which goes around the bolt in the spring holes is fine so that's good news.  I should have everything ready by the time the bearings arrive.  This is the same tail wheel we have on the Fly Baby so any serviceable spare parts will always be welcome.

Wednesday, April 20, 2011

Brake Hoses

I needed to replace the dead brake hoses at the rudder pedals. The parts are cheap and the process is easy enough. Aeroquip has a sheet you can download which shows how to assemble 303 hose and fittings. The EAA also has a nice video. I realized after I got the parts that I don't own a mandrel for assembling 1/4" hose. It's easy enough to pay a local A&P shop to assemble and test the hoses or buy ready made hoses. I wanted to assemble the hoses. Everything I read on line said that the do it yourself mandrels you can buy (about $80) are too small a diameter to hold the hose open well during assembly.  They make them undersized to fit well in used fittings for disassembling old hoses. The solution was obvious, make my own mandrel.  I got out my box of drills and used them as plug gauges to find the inside diameter of the hose fitting, 0.170" goes, 0.172" is a no go.  McMaster-Carr has 36" sticks of drill rod for about $3 so I selected 0.168" rod to make the pin for the mandrel.
 I cut off a piece of rod about 6" long.  By chucking it in the drill I tapered about 3/4" on one end with the belt sander and then polished it.  For a holder I got a 1/4" AN 815 union out of the recycle bin as well as an AN818 Nut and AN819 Sleeve.  It took some light pounding to drive the pin through union.  The ends get squashed down when the fittings are tightens installing the lines in use.  This same idea was used to with the nut and sleeve to squeeze the one end to hold the pin in the union.

The tape on the hose is so I can see how long I need to cut the other end of the hose to get the same length hose as the old hose.  It also allows me to see when I'm done that the hose is still fully in the socket.  For a small hose like this it's easier to use a socket wrench to screw the socket onto the cleaned up end of the hose.  I use the belt sander to get a nice clean square end and blow the debris out when done.  Remember the socket has left hand threads, snug it down and back it off 1/4 turn.
My camera caused this picture to rotate. I've turned off auto rotate so it won't do this again.  The important thing here is I use some assembly oil, it's supposed to be slicker, to lubricate the inside of the hose and the threads on the nipple so it doesn't gaul the socket.  After you tighten the nut and nipple on the mandrel oil the mandrel pin.  You'll need to clean the the oil off the mandrel before you do the next fitting because the nut has to be tight enough not to spin while screwing the nipple into the socket. I also rinse out the hose when all done with a little mineral spirits.  The oil is green so it's easy to see when you've rinsed it clean.  A couple tablespoons of spirits will clean from each end.

Push the mandrel into the hose and hand thread the nipple into the socket as far as you can so you're sure the threads are engaging well.  Then just wrench it in to leave the right gap, 1/32" - 1/16", between the nut and socket.
The fittings add 1-1/16" to the length of the hose so wee need to cut the other end 1-1/16" short of our 11" length needed.
With a short hose like this it's easy to look through it to make sure there is no bulge or cut flap in the inner hose.  These 2 came out great.  Now I just need to pressure test them and we'll have 2 excellent "Owner Produced Parts" to install and so note in the log book.  Good fun!

Tuesday, April 19, 2011

Springs and Things

These are the flap return springs.  Once the paint has dried well they can go back in the plane.  They were a mess but still sound.  I dipped the spring ends in primer and let them dry before priming and painting the rest.  It takes a few light coats to get paint into the center of the coils, but with them stretched like this it worked fine.
The skylight window mounting flanges needed a little work.  The lip on the inside for the headliner was smashed so I made this tool for straightening them.  I used a piece of aluminum angle and shaped it to the inside shape of the lip.  I rounded it and tapered it at each end so I could work it into smashed areas.  With some gentle work they came out great.  Now I just need to find out how to install the windows so they never leak

Monday, April 18, 2011

Pulleys & Cables

Saturday was a rainy stormy day, perfect for re-greasing all the pulleys.  All the old grease was dried on the bushings.  Some MEK and a q-tip swap cleaned them up nicely.  I re-greased them with the Molyshield grease I got for the engine.  It's a #2 grease with 5% Molybdenum Disulfide to reduce friction.  There are a lot of pulleys in a C-140.  All the bolts, etc. are being replaced so I kitted everything for each pulley in it's ziploc bag.

