Brakes, the continuing saga

[cgruby]

I've been so thrilled to actually have brakes on my airplane, I've sort of overlooked some of the idiosyncrasies that still prevail.

1. The angle of the brake pedal is such that anytime you are pushing rudder, you are applying brake at the same time.

2. The right brake is still somewhat less effective than the left making for unbalanced control during braking.

These seem minor, but on one occasion when applying a little brake to slow down, the plane veered sharply to the left, I was unable to stop it with the right brake due to it's ineffectiveness, my first ground loop ever in 63 years of flying.

I've ordered the new style brake pedals from KF, they should be here before long. That should allow me to use the rudder without applying brakes.

I still need to find why that right side is so less effective. I never was completely satisfied with the firmness of the pedal after bleeding. I need to bleed them again, with vigor!!

More later.

[Dusty]

Early kf brake geometry is not the best,to have brakes and full rudder at the same time is next to impossible.
I have my pedals set slightly forward so I don't end up riding the brakes or having to slip my feet up to brake.
With full rudder the brake moves forward
If the master cylinders are mounted to the floor instead of the rudder tubes
They would move back( as in rans aircraft)
I don't know how the later kf is set up but I will be changing mine at some stage after having a near identical experience last weekend .
I didn't ground loop,but due more braking on the left ended up on the left shoulder or the runway:eek:
I usually avoid blacktop but had no option.

[cgruby]

All my landings, to date, have been on blacktop. Those big tires are quite grabby and I have to be really careful. This little ground loop was at very slow speed, but nevertheless, uncontrollable. I whizzed right past a couple of Vassi lights, which could have made a mess had I run into them.

I think the problem with the right brake may still be a little trapped air in the system.

[Peteohms]

I had poor braking on the right side for a long time. On the way to Oshkosh a few years ago, my right brake failed while landing at the half way point from central Texas. Fortunately I didn't lose control. I decided I could live with one brake so I finished my round trip. Turned out to be the o ring on the brake cylinder on the wheel. New 25 cent o ring and problem solved.

[cgruby]

I had poor braking on the right side for a long time. On the way to Oshkosh a few years ago, my right brake failed...

That may be worth looking at. I have added a new cylinder to that wheel, but also have the old cylinder on there too. It might be worth the effort to re-O-ring both of the old cylinders, however, there are no leaks from either.

[cgruby]

I bled the right side with vigor!!!, with no noticeable benefit. I received my new brake pedals from Kit Fox, only to find they are backwards from mine. Mine are "C" type where the later ones are "E" type. Mine the open part of the "C" is to the left, the new one's are open to the right, plus the master cylinder mounting point is entirely different. I'm going to have to fabricate my own "E" type to get this to work. I sure spent a lot of money for some bent tubing.

Flying the airplane with mismatched brakes is really dangerous. You can just about guarantee a ground loop to the left.

The next plan is to measure the pressure on the right side to see if I have 450 psi. If I do, then I should look for something mechanical in the wheel.

Later,

[Dusty]

There has been some discussion on pedals in this or possibly another "similar" site. E pedals have been mentioned as being opposite?
If this is the case would kf swap them over,worth a shot!

[t j]

Just thinking out loud, did you receive pedals for the passenger side instead of pilot side?

[Slyfox]

what kind of lines do you have

[cgruby]

Just thinking out loud, did you receive pedals for the passenger side instead of pilot side?

I have a picture that one of the other builders posted of a later model under construction, that shows these type of pedals on the pilot's side. I can't see the passenger's side in the photo to see if they are different. I've already decided to modify my pedals to add the lower part of the "E". I'll send these back to KF and maybe they'll give me a credit.

[cgruby]

Just thinking out loud, did you receive pedals for the passenger side instead of pilot side?

As I mentioned in a reply to another post, the picture I have shows the open end of the "E" to the right on the pilot's side. Mine the open end is to the left. I can't see the passenger's side in the photo, so I can't comment on that. Also the mounting point of the master cylinder is quite different than mine.

