Ch. 5 - Landing Gear mounts - Part 2

Main landing gear mounts bushings (aka: LMGAB) (15.0 hrs)

Let me just state the obvious up front: “If you are in a hurry to complete and fly your Long EZ, DO NOT even think of machining your own parts!” (unless you are a machinist).

With that out of the way, I just spent a very enjoyable (and long) three days making my own landing gear bushings out of raw steel bar stock. 

Turning a useless, slightly oxidized bar, into very useful, shiny new bushings, has been a slightly frustrating, but mostly rewarding experience. It might be of interest to know that in the process of making the LMGABs, I had to throw away two partially formed ones, because I accidentally cut them too deep. Nevertheless, Miss Lathe and I have since developed a much needed understanding of each other’s limitations. 

This Spring has been unusually warm, so I have taken on the habit of working in my shop/garage with all doors open. Since I’ve been spending most of my time in there, I have become the object of many of my neighbors’ curiosity, as they stroll by my house. One of the regulars is Ralph, a 15 year old boy who lives two doors down, who has taken an interest not only in the plane, but also in the machining of its metal components.

Last night he walked in as usual, full of well thought out questions, just as I was working on my last bushing. So, I decided to let him experience what it's like, by putting him to work on the lathe. He followed directions very well, and did a great job boring the hole in incremental drill sizes, up to the 3/8” final dimension. He seemed to have had a good time; we’ll see if he ever stops by again.

Ralph running the lathe

The steps involved in making LMGABs are exactly the same as those I showed in the videos of “Tooling up” - Part 3, so I’ll skip the description and go straight to the end pictures here.

"Quadruplets... I'm so proud!"

“Tooling up” - Lathe issues

Reading the last post over, I didn’t like that I introduced my latest acquisitions just as I had purchased them, dirty and all. Looking back at their picture now, I can hardly recognize them. So, I’ll open a little parenthesis to show them to you once again as they are now, after a complete tear down to the last bolt, and a total rebuild.

Lathe all cleaned up

She's a beauty, ain't she?

Working with this lathe has not been as straightforward as I expected. Its small size introduces idiosyncrasies that combine to make precision work as much of an art, as it is a science. And that’s not a good thing! I am still happy with it, but if I were to do it again, I think I’d lean toward a heavier duty lathe.

I still have a lot to learn, especially in choosing, and using the cutting implements correctly. At this time, I can bring a piece of steel down to maybe 3 thousands of an inch oversize consistently, but I have to finish it down to size with sand paper, to smooth the groovy finish the cutter leaves.

The more I practice though, the better the finish that I have been able to get, up to a point. I just don’t enjoy turning 4130 steel all that much, and it would seem 4130 steel doesn’t like being turned by me either, certainly not as much as aluminum.

One of the design problems that I have encountered with my lathe, is that the speed at which the automatic feed moves the carriage along cannot be changed, and it is determined only by the gears being used. Because of this coupling (good for cutting threads), increasing the chuck’s rotational speed also increases the longitudinal speed of the automatic feed, and produces a lot of excitement, but unfortunately not a better finish. 

So, I have been slowing the feed down by hand-cranking the carriage (longitudinally), which is a big no-no for smoothness of finish, but it is still better than what I’ve been getting with the auto-mode to date.

I also have an occasional tooth skipping issue with the auto-feed, that I have been able to reduce, but not eliminate, by throwing some lithium grease at the problem, but I think I have finally narrowed down its cause. This skipping has ruined a few parts already, by happening during delicates cuts, and forcing the tool to dig deeper into the part. 

It would appear that there’s not enough contact in the rack and pinion mechanism, creating hesitation in the feed, as well as the skipping. The cure should be to mill down the top of the auto-feed casing, to allow the geared unit to ride higher in the carriage, and engage the rack gear more fully.

