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Therapy Project

Steel bushings might be OK in the Mojave desert for a month or two, but for us in the rest of the world it is surely not a good choice. I use Delrin as a bushing material, bronze is OK but is rather old school by today's standards.

Thanks. I had a blind-spot dumb-out and had transposed reference numbers. Last night I looked again and the Northland plans clearly specify "oil impregnated." Then I started stumbling upon Oilite bushings for sale from Javron and Univair. Inexpensive, too. Finally I ran across Steve Pierce's bushing replacement tool and started to think: "never mind my question...nothing to see, move along...."

But now we talk Delrin? I think I'm really out of the loop. I have used Delrin for harpsichord plectra, and I've seen it on cabinet hinges, but elevator bushings? Sounds interesting.
 
I started using Delrin as a primary bushing material about 30 years ago. In applications that had a bronze or brass type bush I swapped in Delrin. I have yet to replace a Delrin bush That I have made or was installed by anyone else. The real nice aspect is these are an install and forget, you do not need to lubricate them periodically. In my current build the tube or housing any bush goes in will be stainless but steel is fine if protected by paint or some coating. If not coated then a lubricant should be used if anything just to be a protectant from moisture.
 
Thanks, CharlieN. I'll check that out.

Just to vindicate myself a little, I looked again at the Wag drawing and it has the bushing as "3/8 X .065 - 4130". That's what started me wondering about all this.
 
Thanks, CharlieN. I'll check that out.

Just to vindicate myself a little, I looked again at the Wag drawing and it has the bushing as "3/8 X .065 - 4130". That's what started me wondering about all this.

Not all the pivot parts would always be lined, kind of call it fixed bush and pivoting bush. I have built parts from Wag drawings and have some here but it has been too long that I do not recall their technique. I do recall a few cut corners in some aspects of their builds.
But at least one half of the hinge should be lined with a bearing surface.
 
I have the Wagabond drawings too. Exactly the same: 3/8 X .065 4130 for both the "fixed" bushing and the pivoting one.

Then again, I've seen a lot of steel gate hinges last a long time with an occasional squirt of oil. Still, it seemed odd for a control surface hinge.
 
Not really that odd for the plans to call out unbushed hinges. Myself I would go with 3/8-.058 so they do not need to be reamed and there is room for lubricant.
But then I would never build an unbushed hinge now that I know better.
They would have designed for ease of build, not every welder can attach a short .035 wall tube without collapsing it during the process. The .065 being thicker than the tube you are welding to will hold up better during the welding.

If you consider going with thin wall tube and bushings, use a copper rod inside the tube during the weld process to reduce the chance of collapsing the hinge.
If you are doing the hinge as two fixed and one live tube in the center, the fixed tubes can be thick wall and the center thin with a bushing.
 
Just to be clear, the Wag plans have the 3/8 bushing pressed inside a 1/2" x .065 tube.

hinge-detail.jpg



I like your idea about an insert. I was imagining the varieties of distortion I could come up with.

Vic
 
Now I remember that, I was questioning in my mind that the gap between surfaces was greater than the 3/8 plus some standoff for bushing clearance.

Gas welding is not hard to attach .065, Tig can hit harder should the flame, "arc" not be directed properly. But a copper insert will be a great help in lining up the outer bushes. The steel tube will shrink a bit as well as having some scaling on the inside such that a copper mandrel should not be tight before the weld.

I will be using Strap hinges on my plane, these are common on Pitts and other performance planes. They close up the gap in the surfaces, you might consider looking into them. The strap hinges are a bit different to build but in some ways easier and they fly a bit better.
 
Don't forget the gussets 11994-18 in your horizontal stabs. Cub Crafters left these out of the Carbon Cubs and then the braces started breaking and rubbing through the fabric. Their SB00018 RevA addresses this. http://legacy.cubcrafters.com/technical_publications/26/view

Thanks for that! I didn't see anything along those lines in my sets of drawings. The 12769 drawing you attached has more information and detail than what mine has.

The back-watching is much appreciated.
 