[cgruby]

what kind of lines do you have

They are the typical Nylon line which MATCO and KF sell for that purpose. Interesting enough, I just measured the hydraulic pressure at the right wheel cylinder and got 400 psi. I was looking fro 450, but that's considerably better than which the old master cylinders.

[t j]

The rudder pedal torque tubes and brake master cylinder floor bracks on the model 4 are opposite as to pilot and passenger sides to what the earlier models have. It looks to me like Model 4 passenger side pedals would be needed on the pilot side of an earlier model.

Here's a model 4 photo I snagged off barnstormers. This one has C pedals but the E pedals install the same directions on the model 4.

[Slyfox]

They are the typical Nylon line which MATCO and KF sell for that purpose. Interesting enough, I just measured the hydraulic pressure at the right wheel cylinder and got 400 psi. I was looking fro 450, but that's considerably better than which the old master cylinders.


you got the clear lines, same as me. I had problems with mine years ago. could not get good braking from one side. I gave up, until I built my rv7. I used the same lines. to my surprise they had me put inserts at the end of the lines all of them. I thought what? you see to make the lines work you have to put inserts at the end, kind of hard to get them in there, but the reason, they have that compression thing on the outside that crimps the line for a seal. if there is no insert than the line crimps off the fluid to the cylinder. in my case I removed each connection for my brakes and found one end did not have this and was closing off the line. you can have pressure and all air out, but if it's closed off, no brakes. I fixed this by buying new inserts from vans and redoing my lines. than I got nice even brakes on my kitfox after that.

[cgruby]

Hi Gents,

It's been a couple of weeks since I posted my progress (or the lack of) on achieving a firm brake pedal and symmetrical braking power. Since the last post, I've done the following:

1. added a lower bale to my brake pedals to change them from "C" types to "E" types.

2. raised the pedals up and inch by cutting and splicing the risers and re-welding.

3. closed off the lines to the wheel cylinders by closing the park brake valve. When doing this, both brake pedals are firm, suggesting that there was no air in the master cylinders.

4. disconnected the supply line to the right wheel cylinder and connected a fluid catch bottle to it.

5. removed both wheel cylinders from their mounting plate and hung them up vertically with the bleed valve down and the catch bottle up, the interconnect line was left attached.

6. pumped fluid into the bleed valve until no air bubble could be seen entering the catch bottle.

7. remounted the cylinders back on the backing plate, pumped a little more fluid thru the cylinders until the supply port was free of air, and then reconnected the supply line.

8. opened the parking brake valve and continued to pump fluid up to the reservoir.

9. At the end of all this, I felt as though I had improved on the pedal firmness significantly. The next thing to do was to go taxi test.

10. The taxi test yielded brakes that were symmetrical, but still short of totally perfect, but nevertheless, adequate.

11. Takeoff and landings were completely normal, with no hint of loss of directional control (thanks to the "E" type pedals).

The airplane is much more manageable, but short of expectations, but I can live with it. The positive side is that I don't have to worry about nosing it over. I have exhausted all my knowledge and energy trying to solve this problem and unless I come up with some startling revelation, I plan to close this thread.

BTW, I discovered there is a special connector that allows you to connect to the bleed valve that stays put, I have never seen one in all my years working on aircraft. I have ordered one and a brake bleeder from ATS.

Cheers,

[cgruby]

The rudder pedal torque tubes and brake master cylinder floor bracks on the model 4 are opposite as to pilot and passenger sides to what the earlier models have. It looks to me like Model 4 passenger side pedals would be needed on the pilot side of an earlier model.

I think you are right. The master cylinders mounted differently, but substituting the passenger side for the pilot's side looks workable. I just copied the dimensions and modified mine.

[cgruby]

you got the clear lines, same as me. I had problems with mine years ago. could not get good braking from one side. I gave up, until I built my rv7. I used the same lines. to my surprise they had me put inserts at the end of the lines all of them...

I notice those things, but didn't pay a lot of attention to them. I just thought they were just different type of fittings. I will definitely look at those.

