January 27, 2020

Running Brake Lines

I temporarily assembled the throttle section so that I could place it on the center console to help with determining length of tubing needed. Putting together the parking brake valve was a bit of a pain – for some reason, the kit-provided park valve is BPST threaded, whereas the fittings are NPT-threaded. I’m not a plumbing expert, but the internet tells me these two are not compatible, which it what I found empirically as well. I had to really crank down hard to get these to thread together, which caused the threads on the fittings to shave off a bit, and over-torqued one of the valve fittings in the process. The valve is junk now and will have to be replaced. It looks like the valve is made by Alpha Fittings, so I’ll see if I can find a replacement.

While the throttle assembly was in place, I realized I need to change out some fittings – the master brake valve physically moves as you pull the handle, so I need to use a flexible line between it and the parking brake ball valve. I’ll have to remove the AN3 flare fittings and swap them for the push-on fittings included with the kit, and use a short length of flexible tubing.

With parts in place I started routing the 3/16″ OD Versatube. I decided to route this line through the wing spar rather than over it. To ensure it won’t interfere with the rudder cables, I created a bracket to sit atop the center tunnel z-sections near the floor. There’s some room on this bracket to add another clamp that will be used for wires that run out to the joysticks and autopilot servo.

Brake line up to the parking brake valve. Also shown is the bracket that sits atop the z-sections, for attaching a hose clamp.
Close-up view of the bracket
Routing of the brake line through the wing spar carry-thru. I added a small jog to the tube to ensure it clears the horn on the elevator torque tube; after the jog, the tube runs beneath the sheathed rudder cable.

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