While on the subject of modifications, I created a small cover for the hand-cranking mechanism. These greasy gears were totally exposed to the metal shavings, and would routinely attract and capture them like a magnet, then chew them over and over, causing wear and tear, as well as difficulty in hand cranking.

Housing with gears removed

Drilling hole #1

Drilling the same hole through the cover and spacer (without moving the drill)

Threading by hand with help from the drill press

First screw is in!

Process repeated twice more

Finished cover

This mod was cheap, using only leftover parts, and has performed flawlessly, and I no longer have to worry about cleaning those gears again.

By the way, that vise no longer looks so big anymore, and it is a real pleasure to use.

“Tooling up” - Lathe and Mill

The decision to make my own metal parts has cast a whole new light on the composite aircraft construction method. Lately, I've found myself elbows deep studying machine shop manuals, and steel milling techniques. I feel like I have fallen into a parallel universe, where the words epoxy and fiberglass are devoid of any meaning. 

In keeping with the FAA experimental certification motto though, I have been putting the capital “L” in Learning, but unfortunately only the small “r” in recreation so far. So it is, that after a lot of metal working self-education, I decided to finally purchase my very first metal lathe. 

The lathe, for those unfamiliar with it, is a machining device used to make cylindrical parts with cylindrical features. A vertical mill on the other hand, is used to work on parts with flat surfaces, like rectangles, bars, plates, etc.

Months of looking on eBay and CraigsList, left me feeling like every good deal had already been had by someone else, and I was literally about to head over to Harbor Freight to purchase their 7”x10” lathe (7” swing over a 10” long bed), one of the smallest, when my wife suggested I take another look at eBay. Unbelievably, I found not only a bigger lathe (7”x14”), but a mill too, plus a lot of the tooling I would need, at a price that I couldn’t ignore, and all in the same place. The items had just been posted, and the only catch was that they had to be picked up in person, ASAP.  

12 hour drive there, 30 minutes getting the loot, and 12 hour drive back, 1100 mile round trip. No problem! Honey... how would you like to go for a drive?

Well, that was pretty rough! However, I was too excited to care, until we got back that is. That night I slept like a log.

A complete table top machine shop

These two awesome machines belonged to Craig, a brilliant MIT trained mechanical engineer, who had used them for prototyping automobile parts for Audi. He unfortunately passed away in his 50’s after a 2 year battle with brain cancer, and they sat unused for 2 more years. Both machines were working fine the last time he had used them, but by now they displayed surface rust and other signs of disuse. I knew going into this that I would need to bring them back up to speed, and I was willing to give them all the TLC they needed in order to start making parts for my Long EZ. Craig’s wife Kat, was very gracious under the circumstances, and loved the fact that I would be making airplane parts with them. I’m positive Craig must be smiling as well, wherever he is.

Later that week, I spent a whole day sorting out and cleaning all the things I had acquired, and equally important, cataloging everything I was still missing to make the machines operational again. Buying tools sight unseen is risky, and I really went out on a limb on this one, but I had strong indicators that a good deal was in the making. 

Today, after a complete tear down and rebuild of the lathe, I am still happy about this purchase, even after sinking more money into it to replace missing or worn parts.

I have not yet touched the mill, except to verify that the spindle turns under power. Cleaning it will be a project for a later date, since I have no immediate need for it.

So, why was I looking so hard for a lathe in the first place?

Well, I am reaching a stage in the construction where I will soon have to either purchase or fabricate the landing gear assembly (LMGA). 

This cylindrical part fits between the landing gear mounts, and will attach to the landing gear bow (aka: gear legs). 

LMGA mounted on the inboard side of the rear fuselage

It also features two steel bushings (LMGAB) on either end of it, that will support the BIG landing gear bolts.

So, I needed a lathe to transform raw steel rod stock into bushings, and raw steel tubing into LMGA.

If you are still reading this long boring post, I'm very impressed. So, if you stick around a little longer, I will show you the actual making of LMGAB, the 4130 steel bushing. 

