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Horrible brake noise with new brakes/lines!

WingnutWick

Well Known Member
Hello!

So following my girlfriend's brake fire on her 6A I replaced the tire, tube, pads, and put on a braided nylon line instead of the previous rigid line. I cleaned the brake assembly as well and replaced the O-ring. The rotor was new just prior to the fire so I kept it. It had darkened from the fire which I though would clean off after a few uses of the brakes. I also used the opportunity to swap the bleeder valve from the top to the bottom.

After the repair all seemed normal vice a small pulsing in the right brake which I attributed to warping of the disk from the fire. Then after a couple flights a groaning sound began occurring during brake application which got progressively and rapidly worse.

I decided to replace the rotor altogether. I did this and initial taxi test seemed to solve the problem. The next time we went to fly, the noise was there with brake application and again, again getting progressively worse. I looked at the pads and there was some darkening that I figured was residue from the old, burned rotor. So then I replaced the pads today with new ones thinking that they had been contaminated by the old rotor.

Figuring I had the problem licked, my initial first brake attempts had no sound, then to my dismay, about 5 minuted into taxi test it came back again! :(
Now I am lost. I've re-done brakes a bunch of times on RV's with never an issue. I'm guessing the reason the sound doesn't start right off the bat after replacing thee items is due to the fact the pads were still new and not really gripping yet. But I still can't figure out what the heck is causing this horrible sound. The left has the old rigid brake line, the right brake (the repaired one making the sound) has the new flexible braided one.

My suspicions at the moment:
1. Due to event small amount of potential residue which remains from the original rotor? - Seems unlikely.
2. Due to swapping out the valve to the bottom?
3. Due to the new braided line somehow?
4. Some warping or compromise of the entire brake assembly due to the fire?

Here is a video so you can hear the sound which reverberates through the entire plane is quite unbearable. And photos of both brakes. As always, your help and insight is priceless!

VIDEO: https://youtu.be/lZGOIEUarts
IMG-4437-copy.jpg

IMG-4438-copy.jpg

IMG-4439.jpg
 
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Low frequency

Sounds like a low frequency vibration. Is the recording with the wheel pant on? If so the low frequency maybe amplified by the wheel pant. Also the gear fearing maybe channeling the noise up through the fuselage. Maybe the fire effected the wheel pant bracket material properties and is now resonating with any break/rotor interactions.

Please post a solution when resolved. Best of luck.
 
If it's any consolation, my 6A right brake has made that noise from day one, and it's persisted through brake pad replacement and brake bleeding. 21 years and 970 hours later, still there. Mine is not as persistent, only present when nearly stopped, but you can hear it from quite a distance.

I, too, would like to know how to eliminate it, but consider it a "cosmetic" rather than functional issue. IOW, as embarrassing as it is on the tarmac, I've learned to shrug it off and live with it.
 
OK, I may be showing my RV ignorance here (still building), but why would you put the bleeder on the bottom? Are you just cracking the lines at the to bleed now vs using the bleed screw? You can't bleed it from the screw on the bottom unless there is some trick I don't know or haven't learned/read about yet. Could it be the air in the caliper causing some cavitation/vibration.

I saw this firsthand on a car once when someone installed calipers on a 911 upside down (Left caliper on right side of car and ice versa). For the life of them couldn't figure out why they couldn't get all the air out of the brakes after numerous attempts to bleed. Then one of us noticed what what going on and pointed out his mistake and that air likes to go up in the calipers. Quick swap and everything worked out great.
 
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I recently overhauled my brakes and upgraded the lines to SS braided teflon hose, like yours. After the brake work, I also experienced brake chatter and chased my tail for quite some time trying to solve the issue. Finally, out of desperation, I changed the brake lines back to aluminum line and the chatter disappeared. Don’t ask me why.....

Dan, most RV guys bleed brakes by pushing fluid from the calipers up to the master cylinders, hence the bleeder installed on the bottom.

