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J-4 project-3.14159265359

I am a new J4 owner. Still six months away from the first annual, and all I know about maintenance is what a giant PITA the seat lacing is. I anticipate master cylinder maintenance - they are acting like reservoir masters.

Not above swithing to Grove 95 masters - I love them on my J3. Does it require any welding?

And - did we do ok? Semi-show quality, with 70 hr C-85 and starter - under 25 grand?
 
Bob, after the first year I redid my seat bottom and back with 5 ply 3/16 plywood
I think masters cylinders are a 37 Plymouth wheel cylinder?

Glenn
 
Bob, on your masters I would expect yes they would need welding. If not welding then some fabricated brackets made. The J3 are all above the floor with the pedals swinging sideways. The J4 has the masters below the floor with pushrods to pedals that pass upwards through the floor. I do not have good pictures of my masters although they are here in a building on my yard.
I doubt wheel cylinders would be right for the job. If I were to go at changing them I would look into Girling, Tilton or other single masters as used in race cars although fluid compatibility may be an issue.
 
The tube that carries the brake pedals needs to be disassembled and the arms on that tube that transfer force to the master cylinders need to be lengthened by an inch to get enough throw for the Grove masters. It's a simple weld job that can be done outside the airplane. From there on it is just nuts, bolts, and plumbing. You can get all the details from Terry Bowden (barnstmr@aol.com) who is a DER-V. Mention the work he did on my J-4 and he can set you up to get get approval to install Grove master cylinders. Robbie Grove at Grove will put together the parts you need and the AI who is doing your annual can supervise and sign off on the 337 submitted with the DER-V paperwork. Of course, my J4 already had Grove disk brakes before I got it. They just didn't work much at all. Mismatch of high volume/low pressure masters with low volume/high pressure calipers. The replacement Grove masters did the trick.

Sounds to me like you practically stole that J-4. I'd need more details to tell more but it sounds like a great deal.

The ergonomics of the seat is pretty bad. I think it was designed originally for a goose - short legs, long neck. cubdriver2 has the right idea to replace the sling. That's my next project.


 
Bob, my friend Dan Fogal restored his J4 over the last 10 years. Hears his brake rebuild report


This is my brake set up under the floorboards. I made an access panel to get to them from below. I believe they are 1938 Plymouth master cylinders. The reservoir is mounted on the firewall and fills both cylinders. There are check valves in both "fill" ends of the units. The rubber boots came from a farmall Cub touch control system! They work quite well.
Kanter is the company in NJ that supplied the rebuild kits.800-526-1096
Hope this helps.






Glenn
 
Those are Wagner Lockheed master cylinders used on prewar J3s and J4s. They were used on many vehicles in the 30's. Napa will have the seals. Cleaned up and resealed they will lock bushwheels. Be careful with to much brake on the J4. The 4 is the ugly sister of the Cub line but stock and light its a nice flyer.
 
Current task, Machining the pivot tube for the tailwheel. This will support two angular contact ball bearings so when in flight the lack of friction will allow the most tactle feel of the rudder. Is this necessary, to most people, no.
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The stainless disk will be at the bottom, this will be milled into a cam that will release the TW lock as needed during ground operation.
 

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Other then when spinning I have never had a need to feel what the rudder is doing. My butt feel whats going on and tells my feet what to do

Glenn
 
Next step on the tailwheel is to mount the bearing holder on a rotary table so I can cut the pathway for the TW release. In prep for this I had thinned the stainless disk from 3/8 down to 3/16.
I first cut a flat to the depth the small radius will be.
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Then I cut the small radius and ramps.
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This will be followed with hollowing out the lower face of the disc.
Not sure how much more I will get done before flying out to OSH on Saturday morning.
 

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One of my sub-projects is to make a rotary table. I can think of a number of handy uses for it. Of course, the practical approach would be to buy one, but...why do that when you can spend lots of time making swarf?

Really nice detailing, Charlie.

Vic
 
I have been looking at buying one of the small imported rotary tables, either a 3 or 4". Just have something in my mind to not do so. The two I have are very good quality in a 12" and 18". They are stable such that the cutter will not pull them. I am afraid the small ones might have some play in the gears that will not allow running the cutter either direction without the cutter grabbing.
Both of my tables need to be lifted with a chain fall onto the mill such that changeover is not a trivial thing to do.

Making one would be cool once you find a decent worm gear set to build with. One thing to consider is the indexing, the arc I cut is 35° either side with a 15° ramp from perpendicular, the indexing scribed into the work table is kind of needed when the angles matter.
 
Can you tell stainless gets hot when you cut it? and this was with a synthetic lubricant.
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I could thin this down more since there are essentially no loads on the outer diameter, just at the ramps where the lock pawl will be lifted to unlock the wheel.

I want to do more but other tasks to do. The next 1500-1900 images taken by this camera will be out in Wisconsin.
 

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After a week out in the midwest snapping 1376 photos I got to spend an hour in the shop with fitting then tack welding the tailwheel pivot tube to it's arm. I thought my camera would pass the 20,000 image mark but it is a few shy of that still.

