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J-4 project-3.14159265359

I find even after designing and building for going on 50 years, I still find every project a collage course. And hope they remain so for another decade or more.

One interesting point I am at, working on numerous parts going in the back of the plane. Just what is the balance to how heavy or call it reserve strength is designed in or how technical and light should the part be.

I would hate to spend time and money to build beautiful carbon fiber parts just to add lead ballast right next to them once the job is done. So much is not known when you pioneer a design.
The vertical shaft for my trim system will have a delrin guide bearing running inside a milled out ¾ Sq 304 stl tube. This one foot tube being .065 wall will be close to 2lbs on it's own.
An option to make it from either 4130 tube with an .035 wall or form it from 304 sheet will both be about a pound lighter.
The 4130 would either need an anti corrosive coating maintained for life and the formed sheet metal is time consuming and finicky to get just right.
I would hate to keep going in the tail to maintain this part because I built it real light just to also check the block of lead sitting next to it.

Kind of goes with the rudder & brake pedal assemblies. These are designed to be built in either Ti or steel. Is the Ti worth it?
 
As I have been picking away at the trim system with many revisions of the drawings, I kind of have it locked down. Well that kind of means it is partially built now.
Here is a render of the latest trim system drawing, The bearings are not in place so it has some oddities to it.
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And that part in place,
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And it really in place, although far from complete.
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My trim system is moving forwards to the point I have been able to run it from the jump pack. I like it.
To this point I have not had a clue what it's travel speed would be. Running from the EarthX pack I get 3.75" travel in 12 seconds.
I still do not have a clue what that will mean when it comes to trimming the plane in flight. Will it be to fast to make fine jogs? I doubt it will be found to be slow.
Next with this will be to setup limit switches and solder up a set of relays and run it from the switches in the control grips.
Well not to mention I still need to mount the motor to it's frame.
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My trim system is moving forwards to the point I have been able to run it from the jump pack. I like it.
To this point I have not had a clue what it's travel speed would be. Running from the EarthX pack I get 3.75" travel in 12 seconds.
I still do not have a clue what that will mean when it comes to trimming the plane in flight. Will it be to fast to make fine jogs? I doubt it will be found to be slow.
Next with this will be to setup limit switches and solder up a set of relays and run it from the switches in the control grips.
Well not to mention I still need to mount the motor to it's frame.
View attachment 46284

12 seconds is same as a carbon cub one.


Sent from my iPhone using SuperCub.Org mobile app
 
12 seconds is same as a carbon cub one.
Sent from my iPhone
Thank you Mike,
I tried jogging this one, obviously with no load on it, it might be hard to move this much less than an eighth of an inch. I did get one dab with just a tiny bit of movement but that might be hard to repeat.
Being this is a ball screw I would not expect air loads to bind it up much and there is plenty of reserve torque in these window motors.

In one of my track cars I use a window motor driving a 3/8 acme thread rod to slide the pedal assembly and that one can be driven a tiny bit at a time. That I expect could be due to the friction in the screw but may also be from using the Odyssey battery which has considerably less power than this jump pack.
 
What was that saying, "Oh Snap". Well when you hear that when working with your last 5/16 ball mill when working to make an elevator bellcrank that will be the interface between the push pull tube and the cables traveling aft. Oh well, it will be better part of a week to get a few more in without paying stupid money. Heck the house is going to be filling up for the week for our end of year and new years party so I doubt I will be in the shop much anyway.
 
What was that saying, "Oh Snap". Well when you hear that when working with your last 5/16 ball mill when working to make an elevator bellcrank that will be the interface between the push pull tube and the cables traveling aft. Oh well, it will be better part of a week to get a few more in without paying stupid money. Heck the house is going to be filling up for the week for our end of year and new years party so I doubt I will be in the shop much anyway.
Ouch. I think I've heard that in my shop, too.

Boatbuilders have a "moaning chair." Mine gets a fair amount of use still.



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Ouch. I think I've heard that in my shop, too.

Boatbuilders have a "moaning chair." Mine gets a fair amount of use still.

If I could have just heard the "Oh" from that cutter bit I would not have heard the "Snap". This is where CNC is nice, as long as the tool path is generated right.

I keep trying to remember back to that first boat I built, plenty of curved plywood, neat little boat.
I still dabble in boats but it is structural restoration now. All custom resto work actually. Last was a Glastron CVX20 that had not had a cover on it for a decade or two. Great running boat and is sweet in rough water.
Current build is a Superboat Legend, This is a 21' offshore outboard. Thy did not encapsulate the balsa core in the fore deck properly so that delaminated. A few areas in the aft portion appear to need some core and it is recommended to lift the fuel tank out and add core. When build they thought just foaming in the 60 gal tank was sufficient but apparently not. Mine seems fine but who knows.
And I am collecting parts for another 20' Glastron, this will be a V8 powered surface drive boat. Should be cool.

