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Sticky Brakes

Sid Lambert

Well Known Member
My brakes require me to pull the pedal up by hand so they do not drag. This is especially true after I have just landed.

My question is... Is something going wrong with the brake system or do I simply need to put a stronger spring on the master cylinder?
 
Common Issue

Do a quick search and you will find a couple suggested solutions like springs and/or a continous long bolt instead of the short bolts on each side.
 
I had a similar problem. Loosened the bolts that attach the pedals and it went away. Remember to put the cotter pin in!!
 
I have seen people tightened those brake bolts down to 25 inch pounds or so because that's the spec for AN3 bolts. This is obviously an area where the spec is thrown out the window and a little brain power must be applied.

I had the same issue with my brakes slightly dragging (enough to groan a little) so I picked up some springs that I bought at Ace Hardware. The springs are a perfect fit and help bring the brakes pedals all the way back. Sorry, I don't remember the part numbers.

Hope that helps,
 
My only concern is that it is getting worse. I was worried the seals may be deteriorating or something of the likes. It sounds like I just need to disassemble, clean and maybe put fresh/better springs on.

Thanks guys.
 
Sid, two fixes usually found here.

One is long bolt, fixes any misalignment issues on the pedal pivots.

1504871180429cf51dc9a91.mid.jpg


Just remember, in this usage, the bolts are actually pivots/axles, and not clamping devices, use drilled bolts and cotter pins.

The other is booster springs, see this thread go to post 7 for photos and parts list. In fact, read the whole thread for some good info about the long bolts.

I have done both sides on my 10, simple and easy. :)
 
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Skicky Brakes

How many hours do you have on your plane?
Is this something new that is happening?
What brake fluid are you using?
 
put springs on Matco's

After 300 hours my brakes began to drag. The quick effective fix for me was using springs #181(I believe) from ACE hardware on the Matco shafts, but I am still going to replace the pivot points with the long bolt. Does anyone have the AN # required for the bolt?

Don
Phoenix
RV7
 
RE: Sticky brakes (extra springs and stuff)

I used the following from McMaster Carr
(www.mcmaster.
com):

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $1.97 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered,
3"
L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.82 EA.

for a total cost of about $19.62 with shipping in US.
 
Does anyone have the AN # required for the bolt?

Don
Phoenix
RV7

Don,

I used AN3-60A bolts when I did the long-bolt mod on my -6. Actually used the -60A bolts a friend/-7A builder had for his project, and replaced them with like-kind. Just another data point...concur with Steve about measuring.

Cheers,
Bob
 
After carefully measuring, I bought a pair of AN3-56 bolts from Genuine Aircraft Hardware. http://www.gen-aircraft-hardware.com/

They're the perfect length for my RV-7A's brake pedals. Your mileage may vary. What shocked me was the price for a couple of bolts. They're more than $15 each. With shipping, it was over $40!

But I'm glad I did it. I don't want sticky brakes on my airplane.
 
One more plug for Grove

One more plug for Grove master cylinders. (No connection) They have internal springs, and are adjustable in length so you can set the pedals just the way you want them. Very crisp in action, no drag.:cool:

I used the long bolts, as well.
 
Booster springs

A quick thank you to "guccidude1" for listing all the needed parts from McMaster-Carr with part #'s,made it easy for me and the brakes feel much more positive on return of the pedals.

Keith
 
Looking to do the single axle brake pedal mod to my RV-8 brakes to help prevent accidental brake application when landing (I have big feet, size 13 if you must know...) I'm hoping that the axle will provide a surface to concentrate unintended pressure. Anyway, I've noted that some -6 and -7 mods use AN3-56 or AN3-60 bolts as the axle, but the RV-8 pedal width is about 7.5" where the bolts terminate. I was thinking about cutting a 3/16 steel rod to size and threading the ends - has anyone done this? Should I sleeve the rod within the pedal face?
 
I was thinking about cutting a 3/16 steel rod to size and threading the ends - has anyone done this?

I recall someone doing something like this, but cross drilled the rod, used a washer or two and cotter pins.
 
Increased spring force

After a recent post in another thread from someone asking about brake return spring mods, I thought I should finally update this thread with my brake modifications. I assembled my Matco master pistons with the springs recommended in this thread and there was only a barely perceptible increase in return force. I subsequently took some measurements of the spring force in the matco's, ran a few calcs, and came up with an alternative spring solution that will double the current spring force. The original spring upgrade was a maximum of 6lb in compression. This one is 30lb. I've tested them out over the past week during my taxi tests and they feel perfect, with no risk of dragging brake, even if your toes are naturally leaning on the pedals, but not too much force that they become an incomberance when you want the brakes. I also modified the collar sleeve arrangement so that even at full brake compression, there is no way that the spring can rub on the ram. The sliding collar is also a self lubricating polymer, which should help with longevity. Just make sure when you assemble things that the collar is low enough to just clear the top mounting tab, but not so low that you restrict compression of the ram. My aircraft is an RV-7, and I would absolutely recommend the long-bolt (single axis) mod to the brake pedal to eliminate binding, in addition to the spring upgrade. You'll also see in the photos some another mod I did to make some standoffs. These are just aluminum split collars and a piece of tubing cut into thirds, then riveted in place with some long AN470AD4 rivets (the collars are countersunk on the inside and I back riveted it against an appropriate diameter bolt shank). I've also stacked two more short pieces of the cut tubing in between to give myself a little further distance.
Anyway the McMaster Carr parts list is as follows.
Spring 9657K435
Lower nylon sleeve bearing: 6294K441
washers (for seating the lower nylon sleeve bearing) 90295A470
Top nylon sleeve bearing: 6389K625
Set screw shaft collar: 9946K13

