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J-4 Cub Coupe

As you know original brakes are not much, basically no differential braking and I can reach them both with one foot from the right to stop at the end of the run out. I am used to the right side from instructing. No big deal which side just a preference for me.


Geo
www.cubdriving.com
 
Glenn: You are correct about brakes. Although the braking is typical "cub" kinda like dragging your feet, I do like to be somwhat in control. Right seat is good as long as you are in no wind. ---geezer Dan
 
If you pump the slack out of the expander tube the brakes work great, which is bad if not careful on a nose heavy plane like a J4. I run 4x25" goodyears and can lock the wheels doing a full throttle runup with 100hp and seaplane prop.

Glenn
 
Well, bump!

i now own the J4 I spent 100 hours in. Much more fun in the left seat. Yeah, one gear leg is sagging. I wonder if stretching and heat treating that spring works? They cold- straighten gear legs and tail springs - maybe we just pull that spring out and stretch it?

I did not look in there while the gear leg was off, so have no idea what I am getting into.

Neat airplane. 22K, and it looks like a show airplane. C-85, electrics, and a wing tank. A similar J3 would be forty.
 
How close are Aeronca springs? A few years ago I was looking at Die springs to see if there were any current "off the shelf" springs available, I did not come to a conclusion but found that having springs wound would according to the manufacturer, "not be expensive" Not sure if that was on his scale or mine?

Leaf springs are cold worked, I expect a stretch and heat treat cold be done. But how good is the alloy originally used and how much more just to have a new one if some other spring could not be sourced?
 
I modified a pair of die springs to fit a set of J4 gear legs. Owner could not find an off the shelf exact match for the originals, so bought some that were a little big on the diameter, and turned them down on my lathe. Worked out great.
 
I have an 11" Sheldon, but am trying to picture holding and cutting a spring. Aren't they hardened by the heat treatment?
 
I have an 11" Sheldon, but am trying to picture holding and cutting a spring. Aren't they hardened by the heat treatment?
If you are just cutting length I use an abrasive wheel. They will cut with a good saw as well since most spring steel is not all that hard. But some are on the outside.
I prefer a 6" thin wheel since they put less heat into the part than a 14" chop saw. The cut end does not need to be heat treated after.
Diameter gets cut with carbide on a lathe, you need to dress the sharps off afterwards.
 
I have an 11" Sheldon, but am trying to picture holding and cutting a spring. Aren't they hardened by the heat treatment?

Turned up a mandrel from a piece of round steel bar that just fit the inside diameter of the spring, and left a flange on one end to both chuck into the lathe, and seat the spring. Drilled and tapped a hole in the other end. Made up a thick washer, and modified a Hex head bolt by center drilling the head. Slide spring on the mandrel, and use the bolt and washer to collapse the spring. Chuck it up in the lathe, and use a center in the tail stock into the bolt head. I used a carbide toolbit when turning, some cutting oil or coolant helps give a better surface finish.
 
Bob, I sent a message to a friend south of Dallas with several J4s. Hopefully he will chime in. His hanger is like a J4 and bicycle museum.
 
Thanks guys. Is this like my Mustang convertibles - special tools to get that spring safely in and out? Or does it just relax when the strut is fully extended?
 
I have an 11" Sheldon, but am trying to picture holding and cutting a spring. Aren't they hardened by the heat treatment?

Bob, a while back I had a run of springs made for the J4A. Upper and lower springs. I think I might have a set left, however, if your J4 has a wing tank, I’m thinking it might be a J4E which has larger springs. Can you confirm the spring size and/or if your J4 is an E model?
it was 21 years ago when I had the springs made. Perhaps they can make a run of the beefier springs.
 
The wing tank was an addition - unapproved until this year. It is a J4A, s/n 4-635. Dan has mentioned you. I would love to buy a set. Thanks!
 
Thanks guys. Is this like my Mustang convertibles - special tools to get that spring safely in and out? Or does it just relax when the strut is fully extended?
If it's like an aeronca oleo and everything is worn out and broken, the spring will be rattling loose. If most everything is good the spring will be under significant compression.I recall one aeroncateer describing a jig bolted to the bumper of his Suburban and jacking the truck up and down to compress the spring.
 
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