Thanks,

[Avidfox]

You might take a look at your pads. It sounds like the one side may be or have been saturated at one time or are from different makers.
Dave

[Slyfox]

I notice those things, but didn't pay a lot of attention to them. I just thought they were just different type of fittings. I will definitely look at those.

Thanks,
if you don't have those installed at the end of your lines you will crimp down the line when you tighten the nut. it crimps the outside compression ring and than closes the line. if you didn't install those you need to cut off the end and press the little insert in. the best way to do this is to take the whole line off. start the insert and push it against a hard surface and wiggle push it on while holding the line. I believe I took my heat gun and gave it some heat and mine went right on. a tough thing to do, but very important. you will also need to buy new compression rings.

[jiott]

I agree with Slyfox; those inserts are mandatory. Without them the compression ring just collapses the plastic tube without getting a good seal, so you have to tighten (collapse the tube) them much more than ordinary to get a good seal. You may have a firm pedal now, but poor brake response-sluggish to apply and release.

[Slyfox]

I agree with Slyfox; those inserts are mandatory. Without them the compression ring just collapses the plastic tube without getting a good seal.....

it will be like turning the faucet down and getting a little trickle of water. so no brakes is the result. have to put those insert in to keep things open and flowing.

[jrevens]

I had concern about the lack of inserts for the tubing with my Kitfox. I was told a couple of different times that the tubing (Nylaflow Type 3/16" T) & fittings supplied by Kitfox do not require the inserts. I hope that John or someone else from the factory can re-confirm that, as I will soon be plumbing my brakes.

[Slyfox]

I had concern about the lack of inserts for the tubing with my Kitfox. I was told a couple of different times that the tubing (Nylaflow Type 3/16" T) & fittings supplied by Kitfox do not require the inserts. I hope that John or someone else from the factory can re-confirm that, as I will soon be plumbing my brakes.

best way to know is to go ahead and do it. install the line and tighten it down. than remove It and look into the end, if it's crimped shut or close to it, guess what, you needed them. they are there to keep the hole from closing up. vans says you need them, so nylaflow hose is nylaflow hose. and my hose did close up without them. I installed the inserts and got braking afterward.:)

[jrevens]

best way to know is to go ahead and do it. install the line and tighten it down. than remove It and look into the end, if it's crimped shut or close to it, guess what, you needed them. they are there to keep the hole from closing up. vans says you need them, so nylaflow hose is nylaflow hose. and my hose did close up without them. I installed the inserts and got braking afterward.:)

I agree that using the inserts is probably the correct and safest way to go, but you may have some difficulty finding the correct ones for your particular tubing.
"...so nylaflow hose is nylaflow hose" is not exactly true. With Nylaflow tubing, you have types H, T, LM (both natural & black), & LP. Different wall thicknesses (& hence I.D.s), pressure & temperature ratings, UV resistance, etc. The "standard" Type T that came with my kit is the thinner wall version, and I would definitely recommend inserts if you're going to use it for brake lines, regardless of the fact that many have evidently had no problem with it leaking or coming apart at the fittings without them. It should also be protected from exposure to sunlight, as it hardens and becomes brittle with UV exposure. It's hard to beat the plastic for light weight and ease of installation, but there are probably better materials to use - especially at the wheel cylinder. The I.D. of that tubing I got is also large enough that it would be impossible for it to be squeezed shut with the Parker compression fittings I got from Kitfox. My main concern with not using inserts is the tubing "relaxing" with age and not maintaining a strong/leak-free connection.

[Slyfox]

to each there own. I do believe on these aircraft, vans aircraft also, that the nylon hose is all the same. argue all you want. I redid my lines after building my rv7 because of the inserts. the person here that is having troubles must take each connection off and look into the end of the line to see if it closed off from NOT having inserts. yes you could maybe get away without them, but if you tighten the line to much, guess what, that line will get closed off. so check your lines if you are have braking problems, most likely this is your problem.