Ron B
 
If you search the Matroinics RV-list, you will find around 20-years ago, people that tried to use hose had brake noise issues. If the rigid aluminum lines was not perfect aligned, it would also create the same noise you posted to YouTube just like most people that attempted to use hose had.

When you pressurize the brake line, the caliper moves to an angle that makes noise.

The bleeder is suppose to be on the bottom. This allows a pressure pot to be used to force brake fluid up to the master cylinder reservoir. This should then give you a brake system with no air in the lines.
 
Flex line do work without noise.

Flex lines for 9 yrs and counting. No noise.
 
I have flex lines and no noise. these are special lines using -3 hose with -4 fittings. there is some thought that -4 flex lines are too flexible and cause a hydraulic resonance. smaller diameter flex lines are stiffer diametrically. what size is your flex line?
 
Fly it for a while

If you search the archives here you will see a lot of suggestions on brake noise. I have flex lines. I grind an angle on the front edge of the pads and also us an automotive type barrier (Autozone) on the back of the pads. When I have to put new pads on I get the vibration and noise until I get multiple hours and landings on the airplane then it goes away.

No guarantee but it's worth flying for a while. These noise/vibration problems are very hard to track down sometimes. It will make you treat your brakes much more gently as you don't want to change them very often.

Andy
 
I can say for certain if you get hydraulic oil on the rotor or pads, the brake can vibrate and make really bad noises. The only answer is to sand the rotor surface and decontaminate and replace the related pads.
I have actually heard this noise on the airlines from time to time. After awhile it might go away if the oil gets burned off.

Your new rotors look overheated somehow. That could also damage the pads.
 
Curious if the OP did anything with his wheel bearings after the fire?

I installed heavier disks last year, and for the first 15 or so cycles, I had "moaning" emanating from the right brake, especially when subjecting it to a side load (turning) during ground ops. Eventually the noise faded away.
 
Double check procedure for setting the wheel bearings, make sure they are not loose. Also, since you had a brake fire, check the clearance between the caliper drive pins and the back plate, and also if the back plate is warped.
 
I didn’t take the time to read all responses but we have seen this numerous times over the years when people change from solid lines to long flexible ones.

Any flexible line has some level of expand ability under pressure. The actual amount will vary with the type of hose used.

This expandability can develope a natural resonance between the caliper/disk, and the expansion of the hose.

Flexible hose is very common on certified aircraft, but I have never seen installations that use it for a 3-4 ft run. It is usually just short hoses at flex points with solid line for the remainder of the circuit.

Why long lines work in some instances and not others is still a bit of a mystery, but it is likely related to numerous factors as variables ( I.E., disk run out, etc.)
It is very possible that the addition of the long hose is the problem.
 
Per plans aluminum lines from the outset; always had the noise on right side only. It's not at all unique to flexible lines.
 
Hmmmmm.....

A variety of answers here. I have never had an issue like this until placing this new line on. It's way too loud and upsetting to let it go so I guess I'll start by resurfacing the rotor to get any residual burned fluid off that's been swapping between rotor and pads. Can I just sand rotors myself with sand paper? How about the pads?

This with maybe a bevel on the pad and some brake quiet. If those don't fix it then I guess I'll have to make rigid brake line again. Does anyone have the Vans specific plan for the brakes? I want to make it per the book.

Thank you!
 
#3 hose with #4 fittings also. No noise@

I have #3 hose with #4 ends. Polymer jacket over the SS braid. Full run from fuselage bulkhead fitting to brake housing. Got the lines from Bonaco.

Never an issue.
 
As I wrote previously, many people have had the flexible lines work. Some have not. It is doubtful that all used the same exact installation so knowing what is "different" is the only info that would be helpful.
I think trying the antisquel compound would be worthwhile. Some automotive brakes aren't free of squeal unless it is used.
 
