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J-4 project-3.14159265359

Sometimes on a solo cross-country I like to spread out into the middle of the seat. Left foot on the pilot's left pedal and right foot on the co-pilot's right pedal.

It's a nice change in seating position. Not sure if your divider would prevent that or if you'd ever do that, haha.

I do the same or move both feet to other side. If you get bored just move over one pedal with each foot and " try" to do some Dutch rolls, fun stuff

Glenn
 
I did that with the inner pedals, as in opposite travel. Took awhile but I got it. I wonder how long it would take for that to come back.

I just connected the pedals to the rudder with a small dia rope, the travel ration is spot on. This is nice since I can keep moving forward and not have to remake parts.

Mounting all the pulleys for the cable runs will be time consuming but they will be where the drawings depict the routing :smile:
 
I made a change at the bottom of the control sticks where the push - pull tube attaches. I now have what appears to be a nice full range of travel on the elevators which complement the rudder movement from the pedals.
It is looking like the cable runs under the fuselage will be "almost straight" as in 2 to 5° changes at a few spots till they need to truly turn. Kind of frustrating since I am thinking I need to utilize guides rather than pulleys along this route. Thank golly that we have some very low friction plastic bearing material available rather than being stuck with Phenolics as in the past.
 
This post is from work I did a week ago,
Here I am getting the pedals tack welded from a bunch of sub assemblies made a year or so ago and now ready for the first trial fitting.
I do have a few changes to make since the outer pedal can contact a frame tube and the inner pedal needs to move a slight amount since there just in not enough room for the brake pedal.
I will now assemble the PAX side pedals, then narrow the set I have shown here and leave them at that point till all the linkage has been built for a true test fitting.
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And later that same day, And now there are four, far from done but they are there.
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Take some 3/8 x 2" Phenolic bar stock, cut a half dozen squares. Drill and ream a center hole. Mount on a mandrel in the lathe. Turn the square to be round. Then with a round nose bit cut a .140 wide groove. Press a flanged bearing into each side.
And wala, some medium diameter pulleys.
Guess I need a few more pictures, I will get them on the second batch.

These pulleys are for the lower elevator run which does not have much angle as well as the rear rudder cable pulleys.
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I am going to touch on these pulleys again. I went down into the shop early to make a second batch.
Here are more images showing the steps from the beginning.
In the band saw, setup with a 1-2-3 block for this 2" material.
Make the cuts which leaves me a bit short, out of 24" of material one gets 11 full squares and a short drop due to the waste during a cut. Being I scrapped one pulley in the first batch I will now have 10 which is fine.
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On the mill, I square the stack against the reamer, center the DRO and change to a drill, then ream the center hole.
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These then get mounted on the lathe, 3 at a time. I am using a 1/2 bolt as a mandrel with two nuts spaced apart in the chuck, quick and repeatable.
Turn the outside then plunge the groove for the cable.
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On the work table, the pulleys, a couple of bearings ready to go together.
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Very nice. I'm curious about your bearings source.

Various sources from all over the world.
The bearings used here are FR188-2RS These being a .250 bore, .500 OD sealed bearing. If I recall these are rated about 250ish lbs radial load each. So call it about 500lbs per pulley, that is plenty.
One can easily go up with the OD and get a greater load rating.
These also lack an extended inner race so it is not a good thing to clamp down on these. In this application these will ride over a 1/4-.028 SS tube with an AN3 through bolt retaining the assembly. As such the bearings could have a bit of float which is not a bad thing.
 
Lots of little parts ordered so I can make the rest of the control cables. With luck these will all be assembled and get swagged in a few weeks.

Till then the pulley for the rudder system need to go in as well as a few rub blocks along the cable route.

I have not done a big phone order with BandB in decades but none of use will be shopping directly with them at any of the shows this year.

I still want to design a manual trim system just in case I do not actually want the electric trim. Better to have all the mounting for it's cable run in place.
But finishing the electric trim needs to be done, basically mounting the gear motor at this point.
 