[cgruby]

if you don't have those installed at the end of your lines you will crimp down the line when you tighten the nut. it crimps the outside compression ring and than closes the line. if you didn't install those you need to cut off the end and press the little insert in.....

Apparently I have two types of fittings, one has the brass compression ring that fits over the tube. Clearly this one needs the insert. But the Poly Flow fitting has the compression device integral to the nut and does not require a sleeve (according to AC Spruce).

I have a couple of joints that have the brass compression rings which I'll have to go back and examine.

[jrevens]

Apparently I have two types of fittings, one has the brass compression ring that fits over the tube. Clearly this one needs the insert. But the Poly Flow fitting has the compression device integral to the nut and does not require a sleeve (according to AC Spruce).

Chuck,

Some fittings have a separate compression sleeve, but the Poly-Flo fittings have the sleeve also. It's just connected to the nut. They work the very same way. With compression fittings like this, it's critical to tighten them correctly - there are published guidelines. You don't want to over-tighten or under-tighten them.

[jrevens]

to each there own. I do believe on these aircraft, vans aircraft also, that the nylon hose is all the same. argue all you want...

Nobody's trying to argue, Steve... just sharing information and trying to help others. The tubing used is not always the same. There is Nylaflow, Nylaseal, Parflex, etc., and all have been used as brake lines by some builders. There are sometimes some important differences between them for our purposes. I agree with you that inserts are a good idea. Maybe not necessary in all instances, but a good idea. I don't know what size O.D. your lines are, but if they are the smaller 1/8", or the 3/16" with a heavier wall (like Parflex), there might be a greater chance of crushing the tubing to the point that it closes off. Again, with the tubing and fittings supplied by Kitfox to me, it's pretty unlikely that you could have that happen... I just did a test with a small piece and over-tightened it to the max, and the compression just doesn't get anywhere close to closing off the tube. So there are some reasons that the differences in tubing are important - and there are differences.
When Rutan first specified the Nylaflow tubing for brake lines, his recommended technique, as I recall, was to insert a small piece of 1/8" brass tubing into the end as an insert. Many of the RV builders, and Van's themselves, have moved away from the plastic brake lines - at least to a certain extent. I used solid aluminum and Teflon-lined braided stainless on my T-18, and haven't had a single problem with it in 25 years. I repeat - this is all offered in the spirit of sharing knowledge and information, not to argue.

[Dave S]

All,

Jrevens is precisely correct....on the compression nuts with the captive ferrule, there is a prescribed way of tightening them.

I think where we might get separated from the instructions is this.

In the manual the Nylaflow/compression fitting instructions specific to the captive ferrule type nut is not in the assembly instructions where you would expect it. It is under "Compression Tube Fittings" in the Bulder Tips at the beginning of the manual before the assembly manual...goes on to say for the captive ferrule it is a "not to much" and "not too little' issue.....explains that a person should hand tighten, then wrench tighten JUST enough to seal and prevent the tube from backing out so you cannot pull it free. No more tightening than is necessary for the seal to hold; and, enough for the ferrule to bite the tube enough to hold...but no more. Also mentiones that hand tight plus one turn on the wrench works out about right. Nowhere in this tip section are inserts mentioned.OK, now going to the assembly manual covering running the brake lines. In this section there is no mention of the captive ferrule type compression nut; but, there is mention of putting a nut on the line, inserting a ferrule onto the line before attaching. Interesting part here is these instructions including inserting a ferrule over the tube separate and following placing the nut over the tube...which would not be the case if you had the captive ferrule type nut since that is a one piece deal. I don't see any mention of an insert in the assembly instructions, just the ferrule.

This is from my S7 manual.

I can see that the captive ferrule has an extended barrel which sticks out past the nut while a conventional compression fitting would not.....might explain differences people experience between using the two.

