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Drum Brake re: RF4D printer friendly version
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Collin
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Posted Saturday, October 28, 2006 @ 09:35 AM  

Hello,

The brake on my RF4D N2182 does not work very good. But it is the only RF4 I have flown, How good should the brake work? Should it hold full power on a run up. My brake now will hold about 1500 rpm. The lining thinkness is still good. Maybe they are over heated (glazed)?

I bought a set of brake linings from Wink's Aircraft but have not installed them let. (http://www.wicksaircraft.com/)

I was also told by Eugenio (CFI-I) the brake is on off a small motor scooter.

--------------------
Collin Gyenes



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Posted Saturday, October 28, 2006 @ 12:19 PM  

The brake on N3476 holds the aircraft at more than 1,500 RPM. I have not tried it at full power but it certainly holds at more than 2000 RPM. It doesn't do a whole lot on the runway though. I recently yanked on the handle to try an make a turn off and as usual, it didn't have much effect. To my surprise though, the tail started to lift. That tells me that as poor as the braking is, I probably don't want any more!

Steve

dannparks
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Posted Sunday, October 29, 2006 @ 11:41 AM  

I was thinking about replacing the drum with a disc system. But at this point I think I will stick with the drum. I haven't flown an RF4 yet, but Steve's comments and the flight manual's reference to braking with caution seems to me like it would be easy to accidently lift the tail and take off the prop.

I am thinking about changing from the "umbrella" handle to a motorcycle-type lever on the control stick. Am I correct to assume that the "parking" function of the brake is mostly to allow hand-propping? Is it really necessary on the ground? Does it want to roll on hard ground at idle while doing cockpit ground checks without the brake set? I figured I could always make a bungie chord I could wrap around the stick and brake lever to hold it "on" as sort of a parking brake.

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1



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Posted Sunday, October 29, 2006 @ 05:29 PM  

I like the system on the Yak 52. It has a bicycle lever on the stick as you have described, but it also has a very simple parking brake which is in effect a tab which is inserted in the "V" between the movable and fixed portions of the brake lever near the pivot, locking it in the "on" position. Works very well and is easy to make.

Steve

vpch
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Posted Friday, December 15, 2006 @ 06:49 PM  

Here is the Alfred Scherer answer for his RF4:




Brake handle on the speed brakes...

alfred.scherer@netzwerk-sicherheit.net

I don't have any problem at this time with my classic drum type brakes as I can put full trottle (+/- 3200 RPM) on brakes (OK I have to pull hard...).

[Edit by vpch on Friday, December 15, 2006 @ 06:54 PM]

[Edit by vpch on Friday, December 22, 2006 @ 10:35 AM]

--------------------
Vinc. RF3 #13 F-BLXE

milnerd
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Posted Friday, December 22, 2006 @ 09:36 AM  

I have also been thinking about converting to a squeeze lever type brake on the stick because I want to use the umbrella handle with ratchet for the propeller feathering on the Milan. If you incorporate the Bob Grimstead modified stick that brings the top of the stick back from the wheel housing further there should be plenty of room. The one thing that has to be thought through a bit is how to route the cable so that it can bend as the wheel comes up while keeing the radius of the curve in the cable with in the wheel down position as large as possible so as to get as much force on the wheel end of the cable when you need it.

My thought on the parking brake came out of a discussion with Ed Bjornrud on the subject years ago. How about a loop of velcro in the map pocket that is wrapped around the stick and brake lever when you want a park brake? Simple, light, self adjusting, easily replaced etc.. Once you are in the cockpit it can be stowed for flight because you wont need the park function again during run up etc. because you have the squeeze handle. It is not like there is a bunch of two handed activities required on a Fournier once it is turning and burning.

Dave

dannparks
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Posted Friday, December 22, 2006 @ 06:32 PM  

Hi Dave. Welcome to the forum. I too have been wondering about cable routing with a hand grip on the stick. It seems like it will need to to go through the stick boot, so it can pass next to the fore/aft hinge point, and as close to the side-to-side hinge line as possible. There certainly is not a lot of room in that area. Mine is dissassembled at the moment. It might be interesting for someone to play with some stiff tubing or something to make sure it is going to route OK without pinching the cable when retracted. The velcro strap it a great idea. I had thought of a short bungee, but the velcro can probablly hold more force after you've squeezed the lever.

