Avid MK4 braking effect


26 posts in this topic

Posted

My 1st Avid was a model B. I flew it for over 2,000 hours until I totaled it on a challenging back country Sierra strip. It had single MATCO pucks on each wheel that were never very good braking. I even modified to standard poor geometry brake pedals so to give the proper leverage on the brake cylinder. 

On my MK 4 I actually made the MATCO modification to add 2 pucks on each wheel. The brake pedals have good geometry. Still the braking is not great. I have 1700 hours on this Avid.

A friend bough a MK 4 nose-dragger and when I flew it I was surprised at how well the brakes worked. His set up was like mine using the remote reservour. And he only had single pucks.

Recently I found the brake pucks starting to leak so I bought new O rings, new filler nipples and the newer slide spacers that are stainless and so should not corrode restrictingh the ablility of the pads to slide on the spacer/slides. 

I'll check them out on today's flight, but I don't hold out much hope that they are adequate.

I should mention that I had a damaging accident 2 monthes ago when I landed in my tail-dragger MK4. I put on the brakes to slow down and then let off. One of the right brakes stuck in the on position causing a ground loop that put me up on the nose and left wing tip. This damaged the outboard flaperon hangar and busted on of the blades on the Whirlwind composite prop. Fortunately no damage to the crank from prop strike.

Make sure the brake pad slides are clean. 

 

John M

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Posted

I've been having some brake issues as well John.  I even made some different brake pedals, but it's hard to not be applying some brakes even if you don't want to with them.  I bought some new Matco master cylinders that should arrive today.  They are really short, and I've modified some Kitfox 1 brake pedals to go on the plane, cause they provide way better leverage.  I'll see how they work out and then post pictures and such.  JImChuk

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Posted

There must be something different between your brakes and those of your friend if his worked so well. Can you check all the geometry? Does he have the intensifier kits in his master cylinders and you don't? I'd sure like to know what you find if you figure it out. 

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Posted (edited)

We have circled this drain at least 4 times in the last few months! Most Avid brake problems are due to crappy mechanical advantage at the pedal tops, where the brake has a 1:1 ratio to the brake cylinders. Here is one post:

 

Edited by nlappos

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Posted

My two set ups. Stock calipers and rotors with 1/8” nylon line. Both have the Matco intensifier kits in the MCs and both will lock the tires landing on dirt if not careful.

C2CCC525-A3FD-46B7-87B6-566290D04D43.jpeg

8BB7986B-6999-49E6-8000-A012B8FA422D.jpeg

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Posted

Well I didn't make much progress on the brakes today.  Had to take the wife to a doctor's appointment about 75 miles away.  When I got home my package of master cylinders was in the mail box.  It had been ripped up pretty good, and had been taped back together.  It took over a week for a priority mail small package to go from Salt Lake City Ut. to Mn.  (by way of southern Cal.)  Opened the package up and there was only one cylinder in there.  So did Matco ship only one or did one get lost when the package was torn up?   And to top it off, Matco was closed for about 10 minutes when I tried to call.  Another odd thing, there was a package of two silver rings in the box.  I sure didn't order them..... I think I ranted and raved for 15 minutes.  I missed some nice flying days waiting while the plane was torn apart, and now it will be a while yet.  I'm getting mad again thinking about it.  Joey, what model cylinders do you have on the two planes in the pictures?  JImChuk

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Posted

I found that fluid was leaking from my MATCO brake pucks. Two on each wheel.

So I ordered new O rings, stainless puck slider spacers and new fill nipples.

I purged the system, but couldn't get the left brake master cylinder to get the solid feel that the right one had. We didn't see any bubbles.

So I took the left master cylinder (short one with remote reservour) apart and found some sore of dirt in there. There is a part that slides along a shaft that I believe works as a check valve. It was sticking so I replaced the outer O rings and the inner O ring. 

They are a bitch to reassemble. It took two of us to push in the unit far enough to reset the snap ring. This rework has corrected the issues.

For those who mentioned it, I have excellent geometry on my pedals. A friend has a Kitfox and there is plenty of room to get the ball of your feet up high on the pedal. The Avis is restricted so that only the tip of my toe is on the top of the pedal. Any higher and you contct the crossbar on the firewall. Poor design.

