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Therapy Project

Thanks everyone for the encouragement. I'm starting to regroup and engaged in a few sub-projects.

The Wag design for the pedal assembly calls for a torque tube within a torque tube. Because it is side-by-side, you have to make both right and both left pedals work as a unit.

My Commonwealth Skyranger simply has two sets of rudder torque tubes next to each other. It works fine and I still might go that route in this project.

But, I decided to try to do it as designed (mainly because I saw pictures of jimboflying's pedals and they looked nice.)

Layout:

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I didn't take a picture, but after this I nested the tubes in some 1/4" angle iron and clamped them in two axes to keep them straight. I also kept the thick-walled 3/4 tube inside the 7/8 tubes to maintain alignment.

Initial welding:

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The inner tube has been removed, but there was a story behind that. I knew that things would be tight after welding and the resulting distortion, etc. But this was TIGHT.

I put the triangle in a large vice, found an 11/16 round stock bar and ended up using 5 pound hammer to drive it out. The inner tube is supposed to rotate. Not yet, obviously.

So the next idea was to ream it out somehow. I ended up making a barnyard reamer out of thick-walled 3/4 4130. I cut some notches in the end, heated the tip up to cherry red, and quenched it in water.

I know, pretty sketchy.

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I loaded the tube with cutting oil, and put the "tool" into the assembly until I hit a blockage, tapped the end with a hammer to go another 3/16" or so, and turned the vice grips. When it loosened up, another tap. Continue.

After about 10 minutes the entire assembly allowed rotation. It's still stiff--I might try some lapping compound or maybe rig up a red-neck cylinder hone, but even just turning the tube with lubrication shows improvement over time.

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In the heat of the moment, I didn't get more pictures or take videos, but I was pleased with how it turned out.

I'm also working on the stick torque-tube assembly. The problem I'm having though is committing to an approach. After laying out the pedals, I'm starting to think this project ought to be a wide-bodied tandem. I'll have to sleep on it a few nights.
 

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Give some thought to material removal - and - how much is left in that outer tube. Another possibility would be to drive a hardened bullet through that outer tube, with heat on the outer tube if necessary.
 
Give some thought to material removal - and - how much is left in that outer tube. Another possibility would be to drive a hardened bullet through that outer tube, with heat on the outer tube if necessary.

Right now, the only stuff removed was slag from the weld penetration. The outer tube is 7/8 with .058 wall thickness. I like the bullet idea, but I think I'm so close now that it's just a matter of polishing a little.
 
Be certain there is copious lubrication between the tubes on final assembly. They will not be moving in relation to each other a great deal so could over time build rust, restricting smooth motion. Place a grease zerk in the middle or apply a liberal coating of anti-seize or waterproof grease between the tubes. This has been an issue on the stabilizer connecting/pivot tube at the tail post. Small motion = increased susceptibility to rust build up.
 
I like to use bushings, When I make that type of structure I utilize tubes with enough difference in diameter that I can install Delrin or HDPE bushings for the inner tube to ride in.
 
Be certain there is copious lubrication between the tubes on final assembly. They will not be moving in relation to each other a great deal so could over time build rust, restricting smooth motion. Place a grease zerk in the middle or apply a liberal coating of anti-seize or waterproof grease between the tubes. This has been an issue on the stabilizer connecting/pivot tube at the tail post. Small motion = increased susceptibility to rust build up.

I agree, Sky. All my years building and working on farm implements makes me want a grease zerk whenever there is steel to steel movement. But looking more into it, I noticed that the Aztec rudder pedal assembly below (found on ebay) is almost identical to what is drawn on my plans. Do these call for lubricant every annual or so?

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I like to use bushings, When I make that type of structure I utilize tubes with enough difference in diameter that I can install Delrin or HDPE bushings for the inner tube to ride in.

I knew you'd say that! I really want to use bushings like that here and on the stick torque tube assembly. So far I've kind of been overwhelmed in locating supplies and also design. Would you use a simple bushing that is free to rotate within both tubes, or fixed to one part, so to speak?
 
Bushings would be pressed into the outer tube.

Along the lines of what Sky was saying, you don't want too close a fit between inner and outer tubes. If too close it wouldn't take much to get them sticking to each other.

No need for great precision. I'll suggest you check out these references re fits. Metal to metal, maybe RC 7 or 8? With bushings, maybe RC 5 or 6?

https://www.engineersedge.com/mechanical,045tolerances/preffered-mechanical-tolerances.htm
https://www.engineersedge.com/calculators/mechanical-tolerances/ansi-fit-tolerances.htm
 
I knew you'd say that! I really want to use bushings like that here and on the stick torque tube assembly. So far I've kind of been overwhelmed in locating supplies and also design. Would you use a simple bushing that is free to rotate within both tubes, or fixed to one part, so to speak?

