Archive for the ‘Gear Legs’ Category

Gear Camber adjustment and Cowling Plugs

Here’s a comparison shot of the old axle and axle nut along with the new camber shims. I really like the looks of the Grove aluminum axle and axle nut. It should make installing the wheelpants slightly easier, too.

Here’s the axle, tire, wheel and shims installed. The tire almost looks like it’s tipping inward. I think this is just because there’s no weight on the wheels. I measured the camber at 9 degrees and this shim is 7 degrees. It almost looks like the wheel is now toe’d inward. I’ll have to check the alignment again before I fly it.

I’m really impressed with this axle nut made by the Grove gear leg people out in California. The holes line up perfectly for the cotter pin to slide through the axle.

This is the second step in the fabrication of my cowling inlet covers. In this step I laid out the plugs facedown on a plastic sheet covered with wax. I then glassed inside the plugs so that I wouldn’t increase the outside dimensions of the plugs. They fit the cowl inlets perfectly now. I think a layer of felt will make them fit nice and snug.

Long time, no posts…

Yes, it’s been a while since I’ve posted anything. I haven’t been in the mood to fly much now that we’re into the cold weather season. As of today (January 28, 2011), I have 61.4 hours on the plane since putting it back into service in June of 2010.

I’m still having issues with my comm radio so as part of the troubleshooting process, I made up this little harness. It breaks out the push-to-talk circuit and allows me to verify that my PTT is not the source of my radio problems. It was a bit of a pain to fabricate this harness, but it was still better than breaking apart my real harness to isolate the PTT. Bummer. the PTT was verified to NOT be the source of the problem. The antenna is the next step in the troubleshooting process.

Another nagging little issue I’d like to resolve is that I seem to have a twist in my airframe. My left aileron must be deflected upward slightly (forcing the left wing down) to maintain wings-level flight. A guy I worked with suggested that my elevator trim tab located on my right elevator could cause a twist. I bent up a fixed trim tab with the same deflection as I normally carry in level flight. I then taped this trim tab to the left elevator and left the trim tab on the right elevator in trail. Bummer. Still didn’t fix the problem. Keep looking…

A friend of mine has a Bridgeport mill. He offered to help me make some shims for my landing gear to adjust the camber. We fabricated 2 shims. One of them is 5 degrees and one is 7 degrees. I haven’t taken time to install them yet, but will probably do so within the next week or so. Frequent readers might remember that I had planned to machine the bases of some new axles I recently purchased from Grove. After I did the math and figured out how much material I’d have to remove from the gear legs, I decided it would be best to have external, separate shims.

This little guy almost ruined my whole darned day earlier this week. This gasket goes between the housing for my oil screen and the engine case, itself. If you click on the picture to enlarge it, you’ll notice that there’s a tear in the gasket… Well, the other day I was taxiing out for takeoff and my low oil pressure light came on. Argggh!. The pressure gauge confirmed the light so I shut the engine down immediately. I got out of the plane right there in the middle of the taxiway to see if I could see an obvious problem. The problem was VERY obvious!
I left a trail of oil approximately 1000 feet long between my hangar and where I stopped. With the help of a friend, we dragged the plane back to my hangar and found part of this gasket poking out from between the case and the oil screen housing.
A half-roll of paper towels along with copious quantities of Stoddard solvent later, I removed the oil screen housing and found this torn gasket. Not good. Lucky for me, we’ve got Firewall Forward located on the field. Those guys are really good to all us locals. They spend a half-hour looking through their boxes of gaskets trying to find the exact part and in the end ended up just giving me some gasket material to make a new one.
After having pumped all but 2 quarts of oil out of the sump, I decided I may as well go ahead and do an oil change. It had already been 20 hours since the last oil change, so I wasn’t too far away from my 25 hour interval anyway. Happy to find nothing in the oil screen and with the new gasket fabricated and installed, I left the plane on Wednesday night sitting with fresh oil and ready for a leak-check run-up the next day.
The leak-check was dry as a bone so I went and flew it for 0.8 hours on the Hobbs today. Came back and it was completely dry inside. I’m really fortunate that this incident didn’t ruin my engine, or worse, cause an off-field landing. If that little gasket had held out 10-15 minutes longer, I would have been airborne and might be writing a very different report… or none at all, if things really went poorly.
The moral to this story (i.e. the lesson I learned) is that no leak, no matter how small, should be ignored. I’d been chasing a leak from day one on this engine. I thought it was coming from the oil screen or the oil temperature bulb. I hockey-puckied the heck out of the threads and replaced the copper crush washers several times trying to fix the leak. It seemed to go away for a time, but had come back within the last 5 hours or so. I was putting off dealing with it because I’m planning a re-work of my oil system anyway when I install the spin-on oil filter and re-locate my oil cooler. Putting it off almost cost me dearly.