But this plane is my main project for the next few years.
 
Are you planning to have limit switches at top and bottom of travel?


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Are you planning to have limit switches at top and bottom of travel?

Yes definitely. I am at the point I can design that portion of the hardware.
The switches will be a low current control circuit along with the toggle switches on top of the control sticks with relays driving the motor.
I have considered making a circuit board and using transistors for the switching but I am not sure I will go that way.
 
Just an FYI, have a CC FX3 that has a similar setup. Recently had a problem with the wires to the limit switches breaking due to stress when the trim wax full up or down. As I are doing this yourself you will no doubt do a better job than CC did,
But just something to keep in mind, and when that system fails you have no trim in either direction. Lots of little lessons here. Good Luck with your project.

DJG
 
The switches are prone to be the least reliable part with the wires, depending what is used and the strain relief on each one being the second reliability issue.
The switches I intend to use will be the same as I have on outboard jackplates I build for the performance marine industry. Granted I have a small market with a few that have been in use for a decade now.
The tail of the plane will be a totally different environment between vibration and moisture conditions.

Giving thought to what you bring up makes me consider an override circuit that can take the switches out of the circuit. Not something I had given thought to but I should. Easy enough to include.
 
The switches are prone to be the least reliable part with the wires, depending what is used and the strain relief on each one being the second reliability issue.
The switches I intend to use will be the same as I have on outboard jackplates I build for the performance marine industry. Granted I have a small market with a few that have been in use for a decade now.
The tail of the plane will be a totally different environment between vibration and moisture conditions.

Giving thought to what you bring up makes me consider an override circuit that can take the switches out of the circuit. Not something I had given thought to but I should. Easy enough to include.

Would definitely recommend some way to allow the trim to move in the opposite direction so you don’t end up stuck in full up or down, I have sent the same request to CC, will be this time next year getting their response!!
 
I've pondered about limit switches for this application. I assume that they would be normally closed and interrupt the circuit when the limit is reached. An override would be easy to address that.

But mechanical switches back there still bug me for some reason. Seems like a magnetic sensor or maybe an electronic torque sensing circuit would be more reliable. Otherwise, why not just have threads run out so it can't push too far? Use a spring to provide tension for reengagement on reversing. Just tossing things out there.

I'd still want a hand-driven backup, I think.
 
I've pondered about limit switches for this application. I assume that they would be normally closed and interrupt the circuit when the limit is reached. An override would be easy to address that.

But mechanical switches back there still bug me for some reason. Seems like a magnetic sensor or maybe an electronic torque sensing circuit would be more reliable. Otherwise, why not just have threads run out so it can't push too far? Use a spring to provide tension for reengagement on reversing. Just tossing things out there.

I'd still want a hand-driven backup, I think.
Correct, the switch will be set up as NC and open at limit. Easy to over ride if failed.

This drive motor utilizes a worm gear arrangement. There is a fair bit of inertia in the motor such that by the time the current rises the worm screw would be at hard stop. Part of that being the drive unit originally was lifting a window in a car and can do so when everything is frozen. Not sure if they can move a window if it is hot out since everything is air conditioned these days. With the ball screw I am using there is very little load on the system.
The other thing with current sensing is determining just what the true current draw will be under differing air loads and environment conditions.

The limit switch I use is a DPDT switch with the flexible arm to actuate it. I have broken one but not had one fail, yet.

I have had my mind on a manual backup, I intend to build a full manual trim system for the plane, then toss it into a box for the day I do not like the electric. I have yet to figure out a clutch system for this type of motor. Doesn't mean someone else knows just how to do it.

Glenn, It might be if I build in the manual trim that a suitable drive would be brought to my attention. I know they are out there, it's not like I have not worked on my share of them in the past.
Being this drive at least with no load does not offer much resolution, as it I do not see that you could move the stab, "Just a touch" It might be I only need tiny bits of trim, till I pull a fistful of flaps in.
 
Elevator bellcrank.
I decided I did not want to wait for an order of ball mills so I pulled a larger bit out of the drawer which would still allow me to creep in on the dimensions I want.
This allows me to smile going into our year end party knowing I have roughed out another step of this build. I never brought the camera down while the chips were flying but here are a few shots.
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With the bearings pressed in place the spindle slides right in. This spindle will now be welded into a cross tube under the floor aft of the seats.
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With the assembly up on the kitchen table it has the REP bearings in the outer holes for the cables back to the elevator, inner hole port side has the push pull going forward to the sticks and the inner hole right side is available should an autopilot be utilized.
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One detail of the spindle, looking from the underside it has the nut that retains the bearings, this will more than likely be an MS 21042 locknut. The center of the spindle is through drilled and at this time threaded, this allows a through bolt with a nut on the topside essentially double nutting the bearing assembly.
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Very little chance of failure or binding in these parts, and being most every part of all the control systems will ride on anti-friction bearings it will only need a light touch to fly.
 