On my plane, those four spacers/bolts holding the pucks together can get cocked, causing the pads to bind. It seems like there should be some kind of lubricant to use on them but, so far, I just run them dry. I've had to kind of pry them loose after changing a tire.
 
If you are considering changing lines I have flexible brake lines made by TSFlightlines for RVs. I do not have any noise.
 
Had the same chattering noise on my wifes plane.
Changed pads,changed to pads with different composition,used anti squeal spray,angled the front/rear edge of the pad. Never cured it,but spent hundreds of dollars trying.
 
I have no experience with this chatter, but you might want to check the alignment with the disc to the backing plate of the caliper. If the bracket, or pins, cause it to be twisted, then the twist of light loading would result in unloading the pad. Then it releases and repeats. Since many have found stop after some use, this is a more likely issue. The pad on the loose, narrow puck is more likely to self align than the more rigid backplate.

Good luck.

Edit, I call this chatter based the low frequency of the video, not squeal which would be a tuning torque resonance along the axis of the piston. Squeal would be addressed with coatings and such under the pressure surfaces.
 
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I fully agree with Scott and the others pointing to the flexible lines. I had the same on more than one RV. It is a resonance.

I had exactly the same noise on more than one RV - thought my dentures would fall out ;)

On my own RV I have fixed it by merely clocking the 90 degree fittings on top of the calipers to point about 10-20 degrees inward. My flex lines are a lot shorter than those of the OP but it is worthwhile trying. Just experiment a bit.

Secondly I have fixed it one another RV by slitting a rubber hose in length and fastening it over the last few inches of the flex line using tie wraps. again it might need experimenting.

Why I do not like the alu lines - you sometimes pick up chaving or it gets nicked along the way. Then as per Murphy's laws it will fail on landing at the most remote place on earth and if you have a nose wheel that is not fun :mad: I have he T-shirt for that one.
 
Per plans aluminum lines from the outset; always had the noise on right side only. It's not at all unique to flexible lines.

Being the largest fabricator of BOTH Flex lines and Custom CNC bent rigid tubes for RV aircraft worldwide, I read this entire thread and the comments in it with great interest.

Here is what we have found throughout the years. Our data points include Hundreds of RV aircraft with flex hose gear leg installations.

1. We have seen no difference in the utilization of -4 hose/fittings, -3 hose/fittings, and -3 hose with -4 jump size fittings. We utilize all three of these types of assemblies for gear leg hoses.

2. Our cnc tube bending equipment would allow us to fabricate gear leg tubes in aluminum. However, flex hose is a superior product for this application with better performance and longevity. For that reason, we choose to stick with flexible assemblies for the gear legs. It is more costly for us to do so...but we have found it to be a better product.

The exception to this is that we will be offering prefab rigid tubes for the RV12iS Gun drilled gear. The ONLY reason we will offer that is because as an ELSA build, the tubes must conform with the plans. The plans show a self fabricated rigid tube assembly.

3. What we have found is that harmonics or dragging of brakes can occur if a side load is placed on the caliper. As Jan stated, clocking the fittings 10-20 degrees differently made a difference in his application. The small clocking change affects the angle at which the hose/tube goes into the calipers as well as the loading placed on them.

4. 3003 versus 5052- This is an entirely different discussion. Vans utilizes 3003. Most certified aircraft utilize 5052. A search on this topic will yield a multitude of results including information directly from the Standard Aircraft Handbook. Re posting any of that would likely result in a flame war and a discussion that isn't directly related to this topic.

Regarding the issue that the OP has with the aircraft..... I think that there were a lot of good points and suggestions made on this thread. I am curious to hear what the final culprit ends up being.

