Braking ideas

[Deskpilot]

It might be old age but I'm going through a brain fade at the moment. I want to use differential brakes operated from a single lever in the control stick. Seems easy but I'm stuck on how to get it to work. I'm thinking of using bicycle parts so it can be either cable operated or hydraulic. I could use my twist the lever version mentioned in another thread but I really prefer to use the rudder pedals for direction control. This will be used on a tricycle u/g with retractable, castoring, nose-wheel (and possibly mains)

 

Any ideas. Sketch's, how ever crude, will be most welcome.

 

 

[turboplanner]

You may not get enough leverage with twist (compare the pressure and distance to a motor bike)

 

You may not get enough braking effort with cycle parts.

 

I think go kart brakes would be light enough and suit typical Ultralight small disc diameters, and use toe braking to get the leverage.

 

Part of the problem I found with Jab brakes, apart from being non-differential was the leverage isn't good enough with your fingers for maximum retardation.

 

 

[Deskpilot]

Let's face it, Jabiru brakes are crap.

 

Can't use conventional toe brakes as both pedals can be pressed simultaneously for air brake. (Don't ask...yet) Mountain bike brakes are pretty powerful so will be OK except perhaps if I'm running straight at an unsuspected fence or other barrier. Certainly strong enough for differential braking/steering.

 

 

[PA.]

Normal motorcycle brakes are large. The brakes fitted to Moto Trials bikes are much smaller and lighter. Check out Moto Merlin brake page.

 

 

[turboplanner]

Remember braking effort varies exponentially with diameter, so it would be worth making up a rough disk to suit the tyre size, and trying the mountain bike brakes on that, although I have seen a Sturmey Archer bike drum brake which stopped a push bike very well.

 

 

[Deskpilot]

Irrespective of what type of brake to use, can anyone answer my question?

 

 

[turboplanner]

What was your question?

 

 

[skeptic36]

Irrespective of what type of brake to use, can anyone answer my question?

No, I don't think it's old age.........

 

 

[SDQDI]

If toe brakes are out of the question is there possibly room for differential heel brakes? Although having said that using your toes for air brakes and heel for ground brakes brings up all sorts of possibilities of mixing them up at inoportune (that has no red line under it but looks to be spelt wrong) times. I still prefer using feet for directional control as the hands are generally busy with one hand on the throttle and one on the stick, although I have seen a few setups with differential hand brake levers mounted on the stick and they seem to work pretty well.

 

 

[pylon500]

If you're using a split/twin rudder airbrake system, you might as well hook the wheel brakes straight to the rudder pedals, no toe brakes hinging required.

 

Ground wheel braking/steering will occur the same as air rudder braking/steering.

 

Then just use a castoring nosewheel/tailwheel.

 

The only downside is the return spring pressure required to keep the rudders straight in flight.

 

To that end, if you pivot the rudder pedals 'above' the floor (say about 2") then the weight of your feet/legs will hold the pedals 'closed' (back) requiring you to push with your toes for activation.

 

And put the return springs at the rudders, not the pedals.

 

 

 

[bushcaddy105]

Use the same principle as the control valve in hydraulic power steering. Mount the lever on a twist grip rotating around the stick and couple this twist grip to the proportioning valve with a torsion spring. (Probably mount the valve at the bottom of the stick to allow easy connection to flexible hoses). This provides self-centering so that no twist gives equal L - R braking but increasing amounts of twist gives increasing bias to either left or right brake. The amount of braking pressure still depends on how much pressure is applied to the lever.

 

I can visualize just how to make this work, but please don't ask me to draw it!

 

My brain is also old, but it must have momentarily connected the dots. Trust the above is food for thought.

 

 

[aj_richo]

Is differential braking with a single lever a conundrum?

 

 

[facthunter]

Relating to the castoring mainwheels , this has been tried before, and appears to be unsuccesful for making the aircraft track where you want it to. Nev

 

 

[bushcaddy105]

a_jricho,

 

No, it's not- I'm not good at explaining the idea! Don't twist the grip at all, the spring which keeps it centred also ensures that the fluid pressure is applied equally L & R. Twist the grip left or right and pressure is only applied to the relevant wheel. How much pressure is still determined by how much force is applied to the lever which is attached to the twist grip, so rotates with it. Only a few degrees of rotation is required, enough to cover one valve port and open another in each direction.

 

 

[Old Koreelah]

My baby has BMX disks and cable-operated callipers off cheap pocket motor bikes.

 

A pair of bicycle levers on the stick allows differential braking by using two fingers for each side- not as hard as it looks.