I had mentioned that my friend with the nose-dragger had excellent braking. That said, that breaking could be an issue in a panick stop and have you on your nose in a tail-dragger.

So there is a fine ballance between too much and too little braking.

While working on the brakes we noticed that the bolt on the forward left landing gear leg attachment had a broken. The head of the bolt was GONE. 

So I replaced that bolt and will replace all of the others. and since I fold my wings every time I put it in the hangar I am going to replace the Jesus bolts where the strut pivots at the fuselage.

John M

Avid MK4 with Jabiru 2200. Built in 1996. 

Commercial Pilot, 8000 hours, 1200 in Cessanas, 2400 in Ultralights, 2800 in Avid model B  1600 hours in MK4.

 

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Posted

Has anybody installed a hand brake system?  I bought one for my FSII and didn't use it, I thought I would put it in my Avid. There is a guy in Tenn. that has that system in his Kolb MK III and loves it.  The control levers are located beside the seat next to the throttle. 

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Posted

this is a little drawing i made few days ago cause was wondering about brakes.

the idea, push them from bottom to simplify linkage and so put brake on side where they not take to much place in the small cockpit. may be it can be more simple by placing brake in middle Y, but i'm rope start so i personally can't

By the way i stay origin for now , will see after test flights 

IMG_3410.thumb.jpg.5bf3e2b237161885ed82d

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Posted

Has anybody installed a hand brake system?  I bought one for my FSII and didn't use it, I thought I would put it in my Avid. There is a guy in Tenn. that has that system in his Kolb MK III and loves it.  The control levers are located beside the seat next to the throttle. 

Yes I did install a hand brake system on my MkIV. I installed it because I had trouble braking and using the pedals at the same time (by the way, the previous owner had made 2 ground loops!). I put only one master cylinder, controled by a lever below the throttle . I think I already posted a pic of this setup somewhere in this forum.

Sure it limits the ability to make short turns on the ground, but I feel much safer!

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Posted

mini_870031IMG20170312155953.jpg.5d1b62c

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Posted

I have two master cylinders and two levers.  It is easy to either use differential braking or both at once.

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Posted

Just watched the video.  Seems to work okay. I bought mine from Black Max brakes.  Both master cylinders and levers are mounted together.  Roll your hand left for the left turn and roll your hand right for a right turn, pull both for full stop.   No switch,  all mechanical. I'm going to mount it on the right side of the seat just behind the throttle.  Simple. 

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Posted

Brake pedal geometry came up on another forum and they linked here: ultralight news

There are diagrams from Matco on the proper geometry for brake installations which I've attached below. Hopefully someone finds them useful and they haven't already been posted 20 times on this forum.

matco-4.jpg

matco-5.jpg

matco-1.jpg

matco-2.jpg

matco-3.jpg

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Posted

The brake pedal in the first drawing looks very much like the Kitfox 1 pedals I'm going to be using.  In the original Avid MK IV pedals, you have about a 2 1/2" high pedal, and the arm is about 2" long, Kind of like the last picture.  No doubt which one has better leverage.  Also, I was able to get a hold of Matco today.  I was about to have eye surgery, and the nurse was getting some things ready, so I asked her, How long before I"m going in there?  She figured I had 10 minutes, so I said, I have an important call to make.  Talked to George there, and sent him pics I had of the tore up shipping box, and later after surgery, I had an email with a tracking # showing another cylinder is on the way.  George Happ is a good guy!   JImChuk

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Posted

I assume the KF1 pedals are the better design since those are the ones you're using?

I had no idea Matco was in SLC. that's just on the other side of the mountain from me. 

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Posted

Yes, and yes! :) JImChuk

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Posted (edited)

Just watched the video.  Seems to work okay. I bought mine from Black Max brakes.  Both master cylinders and levers are mounted together.  Roll your hand left for the left turn and roll your hand right for a right turn, pull both for full stop.   No switch,  all mechanical. I'm going to mount it on the right side of the seat just behind the throttle.  Simple. 