Happy Building
Steve
 
All==10 + years ago we started making teflon brake hoses to help with a couple of issues.
1) the catastrophic failure of the flare on the OE aluminum tubing from induced vibration.
2) Some builders---not you professionals, wer having issues flaring tubing, and bending the tube around the axle without kinking it.
So on a few early planes, a couple of RVs and a F1 Rocket, we did some tests, and had excellent success. No moans, no drips, no flares breaking, even with a long hose. The flexible hose seemed to dampen any vibrations that may occur.
Since then---1000+ aircraft around the world have our teflon hoses, and no telling hose many in other countries have those from other vendors.

In the cas of the op----if I may---the rotors do appear to be heated---since Charles stated he installed a new rotor, and now after a very short time its heat discolored again. I suspect the noise you here is in fact a brake moan----the pads havent been bedded to the rotor, and there is a glase. Gee---heavy trucks do it---just listen.
The automotive industry came out with metallic brake pads, and gee created a new market for anti squeal gels and shims. Every heard a early Volvo---you could hear the squeal from a block away--- and sometimes with all of that there seems to be a moan.
To the ops point---it seems that there is alot of discoloration for such a short service time, and to ME, that indicates alot of brake heat---gee maybe the cause of the original fire (?). The pad should not contact the rotor without brake pressure---induced friction will cause the brakes to heat even without feeling the brake affect, OR hearing anything. Something appears to be causing that, possibly a master cylinder that has its piston depressed slightly keeping residual pressure on the caliper piston, not allowing retraction AND the pads riding on the rotors.
NOT to say that a hose couldnt contribute to the issue--and not to criticise Charles' install---because none of use are there--but there does seem to be enough of an issue to want to examine everything and see what the culprit may be.

Tom
 
To Jan's point----looks like he had some induced vibration because the caliper was binding at an angle due to the install. Turning the inlet fitting slightly does put the HOSE or TUBE at a different positon, and COULD possibly remove the binding action of the caliper during braking.

Perhaps some of our Brake engineer friends can chime in here--

Tom
 
All thanks for the awesome help. I'm going to dive into it today a little and systematically go through a few steps to see if I can narrow it down and hopefully provide a little information. These are beautiful lines and I am sure that it is a matter of something I have done incorrectly as I am not an expert at these things. I'm still in the learning process.

As for the coloring on the rotor, I believe that is residue from the pads that were used on the burned rotor transferring to the new rotor which has become a vicious cycle. I think I will late this rotor to clear it all off and put on (once again) new pads to eliminate entirely the possibility that residue is causing this. The brake does not sound like it is dragging, nor is there any pull when taxing.

I'll follow up with my findings! Thank you!
 
I'm certainly not an expert in this area but I do think that Tom may have a point. Sometimes it's easier to look at the symptom of the problem and not realize that there is an underlying root cause for the problem. That in fact may be returning on the updated install.

In my EE work we try to minimize the number of variables when we are trying to track down problems. The fact that you changed the type of brake line could actually have nothing to do with the real cause of the problem it is only a change that was made. Or it could be a different problem entirely. My generic suggestion is to try to break the problem down and minimize the number of variables.

As I said before I don't know a lot about this area. I have worked on car brakes and that is the extent of my experience. Just trying to provide my 2 cents to help were I can and learn from others experiences.
 
Charles----just for giggles---there is a temperature indicating paste that is available---most race care shops sell it----that will indicate the max temp of the area. Might be a good idea to get a temp reading----

Tom
 
Vans DWG C2 shows the fuel line on top and the bleed valve on bottom, Matco Brakes says you can switch the bleed valve on top or bottom but bleeds better on top as the air goes up but with wheel pants on the RV's the aluminum tube would fit better. If it's not rubbing on anything and its a matco brake, you are suppose to tighten the axel cap so the rubber seal on the bearing stops turning with the wheel then tighten it a1/4 turn not any tighter, if it's spinning with the wheel it may make a noise or if it's too tight. Get a brake manual if you don't have one, I know Matco uses Nord-lock washers so different Torque. Also you might fly it without the wheel pants to test for noise. Good look
 
I'm certainly not an expert in this area but I do think that Tom may have a point. Sometimes it's easier to look at the symptom of the problem and not realize that there is an underlying root cause for the problem. That in fact may be returning on the updated install.