 

Bicycle hydraulic brakes would give you mobs more feel and braking effect, and weigh bugger all.

 

 

[Soleair]

Any danger of a pic, Mr Koreelah?

 

I'm playing with ideas on braking now. I don't know how tricky it would be to use heel brakes, but that's my preference at the moment.

 

Would love to hear from someone who uses heelbrakes.

 

 

[Old Koreelah]

Sorry Sol; I can't find a pic, and I'm currently working far away from the baby.

 

The major reason for mounting my brake levers on the stick is simplicity and short cable-runs to the wheels.

 

Perhaps the ideal is mounting bicycle hydraulics behind the rudder pedals, so that heavy foot pressure (particularly from your heel) overcomes a strong spring and moves the rudder pedal hinge assembly back against either or both hydraulic actuators. Normal rudder inputs would not affect brakes, but if both your feet were putting sufficient pressure on the pedals, the brakes would be applied. You would have differential braking with "natural" feel.

 

 

[facthunter]

You won't get as much sensitivity with heel brakes. You have to move the whole of your leg to actuate the heels, at the same time you are still trying to steer the plane with the pedals via the rudder and sometimes nosewheel or tailwheel. Toe brakes are pretty much universal for a good reason. Nev

 

 

[Deskpilot]

Thanks for your input guys, lots of info to digest. I was going to post an image of my non proportional system but for some reason "upload a file" isn't working today.

 

 

[Soleair]

Sorry to piggyback your thread, Doug. But it raises some interesting points for me, too.

 

I'm using cable operated drum brakes. I sort of feel the braking action should happen with my feet, but toe brakes would be perhaps a bit overcomplicated. And heel braking seems awkward. Plus it would be easy to overload the light cable limit loads.

 

I can see the advantages of joystick-mounted bake levers. I'm just struggling to visualize how I would operate them both individually to assist in taildragger ground handling, & simultaneously for braking. I would welcome your comments and at some point a pic if poss, Mr Koreelah, sir.

 

Or is it all reasonably easy in practice, operating from the stick?

 

Cheers

 

Bruce

 

 

[Old Koreelah]

...I'm just struggling to visualize how I would operate them both individually to assist in taildragger ground handling, & simultaneously for braking...

Bruce

Landing on tarmac can be an adventure, especially with crosswinds or if I come in a bit quick. The pair of stick-mounted brake levers can be used to keep it straight, but it might be improved upon. Imagine the right hand rested on a sort of T-bar with fingers pulling back on a horizontal brake bar. Pressure could more easily be varied to give differential braking.

 

 

[Soleair]

Hmmm - sounds cunning. Thanks.

 

 

[pylon500]

All the Lightwings use heel brakes, following on from Piper Cubs and Austers before them.

 

Doesn't take too much practice to get a 'feel' for heel brakes.

 

If you look at a Lightwing set-up, you can see that it is possible to vary the leverage/load on the cables depending on the distance from the pivot.

 

 

[Deskpilot]

This is the image I referred to earlier. Twist the lever to select left or right brake. Centralized for equal braking. This is an either or system, not proportional. To change direction, the lever must be released first.

 

 

 

[SDQDI]

When making the hornet we included a hand rudder attachment which incorporates/Replaces the throttle when in use and we did a little brainstorming as to how to make effective differential braking without an overly complex design but didn't come up with a workable design. We did however have some interesting thoughts and even though we discounted them as being unworkable for the hornet ill mention them here.

 

1. An electric toggle switch on the throttle to open/close valves in the brake lines to limit/redirect the pressure.

 

2. Electric brakes.......... They could be controlled altogether by a simple gaming toggle placed on the throttle

 

3. A brake set up on the tail wheel

 

We were trying to solve the problem of being able to operate the plane effectively for my cousin who doesn't have the full use of his legs, which as it's a tail wheel is difficult when it comes to ground handling.

 

I'm not sure if anyone has any knowledge of an ultralight with electric brakes?? I know you would still like to have a redundancy setup but I would think that even with an engine out your battery would still provide sufficient power, unless of course your battery was flat as well.........

 

But other than that it seems that two levers are the easiest way to get progressive differential braking, I can see hassles coming from a setup that requires you to release the brake on one side to use the one on the other but maybe you could slope those bottom pull plates in your drawing so that it did provide progressive braking side to side without release with the only problem being when you wished to brake both wheels you would have to squeeze a bit harder.

 

I tried to draw what I meant by angling those plates not sure how clear it is :-) but setting it up like that would allow you to swap sides without releasing the lever maybe reducing the possibility of operator error.