BTW, I can't find 11994-18 in any of my Northland or other Piper files. I'm assuming it is sheet metal shaped as shown. Do you know if it's 4130 or whether something like 22 gauge mild steel would be sufficient?
 
The shape is pretty obvious but here is drawing 11994 as well. Oh shot, just realized -18 is not included
 

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The shape is pretty obvious but here is drawing 11994 as well. Oh shot, just realized -18 is not included

Yup, that's what I have.

Well, I think I'll use something that doesn't overpower the channel material that it is being welded to.
 
I've got another question, have you considered going with an airfoil shape on the tail feathers?
 
I've got another question, have you considered going with an airfoil shape on the tail feathers?

I have considered it, and researched it a bit. In the end, I decided to go with stock. It's my first build, after all, and I've got plenty of challenges without also trying to redesign things too much.

Not that I'd be averse to trying them in the future. I'm sort of an inveterate tinkerer.
 
Enjoying some spare time, I formed and laid out the second horizontal stabilizer. It went quicker the second time.

stab-2-layout.jpg


After tacking it up, I put things on the floor with the elevators to see how it all lined up. Not bad, but it required a bit of adjusting.

stab-alignment.jpg


A bit of grinding away tacks, rejigging, using various means of tension and pressure, and it got pretty close. I also started to add those gussets Steve Pierce mentioned.

20180106_162653.jpg


I don't think I'll do anything with the hinges until I have a fuselage to attach it to. I have a bit more material to work on the vertical stabilizer.

Then I'm girding up my loins in preparation for the big fuselage material order. Winter is a great time to do this sort of stuff, but I can see winter flying by.
 
Another block of time, another step along the way. Today I built the fin.

I didn't take any pictures of the process, but it is fairly straightforward--no bends, just straight lines.

20180113_174313.jpg


I decided to take a stab at making hinges. The outer bushings are spec'd at 1/2 OD by .065. I was looking around for something I had on hand that might be used to align the bushings (a bit smaller than 3/8"). Turns out the threaded portion of a 3/8 carriage bolt is a nice snug fit.

The inefficient way to start the hinges is to cut each bushing to size and the tack on a little platform from .062 steel plate.

20180113_143810.jpg


For future hinges, I'm going to steal stknrddr's idea: weld a strip of the .062 along the 1/2" bushing stock, and then cut the pieces.

Next, I braced things together and made sure the vertical tubes were evenly spaced, leveled up the hinge assembly with bits of metal and wire. And tacked in place. It took a lot of heat with that carriage bolt in there, so it took a while to cool.

20180113_153858.jpg


So, one hinge done. The lower hinge is on the fuselage, so it will wait.

hinged.jpg


I'm still having fun, and I'm still busy with dayjob work, but I'm pleased with progress so far.

I need to finish weld the whole tail group. I'm still getting by with my clunky Victor setup. I've looked over other torches in person and I probably will be ordering a Smith AW1A next week, along with a whole bunch of tubes and other stuff.
 
RV

Looks good! If you are gonna stay with the gas method you're gonna love the AW1, might save the Victor for the "big" welds. I also use threaded rod for tacking up these bushings as it doesn't absorb heat so much. But you might use a longer length instead of a shorter bolt as to include both hinge points at same time......... helps keep bushings aligned. You may already have this covered but you will need to make an 36+" or so extension for a 3/8 reamer to clean up and align each hinge point............ Ream one and then continue thru that one into the other. If you have a lathe handy it makes this easy.

Nice work. I really appreciate seeing anyone else that will build form scratch!
 
Thanks SA. Threaded rod is on my list, but I'm not doing any more hinges until I have a fuselage to line up to.

I think I'll have to order reamers, too. Nothing can be found locally as far as I can tell. I just haven't found a good source, yet.

I don't have a lathe right now, but I see myself getting one--I keep looking around. A few years back I was going to build one from the Lindsay books, but realized I'd have a better one if I could find an old one used, even with worn out ways.

Each step according to its time....

Vic
 
I have a Grizzly lathe and mill...not fancy but if you take your time it will do everything you need to a 0.001".

Nice progress!!
 