In my EE work we try to minimize the number of variables when we are trying to track down problems. The fact that you changed the type of brake line could actually have nothing to do with the real cause of the problem it is only a change that was made. Or it could be a different problem entirely. My generic suggestion is to try to break the problem down and minimize the number of variables.

As I said before I don't know a lot about this area. I have worked on car brakes and that is the extent of my experience. Just trying to provide my 2 cents to help were I can and learn from others experiences.

I agree, there are a lot of variables and zeroing in on a cause of this type of condition can be a challenge. Further proof of that is that chatter with hard lines happens occasionally as well.

But based on past experience and the fact that the major change that was made was adding a flexible hose, I think there is a strong possibility that the cause is related to the hose.

Replacement of the hard lines with hose is nothing new. Builders have been trying it for far longer than Steve and Tom have been making and selling custom hoses. The first chatter/squeal instances related to the use of flexible hoses thatI was made aware of occurred in the mid to late 90?s.

I am not aware of anyone ever identifying anything specific to explain why it works in one installation and not another. Could it be that the use of rubber lined hose allows for more expansion than when Teflon lines hose is used?

It might be of some help if Steve or Tom we?re willing to post the installation specifics of their hoses that allow them to always work with no problems (type of hose, clocking of fitting, etc.)
 
I agree, there are a lot of variables and zeroing in on a cause of this type of condition can be a challenge. Further proof of that is that chatter with hard lines happens occasionally as well.

But based on past experience and the fact that the major change that was made was adding a flexible hose, I think there is a strong possibility that the cause is related to the hose.

Replacement of the hard lines with hose is nothing new. Builders have been trying it for far longer than Steve and Tom have been making and selling custom hoses. The first chatter/squeal instances related to the use of flexible hoses thatI was made aware of occurred in the mid to late 90?s.

I am not aware of anyone ever identifying anything specific to explain why it works in one installation and not another. Could it be that the use of rubber lined hose allows for more expansion than when Teflon lines hose is used?

It might be of some help if Steve or Tom we?re willing to post the installation specifics of their hoses that allow them to always work with no problems (type of hose, clocking of fitting, etc.)

Would be nice to know the details.

I can say that I had my "per plans" aluminum lines brake setup make noise once after a caliper rebuild and brake pad replacement. My fix was to "bend" the aluminum line slightly (left or right I do not remember) from the fitting changing the side load on the brake caliper. Any time I would get noise after that, I knew the alignment of the tubing to the fitting on the caliper was off and needed an adjustment.
 
I agree, there are a lot of variables and zeroing in on a cause of this type of condition can be a challenge. Further proof of that is that chatter with hard lines happens occasionally as well.

It is definitely difficult to pinpoint exactly what the major change in this situation is as there seems to be a lot of them.

1. Fire 2. New Tire 3. New Tube 4. New Pads 5. New Brake line 6. New O Ring 7. Bleeder Valve Swap 8. New Rotor 9. Second set of new Pads.

However, what I find interesting is this. After the initial change, the problem didn't present itself until after a couple of flights and then got progressively worse.

After the Rotor Change, the same thing happened. Initial testing was fine and then it appeared again and got progressively worse.

After the second pad change, the same thing occurred after about 5 minutes of heating up.

Figuring I had the problem licked, my initial first brake attempts had no sound, then to my dismay, about 5 minuted into taxi test it came back again! :(

I am curious if this happens if you test it now. Does it start immediately, or does it still first start after about 5 minutes of taxiing?

I can say that I had my "per plans" aluminum lines brake setup make noise once after a caliper rebuild and brake pad replacement. My fix was to "bend" the aluminum line slightly (left or right I do not remember) from the fitting changing the side load on the brake caliper. Any time I would get noise after that, I knew the alignment of the tubing to the fitting on the caliper was off and needed an adjustment.