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Like a small gear motor and belt that turns the original crank in the cockpit

Glenn

This is exactly what I am building in my cub.
It is using a small gear motor and is belt driven. If it fails I can yank or cut the belt off and just spin the pulley next hand. My cub is already together and flying so I was looking to make it electric trim without tearing into the tail. So far I mocked
It up on the plane and ran it up and down just to test the function and durability before I make the bracket to permanently mount it.


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Trim motor speed.
With a house full of happy friends for the holidays one would think I would get visions of dancing sugar plums in my head.
But no, I get visions of a 555 IC timer circuit utilizing the controlled bleed down of a capacitor to vary the PW output to my trim motor so the first half second the motor will run at 1/3 speed but over the next two seconds will ramp up to full speed.

So why is it some of my long time friends just don't think I get into the holiday spirit sitting at the table getting a sore butt while sipping on a very nice scotch that arrived in house.
 
With a lull in the pleasant activities as we near the last days of our holiday week here I took some time to play in the shop. I finished a few details in the drawing for the rockers needed for the rudder pedals I took the time to clamp a chunk of aluminum on the mill and drilled the holes. Working on a manual mill I curently print a drawing to make parts from. Many years ago I placed a laptop next to the DRO which personally worked better.
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More work done on the rudder rockers, With my vertical bandsaw broken down I bought a fresh blade for a local shop's saw since he has not setup for aluminum. Cool saw though, it was made between 1901 and 1909 when the company was bought by Crescent, the same company which later became know for their adjustable wrenches.
Being right about zero F this morning when I headed over there my camera chose to stay home, here is what I cut out.
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I followed with some time on my 18" disk sander,
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Then clamped them in the mill and routed out where the rod ends go.
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More later
 

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Very cool. But - - - what should we neanderthals with only hacksaw, hammer, and vise do?

:-? Well, when I was getting out of high school some 46 years back I began buying tools. At that time I was building bicycle frames and working as an airplane mechanic.
I spent most all my money on tools to the point now in my mid 60's I have lots of tools, and stuff but no money to do much with them.

Before I had my own major tools I found small shops that kind of took me under their wing and did much of my critical machining for me for quite fair prices.

I had a sad moment a few years back when a school friend told me of an old gent who just passed away in, he had a machine shop in what had been a chicken coop on his land in Conn. Only chicken coop I ever saw with endgrain wood floor. I did not recognize what that meant at the time. I had forgotten about him over time but realized he was one machinist - tool maker who guided me on the path I have taken.

But I will say, to compliment the hacksaw, hammer and vise, The vice should be a good and pretty big one since it will be an anvil as well. A good hand held angle grinder, I greatly prefer flap wheels rather than stone. A stable drill press with a two axis movable vice on it. I have clamped lathe bits in the vice and the part to turn in the chuck. Since many of the through tube bushings are not real large this works fine.
Then end mills can go in the chuck and the work piece in the vice.

Measuring tools are important, a Mitutoyo digital vernier that reads out to 4 places is indispensable. Any one that only reads to 3 places or so far all the other brands at my place are just tossed in a corner. Most of the other brands just eat batteries. I have had $80 verniers that ate a battery every half hour.

Neat thing about the projects we are doing is most machine shops think we are the coolest people in the world. Yes some think we have a death wish, but still take interest in our projects.
I know I take interest in most anything someone is dedicated to build.

And I will say, I am sure glad I did not have to do 15" of cutting in this ¾" bar of aluminum with a hacksaw. I could do that 40 years ago but I no longer have enough use of my right arm to even try that now. I have done it though.
 
Well, that was partly in jest - I used to own and operate a machine shop, but since I sold the business I'm mostly back to being "innovative" - or borrowing friends' machines. I do like your post!
 
I kind of wanted to write that bit about tools for those who stumble when it comes to making parts. It is generalized but touches on some bits I found of value as I grew threw a learning curve. There is some usable info for some and might go against what others have learned or prefer. After all there is more than one way to play.

Today was making the mounting pedestals for the rudder rockers. These were machined from a 1" bar of steel and weld up under the main lower carry through, they are offset to clear the control stick torque tube while not interfering with the leaf spring in front and over them.
Even though the camera was in the shop today it was not used till I was done making chips.
The first shot is with a plastic bar set in the saddles.
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All the next shots were blurry, should have left the overhead lights on for the camera, it's getting moody in it's old age. Heck it is just over two years old and is very close to 20K images taken. Hope to treat myself to a new one before OSH.
The rod ends attached on the rocker are not flight worthy, just used for jigging.

The engine comes off tomorrow and the fuselage gets flipped over to work under it's belly for some of the pedal system as well as I am ready to make the brace struts for the horizontal.
 

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Engine is off the plane and my camera understood it's task and focused on the the mounts this morning.
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