Going through the camera I forgot I had these shots. I use a construction laser allot on what I build. Here are two shots using the laser to paint the line the cable and pulleys need to be aligned to. These shots you can clearly see how the cable run lights up by the laser.
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I got the elevator trim motor mounted yesterday. Waiting on a pair of limit switches to arrive that will need mounting and probably remaking a part or two. Then the system can truly be test run.
To mount this gear motor I machined a solid coupler to stand in for the flex coupler to provide the best alignment possible. This drive has a square connector while the ball screw has a round shaft utilizing set screws which I expect will be altered with adding a keyway before this goes into service.
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This task was closed out with machining and installing a guide block for the top of the jack screw assembly.
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Now I can move forward with finishing the rudder cables since all components along there path are in place.
 

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With the trim motor in place I have the freedom to finalize the path the rudder cables take.
A few images here starting at the back.
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And from the front
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What is the purpose of the second cross tube? A place to insert a lifting handle pipe?

Correct,
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It is a thin wall stainless tube that is a receiver for a thick wall carbon tube.
Stainless since it will be open to the environment.

I kind of want one up higher but then I need to mock up the main gear to get a better feel when moving the plane around. It could be that all will be fine with a towbar on the tailwheel.
 

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Correct,


It is a thin wall stainless tube that is a receiver for a thick wall carbon tube.
Stainless since it will be open to the environment.

That's an idea I think I'll steal (or borrow if you prefer) ;)

I hadn't though of carbon. When I first looked I thought you were using rebar.
 
That's an idea I think I'll steal (or borrow if you prefer) ;)

I hadn't though of carbon. When I first looked I thought you were using rebar.

Ahh but this is new Chinese rebar :evil:

I welded a short 4130 tube to the airframe on each end with the St 304 tube spanning the width. I think this was a 7/8 .035 Stl 304 tube inside 1" either .028 or .035 bits to weld into the frame.

If I recall the carbon tube is 20mm OD, 2.5mm wall.

Check if you want the handle up high or down low, this one seems OK for carrying the plane but might be too low to just push it around.

Without the front end up at it's proper height I can't really tell.
 
Humm, with the fuselage upside down again a couple of the rudder cable pulleys have been changed out to double groove pulleys. Odd, must be something weird or some sort of trickery going to happen here.
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Sometimes a change is needed, well this might be a bit different than most needed changes. From when I drew then built the aft section of the fuselage it came to be realized a cable path needed to be different than what was designed years ago. Issue is a tube placement was done to allow the cable to pass outboard right next to the longeron. Well, that cable needs to pass more inboard which rendered the tube to be in the way. After days of mulling over it I decided the cable wins and the tube moves.
So I clamped in a guard so I would not nick another diagonal and went in and cut out one end of a tube to move it over a bit.
This is the first stage of moving it.
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Dang. Just ordered 105 feet of stringer material. Interesting how much some material can add up to.
 
And in this cluttered corner of the shop I am starting a proof of concept build of the main landing gear. This is being done in mild steel tube while the flightworthy gear is intended to be a composite spring.
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It is interesting moving around this plane sitting here mocked up with this gear. The door sill is at the middle of my abdomen. The propeller tips will have well over 20" tip clearance when level.
Heck if I have to prop this I am not sure I can reach the blade at the 10 o-clock position.
Yah the AOA looks nice but with the wing I will have and the huge flaps I question if I need this angle. Yah it will make use of the slats but in my mind they are for safety in flight.
For a younger and more agile person this would be sweet, but needing a step ladder on each side to enter or egress is not appealing to me.
Decisions-decisions, humm.
 
It appears as though your plan is for a one piece bolt on gear.
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Why not just make two for flight test purposes?
 
