Therapy Project

[mike mcs repair]

I took a look at Airframes' heavy duty gear fitting. I see it has doubled pieces, and I noticed the internal washer is only edge welded on the outside. I assume that is to prevent the cracking I've heard about.

https://www.airframesalaska.com/Fron.../af21272-4.htm

I thought they also had an even heaver duty one like yours, that goes strait up to tube without that overhang of cabane ear...

[RVBottomly]

the original washers are only partially welded(edge welded, and its at the end of that weld where they crack)

Thanks for that clarification. I read some threads on the dog-bone doubler to deal with that. Do you think a double-thickness fitting would do the same thing?

I suppose while I'm at it, should I make it more triangular and add a safety chain hole, too?

[RVBottomly]

your fitting in drawing is already beefed up style , should be good

heres what the originals look like that crack at the washer: not how its unsupported at washer.
https://www.univair.com/piper/piper-...front-fitting/

5/16 bolt

Thanks Mike.

I guess I should have read all of your posts before asking questions...LOL.

[mike mcs repair]

here is the true heaver duty style, you use these to convert a pa-12 to -18 gear... kinda like yours

https://photos.app.goo.gl/XoLUwwcM1ivq2bWu8

[RVBottomly]

10.5 hours over the past two weeks. That's what it took to layout the gear fittings and finally get them parallel and square.

I tried various jigs and finally ended up lightly tacking, tapping with a hammer, grinding the tack away and shifting, measuring in three dimensions, tacking again.

Despite having wooden and, later, a steel jig holding my all-thread exactly parallel, it would still end up off after tacking.

But it finally happened and I'm fairly happy with the alignment.

If I were to do it again, I'd run the 1/2 bushing tube between both front and back fittings to keep those aligned. Then it would only be two dimensions of jigging. But, alas, I didn't have enough material.







There were diversions, however:



Now I need to order some more tubing for the Vee cabane and gear assemblies. I have plenty of material to keep doing other things, though, so plugging along continues.

I looked at my build log and tallied hours to date: 221 hours over 10 months. I think I need to step it up a little if I want to get to Johnson Creek next year.

[RVBottomly]

I'm waiting for my order of additional materials for the landing gear to arrive--should be here tomorrow. I spent time tweaking and checking the fuselage alignment and finishing off missed weld spots, etc. I was pleased with what I had. I measured from a tight string marking the horizontal reference line to all sorts of locations, and the measurements were very close to what they should be. Eyeballing the line straight from tailpost to the firewall showed it to be at the center of every station.

So I welded the x brace in the tail and, without really noticing it until later, I ended up with lower longerons bowed in.

Picture shows the fuselage upside down:



So now I have more to do at the tail end... and it got me wondering if the x-brace really strengthens things. I'm sure it does, but it seems odd to have it tying into the middle of the braces like that. I'm half tempted to weld up shapes with 1/16 rod and try twisting them with a light torque wrench to see the failure modes.

But I'm also looking ahead and starting to calculate wing materials. So many questions are popping up; and so many rabbit-trails beckon. I end up musing a whole bunch.

I'm still trying to pin down flap forces in various configurations.

Lately I've been flying a rented 180hp C-172 with a constant speed prop. It is quite a performer. I've taken to studying its flaps carefully. It has the manual style that go up to 40 degrees. Pretty effective, it seems to me. I'm wondering if something like that would be nearly as effective as the Keller flaps. But the forces involved, it looks like a lot of twisting leverage?

So that leads me to ponder the little rear spar of the Piper design. I don't have a PA 14 drawing, but the Wag Aero metal wing kit uses the same spar dimensions as the Northland drawings. I wonder why not use one with a wider web and trim the rib capstrips to fit? Or is it necessary? I've been drawing various ideas for compression struts that would double as ribs at the flap hangars.

I don't even want to bring up my idea for a combination AOA indicator and low airspeed indicator that looks suspiciously like a trolling speed log.

Or variable pressure inflatable bushwheels that you could pump up or down from the comfort of the cockpit.

I think I have it bad, but at least these diversions generally occur at night before bed, instead of when I'm working on the project.

[Gordon Misch]

I'm half tempted to weld up shapes with 1/16 rod and try twisting them with a light torque wrench to see the failure modes.

