Replies to This Discussion

Permalink Reply by Chumphol Sirinavin on February 21, 2011 at 6:53am

Hi Bob,

 

My first 701 uses cable brake. Another uses hydraulic brake, with the common plastic/nylon (don't really know which) hydraulic line used on motorcycles and found in hardware store. It's not the hydraulic brake fluid I use, but automatic transmission fluid.

 

Champ

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Permalink Reply by Chris Aysen on February 21, 2011 at 7:28am

Bob - You might check with Aircraft Spruce on "Nylaflow Tubing" (05-00115) and for fittings use "Poly-Flo" fittings all through ACS. My 701 is set-up with these components and I'm happy with the results. I did however put a fitting on the fuselage at the main gear that allows me to change just the exposed tubing in case the tubing is damaged. Hope this helps.

Chris

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Permalink Reply by Mike Ice on February 21, 2011 at 3:12pm

Hi Bob,

On my first airplane I used brake lines made by this company,http://www.bonacoinc.com/bonaco_brake_cat.pdf,

If you call them and tell them it is for aviation they will line you out with all AN fittings and build you a pair of brake lines that will look great.

Mike  

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Permalink Reply by mark woodring on December 10, 2021 at 6:34am

WARNING  DO NOT USE PLASTIC LINES. I have yet to lift off the runway with my 701 on zenair amphibious floats, but during construction one of the plastic gear hydraulic lines burst.  thought it was a fluke, but then trailering the plane to the airport, a second line burst...  taxiing around the ramp to break in the brakes, the left brake line overheated at the caliper and burst. missed the private jet on the ramp by about 10ft...

I am converting all lines to aeroquip 303 and/or stainless tube (I am in salt water with the floats)

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Permalink Reply by Jim and Amelia Isaacs on December 11, 2021 at 6:08pm

 Mark,

Not sure what happened in your circumstance but the Zenith finishing kit includes flexible “plastic” tubing, and that is what I installed on my 701 over two years and 100 flight hours ago.  After almost 300 landings, the vast majority into my confined area short home field requiring demanding braking performance, I’ve had no problems to date. 

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Permalink Reply by mark woodring on December 11, 2021 at 9:18pm

I assume you have the 701 on wheels with steerable nosewheel.

mine is on zenair amphib floats. the same? plastic lines came with the float kit. as I went straight to floats, I never had the main wheels and nosewheel that comes with the 701 kit.  I have blown out 3 lines. first was on the first pressurization of the gear hydraulics when building. second gear line burst due to the trailer ride to the airport... (afraid a hard landing night cause it again).

the float main wheels and matco brakes are a bit smaller than the wheeled 701's. there is a bit extra weight, and all steering at slower speeds (rudder less effective then) is done by brakes alone. they may get a bit hotter in use and having had to ride the brake a little while crosswind taxiing in other non-steerable nosewheel aircraft (grumman cheetah, for one) functional brakes are essential to remain on the runway. 

I am adventurous, but safety conscious. in my opinion the plastic lines are an accident waiting to happen. having nosewheel steering and only using them to stop may not put them in the critical category.

you can check out the video on my youtube channel under my name. I wont use the plane with the plastic lines.

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Permalink Reply by Jim and Amelia Isaacs on December 12, 2021 at 8:08am

Yes sir, my 701 is the terra firma configuration.  I wonder why your lines failed given their proven history but I understand completely moving to an all steel solution. I was skeptical of the plastic tubing at first too until I spoke with Roger about it and he told me he’d been using them on his 701 for years. Maybe something about the float configuration.  Take care and fly safe. 

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Permalink Reply by John Austin on December 14, 2021 at 8:23am

I was skeptical of the plastic tubing at first too until I spoke with Roger about it and he told me he’d been using them on his 701 for years

I have a STOL 750 with the plastic (nylon?) lines as supplied by Zenith.  I was at a Jabiru engine maintenance course and the guy sitting next to me was a Boeing engineer.  Somehow we got around to talking about the brake lines and he told me to not worry about their strength - he said they used the exact same tubing in hydraulic test rigs at Boeing and the tubing could withstand several multiples of the maximum pressure that the Matco brake cylinders could develop!

I've used these lines for about 10 years with zero issues.  Normally, I'm a big fan of SS braided lines and admit they are the optimal solution except for weight and cost, and they are near-indestructible and are the best choice for external lines subject to damage as in a plane operating on unimproved terrrain with bushes, rocks, etc.  However, suitably protected nylon lines are light and cheap and work great for those of us who primarily operate on improved strips.

John

N750A

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Permalink Reply by mark woodring on December 14, 2021 at 8:30am

there must be a significant difference between the land and float configuration. a gear line burst 2 inches from a tee joint, another burst 3 inches from the manual pump fitting, the brake burst just above the caliper fitting, showing signs of heat deformation. 

my stainless lines and aeroquip 303 hose should show up in a day or two. I will post vids on my youtube channel of the conversion.

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Permalink Reply by Mike York on December 15, 2021 at 10:00am

Not all plastic tubing has the same burst pressure.  The stuff from Zenith, Vans Aircraft (mine anyway) is over 1000 psig.  The stuff we use at work for pneumatic controls is less than 200 psig.  I had the zenith supplied stuff get brittle and break after sitting in the sun for 18 years.  How many people let it sit in the sun?  Most aircraft are hangared.  Latest build the tubing was painted when the fuselage was painted.  This should last nearly the life of the plane.

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