Brake lines

[Luke68]

I was reading the latest bear tracks about the brake system hardware and it got me thinking, why couldn't I use flexible brake lines like in my friends RV? Less fittings to leak, lighter and possibly cheaper.
I looked it up in Spruce and for the NSR tubing ( rated for 2500 psi) and all the fittings would cost around $65. I did some checking and the 1/4" tubing will just slide through a 3/8 aluminum line so my plan is to use that as sort of a conduit through the gear leg so I could also eliminate the need for inspection covers.
Looking for some opinions.
Thanks

[whee]

There's a conversation on here somewhere about brake line types. Based on that thread I ordered premade Aeroquip lines from Summit Racing and am very happy with them. Hope I'm just as happy when I actually start using them.

[Luke68]

Yep should have done a search first, thanks

[Bcone1381]

After spending hours researching this topic on line (research includes vansairforce.com) I came back around to what the recent Breatracks article outlined except for making my own flexible hoses using Areoquip 303-4 on the Pressure side of the Master Cylinders. Whee, I am interested in hearing the results of your research and details of your choice of Hoses, and Summit Racing's product offerings.

When I draw a conclusion, I keep an open mind and an eye out for improvement ideas, because I know they exist. So, I am interested in Whee's Choice. He researches things in depth, and draws good conclusions.

Why I rejected the Racing Products was because the Aeroquip 303 hose is an approved industry standard, I can make them myself in the shop with inexpensive tooling, and doing so saved enough money to provide a large enough reward over having an unapproved, but maybe superior stainless branded PTFE hose. I choose to use Rigid Line where the Article suggest because of its weight, cost, durability, and I think ease of fabrication. Most Flex hose I saw had a 5 year shelf life.

I also was aware that our AN fittings are Aluminum, and I have concerns about dis-similar metal corrosion with fittings that are non approved and non-aluminum. But, the Areoquip fitting are not aluminum, so I am inconsistent. I decided that if they are an FAA approved industry standard, then I will turn my head and pretend it will be ok.

As for the light weight plastic hose that Vans uses, I may use a plastic hose product with brass compression fittings for the flexible line that goes from the firewall to the Master Cylinders if I cannot use a reservoir at the Master Cylinder. I have concern over the space available between the rudder pedals and firewall.

I also think the right plastic line has merit on the pressure side, but will require more attention to maintaining, and periodic hose replacement. Lots of Van's Builders have reported poor service results form using the plastic. Consider using fittings that are not plastic.

Brooks Cone
Patrol #303
Shop comes first
Kit Comes next
Meanwhile I research and make plans.

[S Lathrop]

When I install the brake system on my BearHawk, it will be my first experience with aircraft brake systems. But I do have many decades of doing brake systems for road racing brake systems.

When I started installing brake systems, I did it very close to what is recommended for the BearHawk. Over the years, I changed to using Aeroquip lines from the master cylinders to the calipers with the fewest number of fittings possible. Each fitting is a potential problem and fewer is better.

I have cars that have been raced since I built them 25 years ago with no brake line issues except for the occasional crash. The few repairs that have been made are frequently nothing more than adding a union in place of a damaged spot in the line.

I plan to use Aeroquip throughout the brake system on my project. The one thing I am going to do is cover the lines with heat shrink tubing to add an extra degree of protection for both the lines and the parts the lines are close too. Having the lines made by a shop like Summit Racing that can install crimped fittings, is much less expensive that buying the reusable fillings. I frequently use a combination of both crimped and reusable fittings.

AN type fittings are available in -3 and -4 sizes in both steel and aluminum.

[whee]

Yep should have done a search first, thanks

No problem, if it hadn't been so late I would have look the thread up for you but I think I was half asleep when I responded. I never hurts to rehash something like brake systems.

After spending hours researching this topic on line (research includes vansairforce.com) I came back around to what the recent Breatracks article outlined except for making my own flexible hoses using Areoquip 303-4 on the Pressure side of the Master Cylinders. Whee, I am interested in hearing the results of your research and details of your choice of Hoses, and Summit Racing's product offerings.

When I draw a conclusion, I keep an open mind and an eye out for improvement ideas, because I know they exist. So, I am interested in Whee's Choice. He researches things in depth, and draws good conclusions.