Please do. I've had a hard time trying to quantify that tail bracing. X-bracing and boxing. Mine is boxed, but I can't explain why it's a good idea.

[tempdoug]

it helps for twisting between the tail spring bolt forward to the first set of diagonals.

[Gordon Misch]

I know that's the intent, and I'd sure like to see some tests to see how effective it is.

[RaisedByWolves]

It keeps the longerons from bending , and the diagonals, and keeps the two points where the jackscrew attaches from bending and being put in a bind



After the longerons and diagonals were replaced I put the horizontals on and found the rear attach was off quite a bit, causing the jackscrew to not turn. I can’t find a better picture but the rear attach was off quite a bit.

I can tell you exactly where I bent the tail, landed on a narrow road I mean runway, turned around and the baby bushwheel hit a rock or hole. That’s about the time the trim stopped working.


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[RVBottomly]

Finally got back to the shop. The past two weeks have been a disaster in my other life--I ended up getting assigned cases from another public defender who, for various reasons, has now been found unable to represent clients. My planned-for quiet fall and winter has turned into a perpetual state of triage.

But that is why there is a therapy project. I was pleased to make a little progress on the cabane vee.

I cut from .090 4130 sheet the four shapes to be doubled into two parts.



Edge welded them:



And then drilled the two pieces at once to keep the holes lined up.



I am really enjoying my RF30 clone mill/drill. I have been doing just that, drilling and milling. It seems very steady, even with pretty big cuts. I do take my time, though, and keep the speed fairly slow for 4130 steel.

I even roughed out curves on the brackets freehand. Those of a certain age will remember Etch-A-Sketch. It was great training for free-handing a curve on a mill.



Parts after drilling:



Then came the Vee:





Then the brackets tacked on:





Finally there was trimming, drilling and aligning.



I missed a few photos where I milled the ends of the vee to accept bushings, and then tacked those in. I'm pretty pleased with the fit. Still more welding and drilling, but I see the steps leading to having my landing gear fabricated.

As I said in my wings thread, I'm working on supplies for that phase. But I've got plenty to keep me occupied into early next year, at least. Next sub-project will probably be the control torque tube assembly. I'm planning on a simplified version with one stick between the two seats, much like Paul Claus's new 4 place cub. I'm investigating aluminum versus 4130 weldment, and am open to any warnings or ideas.

Pressing on,
Vic

[skywagon8a]

it helps for twisting between the tail spring bolt forward to the first set of diagonals.

I know that's the intent, and I'd sure like to see some tests to see how effective it is.

Gordon,
Consider the lever arm of the tail wheel spring against the two attach points with a side load. Then look at the column loads on the lower longeron between the tail wire attach point and the next bay forward. The new added X​ brace cuts that column load in half.

[Gordon Misch]

Pete, is that how they fail - column buckling? I thought it was in torsion. I haven't personally observed the problem. My IA had me box those tubes rather than x-brace them. If it's a column failure the boxing would be superior, I think, due to support of each tube in two axes. Thanks - -

[tempdoug]

for what its worth. when i built my plane i called atlee and asked him about x or box brace or none at all, he said box, so i never questioned it and went with that. he mentioned having the top tube a little farther back to clear something, but he made his clamp in one with the top tube down some. just wondering if this x and box thing is a clearance issue more than anything. but he did say to do it.

[skywagon8a]

Gordon, I was only going by Tom's pictures in #175 where there are two tubes with a column buckle. His X brace reinforcement cuts the column length of four tubes by half. By welding the X in the center there is additional stiffening. The damage is caused by torsion on the entire aft end of the fuselage but when you narrow your focus to one tube at a time you can see the column failure.

[RaisedByWolves]

Gordon, I was only going by Tom's pictures in #175 where there are two tubes with a column buckle. His X brace reinforcement cuts the column length of four tubes by half. By welding the X in the center there is additional stiffening. The damage is caused by torsion on the entire aft end of the fuselage but when you narrow your focus to one tube at a time you can see the column failure.