Lowrider, do you have a combo mill/lathe, or two separate machines? I've been reluctant to look at those 2 in 1 machines, probably because my childhood best friend is a machinist who told me to steer clear.

But I'm not ever going to be a production shop.
 
Combo.
There are advantages to both...I can turn a rifle barrel in the lathe and cut a front sight dovetail without taking it off the machine. I would say you probably get a better quality machine if you buy separate but then they are also more expensive and take up more space. I'm set up on a 5' x 8' bench with all the tools necessary and the area is "over lighted" but it's nice to have more light than you need. Grizzly is not a production machine but it will do many things well enough. With an unlimited budget I would go with higher quality and separate machines.
 
Lowrider, do you have a combo mill/lathe, or two separate machines? I've been reluctant to look at those 2 in 1 machines, probably because my childhood best friend is a machinist who told me to steer clear.

way too much hype from real machinists... anything will get you good enough for what we need... it's not like we build rockets... just fake birds...
 
Thanks Lowrider. Good to know

way too much hype from real machinists... anything will get you good enough for what we need... it's not like we build rockets... just fake birds...

Right! I was eyeing an old set of Audi cylinder heads I have laying on a shelf thinking I could cobble together something....Maybe use the camshaft and put some kind of face plate on it, but that would be just another rabbit hole. I should probably just sell them on Ebay and use the proceeds. The poor car was totaled by a man who "didn't see the stop sign."
 
Mine is very similar to Sky's machine and capable of most things that I want to do. I also have a table top Unimat lathe and mill that works very much like the bigger machine but the bed is only about 12" long will make small items very accurately as long as you don't get in a hurry.

I am NO machinist!! Totally self taught and I would never provide advice contrary to a REAL machinist but I have been successful making things I need and it seems I learn something new each time I use the thing.
 
I did learn the hard way that when machining steel you do need a cooling lubricant flowing over the bit. They don't cut very well after turning red hot. :oops: I made a lubricant squirter out of a 5 gallon plastic pail, an old hydraulic pump from a Lake LA-4, plastic tubing from ACE aircraft supply store and a gallon of 5606 (hydraulic fluid). Of course you can buy one of these but these parts were in my inventory collection.
 
Tools,
I have two real Bridgeport mills and a 14" Warner Swasey lathe as well as an 18" disc sander and about 5 tons of other machines and metal forming tools.
I also have 3 Tig welders and two Mig welders as well, but I do not consider myself either a machinist nor a welder. I am a parts maker, I make allot of parts for all sorts of things.
To me tools make the job easier and generally faster. It is the person making the parts that makes them accurate.
A person with ingenuity can make most anything. A Machinist generally needs a blueprint to make a part.

Anyone want to bring up engineers? Many of these guys have a history to design stuff that is impractical to build. To me again it is those with ingenuity who get usable parts made.
 
Same lesson learned with a low tech solution. I cut really slow and shallow and squirt ATF with some STP mixed in by hand and catch most of it with a specially modified Cool Whip container...it can get messy. I have had really good luck with carbide bits on steel. I still use steel bits on soft metals since they can be shaped easily with a fine grinder wheel and dressed up with a green wheel.
 
Tools,
I have two real Bridgeport mills and a 14" Warner Swasey lathe as well as an 18" disc sander and about 5 tons of other machines and metal forming tools.
I also have 3 Tig welders and two Mig welders as well, but I do not consider myself either a machinist nor a welder. I am a parts maker, I make allot of parts for all sorts of things.
To me tools make the job easier and generally faster. It is the person making the parts that makes them accurate.
A person with ingenuity can make most anything. A Machinist generally needs a blueprint to make a part.

Anyone want to bring up engineers? Many of these guys have a history to design stuff that is impractical to build. To me again it is those with ingenuity who get usable parts made.

Great collection Charlie!! I'd love to have a big mill but I treated myself to on big upgrade in my new shop...a 2 post car lift...need it to work on my '58 Jeep FC 150...and other toys...maybe even airplanes.

I gotta agree with your engineer comment...and to think I had 40 hours of engineering courses before I came to my senses. I also came close to going to law school TWICE but found an MBA more useful.
 
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