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need advice


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Posted

On my KF4 with 503 Rotax , I installed matco  6" wheels and brakes and 8:00-6 tires... THe brakes barely worked. I added another set of calipers to each wheel so now I have two brake calipers on each wheel and the brakes are better. I can hold the left brake and pivot around but i HAVE TO  push prett y hard on the pedal....I tried conditioining the brake pads and that helped a little... 

 

The second issue is I flew the plane the other day and at 6000 rpm, 2 blade WD prop = about 80. 

I installed vgs on the wing and a new WD taper blade prop, same 72" diameter... now I cruise 85 at 6000 rpm but the nose wants to rise and the flap handle is all the way down....

IS it ok to adjust the flap handle to go lower to be able to trim the plane? Are the VGs makeing the wing create more lift or is it just the extra 5mph speed????its got me stumped.

IT will stall about 35 flaps up and I saw speeds as low at 30 flaps down but that was about it... the air was so rough again it was hard to get accurate speeds but they do seem to help.

I have grove gear and it sits too low....I can tell because when the plane comes off the ground it jumps up about 30 feet in the air like a rocket... I just cant get any more angle.... should have orderd 2" longer gear legs. Or I can insall bigger tires I guess....

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Posted

Also I keep getting my right toe caught under the throttle lever above the right rudder pedal.. I have sz 14 feet... maybe I need to cut off my toes...

 

Ive seen some people put flat metal on the rudder pedal that still allows the brake to be applied... not sure what to do...I have to use my toes to work the rudders......kinda hard....

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Posted

My experience the wd taper gives you more power. 

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Posted (edited)

On the Avid, pulling in just a bit of flaps will cause the nose to go down.  Actually, the more flaps you pull in, the more the nose wants to go down.  I'm sure it's the same on the Kitfox 4.  I trim my Avid that way all the time.  I've also noticed that with several Avids, pulling just a bit of flap made the plane fly better, more stable.  Not sure why.   As far as the size 14 shoes, I see that Trent Palmer is flying barefoot in his latest video.  :-)  JImChuk

Edited by 1avidflyer

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Posted

So can you hold full power on a runnup or will the plane creep away?do they feel spongy beyond typical flexing in the rudder bars and pedals themselves? If you have air trapped somewhere they won't work for nothing no matter what you do. And it can be dam tough to get rid of it sometimes. 

Do you have vg's on the tail as well? Horizontal  stabilizer underside just in front of the hinge point?

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Posted

sorry for the late reply... I cant hold the plane with the brakes above about 3000 rpm even with dual calipers on each wheel . I installed a pressure guage on the wheel cylinder and I am only seeing 220psi if I stand on the brake pedal really hard.... I talked to matco engineering and he said the brake pedal geometry is wrong, however looking at my brake pedals, they are stock kitfox IV pedals and I dont see how to get any more mechanical advantage.....A small master cylinder might make more pressure....Im stummped for now....

I removed my 503 rotax and am trying to install a blue head 582 new engine... I have a different mount coming that has two vertical rails on each side and 4 small aluminum brakets that bolt on the corners of the engine...even that Im running into problems.. I have 3 of the mounts on but the left front side of the engine has one 8mmx1.5mm bolt and one hole is smaller and off center . I know I have to drill and tap and new hole and I am guessing with the mount so it is horizontal and vertical with teh engine....the new hole would be right next to the smaller hole but if I use that the mount bracket will be crooked.....

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Posted (edited)

Don't know what to tell you on the brakes, I think you are right about smaller cylinders giving more pressure.  More travel on the pedal also, but it's really a matter of leverage.  I'm picking up a Kitfox 3 project on Friday that has a new mount for the 582.  I'm sure it's the same as would go on a Kitfox 4.  I won't be using the 582 so the mount will probably go up for sale.  JImChuk

PS  If you look at the engine in the picture I posted, you see the mounting locations for your new style of mount on the sides of the engine directly below the ends of the exhaust manifold.  I sure wouldn't go drilling any holes in the engine without having the mount right there with me.  I can't imagine that the holes are in the wrong spot, unless someone built the mount wrong.  Was the mount made by Kitfox?  I'm sure they know what they were doing.

Kitfox 3 -3.jpg

Edited by 1avidflyer

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Posted

sorry for the late reply... I cant hold the plane with the brakes above about 3000 rpm even with dual calipers on each wheel . I installed a pressure guage on the wheel cylinder and I am only seeing 220psi if I stand on the brake pedal really hard.... I talked to matco engineering and he said the brake pedal geometry is wrong, however looking at my brake pedals, they are stock kitfox IV pedals and I dont see how to get any more mechanical advantage.....A small master cylinder might make more pressure....Im stummped for now....

I removed my 503 rotax and am trying to install a blue head 582 new engine... I have a different mount coming that has two vertical rails on each side and 4 small aluminum brakets that bolt on the corners of the engine...even that Im running into problems.. I have 3 of the mounts on but the left front side of the engine has one 8mmx1.5mm bolt and one hole is smaller and off center . I know I have to drill and tap and new hole and I am guessing with the mount so it is horizontal and vertical with teh engine....the new hole would be right next to the smaller hole but if I use that the mount bracket will be crooked.....