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Wow it has been some time since I have been able to work on this. I have when I had a chance do some updating and cleaning up of some drawings. A few lathe turnings for control system pivots for rocker arms and pulleys.
Last night I mounted up the rear case for the engine so I can make changes to the oil flow from the pump. Not something anyone pays attention to one might say.
New oil outlet right from the pump and goes back into the engine through what originally was the relief valve. The relief valve will now be where the Vernatherm originally was which is right at the pump outlet and not after the cooler then filter as is normally run. Why Lycoming still runs oil through the cooler before filtering and regulating it is beyond me.
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I fitted a tube today, well that sure does not sound like much. Well this tube spans what will be the aft end of the top cabin skylight, it has 3 bends and four miters fitting the longerons and diagonals coming aft or the rear spar. It was well over 3 hours to fit this tube. Being it is .028 wall tube it all needs to be spot on which it is, It did come out very nice though.
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Material arrived to make the control sticks so I will pick away at that next.
 

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As I am working on the top of the cabin I want to move forward with the mounting for the skylight and top of the windscreen. This will be forming quite a few curved and stepped thin sheet metal pieces. All of these will need special tooling made to form the parts.
I am beginning to think I am better off making up simpler tooling and laying up the parts in composites.
For me most of these are easy since I have glass panels out of a sliding door that I tape any special tooling onto and I can either wet layup parts or bag them. Winter is not the most efficient time to me to undertake this type of work since I need to heat another building which I would just assume not do.
But maybe I should just concentrate on making the tooling and be ready a half a year from now when it is warm out again.
I did spend some time today uncovering my 8' sheet metal brake. I keep it covered over with large cardboard sheets simply so no one knows about it and comes over begging to bend stuff in it since mine is one of very few large brakes with no nicks in it. They can go use a press brake.
Heck I will have enough to do on a press brake since I expect that is how I will form the ribs.

The spars in my wings are going to be formed like an RV is done. Mine will be a long formed C shape with formed angle and flat stock spar caps.
Even though I have sheet aluminum in both 21 and 28' lengths here I might decide to utilize splices and try to keep the wing skins full length. I do need to order more material in and that needs to wait till spring since I do not bring full size trucks in during the winter.
This should be interesting.

I also will need to start making the tooling for slats, flaps and ailerons since I intend these to be composite construction.
 
I also will need to start making the tooling for slats, flaps and ailerons since I intend these to be composite construction.

I'll find that interesting. I was shaping some polystyrene boards into flap shapes with an idea of getting some empirical data on a rig in the back of a pickup. I may never get to that project, but I epoxied some left over fiberglass over one of them and started to think, "Hmmmm." The sections felt pretty light and very stiff.
 
Glass over foam is still a viable way to build things. Here I am 34 years ago building a wing.
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Later in that project we started wrapping the parts with Peel Ply, Dacron sail cloth which greatly improved the layup. Within a few months I had my first of the four vacuum pumps I now use for vacuum bagging and now infusion work.
Having the full foam core adds a fair bit of weight but it is a forgiving structure.
 

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bearhawk wing building starts at 2.08, sortve interesting.https://www.youtube.com/watch?v=V2oe2ZF61t8
I am getting more interested in the way Bob B uses the angle material to attach the ribs to the spas. I had not been a fan of that but I have fewer skilled hands around to help with the work than I used too.
I had watched that video a few years back but I will go through that one and others to see just how I should go about this.
Maybe it is time to spend more time on Ya'll tube some evenings.
 
The way Bob mounts the ribs makes for a smooth skin transition. You have a little wiggle room for lining the ribs up.
 
I am seeing a few benefits to the way Bob did the attachment of his ribs, alignment being a big one but monitoring overall spacing of the spars as well. My wing will have no theoretical twist built in. Until I know just how accurate my rib forming will be, this being MDF forms in a steel frame on a 55 ton press. The press is actually a 10' press brake that I am making all my tooling for.
In the past I have used rather conventional construction. I am looking forward to see how much structural bonding and other changes I choose to do.
 
Yesterday I started on making a centerstrip over the cockpit that will support the skylight as well as house the trim indicator. at this time I have a part roughed out but it is far from usable.
First step, not shown was to form the C channel which is made from .024 304 stainless.

Next was to make a set of rollers to form this channel, these are nice and snug to the material with the mis belief I would get the desired curve without the sides wrinkling. Didn't work.
The rollers mount in the milling machine allowing me to creep in on the radius of bend desired. This it did well and being the airfoil shape has a varying curve.

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With the strip set in place I like what I am aiming for.
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Being a C channel I can not work this on a shrinker stretcher not that this thin stainless tolerates being formed that way. I am considering making some tooling to hammer form the sides but maybe another option,
I do have a friend with a planishing hammer so once the freezing rain passes by I may take a drive over there and either salvage this or make a new one.
 

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I made a planishing hammer using a rivet gun with a mushroom head. Made a large C shaped support out of wood similar to an English wheel with a bucking base out of a piece of railroad track turned on a lathe and a foot pedal to control the rivet gun trigger. Thin stainless will be difficult to compress with minimal wrinkles. The metal doesn't move easily. At least not like aluminum.
 
I keep thinking I should make this in aluminum, it is so much easier to work. One reason I chose the Stl is it is so bloody hard, at least for me to work this. It is kind of a classroom project.
Aluminum, I would make two hard rollers and stretch the backside of the C.
Mild steel I could work the sides on tooling I have here, but I want a paint free part. Between the riveted on nuts for the polycarbonate top surface and the moving parts inside I truly want a maintenance free part.
 
I'm 64 7/8. Anything I build, paint or polish will be the next owners problem. I'm surprised your rollers allowed that much wrinkle. Looks like they fit the outside of the channel pretty snug.
 
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