Bear in mind that these are my very first cuts with a lathe, and the first opportunity to put into practice everything I have been learning on my own so far. The bushing I am making in these clips is just a test piece, and will not be used on the actual plane, but it will serve to highlight some of the challenges that I am facing, both with the machine and with my technique, and an opportunity to start honing the skills necessary to approximate CozyGirl perfection. 

Yes I know, that is never going to happen, sigh! At least not until I get a TIG welder, and a laser cutter, and a ...

Why don't we just take a look at the raw materials as they came from Aircraft Spruce?

Solid core 4130 steel rod

Hollow 4130 steel tube

Although they look round and straight, you have no idea how lob-sided these things are until you chuck them up to your lathe and start making some gentle passes on them with a cutter. Wow, these things are so far off even Wal-Mart would think they are junk! I suppose that’s the whole point behind being “raw” stock. Being a machining newbie, I was just a little shocked.

I shoved a foot of tubing right through the chuck until only about an inch was sticking out of the front end (for rigidity purposes), and faced the end of it to make it square with the longitudinal axis, then I cut a starter hole with a super stiff center-drill.

At this point I loosened the chuck’s grip on the rod, and pulled it out about 6 more inches, and secured the chuck once again. I replaced the drill on the opposite hand with a “live center” that has ball bearings inside, and is able to spin with the piece being worked on. I placed a cutter on the tool post, and started reducing the diameter of the rod.

As you might imagine, this reduction of size is done in multiple passes, starting with some roughing passes of maybe 10 to 50 thousands of an inch, depending on the hardness of the material, and ending in 1 to 5 thousands finishing passes to produce a better surface, and sneak up on the required final size.

After using a “parting tool” (not partying) to separate the bearing-to-be from the rest of the stock, I flipped it around in the chuck, and faced it multiple times, reducing its size to the one specified in the plans.

Switching back to a drill chuck, I center-drilled the flat side, then used a drill bit to cut a hole straight through.

As with the turning, producing a big hole is done in stages, utilizing drill bits of increasing size, until the proper dimension is reached.

At the end of this long process, I was rewarded with the long sought after bearing, that while not a looker, it was at least the correct size.

Test bushing behind its plan

Unfortunately, I later underestimated the power of sandpaper, and using it I further reduced the OD (outside diameter) of the part, in an effort to produce a smoother surface. Not by that much, but the required “light press fit” is definitely gone.

Test fitting

Here’s a test fitting of the LMGA-to-be, with the test bearing, and the actual landing gear bolt.

Don't you just love when everything fits together?

After producing a semi-prototype LMGA (it might be good enough to be used), here’s a shot of what I’ve got so far.

I knurled LMGA for a better grip once it's buried in flox

One side of LMGA is right on size, 5/8” or 0.6250” ± 0.0000”!!!

Checking one side of LMGA

The other side is off by 1.6/1000”, -0.0016” (0.041mm) at 0.6234”, not perfect but good enough.

Checking other side of LMGA

All I need now is 4 more bearings, and 1 more LGMA. 

Come to think of it, this kind of work is quite fun as well, and my shop is just the place to spend many hours "Learning and Recreating" oneself.

“Tooling up” - Drill Press

A good drill press is a great addition to any shop, and is an invaluable tool for a variety of situations. 

Unfortunately most inexpensive drill presses (made in China - check your label, you'll be surprised) have junk components that can cause the drill bit to be unable to cut a round hole. Usually this is due to a cheap chuck that is not properly parallel to the quill, and forces the bit to travel in an elliptical fashion. While this is marginally acceptable for wood working, where tolerances are a bit laxer, it is totally unacceptable for precision metal work.

As much as I would like to buy American made products, quality American presses are out of my price range, if I want to be able to equip my shop with more than just one tool. So, Chinese it is (again). Sigh!

I bought my press when it went on sale at Northern Tools, so that I was able to buy more press for the same money.

