Any further ideas, experiences or pictures would be very welcome!
What worked back in 1934 isn't necessarily the best for today's environment. I'm pretty sure Anders Anderson designed the Jungmann to operate off grass runways. Considering the number of Buckers operating on hard surface runways today, there is a need for better brakes.
The original mechanical brakes work ok. They will hold the airplane for a run up (barely) and they will stop a ground loop (barely). One nice thing - you don't have to worry about ending up on your nose. But you must adjust the mechanical brakes as the brake shoes wear and another issue arises when the wheel bearings wear. Loose bearings cause the wheel hub to wobble. Since the tolerance between the brake shoes and inside of the wheel are close, the wobbling wheel hub rubs the brake shoes without any input from you.
Adding hydraulic brakes to a Bucker is not simple. The original pivot point for the arm that pulls the brake cable is close to the longeron and there is a diagonal tube that gets in the way. Several people have converted their Jungmann to hydraulic brakes and I made it a point to study them. It was interesting to see how each person came up with their own solution to the problem.
Master Cylinders
Let's start with geometry. The rudder pedal pivots forward and aft. If you hook the brake master cylinder to a fixed spot on the airframe, pushing the rudder pedal forward pushes the brake pedal backwards. Some people like this because when full rudder is given, you have easy access to a rearward protruding brake pedal.
If you hook the brake master cylinder parallel to the rudder pedal (like welding a tab on the bottom), pushing the rudder pedal keeps the brake in relative position. When you apply full rudder, the brake pedal stays the same and you must depress it further to actuate the brake.
Some people don't like the brake pedal coming back as you press the rudder, but I have found keeping the brake pedal parallel is harder to press when you add full rudder. For people who like the rudder pedals at the far forward position, the brake pedals hit the vertical tubes you see in the picture. You can push the brake pedal all you want, but the tubes won't let it go anywhere. At full rudder deflection, really the only point at which you really want to have good brakes, they may not work!
Somewhere in between may be the best.
OK, lets look at how people solved this:
Woody Menear come up with a solution without welding anything to the fuselage frame. He made a parallel tube that clamped to the pesky fuselage cross tube. On that bar, he attached his master cylinder.
This solution was simple and worked well. You had to position the tube to get that perfect "almost parallel" pivot point on the master cylinder. When you push the rudder pedal, the brake comes back just enough to allow easy actuation.
Talmadge Scott (possibly via John Hickman ?) came up with an even easier solution. This one simply ran a bolt and a spacer through the original brake cam pivot point. It requires that the operating arm is moved from the outboard to the inboard side of the brake pedal and is extended forwards to meet the master cylinder.
Notice the larger distance between the rudder pedal pivot point and the master cylinder pivot point. when applying full rudder, the brake pedal will come back further than the Menear set up.
Here is another view:
Again, some people like that.
Another solution was tried on my Jungmann and refined by Steve Beaver. We made plates to create an artificial floor for the master cylinder pivot point. The plates were clamped to the fuselage tubing:
Here is a view of Steve's plate:
Here is a view of Steve's plate:
Just when you think you have seen the perfect solution, another ingenious person designs another ingenious brake solution.
William Cox decided the original rudder pedal pivot and the original mechanical brake cam pivot were perfect spots to attach his brake solution. Using some square tubing, he came up with this:
It is very simple and effective.
Here is one more solution to the master cylinder location. In a YouTube video of a Jungmann flying some serious aerobatics in Switzerland, I took a screen shot of their brake installation.
This one hinged the master cylinder right on the floorboard.
So, as you can seem there are several ways to mount the master cylinder. A big part of the installation is how you attach the master cylinder to the rudder pedal. Again, I have seen several solutions, each one requiring some welding.
This one welded a nice, strong bracket on the pedal. You can see the original mechanical bracket on the left.
Take a look at the previous photos and you can see the various adaptations.
Did you ever wish you had brakes in the front cockpit? It can be done! I happened to notice this wonderful modification on a Bitz restored airplane. What a great idea. I decided do the same thing on my airplane. You need two set of rear rudder pedals though.....
You just run a bar from the rear brake to the front brake. It works great !
Compliments to Bitz for coming up with a great idea.
Calipers and Brake Lines
Another variable I have seen is the routing of the brake lines from the master cylinder to the wheels. Since the Bucker landing gears have such a long stroke, the brake lines need to be very flexible.
To accommodate the long oleo travel, you will see a loop in the brake line at the wheel. When the oleo compresses on landing, the loop enlarges.
So, to go from the master cylinder to the caliper, you need a combination of flexible Aeroquip hose and hard lines in the gear legs fairing.
Here you can see the aluminum lines with some black anti-chaffe tubing.
So, to go from the master cylinder to the caliper, you need a combination of flexible Aeroquip hose and hard lines in the gear legs fairing.
Here you can see the aluminum lines with some black anti-chaffe tubing.
Some people like the practicality of the big loop. You can easily inspect the flexible line for leaks. It works well.
There is another way. I stole this idea from Jerry Wells.
The original mechanical brakes had a cable that looped in the gear leg fairing. When the oleo extended, the loop took up the slack. The cable ran inside a guide tube.
Why not do the same with the flexible line?
You can see the flexible hose makes a loop in between the original plywood cable guide fairings, goes through the guide tube and out the bottom. No exterior loop. As the oleo moves up and down, the cable at the bottom of the fairing stays straight.
The choice is yours. Loop internally or loop externally.
Caliper placement is also a source of debate. As you have noticed in the pictures, most people put the caliper on the lower rear side of the wheel. The placement works perfectly for the exterior and interior flexible lines. However, if you have a flat tire, the plane could sit on the caliper, or worse, land on the caliper. Woody Menear solved this issue by putting the caliper on the top and running the loop upside down and forward.
And of course you can use "Nyloflow" nylon tubing for perhaps the lightest, most flexible and lowest cost option. This installation uses 3/16" Nylaflow (Same as all Rutan canard aircraft) covered with black heat-shrink tubing for UV protection.
Again....your choice.
The last part of the brake equation is a big one - Axles.
The original axle is too small for the 600 x 6 wheel. I have heard of people sleeving the original axle, but most people just get new ones. I believe Bitz will sell you a set. You can make your own. I'm toying with the idea of making a few more extra sets just to have around. Either way, you have to address this when doing the hydraulic brake conversion.
I have also seen people use vintage Boedell-Adams wheels and brakes and Grove makes a nice light weight set. Also, Gilles Tatry may be able to tell you more about the RDO R66 Mark III wheels he installed on his Jungmann.
That's all for now. I tried to present all the brake options. I chose the design that works best for me. I hope you do the same.
I have also seen people use vintage Boedell-Adams wheels and brakes and Grove makes a nice light weight set. Also, Gilles Tatry may be able to tell you more about the RDO R66 Mark III wheels he installed on his Jungmann.
That's all for now. I tried to present all the brake options. I chose the design that works best for me. I hope you do the same.