bob turner
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without getting way too carried away, let me excerpt a post I did a number of years ago for the Aeronca. Look down at the bottom for part numbers. I will post a link, and maybe a more succinct parts list. The Cub is lots simpler.
We have been operating for a month with copper lines - two of them, terminating at the master cylinders and calipers. I did some testing, and determined that the gear leg flex, spread over 18" of curved line, did not exceed the elastic limit of the copper.
The owners had the option of flex lines, and so we are about to install them - one at each caliper, and one where the lines come out of the belly behind the inner gear leg bolts.
The choice, of course, is between Aeroquip and automotive, and I put automotive in the 337. I am inclined toward auto, since it is tested to much higher pressures, seems to be lighter, and is a bit less than half as expensive.
From about 1930 through 1980, automotive standards involved pipe threads and what are called "inverted flare" connections. Now, of course, every auto is different, and you simply cannot buy standardized anything, let alone brake hoses. But, surprise! The Piper Cub brake hose is pretty much the 1967 Mustang brake hose, with a female #4 inverted flare on one end and a male 3/8-24 on the other, set up either to bottom out in a threaded hole or to mate with a #3 inverted flare fitting.
So at the caliper we use a 90 degree fitting - 1/8" NPT to #3 inv flare, Weatherhead part #403-3. The other end of the hose fits the copper line with a tube nut 105x4. Of course this is all 1/4" soft copper line. Aluminum is also ok. Use care when flaring - examine the flare with 10x magnification, in sunlight.
Then, at the top of the inner gear leg, the copper tube goes in to another flex line using the same tube nut/flare. The flex line then goes into the belly, up, and forward to the master cylinder. Matching the male end of the flex tube to the copper line from the master cylinder requires a #3 inv flare fitting - Weatherhead #202x3 - and a fitting up to the #4 flare -Weatherhead #252-4. These must match, with a male pipe on one, female on the other.
At that point, it is a straight shot with another short copper line with two tube nuts, into a Weatherhead #352x4, going into the master cylinder port.
The hose itself is NAPA 36549. You need two or four, depending on whether you mind copper going to the caliper (most J-3s are set up that way by STC).
I can give you a complete shopping list, including the Edelman cross-references if you need them. If you try this, you will be delighted with the brakes, I promise.
We have been operating for a month with copper lines - two of them, terminating at the master cylinders and calipers. I did some testing, and determined that the gear leg flex, spread over 18" of curved line, did not exceed the elastic limit of the copper.
The owners had the option of flex lines, and so we are about to install them - one at each caliper, and one where the lines come out of the belly behind the inner gear leg bolts.
The choice, of course, is between Aeroquip and automotive, and I put automotive in the 337. I am inclined toward auto, since it is tested to much higher pressures, seems to be lighter, and is a bit less than half as expensive.
From about 1930 through 1980, automotive standards involved pipe threads and what are called "inverted flare" connections. Now, of course, every auto is different, and you simply cannot buy standardized anything, let alone brake hoses. But, surprise! The Piper Cub brake hose is pretty much the 1967 Mustang brake hose, with a female #4 inverted flare on one end and a male 3/8-24 on the other, set up either to bottom out in a threaded hole or to mate with a #3 inverted flare fitting.
So at the caliper we use a 90 degree fitting - 1/8" NPT to #3 inv flare, Weatherhead part #403-3. The other end of the hose fits the copper line with a tube nut 105x4. Of course this is all 1/4" soft copper line. Aluminum is also ok. Use care when flaring - examine the flare with 10x magnification, in sunlight.
Then, at the top of the inner gear leg, the copper tube goes in to another flex line using the same tube nut/flare. The flex line then goes into the belly, up, and forward to the master cylinder. Matching the male end of the flex tube to the copper line from the master cylinder requires a #3 inv flare fitting - Weatherhead #202x3 - and a fitting up to the #4 flare -Weatherhead #252-4. These must match, with a male pipe on one, female on the other.
At that point, it is a straight shot with another short copper line with two tube nuts, into a Weatherhead #352x4, going into the master cylinder port.
The hose itself is NAPA 36549. You need two or four, depending on whether you mind copper going to the caliper (most J-3s are set up that way by STC).
I can give you a complete shopping list, including the Edelman cross-references if you need them. If you try this, you will be delighted with the brakes, I promise.