I should really repaint that floor

The box weighed 160 lbs, nearly half of which are located in the head of the press. Can you spell... top heavy?

All parts were coated in oil to prevent rust from forming during shipping

As always, I find myself alone every time there’s some heavy lifting involved, so I ended up assembling it on my own. This turned out to be quite a struggle, and it would have been far better to lure some unsuspecting neighbor in my shop with the promise of free beer. Between the weight of the components, and the oil that was covering every part of it, the process looked more like a mud bog wrestle event than anything else. Nevertheless I got this thing together without banging it up too badly.

Final resting place

When I finally turned it on for the first time, the top cover rattled like a sidewinder in heat. No matter how much I hit it, this cover was determined to make me lose what's left of my hearing. Rummaging through a box of leftover stuff, I found a piece of fuel line from my deceased 1982 Honda. So I sliced it the long way, then cut it in three pieces, and used them around the perimeter of the top cover as bumpers.

Noise gone!

1982 technology to the rescue

With the rattling taken care of, I decided to drill through some wood to test things out. Unexpectedly, after the first inch of travel into the soft material, the drill bit, the quill, and the spindle froze. Crap! A little head scratching later, I discovered the top spindle nut so loose it came right off.

Non existant quality control

As luck would have it, I just happened to have the huge 32 mm socket that fit the nut, so I tightened it snug. Drilling through wood was now no longer a problem.

Since garage floors have a natural slope, I made some leveling devices out of a bolt and two nuts, one below, and one above the pedestal (times twice).

Home made leveling devices

Although I had high hopes for a relatively decent chuck, I prepared myself mentally to having to replace it. Sure enough, even China's finest chuck was off by a light year, and was sent to the scrap pile where it belonged.

Introducing the “Little Machine Shop” keyless chuck (plus arbor), made in the USA and straight as an arrow... aka another $40 down the drain!

New chuck to the left, old clunker to the right

At this point I had a decent device for drilling holes, but there were still two more issues to be solved before I could take advantage of all this accuracy.

Issue #1 = How to hang on to the piece to be drilled.

I chose to equip the press with a quick action vise (awesome!), for ease of handling numerous parts needing to be drilled. I found it on amazon.com for 25% less.

Issue #2 = How to get the center of the hole-to-be precisely under the drill bit.

I decided to go all out, and add a compound table with which I will be able to position the part exactly under the awaiting drill bit, and do so with a repeatable level of accuracy regardless of how many holes I need to drill in a part. This I bought straight from grizzly.com, since the price was the same everywhere else I looked.

Yes, this vise is huge. Yes, I thought it was going to be smaller. And yes, bigger is better!

If I were a piece of metal waiting to be drilled, I'd be afraid right now

Tight quarters, but serviceable

I cannot wait to start drilling something!

UPDATE: I finally purchased some precision measuring equipment, and was able to accurately measure the runout error of my drill press using both of my chucks (not at the same time, duh). Well, a man has to admit when he's wrong. So, contrary to what my naked eyes led me to believe, it turns out that both chucks have a similar and acceptable level of error, in the order of 3.5/1'000" about 1" away from the chuck. Being that the error is nearly identical between the two of them, I am inclined to believe that the spindle might be the cause of it, but it is minute enough not to matter.


In the two videos below, every line of the instrument equals half of 1/1000 of an inch. What you'll see is about 6 to 7 lines being crossed by the needle during its travel, so we are talking about 3 to 3.5 thousands on an inch deflection from true circular motion.


Viewing Tip: The needle is hard to see in this small window, and the "Full screen" button doesn't appear to work in Safari. To see it more clearly, click on the "YouTube" logo (near the bottom right of the window) to open these videos in YouTube, then select a higher resolution, and click the "Full screen" icon (bottom right).

Original chuck runout test

 Keyless chuck runout test

The old chuck is permanently out of the trash bin, and my foot is tightly wedged in my mouth for the time being.