One source to look at is Mcmaster All sorts of wall thicknesses, diameters and material. I like to plan on a 1/16 minimum wall bush so call it about 1/8 between the inner OD and outer ID. You can run thinner. Being these applications the bush is a rather low load, generally snug on the OD. With a steel tube I would prefer the inner tube to be a bit loose simply to allow oil to remain as an anti-corrosive. I am prone to use stainless steel where the loads allow. This allows a more snug fit since the need for corrosion protection is reduced.

Material choice, Bronze is readily available but with today's engineering plastics the plastic holds up better.

If you need to add clearance to make something free running, use an appropriate outer tube clamped in the lathe allowing you to cut the ID. Other option is a reamer should you have one or justify the cost.

Do NOT try to drill these, it might work but probably will not.

Plastic bushings for high loads should be snug, low loads can be loose.
 
Do NOT try to drill these, it might work but probably will not.

Plastic bushings for high loads should be snug, low loads can be loose.

Thanks Charlie. How about drilling out pillow blocks from blocks of delrin? Is it a heat issue?

I see blocks available on ebay.

I weighed things and it turns out the assembly above weighs 5 ounces more than if I simply use two parallel and offset torque tubes for the pedals. That works on Cessnas, my Skyranger, and I think on several RV designs. Simpler with less hazard of rust on moving parts. I think I'll use delrin pillow blocks to hold them in place. Just not sure if I want to machine them or find something premade.
 
Parallel tubes in Delrin is a superb way to do it. The Delrin can be drilled although an end mill or reamer will provide a nicer final cut.
You might consider split blocks for the Delrin. This offers a way to adjust the bore a bit should that matter. You can however aim for a near zero bore clearance but consideration needs to be considered for long term corrosion control.

Here is another option, turn an insert for the ends of the tubes that will fit inside a ball bearing. The center of the tubes can be supported in a HDPE or Delrin split block.

The end bearing supports can be plastic or aluminum. Image for reference, these support my pedal mixer since I am utilizing full adjustable pedals on each side.

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I am having a hard time finding some images, problem with not being in this file for awhile due to another project consuming my attention recently.
 

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Parallel tubes in Delrin is a superb way to do it. The Delrin can be drilled although an end mill or reamer will provide a nicer final cut.
You might consider split blocks for the Delrin. This offers a way to adjust the bore a bit should that matter. You can however aim for a near zero bore clearance but consideration needs to be considered for long term corrosion control.

Thanks. I was planning on split blocks and I have a nice set of end mills. I like the option of adjusting the bore with shims if necessary.
 
Been a while and I'm lazy when it comes to updates. But things have progressed.

I went the parallel rudder tube approach with Delrin pillow blocks. I ordered a block of Delrin online to see what I could do.

For the pedal assembly I cut little blocks from what I ordered, cut them in half and bolted them together. Then I put 3/4" holes right where they split. The first few I did with a 3/4" end mill. Then I ended up swapping out mill collet for the drill chuck to drill something. Then I wondered, "maybe a spade bit would work."

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Yup. At 120 rpm it worked fine. Delrin is pretty neat stuff.

I had a bunch of shavings, of course.

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I wondered about flammability with it laying around. Grinding sparks and all.

So, a diversion.... lightweight delrin firestarter:


At least it works on wet tumbleweeds.

FWIW, I swept up and vacuumed all the delrin shavings to keep me from starting fires in the shop.

Then I went to the pillow blocks for the 1.5" torque tube, using my cheapo expanded mini-lathe. (16" bed instead of 10")

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I'm pretty sure I need steel reinforcing of some kind. Maybe a top plate with the edges bent down? The torque tube pillow blocks specified are aluminum.

I didn't show the rudder bar assembly being welded up, or the torque tube fabrication. It was tedious but not bad. Here is a draft layout in the fuselage:

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Then it was back to welding on the torque tube. I was contemplating all sorts of alternatives, but ended up with going as drawn. I can spend three times as much time second-guessing myself as it would take to build something. For this I decided to go with what has been done before.

Torque tube welding:

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Gussets were added but I don't see pictures

Control arm bushing holes drilled (step drills seem to drill round)

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Then tabs put on control stick stubs

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Put it together held with welding rod to see how it fits:

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The sticks go back and forth with no interference on the connection rod. So far so good. Still have to weld the elevator arm.
 

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Float fittings etc.

So another month goes by. The new normal is not really normalized, but things plod along.

I finished up the control stick torque tube assembly. Long ago I was thinking of simplifying it to one center stick. I got talked out of it and went with the drawing.

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Suffice it to say it is a heavy assembly. Combined with the stick attachments, it is around 3 pounds.