I cleaned all the cables with MEK.  It was amazing how much grit had accumulated on the old grease.  After cleaning they were inspected. One aileron cable had some broken strands so it will be replaced.  The rest are all OK.  I coiled each in a ziploc bag and oiled them with Corrosion-X.  I did not oil the turnbuckles, they need to be oil free.  Galvanized control cable is originally oiled to prevent corrosion.  I'm sure it dried out ages ago.

I also reassembled the control tee and cleaned up the 2 return springs on the flap bellcrank.  I'll repaint the springs with epoxy primer and epoxy paint.  I believe it is a little more flexible than enamel and therefore may last a little longer before the springs start to rust again.  If it weren't so expensive I'd paint springs with white epoxy primer only so any future rust would be obvious at the start and could treated before any pitting starts.  I really can't afford a quart of primer just for that.

Saturday, April 16, 2011

Cabin Touch-up

I've got the control cables out of the fuselage and started cleaning and inspecting them. One rudder cable has broken strands and will have to be replaced, good-bye $70. Mostly they're just caked with old dry grease and dirt. I'm cleaning them and re-oiling them with Corrosion-X since they were originally oiled to prevent corrosion. The turnbuckle barrels clean up nicely in carburetor cleaner. The threads have accumulated a lot of dry oily crud. They should not be oiled but they need to be clean to adjust them easily, much better. The trick of using a piece of soft flannel cloth to find broken strands was not needed on the one rudder cable, it was obvious to look at.

All the little guards to keep the cables on the pulleys were originally plated. Not much of the plating was left. I cleaned them up, epoxy primed, and painted them. I used a silver paint to look more like plating but once the interior is installed no one will ever see them. Hopefully the paint will last better than the plating. I've also learned that zinc-chromate is a nice primer but needs to be covered with some kind of paint to seal it. All the steel parts with just light coats of zinc-chromate are rusty. Even zinc-chromate will work if you layer up enough coats to seal out moisture. I think it's easier to just paint them with a good enamel over the primer and get on with it.

There were several places in the fuselage cabin area where some extra cleaning and re-priming was needed. Those are done. I think I'm ready to start putting the controls back in.

Tuesday, April 12, 2011

Working In The Fuselage

Now that the plane is back on the gear I've started taking out the control cables and pulleys. All the brackets have some rust and the bushings need grease. I think I need a stand to hold the tail up while I'm working. Trying not to slide into the tail while using wrenches is to much work for an old guy. The Aileron Cables look good but they have so much old grease on them it's hard to tell for sure. I need to clean them up and then measure them and check for broken strands and rust. I also need to find the cross connection cable for the ailerons in the pile of extra cables I have. I must have enough cables for 2 planes since all the other cables are still in the fuselage.

Sunday, April 10, 2011

On The Gear Again

After a rainy day yesterday it finally cleared this afternoon. The last wedge went in fine. This would have all been easier using a 7/16" universal socket. It's shorter than a socket and a universal joint, all 1/4" drive. There is not much space to work.
As the sun sets it's nice to have it starting to look like a plane again. Now I can get the remaining control cable pulley brackets out to clean up, re-grease the pulleys and check all the cables. All the brackets are rusty so I'm sure I'll find more problems but they should all be minor.