Why I rejected the Racing Products was because the Aeroquip 303 hose is an approved industry standard, I can make them myself in the shop with inexpensive tooling, and doing so saved enough money to provide a large enough reward over having an unapproved, but maybe superior stainless branded PTFE hose. I choose to use Rigid Line where the Article suggest because of its weight, cost, durability, and I think ease of fabrication. Most Flex hose I saw had a 5 year shelf life.

I also was aware that our AN fittings are Aluminum, and I have concerns about dis-similar metal corrosion with fittings that are non approved and non-aluminum. But, the Areoquip fitting are not aluminum, so I am inconsistent. I decided that if they are an FAA approved industry standard, then I will turn my head and pretend it will be ok.

As for the light weight plastic hose that Vans uses, I may use a plastic hose product with brass compression fittings for the flexible line that goes from the firewall to the Master Cylinders if I cannot use a reservoir at the Master Cylinder. I have concern over the space available between the rudder pedals and firewall.

I also think the right plastic line has merit on the pressure side, but will require more attention to maintaining, and periodic hose replacement. Lots of Van's Builders have reported poor service results form using the plastic. Consider using fittings that are not plastic.

Thanks Brooks, though I sure that there are many that disagree with you about my decision making.

Anyways, when was looking into brake lines I had talked to people about about the small plastic lines, standard aluminum lines and Aeroquip lines. I never could get comfortable with the plastic lines though I know some here have used them with good success. I've been told they need to be replaced every 5 years or so because they do age and can break. I intended to go with standard aluminum lines until two people I trust gave me a strong recommendation for Aeroquip lines. All the reviews I could find about the premade Summit Racing lines were really good, S Lathrop as an example, and I figured professionally made racing lines would be better than aircraft lines that I made myself. That may or may not be true but the lines from Summit are great quality. I know of a couple other airplanes that have used the premade lines from Summit and the owners are still happy with them.

I went with -3 hoses; they have steel fittings and are tested to 4000psi. Lots of different sizes available from Summit: https://www.summitracing.com/search/...roquip%20brake

I had planned to go with a firewall reservoir but when looking on Aircraft Spruce for the a reservoir I came across their master cylinder mounted reservoirs. They are fairly inexpensive so I tried them and I think they will be great.

[Battson]

Having looked around online extensively before I made my choice, most Bearhawk builders (judging by the records available on build logs, photos, etc.) seem to use a mix of aluminium hard line, Aeroquip hose, and plastic soft line all together. That is what I did.

Using a flexible Aeroquip 303 or similar is the most expensive but is less likely to fail - but it does fail sometimes, I cite a recent local crash. The plastic line is the lowest cost solution, but requires replacement after a time, albeit it very infrequently - but it will fail eventually if not replaced. The hard line is obviously good for the life of the aircraft and is cost-effective, but cannot be used around the gear leg interface or pedals. Some don't like hard line at the caliper, although it is commonly used there with no issues yet AFAIK.

I used hard line and soft line throughout the fuse, aeroquip 303 at the gear leg to fuselage interface, and hard line in the legs. Provided you use good quality brass fittings to interface with the plastic,, it works really nicely (touch wood). Obviously it has a limited life, and you will need to spend an hour or two replacing it every 10 years or so (less if it sees any regular direct UV light). I used hard line at the calipers with a protective pastic sheath wrapped around the aluminium. Initially, I had my doubts about using aluminium near the calipers, but now I can tell there's not enough movement there to cause the aluminium to work harden. We land in the roughest of stuff, and those lines are not seeing any undue wear.

Using Aeroqip line everywhere is the Rolls Royce solution. Using plastic line everwhere is the normal LSA solution. But personally, I would not put plastic line anywhere you can't easily replace it.

[Luke68]

My RV friend also used aluminum at the calipers but he made a loop to take up any movement from the calipers, did you do the same or just run it straight out?

[Battson]

I did something similar - a little S bend.

[JimParker256]

My A&P/IA friend is constantly showing me examples of "engineering decisions that complicate maintenance"... Look at any Mooney for prime examples (you remove something like 100 screws to get full access to the engine), but there are dozens of other examples on every plane ever built. He's shown me a couple of cases where they had to almost completely disassemble structural elements to gain access to non-structural items like servos. Absolutely crazy!

So, I made a promise to myself that I would build as light as possible, consistent with easy maintenance. If it comes down to adding weight or "complexity" during the build process to make maintenance afterward easier, ease of maintenance wins every time.