By the way.....for the tubing between the wheel cylinder and the gear leg...I used aircraft hydraulic hose (3000 psi) and AN fittings .....I know what kind of junk I have a tendency to drag my feet through..:eek:

Sincerely,

Dave S

KF 7 Trigear
912ULS WArp Drive

[Slyfox]

Steve...this is all offered in the spirit of sharing knowledge and information, not to argue.

ya I guess I went overboard. my apologies. I wanted to state that there might be a problem with the clear line.

with the problem of uneven braking, checking at least the end to make sure they didn't close off would be needed at this point. I myself like the idea of a clear line, inspection for air bubbles is easy to detect. my rv for instance, I fly pretty radical and I loose fluid out the res. on the brakes. I always look under the panel at my hoses to see if the fluid is getting low.

when bleading the brakes I can see where the air is, than I just remove the fitting close to the air and it will in most cases just exit where I removed the line on it's own. :)

[Slyfox]

also on this. I would not only look into the ends of the lines, but also stick a drill bit up the line. the area where the crush is located is the area of question. how big, don't know. maybe take the line off on the other side and stick a bit up there to get the size. it's important that both sides are the same, so measuring the good side and making sure you have the opening the same on the other. I personally have a drill bit set that goes .03 on drill bits from .040 to .250. I love this set.

that's why I love the inserts in my lines, I know that the opening is good throughout.

[HighWing]

I had concern about the lack of inserts for the tubing with my Kitfox. I was told a couple of different times that the tubing (Nylaflow Type 3/16" T) & fittings supplied by Kitfox do not require the inserts..

For the record, I had Nylaflow tubing with the Poly-Flow fittings on both of my Model IVs. In 900 hours on the original, I had no issues with the brakes. I would suspect the six or eight guys I regularly flew with would say the same thing. Then, I don't recall discussions on the original email lists and wonder if there are any Service Letters in the Kitfox archives. Over the years, Kitfox has been pretty up front on issues that have popped up. My new airplane has had some brake issues, but totally relating to locking brakes. I have concluded that it is a pedal design issue as the "old" plane was ca. 1993 whereas the "new" one is ca. 1992. The difference being the original E type pedals and the new on the C type which under my feet tend to be a brake always pressurized and overheating. I have since modified the pedals.

Regarding Nylaflow tubing. In both of the kits I built, I was supplied with the Poly Flow fittings along with the tubing. I am really curious where the "hardware store" (add the compression ring) fittings are coming from. I have used them on the fuel vent line and did use the inserts there as the tubing was much softer than Nylaflow. The Aircraft Spruce Catalog and website have been like a Bible to me. Do a search on Nylaflow on ACS and two items pop up - A link to the Nylaflow tubing and a link to the Poly-Flow fittings.

Finally, I was surprised that the Lancair IV I helped with came kitted with Nylaflow tubing for the brakes. This puppy has a 100 kn. approach speed and I was thinking heat. But so far so good there - 7 years.

[jrevens]

That's good to know, Lowell... gives me a little more confidence in the Nylaflow and lack of inserts (although I think I will still add inserts if I can get the correct size. I think Wicks may carry them. I sometimes think I'm kind of a belt AND suspenders type of guy when it comes to airplanes. I also think that the plastic has gotten a bad rap in certain circles, sometimes due to poor assembly technique and other factors.

Steve (Slyfox) - no apology necessary. I appreciate the give & take, and you sharing your experience.

Cgruby - I don't recall if you said what size your plastic lines are (1/8", 3/16", or 1/4" OD). They're not 1/4", are they?

[jiott]

After reading this thread, I got to thinking that Kitfox factory really deserves kudos for this sort of thing. When I got ready to install my brake kit, I just opened the box and everything was there-nice brass compression fittings, plastic tubing, and properly sized inserts for the tubing. It all went together without a hitch in the proper way. I didn't have to know about inserts or no inserts or try to determine proper type and size, or try to figure out where to get them. I would be the first to agree that figuring out this stuff for yourself is a good thing and a valuable part of the building/learning experience.