Dann

--------------------
Dann Parks • RF4D #4051 N2188 • now flying!
Pictures at: https://picasaweb.google.com/111628310900713778468/RF4D_N2188?noredirect=1

Bob Grimstead
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Posted Saturday, December 23, 2006 @ 04:02 AM  

Why fiddle with a brake system that has worked so well for forty years? A disc brake must be heavier, and the one thing a Fournier does not need is more weight, especially for aerobatics.
Yes, you can lift the tail under heavy braking if you heave hard enough on that handle and no, you probably cannot hold the aeroplane stationary against full power. Why would you want to? You can't do a mag check with only one magneto.
As well as when starting, the parking brake facility is useful when turning around on a narrow runway, when the only solution is often to stop, set the park brake, leave the engine ticking over, get out and (very carefully) lift the tail around.
If you need the brake during the rollout, jam the spoilers open with your left elbow or thigh, then grab the brake lever with your left hand.
For the brake to work properly, it is very important to use low friction brake cable and route it carefully as in the original (see photos on the sites and in the old articles). Mine is a length of old Jabiru Teleflex control cable (Teflon coated inner and outer) and works well.

Incidentally, my linings will soon need replacing. I believe the brake shoe was from an old Vespa motor scooter. does anybody know which model, or a part number for the brake lining?

Happy Fournicating, Bob G

Bob Grimstead
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Posted Saturday, December 23, 2006 @ 04:10 AM  

Sorry, I see Eugenio has given the Vespa brake model further down the page.

Thanks Eugenio.

Yours, Bob

joethepro
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Posted Friday, November 2, 2007 @ 10:14 PM  

Can anyone tell me why when i was taxiing in a 15mph direct crosswind from the right, with full left rudder and right wheel down the plane wanted to weather vane to the right until i hit the brake then it would veer slightly to the left and maintain a straight taxi. the brake is on the left side of the wheel but no other explanation for the left turn response seems contributory and that seem a unlikely cause.
vpch
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Posted Saturday, November 3, 2007 @ 03:26 AM  

The only reason I see is:
When the right outriger is down (in the wind), the center of gravity of your plane moves slightly to the right also. When you brake (the wheel is close to the ground and almost on the center line) inertial force tends to turn you to the left ! The same applies when you accelerate because the engine goes futher right of the center of gravity. MAGIC!

--------------------
Vinc. RF3 #13 F-BLXE

Jorgen
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Posted Thursday, November 8, 2007 @ 12:28 PM  

Hi,
I like the drum brake as on the original design which at least on XST gives enough braking power for run up and braking during roll-out after landing. I would hesitate to burden the landing gear with the extra weight of a disc brake.

And Mr Pro(Foley?), I also have problems taxying in cross-wind, but decisevly less so after installing compression-type springs on the tailwheel. As for the question, isn´t it because braking (while in a right turn) puts your leeward (left) outrigger down and that friction slightly brakes your port wing?

Take 5(b) just 4 fun/ Jörgen, SE-UDI, SE-XST

P.S. Love your avatar, Collin. Now THAT is what I without hesitation would call a point roll! And great detective work on airliner.net finding XST, a plane spotter caught me buying some oil at ESMS. Took me 3 phone calls and 2 letters to convince them that XST is a motorglider and as such free of landing fee.

[Edit by Jorgen on Thursday, November 8, 2007 @ 01:31 PM]

andy1
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Posted Friday, November 9, 2007 @ 08:18 AM  

Quote:
Originally posted by Jorgen
Took me 3 phone calls and 2 letters to convince them that XST is a motorglider and as such free of landing fee.

Ha, you neighbors are lucky. You can get cheap AVGAS and no landing fees! Here in Finland we have to pay by weight. That makes a seasonal card quite cheap for an RF4D, but I was thinking about byuing a one month card to visit Helsinki-Malmi a few times with G109. We are even more happy that the fees at that particular airport are times 2,5 versus other Finnish airports. Except for Helsinki-Vantaa, the main airport, that has fees normal*4,5... So, 250 euros for a couple of stops made me use time between TWR closing and opening. Worked fine for the one time occasion, but won't normally be an option.

-A-

PS. I seem to have a new animated avatar as I tried with no success to put one of my own. I believe I have Collin to thank for!

--------------------
***** Antti Laukkanen, Helsinki, Finland - RF4D OH-371 - RF4D OH-370 - RF5 OH-386 *****

Collin
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Posted Friday, November 9, 2007 @ 12:14 PM  

Good Morning,

After installing new shoes and turning the drum I have been happy with the drum brake. (I turned the drum still mounted to the wheel.) When I first pick up N2182 the brake would only hold about 1,200- 1,400 rpm. Now it will hold a lot of power. I have not tried full power yet.

In the early 70's in central California (Merced) a RF4 landed and used the brake to hard and broke the prop. It was towed home by Citabria. I hope to get a copy of that picture some day.

Anyone wanting a avatar or change there currant one or make animated one send the pictures and I will resize and upload.