When you have a big tail wheel (baby bushwheel) and swing the tail around, hit something solid, the longeron bends (green line) it’s un supported from the factory. Later model cubs and a’s had the smaller tube in there (red line)

I rebuilt my cub from landing on a road and turning around and not watching the tail wheel and hitting something. I added the red tube and x brace and now I look out the back windows when turning.
Only make that mistake once









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[Steve Pierce]

The diagonal tube Tom shows in red was standard on the A models and late model 150 how Super Cubs I have worked on. Seen way too many Super Cubs with that aft section of longerons bent. That is a long piece of 3/4" x. 035" wall tubing to be unsupported. Straightened several on covered airplanes with a hammer and a 2x4. Sometimes it worked good, sometimes ok.

[RVBottomly]

When you have a big tail wheel (baby bushwheel) and swing the tail around, hit something solid, the longeron bends (green line) it’s un supported from the factory. Later model cubs and a’s had the smaller tube in there (red line)

I rebuilt my cub from landing on a road and turning around and not watching the tail wheel and hitting something. I added the red tube and x brace and now I look out the back windows when turning.
Only make that mistake once









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That red tube makes sense to me. You said it was smaller. What size did you use?

[mike mcs repair]

for what its worth. when i built my plane i called atlee and asked him about x or box brace or none at all, he said box, so i never questioned it and went with that. he mentioned having the top tube a little farther back to clear something, but he made his clamp in one with the top tube down some. just wondering if this x and box thing is a clearance issue more than anything. but he did say to do it.

yes, box is all i use, the tube farther back/lower is to clear the bottom elevator cable

[RaisedByWolves]

The diagonal tube Tom shows in red was standard on the A models and late model 150 how Super Cubs I have worked on. Seen way too many Super Cubs with that aft section of longerons bent. That is a long piece of 3/4" x. 035" wall tubing to be unsupported. Straightened several on covered airplanes with a hammer and a 2x4. Sometimes it worked good, sometimes ok.

Worked for me to straighten, but the jack screw was in a bind, ended up having to replace the rear attachment


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[Steve Pierce]

That red tube makes sense to me. You said it was smaller. What size did you use?

3/8" tube

[Steve Pierce]

Here are those 3/8" tubes on a late model Super Cub.

[Gordon Misch]

Gordon, I was only going by Tom's pictures in #175 where there are two tubes with a column buckle. His X brace reinforcement cuts the column length of four tubes by half. By welding the X in the center there is additional stiffening. The damage is caused by torsion on the entire aft end of the fuselage but when you narrow your focus to one tube at a time you can see the column failure.

I don't think that's a compression buckling failure, I think it's plain ol' bending from torque imposed by the tailwheel.

Nonetheless, I certainly see how the additional bracing makes sense, and I'm glad I did it on mine.

Thanks to all for the pics and thoughts - - -

[Olibuilt]

3/8 tubes

[RVBottomly]

Switching gears, so to speak. I'm starting to fabricate the landing gear. What exactly is extension of 3 inches in the 3" extended gear?

Is the axle attachment 3" farther from the pivot points, or is the 3" measured vertically?

I can't seem to find actual dimensions.

Thanks,
Vic

[RVBottomly]

So I researched what I could find on extending the landing gear--not sure it's something I want to do, but I ran across something that caused my first real concern with the Wag Aero plans.

First, stock gear for a PA 18, latest iteration on the Northland plans, is 1 3/8 x .058 4130 for the front tube and 1 1/4 x .058 4130 for the rear tube on each leg.

The Wag plans have the same diameter of tubes, except they call for .049 thickness. As drawn, they are not even as stout as the L-21 plans. And the 2+2 is supposed to have a GW of 2200 pounds as opposed to the 1750 of the Northland plans. (Add to that a story I can't find anymore of a 2+2 breaking its gear on a gravel strip).

Then I ran across a reference to heavy duty PA 18 gear: 1 1/2 X .058 for the front and 1 3/8 X .058 for the rear.

I already ordered and have the .049 tubes, but now I think that not only should they not be used for extended gear, I'm not inclined to use them at all.

Any thoughts on this?