Well if this is all you are getting for pressure and holding sounds like air or maybe the caliper is binding on the guides, or both. does the plane have the E style parrelogram brakes or the earlier ones? A lot of guys are filling their brakes from the bottom up thru the bleed screw using a piece of tight fitting rubber hose and a veteranarian srynge to make sure all the air gets out.

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Posted

It has all Matco W62 wheels and hydralic brakes and brake cyliders with a remote reservoir. I careflully bled the air.. In alaska we put aeroquip 303 hose on a cub for brake lines and it didnt work worth a damn. The brake lines were in fact expanding so the brakes never felt stiff, only soft, they worked but not well. Nowsay people use either ridgid lines or small teflon lined stainless brake line and they work better...

I installed the double calliper setup as shown by Matco. Still my  master cylinders only produce 220psi if I stand on the pedal hard, very hard... It needs a small diameter cylinder I think. There are brake intensifiers from Matco that make the master cylinder 1/2 piston in stead of .625 dia piston so maybe that will work.....I dont think I can make the top of the brake redal taller as my right foot toe fould on the throttle cable belcrank... I could move that I guess..... Matco says I need 450psi for the brakes to work right....its got me stumped.....mark smith

exfaa@outlook.com

907-378-9632

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Posted

It has clear lines and I could see the air bubbles go up to the remote reservoir, I pumped a good quart of 5606 fluid thru the system. I carefull moved the brake slave cylinders on the torque pins to check for binding and non found then I lubed them lightlhy with auto disc brake pin lube, a very thin coat. I might be possible for them to cock and bind maybe under pressure but Ill keep[ messing with it and try to figue it out..

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Posted

Well from an appearance standpoint what you have there should enable you to flip that airplane on its back from whatever ground speed you choose to stand on the brakes at.... You have mentioned brake line rigidity.... I am running a clear line called parker parflex 1/4 inch line on my plane rated for only 450 psi or so working pressure and can get all the pressure I need with it. I have used this brake line on a test stand setup just to see what my brake pedal design would do and it gets to 600 psi. Others are running a 1/8 inch line matco sells as well. doesn't seem to make any difference it all works. 

I've never worked with a kitfox but just eyeballing it I would say static leverage is 3.6 to 1. and the way it is setup there should be minimal degradation with activation. 

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Posted

I finally gave up on my old Matco fat brake cylinders, and rebuilt my system.  I installed the newer, slimmer Matco MC-4 cylinders with an external reservoir, and drilled the brake bellcrank on the pedals much closer to the pedal with a second 3/16" hole about 1" from the brake pedal hinge. as opposed to over 2" in the original config.  This now gives me about 2 to 2.5 times the previous mechanical advantage. It took a while to bleed the brakes, I finally used the classic method with clear tube into a bottle and pressing the pedals hard. Now the brakes are excellent, I can hold the aircraft from rolling at 5800 rpm with a 670 engine!

To clarify - the old cylinders are too fat to fit closer to the pedal, so the best mechanical advantage is only about 1:1, thus the pressure your feet build is limited. The new slim  reservoir cylinder easily sits 1" closer, so with only one hole drilled, I doubled the brake power. I used the Matco reservoir kit, it had all the parts and the compression fittings were easy. The whole refit cost me $270 and 2 hours and now I have excellent brakes.

 

 

Matco MC-5.jpg

Matco MC-4.jpg

matco reservoir.jpg

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Posted

So was it the bottom end of the brake cylinder that you moved closer to the rudder pedal mount tube? (the long cross bar that anchors the lower part of the brake master cylinder???? Thanks, Mark

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Posted (edited)

So was it the bottom end of the brake cylinder that you moved closer to the rudder pedal mount tube? (the long cross bar that anchors the lower part of the brake master cylinder???? Thanks, Mark

At the Top, Mark. Here is a quick drawing, I'll get some photos later. My plane is an Avid, MKIV, so the original  pedals are by design low mechanical advantage. Your Kitfox is already sweet in that department, from your photos.

Note in the photo of my "new" brakes how much closer the pivot point has moved to the pedal, I have about 2.5 times more leverage and therefore more braking power for the same press of my toe brakes.

 

 

 

brake.jpg

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Edited by nlappos

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Posted

I did something similar, but modified the pedals so the arm is at the bottom of the pedal instead of the top.  I used the MC4-G cylinders which are the shortest Matco has, and they fit in the shorter space.  I had tried the 'intensifier' kit on the old MC-5 cylinders, but really didn't notice any improvement.  I attached pictures of both the old and new, hope they make it!

Mark

 

 

brakepedals_small_with_ratio.jpg

brakes_original_with_notes.jpg

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Posted

OK I see the problem... Ill try this fix and see how it works. Thanks guys.!!

Mark

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Posted

Here is what I did to improve mine. In the first picture you see I drilled a hole 1/2inch closer to the pedal that doubled my braking power and the second picture I added 3/8 of an inch to the pedal and made them fit my feet better that also helped a bunch, Hope it helps you out.

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Posted

This a great thread that clearly illustrates what I've tried to explain to folks on the phone many times. Thanks Nick for taking the time to draw this up.

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Posted

Joey - might I suggest an Admin add 'brake' to the thread subject line (i.e. "Need Brake Advice") to facilitate future search and referrals.

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