After participating in this forum for over 4 years now I continually see many guys beat themselves to death trying to figure out the best way to do something when a simple call to the Kitfox factory usually gets you the right stuff that is going to work just fine. I have had them gladly send me onesy twosey items. My suggestion would be to start with the factory first and then if you want to learn more and maybe improve the item to a somewhat higher quality, fine. But if you start with the factory recommended items you won't go wrong and end up later spending many hours troubleshooting a problem that you didn't even know you had.

I fully realize that some folks may have added or modified things to such an extent that the factory can't help them so they are on their own, and forums like this can be a great help. Believe me I am not trying to put anyone down, I actually admire those adventurous ones who figure it all out themselves. I am just trying to say that we have a great kit, well engineered and documented, supported by good people that makes life easy for most of us that are willing to go by the book. We also need to support them by purchasing from them whenever possible so their company stays around for many years.

[jrevens]

I for one agree with you Jim, 100%. The particular issue of inserts or no inserts in plastic brake lines has been confusing though, and I've asked someone from the factory if they're needed. The answer - no. That will be good enough for many (or most), but I find it interesting that you say you received inserts. Some other very smart people disagree with the answer I got. So there you have it. It may take a little more time, but sometimes it's smart to research questions that crop up... I'm not saying it's the case here, but people sometimes make mistakes, and sometimes there is a better, & more importantly safer way to skin a cat.

[Slyfox]

I have to agree, John and Deb is a great team. When I got my new engine back in 2009 I got everything from them firewall forward. It was a nice feeling knowing that there was someone that new just what I needed and everything went together nice.

[Slyfox]

That's good to know, Lowell... gives me a little more confidence in the Nylaflow and lack of inserts (although I think I will still add inserts if I can get the correct size. I think Wicks may carry them?....

Steve (Slyfox) - no apology necessary. I appreciate the give & take, and you sharing your experience.



Thanks John, I never know how I'm taken, this is print after all. I know what happened on my plastic lines, and to add I think mine went south over a period of time. I think I had a small leak, I tightened the line, than gradually the brake got less, I kept tightening the line cus the leak came back. finally I said this is bad. than I got to the brakes on the rv and said, hmmmm inserts. I took my line off and sure nuf, no inserts and also closed off, or close to it.

anyway have a nice day.:)

[Peteohms]

On the plastic brake line issue, how often should you replace the lines?

[HighWing]

... I know what happened on my plastic lines, and to add I think mine went south over a period of time......

In my experience - recent and previous IVs, I think if you are having leaking, it is because of riding the brakes and overheating the brake assembly at the wheel. As mentioned previously, I never had any issues at all on my first Model IV with the E pedals. On the other hand, I have had no end of problems with the new IV and I attribute it to the C pedals with my foot holding constant low braking pressure. Long taxi's would result in extreme heat at the calipers and deformed Nylaflow and leaks. right now, I have a very small leak that I am trying to source, but it is likely a seal at the caliper. It appears as a drop or smear at the low point which is the bleed fitting - no moisture at the brake line fitting.

[Slyfox]

as mentioned, I had a leak at a fitting, to much tightening over time collapsed the line at the compression.

anyway, I have the matco set up. I had brake problems also because of the hardware on the brakes itself, this resulted in severe burn up of the brake pads. what I did was buy all the little hardware parts and polished up everything and reinstalled with new pads and NO lube. it's been over 6 years and over 1000 hrs and am still on the same pads. I'm a guy that hardly uses his brakes. the only time I use brakes is if I want to land real short and do a 180 back to the beginning of the runway. most the time I don't use brakes at all when landing.:p

[Slyfox]

one thing for certain, if you end up putting the 1000 dollars into this engine like Dave said, you will get more than that guy that's doing just the rubber replacement. :D

[cgruby]

Cgruby - I don't recall if you said what size your plastic lines are (1/8", 3/16", or 1/4" OD). They're not 1/4", are they?

My lines are 1/4" Nylon from the reservoir to both master cylinders, and 3/16" from the master cylinders to the wheel cylinders. Some of the original lines have the compression ring, but no inserts. My Ny-Lock fittings have no inserts.