Thanks,
Vic

[skywagon8a]

My thoughts on extended gear differs from what most here seem to like. I believe that a stout standard size gear is more robust. The extended sized gear will have greater leverage on the fuselage attach fittings making their margin of safety less. The leverage component on the fittings is the distance from the axle to the fittings. If you want to increase the three point angle of attack you install larger diameter tires to standard gear from which you get two advantages. Increased wing angle and better rolling on unimproved ground. If you combine the long gear legs with the large diameter tires your low speed drag component for take off can actually retard performance. If your only purpose is to increase the angle of attack then use the long gear with small tires.

From a flight perspective if you use extended gear with large tires rather than standard gear with large tires your drag component will be higher due to the requirement for more nose up trim to compensate.

Also if your airplane is heavily loaded, acceleration for take off will be slower with the extended gear due to the increased drag from the down elevator requirement while accelerating. Seems to me that a 2+2 has the cabin volume for "heavy" loads. Enough so that standard gear would be preferable under certain conditions. When a plane is lightly loaded these differences may not be very noticeable to most pilots. But, when you are heavily loaded the differences could make the difference of whether the take off is successful or not.

[stewartb]

Switching gears, so to speak. I'm starting to fabricate the landing gear. What exactly is extension of 3 inches in the 3" extended gear?

Is the axle attachment 3" farther from the pivot points, or is the 3" measured vertically?

I can't seem to find actual dimensions.

Thanks,
Vic

I believe the 3” longer is in the tubes so the installed gear adds approx 1-1/2” in height and width. The taller gear was a necessity for legal prop clearance with Borer props on straight skis. Then we all wanted to maximize AOA, and 3” extended became the norm. Now some guys with 35s use standard length gear and on the flip side, Mackey built airplanes use something like 10” extended gear. One size does not fit all. The available new gas shocks negate most of the stress on gear. The difference is amazing.

[Yentnacruiser]

As we all know anything you change will be a trade-off of some sort. The thicker wall thickness will make it heavier, depends where you plan on taking them. Heavy-duty is a must on skis. Can be the most punishment your airplane will take, you'll hear all kinds of interesting noises. The extended gear also gives you a wider stance. They make it harder to grab the struts at the wing attachments and raise your ski. For my 5'7" frame 3" extended gear and Bushwheels is about maximum height for putting on wing covers. In addition the higher you go your three-point CG changes making the tail heavier.

[RVBottomly]

Thanks everyone for the insights. I ordered .058 tubes with a step up in diameter. Now I have the chance to compare weights.

One thing I'm considering is my fuselage has the gear attach points 4" wider than on a super cub, so it has a wider stance already.

So, I'm not sure if I will go with extended gear. It is unlikely I'll do much ski work here, given that we have snow on the ground, at most, about a week each winter. Lot's of snow 30 miles east of me, though.

But I'm pretty sure I want the stouter tubes.

[CharlieN]

The stouter tubes can be a good thing. One thing to consider is how many tubes fail. In heavy compression the tube is prone to bend or buckle mid tube. The heavier wall helps a bunch in these loads.
In a hard landing where the is extreme tension or side loads in a tube, a cuff, or doubler at the ends of the tube even with a lighter wall thickness offers a substantial increase in strength. This doubler can be a length of say the next size larger tube with say a 0.065 wall welded over the ends. This can even be a section of 0.049 tube slit along it's length so it can be wrapped snug over the parent tube.
I use allot of doublers in what I build.

[RVBottomly]

I left off working on the cabane vee. Here is the finger strap and bushing for it.



Then it was time to lay out and bend up the u-fittings that weld to the gear legs.






The tubes in previous picture are 9/16 x .065. 7/16 x .028 bushings are supposed to fit inside. I had 7/16 x .049 for some reason, so I drilled them out.



And tacked things together


I ordered my larger tubes from Wicks last Friday, taking advantage of a 15% ebay sale. They came the following Monday, 12/24, which surprised me. I started cutting things up and tried a tack.



Then came a Christmas diversion. I had promised my wife a coat rack. There was a dead poplar I had cut down last summer. OK, time to get to those overdue promises.



My little lathe did some wood duty for the pegs



By noon I had a rustic rack. I later varnished it up and now it does its work de-cluttering our entry way.



Then it was back to the landing gear. Main tubes are tacked and aligned. I still need to fabricate some finger straps, and then a jig to put it all together with axles, etc.