For the standoffs:
Two piece collar: 6436K136
Aluminum tubing: 9056K79

Hope this helps.
Tom.

ng3bcl.jpg

fozt77.jpg

2d9zl7p.jpg
 
... I was thinking about cutting a 3/16 steel rod to size and threading the ends - has anyone done this? Should I sleeve the rod within the pedal face?
I recall someone doing something like this, but cross drilled the rod, used a washer or two and cotter pins.

Now I remember why I ordered that piece of 3/16? 4130 steel rod...:eek: I?m planning on the washer and cotter pin route.
 
Is this the setup?

I used the following from McMaster Carr
(www.mcmaster.
com):

(1) Pkg 6389K625
Nylon Bearing Flanged, for 3/8" Shaft Dia, 1/2" Od,
3/8" Length, Packs of 5 $1.97 Pkg

(1) Pkg 9657K115
Steel Compression Spring Zinc-Plated Spring-Tempered,
3"
L, 1/2" Od, .047" Dia, Packs of 12 $5.29 Pkg

(4) Ea. 9946K13
Aluminum Set Screw Shaft Collar 3/8" Bore, 3/4"
Outside Diameter, 3/8" Width $1.82 EA.

for a total cost of about $19.62 with shipping in US.

Friends,

I'm wondering to know if with the hardware mentioned above, this is how the setup will look like:

lDoYA8xh.jpg


Just to confirm to order the correct parts to do it on my plane.

Appreciate if you can chime in. Have all a great week!
 
Friends,
I'm wondering to know if with the hardware mentioned above, this is how the setup will look like:
lDoYA8xh.jpg

Just to confirm to order the correct parts to do it on my plane.
Appreciate if you can chime in. Have all a great week!

I would tie those lines up better at the top. Looks like they could easily be stepped on.
 
That spring is a total waste of time. The force it generates is essentially useless in this situation. I now have 100hrs and about 300 landings on my setup and the spring force of 30lb is right on the money. You are better off using the bill of materials I specify in my post above. If you weren’t on the other side of the world I’d give you some of mine as I have some leftovers. Here’s a link with some pictures.

http://www.vansairforce.com/community/showthread.php?t=173877&page=3

Tom.
RV-7
 
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Thanks Tom!

That spring is a total waste of time. The force it generates is essentially useless in this situation. I now have 100hrs and about 300 landings on my setup and the spring force of 30lb is right on the money. You are better off using the bill of materials I specify in my post above. If you weren?t on the other side of the world I?d give you some of mine as I have some leftovers. Here?s a link with some pictures.

http://www.vansairforce.com/community/showthread.php?t=173877&page=3

Tom.
RV-7

Thanks Tom! Great setup. I've ordered the PN's you described on your post.
Appreciate your knowledge sharing.
Have a great week!
 
stronger brake return springs

Excellent thread. I have experienced brake fade and I have ordered the stronger springs from McMaster Carr.
 
Excellent thread. I have experienced brake fade and I have ordered the stronger springs from McMaster Carr.

Did you do the long bolt option first? YMMV of course, but I found if the pedals are totally free of friction mine returned just fine. I did have to install the little bar extensions for my feet. But with 140 hrs now, I might be able to do without.

If one uses air pressure, you can test the cylinders for return and ensure that the vent to the reservoir is indeed open. Even the hoses have to be arranged to avoid force on that master cylinder.

I did not use the springs as I could not prevent them from touching and rubbing the shaft. Definitely a no-no. I still kept the spring kit JIC. Meaning: the long bolt may not always work, but should be done first.
 
Did you do the long bolt option first? YMMV of course, but I found if the pedals are totally free of friction mine returned just fine. I did have to install the little bar extensions for my feet. But with 140 hrs now, I might be able to do without.

If one uses air pressure, you can test the cylinders for return and ensure that the vent to the reservoir is indeed open. Even the hoses have to be arranged to avoid force on that master cylinder.

I did not use the springs as I could not prevent them from touching and rubbing the shaft. Definitely a no-no. I still kept the spring kit JIC. Meaning: the long bolt may not always work, but should be done first.

There really is no resistance/binding of the return of the pedals. But I would benefit from stronger springs for the return.

With no intent to hijack the thread, my only issue now is a pesky air leak on the left side. I suspect the seals in the left master cylinder as the air bubble (space) grows with more brake action. I am going to swap cylinders to verify the source. The fittings, as best I can tell, are not the culprit.
 
There really is no resistance/binding of the return of the pedals. But I would benefit from stronger springs for the return.

With no intent to hijack the thread, my only issue now is a pesky air leak on the left side. I suspect the seals in the left master cylinder as the air bubble (space) grows with more brake action. I am going to swap cylinders to verify the source. The fittings, as best I can tell, are not the culprit.

If the cleveland design is similar to the matco, I can attest that bad seals can allow air into the supply lines.

Larry
 
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