Yes, and the interesting part is that even if I just use the common main and brake on both tires I can still maneuver very well. Obviously not super sharp turns but when applying moderate brake and rudder you can turn surprisingly sharp. If I didn't do mountain flying (where the room for maneuvers, like in bush flying, sometimes is limited) I would onbly have the stick hand brake and not bothered by the switch.  

Being able to easily apply equal brake force when you need to slow down quickly really makes a difference. It is also easy to raise the tail before starting the take off roll and keep it up while decreasing the brake power when gaining speed. A little dip of the tail and you are of the ground. Just like the big boys.

Edited by FredStork

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Posted

I sent an email to George at Matco this morning, and got some more good info back from him along with a few links you may want to look at.  JImChuk

Jim,

I’m glad you were able to see well enough to read your email J  Thank you for the kind words and sorry that it took two tries to get both cylinders to you.  My wife is having eye surgery next week.  I’ll let her know your’s went smoothly.

 

The early Avid’s and Kitfox suffered from horrible pedal geometry.  Not only was the mechanical advantage low, the configuration caused the geometry to get worse as the pedal stroked!.

 

You should review the document on our website regarding brake output.  It is at:

 

https://static.veracart.com/matco/item_pdfs/3648/document1.pdf

 

You will find it is very applicable to the Avid issues. (especially the examples of how not to do it)  When diagnosing a performance issue, it is always best to verify the brake pressure at the caliper.  Our brakes require 450 psi to get the rated torque.  More torque will be produced above 450 psi but it is less linear above that pressure.  It is analogous to trying to determine an engine output problem without knowing RPM or manifold pressure.  A reading should be taken at the caliper.  This value will take in to account any geometry and ergonomic issues and provide a direct reading of what performance to expect.

 

To help facilitate this diagnostic, we offer a rental gage for the application.  It requires the use of the new style brake bleeder so if you have an older caliper, you will need to purchase one of the bleeder assemblies.  (The new sealed bleeders make the bleeding process cleaner so they are great to have anyway.)  The links are:

 

http://www.matcomfg.com/GAGEBRAKESYSTEMPRESSURE-idv-3934-35.html

http://www.matcomfg.com/ASSEMBLYSEALEDBRAKEBLEEDER-idv-3863-35.html

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Posted

. If I didn't do mountain flying (where the room for maneuvers, like in bush flying, sometimes is limited) I would onbly have the stick hand brake and not bothered by the switch.  

Being able to easily apply equal brake force when you need to slow down quickly really makes a difference. It is also easy to raise the tail before starting the take off roll and keep it up while decreasing the brake power when gaining speed. A little dip of the tail and you are of the ground. Just like the big boys.

I tested a motorbike brake handle on the stick but it did not work (the volume of fluid displaced by the piston was not sufficient for an efficient braking)

Having the brake handle at the center has the benefit that you can fly the plane from either seat (being an long time glider pilot, i feel better having the stick in the right hand, and I  fly often in the right seat)

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Posted

 

I have my throttle on the left side of the seat, with the left hand always resting on the throttle so I pilot with the right hand and now also brake with the right hand. I got a 20 euro motor cycle brake handle from china, works great...  

The (my) only inconvenience with the right hand on the stick is for killing the flaps at touchdown. If you fly with the left hand and throttle with the right hand the right hand will be free for the flaps (flaperons)... Thinking about how to make a double command for the flaps on the left side of the seat... Another winter project... 

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Posted

Are you using the flaps regularly? I tested them once, but was not convinced: they cause a lot of forward pitch. As my strip is quite long (350m) I dont really need them.

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Posted

Yes, I always land with flaps (except on some mountain strips) to land at lowest possible speed. It is a good practice for the day you need it. Slower speed also reduces the tendency to bounce (as does killing the flaps...). When it pitches forward to keep the speed but just pull the stick back and see how wonderfully slow the Avid can fly. 

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Posted (edited)

Note the two photos, the old fat brake cylinder cannot fit close enough to the pivot point so it has about 1:1 mechanical advantage, and you get weak brakes. The new thin cylinder (with remote reservoir) fits much closer, and the new hole as compared to the old hole farther out on the tab shows the increase in mechanical advantage, about 2 1/2 times more powerful brakes. And it works.

 

IMG_0154.JPG

 

new pivot.jpg

Edited by nlappos

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