Since the upper and lower cowling were removed anyway, I decided to tackle a little project I’ve had in mind for several months. I’d like to fabricate plugs for the inlets on the front of my cowling. I’d like to make fiberglass plugs so that they fit nice and look nice. I taped off and waxed the openings in preparation for the fiberglass and resin.

These are some of my fiberglass supplies. The cloth was cut on the bias so that it will lay down better around all the curves. The roll of white is shelf paper. I find that it’s sticky enough to adhere to the part, but not so stick as to leave residue. The greenish roll is just just masking paper. The white tub is Partall paste wax that I’ll use as a parting agent.

I’ve laid up at least 2 layers of 6-ounce cloth in this picture. I have a tendency to make my fiberglass parts way too thick so I decided to start with 2 layers and add another later if it’s necessary. You’ll notice I didn’t cover the smiley inlet with the shelf paper. Instead, I relied on a few good coats of Rejex polish and a few coats of the paste wax parting agent. This approach almost bit me in the fanny. I had to use a little elbow grease to get all the epoxy off the paint. Lesson learned for next time!

Nothing was curing too quickly with our 40 degree overnight temperatures so I took advantage of the cured-to-tacky-but-not-rigid state of cure and rough-trimmed the plugs. Of course these won’t be very effective as plugs in this state so I plan to cover the openings with additional fiberglass. I plan to cover the backside of the plugs with felt so that they won’t scratch the cowling when I take them in and out. I know a lot of metal airplane builders hate working with fiberglass, but I kinda like little projects like this. If nothing else, it’ll be nice to have these plugs ready to go for this year’s flying season!
I had a visitor today. A gentleman from Australia is considering building a Midget Mustang. He’s 4-5 inches taller than me so he was interested in trying the plane on for size. Much to my surprise, he actually fit without much trouble. His legs bumped up against the fuselage fuel tank, and the headroom was a little tight, but workable. If he puts the fuel in the wings to get rid of the fuselage tank and if he goes with the M1A slider canopy, he’ll fit just fine.
Sorry it’s been so long since my last update. I’ve recently decided to stop posting to a different site and concentrate more effort on maintaining this blog on a more regular basis. I’ll try for weekly updates even if there’s nothing going on.
Happy flying. Rod.

Maintenance Day

I was off work this week from Thursday through Monday. I had a few things to do Thursday, so I didn’t fly until Friday morning. I went over to Greeley for breakfast. It’s always nice to run into a few old friends and chat over breakfast. I topped off the fuel tank at $4.21 per gallon (which is about 50 cents per gallon cheaper than KFNL) and headed home. I removed the upper and lower cowling and stated draining the oil for an oil change. I finally made it back out to the hangar on Sunday to finish the oil change. I’m hoping to have all the parts and pieces gathered up by the time my next oil change is due so that I can install a spin-on oil filter at that time. Wonder how long it’ll take me to rack up another 25 hours?

Since I have a wooden/composite prop, I need to check the torque on the prop bolts on a regular basis. I’ve decided to make it my policy that I will check them whenever I change the oil. Since I had the spinner off anyway, I decided to install nutplates on my spinner backplate. I’m doing this in anticipation of doing a dynamic balance on my prop. Normally, during a dynamic balance session, the machine tells you where to place weight on your spinner to balance the engine and prop installation. Without the nutplates, adding weight would require removing the spinner to drill a hole in the backplate to install a nut and a few washers as weight. I decided it would be simpler to just have nutplates positioned every 30 degrees so that installing or removing weights would be quick and painless… and I wouldn’t have to beat up my spinner taking it on and off multiple times as we dial in the balance. I used AN470 rivets (the round headed ones) rather than the flush rivets that are normally used for nutplates because I didn’t want to machine countersink the backplate–removing more material– and making it just a little weaker. The heads of the 470 rivets shouldn’t be a problem in this application.

