Need some advice on fabricating Cub gear.

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Tench745

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Hello all, I've been plugging away at my Jr Ace project making progress. One of the tasks at hand is fabricating the Cub style gear legs. I'm using drawings from supercubproject.com
So far I have the tubing for the gear vee rough-cut and I have the "bearing assembly" brackets which the gear will pivot on.
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The base of the bracket is smaller than the tube it attaches to (1"x 1-1/8" bracket to 1-1/4" tube). What I'm trying to establish is how the top of the tube is supposed to be reshaped to meet the bracket so the reinforcement strap fits nicely. Currently I'm focusing on the forward tube of the gear vee. The aft, angled, tube is a later puzzle that should be pretty straightforward once I figure out the forward fitting.

So, what I'd like to know is, how did Piper bend, cut, weld, or heat the forward tube of the gear vee to fit the bearing bracket?

I'm going to go stare at a J-3 yet again later tonight, but it's hard to see much when the gear is installed and the fitting is obscured by paint and fabric. Any insight would be appreciated.

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Pops

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I heat and use a hammer to flatten the sides of the tube a little less than needed to make room for the weld to the bearing tube. Grind or file the fish mouth for the bearing tube. Tack the bearing tube in place and then weld. Make the reinforcement strap and tack one end and heat and wrap around and weld. I install an old bolt into the bearing tube as a heat sink while welding and remove and ream to the correct size.
 
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Dana

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I don't know exactly how Piper did it, bit this is the new gear I made for my Starduster. The front tube (to the right in the picture) is round, and I flattened (in a vise with heat) it to match the width of the C-shaped bracket that caps it off, with additional straps fore and aft hammered to match as they were welded. The rear is streamline tube, with an L-shaped bracket in the front and a flat bracket in the back supporting the bushing, then a strap formed over it and welded.

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Pops

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Make a simple jig like Dana did makes it a lot easier and holds everything in the correct position.

Picture of the LG jig that I built for making several Bearhawk LG's.
 

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TFF

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My guess is Piper worker tacked one end and used heat and a hammer. You are not driving rail stakes. In fact, once it’s hot enough, it’s just baby taps. They may have had a press putting a pre shape, but I doubt it. The beauty of 4130 is it can be shaped at anyones budget level, and pretty much most skill levels.
 

Tench745

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I have a jig for the gear laid out on my build table; that was simple enough. Near-side is for the forward tube to axle sleeve connection. Far-side jig is for the forward tube/rear tube v. (jig not yet completed in this picture). That wasn't the question.

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I don't need to know how to add bushing stock to the end of a tube either. I've done that six times now in making the spring-struts and cabane vee. And I've heated and flattened the ends of tubing a number of times in making my tail surfaces. That's all old-hat now.

The question is how do I shape the forward gear tube to meet the bracket as called out in the Piper drawings? Does anyone know, or do I have to make it up?

I think the process I'm looking for is probably closer to what Dana did to fit his bracket to the tube; where I basically heat and hammer the end of the tube until it's square.

I have seen the Wag Aero drawings where they forego the bracket altogether and weld the bushing stock directly to the tubing as Pops suggests. At this point my tubing has been rough cut and is not long enough to change to that method.

I have also seen a bearhawk build where they welded the bushing in then ground away any of the tube that won't let the reinforcing strap run fair, and then welded the strap in place to close up the hole in the tubing. This seems like the it would be incredibly weak.
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TFF

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If you are talking about where it narrows, they pie cut it and weld it. Where they do it specifically not sure. Usually you fit the bushing, tack it, and then make the cuts to lay the sides to the bushing. Weld it up. Then lay the reinforcement over that.
 

Pops

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If you are talking about where it narrows, they pie cut it and weld it. Where they do it specifically not sure. Usually you fit the bushing, tack it, and then make the cuts to lay the sides to the bushing. Weld it up. Then lay the reinforcement over that.
That is it. If you can't heat and hammer enough to shink it , you can just cut pie shapped piece out and weld it.

On the Bearhawk LG you cut the bushing tube to length and then weld a tongue to it about 1/16" wider that the tube. Form the end of the tube and cut a slot down each side of the tube for the tongue to slide in and weld. Then add the strap and weld. Very strong.

You can see the tongue that is welded to the bushing on the locating rod on the upper left of the picture of the jig.
Added the .100" brace to the axle, not on the plans.

If you follow the Bearhawk plans and form the end of the tube by the plans and install and weld the tongue and strap by the plans there is no hole to cover with the strap and its very strong.

BTW-- My building buddy, Dallas, built the Baby Ace and Jr Ace Landing gear , fuel tanks, and engine mounts for the factory for many years.
 

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challenger_II

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I would highly recommend using plain steel rod rather than a bolt for fabricating the joint. The zinc plating on a hardware bolt, and the cad plating on an AN bolt, will contaminate the weld.
 

Tench745

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Made a couple test pieces out of my last pieces of 1-1/4" scrap tube. Started with a couple different v-notches but they have a lot of curve to make the strap transition to from the square corner of the bracket.
IMG_2453.JPG IMG_2455.JPG

I tried just heating and hammering the end to match the fitting's base, and that actually turned out okay. I'll probably heat further down the tube on the real part to make the transition a little more gradual. Does anyone see a problem with this procedure or ways to optimize it?
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Pops

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My buddy Dallas built a Jr Ace but its been so long ago I don't remember how the ends of the LG was done. But, to me that is a poor way to design the end.
 

Tench745

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Will you be installing a finger plate to tie the assembly together?
Yes. As I said in the first post, I am building this gear leg from Piper drawings.
My buddy Dallas built a Jr Ace but its been so long ago I don't remember how the ends of the LG was done. But, to me that is a poor way to design the end.
The Baby and Jr Ace plans don’t include the gear legs. You are expected to use Cub gear. Rather than buying it, I elected to build my own from original Piper drawings. This is the bracketry they have drawn. What is deficient about it in your opinion?
 

TFF

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I will have to concede. All the Poberezny planes Pixe, EAA, Acrosport use it too. All I can say is what my old foreman at the airline use to tell us, “Beat it to fit, paint it t to match.”
 

Tench745

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I will have to concede. All the Poberezny planes Pixe, EAA, Acrosport use it too. All I can say is what my old foreman at the airline use to tell us, “Beat it to fit, paint it t to match.”
Yep, almost the same mantra in the theatre. Beat it to fit, paint it black.
 

Tench745

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Well, here's what I wound up with. First two photos are the forward tube pre-welding. That turned out well enough that I tackled the rear tube.
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Heat and squash the sides to match the bracket, tack it together. V-notch the long end, heat and beat flat. It'll all get welded together with a wrapped gusset. Should look just like cub gear when it's done.
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