Independent brakes and where to put them...

[ianahner]

Okay, I will start with a short introduction before jumping into the details. I am getting materials together, and carefully planning an XL build. This build will be a little unique, not in design, but in execution. I am one of three engineering students who will be building the Eagle in a dorm room in pieces, then moving to the local airport hangar for final assembly. 

Before you ask, the answer is yes. Yes it would be easier to do the whole thing in the hangar. Yes there are dozens of other places better suited for building planes. Yes we are all crazy. Near as I can tell though, it has never been done, and when someone told me that it COULDN'T be done, I took it as a challenge. 

Enough with my introduction. On to picking your brains for information. 

I am interested in doing independent brakes in the XL. 

Les Homan pulled it off beautifully, but I do not think my hands are smart enough to deal with two brakes on a stick, and a throttle. I also don't like doing runups with my hand holding the brake. I'd rather move the brakes to my feet. This brings up the question of whether to use toe brakes or heel brakes. 

I did all of my ppl training in a 172 with toe brakes, and I like the toe brakes in the RV4 that I got to fly. 

I also liked the heel brakes in the super cub. I didn't find the transition all that tough, and I don't know that I really have a preference.

This being said, a 172 and a super cub are VERY different planes, and swap the brakes and it might be a bad deal in both situations. The eagle is closer to a super cub than either of the others, so I am inclined to go with a heel braking system, but I would like to know what the rest of you would advise!

Where would you put the brakes? Or am I really barking up the wrong tree and I shouldn't use independent brakes? The eagle will spend a good bit of time on asphalt, so I think independent brakes would be a good thing, especially in a cross wind in the transition to roll out when you occasionally run out of rudder. Or maybe the eagle has so much rudder authority that this isn't a problem? 

What are your opinions?

[Dan_]

 Where would you put the brakes? Or am I really barking up the wrong tree and I shouldn't use independent brakes? The eagle will spend a good bit of time on asphalt, so I think independent brakes would be a good thing, especially in a cross wind in the transition to roll out when you occasionally run out of rudder. Or maybe the eagle has so much rudder authority that this isn't a problem? What are your opinions?

I find toe brakes are easier to use with rudder input.  Especially the kind of rudder input needed when your are fighting off a ground loop.

However some hydraulic brake systems need careful attention to the leverage available to push on the master cylinder. (linkage)  Matco brakes jump readily to mind.  

Toe brakes put way more strain on everything connected to the rudder control system.

All this pulls me toward heel brakes.  Cable heel brakes will be the lightest.

Merely an opinion...

[Steve]

If you go to individual brakes with the Black Max 1000's it will probably require double wheel cylinders on both wheels to have adequate hydraulic advantage for heavy braking...
The single master cyl with hand grip on the stick has a good deal more mechanical advantage...

[stevejahr]

I am positive that opinions here will vary...

If you are used to toe brakes incorporate that style.
If you are used to heal brakes incorporate that style.
Whatever you are most comfortable with run with it, it is your plane.

For me I find some muscles are digital and some are analog.  For brakes you need analog.  How well can you brake a car with your left foot?  My left foot runs a clutch great but brakes not so much.  This should be considered in your design.

Do not over engineer this, an Eagle does not need the same braking system as a 747 (to be extreme about it).

If I were building right now... I would use a mechanical disc brake system from the bicycle world.  I would probably try and use large diameter 200mm rotors to provide some heat/safety margin (this is the place to over engineer honestly).  I would make it toe brakes on the rudder pedals because I have more analog control that way.  And using mechanical means cables that could flex easily with rudder pedal movement.

[Tom H]

DE Stubby has drum brakes, each side connected to its lever located between the seats.  Levers were modified from the plans to allow more leverage.  I am able to hold the airplane still with full throttle, but just barely.

Problem with this arrangement is left hand is on throttle, right hand goes either to stick or brake levers.  Feet are on rudders.  Sometimes it is good to keep the right hand on the stick while applying brakes.

I have thought of changing from levers to heel brakes.  This would be the most straight forward way to make the change.  In my opinion, toe brakes would be more complicated, a bit more weight and, like Dan said, would put more strain on the rudder cable system, especially during full throttle run-ups.

[Sam Buchanan]

I suggest you use the standard, single lever Black Max system, it worked great on my XL. I suspect you will not enjoy flying the XL in wind rowdy enough to require independent braking.  

Best wishes for an enjoyable project!

[Tom XL-7]

The nice thing going with the single hand brake as supplied in the kit is that if you just absolutely feel the need to upgrade to independent you buy another lever cylinder part and crowd your stick. By the way Free Bird (mfg of the black max systems) does make a  dual cylinder unit.  An option not in the poll. You would need a free hand as it is not a stick mount.

http://store.freebirdinnovations.com/product-p/44995.htm

Tom XL-7

[ianahner]

Well as has been pointed out by others, toe brakes put quite a bit of strain on everything. The other thing that I am worried about is that having a braking system on the rudder pedals may mess with the rudder feel. I had an instructor trying to mess with me once who just rested his feet on the pedals while I was flying. He never pushed on anything, but even just resting his feet there it really messed with my perception of the rudder pedals. I can't help but wonder if a bunch of extra nonsense with brakes would do the same thing. 