Next up on the days’ activities was checking and adjusting my landing gear alignment. A friend suggested I should be using greased plates under each main tire to allow the gear to reach its natural point with weight on the wheels. I stumbled across these plastic cutting boards at Wal-Mart the other day in the aviation aisle. They’re really slippery and much lighter and less messy to work with than greased steel plates. Total cost for 4 of these cutting boards was about $16. And hey… If I ever host a wine and cheese tasting party at my hangar, I’m all set for the serving trays…

I added another (my last) 1/2 degree shim to help correct a left-turning tendency. It was also time to replace my first set of tires. I only got 40 hours out of the first set, but that amounted to 122 [really bad] landings. I was using the 11×4.00-5 tires made by Cheng-Shin. They’re cheap at about $35 each, but they aren’t known for being durable or very high quality. I had a set of McCreary Airhawk 5.00×5 tires and tubes laying around so I installed those this time out of curiosity. It’ll be interesting to see how the bigger tires change the handling and landing characteristics. This is the standard size tire for Midget Mustangs and the RV-series of aircraft. Now that I’ve had the little 11.00×4’s installed, these things look like tundra tires to me!
The McCreary tires are fairly cheap as far as tires go at about $52 each. Now that my alignment issues are pretty well fixed and my landing technique has improved, I think I’ll get closer to 100 hours of use out of a set of tires. I like the idea of the smaller tires because I think they look more in proportion to the size of the aircraft and they weight a little less and create a little less drag. This being said, however, if the larger 5.00×5 tires improve the handling dramatically, I’ll switch in a heartbeat!

Alignment and a Honda Hitch

At the suggestion of a friend, I checked with one of the local alignment shops for some throw-away shims. It’s my understanding that they use these shims to adjust the castor on old, solid axle vehicles and trailers. These are much more heavy duty than aircraft shims, but hey, 2 degrees is 2 degrees, right? I cut them down to size using my band saw.

This is my right landing gear leg and I’ve inserted 2-2 degree shims which tipped the top of the tire outboard. The picture is somewhat confusing because the tire has already been flipped and is showing wear on the outside of the tire instead of the inside. Trust me, it was the inside of the tire that was wearing–excessively, I might add.

This is the left landing gear leg. I’ve only inserted one 2 degree shim because while this tire was also wearing on the inside edge, it wasn’t wearing nearly as much as the right tire.

In the process of removing and replacing all the various tire, wheel and axle components, I discovered that my brakes were dragging excessively. I found that the shim between the caliper halves was slightly too thin for my brand new brake discs. When I tightened the caliper bolts down, the pads pinched the disc and caused some pretty good drag. I fabricated an additional shim out of some .032″ material. I’m happy to say the solution worked very well. My takeoff roll was shortened by at least 800′. I tease people and tell them that it also added 3 knots to my top speed!

I also installed this Curt Class III hitch on my CR-V today. I mention this because I credit my aircraft refurbishment experience with giving me the confidence to do this sort of thing. The local trailer place wanted $300 for this hitch and wiring harness plus another $150 to install it. I bought the same exact hitch and wiring harness on Amazon for a total of $185 including shipping and installed everything in less than 45 minutes. If I was married, I would try to spin this story into justification for owning $7500 worth of aircraft tools! But since I’m not, I’ll just give the manly, Tim-the-Tool-Man-Taylor grunt and keep moving…

Landing Gear Alignment

As this picture suggests, I have an issue with the camber on my landing gear. I’ve decided to try to shim the axles to adjust the camber. I’ll also flip this tire around to wear out the other side.

The left side gear leg is also splayed outward a bit, but not as much as the right side. I also rotated this tire in hopes of maximizing its useful life.

Looking at the front of the airplane, the landing gear camber issues are pretty obvious.

I decided to remeasure my landing gear toe and camber. The first step in this process was bringing the airframe to a level flight attitude. A friend of mine owns this taildragger tail lifting apparatus. He loaned it to me for the afternoon. Gotta get me one of these buggers. It sure makes leveling the plane a simple and quick task.

I used my Smart Level on the fuselage longeron to determine level flight attitude. This setup works very well. I set the Smart Level to beep when it reaches 0.0 degrees and then simply crank the tail lifting jack until I hear the thing beep.

I dropped a plumb bob from the center of the firewall and from the tailwheel spring attach bolt to determine the fuselage centerline. I then taped a length of unwaxed dental floss to the floor between the two centerline points. The dental floss is near the black carpenter’s square in this picture. The line in the foreground is just an expansion joint in the cement.

I clamped a straightedge to the outside of the wheel and then measured from the straightedge to the centerline. If the toe-in/out was set perfectly at zero,the measurement from the straightedge to the fuselage centerline would remain constant over the entire length of the straightedge.

I jotted down my measurements directly on the concrete floor with a fine-tipped Sharpie marker.

I drew out a simple line drawing and copied all my measurements to the whiteboard. Armed with all this information, it was a simple matter of looking up a few trig formulas to derive a number of degrees of toe in/out.