So I've gotten a fair dose of therapy these past few days. A good thing, I think. I have to store some of this playtime against the crush of work that is lurking over the next 4 weeks.

[RVBottomly]

I suddenly found myself with a spare 4 hours, so I jumped in to see what I could do on fitting the gear legs.


First I leveled up a temporary cross brace to establish the angle of the legs at the point where the axles are level.





Then followed some free-hand profiling and trial and error fitting with the help of some 1X4 homemade clamps.





Eyeballing the rear angles.





Then tacked it together and did the same on the other side.



Now comes the slow part, making finger straps and welding everything up, adding bushings, and reaming.

And of course, layout of the axle. I ran out of time as I was marking out some finger straps.



So I remain happily engaged at the pace of plod.

[RVBottomly]

Happy New Year! Nice to have a quiet day in the shop. I spent some time on axles.

For some reason, I couldn't find a 1 5/8 hole saw in my collection. So I tried the lathe to make the axle hole for the brake plate. Glad I had a 4-jaw chuck.



I needed a thin tool to start the hole. My regular tools caused too much chatter and would catch the work. I didn't really want to grind down 5/16 tool stock. A worn out Phillips impact driver bit ground to size seemed to work just fine.



Then it was just a matter of machining the hole outward with a side cutting tool until I reached the 1 5/8 diameter.





They fit....



I'm expecting a set of Grove brakes to arrive tomorrow. I'll wait on drilling mounting holes until I can line things up.
Meanwhile, there was work on finger straps to be done.






Then the supper bell called.

[Beaverpilot]

Nice looking project!! I am getting ready to build my axels as well. Any pictures you can put up on how you cut and flatten the cabane slot in the axel would be a great help to me. Thanks!


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[RVBottomly]

Nice looking project!! I am getting ready to build my axels as well. Any pictures you can put up on how you cut and flatten the cabane slot in the axel would be a great help to me. Thanks!


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Providentially, I got more done with more pictures.

I should have waited to get my brakes before making the torque plates last week. Even though I looked at the specs, I didn't make the connection that the torque plate on the Grove brakes I purchased were based on a 2 1/2 diameter instead of the smaller square of the cub design. So I'm glad I waited to tack the plates on until the brakes came.

New plates marked out.



Then I marked out the slots for cutting.



I used a hand-held cut-off wheel to start the slots. I made notches at the end of longitudinal cuts and then used pliers to bend up and down the tabs to break them off.



Then I was going to grind to the lines, but I remembered I had a mill. Ding-Ding-Ding. It was easy using that.



An aside--before I cut the notches, I tacked the axle tube to the doubler so it wouldn't shift.

After milling the notches it was time to tack the torque plates. Didn't take a picture, but I found I could use a square piece of 1 1/2 angle iron as a guide to make the plate square to the tube in a vise.



Then the plans called for edge welding on the end.



Then welded up the torque plates on the inside only and drilled 3/8 holes.





The Wag Aero plans say nothing about flattening the end with the holes. The Northland drawings specify that it be flattened. I'm confident that heating up the end with a torch and squeezing with a vise would do a good job flattening it. But I am still contemplating a beefed-up filler there, as I saw on the carbon cub, so I'm waiting on that task.

Next step was to come up with a way to align the axles. I cut a 6 foot length of angle iron and used hose clamps to clamp the axles to the angle iron. It seems pretty solid and aligned up pretty well. I'll need to make a scaffold of some sort to hold it all in place for welding the axles in. That will be for another day.

[Beaverpilot]

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this is what I have on the sport trainer drawings. About heating and flattening the tabs

[RVBottomly]

this is what I have on the sport trainer drawings. About heating and flattening the tabs

Well, that's interesting. The 2+2 plans have a note for edge welding, but no detail on flattening the ends. What size axle are you using?

[Beaverpilot]

I’ve been debating— I have some 1.25 axels that came with my project and I have plenty of 1.5 stock that I could make some. I’m leaning towards the 1.25 as I plan on having it on skis part of the year and have read that it is difficult to find skis for 1.5 axels


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[RVBottomly]

I think the 1.25 works best for a sport trainer. Plenty of options for brakes, and skies, etc. I went with 1.5 because that was on the plans and it's a heavier airplane at gross weight.