To me, brake reservoirs mounted directly on the master cylinders fall into the "increased complexity / difficulty of maintenance" down the road. Trying to reach into the cockpit from outside, or contort myself to get under there to check the level and/or refill a brake reservoir is pretty challenging for me today, at age 60. How much harder will it be when I'm 70? Will I really do the "contortion" routine on every pre-flight to check those fluid levels? No? Didn't think so... So no cylinder-mounted reservoirs for me - I'm putting mine on the engine side of the firewall, where I can reach it easily when the cowl is open, and check it on every pre-flight. Just my 3⍧ worth (inflation).

As for plastic versus aluminum versus Aeroquip-type lines, I'm inclined against using plastic, just because I know it will be a pain to have to replace them every 5 years, and they do become brittle after some time passes. I like the simplicity of the Bob-style aluminum lines, but worry about the flexing they will do at the rudder pedals and where they exit the fuselage to the landing gear legs. At least those two sections will be flexible braided Aeroquip-style, and If I'm doing that much, why not all of it? I guess cost will be my guideline on that decision...

PS - thanks for the link to Summit Racing's page. Now I'm looking at their "standard lengths" to see if I can design my layout to take advantage of using their "standards" - which cost less than "custom" work... Lots to think about!

[Battson]

Trying to reach into the cockpit from outside, or contort myself to get under there to check the level and/or refill a brake reservoir is pretty challenging for me today, at age 60. How much harder will it be when I'm 70?

I am 32 and getting under the panel to the pedals is a pain in my, well, in everthing!! It's just the worst place in the whole plane to access.
I think only children would be comfortable working in those cramped spaces.

When I change my plastic lines, I will drop out the tunnel (5 minute job) and then have full access from underneath, while sitting on a short-legged stool.

If you are installing a parking brake (personally I think every real aeroplane should have one for safety's sake) then you have a handy termination point for the flexible hose from the pedals. You can run aluminium line from there to the bulkhead under the floor, flexible to the top of the leg, and then aluminium hard line down the leg.

[Battson]

Luke68
Here is the S bend:

[JimParker256]

Battson, please tell me you didn't cut the fabric just to take this picture? What were you actually doing here?

[Battson]

Modifying the gear legs to fit my 31" bushwheels. See the thread in the 4-place Quickbuild section for the full set of photos.

https://bearhawkforums.com/forum/bearhawk-4-place-quickbuild/24277-landing-gear-fairings-modified-for-large-tires-photos

[Luke68]

Thanks, I like the looks of that

[Mark Goldberg]

I have always set up my planes the same - and of course think this is the best way. Plastic lines from the fluid reservoir on the firewall to the master cylinders (no pressure), then the Aeroquip made up lines from the master cyls to the fuselage/gear leg intersection, then hard aluminum lines down to the brake caliper. Has worked well for me all these years. I have never had to replace anything. N303AP has over 1,100 hours.

I have personally seen plastic/nylon lines fail twice (once on Patrol & once on an RV) when used in the high pressure areas. Theoretically they should handle the pressure fine. But I have seen them fail twice. Mark

[nichzimmerman]

If you are installing a parking brake (personally I think every real aeroplane should have one for safety's sake)

Not intending to steer the conversation away from brakes lines, but I have been wrestling with this decision for a while. Can you elaborate Jon? I've owned 3 airplanes without parking breaks and never missed them, but I also don't have the bush experience that you have, and that's how I hope to use my 4-place. I've only considered parking breaks something that holds the airplane still from the time you get out until you slip the chocks in. Obviously they increase cost, weight complexity. What am I missing?

[whee]

Using Aeroqip line everywhere is the Rolls Royce solution.

Whoa, I have something fancy on my plane! I never thought that would happen.

[jim.mclaughlin924]

I would have to agree with Mark, I used plastic on my first 2 homebuilts but changed after a messy, inconvenient failure. I use 3/16 alum and -3 Earl's SS braided teflon. The aluminum can be coiled at the caliper to allow movement. The earl's hose is light and fittings are reusable and compatible with AN tube fittings.

[Flygirl1]

Aaw Jim ya just made me cry. This is the 4th time that's happened since we started this adventure. I expect 1 more time after first flight--tears of joy!!! ( I miss that bird! When the time comes and if I have won the lottery, will ya sell her back to me?? ). D.

[Flygirl1]

P. S. :
But I'm happy that your happy. :-)

[jim.mclaughlin924]

Sure, when the time comes, you have the first shot. Probably spring of 2018.

[JimParker256]

Comment moved to the "Parking Brake" thread for better continuity of discussion.