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I also welded on tabs everywhere for the floor and other attachment points. No pictures, not really difficult work, but tedious bending and twisting of my stiff body.

Then I decided to fabricate float fittings from the Northland plans. They are stout. .090 material for the flat square, .10 for the lugs, and .125 for the tabs.

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The fittings are heavy. 13.5-14 ounces each--not counting the milled insert that I don't have material for right now.

But they look like the Atlee Dodge or Univair ones, and cost me some $20 in materials. I didn't count the gas I needed to get decent penetration, though. It was hot welding them. For some reason I don't have a picture of the final result, but they look like they will make very strong gussets if nothing else.

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The angle of the tab concerned me a little, because the fuselage is wider than a super cub fuselage at this point. I sort of adjusted for that based on what I could find on line. In the end I decided that, if necessary, I could adjust them with heat.

This was an interesting diversion. I can see why the big-name suppliers charge $500-700 for weld on fittings.
 

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Looking for ideas: door frames

So I shifted gears and started bending sheet metal for the door frames. I finally figured out how to do the backward bends with the things I have, but then the gnawing started....

The plans say to weld these channels every so many inches. Right.... Weld onto bare 4130 tubing things that will collect water and dust.

I looked at various threads on rust developing from window and door channels. Predictable results, apparently.

I'd like to be able to put a good coat of paint on these tubes before covering them up with door frames. So far I have played with various options, including laminated douglas fir, milled plastic strips, aluminum over foam tape. All of the ideas include the notion that they could be removable for inspection without having to grind weld points.

Before I go off the deep end, has anyone seen something like this that I could adopt/adapt?
 
As if by now I am not known to do things differently. My doors close against the round tube. I am not a believer in needing the added structure for the door to close against.
I will simply let the fuselage fabric wrap the tube with it's doubled tape as normal. I intend to then apply a strip of durable polymer tape as a wear protection to reduce damage from entry and egress.
My doors are a rectangular frame with a flange that when closed will cover, call it half the tube. Within the rectangle tube and flange will be a ¼ Rd foam seal such that it's round face will seal to the round frame tube.
This all will be durable and has no long cavities to try and protect over the decades from the elements.
 
As if by now I am not known to do things differently. My doors close against the round tube. I am not a believer in needing the added structure for the door to close against.
I will simply let the fuselage fabric wrap the tube with it's doubled tape as normal. I intend to then apply a strip of durable polymer tape as a wear protection to reduce damage from entry and egress.
My doors are a rectangular frame with a flange that when closed will cover, call it half the tube. Within the rectangle tube and flange will be a ¼ Rd foam seal such that it's round face will seal to the round frame tube.
This all will be durable and has no long cavities to try and protect over the decades from the elements.

I like the idea. As you described this I thought about my Commonwealth doors. They overlap from the outside with a rubber seal. Simple. I don't know why I didn't consider that approach given I was just fiddling with the door latches yesterday.

But the Commonwealth has a partial channel. I looked at the drawings I had and it specified "zinc chromate tape" between the channels and tubes. That's a new one on me.
 
I use weldable primer on the Super Cub u-channel in front of the D window and on the door channels on the Short Wings. Piper didn't do anything and it shows 50-75 years later. It splatters and spits as you weld over it but it has to help. I have thought about sealing between the stitch welds with that body sealant they use on car bodies now but haven't tried it.
 
How about filling the channel with linseed oil, paralketone or ??????????? Then draining the excess out the bottom through a drain hole.
 
How about filling the channel with linseed oil, paralketone or ??????????? Then draining the excess out the bottom through a drain hole.
I think that would be a nightmare. We had a fuselage someone filled with oil and it kept weeping out. Most people fill with oil, let it drain out and weld up the filler hole. I can't imagine trying to cover that, I would be afraid it would ooze out throughout the covering/painting process.
 
Check out what Bob Barrows did on the Patrol I believe it was. He too was tired of the bare metal rust issue under door frames etc.
He planned it out and welded tabs as required to the door frame areas, added nut plates or clip on nuts I suppose AFTER the fuselage was primed and painted. Nowhere left to not get a primer and paint protective coating. Then they bent up the door frames out of aluminum and attached them to the tabs possibly even after the fabric was in place. Lighter, plenty strong, no rust. Sounds like a win win to me. Enough so that’s what my plan is for my build, and that’s where I am in the sequence. Do some work on the tail post and then do the door frames. That will finish my fuselage and ready for final blast and paint.


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Check out what Bob Barrows did on the Patrol I believe it was. He too was tired of the bare metal rust issue under door frames etc.
He planned it out and welded tabs as required to the door frame areas, added nut plates or clip on nuts I suppose AFTER the fuselage was primed and painted. Nowhere left to not get a primer and paint protective coating. Then they bent up the door frames out of aluminum and attached them to the tabs possibly even after the fabric was in place. Lighter, plenty strong, no rust. Sounds like a win win to me. Enough so that’s what my plan is for my build, and that’s where I am in the sequence. Do some work on the tail post and then do the door frames. That will finish my fuselage and ready for final blast and paint.


