Thorp Air Command - T18.net

I could use some pictures of wheel brake caliper installations. I had to replace a brake line for a crack just behind the flare. The aluminum line was connected directly to the caliper (a moving part that should be free to move!) instead of connected with hose. My attempted fixes with what I have on hand are too big to fit under the wheel pants so I thought I would ask before spending $$$ on fittings and hose to experiment with.

Thanks

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I went with SS braided AN3 , PTFE lined (Made in the USA) brake line from JEGS . PN 555-104891 . Get the appropriate end fittings (same place you get the hose) and make (1) line from the MC to the caliper . Attach the hose with brake fittings to AN fittings on the MC and caliper . Been on the AC since 2010 with no problems . BOOYA !

RB

How did you secure the hose from chafing the the gear leg and/or inside of the fairing? I don't think my gear leg fairing would be considered removable because it won't slide over the axle mount (I had a gear extension off yesterday to look at the options). Even the cracked line I removed revealed a bad chafing problem with a hard line routed inside the fairing. It just happened to crack at the flare before it chafed through and created harder to identify problems. I foresee a similar or worse tendency with a hose unsupported for ~2 feet in close quarters.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

I put a couple of rubber hose pieces on the tubing before flaring.

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Bob Highley
N711SH
SN 835
KLAL

Secured the hose with (2) Adel clamps around the gear leg . I think (4) total ? Do what Bob said . Sounds like your gear leg fairing is riveted on the trailing edge ? When I did mine I considered future maint/repairs so I used 4-40 screws and nut plates so I can "split" the leg fairing and remove it . I would drill out the rivets , make the new line , install it correctly to the gear leg with Adel clamps and route it accordingly to the caliper with rubber chaff tubing like Bob suggested and either re rivet or use screws like I did . BADA BING , BADA BOOM ! BRAKES ARE ONLY GOOD WHEN YOU HAVE TO USE THEM !

RB

Hi Jeff,

I ran 1/4" aluminum tubing from the bulkhead fittings on the firewall, down the front of the gear legs to approximately a foot above the caliper. From there I used an AN4 to AN3 flare union to connect short pieces of AN3 teflon-lined s.s. hose into the calipers. Everything is carefully supported off the surface of the gear legs with custom built clamps & /or self-fusing rubber tape. If I can find pictures I'll post them. I highly recommend that you remove the leg fairings & make them removable for the future.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

My aircraft has 3/16" stainless line from the firewall bulkhead fitting to the AN fitting on the caliper, the hard line is clamped to the gear leg just below the bottom of the fuselage this allows the line to move with the caliper. This is how it was when I purchased the airplane and seems to be holding up just fine. I did redo my gear leg fairings and installed a hidden hinge down the trailing edge, to remove just pull the hinge pin.

Here's how the line is routed to the caliper, the hose is to prevent chafing where the line goes through the gear fairing.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Looks like I will be splitting the landing gear fairings.

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Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

You will be happy that you did .

RB

Jeff,

This is the only picture that I found quickly... it shows the transition from the aluminum tubing to the flexible S.S. hose with the little clamp I made. The flex goes down similar to Bruce's picture, but follows the structure a little tighter/closer. It then attaches to a 90 deg. fitting on the caliper assembly.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Hey fellas, here's another example for brake line.

Mine is 3/16 SS with service loop on each end for flexing. It also has rubber lined standoffs to keep it from touching anything along the way. I look at calipers and exposed lines for freedom each time when I check brakes for preflight. Ya gotta know the A-frame gear is secured quite well at the top, but the two lower bushings at fuselage allow some freedom, right where R & L brake lines typically emerge. That's an important place to have a loop and some flexibility. Mine don't really grip the leg, they're free to slide through the Adel clamps. The other critical point is obviously where the caliper floats on the brake disc. You'll see I only have one real tie-down, which occurs halfway down the leg. Rubber sleeves protect the line from the fairing, but there's lots of freedom as indicated before making end attachments. Fairings have to be removable for occasional inspection so the trailing edges are held by screws. I'm confident that any sign of wear will show on the fairings first since they're just thin aluminum sheet while tubing is steel. It's a matter of routine inspection that we all do. Steel is also less prone to fatigue and better for high temp. That's something to consider: my brakes got pretty hot as I was still on the learning curve with my plane.

In the top of the photo you may notice two fittings into the firewall for cabin and carb heat control cables. They're really automotive 'choke' cables, not fluid connections. I made a pair of crossed cuts into end of the AN832 bulkhead fittings so the nut and sleeve clamps down on the flexible control cable. Kind of an inexpensive way to make a pass through on the firewall.

My two cents,
Les Krumel

Les,
I can't wait for you to show her off at Sedona
Cubes

Thanks Jim. There are plenty of cool thorps to show off; most of them no doubt. I'm lookin forward to see them all too.

Les.

Very nice, Les! I really like your idea to use the bulkhead fittings for the control cable penetrations. Absolutely right about needing to accommodate movement at the bottom of the firewall area. I didn't have to do a "loop", as mine goes over a little more towards the center before penetrating, lining up where I wanted it with my master cylinder(s). Even as stiff as they are, the gear legs also do flex and you have to keep that in mind also (not directing that at you of course, but just thinking to myself). Watch your brake line where they go "loosely" through the Adel clamps. I've seen loose Adel clamps really eat into 4130 tubing when a little dirt gets embedded in the surface of the rubber. My aluminum lines are securely attached to the gear leg at the union where the S.S./Teflon hose connects shown in the picture. Otherwise, they ride the leg with rubber & duct tape... no problems in 26 years. Another nice possible advantage to using hose at that point is that you can remove the brake cylinder assemblies for cleaning or lining replacement easily without disconnecting hydraulic lines or having to bend any tubing.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Good points! I'll keep an eye on it. Les