This is very true. Jan also mentioned this. We have heard (no pun intended) that side loading on calipers with either flex or rigid tubes can cause noises.

It might be of some help if Steve or Tom we’re willing to post the installation specifics of their hoses that allow them to always work with no problems (type of hose, clocking of fitting, etc.)

Happy to answer this question

Our brake hose assemblies are all PTFE Teflon with a stainless steel braid in -3 or -4 size. Most are clear coated with an anti abrasion clear plastic. The hose has an approx 3,000 PSI working rated pressure and a >9,000 psi burst pressure. We do NOT utilize any rubber lined hoses for any of our assemblies.

Fittings utilized are -3 or -4 stainless as are the collars utilized to crimp the assemblies.

Collars are all crimped utilizing a CNC crimper for repeatability. Assemblies then undergo hydrostatic pressure testing prior to shipment.

For more detailed information, here is a link that has fabrication and testing videos.

http://aircraftspecialty.com/howwemake.html

As far as the second part of the question regarding installation specifics....that would be impossible to post as we have over 30 build sheets just for gear leg hoses on a variety of aircraft. They come in a variety of configurations. Some hoses utilize straight fittings, some have angled fittings, some have banjos, some go straight down the gear leg, while others wrap around the axle. The "Standardized" assemblies were all designed and built with the help of beta testers around the world. Many others are built custom based on owner specifications.

WingnutWick- There are some good comments and suggestions in here, and I'm sure you'll get to the root cause of this. If Tom and I can be of any assistance, we are happy to help.
 
The results

Alright folks, here's the breakdown of yesterday?s work and findings. I wanted to be able to see if I can isolate it to one thing for future information vice doing all the suggestions at once so I started with the easiest and went from there.

First I tried to "clock" the fitting. I moved it so that it alleviated the bend that was previously there. Initial taxi test seemed good, I was excited, and how easy a fix. But then it came back after a little more taxiing and braking. The tendency for it to happen after a little bit of operation I?m guessing has to do with being heat related? Either the pads or the fluid in the lines as it occurs after everything is warmed up a little. Not enough info though to say for sure.

I tried clocking it further both inward and outward. No luck. I tried removing some of the zip ties I had to prevent any undue pressure being applied on the caliper. No luck. Next I jacked the wheel up, and made sure everything was looking normal and tight with the bearings, axle, pressure plate, etc. I beveled the leading and trailing edge of the pads a little as suggested, and added brake quiet. Cleaned the rotors and pads. It was just as bad as before.

My final option before deciding to belligerently throw bundles of money at the problem and buy a whole new wheel, bearing, and brake assemblies, was to fabricate a rigid line as I had before. I had the tools and tubing in my hangar so I did just that. Lo and behold - the horrible noise and vibration was gone! Not a squeak, just as silent as the other and my 8's! I did plenty of taxiing and a high speed abort to simulate landing followed by a flight. Nothing at all! Just to be sure I waiter until today to test it agin before posting this, and after much operation, the noise is gone! Sigh of relief.

While I was keeping an open mind about it, my gut was telling me after I had read a lot of previous archives of "brake groan" following installation of flex lines, that this was the case. Now let me say, these lines are absolutely beautiful and extremely well crafted. Super high quality. (Steve I'm sure yours are the same as well :) ) Not to mention recommended to me by a lot of people. But there seems to be the occasional RV'er out there that these do not work well with. The interesting question I'm curious about (for Tom and Steve) is why they work on most, but cause this resonating vibration sound on others? A couple people stated "hydraulic resonance". My lines in particular ran from the fuselage to the brake assembly and were on the long side from what I gathered (50.5 inches), I'm not sure if that contributed.