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Thanks for that. I hadn't looked at Bearhawk.

But this morning I looked closely at my Commonwealth SkyRanger. It does almost the same thing that you describe. Painted tabs on a painted frame; aluminum trim/frames over it that can easily be removed.

But I'm still kicking around Charlie's minimalist idea, too.
 
I have done like Steve in the past with the weldable primers. On the door frame sheet metal I use a Rotabroach to put in a series of access (lightening?) holes half way between the tubing and the outside edge of all the formed sheet metal .......... there are other brands that are the same difference ........... This allows access to the interior portion of the frames. The holes are about 1 1/4" down to 5/8 or 1/2. If you have sand blasted the fuselage, make sure to get all the sand out. Tape up the holes and skip welds with most any kind of tape but leave a place to tape in a tube to pour in your favorite primer. Roll it around to ensure total coverage then drain into a pan for reuse of what's left. It can be somewhat messy but it gives you the warm and fuzzy knowing SB819 will never be an issue for that airframe.
 
June Update

I left off at the end of April having fabricated float attach brackets. I didn't have the drive to actually gather thoughts for an update until now. Things plug along in a haphazard fashion.

I tacked on the float attach fittings. Later I welded them more securely.

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Then I went about making rudder pedals.

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They are pretty basic. I had all sorts of "improvements" in mind, but given my current circumstances, I've decided to pretty much follow the plans and not get derailed.

But following the plans requires creativity, nonetheless.

I'm still kicking around how to attach the channels under the cockpit. The drawings are vague at best. They show "channels" and mention that they should be "radiused." No specs. No pictures. You can figure offsets by looking at other measurements, but, as near as I can tell, it is sort of an improv adventure.

My first improv:

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I've studied pictures of various fuselages online so I think I have the gist of it, but I'm going to fall back on my boatbuilding hit and miss fairing before I weld the things on.

I also re-did the jack-stand for the stabilizers. I don't know how these things happen, but I discovered after 8 months that the screw would run into a cross-brace. Glad I just tacked it last Fall. Rudder still lines up well, at least.

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Part of my life these past months has been devoted to winding up my day job. I'm pretty much a stay-at-home fellow now. Which means no cash flow, so the frugality regime kicks in. I had an Acme screw from my old lathe that I didn't need when I extended the bed. It has 16 TPI square threads. I'm thinking it might do well for the jack screw. I turned it down on the shaft to fit, but I'm still weighing the pros and cons.

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A side project was to see if I could make aluminum pulleys. Apparently I can:


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I am thinking about increasing the bore and using some of my left over delrin for bushings. If nothing else, it is fun to try.
 

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I tacked on the float attach fittings. Later I welded them more securely.

View attachment 56373
Do you have a particular make and model of floats in mind? I ask because the flat tab wire pull which you have "hard" welded MUST align with the cross wires when they are tightened. This angle varies from float model to float model. When these tabs are "fixed" as yours are, it is usually because the angle has been calculated for a particular float. You may need to bend this tab while installing whatever model floats you use.

An alternative welded on fitting would resemble the fitting you have for the strut attachment. This would create a flexible cross wire fitting for a natural self aligning connection.

These fittings are normally supplied by the float manufacturers for a particular installation. Unless you are duplicating the angles for this particular model of float on this particular model of airplane you may or may not have the correct angle.

I agree with Jimbo, use a ball bearing in your pulleys. They make for nice smooth low resistance controls which absorb the extra friction caused by tightening the cables to a proper tension.
 
Do you have a particular make and model of floats in mind? I ask because the flat tab wire pull which you have "hard" welded MUST align with the cross wires when they are tightened. This angle varies from float model to float model. When these tabs are "fixed" as yours are, it is usually because the angle has been calculated for a particular float. You may need to bend this tab while installing whatever model floats you use.

An alternative welded on fitting would resemble the fitting you have for the strut attachment. This would create a flexible cross wire fitting for a natural self aligning connection.

These fittings are normally supplied by the float manufacturers for a particular installation. Unless you are duplicating the angles for this particular model of float on this particular model of airplane you may or may not have the correct.

Montana Floats Series 2200 amphibious . It may never happen, but that’s the target.


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Montana Floats Series 2200 amphibious . It may never happen, but that’s the target.
In that case, you may be wise to inquire of Montana as to what that angle should be. Now would be the time to make any corrections if needed, since you are not yet covered.

Perhaps Jimboflying could help with those angles as his airplane is on those floats? Your installation would be similar.
 
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