The dual hand brakes from Free Bird are nice, but I am not sure that I like the idea of not being able to use the throttle and the brakes at the same time. I definitely don't like the idea of not being able to use stick and brakes simultaneously. That being said, the actual unit is great and IF I did heel brakes, I would likely modify that system to fit, as I think it is a great little dual master setup. 

There seems to be a decent number of people who say that I probably just don't really need dual brakes. This makes sense in many ways. With wind going straight through the frame, cross wind loses some of its effect, and an ultralight in cross wind isn't really that much fun anyway. Though I will say, part of my interest in an eagle is that it can handle slightly more wind than the PPG. I love the PPG but the amount I get to actually fly is drastically limited by wind. I have about an hour at dawn and dusk, and that is only on good clear days where there is no morning fog. All in all it is often hard to find a chance to fly. I like the fact that the eagle could fly in a little bit of a breeze, which is very common in the midwest. 

For now, I think I will listen to those of you who say to just build it with a single brake lever. I'll fly for a bit and see if I really want dual. If I decide that I really want dual, I can certainly add them later as several of you have said. If I do decide to add it, I think that I will pursue heel braking or possibly the dual free bird setup. 

Thank you all for the suggestions! I am looking forward to the build. 

Cheers!
-Ian

[CHARLES DEBOER]

Check out this U-Tube video on a Double Eagle break set up. 

 ...

[ianahner]

Check out this U-Tube video on a Double Eagle break set up. ...

I Like this setup quite a bit, though it looks like it would add a bit of weight over the plans version. It is made with lightness in mind, and AL is used, but there is still a good bit of material there. It is a beautiful solution though! I also love how the video showed the multiple iterations and not just the final product. Very cool!

My only issue with that whole design is that it will put a tremendous amount of force on the rudder system in the event of full braking on both sides. Think of the runup scenario. In this case all of the forward pressure on the brakes is being held back by the tail linkage, whether that be cable or push/pull rods. In a runup this would likely only be a minor inconvenince in the case of a failure, because you would presumably rotate on one wheel while you pull power to idle and then pull your plane back to the hangar to change your pants. The bad one would be coming in on a short field, touching down, applying maximum braking, and losing your rudder control. At this point this is a worst nightmare situation. You are landing a taildragger with no rudder... Talk about a change of shorts needed.....

My opinion on the toe brakes is that to do it safely there needs to be some form of mechanical linkage between the pedals, so that if you are pushing on both sides simultaneously you are fighting the pedal assembly and not the tail linkage. Also, this linkage should include sturdy stops so that when you are at the extent of rudder travel and applying brakes you would not be placing undue stress on the tail linkage. Though I admit, if you are hanging out at full rudder and mashing a brake, you are in a nasty spot to begin with... But this is one of the main use cases for the differential brakes on toes: running out of rudder and needing to tap a brake.

[stevejahr]

I have a hard time with the concern about adding more loading to the rudder control system...

Consider that the rudder control system is "connected" to the strongest muscles in the body.  It already has to be designed to handle a LARGE input.

Consider that the rudder control system is quite literally open loop until the pilot is added to the system.  So there is impetus to add load to tighten up the feedback loop.

Consider that almost none of us lift the rudder pedals, instead we just push harder on the other side forcing the rudder control system to push our other leg up.

Consider that braking systems are often operated with only a hand control at a much lower force.  Your hand can only generate so much power after all.

So with a system that must be designed for such a large force to be overwhelmed by the addition such a small force just does not seem reasonable.

[Dan_]

Just operating on grass fields can stress the rudder control system...  

Wittman Tailwinds have an advisory on the rudder pedal assembly, to add a finger strap to the pedal to torque tube weld joint.  (grass fields and toe brakes)  

I would want the finger strap, an extra thick plate where you drill for the cable connection on an Eagle pedal, and beef on the rudder post and horns...

I am fairly certain there was a report that the rudder horns folded on a Legal Eagle.  Fairly certain it did not have brakes.  The pilot pressed both pedals at the same time for some reason I don't recall, I think it was still in the building stage.

The original idea was not to have brakes, not wheel bearings either but I digress...    The point is, less than 254 lbs is the rule.  Deviations from the prototype make it less likely you will hit that target, especially adding something that will cause other things to have to be beefed up...

Leonard says "add only lightness".

Edit:
Wittman Tailwinds touch down at about 70 mph...    

Single place Eagles do not technically have a torque tube for the rudder pedal connection but the whole system would need scrutiny if adding toe brakes.  

The Double Eagle has pilot/pax pedals so has the torque tubes...

My comments are only an opinion...