This morning I pretty much determined I will shorten the gear legs about 5"
Where the axles bolt on will have more than one set of mounting holes allowing some option as well as changing tires and wheels.
If I was 6'2 and had two good legs I would stick with what I was mocking up.
Yes this will be a one piece leaf spring. I would really like to get it right the first time. The steel tubing is inexpensive and fast to work with, but will in no way withstand actual operations, even short term.
The composite gear requires a mold, time consuming and expensive. There will be hard points to be machined that get molded in the layup.
Then the carbon tows, innegra and S glass along with $200 of resin, much of which may go to waste due to short shelf life.
I really am hoping to do this once.
Aspects as stiffening or softening the spring rate can be altered, but the torsional stiffness and general dimensions are pretty much locked down once the fabric is in the mold, especially once I resonate it.

I still consider going with an Olio type gear similar to original. I would utilize modern motorcycle fork legs, I have not done any recent drawings or calculations since I decided to go with a leaf.
 
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I am fitting the stringers, starting up top since most of the mounts under the belly were done previously. I am liking it.
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Once the top is pretty much done I will undertake the sides, They will be tricky due to the baggage doors.
 

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Charlie can you weigh the major components before assembly - wings, empennage, fuselage, FWF? Might be worth the effort. Not sure if covered or uncovered.

Gary
 
Sure,
It has been some time since this has been on the scales and allot has been done. Next time I do I want to weigh the fuselage with stuff in it as well as bare tubes. Both before and after cover too. Some of the add ons be they the pedals which seem heavy in my hand while other parts seem light. It will be interesting where it is at compared to what is in my spreadsheet of weighed and estimated parts.
The wings are a long way off but since they are metal skinned they will not be apples to apples with Cub parts. Maybe compare to Bearhawk parts. I expect mine will turn up heavier. I tend to not skimp with wing structure.
The flaps and ailerons which are designed in both composite and metal, One or the other. They might actually end up as composite spars, ribs and trailing edges with fabric cover.
I still have a desire to build the rudder and elevators in fabric skinned composite structure. Need to get close to the final weights to see what is needed to balance this out before I build superlight tail feathers.

The engine will have a sheetmetal oil sump, forward facing HA6 carb to start with. Denso Alternator and Skytec starter. The flywheel will be receiving a day on the mill and lathe as well. That did not get done last winter and may not be till next till to become important.
This will have a 4 into 1 header that should not be bad weight wise.
 
Curious why you are choosing metal wings over fabric? I was always told that fabric wings perform better at lower speeds.

Web
 
Yes fabric wings perform well at low speed, because they can not achieve a high speed.
Low speed and light weight are not my goal here. It might be feasible that a fabric wing could fly slower, but it is also considerably slower at cruise or high speeds as well.
Everything I have designed and built has a minimum of 5:1 speed ratio. This plane should exceed that by a fair margin.

The airfoil I have chosen, one of Riblett's optimized has a good chance of a fair amount of natural laminar flow. Being that laminar flow is not necessarily just fore-aft on a wing but actually has a fairly large spanwise component, this leaves out any rib-fabric construction for efficient higher speed operations.

FWIW, The airfoil I have selected is not what is utilized on the Bearhawk aircraft.

Oh, my selection of metal wing actually has more to do with what I can build with a lack of skilled helpers. The old brush & bucket layups need more hands than I can get here.
Learning more about resin infusion is making me think again about composites. I have 3 real good wet vacuum pumps here ranging from 3/4 HP to 5 HP so I can draw down anything. Dry layups are not hurried.
 
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Top stringers revisited,
Yesterday I got the fiberglass tubes trimmed to fit in place on top of the fuselage. Today I undertook making some saddles these tubes will be supported on. The saddles are used where the stringer rests on existing structure. For these ¾" OD tubes I make these saddles from 7/8-.028 wall tube, split in half, then formed to fit snug to the stringer tube and welded into place.
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This is one of six saddles fitted today, the rosette weld will need to be dressed down.
At the very front the stringers were trimmed to mate up to some structure,
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And then a saddle was formed and welded in for the stringer to fit into.
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