I wonder if a -3 line would have made a difference. It may be that whatever setup I had was imparting some pressure on the system that was causing this. Short of making some support bracket, I tried manipulating the position and support via zip ties. I'm tempted to test out different lines (like a -3) to figure it out but as of now I (and my girlfriend) are just happy her plane is back functional so I'm going to take a "brake" from meddling underneath it and enjoy flying it!

Thanks all for the great help, as always this has been great learning experience and I've furthered my skills and knowledge in the brake department with this whole fire debacle. And thank you Tom for the lovely lines, and to both Tom and Steve for sharing their insights into their lines. I am going to see if they will work on my 8 at some point without the same issue. This is obviously a one in thousands occurrence. I wonder if we can figure it out! It may simply boil down to the possibility that the nature of flex lines results in a smaller tolerance for positioning than what you can get with rigid lines, in the fact that with rigid lines you can essentially sculpt a spiral straw with them and they will work as long as the end ends up aligned with the fitting with no pressure (which is easy to do). I?m sure that this was just a matter of amateur craftsmanship on my part. I shall re-attack these at a later date.

Thanks again all!

Cheers!

Wingnut
 
Interesting. I will be installing flex lines in the next week or so to replace rigid tubing that has some workmanship issues, and a nick from the wing root fairing that I discovered during my annual CI. The original installation is not exactly what is shown in the plans, and the bends are a bit "flat," so I hope to improve on the current configuration. While I'm at it, I'll be removing surface corrosion from the gear legs, and repainting with epoxy paint.
 
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The interesting question I'm curious about (for Tom and Steve) is why they work on most, but cause this resonating vibration sound on others? A couple people stated "hydraulic resonance". My lines in particular ran from the fuselage to the brake assembly and were on the long side from what I gathered (50.5 inches), I'm not sure if that contributed.

Wingnut

From discussions over the years with people that have had this occur, my theory has always been that it is related to the expandability of the long hose under high pressure.
Any object will expand under pressure. On some, they are stiff enough that it is only at a molecular level and for others it might even be measurable with a caliper.
My theory is that in some cases, there is an interaction between the brake system and the expansion of the hose that occurs at a natural resonance. Perhaps because of run-out of the disk, or a slight thickness variation?
I think it is the long length of hose, having a lot of expansion area along its length, that it acts like a compression spring under the high pressure.
I think that if you had a hard line with just a short length of flexible hose at the end (like is typically done on certificates aircraft), you probably wouldn?t have seen the problem.
I imagine some types of hose material can expand more than others when exposed to high pressure. I don?t know if that is a factor in the hoses working in a lot of installations but not in some, but it could be.
Do you know whether your hoses have rubber or Teflon liners?

Regardless, glad to hear that you narrowed down the cause.
 
Charles---very glad that you isolated the problem. Kinda weird, but stranger things have happened. Yes the liners are teflon, and yes we've had some gear hose that were longer---and no problems. As Scott said, quite possibly there is something in this install that has a natural resonance.

Tell you what----We'll be glad to make you short hoses coupled to rigid tube when you get to that point if you wish. Also---obviously you can return the hoses for a full refund including the shipping.

This has been one of those experiences that get filed int he memory banks---

Tom
 
That would be interesting. Whats even more interesting is why on this aircraft---and not others. Smarter minds than me will have to figure it out.

Tom
 
It might be worthwhile to use an adel or WDG clamp to the gear leg within 3 inches of the caliper. Or just electrical tape and firm zip ties for an experiment to snub the flex line to something solid, close to the caliper.

Even on the -4 line. I suspect if the hose is held stiff enough to damp any stick slip movement all might be quiet. My legs have about 4 or 5" lengths of -4 flex line from a 90 elbow into the tops of the caliper. Then they arc 90deg up the gear leg to hard AL lines that are only electrical taped to the Ti gear legs under the gear fairings. Smooth and quiet.
 
Bob--and others---I dont have an answer to hoses questions---we didnt do the install. Probably going to chauk this ine up to a strange occurance---but definitely remember it.

Tom
 
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