Thursday, April 7, 2011

Gear Back On

The gear is finally back on. I still have 3 rivets to install on the skins around the gear. They need some modified bucking bars to get them in and I need to crawl in the fuselage to figure out what is needed. I haven't wanted to crawl in until the plane was off the stand. The rivets are also easy to get at with the gear on. I still need to install one of the wedges and torque the 2 attachment bolts.Someone had modified the skin on the left side to get at the wedge bolts better. I did those 2 wedges first without realizing how much easier it was with some room to work and being able to see what was happening. The right side has not been modified and is tough. On top of that the slight amount of primer I put on the gear, 2 coats, prevents the wedges from going in as far as they did in the factory. This requires longer bolts which adds to the problem. I did not repaint the wedges for that reason and wiped off any primer on the channels with MEK. The wedges are a very shallow taper so it doesn't take much to make a big difference. I got each wedge lined up with the bolt hole and then started the bolt in to assure it would be lined up free to turn it in. Then I pounded the wedge in tight per the Cessna 100 Series manual and tightened the bolt. Once I was convinced I had the wedge as far as it would go I checked the bolt with the mirror and found I had 1 - 2 threads through the nut plate, perfect. I don't trust that the wedges are in as far as they should be since I used AN4-10A bolts and the parts list shows AN4-5A. The bolts I removed were AN4-6A, but even then 1/4" longer bolts leaves me believing the wedges can go in further. I'll recheck them as we move forward and also after we start flying just to see if they can be wedged in further. I quit when it got dark and I got tired. It's still very cool to have the gear back on.

Wednesday, April 6, 2011

Bucking Bars

I've started riveting the panels back over the gear leg openings. I had gotten some new bucking bars from Aircraft Spruce. When I went to use them I realized they mostly have sharp corners , (chamfered but not smooth and round), edges and some rough areas on the castings that need smoothing. Any edge etc. which might come into contact with something while bucking the rivets needs to be smooth so it won't scratch anything it touches. I'll spend a couple hours rounding all the edges and smoothing any areas which might touch something. You don't want everything smooth or they're hard to hold while bucking the rivets. I'm not really complaining about Aircraft Spruce. On something like these panels where you have to reach in through a hole to buck the rivets it's easy to touch the structure while bucking the rivet. If all this were being done by 2 people in nice open space it could probably be done without any worry of scratching things.

Tuesday, April 5, 2011

Engine Assembly Greases and Sealants

I now have the rest of the greases and sealants to start assembling the engine. There are more listed in SIL99-2B but the work has already been done, plugs & breather elbow, or they don't apply, fuel injection, turbo charger, etc. The tube of Molyshield grease came from The American Lubricants Company in Dayton, Ohio, (800-543-9720 no website). They take credit cards and were happy to sell one tube. It's a #2 grease with 5% Molybdenum Disulfide for use on the valve stems and gear teeth. . The small tube of Dow Corning Molykote G-n paste came from Skygeek. It's for the cam shaft lobes and tappet faces. I've seen on line videos showing this stuff being slopped on the lobes and tappets. The directions on the tube say: Apply a thin coating. For more effective application, burnish into metal surfaces by rubbing on with lint-free cloth. Remove excess. May be applied with short, stiff bristled brush. Not everything you find on line is correct. I only hope I don't post incorrect info or at least someone will point it out when I do.

Monday, April 4, 2011

Trim Wheel & Fuel lines

I was concerned that I would not get a good seal on the old fuel lines. There was evidence people had worked to seal the fittings to stop fuel leaks in the past. The best solution would probably be to make all new lines. Instead I ordered some DEL 37 deg. fitting seals from Aircraft Spruce. They're about $2 each and I won't know if they work until I can leak test the lines. They're soft aluminum caps which fit on the end of the fittings (shiny ends on fittings). They intall easier on new fittings, but by lining them up squarely on the fitting and then slowly turning the fitting while gently pushing down with your finger tips they go on well. They stay fairly well but will fall off a new fitting so be careful they are very fragile. They're so soft I'm sure they will seal very well. I also cleaned up and re-greased the bearings for the elevator trim tab wheel. The wheel is straight forward to re-install using the procedures in the 140 Operation Manual or the 100 Series Service Manual. The service manual does not have the cable tension spec for the 140. It did have one piece of information I could not find in the Operation Manual. There was no spec for oiling the chain in the Operation Manual because none of the control chains are supposed to be greased or oiled. It would seem they were more concerned with it picking up dirt if oiled than reducing friction. Many slow moving parts are better not oiled. When I cleaned the chain in some MEK I was shocked how much grit washed off it from someone oiling it in the past. The chain didn't even look dirty. If I ever detect any rusting I'll use the Corrosion-x to lightly oil it, but for now it is cleaned and moves very freely.