Take Care

Collin

Bob Grimstead
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Posted Saturday, July 5, 2008 @ 04:40 AM  

Hello again Folks,

For some time I have been pondering the RF4’s brakes.

We have fitted Teflon-lined Teleflex cables (from a crashed Jabiru’s controls) to both of ours, and they work really well, even holding the airplane against full power – and that’s with the 1400cc engine!

But when I flew Sportair and Tiger Club Fourniers years ago, their brakes would barely slow the airplane, let alone hold it stationary at full power – and they were all professionally maintained.

So, when we recently had to take the fuselage off the wing of our red one to fix a different problem, I took the opportunity of having a good look at the brake mechanism.

Looking at the linkage from the side, you can immediately see the problem. The telescoping ratcheted handle under the panel is connected to a rocking lever. The lever’s pivot is offset from the middle, to give you some mechanical advantage. The lower end of this lever then hauls on the brake cable.

Once the brake handle is pulled out from the panel more than four clicks, the lever is becoming in line with the brake handle’s arm. By five clicks they are virtually aligned, and no matter how hard you pull on that handle, all you are doing is trying to stretch a solid mechanism.

Thus, if you are getting five clicks when you pull your brake handle, it’s no wonder the brake isn’t working properly.

So, it is clearly important to take as much of the slack as possible from your brake cable, but without causing the brake linings to drag against the wheel’s rotating drum. Fitting a low-friction cable with a gentle bend will also help. Since our cable outer is very stiff, we later fitted a P-clip on the floor ahead of the left rudder pedal, to hold it precisely in line with the lever’s ferrule.

The best way to adjust your brake is to jack up the airplane and progressively tighten the adjusters (top and/or bottom) until the brake's linings are just rubbing a little on the drum as the wheel turns with the brake released. If there is not enough adjustment left, slacken the adjusters right off and slide the nipple further along the inner cable.

The optimum setting seems to give you three or four clicks on the handle (with a good heave) to set the parking brake. Then it will hold the airplane properly.

If your brake has been out of adjustment for a long time, it is possible that only part of the brake shoe lining was in touch with the drum, so they are no longer exactly parallel. You will have to re-adjust a few times, with a few flying hours between each adjustment, as your linings re-set themselves to the drum.

Good luck, and for all of you I hope this improves your braking.

Yours, Bob

Bob Grimstead
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Posted Sunday, November 2, 2008 @ 09:19 PM  

Hi Guys,

Thank you to whoever suggested Imageshack for posting photos.

Now (if it works) I can show a photo of WGN's brake arm, so you can see why more than four brake handle clicks is giving you no more braking.

Fingers Crossed....

Bob

Bob Grimstead
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Posted Sunday, November 2, 2008 @ 09:24 PM  

Nope,

That didn't work.

How's this?

Bob

[Edit by Bob Grimstead on Monday, August 8, 2011 @ 09:41 AM]

Bob Grimstead
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Posted Sunday, November 2, 2008 @ 09:27 PM  

Well, That address still doesn't get the image to pop up, but if you cut/n/paste the address into your 'address' line above, you can see a photo of our brake lever at five clicks. Pull harder (very much harder!) and all you will get is a longer brake arm. If your brake handle clicks more than four times, you are not getting any more braking, and need to take up some of the slack in your cable.

Yours, Bob

SteveBeaver
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Posted Sunday, November 2, 2008 @ 11:54 PM    YIM

A quick tutorial on posting web links and images:

If you want to post a link to a web site/page/picture be sure that the "Disable CuteCode" checkbox at the bottom of the box you are typing in is NOT checked. If you want your web address to appear as a clickable link, precede it with [url] and end it with [/url].

If you want to display an image, precede the web address of the image with [img] and end it with [/img].

If you click the "Edit" button on your two previous messages, you will see how I have added the required tags.

Steve

Jorgen
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Posted Monday, November 3, 2008 @ 01:46 PM  

Thanks Bob,
for the "three to four clicks"-rule. I do like simple rules like that and what´s more, it appears to be correct. I replaced the modified brake cable stop at the braking arm on the wheel of XST, instead of the original setup (which can be seen on the wheel drawings on this or the german site) I have just a bolt with a drillhole and two nuts to squeeze the cable. Probably just by fluke I seem to have gotten the correct tension on the cable, three clicks and it holds full static (2900 rpm) on grass, at least. From your picture it´s easy to understand why more than four clicks is just trying to pull the pieces of the braking system apart.

Take 5(b) just 4 fun/ Jörgen

[Edit by Jorgen on Monday, November 3, 2008 @ 01:49 PM]

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